Smith - 2003 - Rice origin, history, technology, and production
Smith - 2003 - Rice origin, history, technology, and production
Smith - 2003 - Rice origin, history, technology, and production
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Wiley Series in Crop Science<br />
C. W a yn e Sm ith, Series Editor<br />
Texas A & M University<br />
Cotton: Origin, History, Technology, <strong>and</strong> Production<br />
Edited by C. Wayne <strong>Smith</strong> <strong>and</strong> J. Tom Cothren<br />
Sorghum: Origin, History, Technology <strong>and</strong> Production<br />
Edited by C. Wayne <strong>Smith</strong> <strong>and</strong> Richard A. Frederilcsen<br />
<strong>Rice</strong>: Origin, History Technology, <strong>and</strong> Production<br />
Edited by C. Wayne <strong>Smith</strong> <strong>and</strong> Robert H. Dilday<br />
Forthcoming<br />
Corn: Origin, History, Technology, <strong>and</strong> Production<br />
Edited by C. Wayne <strong>Smith</strong>, Javier Betran, <strong>and</strong> Ed Runge
^ lA<br />
RICE<br />
Origin, History,<br />
Technology, <strong>and</strong><br />
Production<br />
EDITORS<br />
C. Wayne <strong>Smith</strong><br />
T&xus University<br />
Robert H. Dilday<br />
USDA-AMS-NRGEEC<br />
John Wiley 8c Sons, Inc,<br />
( a a o ^
This book is printed on acid-free paper. 0<br />
Copyright © <strong>2003</strong> by John Wiley & Sons, Inc, All rights reserved<br />
Published by John Wiley 8t Sons, Inc., Hoboken, New Jersey<br />
Published simultaneously in Canada<br />
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Library of Congress Cataloging-in-Publication Data:<br />
. . . . . ■■■■<br />
V “ ' ' . . 1 V >-!=■■■''■"'' "'<br />
w - ^<br />
R ice; <strong>origin</strong>, <strong>history</strong>, <strong>technology</strong>, <strong>and</strong> <strong>production</strong> /editors, C. Wayne<br />
<strong>Smith</strong>, Robert H. Dilday.<br />
p. cm. — (Whey series in crop science)<br />
Includes bibliographical references, (p .),<br />
ISBN 0-471-34516-4 (doth : alk. paper)<br />
1. <strong>Rice</strong>. I. <strong>Smith</strong>, C. Wayne. II. Dilday, R. H. (Robert Henry)<br />
III. Series,<br />
SB191.R5 R455 2002<br />
633.T8— dc21 2001057367<br />
Printed in the United States of America.<br />
10 9 8 7 6 5 4 3 2 1<br />
>10.3003 %
Contents<br />
Preface<br />
Contributors<br />
vii<br />
ix<br />
SECTION 1: O RIG IN AND HISTORY 1<br />
Chapter 1.1<br />
Chapter 1.2<br />
Chapter 1.3<br />
Chapter 1.4<br />
Origin, Domestication, <strong>and</strong> Diversification<br />
Te-Tzu Chang<br />
Biosystematics of the Genus Oryza<br />
Duncan A. Vaughan <strong>and</strong> Hlroko Morishima<br />
American <strong>Rice</strong> Industry: Historical Overview<br />
of Production <strong>and</strong> Marketing<br />
Henr/ C. Dethloff<br />
Origin <strong>and</strong> Characteristics of U.S. <strong>Rice</strong> Cultivars<br />
David J. Mackili <strong>and</strong> Kent S. McKenzie<br />
3<br />
27<br />
67<br />
87<br />
SECTION II; THE RICE PLANT 101<br />
Chapter 2.1<br />
Chapter 2.2<br />
Chapter 2.3<br />
Chapter 2.4<br />
Chapter 2.5<br />
Chapter 2.6<br />
<strong>Rice</strong> Morphology <strong>and</strong> Development<br />
Karen A. K. Moldenhauer <strong>and</strong> Julio H. Gibbons<br />
<strong>Rice</strong> Physiology<br />
Paul A. Counce, David R. Gealy, <strong>and</strong> Shi-Jean Susana Sung<br />
Genetics, Cytogenetics, Mutation, <strong>and</strong> Beyond<br />
Georgio C. Eizenga ond J. Neil Rutger<br />
Techniques for Development of New Cultivars<br />
Anna Myers McClung<br />
<strong>Rice</strong> Bio<strong>technology</strong><br />
Thomas H, Tai<br />
Studies on <strong>Rice</strong> Allelochemicals<br />
Agnes M. Rim<strong>and</strong>o <strong>and</strong> Stephen 0, Duke<br />
103<br />
129<br />
153<br />
177<br />
203<br />
221
Contents<br />
SECTION III; PRODUCTION 245<br />
Chapter 3.1<br />
Chapter 3.2<br />
Chapter 3.3<br />
Chapter 3.4<br />
Chapter 3.5<br />
Chapter 3.6<br />
Chapter 3.7<br />
Chapter 3.8<br />
Global <strong>Rice</strong> Production<br />
Bobby Coats<br />
<strong>Rice</strong> Production<br />
Joseph E. Street <strong>and</strong> Patrick K. Boilich<br />
<strong>Rice</strong> Soils: Physical <strong>and</strong> Chemical Characteristics<br />
<strong>and</strong> Behavior<br />
H. Don Scott, David M. Miller, <strong>and</strong> Fabrice G. Renaud<br />
Soil Fertilization <strong>and</strong> Mineral Nutrition<br />
in U.S. Mechanized <strong>Rice</strong> Culture<br />
Richard J. Norman, Charles E. Wilson, Jr., <strong>and</strong> Nathan A. Slaton<br />
<strong>Rice</strong> Diseases<br />
Don Groth <strong>and</strong> Fleet Lee<br />
<strong>Rice</strong> Arthropod Pests <strong>and</strong> Their Management<br />
in the United States<br />
M .0.W ay<br />
<strong>Rice</strong> Weed Control<br />
Andy Kendig, Bill Williams, <strong>and</strong> C. Wayne <strong>Smith</strong><br />
<strong>Rice</strong> Marketing<br />
Gail L. Cramer, Kenneth B. Young, <strong>and</strong> Eric J. Wailes<br />
247<br />
271<br />
297<br />
331<br />
413<br />
437<br />
457<br />
473<br />
SECTION IV: PRODUCTS AND PRODUCT PROCESSING 489<br />
Chapter 4.1<br />
Chapter 4.2<br />
Chapter 4.3<br />
<strong>Rice</strong> Harvesting<br />
Graeme R. Quick<br />
<strong>Rice</strong> Storage<br />
Terry A. Howell, Jr.<br />
Rough <strong>Rice</strong> Drying <strong>and</strong> Milling Quality<br />
Terry J. Siebenmorgan, Wade Yang, Rustico Bautista, <strong>and</strong> Auke Cnossen<br />
491<br />
545<br />
567<br />
SECTION V: GERMPLASM RESOURCES 595<br />
Chapter 5.1<br />
Germ plasm Collection, Preservation, <strong>and</strong> Utilization 597<br />
Harold E. Bockelman, Robert H, Dilday, Wengui Yan, <strong>and</strong> Darrell M, Wesenberg<br />
Index 627
Preface<br />
<strong>Rice</strong>, Oryza sativa^ also called paddy rice, com m on rice, lowl<strong>and</strong> or upl<strong>and</strong> rice, not<br />
including American wild rice. Zizania palustris L., is the m ajor caloric source for a<br />
large portion o f the eartli’s population. This food grain is produced in at least 95<br />
countries around the globe, with China producing 36% o f the world’s <strong>production</strong><br />
in 1999, followed by India at 21% , Indonesia at 8% , <strong>and</strong> Bangladesh <strong>and</strong> Vietnam<br />
each producing about 5%. The United States produced about 1.5% o f the world’s<br />
total annual <strong>production</strong> during tlie last half of the 1990s. However, the United States<br />
accounts for about 15% of the annual world exports o f rice.<br />
Although there probably were experimental plots o f rice in the colonies prior<br />
to 1686, the first recorded effort in rice <strong>production</strong> was by Henry Woodward o f<br />
Charleston, South Carolina, in tliat year. This account o f tlie introduction o f rice<br />
has John Thurber, a captain of an English brigantine, docking at Charleston Harbor<br />
in or before 1686. During this fortuitous occurrence, there being no indication o f<br />
why the ship docked in Charleston, Woodward obtained about a “peck” o f rice seed<br />
that had been placed aboard ship in Madagascar. From this humble beginning, rice<br />
<strong>production</strong> soared to 680 mt in only 23 yearns. The <strong>production</strong> o f rice, <strong>and</strong> later indigo,<br />
made Charleston one of the wealthiest cities in the South during much o f the colonial<br />
period in America.<br />
Carolina W hite cultivar resulted from the 1686 Madagascar introduction <strong>and</strong><br />
Carolina Gold cultivar was selected from Carolina W hite shortly thereafter, or was<br />
a separate introduction at about the same time. There apparently were no additional<br />
introductions or selections grown for almost 200 years, although logic dictates that<br />
producers made additional selections within the <strong>origin</strong>al introduction <strong>and</strong> that additional<br />
introductions made their way into South Carolina <strong>and</strong> Georgia. The next<br />
documented cultivar introduced into the United States was Honduras in 1890. The<br />
U.S. Department o f Agriculture (USDA), through the efforts o f S. A. Knapp, began<br />
systemic introductions o f rice in 1899 with the introduction o f Kiushu from Japan.<br />
The first com mercial seedsman to develop com mercial cultivars o f rice through selection<br />
was S. L. Wright o f Crowley, Louisiana. Crop improvement programs based<br />
on the scientific principles of gene segregation <strong>and</strong> recombination were established<br />
by the USDA in the early 1930s in Ai'kansas, California, Louisiana, <strong>and</strong> Texas. State<br />
agriculture experiment station programs were initiated later in Florida, Mississippi,<br />
<strong>and</strong> Missouri.<br />
<strong>Rice</strong> <strong>production</strong> was limited to the tidewater l<strong>and</strong> regions o f South Carolina <strong>and</strong><br />
Georgia prior to the Civil War because o f the ease of adding water to rice paddies via<br />
a series o f dikes <strong>and</strong> gates utilizing fluctuations in freshwater levels caused by ocean<br />
tides. By 1850, these two states accounted for 90% of the rice produced in the United<br />
VII
VIII<br />
Preface<br />
States. South Carolina <strong>and</strong> Georgia continued to be m ajor producers of rice after the<br />
Civil War. producing about 34 000 mt in 1870, but this was only 34% o f 1850 <strong>production</strong>.<br />
However, the movement o f rice <strong>production</strong> that had begun with the expansion o f<br />
the country prior to 1850 gained m om entum , <strong>and</strong> by 1890, Louisiana was the leading<br />
producer o f rice, <strong>and</strong> <strong>production</strong> in the tidewater regions o f the Atlantic coast had<br />
ceased to exist. Today, <strong>production</strong> is concentrated in Arkansas, California, Louisiana,<br />
Mississippi, Missouri, <strong>and</strong> Texas. California produces predominately medium-grain<br />
rice <strong>and</strong> the remaining states produce predominately long-grain rice.<br />
<strong>Rice</strong> is grown predominately under flooded conditions with water impounded<br />
on the rice field, often called a paddy. Only about 15% o f total world hectarage is<br />
grown as dryl<strong>and</strong>, without water being impounded. In many areas o f the world,<br />
the water that is impounded within the paddies is from rainwater, whereas in the<br />
United States rice is irrigated from wells or surface water such as rivers. Production<br />
in the United States is a highly sophisticated operation, with laser leveling o f fields<br />
<strong>and</strong> huge combines specially designed for rice harvest. Although m uch o f the rice<br />
produced in the world is consumed locally <strong>and</strong> undergoes little processing prior to<br />
consumption, that produced in the United States is perled, or polished, using stateof-the-art<br />
machinery to produce whole or nearly whole kernels with an aesthetically<br />
pleasing, pure white appearance. This product is coated with vitamins <strong>and</strong> iron to<br />
improve human health <strong>and</strong> m aybe treated to make it “quick” cooking, to fit our fastpaced<br />
lifestyles.<br />
There are many other fascinating aspects o f this crop <strong>and</strong> its <strong>production</strong>: such<br />
aspects as its genetic diversity, its <strong>production</strong> o f allelocheniical exudates that control<br />
some aquatic weeds, the aquatic nature o f the plant itself, the methods o f applying <strong>and</strong><br />
removing floods, l<strong>and</strong> preparation, biotic pest control, <strong>and</strong> many others. We believe<br />
that the student o f agriculture wfll find profit <strong>and</strong> pleasure in this monograph on rice<br />
<strong>and</strong> its <strong>origin</strong>, <strong>history</strong>, <strong>technology</strong>, <strong>and</strong> <strong>production</strong>.<br />
C. Wayne <strong>Smith</strong><br />
Robert H, Dilday
Contributors<br />
Rustico B autista<br />
Pood Science Department<br />
University o f Arkansas<br />
2650 North Young Avenue<br />
Fayetteville, AR 74704<br />
H arold E. Bockelm an<br />
USDA-ARS<br />
P.O. Box 307<br />
Aberdeen, ID 83210<br />
University o f Arkansas<br />
2301 South University Avenue<br />
P.O. Box 391<br />
Little Rock, AR 72203<br />
Paul A. Counce<br />
<strong>Rice</strong> Research <strong>and</strong> Extension Center<br />
University o f Arkansas<br />
P.O. Box 351<br />
Stuttgart, AR 72160<br />
P atrick K. B ollich<br />
<strong>Rice</strong> Research Station<br />
Louisiana State University<br />
Agricultural Center<br />
RO. Box 1429<br />
Crowley, LA 70527<br />
Te-TYu Chang<br />
Lane 131, Alley 13, No. 2 , 2/F<br />
Sha Lun Road<br />
Tamshui, Taipei Husien 251<br />
Taiwan<br />
Auke Cnossen<br />
Unilever Research<br />
Olivier van Noortlaan 120<br />
3133AT Vlaardingen<br />
The Netherl<strong>and</strong>s<br />
Bobby Coats<br />
Cooperative Extension Section<br />
Agricultural Econom ics Department<br />
Gail L. Cram er<br />
Agricultural Economics<br />
Louisiana State University<br />
Baton Rouge, LA 70803-3282<br />
H enry C. D eth lo ff<br />
Department o f History<br />
Texas A&M University<br />
College Station, T X 77843-4236<br />
R obert H. Düday<br />
USDA-ARS-DBNRRC<br />
P.O. Box 287<br />
Stuttgart, AR 72160<br />
Stephen O. Duke<br />
USDA-ARS<br />
Natural Products Utilization<br />
Research Unit<br />
University o f Mississippi<br />
P.O. Box 8048<br />
University, MS 38677-8048
Contributors<br />
Georgia C. Eizenga<br />
USDA-ARS-SPA<br />
Dale Bumpers National <strong>Rice</strong><br />
Research Center<br />
2890 Hwy 130 E.<br />
P.O .Box 287<br />
Stuttgart, AR 72160-0287<br />
David R. Gealy<br />
Dale Bumpers National <strong>Rice</strong> Research<br />
Center<br />
USDA-ARS<br />
Stuttgart, AR 72160<br />
Julia H. Gibbons<br />
<strong>Rice</strong> Research <strong>and</strong> Extension Center<br />
University o f Arkansas<br />
PO . Box 351<br />
Stuttgart, AR 72160<br />
Anna Myers M cClung<br />
USDA-ARS<br />
Texas A&M Research <strong>and</strong><br />
Extension Center<br />
Route 7, Box 999<br />
Beaum ont, T X 77713-8530<br />
Kent S. M cKenzie<br />
California Cooperative <strong>Rice</strong> Research<br />
Foundation<br />
PO. Box 306<br />
Biggs, CA 95917-0306<br />
David M. M iller<br />
Department o f Crop, Soil, <strong>and</strong><br />
Environmental Sciences<br />
115 Plant Sciences Building<br />
University o f Arkansas<br />
Fayetteville, AR 72701<br />
D on Groth<br />
<strong>Rice</strong> Research Station<br />
LSU Ag Center<br />
PO. Box 1429<br />
Crowley, LA 70527-1429<br />
K aren A. K. M oldenhauer<br />
<strong>Rice</strong> Research <strong>and</strong> Extension Center<br />
University o f Arkansas<br />
PO . Box 351<br />
Stuttgart, AR 72160<br />
Terry A, Howell, Jr.<br />
Department Food Science<br />
University o f Arkansas<br />
2650 North Young Avenue<br />
Fayetteville, AR 72704<br />
H iroko M orishim a<br />
Saiwai-cho 15-2<br />
Hiratsuka, 254-0804<br />
Kanagawa<br />
Japan<br />
AndyKendig<br />
University o f Missouri<br />
PO . Box 160<br />
Portageville, M O 63873<br />
Fleet Lee<br />
<strong>Rice</strong> Research <strong>and</strong> Extension Center<br />
University o f Arkansas<br />
PO . Box 351<br />
Stuttgart, AR 72160<br />
David J. M ackill<br />
International <strong>Rice</strong> Research Institute<br />
DAPO Box 7777<br />
Metro Manila<br />
The Philippines<br />
Richard J. N orm an<br />
Department o f Crop, Soil, <strong>and</strong><br />
Environmental Sciences<br />
115 Plant Sciences Building<br />
University o f Arkansas<br />
Fayetteville, AR 72701<br />
Graem e R. Q uick<br />
Department of Agricultural <strong>and</strong><br />
Biosystems Engineering<br />
Iowa State University<br />
Ames, lA 50011<br />
Fabrice G. Renaud<br />
Cranfield Centre for EcoCheniistry<br />
Cranfield University
Contributors<br />
Silsoe<br />
Bedford M K45 4D T<br />
Engl<strong>and</strong><br />
Agnes M . Rim <strong>and</strong>o<br />
USDA^ARS<br />
Natural Products Utilization Research<br />
Unit<br />
University o f Mississippi<br />
P.O. Box 8048<br />
University, M S 38677-8048<br />
J. Neil Rutger<br />
USDA-ARS-SPA<br />
Dale Bumpers National <strong>Rice</strong><br />
Research Center<br />
2890 Hwy 130 East<br />
P.O. Box 287<br />
Stuttgart, AR 72160-0287<br />
H. D on Scott<br />
Department o f Crop, Soil, <strong>and</strong><br />
Environmental Sciences<br />
115 Plant Sciences Building<br />
University o f Arkansas<br />
Fayetteville, AR 72701<br />
Terry J. Siebenm orgen<br />
Food Science Department<br />
University o f Arkansas<br />
2650 North Young Avenue<br />
Fayetteville, AR 72704<br />
Shi-Jean Susana Sung<br />
USDA-FS Southern Research Station<br />
Institute o f Tree Root Biology<br />
Athens, GA 30602<br />
Thom as H, Tai<br />
USDA-ARS-SPA<br />
Dale Bumpers National <strong>Rice</strong><br />
Research Center<br />
2890 Highway 130 East<br />
P.O. Box 287<br />
Stuttgart, AR 72160-0287<br />
D uncan A. Vaughan<br />
Crop Evolutionary Dynamics<br />
Laboratory<br />
Division o f Genetic Resources II<br />
National Institute o f Agrobiological<br />
Sciences<br />
Kannondai 2-1-2, Tsukuba,<br />
Ibaraki 305-8602<br />
Japan<br />
E ric J. WaUes<br />
Agriculture Econom ics<br />
University o f Arkansas<br />
Fayetteville, AR 72701<br />
M .O .W ay<br />
Texas Agricultural Experimental Station<br />
Route 7, Box 999<br />
Beaumont, T X 77713-8530<br />
N athan A. Slaton<br />
Department of Crop, Soil, <strong>and</strong><br />
Environmental Services<br />
University o f Arkansas<br />
Stuttgart, A ^ 72106<br />
C. Wayne Sm ith<br />
Texas AScM University<br />
College Station, Texas 77843<br />
D arrell M. W esenberg<br />
USDA-ARS<br />
P.O. Box 307<br />
Aberdeen, ID 83210<br />
Bm W iU iam s<br />
Louisiana State University<br />
Agriculture Center<br />
St. Joseph, LA 71366<br />
Joseph E. Street<br />
Delta Research <strong>and</strong> Extension Center<br />
Mississippi State University<br />
RO. Box 197<br />
Stoneville, M S 38776<br />
Charles E. W ilson, Jr.<br />
Department o f Crop, Soü, <strong>and</strong> Environmental<br />
Services<br />
University o f Arkansas<br />
Stuttgart, AR 72106
XII<br />
Contributors<br />
W engui Yan<br />
USDA-ARS-DBNRRC<br />
P.O. Box 287<br />
Stuttgart, AR 72160<br />
Wade Yang<br />
Food Science Department<br />
University of Arkansas<br />
2650 North Young Avenue<br />
Fayetteville, AR 72704<br />
Kenneth B. Young<br />
Agriculture Economics<br />
University o f Arkansas<br />
Fayetteville, AR 72701
RICE
SE C J IO N<br />
I<br />
Origin <strong>and</strong> History
• í ji-1
C h o p t e r<br />
1.1<br />
Origin, Domestication, <strong>and</strong><br />
Diversification<br />
Te-Tzu Chang<br />
<strong>Rice</strong> Geneticist, Retired<br />
Taipei, Taiwan<br />
IMPORTANCE OF RICE TO HUMANS<br />
GENUS ORYZA<br />
Genomes<br />
Karyotype<br />
Moiecular Characterization<br />
SPECIES OF ORYZA<br />
Updated Biogeography Map<br />
Continental Drift<br />
EVOLUTIONARY PATHWAY OF 0. SATIYACULTIVARS<br />
Proposed Evolutionary Pathway<br />
Perennial versus Annual Ancestor<br />
EVOLUTION OF 0. GLASERRIMA<br />
ANTIQUITY OF THE CULTIGENS<br />
African <strong>Rice</strong><br />
Asian <strong>Rice</strong><br />
DOMESTICATION AND CULTIVATION PROCESSES<br />
DIVERSIFICATION OF RICE CULTIVARS: A CONTINUUM<br />
Genetic <strong>and</strong> Human Forces<br />
Spread of <strong>Rice</strong> Cultivation<br />
Ecogenetic Races<br />
RECENT LOSS IN GENETIC-DIVERSITY<br />
LOOKING AHEAD<br />
REFERENCES<br />
SUGGESTED READINGS<br />
<strong>Rice</strong>: Origin, History, Technology, <strong>and</strong> Production, edited by C. Wayne <strong>Smith</strong><br />
ISBN 0-471-34516-4 © <strong>2003</strong> John Wiley & Sons, Inc.
4 Origin <strong>and</strong> History<br />
IMPORTANCE OF RICE TO HUMANS<br />
GENUS ORYZA<br />
<strong>Rice</strong> is a unique crop o f great antiquity <strong>and</strong> akin to progress in human civilization.<br />
Its rich genetic diversity encompasses an enorm ous range o f geographic-ecologic<br />
adaptation. Its early progenitor, a grass, had differentiated into rather distinct forms<br />
in various humid regions o f the southern l<strong>and</strong>mass now called the Gondwana supercontinent<br />
more than 130 million years ago. The splitting up <strong>and</strong> drifting apart o f<br />
the Gondwana fragments led to their disjunct positions on present-day l<strong>and</strong>masses.<br />
From ancestral forms in West Africa <strong>and</strong> South <strong>and</strong> Southeast Asia, the two cultigens<br />
(cultivated species) evolved separately <strong>and</strong> becam e known as African rice (Oryza<br />
glaberrima Steud.) <strong>and</strong> Asian or com m on rice (O. sativa L.), respectively.<br />
During the last 12,000 years or so, the long process o f cultivation, domestication,<br />
dispersal, <strong>and</strong> diversification is also a facet o f human <strong>history</strong> for the rice-eating peoples<br />
o f Africa <strong>and</strong> Asia. Many fascinating changes in rice cultivation reflect advances<br />
in human manipulation o f the genes in the rice plant <strong>and</strong> the rice ecosystem for<br />
maximum exploitation.<br />
Today, human activities have led to the growing o f rice in m ore than 100 countries<br />
o f the world across a soutli-to-north span from 40°S to 53°N latitude. During 1994,<br />
world rice <strong>production</strong> covered 150 million hectares o f which m ore tlian 130 m illion<br />
hectares are in Asia, 6 million hectares in South America, 1.7 million hectares in North<br />
<strong>and</strong> Central America, <strong>and</strong> slightly over 7 million hectares in Africa. Global rough rice<br />
(paddy) <strong>production</strong> reached 534 million m etric tons in 1994, o f which 482 million<br />
m etric tons were harvested in Asia. The United States produced a record crop o f 8.14<br />
million m etric tons in 1992 <strong>and</strong> maintains its rank as the number 2 rice exporter o f<br />
the world, following Thail<strong>and</strong>.<br />
The continuous growth in world rice <strong>production</strong> has further elevated its em <br />
inence as a staple, with importance equal to that o f wheat. In many areas o f the<br />
developing world, rice is gaining popularity as a preferred source o f caloric supply<br />
(cf. IRRI, 1995; FAO, 1996).<br />
In Asia, rice comm<strong>and</strong>s a top position among food crops (David, 1991). Although<br />
less than 5% o f the world’s rice enters world trade mai'kets, the growing dem<strong>and</strong> for<br />
rice <strong>and</strong> wheat by an increasing populace will necessitate that the two staples support<br />
4 billion people by the year 2020 (Chang <strong>and</strong> Luh, 1991).<br />
For background inform ation on rk e <strong>production</strong> in different countries of some<br />
importance <strong>and</strong> individual <strong>production</strong> statistics, a reading o f the World <strong>Rice</strong> Statistics,<br />
1993-94 (IRRI, 1995) <strong>and</strong> <strong>Rice</strong> Almanac (IRRI-CIAT-W ARDA, 1997) will be helpful.<br />
In addition to the Oryza species, Zizania aquatica L. (now called Z. palustris L.)<br />
was the wild rice of North America. It is now grown commercially in the United States.<br />
On an average basis, rice produces a higher grain yield than wheat or maize <strong>and</strong><br />
can support more people per hectare o f l<strong>and</strong>. Hence, accelerated human population<br />
increase tends to follow intensive rice cultivation (Hanks, 1972; Lu <strong>and</strong> Chang, 1980;<br />
Chang, 1987).<br />
Genomes<br />
Oryza is a modest-sized genus consisting of 20 well-recognized wild species <strong>and</strong> two<br />
advanced cultigens, O. glaberrima <strong>and</strong> O. sativa. These species, tlieir chromosom e<br />
numbers, genome symbols, <strong>and</strong> geographic distribution are summarized in Table 1.1.1.
Origin, Domestication, <strong>and</strong> Diversification<br />
TABLE 1.1.1.<br />
Geographical Distributions<br />
Species of Oryza, Chromosome Numbers, Genome Symbols, <strong>and</strong><br />
Species Name<br />
(Synonym)<br />
2nfor<br />
x = 12<br />
Genome<br />
Group<br />
Distribution<br />
0. aha Swalleii 48 CCDD Central <strong>and</strong> South America<br />
O. australiensis Domin 24 EE Australia<br />
O. barthii A, Chev. 24 A^A*> West Africa<br />
(0. breviliguîata)<br />
O. brachyantha A. Chev. et 24 FF West <strong>and</strong> central Africa<br />
Roehr<br />
0 . eichingeri A. Peter 24,48 CC, BBCC East <strong>and</strong> central Africa<br />
0 . glaberrima Steud. 24 AbAe West Africa<br />
O. glumaepatula teud. 24 AbpAêp South America, West Indies<br />
(O. perennis subsp.<br />
cubensis)<br />
O. gr<strong>and</strong>iglumis (Doell.) 48 CCDD South America<br />
Prod.<br />
O. granulata Nees et Arn. ex. 24 — South <strong>and</strong> Southeast Asia<br />
Hookf.<br />
O. latifolia Desv. 48 CCDD Central <strong>and</strong> South America<br />
0. longiglumis Jansen 48 — Papua New Guinea<br />
O. longistaminata A. Chev. et 24 A'A' Africa<br />
Roehr (0. barthii)<br />
O. meridionalis Ng 24 AA Australia<br />
O. meyeriana (Zoll, et Morrill 24 — Southeast Asia, southern China<br />
ex. Steud.) Baill.<br />
0. minuta J, S. Presl. ex. C. B. 48 BBCC Southeast Asia<br />
Presl.<br />
O. nivara Sharma et Shastry<br />
(0. fatua, O, sativa f.<br />
24 AA South <strong>and</strong> Southeast Asia<br />
southern China<br />
spontanea)<br />
O. oßdnalis Wall. ex. Watt 24 CC South <strong>and</strong> Southeast Asia,<br />
southern China, Papua New<br />
Guinea<br />
O. punctata Kotschy ex. 48, 24 BBCC, BB Africa<br />
Steud.<br />
(?)<br />
0. ridleyi Hook f. 48 — Southeast Asia<br />
0. rufipogon Griff.<br />
(0 . perennis, 0 . fatua,<br />
24 AA South <strong>and</strong> Southeast Asia,<br />
southern China<br />
O. perennis subsp. halunga)<br />
0. sativa L. 24 AA Asia<br />
0. schkchteri Pilger 48 — Papua New Guinea<br />
M ost o f the species are diploid, having 12 pairs o f chromosomes. Seven species<br />
are tetraploid (2n = 4x = 48). Six basic genomes o f 12 chromosomes each have been<br />
identified by the m eiotic pairing behavior in interspecific Fi hybrids examined under<br />
the light mici'oscope. The chromosomes o f rice species are small <strong>and</strong> deficient in m orphologic<br />
markers, rendering them difficult to discern <strong>and</strong> identify. Clear figures o f
Origin <strong>and</strong> History<br />
pachytene chromosomes are also difficult to obtain— a preparation made by Shastry<br />
et al. in 1960 remains the prime model.<br />
Seventeen species in the genus have one or two haploid chromosome complements<br />
(genomes), designated as A, B, C, D, E, <strong>and</strong> P by Japanese, Chinese, <strong>and</strong> U.S.<br />
workers through long years of painstaking investigations, from tlie 1930s through the<br />
early 1960s. At the 1963 <strong>Rice</strong> Genetics <strong>and</strong> Cytogenetics Symposium held at the International<br />
<strong>Rice</strong> Research Institute (IR R l), keyworkers agreed to assign the A genome to<br />
the two cultigens <strong>and</strong> their immediate wild relatives. Thus the cross-fertile taxa in the<br />
O. sativa primary gene pool (species complex) (i.e., O. sativa, O. nivam, O. rufipogon,<br />
<strong>and</strong> their weed races) are assigned the A genome symbol. Related species that have<br />
shown incomplete cross-fertility, detectable aberrations in meiotic pairing, <strong>and</strong> other<br />
aberrations in their crosses with 0 . sativa are assigned to subgenonies o f A, bearing<br />
a lowercase superscript letter corresponding to the species name (IRRI, 1964). For<br />
instance, the genome symbol of O. glaherrima is designated as A®; for O. barthii^ .<br />
The superscripts have undergone revision, following revision in species names (see<br />
Chapter 1.2). Those taxa less compatible witli O. sativa are assigned genome symbols<br />
such as C (for O. ojficinalis), BC (for O. puntata), or E (for O. australiensis). This<br />
scheme corresponds to the primary, secondary, <strong>and</strong> tertiary gene pools o f Harlan <strong>and</strong><br />
de Wet (1971).<br />
Following repeated revisions <strong>and</strong> corrections, the total number o f Orzya species<br />
has been trim m ed from a total o f 28 listed in the 1940s (Chatterjee, 1948; Chang,<br />
1964a, 1975, 1976d, 1985, 1988) to 22 species (Chang, 1985; see dso Chapter 1.2).<br />
The number o f genomes remains at six.<br />
Karyotype<br />
Figures for m itotic <strong>and</strong> m eiotic chromosomes were furnished by Hu (1964), Kurata<br />
(1986), Wu <strong>and</strong> Chung (1986), Kliush <strong>and</strong> Kinoshita (1991) <strong>and</strong> Fukui (1996). D e<br />
spite their shortcomings, the chromosomes are useful in cytogenetic studies. The large<br />
■number o f early papers on genome analysis, meiotic pairing, <strong>and</strong> pollen fertility o f<br />
interspecific hybrids have been summarized by Morinaga (1964) <strong>and</strong> Chang (1964b).<br />
Molecular Characterization<br />
The small size o f the Orzya sativa genome is reflected in its nuclear content o f DNA:<br />
430 Mb, with m ore than 50% repetitive sequences. It is the smallest genome among<br />
aU food crops; com m on wheat has a content o f 13,240 Mb. Recent estimates place<br />
the number o f gene loci in rice at 30,000 (Arumuganathan <strong>and</strong> Earle, 1991). It is<br />
remarkable for a small genome to contain such a vast array o f physiological variations.<br />
The assignment of Orzya taxa to respective genomes now finds confirmation<br />
from biochemical studies on the nuclear DNA of various species. Analyses o f the<br />
repetitive sequences (Zhao et al., 1989) <strong>and</strong> RAPD analysis o f a number o f Oryza<br />
■species (Xie et al., 1998) have shown high degrees o f similarity in species relationships<br />
between cytological <strong>and</strong> molecular approaches. Localization o f specific DNA<br />
repetitive sequences in individual chromosomes <strong>and</strong> localization o f ribosonial DNA<br />
genes on chromosomes have been reported (W u et al., 1991; Chung et al., 1993).
Origin, Domestication, <strong>and</strong> Diversificotion 7<br />
Laboratories in the United States <strong>and</strong> Japan are mapping intensively the m olecular<br />
markers across the A genome. Additional laboratories in other countries have<br />
joined the <strong>Rice</strong> Genom e Project led by the Brookhaven National Laboratory in the<br />
United States (Y. Using, personal com munication, 1999). The mapping <strong>and</strong> tagging<br />
task may someday help in arriving at a fuller underst<strong>and</strong>ing of species relationships<br />
<strong>and</strong> the evolutionary pattern. Recent studies have shown that rice, maize, <strong>and</strong> wheat<br />
have a number o f genes in com mon, indicating a conseiwation o f syntemyjin the grass<br />
family (Kurata et al., 1994; Gale et aL, 1996).<br />
SPECIES OF ORYZi[<br />
Updated Biogeography Map<br />
Long before the param ount importance o f com m on rice to the masses o f Asian people<br />
was recognized by scholars o f the West (see Copel<strong>and</strong>, 1924; Grist, 1975), numerous<br />
accounts <strong>and</strong> tales about rice had appeared in China <strong>and</strong> India. M ost writings or<br />
brief mentions o f rice, especially in classic Chinese literature, were based on historical<br />
records o f various sorts. Others were conjectures or mythology. The focus was naturally<br />
on the culture <strong>and</strong> use of Asian rices. Less was Imown about its wild-growing,<br />
relatives or the phylogeny between cultivated <strong>and</strong> wild rices that were found at the<br />
same or neighboring sites. It should be pointed out that artificial hybridization <strong>and</strong><br />
its genetic consequences became recognized <strong>and</strong> pursued only after the rediscovery<br />
in the twentieth century o f Mendel’s laws o f 1865. Asian writers’ knowledge o f wild<br />
Oryza species grew in the late nineteenth century after botanists reported new finds<br />
of Oryza species.<br />
Meanwhile, the wide <strong>and</strong> disjunct distribution o f the species described, spanning<br />
from West Africa across tropical Asia <strong>and</strong> Oceania to South America, has baffled<br />
many scholars about the significance of such a distribution. Only the Russian botanist<br />
Roschevicz (1931), following a systematic study o f 19 species, made a sweeping statement<br />
that species in the section Sativa Roschev. had a com m on <strong>origin</strong> in Africa. The<br />
taxa in this section were australiensisy hrachyantha, glaherrima, gr<strong>and</strong>iglumis, latifolia,<br />
officinaUs, <strong>and</strong> sativa, which covered aU Icnown genomes o f A, B, C, D, E, <strong>and</strong> F. The<br />
other three sections o f Roschevicz consisted o f minor species o f unknown genomic<br />
composition, <strong>and</strong> several taxa were later banished from the genus Oryza. Roschevicz’s<br />
postulate did not receive support from rice workers.<br />
The geographic <strong>origin</strong> <strong>and</strong> later dismemberment o f the genus remained a puzzle<br />
until the early 1970s, when Chang happened to see a new <strong>and</strong> crude map o f the<br />
Gondwana supercontinent (Hallam, 1973), which struck Chang as the solution to the<br />
puzzle. W hen the loiown genomes of m ajor species were placed on the map o f Gondwana<br />
before its brealcup <strong>and</strong> drifting apart, a perfect fit was obtained (Chang, 1976e).<br />
The Gondwanaic <strong>origin</strong> o f the Oryza species was then postulated (Chang, 1976a) as<br />
shown in Figure 1.1.1. An associated postulate on tlie pai'allel evolutionary pathway of<br />
the two cultigens was presented in conferences <strong>and</strong> papers o f 1975 <strong>and</strong> received wide<br />
acceptance (Chang, 1976b,c). A full account was summarized by Chang in 1985. It<br />
represented the best integration o f findings from plate tectonics, biosystematics, <strong>and</strong><br />
crop geography among plants o f econom ic importance.
Origin <strong>and</strong> History<br />
Figure 1,1.1. Reconstruction of the Gondwana components, showing the genomes of wild species found in<br />
various areas. (Adapted from Chang, 1985.)<br />
Continental Drift<br />
In the new scheme of plate tectonics, the Gondwana supercontinent began to break up<br />
in the early Cretaceous period around 130 million years ago. South America was the<br />
first to bréale away from Africa <strong>and</strong> begin its drift. Australia <strong>and</strong> Antarctica followed<br />
20 million years later. The huge plate o f Soutli <strong>and</strong> Southeast Asia was the last to bréale<br />
away, <strong>and</strong> it collided with the Asian mainl<strong>and</strong> about 45 million years BP. This collision<br />
<strong>and</strong> continuing northward push of the South Asia plate led to the rise o f the Himalaya<br />
<strong>and</strong> associated mountains in Burm a <strong>and</strong> Malaysia. Madagascar, the m ajor isl<strong>and</strong>s o f<br />
Indonesia, <strong>and</strong> Papua New Guinea also were fragments o f Gondwana. Further details<br />
o f direct <strong>and</strong> related evidence along with sources o f inform ation may be found in<br />
Chang (1983, 1985).<br />
The summary given above is a fantastic account o f those huge l<strong>and</strong>masses ferrying<br />
the early forms o f Oryza plants to far corners o f the southern hemisphere. It<br />
reconciled many divergent postulates <strong>and</strong> conjectures about various members o f the<br />
genus. It also led to a unified postulate that explains the southern <strong>origin</strong> o f Oryza<br />
plants in the north, their phylogenetic relationships, <strong>and</strong> ecogenetic differentiation at<br />
new sites such as China. More crucially, however, the unified postulate lent credence<br />
to the parallel evolutionary pathway o f the two widely located cultigens, <strong>and</strong> their<br />
subsequent differentiation <strong>and</strong> diversification in diverse agroecosystems by peoples<br />
differing in cultural <strong>and</strong> technological development.
Origin, Domestication, <strong>and</strong> Diversîficatîon<br />
EVOLUTIONARY PATHWAY OF 0. SATIVA CULTIVARS<br />
Proposed Evolutionary Pathway<br />
The unified postulate on the Gondwanaic <strong>origin</strong> o f the genus <strong>and</strong> the parallel evolution<br />
o f the two cultigens amplified <strong>and</strong> strengthened an analytical approach to<br />
the im portant question: How did O. sativa cultivars evolve? Controversies lingering<br />
from the days o f Watt (1891) <strong>and</strong> de C<strong>and</strong>olle (1886) in the late nineteenth century<br />
were concerned largely with the choice between a perennial parent such as O. rufipogon<br />
<strong>and</strong> an annual form, then called O. sativa f. fatua or f. spontanea (cf. Chang,<br />
1964b). O n top o f the confusion, the ambiguous taxon “O. perennis M oench” o f<br />
diverse geographic <strong>origin</strong>s <strong>and</strong> uncertain description was used repeatedly by Oka <strong>and</strong><br />
co-workers, <strong>and</strong> others as the ancestral species. “O. perennis M oench” was named<br />
early in 1794 <strong>and</strong> used by Chatterjee (1948), Sampath (1962), <strong>and</strong> others in varying<br />
instances. Following Tateoka’s visit to several botanical museums in Europe <strong>and</strong> the<br />
United States, the specimen was found missing, <strong>and</strong> various descriptions by later<br />
workers differed widely (Tateoka, 1963,1964). Thus “O. perennis” lacks the requisites<br />
o f a valid botanical species (see Chapter 1.2). Moreover, the distinction between a<br />
perennial or annual growth habit is not so pronounced in diverse environments o f<br />
the tropics as to be a valid classification criterion (Tateoka, 1964; Chang, 1976d).<br />
Tateolca (1964) suggested the use o f O. rufipogon Griff, to designate Asiatic, African,<br />
<strong>and</strong> American forms in his “ O. sativa complex.”<br />
Then Sharma <strong>and</strong> Shastry (1965) described <strong>and</strong> proposed the name O. nivara<br />
Sharma et Shastry for the Asian annual wild form o f the O. sativa complex in northern<br />
India. A m ore restricted description was given o f O. rufipogon. This development<br />
facilitated a delineation between the more primitive perennial forms <strong>and</strong> the annual,<br />
more advanced wild rices, although samples o f O. nivara provided to me by Sharma<br />
did not agree with his description in many respects (my personal observation). Yet<br />
m ost samples taken from the field were judged as weed races (according to Harlan<br />
<strong>and</strong> de Wet, 1971) which came from natural hybridization between two wild species<br />
or among three species: rufipogon^ nivara, <strong>and</strong> sativa <strong>and</strong> their hybrid progenies. Thus<br />
elegant statistical treatm ent of r<strong>and</strong>om samples talcen from the field without prior<br />
knowledge of their phylogenetic <strong>origin</strong> <strong>and</strong> site <strong>history</strong> may not reveal or lead to a<br />
true picture o f the complex events of past centuries. The evolutionary pathway o f<br />
O. sativa <strong>and</strong> wild relatives is shown in Figure 1.1.2.<br />
Perennial versus Annual Ancestor<br />
The line o f descent in O. sativa is probably from a wild perennial to a wild annual <strong>and</strong><br />
onto an annual cultigen. Also involved ai*e weedy forms, which could have played a<br />
role in the long process o f evolution (Chang, 1976a,b). Chang also emphasized that<br />
the status o f the putative progenitors should be regarded as conceptual species o f the<br />
past as true-to-type specimens likely are not to be found in the disturbed habitats<br />
o f today. This scheme, based on past findings of many workers <strong>and</strong> observations<br />
o f the author, has been accepted generally by rice workers <strong>and</strong> otlrers. The choice<br />
o f an annual wild form, propagated mainly by seed, as the immediate progenitor
"l!<br />
10 Origin <strong>and</strong> History<br />
GONDWANALAND<br />
Figure 1.1.2. Evolutionary pathway of the two cultigens. Arrow with solid line indicates direct descent. Arrow with<br />
broken line indicates indirect descent. Double lines indicate introgressive hybridization. (Adapted from Chang, 1985.)<br />
I: '<br />
began with the observations o f Watt (1891); with corollary evidence from barley<br />
<strong>and</strong> wheat (Harlan et al., 1973). Nevertheless, Oka (1988) continued to argue for<br />
an “intermediate perennial-annual type” as the immediate progenitor <strong>and</strong> adopted<br />
O. rujipogon, the Asian form o f “ O. perennis” in the next rank o f ancestry. Citing the<br />
papers o f Sano et al. (1988) <strong>and</strong> M orishim a (1986), Oka based his choice on wild<br />
rice samples collected in Thail<strong>and</strong>, which generally is not considered the early site o f<br />
domestication for rice (see also Evans, 1989).<br />
It is apparent from the condensed review above that the question about the<br />
immediate progenitor o f O. sativa has not been settled. As in many other crops,<br />
debates are certain to continue in the future. It is hoped that more illuminating<br />
evidence will come with the aid o f molecular techniques. But the question remains:<br />
Wliere can we now find representative specimens o f plants <strong>and</strong> seeds with related<br />
phylogenetic <strong>and</strong> site information?<br />
When one visits the remaining natural habitats o f the “0 . sativa complex,” especially<br />
when adjacent to a cultivated field, the observer usually is bewildered by the<br />
wide array of plants that differ in some plant <strong>and</strong>/or floral features. Except at spots<br />
where a single plant st<strong>and</strong>s, it would be difficult to find a representative specimen.<br />
Thus Oka <strong>and</strong> co-workers were dealing lai'gely with hybrid swarms or heterogeneous<br />
populations rather than discrete colonies.<br />
Those morphoagronom ic changes that accompany the evolutionary process<br />
from wild to cultivated will support the south-to»north route from perennial to<br />
annual as indicated by the dispersal route in Figure 1.1.3. A broad-based discussion<br />
o f individual traits is given in the section “Dom estication <strong>and</strong> Cultivation Processes.”
Origin, Domestication, ond Diversification<br />
n<br />
Centres of diversity of cultivars S<br />
“ “ “* Sínicas of Japónicas<br />
Indicas<br />
■' Javanicas<br />
------ Distribution of wild relatives<br />
Figure 1.1.3, Extent of wild relatives ond spread of ecogenetic races of 0. sativa in Asia <strong>and</strong> Oceania. (Adapted<br />
from Cliong, 1985.)<br />
EVOLUTION OF 0. GLABBRRIMA<br />
M ost rice workers find little dissension with the postulate that the African cultigen<br />
O. glaberrima came from the wild annual O. barhtii A. Chev., which, in turn, was<br />
likely to have been derived from the rhizomatous <strong>and</strong> self-incompatible wild perennial<br />
O, longistaminata Chev. et Roehr. O, harthii was formerly called O. hreviligulata<br />
A. Chev. et Roehr, <strong>and</strong> the perennial longistaminata as O. barthii sensu Hutch, et<br />
Dalz. Weedy intermediates have been grouped tentatively under O. stapfii Roschev.<br />
The three species have become sufficiently differentiated from each other to warrant<br />
their assignment to different subgenomes o f A, A®, A'’, <strong>and</strong> A^ respectively (see<br />
Chang, 1964b).<br />
Studies by Porteres (1956) have indicated that the primary area o f diversity for<br />
O, glaberrima is in the swampy basin o f the upper Niger River <strong>and</strong> two secondary<br />
centers located to die northwest, near tlie Guinean coast<br />
Various studies have shown that cultivars o f O, glaberrima are less diverse than<br />
those in O. sativUi but they also contain both deepwater <strong>and</strong> dryl<strong>and</strong> strains. Details<br />
appear in Oka <strong>and</strong> Chang (1964), Bardenas <strong>and</strong> Chang (1966), Oka <strong>and</strong> M orishima<br />
(1967), Chang et al., (1977), Harlan (1975, 1977,1989) <strong>and</strong> Ng et al., (1991).
12 Origin <strong>and</strong> History<br />
ANTIQUITY OF THE CULTI6ENS<br />
African <strong>Rice</strong><br />
I . ii:<br />
O, glaherrima generally is believed to have been grown in the primary area o f diversity<br />
in West Africa since 1500 b .c., while the secondary areas began 500 to 700 years later<br />
(Porteres, 1956), although no archaeological evidence has been provided. In recent<br />
years, 0 . glaherrima has been reduced in many cases to the status o f a weed (i.e,,<br />
volunteer plants from dropped seeds) in fields planted to O. sativa (Harlan, 1989;<br />
the audior’s observation).<br />
Asian <strong>Rice</strong><br />
I' ii<br />
Reports on tlie findings of early rices growing in Asia are numerous <strong>and</strong> varied in<br />
authenticity. The largest num ber o f accounts or claims based on historical records<br />
or mythological writings came firom two countries vying for the top spot: India <strong>and</strong><br />
China. Early debates in European circles led de C<strong>and</strong>olle (1886) to remark that rice<br />
is more likely to have <strong>origin</strong>ated in India, whereas rice cultivation may be earlier in<br />
China.<br />
The param ount importance o f rice as a staple to the populations in Asia has<br />
aroused widespread interest in the <strong>origin</strong> <strong>and</strong> antiquity o f rice cultivation among<br />
Asian writers as well as countless scholars in both the East <strong>and</strong> West for several<br />
centuries.<br />
In India, references to rice appear in ancient Hindu scripts (estimated to be 1500<br />
to 1000 B,c.). Up to the 1950s, the oldest excavation o f rice grains was found at<br />
Hasthinapur (U.P.) dated between 1000 <strong>and</strong> 750 b .c. (Chose et al., 1960). The often-<br />
cited Chalcolithic sample o f rice dated to 4530 b .c. A 1980 report on excavations made<br />
in Koldihwa at Mahagasra (U.P.) pushed the date back to 6570-4530 b .c. The rice<br />
grains appeared to be o f a cultivated type (see Chang, 1989).<br />
In China, the popular claim in the past was that rice was among the five cereals<br />
that the mythological Emperor Sheng-Nung (2737-2697 B x .) taught the people to<br />
cultivate. Many scholars in tlie West have questioned tlie validity o f the mythology<br />
<strong>and</strong> raised the question of whether wild rice was found in ancient times (see Chang,<br />
1983). The finding of the character "tan” (= rice) carved on the bone oracles o f<br />
tire Ying Dynasty (1766-1922 b .c.) provided a more reliable time period tlian that<br />
o f earlier accounts. Archaeological evidence came from the imprint of a rice glume<br />
on clay pottery unearthed from Yang-shao site (Honan Province) <strong>and</strong> its estimated<br />
age was 3200-2500 b .c. (cf. Chang, 1979). Soon after, an excavation at H o-M o-Tu<br />
(Hemudu) in Chekinag Province revealed a large, well-preserved collection o f carbonized<br />
grains, straw, earthen cooking utensils, spades made from bones o f large<br />
animals, <strong>and</strong> advanced wooden huts— all these point to a com munity structure o f<br />
early rice growers. Repeated carbon-14 dating showed a date 8000 years ago (see<br />
Chang, 1983). Soon, excavations o f a similar age, according to radiocarbon dating,<br />
were found in Chekiang <strong>and</strong> Hunan Provinces along the middle <strong>and</strong> lower reaches of<br />
the Yang-Tze River (An, 1989; Chang, 1989). Together with the finding o f four wild<br />
species in south <strong>and</strong> southwest China, reaffirmed in the 1970s, the antiquity of rice<br />
cultivation in China has been recently reestablished by scientific evidence. Even the<br />
<strong>origin</strong>s o f Chinese civilization need revision (Chang, 1983).
Origin, Domestication, <strong>and</strong> Diversification 13<br />
Recent articles have reported the finding of ancient rice remains o f about 10,000<br />
to 11,500 years in age from sites nortli o f the previously reported sites. It is rather<br />
puzzling that older sites, such as those in Peng-Tou Shan in Hunan <strong>and</strong> at the Cliahu<br />
site in Honan (Hunan Provincial Archaeological Research Institute, 1990; Chen,<br />
1995), have predated those found in Yunnan. Since Yunnan hosts the routes from<br />
South <strong>and</strong> Southeast Asia to China <strong>and</strong> is along the border where the Gondwanaic<br />
South-Asia plate collided <strong>and</strong> thrust into the Asia mainl<strong>and</strong>, it was thought tliat the<br />
southern areas could be earlier sites o f the dispersal o f rice into China (see discussion<br />
by Chang, 1983). Further studies will shed more light on this point.<br />
The southern <strong>origin</strong> o f the early rices has dispelled the former claim o f some<br />
Chinese authors that “rice <strong>origin</strong>ated in China” (see Chang, 1964b). Now, the Chinese<br />
workers have agreed that China was one o f the centers (Wang, 1993). A list o f the<br />
chronology <strong>and</strong> sites where early remains o f rice were discovered in Asia has been<br />
provided by Chang (1989). Again, readers should note that tlie validity o f some o f the<br />
reports needs to be confirmed by more rigorous tests.<br />
DOMESTICATION AND CULTIVATION PROCESSES<br />
As in other plant species that became crops, the sequence in domesticating a food crop<br />
such as rice by prehistoric people is: gathering cultivation domestication. Prior<br />
to gathering, the prehistoric people also hunted, fished, <strong>and</strong> gathered other readily<br />
available edible plant parts as food. Initially, rice might have been a food supplement<br />
to other more easily collected plants or plant parts, but as people developed a liking<br />
for the tasty <strong>and</strong> easily cooked cereal, they selected the heavier-bearing panicles as<br />
wen as heavier grains. They also brought rice plants closer to homesteads. In tropical<br />
areas, a crop o f free-shedding plants is generated from dropped seeds or ratoons. The<br />
harvest season may last for months. However, in cooler regions, where the harvest<br />
period is shorter <strong>and</strong> m ore synchronized, selecting plants for the next crop became<br />
more imperative.<br />
In cooler areas, the harvested grains also need to be transported to homes <strong>and</strong><br />
stored for a considerable period in order to sustain the food supply for the intervening<br />
months between harvests <strong>and</strong> to provide seed for the next crop. In such a situation,<br />
the crop depends on human care for perpetuation, <strong>and</strong> the true domestication phase<br />
begins under more deliberate human manipulation.<br />
The cultivation o f rice began when humans, probably women, broadcast grains<br />
into low-lying swampy spots near homesteads, where weeds <strong>and</strong> free-running animals<br />
were kept out <strong>and</strong> the water supply <strong>and</strong> drainage could be manipulated. L<strong>and</strong> near a<br />
homestead often benefits in soil productivity from human wastes <strong>and</strong> animal excreta,<br />
which can nourish the rice plants. Plants are increasingly subject to natural selection<br />
forces or human preference, or both. Selection can be both active (i.e., directed) or<br />
negative, through discarding. Later, religious <strong>and</strong> social forces would play a part in the<br />
human selection phase. In general, the com m on trend in selection following domestication<br />
is for plants to be developed so as to conform further to human desires relative<br />
to growth habit, plant height, tillering, growth duration, photoperiod or temperature<br />
sensitivity, tolerance to drought or flooding, plant form , <strong>and</strong> grain morphology, size,<br />
<strong>and</strong> milling <strong>and</strong> cooking characteristics. AU these traits can be controlled more effectively<br />
by the cultivator than in wild-growing populations (Chang, 1976a,b). The
14 Origin ond History<br />
; r<br />
i r<br />
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natural outcrossing incidence decreased from 30% in wild forms to about 1% in<br />
cultivers. Other factors involved in the dynamics o f domestication were discussed by<br />
Harlan (1975) <strong>and</strong> Oka (1988).<br />
Various adaptive components have contributed to differences among wild, weedy,<br />
<strong>and</strong> cultivated forms. Other features that were readily recognized by the cultivators<br />
<strong>and</strong> became markers for panicle vselection range from awn length, degree o f grain<br />
shedding or ease in threshing, length o f grain dormancy, smoothness o f the glume<br />
surface, pericarp color, endosperm features, <strong>and</strong> probably others. During the domestication<br />
process, those traits governed largely by dominant alleles would give way<br />
to recessive alleles (Chang, 1976b; Chang <strong>and</strong> Li, 1991). Whereas the wild forms<br />
differ more in genetic diversity between populations, the divergence in alleles became<br />
smaller as domestication <strong>and</strong> cultivation proceeded (Oka, 1988).<br />
DIVERSIFICATION OF RICE CULTIVARS: A CONTINUUM<br />
Genetic <strong>and</strong> Human Forces<br />
The cultivated rices, especially the Asian cultivars north o f the equator, are truly<br />
remarkable in the diversity of their morphological characteristics <strong>and</strong> in their physiological<br />
mechanisms related to ecological adaptation or specialization. The enorm ous<br />
<strong>and</strong> broad range o f diversification led to the present cosmopolitan cultivation over<br />
such an enormous <strong>and</strong> extreme range o f agroecosystems, not seen in other crops: deep<br />
water up to 5 m vs. dryl<strong>and</strong> habitat; 90-day maturity in the aus crops to 330-day cycle<br />
in the rayada group; elevations from sea level to nearly 2000 m; a wide range in plant<br />
tolerance to soil factors; from tropical types grown in desertlike climate to cultivars<br />
in northern California that can emerge under soil clods in icy water; <strong>and</strong> varying reactions<br />
to a large num ber o f insects <strong>and</strong> disease organisms. The com mercial planting<br />
o f m ajor cultivars across five agroecosystems following centuries o f cultivation under<br />
such ecosystems <strong>and</strong> related cultural practices are summarized in Table 1.1.2.<br />
What are the genetic mechanisms that enabled the rices to attain their remarkable<br />
diversification? Spontaneous gene mutations undoubtedly fueled the beginning o f diversification.<br />
Soon after, hybridization-differentiation cycles in the field, proposed by<br />
Harlan in 1964 (see Harlan, 1975), formed the moving force. However, the selection<br />
processes, whether natural or human, or more likely a com bination, were crucial in<br />
leading to stable variants (Chang, 1976b). The great power <strong>and</strong> efficacy o f human<br />
selection has been well shown by the progress made in plant <strong>and</strong> animal breeding<br />
all over the globe. W omen have played a greater role than m en in plant selection <strong>and</strong><br />
subsequent plant modification. On the other h<strong>and</strong>, men are probably more concerned<br />
with the improvement o f farm tools.<br />
Spread of <strong>Rice</strong> Cultivation<br />
Methods for planting rice progressed from broadcasting to dibbling, drilling, <strong>and</strong><br />
transplanting. Aerial broadcasting o f presoaked <strong>and</strong> germinated seed into flooded<br />
fields is gaining in acceptance in temperate regions such as the southern United States<br />
<strong>and</strong> Australia. Broadcasting dry seed into dry soil is practiced in both dryl<strong>and</strong> rice
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16 Origin ond History<br />
fields <strong>and</strong> deepwater rice areas in the tropics. Drilling o f seed in rows was once the<br />
principal method o f seeding in the southern United States. Drilling with sprouted seed<br />
is now used to some extent in Japan. The labor-consuming process o f transplanting<br />
seedlings in puddled soils began in China in about a .d. 200. It has the advantages<br />
o f facilitating intensive management of the seedlings grown in nurseries, thorough<br />
soil preparation, control of weeds, promoting uniform ripening of plants in the field,<br />
<strong>and</strong> aiding multiple cropping of rice with a short-duration crop in the same paddy<br />
field. Transplanting generally led to the highest grain yield (Nishiyama, 1949; Hanks,<br />
1972; Chang, 1976a), but its labor-intensive nature required organized com munity<br />
effort. The techniques <strong>and</strong> associated farming practices spread from China to countries<br />
in East <strong>and</strong> Southeast Asia (Chang, 1979). Interesting illustrations o f farming<br />
practices <strong>and</strong> tlie associated implements have been provided by Amano (1962) <strong>and</strong><br />
Chao (1979).<br />
The time frame o f the <strong>origin</strong> o f rice cultivation in different countries is im <br />
possible to pinpoint. It is likely, however, that the early forms that became adapted<br />
to human care in seeding arose largely on the northern edge o f distribution of annually<br />
based progenitors during the New Therm al Period o f 10,000 to 15,000 years<br />
ago, when frequent drought favored the earlier-maturing forms (Whyte, 1972). Such<br />
clusters of early rice cultivation began in a wide belt covering the southern slopes<br />
of the Himalaya mountain range <strong>and</strong> the hills o f Thail<strong>and</strong>, Burma, southern China,<br />
<strong>and</strong> Vietnam (Figure 1.1.3). From this belt, the early form s o f rice spread to east-<br />
central China <strong>and</strong> various isl<strong>and</strong>s in Southeast Asia (Chang, 1976a-c). This postulate<br />
is based on the studies of many workers (Hamada, 1956; Kihara <strong>and</strong> Katayama,<br />
1964; Watabe et al., 1970; Hakim <strong>and</strong> Sharma, 1974; Watanabe <strong>and</strong> Toshimitsu, 1974;<br />
Nakagahra et al., 1975) <strong>and</strong> is now generally accepted as plausible (Sm artt <strong>and</strong> Simmonds,<br />
1995).<br />
W hat types o f changes did the rice plant undergo following cultivation <strong>and</strong> domestication?<br />
Following domestication, cultivation, <strong>and</strong> selection, the rice plants became<br />
a little shorter. Following intense human cultivation, the plants produced more<br />
panicle-bearing tillers, longer <strong>and</strong> more branched panicles, <strong>and</strong> heavier grains. Plants<br />
that showed differences in adaptation to varying water depths would show up in<br />
exp<strong>and</strong>ed cultivation sites <strong>and</strong> become selected for the ensuing year. In continually<br />
flooded sites, plants with superior ratooning ability on the higher nodes would be<br />
recognized <strong>and</strong> saved (Chang, 1976a). In dryl<strong>and</strong> plantings, plants having tliicker <strong>and</strong><br />
deeper roots would be favored (Chang et al., 1991).<br />
In the process o f domestication, dispersal was a prerequisite. Widespread dispersal<br />
o f rice occurred when migrating people or travelers brought rice grains along with<br />
them as food, merch<strong>and</strong>ise, gift, or seed. Movement o f rice plantings up or down<br />
the latitude or the altitudes or to new ecosystems, provided an opportunity for the<br />
heterogeneous <strong>and</strong> heterozygous plants in a population to manifest their individual<br />
adaptive traits <strong>and</strong> enabled human selection to begin. The com mon trend was to<br />
increase the reproductive capacity o f plants at the expense o f vegetative growth: The<br />
plants became thrifty in vegetative growth <strong>and</strong> the grain-to-straw ratio was raised.<br />
In rice, the rapid change from bold to slender grains in Southeast Asia in less than<br />
1000 years (Watabe <strong>and</strong> Toshimitsu, 1974), <strong>and</strong> the spread of the introduced Champa<br />
rices in reducing the growth duration of rices in China (Chang, 1987), are examples<br />
o f the power of human choke <strong>and</strong> selection.
Origin, Dotnestication, <strong>and</strong> Diversification 17<br />
Ecogenetic Races<br />
Another input generated by improved cultural practices o f humans in exploiting a<br />
new or modified ecosystem has led to the proliferation o f ecotypes in rice, which later<br />
formed ecogenetic races. The wide array o f ecotypes, as signified by their local group<br />
names (Figure 1.1.4), illustrates tlie unique situation in rice (Chang, 1985).<br />
On a broader basis, the greater divergence o f Asian rices over their African counterparts<br />
is given in Table 1.1.3 to illustrate the im pact o f geographical dispersal <strong>and</strong><br />
Ecogeographic<br />
differentiation<br />
Indica raee<br />
Javanica race<br />
Hydro-edapnic-culturalseasonal<br />
regime<br />
upl<strong>and</strong>(dryl<strong>and</strong>)<br />
aus(summer)<br />
borofwinter)<br />
T.aman(autumn)<br />
cereh,hsien,others<br />
eepwater,B>Aman<br />
floating<br />
pl<strong>and</strong><br />
bnlii(awned)<br />
;undil(awnles8)<br />
Sinica raci<br />
(Japónica)<br />
_ _ _<br />
~--------- lowl<strong>and</strong>(keng)<br />
---------h-------- 1<br />
0 . 1 1 5<br />
W ater depth(m)<br />
Figure 1.1.4. Grouping of Asion rice cultivors by ecogenetic race, hydrologic-edaphiccultural<br />
regime, <strong>and</strong> crop season, Cultivors grown in startdlng water belong to the lowl<strong>and</strong><br />
type. (Adapted from Chang, 1985.)<br />
TABLE 1.1.3.<br />
Contrast in Diversificotion: Orjrzn sotiVo vs. 0. glabemma<br />
Factor A sio W est Africa<br />
Latitudinal spread 10°Sto53"N 5° to 17“N<br />
Topography Hilly Flat<br />
Population density High Low<br />
Movement of people Continuous Little<br />
Iron tools Many None or few<br />
Draft animals Water buffalo <strong>and</strong> oxen Little used
\ ! I<br />
f ■<br />
18 Origin <strong>and</strong> History<br />
ecological diversity o f cultivation sites on varietal diversification. Similarly, but at<br />
different sites, for the wild progenitors O. meridionalis <strong>and</strong> O. glumaepatula, which<br />
would have the potential to be developed into cultigens, no cultigens evolved because<br />
o f the absence o f indigenous agriculture in Australia, <strong>and</strong> o f wetl<strong>and</strong> agronomy <strong>and</strong>.<br />
low population density o f humans in South America.<br />
The diversification o f O, sativa reached its peak in Asia. Most rice workers agree<br />
that the tropical rices, later called the indica race, served as the primary source of<br />
variations in other ecogenetic races. The differentiation process progressed farthest<br />
in China, where a distinct race was already differentiated over 10,000 years ago. Since<br />
the second century a.d., Chinese historical papers described two types o f rice: the<br />
drier cookmg type as hsien or sen <strong>and</strong> the stickier type as keng (Ting, 1949, 1961).<br />
The plant characteristics o f the hsien type correspond with those o f the tropical indica<br />
rices, whereas the keng type has a more thrifty vegetative growth habit, matures later,<br />
has dark green leaves, has higher yield potential in fertile soils <strong>and</strong> is more tolerant o f<br />
cool temperatures, especially in the seedling stage. In Japan, this temperate-zone race<br />
was named the japónica type by Kato et al. (1928) this term became more widely<br />
used because Kato’s papers have English summaries. In terms o f geographic <strong>and</strong><br />
historical convention, japónica is a misnomer, as rice culture in Japan was 7000 years<br />
behind that of China, <strong>and</strong> the Japanese obtained their rice seeds initially from China<br />
(Moriuaga, 1955, 1957), Therefore, this author suggested the use o f sínica (Chang,<br />
1976a,b) to denote the temperate-zone race that had evolved in China (Ting, 1949,<br />
1961). A third ecogeographic race having a larger plant size, slower growth, <strong>and</strong><br />
larger <strong>and</strong> bolder grains was recognized by Japanese workers <strong>and</strong> given the collective<br />
name javanica (M orinaga <strong>and</strong> Kuriyama, 1958; see also Chang, 1964b, for related<br />
details). The morphological phylogenetic, <strong>and</strong> physiological features o f javanica are<br />
unique (Matsuo, 1952; Chang et al., 1991). The three races are contrasted in Table<br />
1.1.4. Despite some deficiencies, the terms indica, sínica, <strong>and</strong> javanica are useful,<br />
as there is genetic incompatibility in their hybrid progenies (see Morinaga, 1954;<br />
IRRI, 1964; Chang, 1964b; Chang et al., 1991). On the other h<strong>and</strong>, the recent use<br />
o f “tropical japónicas” to denote certain ecostrains o f m inor importance would add<br />
to the problems o f botanical <strong>and</strong> geographical misuse, leading to further confusion,<br />
as we have seen in the case o f tlie Oryza species,<br />
Geographical dispersal <strong>and</strong> subsequent adoption o f introduced rices have played<br />
a vital role in the diversification o f O. sativa cultivars. The route o f dispersal from<br />
the belt of primary diversity to areas farther west (i.e„ tlie Middle East, Europe, East<br />
Africa, West Africa, <strong>and</strong> South America), has been summarized by Lu <strong>and</strong> Chang<br />
(1980). The United States obtained its rice germplasm from diverse sources in Asia<br />
(Adair <strong>and</strong> Jodon, 1973), while the often-cited tale of seed from Madagascar following<br />
a shipwreck appears to have been a short-hved incident.<br />
Geographic isolation following introduction <strong>and</strong>/or domestication invariably led<br />
to the development o f genetic isolating mechanisms <strong>and</strong> incompatibility. The partial<br />
sterility <strong>and</strong> aberrant recom bination found in indica x japónica crosses during the<br />
1940s became somewhat exaggerated by workers when they hedged heavily on the<br />
japónica type to increase grain yield in the indicas (see Parthasarathy, 1972). After<br />
high-yielding cultivars resulted from the use o f the semidwarfing gene, sd-1, fi-om<br />
Taiwan, other Chinese sources, <strong>and</strong> induced mutations, the use o f japónica parents<br />
was reduced greatly (see Chang <strong>and</strong> Li, 1991). However, the effect o f partial sterility<br />
in interracial crosses should not be overlooked (see IRRI, 1964).
k<br />
Origin, Domesticption, <strong>and</strong> Diversification 19<br />
TABLE 1.1.4. Ecogenetic Races of O ryza s a tiv a : Comparison of Their Morphological <strong>and</strong><br />
Physioiogical Characteristics<br />
Indica Sínica (or Japónica) iavaaica<br />
Broad to narrow, light Narrow, dark green leaves Broad, stiff, light green<br />
green leaves<br />
leaves<br />
Long to short, slender, Short, roundish grains Long, broad, thick grains<br />
somewhat flat grains<br />
Profuse tillering Medium tillering Low tillering<br />
Tah to intermediate plant Short to intermediate plant TaU plant stature<br />
stature<br />
stature<br />
Mostly awnless Awnless to long-awned Long awned or awnless<br />
Thin, short hairs on lemma Dense, long hairs on Long hairs on lemma <strong>and</strong><br />
<strong>and</strong> palea lemma <strong>and</strong> palea palea<br />
Easy shattering Low shattering Low shattering<br />
Soft plant tissues Hard plant tissues Hard plant tissues<br />
Varying sensitivity to Zero to low sensitivity to Low sensitivity to<br />
photoperiod photoperiod photoperiod<br />
23-31% amylose 10-20% amylose 20-25% amylose<br />
Variable gelatinization Low gelatinization Low gelatinization<br />
temperatures (low or<br />
intermediate)<br />
temperature<br />
temperature<br />
RECENT LOSS IN GENETIC DIVERSITY<br />
The remarkable genetic diversity found in wild species, as well as the traditional<br />
l<strong>and</strong>race cultivars, reached its peak by the first half o f the twentieth century before<br />
scientific breeding assumed a central position in many national rice improvement<br />
programs. It was wise o f many Asian countries to began to collect <strong>and</strong> conserve their<br />
indigenous <strong>and</strong> introduced rice cultivars before the 1950s. As the green revolution in<br />
rice was centered largely around the sd-1 gene <strong>and</strong> the cytoplasm o f the cultivai- Gina<br />
(China), the genetic base o f improved O. sativa cultivars all over the world became<br />
greatly narrowed. Meanwhile, numerous traditional types were displaced <strong>and</strong> lost<br />
from farmers’ fields. Concurrently, disturbance or destruction o f many natural habitats<br />
has reduced the populations o f wild relatives (see Chang, 1984,1994; Vaughan <strong>and</strong><br />
Chang, 1992). The continuing trend toward erosion o f genetic diversity is worrisome<br />
in the face o f increasing pest epidemics under intensive cultivation <strong>and</strong> global climate<br />
change. New gene pools are not only indispensable to fill new needs, but genetic<br />
diversity also may produce de novo variations <strong>and</strong> elevated epistasis (Rasmusson <strong>and</strong><br />
Phillips, 1997). Epistasis <strong>and</strong> its ramifications have not been fully explored <strong>and</strong> used<br />
in breeding self-poUinated crops. It appears worthwhile to probe the polymorphic<br />
<strong>and</strong> latent gene com binations in not-so-highly inbred rice strains.<br />
Fortunately for the rice-eating world, the genetic resources o f Oryza species <strong>and</strong><br />
traditional cultivars have been collected extensively by international efforts <strong>and</strong> conserved<br />
under the leadership o f the International <strong>Rice</strong> Research Institute in recent<br />
decades to a greater extent than for m ost other food crops (Chang, 1992), Active<br />
use o f the rich gene pools a few decades ago is reflected in the sustained <strong>production</strong>
I ü<br />
20 Origin <strong>and</strong> History<br />
increase for rice since the green revolution began in the early 1970s. <strong>Rice</strong> plants also<br />
are more amenable than other cereals to in vitro culture <strong>and</strong> regeneration. Thus it<br />
remains for rice workers to continue the exploitation o f genetic potential found in this<br />
rich germplasm, intensify' international <strong>and</strong> multidisciplinary efforts <strong>and</strong> m issionoriented<br />
evaluation <strong>and</strong> research, <strong>and</strong> diversify the genetic base o f m ajor cultivars.<br />
<strong>Rice</strong> farmers who were unsung heroes in selecting <strong>and</strong> improving rice before science<br />
came into play, as well as in the improvement o f cultural practices <strong>and</strong> farm tools,<br />
should be involved more actively in future rice improvement programs. Meanwhile, it<br />
is envisaged that incerases in rice <strong>production</strong> will not keep up with hum an population<br />
growth <strong>and</strong> the ever-exp<strong>and</strong>ing preference for rice in the developing world. Many<br />
unfavored l<strong>and</strong> areas where local environments are harsh (e.g., deepwater areas <strong>and</strong><br />
tidal swamps), will remain at the subsistence level at which rice farming began several<br />
millennia ago (Chang, 1999).<br />
LOOKING AHEAD<br />
Retracing the mysterious past o f this frail yet economically mighty grass is not merely<br />
an academic pursuit but an exercise in finding useful pointers for the future. Along<br />
this tortuous path we have witnessed the usefulness o f multidisciplinary analysis <strong>and</strong><br />
how international collaboration has led to fruitful ventures in conserving <strong>and</strong> using<br />
rice germplasm. W ith added tools from bio<strong>technology</strong>, scientists should achieve more<br />
<strong>and</strong> accelerated advances in rice improvement. The 80,000-accession rice collection<br />
conserved at the the International <strong>Rice</strong> Research Institute should provide additional<br />
useful gene pools.<br />
Despite the shrinking supply o f necessary resources on all fronts— ^l<strong>and</strong>, water,<br />
soil productivity, genetic diversity, labor, <strong>and</strong> financial incentives— crop productivity<br />
must be raised. We must unlock the genetic <strong>and</strong> physiological mechanisms o f the rice<br />
plant to exp<strong>and</strong> its geographical adaptation <strong>and</strong> to overcome ecological constraints.<br />
Well-planned coordinated research must be revived in the developing world. It will<br />
be the tedious <strong>and</strong> painstaking research efforts o f scientists, extension staff, urban<br />
consumers, <strong>and</strong> rice farmers that will bear fruit for users. We have seen great human<br />
ingenuity from all these sectors in the past, hence we should be able to make greater<br />
advances through increased effort in the future. The impending increase in human<br />
growth, gobal climate change, <strong>and</strong> the sheer human need for this cereal will necessitate<br />
drastic changes in our attention to productivity, sustainability, <strong>and</strong> other long-term<br />
needs for conservation o f natural <strong>and</strong> human resources <strong>and</strong> will cause us to modify<br />
our efforts accordingly. Let us begin now.<br />
REFERENCES<br />
Adair, C. R., <strong>and</strong> N. E. Jodon, 1973. Distribution <strong>and</strong> <strong>origin</strong> o f species, botany, <strong>and</strong><br />
genetics. In <strong>Rice</strong> in the United States: Varieties <strong>and</strong> Production. A RS-USD A Agricultural<br />
H<strong>and</strong>book 289. U.S. Departm ent of Agriculture, Washington, DC.<br />
Amano, M. 1962. Research on Chinese Agricultural History (in lapanese). Tokyo.<br />
An, Z. 1989. Prehistoric agriculture in China, In D. R. Harris <strong>and</strong> G. C. Hillman (eds.),<br />
Foraging <strong>and</strong> Farming. Unwin Hyman, London, pp. 643-649.
k<br />
Origin, Domestkation, <strong>and</strong> Diversification 21<br />
Arumuganathan, K., <strong>and</strong> E. D. Earle. 1991. Estim ation o f nuclear DNA content o f<br />
plants by flow cytometry. Plant Mol Biol Rep. 9(3):229-233.<br />
Bardenas, E. A., <strong>and</strong> T. T. Chang. 1966. M orpho-taxonom ic studies o f Oryza giaberrima<br />
Steud. arid its related wild taxa, O. hreviligulata A. Chev. et Roehr <strong>and</strong><br />
O. stapfii Roschev. Bot Mag. Tokyo 79:791-798.<br />
Chang, T. T. 1964a. Report o f a poU on Oryza species. In <strong>Rice</strong> Genetics <strong>and</strong> Cytogenetics.<br />
IRRI-Elsevier, Amsterdam, pp. 24r-27.<br />
Chang, T. T. 1964b. Present Knowledge of <strong>Rice</strong> Genetics <strong>and</strong> Cytogenetics, Tech. Bull. 1.<br />
International <strong>Rice</strong> Research Institute, M anila, The Philippines.<br />
Chang, T. T. 1975. Species o f rice. In D . H, Grist (ed.), <strong>Rice</strong>, 5th ed. Longman, London,<br />
pp. 532-533.<br />
Chang, T. T. 1976a. The rice cultures. Philos. Trans. R. Soc, London B 275:143-157.<br />
Chang, T. T. 1976b. The <strong>origin</strong>, evolution, cultivation, dissemination, <strong>and</strong> diversification<br />
o f the Asian <strong>and</strong> African rices. Euphytica 25:425-441.<br />
Chang, T. T. 1976c. <strong>Rice</strong>. In N. W. Simmonds (ed.), Evolution of Crop Plants. Longman,<br />
London, pp. 98-104.<br />
Chang, T. T. 1976d. Manual on Genetic Conservation of <strong>Rice</strong> Germ Plasm for Evaluation<br />
<strong>and</strong> Utilization. International <strong>Rice</strong> Research Institute, Manila, The Philippines.<br />
Chang, T. T. 1976e. Paleographic <strong>origin</strong> o f the wild taxa in genus Oryza <strong>and</strong> their<br />
relationship. Int. Rke Res. Newsl 2 (7 6 ):4.<br />
Chang, X T . 1979. Early <strong>history</strong> of rice crop (in Chinese). In T . H. Shen <strong>and</strong> Y. S. Chao<br />
(eds.), Essays on Chinese Agricultural History. Taiwan Commercial Press, Taipei,<br />
Taiwan, pp. 49-6 8 .<br />
Chang, X X 1983. The <strong>origin</strong> <strong>and</strong> early cultures o f the cereal grains <strong>and</strong> food legumes.<br />
In D. N. Keightley (ed.). The Origins of Chinese Civilization. University o f California<br />
Press, Berkeley, CA, pp. 65-94.<br />
Chang, X X 1984. Conservation o f rice genetic resources: luxury or necessity? Science<br />
224:251-256.<br />
Chang, X T . 1985. Crop <strong>history</strong> <strong>and</strong> genetic conservation: rice— a case study. Iowa<br />
State J. Res. 59:425-455.<br />
Chang, X X 1987. The impact o f rice on human civilization <strong>and</strong> population expansion.<br />
Interdiscip. Sei. Rev. 12:63-69.<br />
Chang, X X 1988. Taxonom ic key for identifying the 22 species in the genus Oryza.<br />
Int <strong>Rice</strong> Res. Newsl 13(5):4-5,<br />
Chang, X X 1989. Dom estication <strong>and</strong> spread o f the cultivated rices. In D. R. Harris<br />
<strong>and</strong> G. C. Hillman (eds.), Foraging <strong>and</strong> Farming. Unwin Hyman, London,<br />
pp. 408-417.<br />
Chang, X X 1992. Availability o f plant germplasm for use in crop improvement. In<br />
H. X Stalker <strong>and</strong> J. P. Murphy (eds.), Plant Breeding in the 1990s. CAB International,<br />
Wallingford, Oxon, Engl<strong>and</strong>, pp. 17-35.<br />
Chang, X X 1994. The biodiversity crisis in Asian crop <strong>production</strong> <strong>and</strong> remedial m easures.<br />
In C. I. Peng <strong>and</strong> C. H. Chou (eds.), Biodiversity <strong>and</strong> Terrestrial Ecosystems.<br />
Institute o f Botany, Academia Sinica, Nankang, Taiwan, pp. 25-41.<br />
Chang, X X 1999. The prospect o f rice <strong>production</strong> increase. In Food Needs of the Developing<br />
World in the Early Twenty-First Century. Pontifical Academy o f Sciences<br />
<strong>and</strong> Oxford University Press, Oxford.<br />
Chang, X X , <strong>and</strong> C. C. Li. 1991. Genetics <strong>and</strong> breeding. In B. S. Luh (ed.). <strong>Rice</strong>, Vol. 1,<br />
Production, 2nd ed. AVI-VanNostr<strong>and</strong> Reinhold, New York, pp. 23-101.
1<br />
22 Origin <strong>and</strong> History<br />
Chang, T. T„ <strong>and</strong> B. S. Luh. 1991. Overview <strong>and</strong> prospects o f rice <strong>production</strong>. In<br />
B. S. Luh (ed.), <strong>Rice</strong>, Vol. 1, Production, 2nd ed. AVI-VanNostr<strong>and</strong> Reinhold, New<br />
York, pp. 1-11.<br />
Chang, T. T,, A. P. M arciano, <strong>and</strong> G. C. Loresto. 1977. M orpho-agronom ic variousness<br />
<strong>and</strong> econom ic potentials o f Oryzaglaberrima <strong>and</strong> wild species in the genus Oryza.<br />
Meeting on African <strong>Rice</strong> Species. ORSTOM -IRAT, Paris, pp. 6 7 -7 5 .<br />
Chang, T, T., Y. Pan, Q. Chu, R. Reiris, <strong>and</strong> G. C. Loresto. 1991. Cytogenetic, electrophoretic,<br />
<strong>and</strong> root studies o f javania rices. <strong>Rice</strong> Genetics II. International <strong>Rice</strong><br />
Research Institute, Manila, The Philippines, pp. 2 1 -3 1 .<br />
Chao, Y. S. 1979. Evolutionary changes in the water wheel-pump o f China (in Chinese).<br />
In T. H. Shen <strong>and</strong> Y. S. Chao (eds.). Essays on Chinese Agricultural History.<br />
Taiwan Commercial Press, Taipei, Taiwan, pp. 116-173.<br />
Chatterjee, D. 1948. A modified key <strong>and</strong> enumeration o f the species o f Oryza Linn.<br />
Indian /. Agric. Sd, 18:185-194.<br />
Chen, P. C. 1995, Preliminary research on excavated carbonized rice excavated from<br />
Chia-Hu site, H o-nan (in Chinese), Agric. Archaeol 3:94-95.<br />
Chung, M . C., C. N. Ning, <strong>and</strong> H. K. Wu. 1993. Localization o f ribosom al RNA genes<br />
on rice chromosomes. Bot. BuUl Acad. Sin. 34:43-55.<br />
Copel<strong>and</strong>, E. B. 1924. <strong>Rice</strong>. Macmillan, London.<br />
David, C. C. 1991. The world rice economy; challenges ahead. In G. S. Khush <strong>and</strong><br />
G. H. Toenniessen (eds.), Rke Bio<strong>technology</strong>. CAB International <strong>and</strong> IRRI, Wallingford,<br />
Oxon, Engl<strong>and</strong>, pp. 1-18.<br />
de C<strong>and</strong>olle, A. 1886. Origin des Plants Cultives, 4th ed. F. Alcan, Paris.<br />
Evans, L, T. 1989. Cultivated <strong>Rice</strong>,, book review. Field Crop Res. 21:167-168.<br />
FAO. 1996. The Sixth World Food Survey. Food <strong>and</strong> Agriculture Organization o f the<br />
United Nations, Rome.<br />
Fukui, K. 1996. Advances in rice chromosom e research, 1900-95. In G. S. Khush (ed.),<br />
<strong>Rice</strong> Genetics III. International <strong>Rice</strong> Research Institute, Manila, The Philippines,<br />
pp. 117-130.<br />
Gale, M. D., K. M . Devos, <strong>and</strong> G. Moore. 1996. <strong>Rice</strong> as the pivotal genome in the<br />
new era o f grass comparative genetics. In G. S. Khush (ed.). <strong>Rice</strong> Genetics III.<br />
International <strong>Rice</strong> Research Institute, Manila, The Philippines, pp. 77-84.<br />
Ghose, R. L. M ., M. B. Ghatge, <strong>and</strong> V. Subraraanian. 1960. <strong>Rice</strong> in India. Indian<br />
Council for Agricultural Research, New Delhi.<br />
Grist, D. H. 1975. <strong>Rice</strong>, 5th ed. Longman, London.<br />
Hakim, K. L., <strong>and</strong> S. D. Sharraa. 1974. Localized distribution o f certain characters o f<br />
rices in northeast India. Indian }. Plant Genet. Breed. 34A: 16-21.<br />
Hallam, A. 1973. A Revolution in the Earth Sciences: From Continental Driß to Plate<br />
Tectonics. Clarendon Press, Oxford.<br />
Hamada, H. 1956. Ecotypes o f rice. In H. Kihara (ed.). L<strong>and</strong> <strong>and</strong> Crops of Nepal,<br />
Himalaya. Kyoto University, Kyoto, Japan, pp. 263-312.<br />
Hanks, L. M. 1972. <strong>Rice</strong> <strong>and</strong> Man. Aldine-Atherton, Chicago.<br />
Harlan, J. R. 1975. Crops <strong>and</strong> Man. Am erican Society o f Agronomy <strong>and</strong> the Crop<br />
Science Society o f America, Madison, W I.<br />
Harlan, J. R. 1977. The <strong>origin</strong>s o f cereal agriculture in the old world. In C. A. Reed<br />
(ed.). Origins of Agriculture. M outon, The Hague, The Netherl<strong>and</strong>s, pp. 357-383.<br />
Harlan, J. R. 1989. The tropical African cereals. In D. R. Harris <strong>and</strong> G. C. Hillman<br />
(eds.). Foraging <strong>and</strong> Farming. Unwin Hyman, London, pp. 335-343.
Origin^ Domestication, <strong>and</strong> Diversification 23<br />
Harlarij J. R., <strong>and</strong> J. M . J. de Wet. 1971. Toward a rational classification o f cultivated<br />
plants. Taxon 20:509-517.<br />
Harlan, J. R., J. M, J de Wet, <strong>and</strong> E. G. Price. 1973, Comparative evolution o f cereal<br />
Evolution 27:311-325.<br />
Hu, C. H. 1964. Further studies on the chromosome morphology of Oryza sativa L<br />
In <strong>Rice</strong> Genetics <strong>and</strong> Cytogenetics. IRRI-Elsevier, Amsterdam, pp. 51-61.<br />
Hunan Provincial Archaeological Research Institute. 1990. Report on excavation from<br />
Peng-tou-shan Neolithic site in Hunan Province (in Chinese). Wen Wu 8:17-29,<br />
IRRI. 1964. <strong>Rice</strong> Genetics <strong>and</strong> Cytogenetics. IRRI-Elsevier, Amsterdam.<br />
IRRI. 1995. World <strong>Rice</strong> Statistics, 1993-94. International <strong>Rice</strong> Research Institute, M a<br />
nila, The Philippines.<br />
IRRI-CIAT-W ARDA. 1997. <strong>Rice</strong> Almanac, 2nd ed. International <strong>Rice</strong> Research Institute,<br />
Manila, The Philippines.<br />
Kato, S., H. Kosaka, <strong>and</strong> S. Kara, 1928. On the affinity o f rice varieties as shown by the<br />
fertility o f hybrid plants. BuU. Set. Fak. Terkult Kyushu Imperial Univ. 3:132-147.<br />
Khush, G. S., <strong>and</strong> T. Kinoshita, 1991. <strong>Rice</strong> karyotype, marker genes <strong>and</strong> linkage<br />
groups. In G. S. Khush <strong>and</strong> G. H. Toenniessen (eds.). <strong>Rice</strong> Bio<strong>technology</strong>. IRRI<br />
GAR International, Wallingford, Oxon, Engl<strong>and</strong>, pp. 83-108.<br />
Kihara, H., <strong>and</strong> T. C. Katayama. 1964. Occurrence o f Indica <strong>and</strong> Japónica Types among<br />
Sikkimese <strong>Rice</strong> Varieties. NIG, Rep. a 14:67-68. National Institute o f Genetics,<br />
Misima, Japan.<br />
Kurata, N. 1986. Chromosome analysis o f mitosis <strong>and</strong> meiosis in rice. In <strong>Rice</strong> Genetics.<br />
International <strong>Rice</strong> Research Institute, Manila, The Philippines, pp. 143-152.<br />
Kurata, N., et al, 1994. Conservation o f genetic structure between rice <strong>and</strong> wheat.<br />
Bio<strong>technology</strong> 12:276-278.<br />
Lu, J. J., <strong>and</strong> T. T. Chang. 1980. <strong>Rice</strong> in its temporal <strong>and</strong> spatial perspectives. In B. S.<br />
Luh (ed.), <strong>Rice</strong> Production <strong>and</strong> Utilization. AVI, Westport, CT, pp. 1-74.<br />
Matsuo, T‘. 1952. Genecological studies on cultivated rice. Bull. Natl. Inst. Agrie. Sei.<br />
Jpn. D 3 : l - l l l .<br />
Morinaga, T. 1954. Classification o f rice varieties on the basis o f affinity. In Studies<br />
on <strong>Rice</strong> Breeding, Suppl. 4. Japanese M inistry o f Agriculture <strong>and</strong> Forestry, Tokyo,<br />
pp. 1-14.<br />
Morinaga, T. 1955. The geneology o f Japanese rice (in Japanese). Agrie. Hortic. 30:<br />
1275-1277.<br />
Morinaga, T. 1957. <strong>Rice</strong> of Japan (in Japanese). Yokendo Press, Tokyo.<br />
Morinaga, T. 1964. Cytogenetical investigations on species. In <strong>Rice</strong> Genetics <strong>and</strong><br />
Cytogenetics. IRRI-Elsevier, Amsterdam, pp. 91-102.<br />
Morinaga, T., <strong>and</strong> H, Kuriyama. 1958. Intermediate type o f rice in the subcontinent<br />
of India <strong>and</strong> Java. Jpn. J. Breed. 7:253-259.<br />
M orishima, H. 1986. Wild progenetoiy o f cultivated rice <strong>and</strong> their population dynamics.<br />
In <strong>Rice</strong> Genetics. International <strong>Rice</strong> Research Institute, Manila, the Philippines,<br />
pp. 3 -1 4 .<br />
Nakagahra, M. T., T. Akihama, <strong>and</strong> K. Hayasli. 1975. Genetic variation <strong>and</strong> geographic<br />
dine o f esterase isozymes in native rice varieties. Jpn. J. Genet. 50:373-382.<br />
Ng, N. Q., T. T. Chang, D. A. Vanghan, <strong>and</strong> C. Ziiflo-AIteveros. 1991. African rice<br />
diversity, conservation <strong>and</strong> prospects for crop improvement. In N. Q, Ng et al.<br />
(eds.). Crop Genetic Resources of Africa, vol. 2. IITA -IBPG R -U N EP-C N R . Trinity<br />
Press, Cambridge, pp. 213-227.
24 Origin <strong>and</strong> History<br />
Nishiyama, T. 1949. Development o f rice industry in China (in Japanese). Compr.<br />
Agric, Res, 3(1):118~159.<br />
Oka, H. I. 1988. Origin o f Cultivated <strong>Rice</strong>. Japan Scientific Societies Press, Tokyo, <strong>and</strong><br />
Elsevier, Amsterdam.<br />
Oka, H. L, <strong>and</strong> W. T. Chang. 1964. Observations o f Wild <strong>and</strong> Cultivated <strong>Rice</strong> Species in<br />
Africa. National Institute of Genetics, Misima, Japan.<br />
Oka, H. I., <strong>and</strong> H, Morishima. 1967. Variation in the breeding system o f a wild rice,<br />
Oryza perennis. Evolution 21:249"258.<br />
Parthasarathy, N. 1972. <strong>Rice</strong> breeding in tropical Asia up to 1940. In <strong>Rice</strong> Breeding.<br />
International <strong>Rice</strong> Research Institute, Manila, The Philippines, pp. 5 -29.<br />
Porteres, R. 1956. Taxonomie agrobotanique des riz cultives O. sativa Linné, et. O. glaherrima<br />
Steud. /. Agrîc. Trop. Bot. A ppl 3:341-384, 541-580, 6 27-700, 8 2 1 -<br />
850.<br />
Rasmusson, D. C., <strong>and</strong> R. L. Phillips. 1997. Plant breeding progress <strong>and</strong> genetic diversity<br />
from de novo variation <strong>and</strong> elevated epistasis. Crop Sei 37:303-310.<br />
Roschevicz, R, 1931. A contribution to the knowledge o f rice (in Russian); (English<br />
translation o f IRRI). Bull. Appl. Bot. Genet. Plant Breed. All-Union Institute of<br />
Plant Breeding, Leningrad.<br />
Sampath, S. 1962. The genus Oryza: its taxonomy <strong>and</strong> species relationships. Oryza<br />
1:1-29.<br />
Sharraa, S. D,, <strong>and</strong> S. V. S, Shastry. 1965. Taxonomic studies in genus Oryza L. ?.<br />
O. rufipogon Griff, sensu stricto <strong>and</strong> O. nivara Sharma et Shastry nom nov. Indian<br />
/. Plant Genet. Breed. 25:157-167.<br />
Shastry, S. V, S., D. R. RangaRao, <strong>and</strong> R. N. Misra. 1960. Pachytene analysis in Oryza. I.<br />
Chromosome morphology in Oryza sativa. Indian J. Plant Genet. Breed. 2 0 :1 5 -<br />
21.<br />
Smartt, J., <strong>and</strong> N. W. Simmonds (eds.). 1995. Evolution o f Crop Plants, 2nd ed. Longman,<br />
Harrow, Essex, Engl<strong>and</strong>.<br />
Tateoka, T. 1963. Taxonomic studies o f Oryza. III. Key to the species <strong>and</strong> their enumeration.<br />
Bot. Mag. Tokyo 76:165-173.<br />
Tateoka, T. 1964, Taxonom ic studies o f the genus Oryza. In <strong>Rice</strong> Genetics <strong>and</strong> Cytogenetics.<br />
IRRI-Elsevier, Amsterdam, pp. 15-21.<br />
Ting, Y, 1949. Ancient cultivation o f Keng <strong>and</strong> Hsien rices in China <strong>and</strong> their distribution.<br />
Agron. Bull Sun Yatsen Univ. 6:1-32.<br />
Ting, Y, (ed.). 1961. Chinese Culture o f Lowl<strong>and</strong> <strong>Rice</strong> (in Chinese). Agricultural Publishing<br />
Society, Peking.<br />
Vaughan, D. A. 1994. The Wild Relatives o f <strong>Rice</strong>. International <strong>Rice</strong> Research Institute,<br />
Manila, The Philippines.<br />
Vaughan, D. A., <strong>and</strong> T. T. Chang. 1992. In situ conservation o f rice genetic resources.<br />
Econ. Bot. 46:368-383.<br />
Wang, X. K. 1993. Origin, evolution <strong>and</strong> taxonomy o f the cultivated rice o f China (in<br />
Chinese). In C. Ying (ed.), <strong>Rice</strong> Genetic Resources o f China. Chinese Agricultural<br />
Science <strong>and</strong> Technology Publishing Press, Beijing, pp. 1-16.<br />
Watabe, T., <strong>and</strong> K. Toshimitsu. 1974. Morphological properties o f old rice grains<br />
recovered from ruins in the Indian subcontinent. Prelim. Rep. Tottori Univ. S ei<br />
Surv. 2:1-18.<br />
Watabe, T., T. Akihama, <strong>and</strong> O. Kinoshita. 1970. The alteration o f cultivated rice in<br />
Thail<strong>and</strong> <strong>and</strong> Cambodia. Southeast Asian Stud. 8:36-45.
Origin, Domestication, <strong>and</strong> Diversificotion 25<br />
Watt, G. 1891. Dictionary o f the Economic Products o f India.. V. W. H. Allen, London,<br />
pp. 498-508.<br />
Whyte, R. O. 1972. The Gramineae, wild <strong>and</strong> cultivated o f raonsoonal <strong>and</strong> tropical<br />
Asia. I. Southeast Asia. Asian Perspect. 15:127-151,<br />
Wu, H. K., <strong>and</strong> M. C. Chung. 1986. <strong>Rice</strong> karyotype analysis. In <strong>Rice</strong> Genetics. International<br />
<strong>Rice</strong> Research Institute, Manila, The Philippines, pp. 135-142.<br />
Wu, H. K., et al. 1991. Localization o f specific repetitive DNA sequences in individual<br />
rice chromosom es. Chromosoma 100:330-338.<br />
Xie, Z. W , Y. Zhou, B. R. Lu, <strong>and</strong> D. Y. Hong. 1998. Phylogenetic relationship o f genus<br />
Oryza as revealed by RAPD analysis. In t <strong>Rice</strong> Res, Notes 23(3 ):6 -8 .<br />
Zhao, X., T. Wu, Y, Xie, <strong>and</strong> R. Wu. 1989. Genome-specific repetitive sequences in the<br />
genus Oryza. Theor. A ppl Genet. 78:201-209.<br />
SUGGESTED READINGS<br />
Akihama, T., <strong>and</strong> K. Toshimitsu. 1972. Geographical distinction o f morphological<br />
variation on wild rices in central <strong>and</strong> southern India. Tottori Univ. Sei. Surv.<br />
(1971) 1:48-59.<br />
Chang, T, T. 1966. The need for genetic investigations to assist rice breeders in tropical<br />
Asia. Indian J, Plant Genet. Breed. 26A :206-216.<br />
Chang, T. T., <strong>and</strong> H, I. Oka. 1976. Genetic variousness in the climatic adaptation o f<br />
rice cultivars. In Climate <strong>and</strong> <strong>Rice</strong>. International <strong>Rice</strong> Research Institute, Manila,<br />
The Philippines, pp. 87-111.<br />
Chang, T. T., C. R. Adair, <strong>and</strong> T. H. Johnston. 1982. The conservation <strong>and</strong> use o f rice<br />
genetic resources. Adv. Agron. 35:37-91.<br />
Chevalier, A. 1932. Nouvelle contribution aPétude systématique des Oryza. Rev. Int.<br />
Bot. Appl. Agrie. Trop. 12:1014-1032.<br />
Oka, H. I. 1964. Pattern o f interspecific relationship <strong>and</strong> evolutionary dynamics. In<br />
<strong>Rice</strong> Genetics <strong>and</strong> Cytogenetics. IRRI-Elsevier, Amsterdam, pp. 71-90.<br />
Oka, H. 1 .1974. Experimental studies on the <strong>origin</strong> o f cultivated rice. Genetics 7 8 :4 7 5 -<br />
486.<br />
Oka, H. L, <strong>and</strong> W. T. Chang. 1959. The impact o f cultivation on populations o f wild<br />
rice, Oryza sativa f. spontanea. Phyton 13:105-117.<br />
Oka, H. I., <strong>and</strong> W. T. Chang. 1961. Hybrid swarms between wild <strong>and</strong> cultivated rice<br />
species Oryza perennis <strong>and</strong> O. saHva. Evolution 15:418-430.<br />
Sano, Y., H. M orishim a, <strong>and</strong> H. I. Oka. 1988. Intermediate, perennial-annual populations<br />
o f Oryza perennis found in Thail<strong>and</strong> <strong>and</strong> their evolutionary significance.<br />
Bot. Mag. Tokyo 93:291-305.
Chopfer<br />
1.2<br />
Bíosystematícs of the Genus O ryza<br />
Duncan A. Vaughan<br />
National Institute of Agrobiological Sciences<br />
Ibaraki, Japan<br />
Hiroko Moris hima<br />
Formerly at the National I nstitute of Genetics<br />
Shizuoka, Japan<br />
ANTIQUITY OF o r a<br />
TAXONOMIC POSITION OF ORYZA IN THE POACEAE<br />
OÄYZASCHifCMJ?/PILGER<br />
ORYZA BRACHYAmA CHEV. ET ROEHR.<br />
o r a O Ä 4 T O H COMPLEX<br />
ORYZA R ID L E Y im ? m<br />
ORYZA O F f í c m u s m m i<br />
Oryza officinalis Wall ex Walt<br />
Oryzae/fA/ngerf Peter<br />
Oryza rhizomotis D. A. Vaughan<br />
Oryza m inuta J. S. Presl. ex C. B. Presl.<br />
Oryza punctata Kotschy ex Steud.<br />
Oryza australiensis Domin<br />
CCDD Genome Species Complex in Latin America<br />
Oryz0 /r//t/o//0 Desv.<br />
Oryza gr<strong>and</strong>igiumis (Doell.) Prod,<br />
Oryza alta Swollen<br />
o r a SAHM COMPLEX<br />
Asia<br />
Taxonomy<br />
Evolution<br />
Oryza rvfipogon subsp. rufipogon<br />
Oryza rufipogon subsp. nivara<br />
Africa<br />
Oryza /o0g/s/0/n/not0 Chev. et Roehr.<br />
Oryza barthn A. Chev.<br />
<strong>Rice</strong>: Origin, History, Tedmology, <strong>and</strong> Production, edited by C. Wayne <strong>Smith</strong><br />
ISBN 0-471-34516-4 © <strong>2003</strong> John Wiley & Sons, Inc.<br />
27
28 Origin <strong>and</strong> History<br />
Australia <strong>and</strong> New Guinea<br />
Or>7iimer/i//offii//s Ng<br />
Oryza rufipogon sensu lacto<br />
Latin America<br />
WEEDY RICE<br />
Oryza glumaeptJtula Steud.<br />
Taxonomy<br />
Evolution<br />
RESEARCH DIRECTIONS<br />
CAUTIONARY NOTE<br />
REFERENCES<br />
ANTIQUITY OF ORYZA<br />
To underst<strong>and</strong> the biosystematics of the genus Oryza, inform ation regarding the possible<br />
time scale o f evolution of the genus <strong>and</strong> its various components can be very<br />
helpful. Unfortunately, molecular clock data with respect to evolutionary events in<br />
the genus are scarce <strong>and</strong> estimates need to be revised constantly in the light o f new<br />
information. For example, recently discovered fossils dating back 90 m illion years<br />
represent the oldest record to date o f monocotyledon flowers (G<strong>and</strong>olfo et al., 1998).<br />
These fossils, however, have presented scientists with a dilemma because either the<br />
monocotyledon clade is older than previously thought or the characters that constitute<br />
a “primitive’’ monocotyledon must be revised. Literature regardmg the possible<br />
dates o f various events related directly or indirectly to the evolution o f the genus Oryza<br />
are presented (Table 1,2.1).<br />
TABLE 1.2.1.<br />
Dates Concerning the Ancestry <strong>and</strong> Divergence of the Genus Oryza<br />
Event Possible D ate'’ Reference<br />
Origin of monocotyledons Prior to 90 mya G<strong>and</strong>olfo et al. (1998)<br />
Probable earliest Oryza Tertiary (after 70 mya?) Second (1991a)<br />
Divergence of Oryza <strong>and</strong> Zea 50 mya Stebbins (1981), Wolfe et al.<br />
ancestors (1989), Gaut (1998)<br />
Divergence of Asia vs. 15 mya Second (1991a)<br />
African species of the O.<br />
officinalis complex<br />
Divergence of the Australian 15 mya Second (1991a)<br />
(Oceanian) <strong>and</strong><br />
non-Oceanian strain of<br />
the Oryza<br />
Divergence of African <strong>and</strong> 7 mya Second (1991a)<br />
Asian AA genome rice<br />
species 230-680,000 years ago Barbier et al (1991)<br />
"mya, iiiilUon years ago.
Biosystemalícs of the Genus Of/zo 29<br />
TAXONOMIC POSITION OF ORYZA IN THE POACEAE<br />
The genus Or/za, named by Linnaeus in 1753, is in the botanical family Poaceae. The<br />
general consensus among taxonomists is that Oryza is in the tribe Oryzeae, subfamily<br />
Bambusoideae (Clayton <strong>and</strong> Renvoize, 1986; Soreng <strong>and</strong> Davis, 1998). However,<br />
Oryza has been placed in the tribe Oryzeae, in the subfamily Pooideae (Tzvelev,<br />
1989), in the supertribe Oryzanae (Watson et al., 1985), <strong>and</strong> tlie subfamily Oryzoideae<br />
(Duistermaat, 1987). One reason for these varying interpretations is that Oryza <strong>and</strong><br />
its relatives share some key characteristics that are shared with Bambusoideae (leaf<br />
anatomy, stamen number, <strong>and</strong> small chromosom es) <strong>and</strong> some shared with Pooideae<br />
(embryo type). Recent phylogenetic analysis has confirmed the intermediate position<br />
o f Oryzeae <strong>and</strong> related tribes (Soreng <strong>and</strong> Davis, 1998). Soreng <strong>and</strong> Davis (1998)<br />
concluded that Bambusoideae does not represent a monophyletic group; thus the<br />
tribe Oryzeae <strong>and</strong> its allies may have a distinct lineage in the Poaceae.<br />
The closest tribe to Oryzeae is Ehrharteae Nevsld, which consists o f four genera<br />
<strong>and</strong> about 40 species from tropical <strong>and</strong> southern Africa, Asia, Australia, <strong>and</strong> New<br />
Zeal<strong>and</strong> (Tzvelev, 1989).<br />
The tribe Oryzeae consists o f 12 genera <strong>and</strong> more than 70 species (Table 1.2.2).<br />
Apart from the genus Oryza, Zizania also consists o f species o f econom ic im portance<br />
(Z. palustris is the "wUd rice” o f U.S, cuisine, <strong>and</strong> Z. latifolia is a vegetable in Chinese<br />
TABLE 1.2.2.<br />
Tribe O/yzeoe<br />
Genera, Number of Species, Chromosome Number, <strong>and</strong> Spikelef Structure in the<br />
N um ber of<br />
Chrom osom e<br />
Genus<br />
Species<br />
Distribution"<br />
N um ber (2n)<br />
Spibelet Structure<br />
Oryza 22 Pantropical (T) 24, 48 Bisexual<br />
Leersia 17 Worldwide 24, 48, 60, 96 Bisexual<br />
Chikusichloa 3 China, Japan (t) 24 Bisexual<br />
Hygroryza 1 Asia (t + T) 24 Bisexual<br />
Porteresia 1 South Asia (T) 48 Bisexual<br />
Zizania 4 Europe, Asia, North 30,34 Unisexual<br />
America (t + T)<br />
Luziola^ 11 North America (t + 24 Unisexual<br />
T)<br />
Zizaniopsis 5 North <strong>and</strong> South 24 Unisexual<br />
America (t + T)<br />
Rhynchoryza 1 South America (t) 24 Bisexual<br />
Maltebrunia 5 Southern Africa (T) Unknown Bisexual<br />
Prosphytochha^ 1 Southern Africa (t) Unknown Bisexual<br />
Potomophila^' 1 Australia (t + T) 24 Unisexual <strong>and</strong><br />
bisexual<br />
Source; Modified from Vaughan (1994).<br />
"T, tropical; t, temperate.<br />
^Tzvelev (19S9) recognizes H ydrochloa as a separate genus within the tribe Oryzeae but this has been<br />
considered to be within the generic limits of Luziola by Duistei'inaat (1987).<br />
'Duistermaat (1987) considers that P rosphytochha <strong>and</strong> M altebrunia are witliin the generic limits of<br />
Potom ophila.
30 Origin ond History<br />
cuisine). Genome studies o f Zizania are being conducted in the United States (Oellce<br />
et ah, 1997).<br />
Leersia is a widely distributed genus in both temperate <strong>and</strong> tropical regions, <strong>and</strong><br />
some species, such as L hex<strong>and</strong>ra, are used for forage (Launert, 1965j Pyrah, 1969).<br />
Potamophila o f Australia has been suggested as a source o f cold tolerance for rice since<br />
it has the same chrom osom e number as Oryza, unlike Zizania (Abedinia et al., 1998).<br />
The tetraploid monospecific genus Porteresia has been crossed with rice (Jena,<br />
1994; Brar et al., 1998). This genus grows in saline waters off the South Asian subcontinent,<br />
thus the intense interest in this genus as a source o f genes to restructure the<br />
rice plant for saline habitats (Flowers et al., 1990).<br />
W ithin the tribe Oryzeae, Leersia is m ost closely related to Oryza. Som e species o f<br />
both genera appear to be intermediate between both genera. For example, Leersia stipitata<br />
o f Thail<strong>and</strong> has some anatomical characteristics that resemble Oryza (Launert,<br />
1965; Pyrah, 1969). Similarly, O. hrachyantha has some features that resemble Leersia<br />
(Launert, 1965), but on balance, it is considered an Oryza species (Tateoka, 1963;<br />
Launert, 1965). O. schlechteri required a scanning electron microscopic survey o f the<br />
spikelet; surface to confirm its position in Oryza, despite having some characteristics,<br />
such as rudimentary sterile lemma, similar to Leersia (Naredo et al., 1993).<br />
The key characteristics o f species in the genus Oryza are (1) bisexual spilcelets;<br />
(2) two m ore-or-less well-developed sterile lemmas; (3) sterile lemmas acuminate,<br />
entire, sometimes setiform; (4) lemma <strong>and</strong> palea o f fertile florets herbaceous to crus-<br />
taceous; <strong>and</strong> (5) leaves herbaceous <strong>and</strong> leaf margins often scabrous (Duistermaat,<br />
1987). Further detailed studies are needed o f the species at the boundary o f Leersia<br />
<strong>and</strong> Oryza genera to better underst<strong>and</strong> their evolutionary relationships.<br />
The species currently <strong>and</strong> widely recognized in the genus <strong>and</strong> their m ost com m on<br />
synonyms, chrom osom e number, <strong>and</strong> genome group are presented (Table 1.2.3). A<br />
key to distinguish species in the genus Oryza can be found in Vaughan (1994). The<br />
major characteristics o f these species, their biosystematic relationships, <strong>and</strong> uses or<br />
potential uses are discussed below.<br />
ORYZA SCHLECHTERI PILGER<br />
The tetraploid species O. schlechteri Pilger is a small stoloniferous plant found in<br />
Papua New Guinea <strong>and</strong> Irian Jaya, Indonesia (Vaughan <strong>and</strong> Sitch, 1991; Vaughan,<br />
1994) (Figure 1.2.1). Among the unusual morphological traits o f O. schlechteri are<br />
pubescent nodes <strong>and</strong> very small stature compared with other Oryza species. Genetically,<br />
it has been demonstrated that the genome is diverged by > 30% from other<br />
genomes in the genus Oryza at the molecular level (Aggarwal et al., 1996c), <strong>and</strong> thus<br />
this species is particularly interesting as a possible source o f new genes. However,<br />
only one accession o f this species is in the world gene bank system at IRRI, <strong>and</strong> this<br />
accession has so far not been induced to flower since it was collected.<br />
ORYZA BRACHYANTHA CHEV. ET ROEHR.<br />
Like O. schlechteri, the diploid African species O. hrachyantha Chev, et Roehr. is on<br />
the boundary o f the genus Oryza <strong>and</strong> is found in the areas denoted in Figure 1.2.2.
Bjosystematics of the Genus Qf/ztl 31<br />
TABLE 1.2.3.<br />
O ryza Species: M ajor Synonymy, Chromosome Number, <strong>and</strong> Genome Group<br />
Section<br />
Com plex<br />
Species<br />
O ther Nom e(s) Com m only<br />
Found in the Literature<br />
C hrom osom e<br />
Num ber<br />
G enom e<br />
Group<br />
Oryza<br />
Oryza sativa complex"<br />
Oryza sativa L. 24 AA<br />
0. rufipogon sensu lacto 0. nivara for the 24 AA<br />
0. glaberrima Steud.<br />
annual form, 0.<br />
rufipogon sensu<br />
stricto for the<br />
perennial form<br />
24 AA<br />
0 . barthii A. Chev. O. breviligulata 24 AA<br />
0, longistaminata Chev. et Roehr. O. barthii 24 AA<br />
0. meridionalis Ng 24 AA<br />
0. glumaepatula Steud.*’ O. rufipogon 24 AA<br />
O, officinalis complex<br />
O. ojficinalis Wall ex Watt*’ 0 . minuta 24 CC<br />
0, minuta J. S. Presl ex C. B. Presl. O, ojficinalis 48 BBCC<br />
O. rhizomatis D. A. Vaughan 24 CC<br />
O. eichingeri Peter'* O. collina for the Sri 24 CC<br />
Lankan form<br />
O. punctata Kotschy ex. Steud. O. schweinjurthiana 24, 48 BB, BBCC<br />
O. latifolia Desv.“ ■48 CCDD<br />
O. alta Swallen" 48 CCDD<br />
O. gr<strong>and</strong>iglumis (Doell.) Prod.“ 48 CCDD<br />
O. australiensis Domin 24 EE<br />
Ridleyanae Tateoka<br />
O. brachyantha Chev. et Roehr. 24<br />
0. schlechteri Pilger 48 Unknown<br />
0. ridleyi complex<br />
O. ridleyi Hook. 48 HHJJ<br />
O. longiglumis Jansen 48 HHJJ<br />
Granulata Roschev.<br />
0. granulata complex^<br />
O, granulata Nees et Arn ex Watt 24 GG<br />
O. meyeriana (2oU. et Mor. ex 24 GG<br />
Steud.) Baill.<br />
Source: Updated <strong>and</strong> revised from Vaughan (1989a).<br />
“Many workers have considered that the annual <strong>and</strong> perennial wild relatives of O. sativa should be considered<br />
separate species. However, crop complexes consisting of perennial, annual wild relative <strong>and</strong> cultigen<br />
have generally been given subspecific ranking (De Wit, 1981). Research results suggest that for rice <strong>and</strong> its<br />
relatives, evolution of annual from perennial forms is a local phenomenon, morphologically intermediate<br />
types are abundant, <strong>and</strong> no major crossing barriers exist between rice <strong>and</strong> its close relatives (Oka, 1988).<br />
*'We refer to Latin American AA genome as O. glum aepatula because of its wide use in the literature despite<br />
the fact that the taxonomy <strong>and</strong> nomenclature of this species is in a state of flux. We recognize that no key<br />
characters have been found to distinguish this species from perennial 0 . rufipogon.<br />
^A tetraploid race, described from southwestern India as a new species, O. m alam puzhaensis, requires<br />
further study to determine its relationship with other tetraploid BBCC genome species.<br />
continued
32 Origin <strong>and</strong> History<br />
TABLE 1.2.3,<br />
(Continued)<br />
'^There has recently been a report of tetraploid O. eichingeri (Lu et al., 1997). This has not been confirmed<br />
<strong>and</strong> at this time is discounted.<br />
'A diploid population of O. latifolia was reported from Paraguay {Brucher, 1977). Subsequently, no seed<br />
material was made available from this population <strong>and</strong> two collecting trips to the locality (Second, 1989;<br />
Morishima et al., 1999) failed to find diploid O. latifolia. This report is thus discounted.<br />
■^Two other species have recently been named within this complex: O. in d<strong>and</strong>am anica EUis, restricted to<br />
Rutl<strong>and</strong> Isl<strong>and</strong>, the Andamans, India, <strong>and</strong> 0. neocaledonica Morat. from the region of Pouembout, New<br />
Caledonia, The former is a diminutive variant of O. granulata <strong>and</strong> the latter was distinguished primarily<br />
based on microscopic epidermal characters. We consider that both probably warrant intraspedfic status<br />
only; however, further studies of these two taxa are warranted.<br />
Features o f the long awn, such as its coriaceous, rigid structure served with a single<br />
vascular bundle, allie this species with Oryza rather than Leersia (Launert, 1965). The<br />
species often grows with O. barthit in small temporary pools, usually in laterite soils.<br />
It has been suggested that during evolution, introgression may have occurred between<br />
African AA genome species <strong>and</strong> O. hrachyantha (FF genome) since the rDNA spacer o f<br />
the two genomes is similar (Cordesse et al., 1992). On the otlier h<strong>and</strong>, Ichikawa et al.<br />
(1986) found large subunits o f fraction 1 protein (Rubisco) o f O. officinalis complex<br />
species <strong>and</strong> 0 . hrachyantha indistinguishable.<br />
Hybrids between O. hrachyantha <strong>and</strong> elite rice Unes have been made successfully<br />
to'incorporate resistance to multiple races of bacterial blight (Brar <strong>and</strong> Khush, 1997).<br />
Backcross progeny <strong>and</strong> m onosom ie alien addition lines have been developed from<br />
these hybrids (Aggarwal et al., 1996b).<br />
O, schlechteri<br />
Figure 1.2.1.<br />
Distribution of 0. schlediteri Pilger,
Biosystemotics of the Genus O ryia 33<br />
ORYZA GRANULATA COMPLEX<br />
The O. granulata complex consists o f two species, O. granulata Nees et Arn. ex Watt<br />
<strong>and</strong> O. meyeriana (Zoll. et Mor. ex Steud.) Baill., with a wide distribution across Asia.<br />
O. granulata is found primarily across continental Asia (Figure 1.2.3), <strong>and</strong> O. meyeriana<br />
is found primarily in insular Asia (Figure 1.2.4). These species are distinguished<br />
by spikelet size; the spikelet o f O. granulata is 6.4 mm.<br />
Botli species look like diminutive bamboos <strong>and</strong> their distinctive habitat is shaded<br />
forest floors. These two species are the only relatives o f rice that are found in upl<strong>and</strong><br />
habitats ratlier than in or near water. Generally, these two species are found in forests<br />
o f hilly or mountainous regions. These two species flower year round <strong>and</strong> have distinctively<br />
dark green leaves <strong>and</strong> nonbranching panicles. Spikelets are awnless, a feature<br />
found in only one other wild Oryza species, O. schlechteri.
' - i<br />
■<br />
^<br />
34<br />
Origin <strong>and</strong> History<br />
! ■<br />
io u r regional variants o f these two species have been reported. A population from<br />
the Andaman isl<strong>and</strong>s, India was described as a new species, O. ind<strong>and</strong>am anica Ellis<br />
(Ellis, 1985; Khush <strong>and</strong> Jena, 1989; Khush et al,, 1990a), We consider this a variant o f<br />
O. granulata.<br />
Based on variation between spikelet surface structures o f Chinese populations<br />
o f O. granulata <strong>and</strong> accessions from other regions, a new subspecies was proposed,<br />
O. meyeriana subsp. tuberculata (Wu et al., 1990). However, since relatively few populations<br />
across Southeast Asia have been studied, we suspect variation to be continuous<br />
for microscopic structures on the spikelet surface.<br />
Populations o f this complex from the M olluca isl<strong>and</strong>s, Indonesia, have long<br />
spikelets. Although this has been described as the species O. abromeitiana, we consider<br />
this type within the range o f variation for O. meyeriana.<br />
A species closely resembling O. meyeriana was described from New Caledonia,<br />
O. neocaledonka M orat (M orat et al., 1994). O. neodadedonica is distinguished from<br />
O, meyeriana based on microscopic epidermal characteristics but was not compared<br />
to O. granulata. We believe that the status o f this species requires further study <strong>and</strong><br />
may warrant only intraspecific status. The species is found very far from other populations<br />
o f O, granulata complex taxa. The nearest known location to New Caledonia<br />
at which O. granulata complex taxa grow is on the M olucca isl<strong>and</strong>s, Indonesia. Thus<br />
O. granulata complex taxa may be present on New Guinea <strong>and</strong> other isl<strong>and</strong>s that lie<br />
between New Caledonia <strong>and</strong> the M olucca isl<strong>and</strong>s.<br />
Hybrids between O, granulata (GG genome) <strong>and</strong> rice (AA genome) are very<br />
difficult to obtain but have been made successfully, <strong>and</strong> backcross progeny have been<br />
derived from these hybrids (Aggarwal et al., 1996b; Brar <strong>and</strong> Khush, 1997).
Biosystematks of Ihe Genus O rym 35<br />
0. meyerianB<br />
Figure 1.2.4.<br />
Distribution of 0. m e y e m Q {Zoll, et Mor. ex Steud.) Baill.<br />
ORYZA RIDLBYI COMPLEX<br />
The O. ridleyi complex consists o f two allopolyploid species, O. ridleyi Hook, <strong>and</strong><br />
O, longiglutnis Jansen. O. ridleyi is found in continental Southeast Asia <strong>and</strong> across the<br />
Malay archipelago to New Guinea (Figure 1.2.5), while O. longiglutnis is restricted<br />
to New Guinea (Figure 1.2.6). Both species com e from similar habitats, shaded seasonally<br />
inundated forest floors. Generally, populations o f these two species grow very<br />
close to rivers. The habit o f these species is very similar, being erect or semierect with<br />
dark green leaves <strong>and</strong> panicles with erect branching. These two species differ primarily<br />
in the length o f the sterile lemma <strong>and</strong> awn, both o f which are shorter in O. ridleyi.<br />
O. ridleyi has long been o f interest to plant breeders as a possible source o f stem<br />
borer resistance (Van <strong>and</strong> Guan, 1959; Heinrichs et al., 1985). However, since this<br />
species is tetraploid <strong>and</strong> has highly divergent genomes (H H JJ genome) from rice (AA),<br />
no introgression has been detected in hybrids produced between these two species<br />
(Aggarwal et al., 1997; Brar <strong>and</strong> Khush, 1997).<br />
ORYZA OFFICINALIS COMPLEX<br />
Oryza officinalis Wall ex Watt<br />
O. officinalis is a diploid, CC genome species <strong>and</strong> is distributed widely across Asia<br />
from India <strong>and</strong> southern China to New Guinea (Figure 1.2.7). Reports o f this species<br />
occurring in northern Australia need confirmation. This species grows in a wide
36 Origin ond History<br />
O. rid le y i<br />
Figure 1.2.5.<br />
Distribution of 0, ridleyi Hook.<br />
O, tongiglumis<br />
Figure 1.2.6. Distribution of 0. hngigiumis Im m .<br />
variety o f habitats, from open grassl<strong>and</strong> to shaded woodl<strong>and</strong>, <strong>and</strong> from seasonally<br />
dry to permanently wet. The growth habit o f this species also varies, probably due<br />
to environmental factors, from herbaceous clumps to very tall (>3 m ), widely spaced<br />
plants. O. officinalis has been described as a species with weedy characteristics (Oka,
k<br />
Biosystemafits of the Genus Oryza 3 7<br />
0 , o ff ic in a lis<br />
? unconfirmed reports<br />
Figure 1.2.7.<br />
Distribution 6f 0. offkm iis Wall ex Walt.<br />
1988). Second (1991b) has reported that it occurs occasionally as a weed in newly<br />
established rice fields in the Philippines.<br />
O. officinalis is distinguished by generally having small rhizomes <strong>and</strong> a whorl o f<br />
basal panicle branches. Earlier workers reported little intrapopulation morphological<br />
variation (Hu <strong>and</strong> Chang, 1967), however, Chinese populations have larger spikelets<br />
than those o f South <strong>and</strong> Southeast Asia. On the other h<strong>and</strong>, intrapopulation sterility<br />
barriers are high in O. officinalis between populations from different countries (Hu<br />
<strong>and</strong> Chang, 1967). New germplasra from both China <strong>and</strong> New Guinea is available<br />
now <strong>and</strong> further study o f the ecogenetic variation in this species is warranted.<br />
O. officinalis has been used as a source o f brown plant hopper resistance <strong>and</strong><br />
used successfully in breeding new cultivars (Jena <strong>and</strong> Khush, 1990; Jena et al., 1992).<br />
Three cultivars with genes for brown plant hopper resistance from a Thai population<br />
of O. officinalis have been released in Vietnam (Vaughan <strong>and</strong> Sitch, 1991; Brar <strong>and</strong><br />
Khush, 1997). O. officinalis has been shown to have resistance to rice pathogens such<br />
as bacterial blight <strong>and</strong> blast (Katsuya, 1973; Brar <strong>and</strong> Khush, 1997) <strong>and</strong> contain an<br />
antifungal compormd, jasm onic acid, a methyl ester (Neto et al., 1991).<br />
Otyza eichittgeri Peter<br />
O. eichingeri, a diploid, CC genome species o f shaded habitats, has an unusual disjunct<br />
distribution in West <strong>and</strong> East Africa <strong>and</strong> Sri Lanka (Figure 1.2.8), Tateoka (1962a,b;<br />
1965a,b) analyzed this species <strong>and</strong> clarified its differences with O, punctata in Africa.<br />
Vaughan (1989b, 1990a) determined the characteristics with which tliis species can<br />
be distinguished from O. rhizomatis in Sri Lanka. The distribution may help explain
38 Origin <strong>and</strong> History<br />
(a) Africa<br />
(b) Sri Lanka<br />
O .eich 'm g eri \<br />
Figure 1.2.8.<br />
Distribution of 0. ekhingeri Peter.<br />
genetic heterogeneity that has been found in this species; for example, three cpDNA<br />
plastotypes have been found in African accessions o f O. ekhingeri (Dally <strong>and</strong> Second,<br />
1990). Despite morphological variation such as compact <strong>and</strong> spreading panicles, <strong>and</strong><br />
short <strong>and</strong> tall forms, most features, particularly those o f the spilcelet, a taxonomically<br />
conservative structure, clearly align widely separated populations as one species. The<br />
key characters o f O. ekhingeri are its flexuous awn, short <strong>and</strong> nonsplit ligule, <strong>and</strong><br />
spilcelet size.<br />
In com m on with O. punctata (BB genome) <strong>and</strong> O. officinalis (CC genome),<br />
O. ekhingeri has three rDNA loci. However, one o f these loci is much wealcer in<br />
O. ekhingeri than in other species o f the O. officinalis complex (Bukui et ah, 1994;<br />
Shishido et ah, 1996).<br />
Oryza rhizomatis D. A. Vaughan<br />
O. rhizomatis is a diploid, CC genome species distributed in open grassl<strong>and</strong> habitats<br />
in the dry zone o f Sri Lanka (Figure 1.2.9). O. rhizomatis grows in habitats that may be
Biosystematics of the Genus Oryza 39<br />
............ / ..<br />
•i;-<br />
h-.A / > ... 1<br />
i<br />
i f , ^...<br />
i<br />
C<br />
I \ \ '...<br />
u<br />
i1<br />
i<br />
\\.A\<br />
/<br />
, t ; ( ..'.(V.....<br />
O. rhSzomatis<br />
Figure 1.2.9.<br />
Distributioii of 0. f/iizomGfe Vaughan.<br />
seasonally wet, but rhizomes enable this species to survive the dry season. The panicle<br />
o f O. rhizomatis frequently has purple pigmentation, <strong>and</strong> like O. eichingeri, the basal<br />
panicle branches are not in a whorl. M ost other morphological characteristics <strong>and</strong><br />
the habitat o f O. rhizomatis shows greater similarity to O. o^cinalis than O. eichingeri.<br />
DNA polymorphism based on RAPD analysis also supports a closer relationship<br />
between O. rhizomatis <strong>and</strong> O. officinalis than to O. eichingeri (Aggarwal et al., 1996a).<br />
O. rhizomatis was found to differ from all other members o f the O. officinalis<br />
complex in its chloroplast DNAplastotype. The accession studied (National Institute<br />
o f Genetics, Japan W 1805) had one restriction site that it shared with O. hrachyaniha<br />
<strong>and</strong> O. meyeriana (Dally <strong>and</strong> Second, 1990).<br />
Qtyia mimfu J. S. PresL ex C. B. Presl.<br />
O. minuta, a tetraploid species (BBCC), has been found only in the Philippines <strong>and</strong><br />
Papua New Guinea (Figure 1.2.10). It grows in semishade, usually beside ponds or<br />
streams. It was only after collecting both O, officinalis <strong>and</strong> O. minuta in the Philippines<br />
<strong>and</strong> subsequent morphological <strong>and</strong> cytological studies that the traits of these two<br />
species were clarified (Tateoka <strong>and</strong> Pancho, 1963). O. minuta has a small panicle <strong>and</strong><br />
the smallest spilcelets o f the species in the O. officinalis complex: hence its name—<br />
minuta. It is also distinguished from O. officinalis by having only one or two branches<br />
from the lowest panicle node. Despite being a tetraploid, O. minuta has been crossed
Origin <strong>and</strong> History<br />
0 . m i n u t a ^ \ ^<br />
F igure 1,2.10.<br />
Distribution of 0. minutai. S. Presl, exC. B. Presl.<br />
to rice, <strong>and</strong> several useful traits, such as blast <strong>and</strong> bacterial blight resistance, have been<br />
transferred (Sitch, 1990; Amante-Bordeos et al., 1992).<br />
The <strong>origin</strong> o f O, minuta is intriguing because it has the BB genome for which<br />
the only diploid species is found in Africa, The relationship between O. minuta <strong>and</strong><br />
O. punctata (BB genome) is supported by similar deletions in the chloroplast DNA<br />
(Kanno <strong>and</strong> Hirai, 1992). However, five families o f repetitive DNA from the genomes<br />
o f 0 . minuta <strong>and</strong> O. australiensis (EE genome) have been reported (Aswidinnoor<br />
et a l, 1991), <strong>and</strong> three o f these families cross-hybridize with both O. minuta <strong>and</strong> O.<br />
australiensis. This suggests that perhaps the BB genomes o f O. minuta have similarities<br />
to the EE genome o f O. australiensis.<br />
Oryza punctata Kotschy ex Sfeud.<br />
The taxonomy o f O. punctata was clarified by Tateoka (1965a,b), based on herbarium<br />
studies <strong>and</strong> analysis o f germplasm collected directly during a visit to East Africa<br />
<strong>and</strong> Madagascar in 1964 (Tateoka, 1964) (Figure 1.2.11). Particularly, Tateoka distinguished<br />
O. punctata from the closely related species O. eichingeri based primarily<br />
on spikelet size, ligule <strong>and</strong> culm characteristics. Tateoka (1962a, 1965a) suggested<br />
that O. punctata <strong>and</strong> O. eichingeri may form natural hybrids since several herbarium<br />
<strong>and</strong> gene bank accessions appeared to be intermediate in nature. The ecological <strong>and</strong><br />
population dynamics o f the 0 . punctata chromosom e races <strong>and</strong> O. eichingeri require
Biosystematics of the Genus Oryzg 41<br />
0, punctata \<br />
T Diploid race<br />
■ Tetraploid race<br />
Figure 1.2.11.<br />
Distribution of 0. puncMo Kotschy ex Steud.<br />
investigating before some o f the critical issues related to the evolution o f African<br />
representatives o f the O. ojfidnalis complex are resolved.<br />
Tateoka (1963) describes O. schwienfurthiana Prod, as a synonym o f O. punctata<br />
<strong>and</strong> considered the tetraploid form very close to the type specimen o f O. punctata<br />
(Tateoka, 1962a). However, the description by Roschevicz (1931) o f O. schweinfurthiana<br />
is close to the tetraploid, <strong>and</strong> O. punctata is close to the diploid. Using gene bank<br />
material as well as that collected directly in West Africa, Sano (1980) found discrete<br />
differences between the diploid <strong>and</strong> tetraploid form s o f O. punctata in morphological<br />
<strong>and</strong> ecological traits. Among the ecological traits, shade tolerance was found to be<br />
high in the tetraploid form o f O. punctata (Sasahara et al., 1982). Comparative studies<br />
o f the structure o f chloroplast DNA identified different types o f deletions in the<br />
diploid <strong>and</strong> tetraploid O. punctata accessions. Two diploid accessions analyzed from<br />
East Africa had typical punctata deletion, while the tetraploid accession from Nigeria<br />
had typical oßcm aU s deletion (Kanno <strong>and</strong> Hirai, 1992). These results suggest that<br />
further taxonom ic studies are required o f carefully identified germplasm to determine<br />
whether the two chrom osom e races o f O. punctata warrant specific ranking.<br />
A m ajor issue related to O. punctata <strong>and</strong> any taxonom ic revision concerns the fact<br />
that in parts o f Africa, O. punctata (probably the diploid race only) can be a serious<br />
weed o f rice. Due to the weedy nature o f O. punctata> it has been designated a noxious<br />
weed by the U.S. quarantine service.
42 Origin <strong>and</strong> History<br />
Although O. punctata has not been used in breeding programs, there has been<br />
considerable effort to produce aneuploids o f rice with chromosomes from O, punctata<br />
(BB) (YasuietaL, 1992,1994; Yasui <strong>and</strong> Iwata, 1996). Cytological investigation o f gene<br />
location in O. punctata has been conducted using fluorescence in situ hybridization<br />
(FISH) (Fukui et a l, 1994). This has identified three rDNA loci on different chrom o<br />
somes in O. punctata. A similar num ber were found in O. ojJicinaUs (GC genome) <strong>and</strong><br />
O. eichingeri (CC genome) from Africa.<br />
Ofyzo ausfraliensis Domin<br />
O. australiensis is a diploid, EE genome species o f tropical Australia (Figure 1.2.12)<br />
<strong>and</strong> is highly variable. It is reported to be both annual (without rhizomes) <strong>and</strong> perennial<br />
(with rhizom es). It occurs in a wide range o f habitats, from open to relatively<br />
shaded woodl<strong>and</strong>s, from dry habitats to swamps <strong>and</strong> lagoon edges. It generally produces<br />
abundant seeds. The ecological amplitude o f this species is similar to that<br />
found in the dose relative o f rice, 0 , rufipogon sensu lacto; however, Second (1987)<br />
reports that O. australiensis is found in drier habitats than AA genome wild species<br />
in Australia.<br />
Morphologically, this species is recognized readily by its pear-shaped spikelets.<br />
Several unique features o f O, australiensis may reflect its long isolation from other<br />
species o f the O. officinalis complex (Second, 1991a). Among these is the extraordinary<br />
number o f copies o f the retrotransposon RIREl (<strong>Rice</strong> Retroelement 1), first<br />
described from O. australiensis but found in many other Graminae (Nakajima et al.,<br />
1996; Noma et a l, 1997). O. australiensis has a haploid genome size twice that of<br />
domesticated rice, <strong>and</strong> this may reflect the num ber o f copies o f the LTR (long term i<br />
nal repeats) sequence o f RIREl, estimated to be 7500 copies (M artinez et al., 1994;<br />
Naliajima et al., 1996; Uozu et ah, 1997). In addition, O. australiensis has chloroplast<br />
DNA <strong>and</strong> a large subunit o f fraction 1 protein (Rubisco) that differs from all other<br />
Oryza species (Ichikawa et al., 1986).<br />
The distinct <strong>and</strong> separate evolution of O. australiensis also is reflected in analysis<br />
o f chloroplast plastotype diversity in the genus Oryza, which shows that this species<br />
is isolated genetically from other species (Dally <strong>and</strong> Second, 1990).
Biosystematicsof the Genus Oryza 43<br />
O. australiensis has been successfully crossed to rice <strong>and</strong> backcrossed progeny<br />
had both recessive <strong>and</strong> dom inant genes for brown plant hopper resistance <strong>and</strong> six<br />
races o f bacterial blight resistance (Multani et al., 1994). The suggested potential o f<br />
O. australknsis as a source o f resistance to drought has yet to be explored (Lu, 1996).<br />
CCDD Genome Species Complex in Latin America<br />
Three species, all having the CCDD genome, are recognised in Latin America: O. latifolia<br />
Desv., O. alta Swallen, <strong>and</strong> O. gr<strong>and</strong>iglumis (Doell.) Prod. These three species<br />
belong to the O. officinalis complex, <strong>and</strong> clear genetic differences between them have<br />
been demonstrated by total genomic DNA hybridization <strong>and</strong> RFLP analysis, albeit<br />
with a very limited num ber o f accessions (Aggarwal et al., 1996a). Chromosomes<br />
belonging to the DD genome have been distinguished from those of the CC genome<br />
(Fukui et al„ 1997). O. gr<strong>and</strong>iglumis is readily distinguished from O. latifolia <strong>and</strong><br />
O. alta by its large sterile lemma, which is approximately equal in length or longer<br />
than tlie palea <strong>and</strong> lemma. However, recent new collections <strong>and</strong> research indicate<br />
that O. latifolia <strong>and</strong> O. alta cannot consistently be distinguished based on the key<br />
characters that have long been used to distinguish them: spikelet length <strong>and</strong> leaf<br />
width {Chen <strong>and</strong> Matsunaka, 1991; M orishima et al., 1999). M ore comprehensive<br />
germplasm o f these two species needs to be collected <strong>and</strong> studied, particularly from<br />
the lower Amazon <strong>and</strong> Equador, to clarify their taxonom ic status.<br />
Oryza fotifoUa dm<br />
O. latifolia is the m ost widely distributed o f the three tetraploid Oryza species in Latin<br />
America, being found from Mexico to Argentina (Figure 1.2.13). However, it has<br />
not been collected frequently in the Amazon basin. This species appears to consist<br />
o f at least two types, an ecotype o f small stature from Central America <strong>and</strong> a large<br />
stature ecotype from South America (Second, 1989). RFLP analysis o f O. latifolia<br />
tended to distinguish between Central <strong>and</strong> South American accessions of O. latifolia<br />
(Jena <strong>and</strong> Kochert, 1991). Introgression o f genes for resistance to brown plant hopper,<br />
white-backed plant hopper, <strong>and</strong> bacterial blight from O. latifolia to O. sativa has been<br />
reported (Brar <strong>and</strong> Khush, 1997).<br />
Oryza gr<strong>and</strong>iglumis (Doell.) Prod.<br />
Recently, collection missions to Brazil have clarified the distribution <strong>and</strong> ecology<br />
o f O. gr<strong>and</strong>iglumis (Doell.) Prod. (M orishima <strong>and</strong> M artins, 1994). This species is<br />
distributed widely along the Rio Solimoes <strong>and</strong> adjacent areas in the western Amazon<br />
(Figure 1.2.14). O. gr<strong>and</strong>iglumis is a species that grows in deep water <strong>and</strong> has a<br />
remarkable ability to elongate internodes in rising floodwaters.<br />
Oryza rdta Swallen<br />
O. alta generally is reported to occur at the margins o f ponds <strong>and</strong> lakes rather than<br />
rivers (Oliveira in M orishim a <strong>and</strong> Martins, 1994), <strong>and</strong> in savannah rather than woodl<strong>and</strong><br />
habitats (Vaughan, 1994). It is closely related to O. gr<strong>and</strong>iglumis <strong>and</strong> one population<br />
has been reported to have characteristics o f both O. alta <strong>and</strong> O, gr<strong>and</strong>iglumis
Origiii <strong>and</strong> History<br />
O, latifolia<br />
Figure 1.2.13.<br />
Distribution of 0. latifolio Desv.<br />
(M orishima <strong>and</strong> Martins, 1994). O f the three Latin American CCDD genome species,<br />
this species has the largest spikelet size <strong>and</strong> widest leaves. However, both inter- <strong>and</strong><br />
intrapopulation studies indicate that these characters show continuous variation with<br />
O. latifolia (Chen <strong>and</strong> Matsunaka, 1991; Morishima et al., 1999). Consequently, identification<br />
o f specimens based on these characters alone may he erroneous, which<br />
may explain the rather disjunct distribution o f O. alta outside the Amazon basin<br />
(Figure 1.2.15).<br />
ORYZA SATIVA COMPLEX<br />
Hybrids among AA genome species are possible without much difficulty. Thus AA<br />
genome wild species have been used in rice breeding more than the other wild species<br />
(Table 1.2.4). However, from a taxonom ic perspective, this group o f pantropical<br />
species is particularly problematic because, except for the African species, they lack<br />
clear morphological distinguishing characteristics. Based on morphological characters<br />
alone, it is not possible to consistently <strong>and</strong> reliably identify wild species o f this
Biosystematics of the Genus Oryza 45<br />
complex from Asia, Australia, <strong>and</strong> Latin America. The introduction, in historic times,<br />
of AA genome wild species from one region to another probably has occurred, but its<br />
extent is not clear. For example, tlie African AA genome species O. longistaminata was<br />
collected as a herbarium specimen on the Caribbean isl<strong>and</strong> o f M artinique (Vaughan,<br />
1994). The nom enclature o f the species with the AA genome used by different authors<br />
is shown in Table 1.2.5.<br />
Although an array o f isolating mechanisms have been reported among AA genom<br />
e species, the m ost com monly found isolating mechanism is Fi pollen sterility.<br />
However, this does not prevent gene exchange between isolated populations that are<br />
brought into contact (Chu et al., 1969). There are well-documented cases o f naturally<br />
occurring hybrids between O. sativa <strong>and</strong> O. longistaminata in Africa <strong>and</strong> 0 . sativa <strong>and</strong><br />
O. glumaepatula in Cuba (Chu <strong>and</strong> Oka, 1970; Ghesquiere, 1986).<br />
Despite the wealth o f liter ature on the diversity o f AA genome species, none have<br />
been comprehensive, for the following reasons: (1) there are regions where collecting<br />
has yet to be done, such as the lower Amazon <strong>and</strong> M am beram o river system, Irian Jaya,<br />
Indonesia; (2) germplasm collected, such as that from the Sepik River o f northern<br />
Papua New Guinea, often does not set seeds in sufficient quantities to perm it use in<br />
experimentation; <strong>and</strong> (3) bias is introduced when germplasm is taken directly from<br />
a gene bank collection ratlier than from field-collected material because germplasm<br />
obtained from a gene bank has moderate to abundant seed set. Vast st<strong>and</strong>s o f O, rufipogon<br />
exist in Sumatra, but they are very shy seeders under experimental conditions<br />
<strong>and</strong> thus multiplied seeds generally are not represented in diversity experiments. Thus<br />
literature that has used first-generation germplasm from seeds collected directly in the<br />
field has been given weight in the following sections.<br />
AA genome Oryza species have been recognised based primarily on geographic<br />
differentiation. Indeed, the location that wild rice comes from seems to have become
46 Origin <strong>and</strong> History<br />
0 . a lt a i<br />
Fig u re 1.2,15.<br />
Distribution of 0. alta Swollen.<br />
the primary determinant for applying species names to some AA genome wild species<br />
(Juliano et al., 1998), W ithin each region, various ecological factors, but primarily<br />
the hydrological regime, have lead to varying degrees o f both regional <strong>and</strong> local differentiation.<br />
We discuss AA genome wild species o f each geographic region where<br />
they occur.<br />
Asia<br />
Taxonomy<br />
To underst<strong>and</strong> the confusion regarding taxonomy o f the close relatives of rice (O. sativa<br />
L.) in Asia, two evolutionary genetic points are pertinent.<br />
1. Based on the gene pool system o f Harlan <strong>and</strong> De W it (1971), rice <strong>and</strong> its close<br />
relatives with the AA genome in Asia constitute the primary gene pool o f rice.<br />
Although partial F] sterility can occur between populations within this gene<br />
pool, it does not prevent gene flow (M orishim a et al., 1992).<br />
2, Two evolutionary trends are discernible in the close wild relatives o f rice:<br />
(a) Geographic isolation that has led to marked genetic differentiation (Second,<br />
1985; Cai et al., 1995, 1996; Akimoto, 1999).<br />
(b) Ecological adaptation that has lead to life cycle <strong>and</strong> breeding system differentiation<br />
(M orishima et al., 1992). Ecological adaptation can occur
Biosystemati($ of the Genus Oryza 47<br />
TABIE1.2.4.<br />
Uses Made of AA Genome Wild Species<br />
O. sativa f. spontanea (weedy plant) was used in China in the 1920s to develop Yatsen-1,<br />
which had tolerance to low temperatures <strong>and</strong> acid soils (Chang, 1985),<br />
O, rufipogon subsp. nivara from India provided the vsole source of resistance to grassy stunt<br />
virus (Chang et al., 1975).<br />
0. sativa f. spontanea has provided the most useful sources of cytoplasmic male sterility in<br />
hybrid rice <strong>production</strong> (Lin <strong>and</strong> Yuan, 1980).<br />
O, rufipogon subsp. rufipogon from Thail<strong>and</strong> has been found to have a high level of resistance<br />
to both tungro viruses (Ikeda et al., 1994).<br />
O. longistaminata has been a source of bacterial blight resistance (Xa-21) (Khush et al.,<br />
1990b).<br />
O. glumaepatula has been a new source of cytoplasmic male sterility (Dalmacio et al, 1996),<br />
regionally or over very restricted areas, such as a single pond. This can<br />
result in distinctive phenotypes associated with annual versus perennial<br />
life cycles <strong>and</strong> inbreeding versus outcrossing reproductive systems. However,<br />
ecological adaptation in rice <strong>and</strong> its close relatives in Asia, perhaps<br />
due to lack o f barriers to gene flow, has not resulted in the same extent<br />
o f genetic differentiation as that seen with geographic isolation. Recent<br />
intensive studies have demonstrated a tendency for differential distribution<br />
o f isozyme <strong>and</strong> RFLP genotypes (Akimoto, 1999) <strong>and</strong> the presence<br />
or absence o f a transposable element (Kanazawa et al., 2000) between<br />
ecotypes o f AA genome wild rice in Asia. However, direct sequencing o f<br />
particular genes has not revealed differences between different ecotypes<br />
(Barbier et a l, 1991; Morishima, 1998).<br />
These com ments may help explain why various rice workers have disagreed on<br />
the nomenclature o f rice <strong>and</strong> its close relatives. Accurate nomenclature, however,<br />
is an im portant issue, since com m on underst<strong>and</strong>ing <strong>and</strong> interpretation o f research<br />
results depend on germplasm being identified accurately. Wild rice populations are<br />
frequently heterogeneous with respect to annual <strong>and</strong> perennial <strong>and</strong>/or inbreeding<br />
<strong>and</strong> outcrossing types. In addition, intermediate plants <strong>and</strong> populations have been<br />
identified (Sano et a l, 1980). Thus, while morphological characters can be used to<br />
distinguish extremes in the annual/perennial spectrum, these characters are continuous,<br />
based on broadly based studies o f freshly collected germplasm (M orishim a<br />
et al., 1992). Consequently, we suggest that the close wild AA genome relatives o f<br />
rice are recognized as O. rufipogon sensu lacto. W hen populations or individuals can<br />
be identified clearly as wild <strong>and</strong> annual, we suggest that they be called O. rufipogon<br />
subsp. nivara. W lien accessions can be identified accurately as wild <strong>and</strong> perennial,<br />
we propose that they be called O. rufipogon subsp. rufipogon. There are, in addition,<br />
sufficient differences between the indica <strong>and</strong> japónica cultivai's o f O. sativa for these<br />
two cultivar groups to be recognized as distinct subspecies O. sativa subsp. indica <strong>and</strong><br />
O. sativa suhsp. japónica (Second, 1991a; M orishima et al., 1992).<br />
Weedy rices form a different problem because the word weed has varying in <br />
terpretations. The nom enclature o f weedy rices is discussed in a later section o f tliis<br />
chapter.
Biosystematics of the Genus Oryza 49<br />
Thus we can consider the primary gene pool of rice in Asia as follows:<br />
Cultivated<br />
Wild<br />
O. sativa sensu lacto<br />
subsp. indica<br />
subsp. japónica<br />
O, rufipogon sensu lacto<br />
subsp. nivara<br />
subsp. rufipogon<br />
We believe that this nomenclature most accurately reflects the primary gene pool<br />
o f Asian cultivated rice <strong>and</strong> should enable rice workers to determine the level o f<br />
nomenclatura! accuracy that is possible <strong>and</strong> appropriate for their work.<br />
Evolution<br />
The most obvious evolutionary trend that can be seen in Asian wild rice is the trend<br />
towards perennial <strong>and</strong> annual types (Figure 1.2.16). This trend is reflected by generally<br />
continuous variation for life <strong>history</strong> traits, mating system, <strong>and</strong> habitat preferences.<br />
Oryza rufipogon subsp. rufipogon. This subspecies is distributed widely in m onsoon<br />
Asia. Geographical variation exists between Chinese <strong>and</strong> South <strong>and</strong> Soutlieast Asian<br />
populations. This subspecies inhabits deep water that is not subject to great disturbance.<br />
Coexisting species are mainly perennial. Outcrossing is high: estimated to be 30<br />
O. rufipogon sensu lacto ..... .......<br />
........ \<br />
........ . limits of distribution of 0, ru^pogon subsp. rufipogon<br />
~ - limits of distribution of O, rufipogon subsp. nivara iX<br />
Figure 1.2.16.<br />
Distribution of 0. lufipogon sensu lacto.
50 Origin <strong>and</strong> History<br />
to 50% (Oka <strong>and</strong> Morishima, 1967) <strong>and</strong> 51 to 56% (Barbier, 1989). Seed productivity<br />
is low, but regeneration ability is high; reproductive allocation is between 0 <strong>and</strong> 20% .<br />
Stature is tall <strong>and</strong> plants generally are late flowering, reflecting long basic vegetative<br />
phase <strong>and</strong>/or photoperiod sensitivity.<br />
This subspecies has higher gene diversity, a larger number o f polymorphic loci,<br />
<strong>and</strong> a higher average number o f aUeles per locus than the annual subspecies nivara.<br />
Populations consist o f a high frequency o f heterozygotes <strong>and</strong> the fixation index is<br />
low. Although this ecotype propagates mainly asexuaUy, they can produce various<br />
segregants by seed propagation, particularly when their habitats are disturbed. This<br />
confers a high evolutionary potential to this subspecies (M orishim a et al., 1992). This<br />
subspecies has higher resistance to various races o f bacterial leaf blight than that o f<br />
the annual subspecies (Ikeda et al., 1990; Morishima, 1994),<br />
Oryza rufipogon subsp. nivara. This subspecies is found in tropical areas o f continental<br />
Asia that are very dry in the dry season. Typically, habitats include the edge o f<br />
seasonally dry ponds <strong>and</strong> swamps. These habitats can be subject to a high degree of<br />
disturbance by humans or animals. Coexisting flora are generally composed of annual<br />
species. Outcrossing has been estimated to be between 5 <strong>and</strong> 20% (M orishim a et al.,<br />
1984) <strong>and</strong> 5% (Barbier, 1989). Seed <strong>production</strong> <strong>and</strong> dispersal is high <strong>and</strong> seeds have<br />
pronounced seed dormancy. Reproductive allocation is between 40 <strong>and</strong> 60% . Stature<br />
is short <strong>and</strong> flowering is early, indicative o f photoperiod insensitivity. This subspecies<br />
has high tolerance to both submergence <strong>and</strong> drought. Compared to the subspecies rwfipogon,<br />
this subspecies has a lower gene diversity index, fewer polymorphic loci, <strong>and</strong><br />
a higher average number o f alleles per locus. Homozygotes are more frequent <strong>and</strong> the<br />
fixation index is higher than that o f the perennial subspecies (M orishima et al., 1992).<br />
Africa<br />
In contrast to the AA genome species o f other regions, the wild African AA genome<br />
species (Figure 1.2.17) can be identifiedreadilybyclearkey characters with no continuum<br />
o f forms between them. The perennial species O. longistaminata is the only AA<br />
species with well-developed rhizomes. O. barthii <strong>and</strong> the African cultigen O. glaberrima<br />
are the only AA genome species with short, rounded ligules. All other AA<br />
genome species have pointed bifurate ligules o f variable length.<br />
Oryza fongistaminaia Chev. et Roehr.<br />
O. longistaminata Chev, et Roehr. is widely distributed across Africa (Figure 1,2.17).<br />
Several ecological types based on habitat <strong>and</strong> breeding system has been recognised<br />
(Ghesquiere, 1986):<br />
1. Isolated populations occurring in regularly flooded plains; moderately selfincompatible<br />
2. Populations o f temporary pools often sympatric with 0 . barthii^ highly selfincompatible<br />
3. In areas o f cultivation but not a weed, exhibiting self-compatibility <strong>and</strong> selfincompatibility
Biosystematics of the Genus Oryza 51<br />
Figure 1.2.17.<br />
Distribution of 0. barthii A. Cbev. <strong>and</strong> 0. longistaminata Chev. et Roefir.<br />
4. Weedy in cultivated fields, exhibiting self-compatibility <strong>and</strong> self-incompatibility<br />
5. Weedy in cultivated fields or recently fallow areas; complete self-incompatibility<br />
absent<br />
Among AA genome species, O, longistaminata shows a high level o f withinpopulation<br />
variation (Oka, 1988). Analysis ofthe nucleotide sequence o f the p-SINEl-<br />
like intron o f the CatA catalase hom olog has suggested that the AA genome may have<br />
<strong>origin</strong>ated from an ancestor o f O. longistaminata in Africa (Iwamoto et al., 1999).<br />
Although O. barthii <strong>and</strong> O, longistaminata are frequently sympatric, isolating<br />
barriers are apparently strong <strong>and</strong> hybrid populations have not been confirmed (Morishima<br />
et al., 1992). However, natural weedy hybrid populations between O. longistaminata<br />
<strong>and</strong> O. sativa have been analyzed (Chu <strong>and</strong> Oka, 1970; Ghesquiere, 1986;<br />
Causse <strong>and</strong> Ghesquiere, 1991).
52 Origin <strong>and</strong> History<br />
Oryza bartkH A. Chev.<br />
O. barthii <strong>and</strong> African cultivated rice, O. glaherrima (Figure 1.2.17), are closely related<br />
<strong>and</strong> exhibit a strongly annual life cycle. O. harthii is photoperiod sensitive, whereas<br />
O. glaherrima occasionahy can be photoperiod insensitive. O. harthii typically occurs<br />
in seasonally dry pools, has a short stature, <strong>and</strong> large spikelets with a long strong awn<br />
(Bardenas <strong>and</strong> Chang, 1966). It can also occur in deep water <strong>and</strong> shows a floating<br />
habit. Among AA genome wild taxa, O. barthii has narrow genetic variation that<br />
may reflect its annual <strong>and</strong> predominantly inbreeding nature. Outcrossing has been<br />
estimated at between 5 <strong>and</strong> 20% (O ka <strong>and</strong> M orishima, 1967).<br />
Australia <strong>and</strong> New Guinea<br />
In Australia <strong>and</strong> New Guinea, two broad groups o f AA genome wild rice have been<br />
reported. One has been called the Oceanian type (M orishima, 1969), <strong>and</strong> the other<br />
is similar to Asian AA genome wild rice (Ng et al., 1981a <strong>and</strong> b ). In this region, there<br />
is some evidence that both types have evolved annual <strong>and</strong> perennial form s (Second,<br />
1987; Lu, 1996). Two forms o f annual wild rice have been reported in Australia <strong>and</strong><br />
New Guinea (Lu, 1996). One type is tail <strong>and</strong> has open panicles <strong>and</strong> small slender<br />
spikelets corresponding to the Oceanian annual type (O. meridionalis). The other<br />
form is short <strong>and</strong> has large, broad spikelets typical o f the Asian annual type <strong>and</strong> thus<br />
may be O. rufipogon subsp. nivara. Perennial Oceanian AA genome wild rice has been<br />
reported from southern New Guinea (M orishima, 1969) <strong>and</strong> northern New Guinea<br />
(Doi et al., 1995). Second (1987) indicated the Asian AA genome perennial type o f<br />
wild rice ( O. rufipogon subsp. rufipogon) may grow in Australia.<br />
Oryza meridionalis Ng<br />
Oryza meridionalis (Figure 1.2.18) has strong reproductive isolation from all other AA<br />
genome species. Diversity studies based on isozymes <strong>and</strong> nuclear DNA RFLP generally<br />
demonstrated tliat O. meridionalis is remotely related to other AA genome species<br />
(Second, 1985; D oi et a l, 1995; Aldmoto, 1999). Studies of ribosom al DNA (Sano<br />
<strong>and</strong> Sano, 1990), m itochondrial DNA (Aldmoto, 1999), <strong>and</strong> RAPD analysis based on<br />
nuclear DNA (Ishii et a l, 1996) have provided results suggesting that O. meridionalis<br />
may be similar to annual <strong>and</strong>/or perennial African, some South American accessions,<br />
<strong>and</strong>/or Oceanian perennial AA genome wild rices. A clear underst<strong>and</strong>ing o f tlie diversity<br />
<strong>and</strong> relationship of this species with other AA genome species is lacking.<br />
Oryza rufipogon sensu lacto<br />
O, rufipogon from Australia <strong>and</strong> New Guinea produces fertile hybrids with Asian<br />
accessions o f O. rufipogon (M orishima, 1969). This taxon produced fertile hybrids<br />
with Asian accessions o f 0 . rufipogon (M orishima, 1969). However, two accessions<br />
(National Institute o f Genetics, Japan W 1235 <strong>and</strong> W 1239) collected in southern New<br />
Guinea produced completely sterile hybrids with other accessions o f Oceanian rufipogon<br />
<strong>and</strong> Asian rufipogon. Hybrids between these two accessions <strong>and</strong> O. meridionalis<br />
were invable. These accessions are weakly perennial <strong>and</strong> have morphological characteristics<br />
o f annuals, such as short stature, short anthers relative to spikelet length, <strong>and</strong>
Biosystamalics of the Genus Oryza 53<br />
■/ '"v*<br />
%<br />
^ \ ' }■ ' 'S-:'' ■ ■- ■■-ir<br />
i<br />
A M '-”:'<br />
^ 'I f: ■' ■ ::<br />
■1.<br />
Figure 1.2.18.<br />
Distribution of 0, /iter/r/io/tc/fe Hg.<br />
high reproductive allocation. Further, they show an intermediate position between O.<br />
meridionalis <strong>and</strong> O. rufipogon in isozyme <strong>and</strong> nuclear DNA RFLP analysis. The results<br />
above suggest that Oryza germplasm exchange between Australia <strong>and</strong> New Guinea has<br />
occurred in tlie past.<br />
LaKn America<br />
Oryza ghmaepatuk Steud.<br />
AA genome wild species from Latin America (Figure 1.2.19) have recently generally<br />
been called O. glumaepatula despite the fact that no key taxonom ic character has<br />
been found to distinguish it from O. rufipogon sensu lacto (Juliano et al., 1998) <strong>and</strong><br />
this name was described <strong>origin</strong>ally as a cultigen from Suriname (Steudel, 1855). In<br />
addition, there are many reports indicating the presence o f Asian O. rufipogon in Latin<br />
America (Juliano et al., 1998). Accessions from Costa Rica were morphologically sim <br />
ilar to weedy rice <strong>and</strong> genetically similar to O. rufipogon. Their <strong>origin</strong> remains unclear.<br />
Recent ecological <strong>and</strong> genetic inform ation on South American AA genome germ-<br />
plasm has resulted from a series o f collaborative expeditions in South America that<br />
have focused on wild Oryza (M orishima <strong>and</strong> M artins, 1994). The various accum u<br />
lated research based on early collections by Oka (1961) in the Caribbean <strong>and</strong> South<br />
America <strong>and</strong> recent collections in Brazil (M orishim a <strong>and</strong> M artins, 1994) can be sum <br />
marized as follows;<br />
1. Three ecogeographic types o f O. glumaepatula have been proposed, based on<br />
a variety o f morphoecological traits <strong>and</strong> genetic markers. These three ecogeographic<br />
types are (a) the Central American, Caribbean, <strong>and</strong> northern South<br />
America type (perennial); (b) the Amazonian type (perennial-interm ediate<br />
annual); <strong>and</strong> (c) the central South American type (perennial) (Akimoto et al.,<br />
1998).<br />
2. Based on the complex relationships between O. glumaepatula <strong>and</strong> AA genome<br />
species from odrer regions O. glumaepatula seems to be polymorphic in <strong>origin</strong>.
54 Origin <strong>and</strong> History<br />
I f *<br />
p e e<br />
i<br />
B<br />
I<br />
s i<br />
■ [ L<br />
O. glumaepatula<br />
.- U "<br />
F ig u re 1.2,19.<br />
Distribution of 0. glumaepatula Steud,<br />
Based on analysis o f chloroplast DNA of four accessions, Dally <strong>and</strong> Second<br />
( lyyo) found that two accessions had a plastotype related to Asian AA genome<br />
species <strong>and</strong> two had a plastotype related to O. longistaminata o f Africa. Based<br />
on m ore comprehensive germplasm <strong>and</strong> using mitochondrial DNA pattern<br />
analysis, O. glumaepatula germplasm consists o f two groups, with one showing<br />
a closer relationship to O. longistaminata <strong>and</strong> the other a closer relationship<br />
to O. harthii o f Africa (Aldmoto, 1999).<br />
3. Reproductive barriers, such as Fi pollen sterility, exist between O. glumaepatula<br />
<strong>and</strong> Asian AA genome species. However, in natural habitats hybrids between<br />
wild O. glumaepatula <strong>and</strong> the cultigen, O. sativa, have been described<br />
from Cuba (Chu <strong>and</strong> Oka, 1970).<br />
4. Ecologically, O. glumaepatula in the Amazon basin consists o f both annual<br />
<strong>and</strong> perennial characteristics. Annual characteristics include high seed <strong>production</strong>,<br />
stiff awn, <strong>and</strong> propagation mainly by seed. Perennial characteristics<br />
include thlering from upper nodes <strong>and</strong> long anthers. Outcrossing has been<br />
estimated to be between 20 <strong>and</strong> 60% (Oka <strong>and</strong> Morishima, 1967). In com m on
Biosysteiriatics of the Genus Oryza 55<br />
with Oceanian O. rufipogon from New Guinea, Amazonian O, glumaepatula<br />
has the ability to break at nodes as floodwater rises, <strong>and</strong> becom e free floating<br />
(Vaughan, 1990b; M orishima <strong>and</strong> M artins, 1994).<br />
WEEDY RICE<br />
Weedy rices can be defined broadly as Oryza plants that are not intentionally cultivated<br />
but grow in <strong>and</strong> around arable l<strong>and</strong>. Weedy rices are diverse, <strong>and</strong> the m ore they<br />
resemble the crop ecologically, the worse tliey are (Moody, 1994). For rice, perhaps,<br />
the worst weeds are the wild species <strong>and</strong> weed forms o f rice that shed seeds before the<br />
crop is ripe <strong>and</strong> have seeds with dormancy (Cook, 1990). The literature on weedy rice<br />
is voluminous (Eastin, 1979; Asian Pacific Weed Science Society, 1998). O ur objectives<br />
here are to discuss nom enclature in relation to weedy rice <strong>and</strong> to discuss salient factors<br />
in the evolution o f AA genome weedy rice.<br />
Taxonomy<br />
Weedy rice usually involves hybridization <strong>and</strong>/or selection o f shattering types within<br />
the primary gene pools o f the two rice cultigens, O. sativa <strong>and</strong> O. glaberrima, <strong>and</strong><br />
their close relatives that share the AA genome. The appropriate taxonom ic names<br />
for shattering weedy rice o f the AA genome have not been established; however, a<br />
widely used name currently applied to weedy rice o f the AA genome in Asia is O.<br />
sativa f. spontanea. Many workers call weedy rice O. sativa since these plants can<br />
be indistinguishable morphologically from the cultigen. Oryza staphii has been used<br />
com monly for African AA genome weedy rice.<br />
In some areas, wild rice itself may directly become a weed in rice fields. W ild<br />
rice species that have been reported as agricultural weeds are O. rufipogon sensu lacto<br />
(AA genome) in Asia <strong>and</strong> Australia; O. barthi (AA genome), O. hngistaminata (AA<br />
genome), <strong>and</strong> O. punctata (probably the BB genome race) in Africa; O. officinalis<br />
in Asia; <strong>and</strong> O. lattfolia (CCD D genome) in Latin America (Second, 1989, 1991b;<br />
Vaughan et al., 1999). A syndrome o f characteristics usually is associated with weedy<br />
rices. They are annual, most com m only found in directly seeded fields, <strong>and</strong> are rare in<br />
transplanted rice cultures. They generally mature before the crop, but have variable<br />
shattering <strong>and</strong> variable degrees o f dormancy (Oka, 1988). Weedy rices are frequently<br />
awned <strong>and</strong> often have a red pericarp.<br />
Evolution<br />
Cultivated rice is always a com ponent o f the agroecosystem o f which weedy rice is<br />
a part; however, wild rice may or may not be. Various forms o f AA genome weedy<br />
rice are distributed over a wider area than are their wild relatives. Genetic characterization<br />
o f weedy rice accessions associated with O. sativa indicates that they can<br />
be classified generally into two groups, corresponding to the indica <strong>and</strong> japónica<br />
subspecies. Further, in both groups, two types with different propagating systems<br />
have been recognized; one is a crop m im ic type which is unconsciously seeded <strong>and</strong>
56 Origin <strong>and</strong> History<br />
harvested by humans mixed with cuitigens, <strong>and</strong> the other is naturally propagating<br />
type which disperses its seeds <strong>and</strong> germinatesj although the variation between the<br />
two types is continuous (Suh et al., 1997).<br />
Weedy rice is considered to have various <strong>origin</strong>s. Weedy rices found in regions<br />
where no wild rice occurs are probably derivatives o f cultigens. They have been selected<br />
naturally for weediness either from cultigens or from progeny o f natural hybridization<br />
between different cultivars. Such weedy plants may have persisted for a<br />
long time at low frequency with higher adaptability than improved cultivars when <strong>and</strong><br />
where adverse conditions prevail. In cases where weedy rices are not related genetically<br />
with associated cultigens, they are supposed to be relics o f ab<strong>and</strong>oned cultigens,<br />
or introduced from outside through mixtures with rice seeds. In Bhutan, however,<br />
japonica-like weedy rices are associated with japónica cultivars at altitudes higher than<br />
1700 m, <strong>and</strong> indica-like weedy rices with indica cultivars at lower altitudes, suggesting<br />
that primitive cultivars have the potential to evolve weedy forms (Suh et ah, 1997).<br />
Evidence supporting the possibility of the hybrid <strong>origin</strong> o f weedy rices is the<br />
fact that í«dícíi-like Korean weedy rices are not always typical indica but contain a<br />
few japonica-specific molecular markers (Cho et al., 1995; Suh et al., 1997). Weedy<br />
rice found in a rice field in hilly areas o f Nepal where both indica <strong>and</strong> japónica<br />
cultivars were mixed carried recombined isozyme genotypes (Tang <strong>and</strong> Morishima,<br />
1997). Although hybrids between distantly related types are more or less pollen sterile,<br />
fertile female gametes easily produce backcross progeny. In many countries, indica-<br />
like weedy rice has been found not only in Índica rice fields but also in japónica<br />
rice fields (Korea, Japan <strong>and</strong> Paraguay) (Suh et al., 1997; M orishima et al., 1999). In<br />
contrast, japonica-like weedy rices were rarely found in indica rice fields.<br />
Weedy rices found in wild rice (AA) growing areas probably are derivatives o f<br />
natural hybridization between the cultivar <strong>and</strong> wild rice growing nearby. Gene flow is<br />
mainly from cultivated to wild forms, because the former is predominantly inbreeding<br />
whereas the latter is partially outbreeding. Since no isolating barriers exist between<br />
wild <strong>and</strong> cultivated forms, weedy plants are naturally selected <strong>and</strong> invade rice fields.<br />
Most o f them have an annual habit (Oka <strong>and</strong> Chang, 1959), but weedy form s in<br />
deepwater rice fields propagate by ratoons as well as by seeds.<br />
There are many reports indicating that weedy rices have a higher tolerance than<br />
improved cultivars to various adverse environmental conditions such as drought, low<br />
temperature, <strong>and</strong> flooding (Suh et al., 1997). Since weedy rices are often m ore similar<br />
to cultivated rice than to true wild rice, introduction o f useful traits from weedy rices<br />
to the cultigen may be easier than using wild rice.<br />
In West Africa, the differences between the wild annual O. barthii <strong>and</strong> African<br />
cultigen O. glaherrima are more blurred than in Asia. Weedy or wild-cultivated intermediate<br />
forms are abundant. It is difficult to determine whether such plants are<br />
secondary products o f introgression, or if they are in a transient state from wild to<br />
cultivated forms. This may reflect an incipient stage o f domestication in which weedy<br />
or intermediate types could serve as a germplasm reservoir for differentiating diverse<br />
cultivars.<br />
During the last few decades, weedy rices declined in many Asian countries along<br />
with the spread o f transplanting culture <strong>and</strong> intensive weeding. But the recent revival<br />
o f direct-seeded culture, sometimes coupled with large-scale machine tillage, seems<br />
to be reversing this trend in Malaysia, Vietnam (Vaughan et al., 1999; Watanabe et al.,<br />
in press), <strong>and</strong> Korea (Cho et al., 1995).
Biosystematics of the Genus Oryzü 57<br />
Another concern in recent years is a possible drift o f herbicide-resistance genes<br />
into weedy rice populations. In rice, transgenic herbicide-resistant cultivars have yet<br />
to be released. W hen such cultivars are released, however, gene flow to weedy rice <strong>and</strong><br />
wild rice may be inevitable. Weedy rices have been reported to have an outcrossing<br />
rate of 1 to 52% (Oka <strong>and</strong> Chang, 1959; Langevin et al., 1990) <strong>and</strong> this is higher than<br />
for cultivated rice, so they may easily be contaminated by herbicide-resistance genes<br />
(Vaughan et al., 1999).<br />
RESEARCH DIRECTIONS<br />
M any areas related to the biosystematics o f the genus Oryza are unclear. Following is<br />
a list o f some o f research areas for the future.<br />
1. The generic boundary o f the genus Oryza <strong>and</strong> genetic relationships between<br />
Oryza <strong>and</strong> related genera require clarification.<br />
2. Germplasm o f the O. ridleyi complex <strong>and</strong> particularly the O. granulata com <br />
plex are underrepresented in the world’s germplasm collections. Very little<br />
ecogenetic research has been conducted on species from these complexes.<br />
3. Ecogenetic studies o f O. eichingeri <strong>and</strong> O. punctata are needed to clarify their<br />
relationship <strong>and</strong> diversity, For example, what is the relationship between wild<br />
<strong>and</strong> weedy O. punctata^.<br />
4. Specific taxonom ic <strong>and</strong> nomenclature clarification is needed o f the tetraploid<br />
<strong>and</strong> diploid races o f O. punctata.<br />
5. Lower Amazon collections o f CCDD genome species are needed to clarify the<br />
relationship between O. alta <strong>and</strong> O. latifolia.<br />
6. Underst<strong>and</strong>ing AA genome species is hampered by the lack o f inform ation on<br />
time o f divergence o f species. Reliable m olecular clock estimates are required<br />
to answer many confusing issues related to species with the AA genome.<br />
7. There is a lack o f germplasm ofAfrica wild rices from central regions o f Africa,<br />
such as the Congo basin, Sudan, <strong>and</strong> Central African Republic, which may be<br />
an im portant area o f CC <strong>and</strong> BB genome evolution.<br />
8. Clarification is needed o f the ecogenetic <strong>and</strong> taxonom ic differences between<br />
the Oceanian <strong>and</strong> Asian AA genome wild species <strong>and</strong> the differentiation within<br />
the Oceanian AA species in both Australia <strong>and</strong> New Guinea.<br />
9. The rice genome project is one o f the m ost advanced plant genome projects.<br />
Using this as a basis, an Oryza genome project is both possible <strong>and</strong> may<br />
enhance the already significant use o f wild rice genetic resources being used<br />
in plant improvement (Xiao et al., 1998).<br />
CAUTIONARY NOTE<br />
Gene banks provide scientists with easy access to a broad diversity o f germplasm.<br />
However, germplasm users working in <strong>and</strong> outside the gene bank are frequently laclcing<br />
in knowledge or inform ation regaining the germplasm they use in experiments.<br />
Few gene banks furnish inform ation on the number o f times particular accessions<br />
have been regenerated since collected. The only inform ation that might be indicative
58 Origin <strong>and</strong> History<br />
o f this is the date o f collection. Regeneration o f germplasm, particularly if it is not<br />
adapted to the growing location <strong>and</strong> is outcrossing, is likely to result in changes in<br />
its genetic com position or die. About one-third o f wild rice accessions (AA genome)<br />
collected in Thail<strong>and</strong> in 1983 were lost for various reasons after 10 years in the gene<br />
bank (M orishima, 1998), Thus the conclusions o f scientific papers, particularly those<br />
concerning evolution <strong>and</strong> biosystematics, will be influenced greatly by the quality o f<br />
germplasm used.<br />
Lade o f loiowledge concerning the identity o f germplasm can lead to erroneous<br />
conclusions. Although m ost germplasm from gene banks is identified correctly, m istakes<br />
can occur during h<strong>and</strong>ling in the gene bank. It is incum bent on the germplasm<br />
user to verify that germplasm received is identified correctly, particularly if the germplasm<br />
is to be referred to in a scientific paper. Chromosome counts may be a necessary<br />
part o f confirming the identity o f germplasm.<br />
Although gene banks usually can provide some passport data on distributed<br />
germplasm, care m ust be taken to verify where samples came from. Thus O, rufipogon<br />
from Sumatra, Indonesia, implies something different from a sample collected in Irian<br />
Jaya, Indonesia.<br />
Germplasm accessions represent populations. Wild species have different levels<br />
o f outcrossing. Thus germplasm users should expect germplasm to he polymorphic<br />
<strong>and</strong> heterogeneous <strong>and</strong> plan experiments accordingly.<br />
NOTE<br />
This review was based on literature available to the authors up to January 1999.<br />
REFERENCES<br />
Abedinia, M ., R. H. Henry, <strong>and</strong> S. C. Clark. 1998. D istribution <strong>and</strong> phylogeny o f<br />
Potamophila parvißora R.Br. a wild relative o f rice from eastern Australia. Genet.<br />
Res. Crop Evol. 45:399-406.<br />
Aggarwal, R. K., D. S. Brar, N. Huang, <strong>and</strong> G. S. Khush. 1996a. Differentiation within<br />
CCDD genome species in the genus Oryza as revealed by total genomic hybridization<br />
<strong>and</strong> RFLP analysis. <strong>Rice</strong> Genet. Newsl. 13:54-57.<br />
Aggarwal, R. K., D. S. Brar, N. Huang, <strong>and</strong> G. S. Khush. 1996b. Molecular analysis o f<br />
introgression in Oryza sativa/O. brachyantha <strong>and</strong> O. sativa/O. granulata derivatives.<br />
Int <strong>Rice</strong> Res. Notes 21:2-3.<br />
Aggarwal, R. K., D. S. Brar, G. S. Khush, <strong>and</strong> M . T. Jackson. 1996c. Oryza schlechteri<br />
Pilger has a distinct genome based on molecular analysis. <strong>Rice</strong> Genet. Newsl. 13:<br />
58-59.<br />
Aggarwal, R. K., D. S. Brar, <strong>and</strong> G. S. Khush. 1997. Two new genomes in the Oryza<br />
complex identified on the basis o f molecular divergence analysis using total genom<br />
ic DNA hybridization. Mol Gen. Genet, 254:1-12.<br />
Akimoto, M , 1999. Bio-system atks in the AA genome wild taxa o f genus Oryza (O.<br />
sativa complex): a comparative study o f morpho-physiological traits, isozymes<br />
<strong>and</strong> RPLPs o f nuclear <strong>and</strong> organelle. Ph.D. dissertation, Holckaido University,<br />
Sapporo, Japan.
Biosystematics of the Genus OryzQ 59<br />
Akimoto, M., Y. Shimamoto, <strong>and</strong> H. Morishima. 1998. Genetic differentiation in<br />
Oryza glumaepatula <strong>and</strong> its phylogenetic relationships with other AA genome<br />
species. <strong>Rice</strong> Genet. Newsl 14:37-39.<br />
Amante-Bordeos, A., L, A. Sitch, R. Nelson, R. D. Dalmacio, N. P. Oliva, H. Aswid-<br />
noor, <strong>and</strong> H. Leung. 1992. Transfer o f bacterial blight <strong>and</strong> blast resistance from<br />
the tetraploid wild rice Oryza minuta to cultivated rice, Oryza sativa. Theor. Appl<br />
Genet, 84:345“ 354.<br />
Asian Pacific Weed Science Society. 1998. International Symposium on Wild <strong>and</strong> Weedy<br />
<strong>Rice</strong>s in Agroecosystems, Ho Chi M inh City, Vietnam, Aug. lO - ll.<br />
Aswidinnoor, H., R. J. Nelson, J. F. Dallas, C. L. McIntyre, H. Leung, <strong>and</strong> J. P. Gustafson.<br />
1991. Cloning <strong>and</strong> characterisation of repetitive DNA sequences from genomes<br />
of Oryza minuta <strong>and</strong> Oryza australiensis. Genome 34:790-798.<br />
Barbier, P. 1989. Genetic variation <strong>and</strong>ecotypic differentiation in the wild rice species<br />
0 . rufipogon. 11. Influence o f the mating system <strong>and</strong> life <strong>history</strong> traits on the<br />
genetic structure of populations. Jpn. J. Genet 64:273-285.<br />
Barbier, P., H. Morishima, <strong>and</strong> A. Ishihama. 1991. Phylogenetic relationships o f annual<br />
<strong>and</strong> perennial wild rice probing by direct DNA sequencing. Theor. Appl<br />
Genet. 81:693-702.<br />
Bardenas, E. A , <strong>and</strong> T. T. Chang. 1966. M orpho-taxonom ic studies o f Oryza glaberrima<br />
Steud. <strong>and</strong> its related wild taxa, O. breviligulata A. Chev. et Roehr. <strong>and</strong> O.<br />
Stapfii Roschev. Bot Mag. Tokyo 79-.791-79S.<br />
Brar, D. S., <strong>and</strong> G, S. Khush. 1997. Alien introgression in rice. Plant Mol Biol 3 5 :3 5 -<br />
47.<br />
Brar, D. S., R. M . EUoran, J. D. Talag, K Abbasi, <strong>and</strong> G, S. Khush. 1998. Cytogenetic<br />
<strong>and</strong> molecular' characterization o f an intergeneric hybrid between Oryza sativa<br />
<strong>and</strong> Porteresia coarctata (Roxb.) Tateoka. <strong>Rice</strong> Genet. Newsl 15:43-45.<br />
Brucher, H. 1977. M orpho-genetic study o f a perennial wild rice ( Oryza sp,), SABRAO<br />
}. 9 (2 ):8 6 -9 0 .<br />
Cai, H. W., X. K. Wang, <strong>and</strong> H. M orishima. 1995. Isozyme variation in Asian com m on<br />
wild rice, Oryza rufipogon. <strong>Rice</strong> Genet Newsl 12:178-180.<br />
Cai, H. W., X. K. Wang, <strong>and</strong> H. Morishima. 1996. Geographic variation o f O. rufipogon<br />
with reference to annual-perennial differentiation. <strong>Rice</strong> Genet Newsl 13:67-69.<br />
Causse, M ., <strong>and</strong> A. Ghesquiere. 1991. Prospective use o f Oryza longistaminata for rice<br />
breeding. In <strong>Rice</strong> Genetics II. International <strong>Rice</strong> Research Institute, Manila, The<br />
Philippines, pp. 81-89.<br />
Chang, T. T. 1985. Crop <strong>history</strong> <strong>and</strong> genetic conservation: rice— a case study. Iowa<br />
State Univ. J. Res, 59(4):425-455.<br />
Chang, T. T„ S. H. Qu, M. D. Pathak, K. C. Ling, <strong>and</strong> H. E. Kauffman. 1975. The<br />
search for disease <strong>and</strong> insect resistance in rice germplasm. In O. H. Frankel <strong>and</strong><br />
1. G. Hawkes (eds.). Crop Genetic Resources for Today <strong>and</strong> Tomorrow. Cambridge<br />
University Press, Cambridge, pp. 183-200.<br />
Chen, J. L, <strong>and</strong> S. Matsunaka. 1991. Correlation o f propanil hydrolyzing enzyme<br />
activity with leaf morphology in wild rices o f genome CCDD. Pestic. Biochem.<br />
Physiol 4 0:80-85.<br />
Cho, Y. C., T. Y. Chung, <strong>and</strong> H. S. Suh. 1995. Genetic characteristics o f Korean weedy<br />
rice {Oryza sativa L.) by RFLP analysis. Euphytica 86:103-110.<br />
Chu, Y. E., <strong>and</strong> H. I. Oka. 1970. Introgression across isolating barriers in wild <strong>and</strong><br />
cultivated Oryza species. Evolution 24:344-355.
60 Origin <strong>and</strong> History<br />
Chu, Y. E., H. M orishima, <strong>and</strong> H. I. Oka. 1969. Reproductive barriers distributed in<br />
cultivated rice species <strong>and</strong> their wild relatives. Jpn. J. Genet. 44:207-223.<br />
Clayton, W. D., <strong>and</strong> S. A. Renvoize. 1986. Genera Graminum, grasses o f the world.<br />
Kew Bull X III.<br />
Cook, C. D. K. 1990. Origin, autoecology, <strong>and</strong> spread o f some o f the world’s m ost<br />
troublesome weeds. In A. H. Pieterse <strong>and</strong> K. J. Murphy (eds.), Aquatic Weeds:<br />
The Ecology <strong>and</strong> Management of Nuisance Aquatic Vegetation. Oxford University<br />
Press, Oxford, pp. 31-32.<br />
Cordesse, R, F. Grellet, A. S. Reddy, <strong>and</strong> M . Delsany. 1992. Genome specificity o f<br />
rDNA spacer fragments from O. sativa L. Theor. Appl Genet. 83:864-870.<br />
Dally, A. M ., <strong>and</strong> G. Second. 1990. Chloroplast DNA diversity in wild <strong>and</strong> cultivated<br />
species o f rice (genus Oryza, section Oryza): cladistic m utation <strong>and</strong> genetic distance<br />
analysis. Theor. Appl. Genet. 80:209-222.<br />
Dalmacio, R., D. S. Brar, T. Ishii, L. A. Sitch, S. S. Virm ani, <strong>and</strong> G. S. Khush. 1996.<br />
Male sterile line in rice developed with O. glumaepatula cytoplasm. Int. <strong>Rice</strong> Res.<br />
Newsl. 2 1 (l):2 2 -2 3 .<br />
De W it, J. M. J. 1981, Species concepts <strong>and</strong> systematics o f domesticated cereals. Kulturpflanze<br />
29:177-198.<br />
Doi, K., A. Yoshimura, M. Nakano, N. Iwata, <strong>and</strong> D. A. Vaughan. 1995. Polygenetic<br />
study o f AA genome species o f genus Oryza using nuclear RFLP. <strong>Rice</strong> Genet.<br />
Newsl. 12:160-162.<br />
Duistermaat, H. 1987. A revision o f Oryza (Gramineae) in Malaysia <strong>and</strong> Australia.<br />
Biwmea 32:157-193.<br />
Eastin, E, E 1979. Selected Bibliography o f Red <strong>Rice</strong> <strong>and</strong> Other Wild <strong>Rice</strong> (Oryza spp.).<br />
Tex. Agric. Exp. Stn. M P-1429, 59 pp.<br />
Ellis, J. L. 1985. Oryza ind<strong>and</strong>amanica Ellis, new rice plant from isl<strong>and</strong>s o f Andamans.<br />
Bull Bot Surv. Ind. 27:225-227,<br />
Flowers, T. J., S. A. Flowers, M. A. Hajibagheri, <strong>and</strong> A. R. Yeo. 1990. Salt tolerance in<br />
the halophytic wild rice, Porteresia coarctata Tateoka. NewPhytol 114:675-684.<br />
Fukui, K. N., N. Ohmido, <strong>and</strong> G. S. Khush. 1994. Variability in rDNA loci in the genus<br />
Oryza detected through fluorescence in-situ hybridization. Theor. Appl Genet.<br />
87:893-899.<br />
Fukui, K., R. Shishido, <strong>and</strong> T. Kinoshita. 1997. Identification o f the rice D-genome<br />
chromosomes by genomic in-situ hybridization. Theor. Appl Genet 9 5 :1 2 3 9 -<br />
1245.<br />
G<strong>and</strong>olfo, M . A., K. C. Nixon, W, L. Crepet, D. W. Stevenson, <strong>and</strong> E. M . Friss. 1998.<br />
Oldest known fossils o f monocotyledons. Nature 394:532-533.<br />
Gaut, B. S. 1998. Molecular clocks <strong>and</strong> nucleotide substitution rates in higher plants.<br />
Evol Biol 30:93-120.<br />
Ghesquiere, A, 1986. Evolution of Oryza longistaminata. In <strong>Rice</strong> Genetics. International<br />
<strong>Rice</strong> Research Institute, Manila, The Philippines, pp. 15-25.<br />
Harlan, J. R., <strong>and</strong> J. M, J. De Wit. 1971. Towards a rational classification o f cultivated<br />
plants. Taxon 20:509-517.<br />
Heinrichs, E. A., R G. Medrano, <strong>and</strong> H. R. Rapusas. 1985. Genetic Evaluation for Insect<br />
Resistance in <strong>Rice</strong>. International <strong>Rice</strong> Research Institute, Manila, The Philippines,<br />
356 pp.<br />
Hu, C. H, <strong>and</strong> C. C, Chang. 1967. Cytogenetic studies o f Oryza officinalis complex.<br />
I. Pi hybrid sterility in geographical races of O. officinaUs, Bot. Bull Acad. Sin.<br />
8 :8-19.
Biosystematics of the Genus Oryza 61<br />
Ichikawa, H., A. Hirai, <strong>and</strong> X Katayama. 1986. Genetic analyses o f Oryza species by<br />
molecular markers for chloroplast genomes. Theor. Appi Genet. 72:353-358.<br />
Ikeda, R., G. A. Busto, <strong>and</strong> T. Ogawa. 1990. Resistance o f wild rices to bacterial blight<br />
(BB). Int. <strong>Rice</strong> Res. Newsl. 15(3):14.<br />
Ikeda, R., D. A. Vaughan, <strong>and</strong> N. Kobayashi. 1994. L<strong>and</strong>races <strong>and</strong> wild relatives o f rice<br />
as sources o f useful genes. In JIRCAS International Symposium Series 2, Plant<br />
Genetic Resources Management in the Tropics^ Tsukuba, Japan, pp, 104-111,<br />
Ishii, T., T. Nakano, H. Maeda, <strong>and</strong> O. Kamijima. 1996. Phylogenetic relationships<br />
in AA genome species o f rice as revealed by RAPD analysis. Genes Genet Syst<br />
71(4):195-201.<br />
Iwamoto, M., H. Nagashima, T. Nagamine, H. Higo, <strong>and</strong> K. Higo. 1999. p-SINEllike<br />
intron o f the CafA catalase homologs <strong>and</strong> phylogenetic relationships among<br />
AA-genorae Oryza <strong>and</strong> related species, Theor, Appl Genet 98:853-861.<br />
Jena, K. K. 1994. Development o f intergeneric hybrid between O. sativa <strong>and</strong> Porteresia<br />
coarctata. <strong>Rice</strong> Genet Newsl. 11:78-79.<br />
Jena, K. K., <strong>and</strong> G. S. Khush, 1990. Introgression o f genes from Oryza ofßänalis Wall<br />
ex. Watt, to cultivated rice, O. sativa L. Theor. Appl. Genet 80:737-745.<br />
Jena, K. K., <strong>and</strong> G. Kodiert. 1991. Restriction fragment length polymorphism analysis<br />
o f GCDD genome species o f the genus Oryza L. Plant Mol Biol 16:831-839.<br />
Jena, K. K., G. S. Khush, <strong>and</strong> G. Kochert. 1992. RFLP analysis o f rice (Oryza sativa L.)<br />
introgression lines. Theor. Appl Genet 84:608-616.<br />
Juliano, A. B., M. E. B. Naredo, <strong>and</strong> M. T, Jackson. 1998, Taxonomic status o f Oryza<br />
glumaepatula Steud. I. Comparative morphological studies o f New World diploids<br />
<strong>and</strong> Asian AA genome species. Genet Res. Crop Evol 45:197-203.<br />
Kanazawa, A., M. Akimoto, H. M orishima, <strong>and</strong> Y. Shimamoto. 2000. Inter- <strong>and</strong> intra-<br />
specific distribution o f Stowaway transposable elements in AA-genome species o f<br />
wild rice. Theor. Appl Genet. 101:327-335.<br />
Kanno, A,, <strong>and</strong> A. Hirai. 1992. Comparative studies o f the structure o f chloroplast<br />
DNA from four species o f Oryza-. cloning <strong>and</strong> physical maps. Theor. Appl Genet.<br />
83:791-798.<br />
K atsu p, K. 1973. Variation in susceptibility to blast fungus Pyricularia oryzae Cav. in<br />
cultivated <strong>and</strong> wild rice, (in Japanese with English sum mary). Rep. Tottori Mycol<br />
Inst (Japan) 10:553-560.<br />
Khush, G. S., <strong>and</strong> K. K. Jena. 1989, Biosystematic status o f Oryza ind<strong>and</strong>amanica.<br />
Proceedings of the 6th International Congress ofSABRAO, Tsukuba, Japan.<br />
Khush, G. S., D. S. M ultani, G. V. Vergara, <strong>and</strong> D. S. Brar. 1990a. Taxonomic status o f<br />
O. ind<strong>and</strong>amanica. <strong>Rice</strong> Genet. Newsl 7:88-89.<br />
Khush, G. S., E. Bacalangco, <strong>and</strong> T. Ogawa. 1990b. A new gene for resistance to<br />
bacterial blight from Oryza longistaminata. <strong>Rice</strong> Genet. Newsl 7:121-122.<br />
Langevin, S. A., K. Clay, <strong>and</strong> J. B. Grace. 1990. The incidence <strong>and</strong> effects o f hybridization<br />
between cultivated rice <strong>and</strong> its related weed red rice (Oryza sativa L ).<br />
Evolution 44:1000-1009.<br />
Launert, E. 1965. A survey o f the genus Leersia in Africa. Senckenb. Biol 4 6 (2):29-153.<br />
Lin, S. C., <strong>and</strong> L. P. Yuan. 1980, Hybrid rice breeding in China. In Innovative Approaches<br />
to <strong>Rice</strong> Breeding. International <strong>Rice</strong> Research Institute, Manila, The Philippines,<br />
pp. 35-52.<br />
Lu, B. R. 1996. A Report ofIRRI-DPI Cooperative Collecting of Wild Oryza Species in<br />
Northeastern Australia <strong>and</strong> a Visit to Herbaria in Northern Territory <strong>and</strong> Singapore.<br />
International <strong>Rice</strong> Research Institute Library, Manila, The Philippines.
62 Oriain <strong>and</strong> History<br />
Lu, B, R,, Ma. E. B. Naredo, M. Macatangay, <strong>and</strong> Ma. T. Alvarez. 1997. Determ ination<br />
o f chromosome numbers of wild Oryza species in the International <strong>Rice</strong><br />
genebank at IRRI. Inf. <strong>Rice</strong> Res. Newsl 22(2).'5-6.<br />
Martinez, C. P., K. Arumuganathan, H. KÜcuchi, <strong>and</strong> E. D. Earle. 1994. Nuclear DNA<br />
content of ten rice species as determined by flow cytometry. Jpn.J. Genet. 6 9 :5 1 3 -<br />
523.<br />
M oody K. 1994. Weedy forms of rice in Southeast Asia. Paper presented at the Padi<br />
Angin Workshop, M ARDI, Peirang, Malaysia, May 18.<br />
Morat, P., T. Deroin, <strong>and</strong> H, Couderc. 1994. Présence en NouveU-Calédonie d’une<br />
espèce endemique du genre Oryza L. (Gram inae). BuU. Mus. Natl Hist. Nat Paris<br />
4, ser. 16, Sec. B, Adansonia 1:3-10.<br />
Morishima, H. 1969. Phenetic similarity <strong>and</strong> phylogenetic relationships among strains<br />
o f Oryza perennis estimated by methods of numerical taxonomy. Evolution 23:<br />
429-443.<br />
Morishima, H. 1994. Polymorphism of bacterial blight resistance in populations of<br />
wild <strong>and</strong> cultivated rice: a lesson from natural ecosystem. In Towards Enhanced<br />
<strong>and</strong> Sustainable Agricultural Productivity in the 2000’s; Breeding Research <strong>and</strong><br />
Bio<strong>technology</strong> Proceedings o f the 7th International Congress o f SABRAO <strong>and</strong><br />
W SAA,pp. 139-144,<br />
Morishima, H. 1998. Conservation <strong>and</strong> genetic characterisation o f plant genetic resources.<br />
In Plant Genetic Resources: Characterisation <strong>and</strong> Evaluation. MAFF, Tsu-<br />
kuba, Japan, pp. 31-42.<br />
Morishima, H., <strong>and</strong>P. S. Martins. 1994. Investigations of Plant Genetic Resources in the<br />
Amazon Basin with the Erpphasis on the Genus Oryza. M onbusho International<br />
Scientific Research Program Japan <strong>and</strong> Research Support Foundation o f the State<br />
o f Sao Paulo, Brazil.<br />
Morishima, H., Y. Sano, <strong>and</strong> H. I. Oka 1984. Differentiation o f perennial <strong>and</strong> annual<br />
types due to their habitat conditions in the wild rice Oryza perennis. Plant Syst.<br />
Evol. 144:119-135.<br />
Morishima, H., Y. Sano, <strong>and</strong> H. I. Oka. 1992. Evolutionary studies in cultivated rice<br />
<strong>and</strong> its wild relatives. Oxford Surv. Evol Biol 8:135-184.<br />
Morishima, H ., M . Akimoto, A, Ando, E. P. de Silva, <strong>and</strong> E. N. Chaibub. 1999. Study<br />
Tour in Paraguay <strong>and</strong> Argentina for Investigation o f Oryza Species. National Institute<br />
o f Genetics, M ishima, Japan,<br />
Multani, D. S., K. K. Jena, D. S. Brar, B. C. de los Reyes, E. R. Angeles, <strong>and</strong> G. S. Khush.<br />
1994. Development o f m onosom ie alien addition lines <strong>and</strong> introgression o f genes<br />
from O. australiensis Dom in. to cultivated rice, O. sativa L. Theor. Appl Genet<br />
88:102-109.<br />
Nakajima, R„ K. Noma, H. Ohtsubo, <strong>and</strong> E. Ohtsubo. 1996. Identification <strong>and</strong> characterisation<br />
of two t<strong>and</strong>em repeat sequences (TrsB <strong>and</strong> TrsC) <strong>and</strong> a retrotrans-<br />
poson {RIREl) as genome-general sequences in rice. Genes Genet Syst 7 1 :3 7 3 -<br />
382.<br />
Naredo, Ma. E. B., D. A. Vaughan, <strong>and</strong> F. Santa Cruz. 1993. Comparative spikelet<br />
morphology o f Oryza schlechteri Pilger <strong>and</strong> related species o f Leersia <strong>and</strong> Oryza<br />
(Poaceae). J. Plant Res. 106:109-112.<br />
Neto, G. C., Y. Kono, H. Hyakutake, M. Watanabe, Y. Suzuki, <strong>and</strong> A. Sakurai. 1991.<br />
Isolation <strong>and</strong> identification o f (-)-jasm onic acid from wild rice, O. officinalis, as<br />
an antifungal substance. Agric. Biol Chem. 55(12):3097-3098.
Biosystematics of the Genus Oryza 63<br />
Ng, N. Q., T. T. Chang, J. T. Williams, <strong>and</strong> J. G. Hawkes. 1981a. Morphological studies<br />
o f Asian rice <strong>and</strong> its related wild species <strong>and</strong> the recognition of a new Australian<br />
taxon. Biol. J. Linn. Soc. 16:303-313.<br />
Ng, N. Q., J. G. Hawkes, J. T. Williams, <strong>and</strong> T. T. Chang. 1981b. The recognition o f a<br />
new species o f rice {Oryza) from Australia. Bot J. Linn. Soc. 82:327-330.<br />
Noma, K,, R. Nakajima, H. Ohtsubo, <strong>and</strong> E. Ohtsubo, 1997. RIREL a retrotransposon<br />
from wild rice, Oryza australiensis. Genes Genet. Syst. 72:131-140.<br />
Oelke, E. A., R. A. Porter, A. W. Grombacher, <strong>and</strong> P. B. Addis. 1997. Wild rice: new<br />
interest in an old crop. Cereal Foods World 42{4):234-246.<br />
Oka, H. I. 1961. Report o f Trip for Investigation of <strong>Rice</strong> in Latin American Countries,<br />
Unpublished. International <strong>Rice</strong> Research Institute Library, Manila, The Philippines.<br />
Oka, H. I. 1988. Origin o f Cultivated <strong>Rice</strong>. Japan Scientific Societies Press, Tokyo.<br />
254 pp.<br />
Oka, H. I., <strong>and</strong> W. T. Chang. 1959. The impact o f cultivation on populations o f wild<br />
rice, Oryza sativa f. spontanea. Phyton 13:105-117.<br />
Oka, H. I., <strong>and</strong> H. M orishim a. 1967. Variation in the breeding systems o f a wild rice,<br />
Oryza perennis. Evolution 21:249-258.<br />
Pyrali, G. L. 1969. Taxonom ic <strong>and</strong> distributional studies in Leersia (Gram inae). Iowa<br />
State Univ. /. Sei 44:215-270.<br />
Roschevicz, R. 1931. A contribution to the loiowledge o f rice (translated from Russian).<br />
Bull Appl Bot. Genet. Plant Breed. 27(4 ):1 -1 3 3 .<br />
Sano, Y. 1980. Adaptive strategies compared between the diploid <strong>and</strong> tetraploid forms<br />
o f O. punctata. Bot. Mag. Tokyo 93:171-180.<br />
Sano, Y., <strong>and</strong> R. Sano. 1990. Variation o f the intergenic spacer region o f ribosomal<br />
DNA in cultivated <strong>and</strong> wild rice species. Genome 33:209-218.<br />
Sano, Y., H. M orishima, <strong>and</strong> H. I. Oka. 1980. Intermediate perennial-annual populations<br />
o f Oryza perennis found in Thail<strong>and</strong> <strong>and</strong> their evolutionary significance.<br />
Bot. Mag. Tokyo 93:291-305.<br />
Sasahara, T., T. Sengoku, <strong>and</strong> Y. Sano. 1982. CO 2 <strong>and</strong> water vapour exchange as related<br />
to shade tolerance o f O. punctata Kotschy. Photosynthetica 16(3);356-361.<br />
Second, G. 1985. Evolutionary relationships in tlie Sativa group o f Oryza based on<br />
isozyme data. Genet. Sei Evol 17:89-114.<br />
Second, G. 1987. Field notes on a collection o f wild rice species in Australia, May<br />
1987. Mimeographed. International <strong>Rice</strong> Research Institute Library, Manila, The<br />
Philippines.<br />
Second, G. 1989. Additional observations <strong>and</strong> collection o f the Oryza latifolia Desv.<br />
species complex. <strong>Rice</strong> Genet. Newsl 6:73-76.<br />
Second, G. 1991a. Molecular markers in rice systematics <strong>and</strong> the evaluation o f genetic<br />
resources. In Y, P. S. Bajaj (ed.). <strong>Rice</strong> Bio<strong>technology</strong> in Agriculture <strong>and</strong> ForestryyVol.<br />
14. Springer-Verlag, Berlin, pp. 468-494.<br />
Second, G. 1991b. Trip to San Jose Area, Occidental Mindoro. Mimeographed. International<br />
<strong>Rice</strong> Research Institute Library, Manila, The Philippines.<br />
Shishido, R., Y. Sano, <strong>and</strong> K. Fukui. 1996. The third 45SrDNA locus in O. eichingeri<br />
(CC) newly detected by an improved FISH method. <strong>Rice</strong> Genet. Newsl 13:84-85.<br />
Sitch, L. A. 1990. Incom patibility barriers operating in crosses o f Oryza sativa with<br />
related species <strong>and</strong> genera. In J. P. Gustafson, (ed.), Genetic Manipulation in Plant<br />
Improvement. Vol. II. Plenum Press, New York, pp. 77-94.
Origin <strong>and</strong> History<br />
Soreng, R. J., <strong>and</strong> J. I. Davis. 1998. Phylogenetics <strong>and</strong> character evolution in the grass<br />
family (Poaceae): simultaneous analysis o f morphological <strong>and</strong> chloroplast DNA<br />
restriction site character sets. Boi. Rev. 6 4 (1 ):1 -6 7 .<br />
Stebbins, G. L. 1981. Coevolution o f grasses <strong>and</strong> herbivores. Ann. Mo. Bot. Card.<br />
68:75-86.<br />
Steudal, E. 1855. Synopsis Plantarum Graminum. Stuttgart<br />
Suh, H. S., Y. I. Sato, <strong>and</strong> H. M orishima. 1997. Genetic characterisation o f weedy rice<br />
{Oryza sativa L.) based on morpho-physiology, isozymes <strong>and</strong> RAPD markers.<br />
Theor. Appl. Genet. 94:316-321.<br />
Tang, L. H., <strong>and</strong> H. M orishima. 1997. Genetic characterization o f weedy rices <strong>and</strong><br />
the inference on their <strong>origin</strong>s. Breeding Set. 47:153-160 (in Japanese with English<br />
summary).<br />
Tateoka, T. 1962a. Taxonomic studies o f Oryza. I. O. latifolia complex. Bot. Mag. Tokyo<br />
75:418-427.<br />
Tateoka, T. 1962b. Taxonomic studies o f Oryza. II. Several species complexes. Bot.<br />
Mag, Tokyo 76:165-173.<br />
Tateoka, T. 1963. Taxonomic studies o f Oryza. III. Key to the species <strong>and</strong> their enum<br />
eration. Bot. Mag. Tokyo 76:165-173.<br />
Tateoka, T. 1964. Report of explorations in East Africa <strong>and</strong> Madagascar. International<br />
<strong>Rice</strong> Research Institute Library, Manila, The Philippines.<br />
Tateol^a, T. 1965a. A taxonom ic study o f Oryza eichingeri <strong>and</strong> O. punctata. Bot Mag.<br />
Tofeyo 78:156-163.<br />
Tateoka, T. 1965b. Taxonomy <strong>and</strong> chrom osom e numbers o f African representatives<br />
o f the Oryza officinalis copiplex. Bot Mag. Tokyo 78:198-201.<br />
Tateoka, T , <strong>and</strong> J. V. Pancho. 1963. A cytotaxonom ic study o f Oryza minuta <strong>and</strong> O.<br />
officinalis. Bot. Mag. Tokyo 76:366-373.<br />
Tzvelev, N. N. 1989. The system o f grasses (Poaceae) <strong>and</strong> their evolution. Bot Rev.<br />
55(3):141-203.<br />
Uozu, S., H. Ikehashi, N. Ohmido, H. Ohtsubo, E. Ohtsubo, <strong>and</strong> K. Fukui. 1997.<br />
Repetitive sequences: cause o f variation in genome size <strong>and</strong> chromosom e m orphology<br />
in the genus Oryza. Plant Mol. Biol. 35:791-799.<br />
Van, T. K., <strong>and</strong> G. K. Guan. 1959. The resistance o f Oryza ridleyi (Hook.) to padi<br />
stemborer attack. Malay Agric.}. 4 2 (4 ):2 0 7 -2 10.<br />
Vaughan, D. A. 1989a. The Genus Oryza L.; Current Status ofTaxonomy. Res. Pap. Ser.<br />
138. International <strong>Rice</strong> Research Institute, Manila, The Philippines.<br />
Vaughan, D. A. 1989b. Two species o f Oryza officinalis complex present in Sri Lanka.<br />
Int <strong>Rice</strong> Res. Newsl. 14(4):5.<br />
Vaughan, D. A. 1990a. A new rhizomatous Oryza species (Poaceae) from Sri Lanka.<br />
Bot J. Linn. Soc. 103:159-163.<br />
Vaughan, D. A. 1990b. The Wild Relatives of <strong>Rice</strong> in Papua New Guinea. International<br />
<strong>Rice</strong> Research Institute Library, Manila, The Philippines.<br />
Vaughan, D. A. 1994. Wild Relatives of <strong>Rice</strong>: Genetic Resources H<strong>and</strong>book. International<br />
<strong>Rice</strong> Research Institute, Manila, The Philippines. 137 p.<br />
Vaughan, D. A,, <strong>and</strong> L. A. Sitch. 1991. Gene flow from the jungle to farmers: wild rice<br />
genetic resources <strong>and</strong> tlieir uses. BioScience 4 4 :2 2 -2 8<br />
Vaughan, D. A., H. Watanabe, D. Hille Ris Lambers, Md. A. Zain, <strong>and</strong> N. Tomooka.<br />
1999. Weedy rice complexes in direct seeding rice cultures. Jpn. J. Crop Sei. 67(2):<br />
277-280.
Biosystemntics of the Genus Oryza 65<br />
Watanabe, H., D. A. Vaughan, <strong>and</strong> N. Tomooka. In press. Weedy rice complexes: case<br />
studies from Malaysia, Vietnam <strong>and</strong> Suriname. In Proceedings of the International<br />
Symposium on Wild <strong>and</strong> Weedy <strong>Rice</strong>s in Agro-ecosystem. Asian Pacific Weed Seience<br />
Society, Ho Chi M inh City, Vietnam.<br />
Watson, L., H. T. Clifford, <strong>and</strong> M . J. Dallwitz. 1985. The classification o f Poaceae:<br />
subfamilies <strong>and</strong> supertribes. Aust. J, Bot. 33:433-484.<br />
Wolfe, K. H., M. Gouy, Y. W. Yang, P. M. Sharp, <strong>and</strong> W. H. Li. 1989. Date o f m o n ocotdicot<br />
divergence estimated from chloroplast DNA sequence data. Proc. Natl.<br />
Acad. Sei. USA 86:6201-6205.<br />
Wu, W , Y. Lu, <strong>and</strong> G. Wang. 1990. A revision on the scientific <strong>and</strong> Chinese name o f<br />
verrucose wild rice indigenous to China. Chin.}. <strong>Rice</strong> Sd. 4:33-37.<br />
Xiao, J., J. Li, S. Gr<strong>and</strong>illo, S. N. Ahn, L. Yuan, S. D. Tanksley, <strong>and</strong> S. R. McCouch.<br />
1998. Identification o f trait-improving quantitative trait loci alleles from wild<br />
rice relative, Oryza rufipogon. Genetics 150:899-909.<br />
Yasui, H., <strong>and</strong> N. Iwata. 1996. Ditelosom ic alien addition lines o f rice (Oryza sativa L.)<br />
carrying a pair o f telocentric chromosomes o f O. punctata Kotschy. <strong>Rice</strong> Genet.<br />
Newsl. 13:80-82.<br />
Yasui, H., A. Yoshimura, <strong>and</strong> N. Iwata. 1992. Characterisation o f m onosom ic alien<br />
chromosomes o f O. punctata transferred to O. sativa using RFLP markers. <strong>Rice</strong><br />
Genet Newsl. 9:138-142.<br />
Yasui, H., K. I. Nonomura, <strong>and</strong> N. Iwata 1994. Identification o f O. punctata chrom o<br />
somes transferred to m onosom ic alien addition lines o f 0 . sativa by fluorescence<br />
in-situ hybridization. <strong>Rice</strong> Genet. Newsl. 11:76-77.
Chopter<br />
1.3<br />
American <strong>Rice</strong> Industry: Historical<br />
Overview of Production<br />
<strong>and</strong> Marketing<br />
Henry C. Dethioff<br />
Professor Emeritus<br />
Department of History<br />
Texas A&M University<br />
College Stotion, Texas<br />
INTRODUCTION<br />
EARLY AMERICAN RICE CULTURE<br />
EXPANSION, 1750-1850<br />
TIME OF TRANSITION,1850-1880<br />
BEGINNING OF THE MODERN INDUSTRY, 1880-1900<br />
A NEW CENTURY AND A NEW DEAL, 1900-1945<br />
REFERENCES<br />
INTRODUCTION<br />
<strong>Rice</strong> cultivation, milling, <strong>and</strong> marketing is one o f America’s oldest agribusinesses. In <br />
deed, rice, Oryza sativa^ is one o f humanldnd’s m ost ancient <strong>and</strong> m ost universally consumed<br />
foods. It is the one grain crop grown almost exclusively for human food. The<br />
advent of cultivated grains in human society is closely associated with the inception of<br />
the city <strong>and</strong> civilization. Som etim e around 10,000 b .c., men, or more likely women,<br />
began to cultivate grain. Many believe that the earliest cultivation was along the Yellow<br />
River of China or in similar aquatic <strong>and</strong> tropical terrain in Asia. Cultivation eventually<br />
extended from the Yellow River o f China to the Amur River on the border between<br />
the Soviet Union <strong>and</strong> China. Because of its unique adaptability to diverse growing<br />
conditions, its ease o f preparation <strong>and</strong> palatability, <strong>and</strong> its durability in storage, rice<br />
<strong>Rice</strong>: Origin, History, Technology, <strong>and</strong> Production, edited by C. Wayne <strong>Smith</strong><br />
ISBN 0-471-34516-4 © <strong>2003</strong> John Wiley & Sons, Inc.<br />
67
68 Origin <strong>and</strong> History<br />
cultivation spread rapidly to the cool climates <strong>and</strong> high mountains o f Nepal <strong>and</strong> India,<br />
to the hot deserts o f Pakistan, Iran, <strong>and</strong> Egypt, <strong>and</strong> into the tropical <strong>and</strong> desert regions<br />
o f Soudieast Asia <strong>and</strong> Africa. The inception o f agriculture came with the cultivation<br />
o f rice <strong>and</strong> other wild grains. After thous<strong>and</strong>s o f years o f sameness <strong>and</strong> virtual stagnation,<br />
with the advent of agriculture, human development suddenly accelerated.<br />
Agriculture brought an abundance o f food that humankind previously had not<br />
experienced. Cultivation, rather than hunting <strong>and</strong> gathering, became the primary<br />
econom ic endeavor <strong>and</strong> prescribed a revolutionary new social order— the city. The<br />
cit/s primary econom ic function was as that of a granary. Its m ajor social function<br />
was as a nursery for the young, <strong>and</strong> a safe <strong>and</strong> defensible refuge for its inhabitants.<br />
Cities organized existing human life into a new state o f dynamic tension <strong>and</strong> interaction<br />
intrinsic to civilization, <strong>and</strong> civilization brought with it “the need to administer<br />
the l<strong>and</strong> <strong>and</strong> the water used to irrigate the l<strong>and</strong>” (Mumford, 1961; Tannahill, 1973).<br />
Agriculture imposed civilization upon humans, <strong>and</strong> rice early became the most widely<br />
cultivated <strong>and</strong> universally consumed grain.<br />
The necessity for agriculture generally is associated with the receding glaciers o f<br />
the last ice age more than 10,000 years ago, the subsequent moderation o f climate,<br />
<strong>and</strong> the demise <strong>and</strong> retreat of large animal species to more northern regions. The<br />
scarcity o f game forced humans into more intensive reliance on wild <strong>and</strong> then on<br />
domesticated grains <strong>and</strong> foodstuffs. The diversion o f human energies from hunting<br />
to agriculture <strong>and</strong> to a state o f civilization occupied thous<strong>and</strong>s o f years, during which<br />
time regional <strong>and</strong> cultural distinctions arose differentiating one civilization from<br />
another. Societies often were distinguished by the food they ate <strong>and</strong> the manner in<br />
which they produced or obtained their food. Assuming that the search, <strong>production</strong>,<br />
<strong>technology</strong>, social organization, <strong>and</strong> behavioral characteristics attendant upon foods<br />
<strong>and</strong> their consumption are m ajor com ponents o f hum an endeavor through the years,<br />
the most widely consumed of aU human foods— ^rice— deserves a prom inent place in<br />
<strong>history</strong> (Dethloff, 1988).<br />
In the second <strong>and</strong> third m illennium b .c., the tribes o f central Asia <strong>and</strong> India<br />
offered m ilk <strong>and</strong> rice in the ceremonial fires to Agni, die god o f fire <strong>and</strong> witness to aU<br />
creation. They offered rice because rice was their choicest food. <strong>Rice</strong> in India continues<br />
to be used in rituals <strong>and</strong> prayer. It is the first food offered the infant, <strong>and</strong> the first<br />
mouthful offered by a new bride to her husb<strong>and</strong>. In the Western world <strong>and</strong> die United<br />
States, rice is thrown on the bride <strong>and</strong> groom at weddings as a symbol o f abundance<br />
<strong>and</strong> fertility. The Susruta Samhita> compiled in India in about 1000 b .c., classifies rice<br />
by varieties based on duration, water requirements, <strong>and</strong> nutritional values. <strong>Rice</strong> was<br />
cultivated during the dynastic period in Egypt. Carbonized grains have been found in<br />
the pyramids. <strong>Rice</strong> entered into trade between Rome <strong>and</strong> Egypt <strong>and</strong> between Egypt,<br />
India, <strong>and</strong> China. <strong>Rice</strong> is mentioned in Chinese records o f 2800 b .c. In Chinese, the<br />
spoken word <strong>and</strong> the written character for cooked rice is fan, which is also the word<br />
for food, <strong>and</strong> when pronounced with a different intonation is the verb to eat. <strong>Rice</strong> is<br />
ingrained deeply into the culture, literature, <strong>and</strong> <strong>history</strong> o f Japan. <strong>Rice</strong> is an industry,<br />
an agribusiness, with historic cultural <strong>and</strong> global dimensions.<br />
Since colonial times, the United States has produced approximately 1.5 to 5% o f<br />
the world’s rice but accounts for 15 to 30% o f the world’s total exports. Fifty to 90%<br />
of the U.S. rice crop has been sold abroad in most years since the industry began in<br />
1685. In recent decades the market value o f U.S. rice has approximated $1.5 billion<br />
annually. Although the United States historically has exported most o f its rice, per
American <strong>Rice</strong> Industry: Historical Overview of Production <strong>and</strong> Marketing 69<br />
capita domestic consumption has increased markedly in recent decades. The U.S.<br />
industry is unique in being characterized as a large-scale, capital-intensive, mass<strong>production</strong><br />
agricultural enterprise. The average size o f a rice farm in the United States<br />
at the close o f the twentieth century was 94 ha (1 hectare = 2.471 acres) compared<br />
to the average farm size in Thail<strong>and</strong>, the world’s leading exporter o f rice, o f 3.8 ha.<br />
The United States has utilized advanced <strong>technology</strong> in the <strong>production</strong> o f rice since<br />
colonial times. The industry’s survival has depended largely on international m arketing.<br />
During its three centuries o f development, tlie U.S. rice industry has becom e<br />
a sophisticated infrastructure o f private- <strong>and</strong> public-sector interests (i.e., growers,<br />
millers, <strong>and</strong> merchants, with administrators <strong>and</strong> scientists from government agencies<br />
<strong>and</strong> educational institutions, all closely associated with the <strong>production</strong>, marketing,<br />
<strong>and</strong> distribution o f U.S. rice to the global com munity).<br />
e a r l y AMERICAN RICE CULTURE<br />
The British Lords Proprietor o f the Carolina colonies actively encouraged the cultivation<br />
o f rice soon after founding o f the colonies in the mid-seventeenth century,<br />
<strong>and</strong> professed to be "Laying out in Severall places” for proper seeds for the colony.<br />
Although there may have been prior experiments with the cultivation o f rice, the first<br />
recorded effort was made by Dr. Henry Woodward o f Charleston, South Carolina,<br />
who obtained seed from John Thurber, the captain o f a ship arriving from Madagascar<br />
in 1685. By 1690, rice <strong>production</strong> had grown to such proportions that the colonists<br />
proposed paying their rents to the Proprietors in rice <strong>and</strong> other commodities. In 1691,<br />
Peter Jacob Guerard was granted a patent by the colonial assembly o f South Carolina<br />
for the development o f a pendulum engine to "huske rice.” In 1695, the Proprietors<br />
approved the payment o f rents in rice. Following the introduction of improved varieties,<br />
South Carolina exported 10,000 lb (4536 kg) o f rice in 1698, 131,000 lb (59422<br />
kg) in 1699, <strong>and</strong> 394,000 lb (178 718 kg) in 1700 (Drayton, 1802; Ramsay, 1858; Salley,<br />
1919; Littlefield, 1981).<br />
Early <strong>production</strong> depended on ponds <strong>and</strong> rainwater for cultivation. W ith populations<br />
thin <strong>and</strong> labor very scarce, Carolina planters began importing slave labor<br />
from Africa to plant <strong>and</strong> harvest rice. The Africans, often familiar with rice <strong>production</strong><br />
which had spread from Egypt through Africa in ancient times, contributed their<br />
own methods o f planting, hoeing, threshing, <strong>and</strong> polishing. By 1709, <strong>production</strong> had<br />
soared to 1.5 million pounds (680 m t), <strong>and</strong> Carolina rice had become a m ajor factor<br />
in Western rice trade. The colony adopted a st<strong>and</strong>ard o f weights <strong>and</strong> measurements<br />
in 1714, specifying among otlier things, the size o f a barrel used to ship rice, <strong>and</strong><br />
imposing penalties upon the cooper <strong>and</strong> seller for failure to use legal-size containers.<br />
Production reached over 20 million pounds annually by 1721 (Drayton, 1802; Ram <br />
say, 1858; Salley, 1919; Littlefield, 1981). American rice had become a m ajor factor in<br />
world trade.<br />
Colonial rice growers soon discovered an impediment to trade created by British<br />
laws. The British Navigation Acts required that colonial rice be shipped to British<br />
ports, on British-built ships, where it was taxed, <strong>and</strong> reexported by British merchants<br />
to non-British consumers. Following American protests, <strong>and</strong> acknowledging the reality<br />
that rice rotted during the long delays forced by transshipment through British<br />
ports. Parliament in 1731 allowed direct shipments of American rice to ports in Spain,
70 Origin <strong>and</strong> History<br />
Portugal, North Africa, <strong>and</strong> the Mediterranean as long as those shipments were made<br />
in British ships (which were forbidden admission into Spanish ports), American rice<br />
growers became early advocates o f free trade <strong>and</strong> learned ways to circumvent British<br />
trade regulations.<br />
But the constraints on the colonial rice trade were not all o f British <strong>origin</strong>. Piracy<br />
soon became a costly econom ic depredation <strong>and</strong> disincentive to exp<strong>and</strong>ing rice trade.<br />
The South Carolina Colonial Assembly finally took independent action against the<br />
scourge o f pirates raiding colonial commerce. Between 1717 <strong>and</strong> 1721, an estimated<br />
30 to 40 vessels fell victim to attack off the shores o f South Carolina. Previously<br />
tolerated, if not encouraged, now that rice had becom e a m ajor industry, piracy had<br />
become an econom ic liability rather than an asset. The assembly authorized Captain<br />
Woodes Rogers to outfit a small fleet o f warships <strong>and</strong> attack the m ajor stronghold<br />
o f the pirates on Providence Isl<strong>and</strong>. But an offer of amnesty accepted by the pirates<br />
in exchange for their “ceasing <strong>and</strong> desisting” in their attacks on colonial shipments,<br />
was followed by more piracy. Subsequent naval actions led by Governor Johnson <strong>and</strong><br />
others resulted in the surrender, trial,- <strong>and</strong> execution o f the remaining pirates <strong>and</strong> the<br />
end o f the era of piracy (Ramsay, 1858; Gray, 1932).<br />
E X P A N SIO N ,1 7 5 0 -1 8 5 0<br />
Two im portant innovations resulted in the rapid expansion o f rice <strong>production</strong> in<br />
the southeastern United States over the next 100 years, 1750-1850. One involved a<br />
remarkable system of water cultivation that harnessed the tidal flow o f the coastal<br />
rivers (Figure 1.3.1). The ocean tides, when rising, forced fresh water ahead o f the<br />
Figure 1.3.1. Panorama of colonial rice fields. (Author's photograph taker» ot the Georgetown Museum; courtesy<br />
of the Georgetown Museum,)
American Ríce Industry: Historical Overview of Production <strong>and</strong> Marketing 71<br />
seawater “upriver” raising the river water level. The cultivation o f rice (i.e., flooding<br />
the fields to prevent the intrusion o f wild grasses) had depended first on rainfall <strong>and</strong><br />
then on the introduction o f raised ponds or “reserves” from which water could be<br />
released to flood fields by gravity flow (Figure 1.3.2). About 1750, Mckewn Johnstone,<br />
a planter in the area o f Winyah Bay, began experimenting with the tidal flow as a<br />
method o f flooding his fields. Using small levees along the river, he devised a system o f<br />
water gates or locks that were forced open when the tide came in, <strong>and</strong> closed when the<br />
tide receded, locking the fresh water at higher elevations than the surrounding fields<br />
[8 to 10 ft (2.5 to 3 m) above sea level]. Fields were surrounded by embanlonents tliat<br />
contained the water drained from the river into the fields. Each enclosed field could<br />
be flooded <strong>and</strong> the water levels adjusted independent o f adjoining fields (Drayton,<br />
1802; Lawson, 1972). The system opened thous<strong>and</strong> o f new acres to rice cultivation<br />
<strong>and</strong> greatly improved cultivation practices <strong>and</strong> yields.<br />
The second innovation that revolutionized the early American rice industry was<br />
an improved, tidal-powered rice mill developed in the 1780s by Jonathan Lucas o f<br />
Charleston (Figure 1.3.3). Lucas realized that the tidal gates <strong>and</strong> locks used to im <br />
pound water for irrigation also contained water that could be used to turn a waterwheel.<br />
Using the com m on pounding (m ortar <strong>and</strong> pestle) milling approach, Lucas<br />
designed an elaborate mechanical mill powered by tidal flows <strong>and</strong> tidal im poundments<br />
that could mill 100 barrels [at 600 lb (272 kg) each] per day. Lucas began building<br />
mills throughout the Carolinas <strong>and</strong> Georgia <strong>and</strong> in Engl<strong>and</strong> <strong>and</strong> Egypt (Lucas<br />
Figure 1.3.2. Rivers of South Carolina. (From Drayton, 1802.)
72 Origin <strong>and</strong> History<br />
family papers). By the time o f the American revolution, South Carolina <strong>and</strong> Georgia<br />
reached 80,000,000 lb (16 364 mt)/yr. Annual exports generally averaged about half<br />
of total domestic <strong>production</strong> from 1780 to 1850, despite particularly destructive hurricanes<br />
in many o f those years.<br />
n C<br />
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American <strong>Rice</strong> Industry; Historical Overview of Production <strong>and</strong> Marketing 73<br />
t im e o f t r a n s i t i o n , 1 8 5 0 -1 8 8 0<br />
The westward movement, new <strong>technology</strong>, <strong>and</strong> finally, the Civil War interceded again<br />
to alter the character o f U.S. rk e <strong>production</strong>. Steam engines, <strong>and</strong> prominently steam-<br />
powered pumps, facilitated the opening o f rice <strong>production</strong> along the Mississippi River<br />
in Louisiana, where water was pumped over the levees into rice fields. Mills also began<br />
to change to steam power. Roller mills, developed <strong>origin</strong>ally for wheat in the midwest,<br />
were adapted to rice. During the decade 1850-1860, <strong>production</strong> had vshifted heavily<br />
to Louisiana's Mississippi delta, <strong>and</strong> New Orleans had becom e the center o f new<br />
U.S. milling <strong>and</strong> marketing activities (WiUdnson, 1848; Babineaux, 1967). Exports o f<br />
U.S. rice, despite intermittent fluctuations, were remarkably stable for the 100 years<br />
between 1760 <strong>and</strong> 1860, averaging about 60 million pounds (27,210 m t). The industry<br />
recorded exceptional exports in 1827 <strong>and</strong> 1828 with 105 <strong>and</strong> 103 m illion pounds<br />
(47 618 <strong>and</strong> 4 6711 m t), respectively, <strong>and</strong> the all-time antebellum record for exports<br />
occurred in 1835, with 127,790,000 lb (57 953 m t) shipped (Table 1.3.1).<br />
The U.S. Civil War (1861-1865), the end o f slavery, <strong>and</strong> the introduction o f<br />
wage labor, as well as the lack o f available capital, created serious problems for the<br />
U.S. rice industry between 1865 <strong>and</strong> 1880. <strong>Rice</strong> <strong>production</strong> in the older areas of<br />
South Carolina <strong>and</strong> Georgia declined rapidly. Production after the Civil War was<br />
concentrated on small acreages in Louisiana along the Mississippi River <strong>and</strong> that<br />
<strong>production</strong> was threatened by eroding levees <strong>and</strong> flood devastation (W ilkinson, 1848;<br />
Babineaux, 1967).<br />
BEGINNING OF THE MODERN INDUSTRY, 1 8 8 0 -1 9 0 0<br />
American rice cultivation might have come to an end in the latter part o f the nineteenth<br />
century but for an unusual com bination o f events, including (1) the com <br />
pletion o f a southern transcontinental railroad across Louisiana <strong>and</strong> Texas, (2) the<br />
availability <strong>and</strong> distribution o f cheap <strong>and</strong> previously uncultivated l<strong>and</strong>, (3) the introduction<br />
o f new steam-powered farm equipment, <strong>and</strong> (4) the immigration o f wheat<br />
farmers from the American midwest into the southwestern prairies. The com bination<br />
served to revolutionize the U.S. rice industry, whose modern period began in the latter<br />
decades o f the nineteenth century.<br />
The first southern transcontinental railroad was completed from New Orleans<br />
westward about 1883 <strong>and</strong> became a part of the Southern Pacific Railroad in 1885. An<br />
abundance o f cheap coastal prairie in southwestern Louisiana <strong>and</strong> southeastern Texas<br />
became available for settlement <strong>and</strong> sale. Rafli'oad agents <strong>and</strong> private entrepreneurs<br />
such as S. L. Cary, Jabez B. Watkins, <strong>and</strong> Seaman A. Knapp came to Louisiana from<br />
the grain-producing areas o f the midwestern United States to develop <strong>and</strong> sell agricultural<br />
l<strong>and</strong>s. The Southern Pacific Railroad made Cary its northern im m igration<br />
agent. Cary recruited prospective farmers, primarily in Iowa, Illinois, <strong>and</strong> Kansas.<br />
The railroads advertised the region as a “farm er’s mecca.” L<strong>and</strong>s in the region could<br />
be purchased for as little as 12 cents an acre <strong>and</strong> a 160-acre (395-ha) farm for as little<br />
as $14 down. Jabez Bunting Watldns, from Kansas, became the agent for a London-<br />
based l<strong>and</strong> syndicate called the North American L<strong>and</strong> <strong>and</strong> Tim ber Company. The<br />
syndicate purchased 1.5 m illion acres (3.7 x 10^ ha) o f l<strong>and</strong> located in southwestern<br />
Louisiana from the state <strong>and</strong> federal governments (Delavan, 1963). Midwestern grain
w<br />
É<br />
74 Origin <strong>and</strong> History<br />
TABLE 1.3.1.<br />
Exports <strong>and</strong> Export Prices of <strong>Rice</strong> Shipped from the United States, 1812’-186Q<br />
Year<br />
Exports<br />
(1000 lbs)<br />
Price<br />
(cents/lb)<br />
Year<br />
Exports<br />
(1000 lbs)<br />
Price<br />
(cents/lb)<br />
Year<br />
Exports<br />
(1000 lbs)<br />
Price<br />
(cents/lb)<br />
1712-16<br />
(average) 3 144 1767 68 267 2.2 1819 42998 3.9<br />
1717 3 187 — 1768 67 234 2.2 1820 52 933 2.8<br />
1718 3190 .—. 1769 75 492 2.2 1821 52 253 3.0<br />
1719 5 444 2.2 1770 76511 3.4 1822 60 819 3.0<br />
1721 8 752 1.0 1771 70 000 3.4 1823 67 937 2.8<br />
1724 7 094 .—. 1772 68 078 3.4 1824 58 209 3.3<br />
1725 9212 — 1723 62 538 — 1825 66 638 2.9<br />
1726 10 754 — 1782 12112 — 1826 80111 2.9<br />
1727 11962 — 1783 30 987 — 1827 105 011 2.5<br />
1728 12 954 —■ 1784 31857 — ■ 1828 102982 2.4<br />
1729 16 689 — 1785 32 929 — 1829 78418 2.5<br />
1730 19 744 1.4 1786 32 598 — 1830 69 910 3.0<br />
1731 18 534 .—. 1788 50 000<br />
—<br />
1831 72196 3.0<br />
1732 25 363 — 1789 60 507 2.9 1832 86498 3.2<br />
1733 15 162 — 1790 74136 2.6 1833 73 132 2.9<br />
1734 22 866 .—. 1791 85 057 2.3 1834 66 511 3.3<br />
1735 26 485 — 1792 80 767 2.9 1835 127 790 2.0<br />
1736 21413 2.9 1793 69 893 2.7 1836 63 650 4.0<br />
1737 17162 .—■ 1794 83116 3.5 1837 42 629 4.4<br />
1738 35 742 1.9 1795 78 623 5.9 1838 55 992 4.4<br />
1739 45 555 2.4 1796 36 067 — 1839 60996 3.2<br />
1740 4 0 4 4 7 2.7 1797 75146 — 1840 60 970 3.3<br />
1741 23 098 — 1798 66 359 — 1841 68 770 2.8<br />
1742 36 078 1,9 1799 - 67 234 — 1842 64 060 2.6<br />
1743 40 389 1.3 1800 56 920 — 1843 80 829 2.7<br />
1744 29 814 0.9 1801 47 893 1844 71173 3.0<br />
1745 27 051 0.9 1802 49103 5.0 1845 74404 3.5<br />
1746 27 073 2.2 1803 47031 4.9 1846 86656 4.2<br />
1747 27 566 1.6 1804 34098 5,0 1847 60 242 3.9<br />
1748 20 517 1.9 1805 61576 4.3 1848 77 317 3.3<br />
1749 24111 — 1806 56 815 4.2 1849 76241 3.5<br />
1750 30 086 1.8 1807 5 537 4.0 1850 63 354 3.4<br />
1751 39217 3.4 1808 70144 3.0 1851 71840 3.4<br />
1752 17 761 2.2 1809 78 805 3.3 1852 40 624 4.1<br />
1753 52 341 1.7 1810 71614 3.3 1853 63 073 4.2<br />
1754 48 389 1.9 1811 46 314 3.1 1854 39422 4.3<br />
1758 25 942 — 1812 72 506 4.1 1855 67616 3.5<br />
1759 30 403 2.2 1813 6 886 3.3 1856 68 323 3.4<br />
1760 52 342 1,8 1814 77 549 3.6 1857 58122 3,2<br />
1761 43 592 1.5 1815 82 706 4,3 1858 77070 2.9<br />
1762 50 350 2.4 1816 47 578 5.0 1859 81633 3.2<br />
1763 50 921 2.0 1817 52 909 6.1 1860 43 512 3.2<br />
1764 53 646 2.5 1818 45 914 4.6<br />
Source: Lewis Cecil Gray, H istory o f Agriculture in the Southern United States to I860 (Washington, DC: Carnegie Institution,<br />
1932; rpt, Gloucester, MA; Peter <strong>Smith</strong>, 1958), Vol, 2, p. 1030.
American Ríce Industry: Historical Overview of Produtlion <strong>and</strong> Marketing 75<br />
■Sí<br />
ft<br />
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mffirt fíth tufn»i M l>r<br />
. y, iitt' fWíl/ ' i X . Íff(n^fiígfíiu!/U nf á t1rí>tJÍiU^<br />
Figure 1.3.4, Water rice mili. (From Drayton, 1802.)<br />
<strong>and</strong> corn farmers, attracted by the lure o f cheap l<strong>and</strong> in the fertile, virgin prairies o f<br />
the central Gulf coast, <strong>and</strong> suffering from unusual drought <strong>and</strong> hard winter freezes<br />
in the midwest, came to Texas <strong>and</strong> Louisiana in large numbers, bringing with them<br />
their steam engines, steam tractors, mechanical harvesters, <strong>and</strong> general know-how of<br />
mechanized farming obtained from their corn <strong>and</strong> grain farm ing experiences (Figures<br />
1.3.4 to 1.3.6). They discovered tliat the corn <strong>and</strong> grain grown on the midwestern<br />
prairies did not prosper on the southern coastal prairies, but that rice would. The<br />
Southern Pacific Railroad advertised that, “rice is raised at about the same expense<br />
as wheat in the North, can be sown <strong>and</strong> harvested with the same machinery, <strong>and</strong> the<br />
average value o f the crop is more than double” (Cary, 1886, 1910; Southern Pacific<br />
Railroad, 1901; Ginn, 1940).<br />
Maurice Brien successfully adapted a wheat twine binder to rice harvesting in<br />
1884. Records o f the Southern Pacific Railroad indicate that one twine binder was<br />
shipped to Louisiana in 1884, 200 in 1887, <strong>and</strong> 1000 in 1890. William Deering <strong>and</strong><br />
Company began to manufacture a harvester especially adapted for rice in 1888. Steam<br />
tractors <strong>and</strong> steam threshers, <strong>and</strong> gang plows, previously unknown on Louisiana <strong>and</strong><br />
Texas farms, were brought into the southwest specifically for the development o f rice<br />
culture. Midwestern grain farmers <strong>and</strong> mechanized agriculture revolutionized <strong>and</strong><br />
greatly exp<strong>and</strong>ed the southern rice industry.
76 Origin <strong>and</strong> History<br />
= ...<br />
Figure 1.3.5. Harvesting rice in the Louisiana rice fields about 1882. (From the Southwestern<br />
' Archives <strong>and</strong> Manuscripts Collection, University of Southwestern Louisiana, Lafayette, Louisiana.)<br />
But, in fact, despite low l<strong>and</strong> costs, the capital improvements required for rice cultivation<br />
considerably exceeded those required for wheat <strong>and</strong> corn. Seaman A. Knapp<br />
left the presidency o f Iowa State College to join Watkins’ syndicate as a farm specialist<br />
in 1885, <strong>and</strong> in 1889 he organized his own l<strong>and</strong> company, called the Southern Real<br />
Estate, Loan <strong>and</strong> Guaranty Company, which marketed some half a million acres (1.2 x<br />
10^ ha) o f l<strong>and</strong> in Calcasieu Parish, Louisiana. Knapp promoted experimental farms,<br />
found improved rice cultivars, <strong>and</strong> in many other ways assisted in the development o f<br />
the industry. He estimated that in 10 years, Louisiana rice farmers spent "no less than<br />
$675,000 for binders, steam threshers <strong>and</strong> mowers, gang plows, <strong>and</strong> riding cultivators”<br />
(Anonymous, 1892; Bailey, 1945).” Investments in levees, canals, mills, pumping<br />
systems, <strong>and</strong> transportation were far greater.<br />
Developments in Texas followed closely those in Louisiana. As in Louisiana, some<br />
rice had been grown for local consumption, usually by settlers who had moved across<br />
the Sabine River from Louisiana. David French is credited with raising tlie first rice<br />
crop in Texas, near Beaum ont, in 1863. Texas’s first commercial crop, on 200 acres<br />
(494 ha) o f l<strong>and</strong> near Beaum ont, was grown by Edgar Carruthers, Louis Bordages,<br />
<strong>and</strong> Dan Wingate in 1886 (Stratton, n.d.; Scanlon, 1954). This crop was shipped by<br />
rail to New Orleans for milling.<br />
The existence o f an established rice milling center in New Orleans, founded when<br />
rice <strong>production</strong> began to flourish along the Mississippi River just prior to the Civil<br />
War, faciltiated the early development o f the industry in Louisiana <strong>and</strong> Texas. The new<br />
industry, however, soon outgrew the New Orleans mills. In addition, the m onopolistic<br />
position o f the New Orleans mills, the toll milling system then in vogue, various price<br />
control mechanisms o f tlie mills, <strong>and</strong> inadequate storage facilities in New Orleans<br />
began to stifle expansion. The longer distance to the New Orleans mills created a<br />
proportionately greater cost to Texas rice producers. In 1892, Joe E. Broussard added<br />
rice milling machinery to an existing gristmill <strong>and</strong> initiated the Texas rice milling<br />
industry, paving the way for expansion of the industry throughout southeastern Texas.<br />
Then, in a rare reversal o f what might be regarded as traditional railroad policy, the<br />
Southern Pacific Railroad levied lower rates on milled rice to New Orleans than on
%<br />
American <strong>Rice</strong> Industry; Historical Overview of Production <strong>and</strong> Marketing 77<br />
Figure 1.3.6. {a) Case steam engine, 1870; (b) Wood Brothers steam tractor,<br />
Des Moines, Iowa, 1913. (From author's personal photographic collection.)<br />
rough rice, giving prairie mills a price advantage <strong>and</strong> thus ending the New Orleans<br />
control over rice milling (Ginn, 1940). <strong>Rice</strong> <strong>production</strong> spread rapidly throughout<br />
Louisiana <strong>and</strong> Texas.<br />
By 1895 there were almost 300,000 acres (741,300 ha) o f rice under cultivation in<br />
the United States, m ost o f that in Louisiana. The railroad carried rough rice to established<br />
mills <strong>and</strong> markets in New Orleans <strong>and</strong> from there to world markets. By 1903,<br />
Louisiana had 376,500 acres (930,332 ha) <strong>and</strong> Texas had 234 200 acres (578 708 ha)
W \.<br />
78 Origin <strong>and</strong> History<br />
in rice. <strong>Rice</strong> <strong>production</strong> exp<strong>and</strong>ed westward as far as Houston, <strong>and</strong> by World W ar I<br />
moved west o f Houston into Colorado, Victoria, <strong>and</strong> Calhoun counties. Until 1924,<br />
Jefferson County (surrounding Beaumont) produced the m ajority o f the Texas rice<br />
crop. Meanwhile, rice cultivation in the older rice-producing areas along the Mississippi<br />
River, <strong>and</strong> in South Carolina, declined. <strong>Rice</strong> <strong>production</strong> in South Carolina, about<br />
1.7 million bushels in 1899, dropped to less than half a million bushels by 1909, <strong>and</strong><br />
ceased to exist by 1929. But even by 1903, the newly opened rice fields in the prairies<br />
of Louisiana <strong>and</strong> Texas accounted for 99.2% o f the rice acreage in the United States.<br />
In that year Louisiana had 376,500 acres (929,955 ha) under cultivation, <strong>and</strong> Texas<br />
had 234200 acres (578474 ha).<br />
Significant contributions to the expansion o f rice <strong>production</strong> during the last<br />
decade o f the nineteenth century were adaptations <strong>and</strong> innovations in the development<br />
o f canal <strong>and</strong> irrigation systems. In the 1890s, farmers began experimenting<br />
with deepwater wells powered by improved steam-driven pumps which serviced fields<br />
through a system o f elevated canals. Canal <strong>and</strong> l<strong>and</strong> development companies began<br />
to offer farmers dependable supplies o f fresh water for a share o f the crop (usually<br />
one-fourth) or for a cash rental fee (Gregory, 1904; Babineaux, 1967). M echanization<br />
<strong>and</strong> m odern irrigation systems changed the U.S. rice industry into something wholly<br />
different than that which it had been during the previous 200 years.<br />
A NEW CENTURY AND A NEW DEAL, 1900-1 9 4 5<br />
The first decades o f the twentieth century brought improved cultivars, exp<strong>and</strong>ed<br />
<strong>production</strong>, marketing refinements, <strong>and</strong> new problems. New, higher-producing <strong>and</strong><br />
better-milling rice strains were developed <strong>and</strong> introduced. Seaman A. Knapp received<br />
a special commission as a plant explorer from the U.S. Department of Agriculture to<br />
seek new rice genotypes, He went to Japan <strong>and</strong> returned with what becam e known as<br />
Kiushu (Kyushu) or Japan rice, which markedly reduced mill losses. Later, Solom on<br />
Wright, a midwesterner relocated in Crowley, Louisiana, perfected the Blue Rose <strong>and</strong><br />
other improved cultivars. Medium- <strong>and</strong> long-grain varieties were preferred by U.S.<br />
consumers <strong>and</strong> long-grain rice began to dominate southern rice <strong>production</strong> (Bailey,<br />
1945; Babineaux, 1967).<br />
There were, of course, conflicts, problems, <strong>and</strong> growing pains in the new rice<br />
industry. In response to the m onopolistic practices o f the New Orleans mills <strong>and</strong> the<br />
more favorable rates being provided the railroads for milled rice to New Orleans <strong>and</strong><br />
Gulf coast ports, prairie rice farmers began building private <strong>and</strong> cooperative mills<br />
adjacent to the areas o f <strong>production</strong>. They negotiated with the railroads for rates, <strong>and</strong><br />
by 1910, New Orleans was virtually out o f the rice business but for shipping milled<br />
rice through the port o f New Orleans, <strong>and</strong> through its role as a financier o f rural<br />
banks. <strong>Rice</strong> mills began to be constructed prominently in Lake Charles, Louisiana, <strong>and</strong><br />
Beaumont <strong>and</strong> Houston, Texas. As the rice industry surged, l<strong>and</strong> prices rose, forcing<br />
prospective rice farmers into new <strong>and</strong> lower-priced l<strong>and</strong>s in Texas <strong>and</strong> Arkansas. By<br />
1910, Texas <strong>and</strong> Louisiana farmers produced 90% (10 million bushels) o f the U.S. rice<br />
crop. Another million bushels was being produced in Arkansas, which a decade earlier<br />
had no <strong>production</strong> (Ginn, 1940; Gregory, 1904; Bailey, 1945; Babineaux, 1977).<br />
Developments in Arkansas duplicated in many respects those in Louisiana <strong>and</strong><br />
Texas two decades earlier. Arkansas <strong>production</strong> drew directly upon the experience o f
Amerícqn Ríce Industry; Historical Overview of Production <strong>and</strong> Marketing 79<br />
Louisiana rice growers. Prairies in the central eastern portion o f the state were similar<br />
to those in the coastal prairies o f Louisiana <strong>and</strong> Texas. Located near Stuttgart <strong>and</strong><br />
Carlisle, the Arkansas prairies were largely uncultivated, virgin l<strong>and</strong>s in 1900. The<br />
area was sparsely settled <strong>and</strong> l<strong>and</strong> was cheap. Midwesterners again took advantage<br />
o f the situation. A survey taken in 1930 revealed that over 60% o f farmers in the<br />
rice-producing counties o f Arkansas came from Illinois, Iowa, Indiana, <strong>and</strong> Ohio<br />
(M cCorm ick, 1933).<br />
One o f these settlers in particular, W. H. FuUer, who moved near Carlisle, Arkansas,<br />
from Ohio in 1896, pioneered the development o f the Arkansas rice industry.<br />
FuUer traveled into the rice country o f Louisiana, investigated rice culture, <strong>and</strong> returned<br />
to drill an irrigation well <strong>and</strong> plant rice on his Arkansas farm in 1897. But<br />
his crop failed largely because o f pumping problems. Fuller then decided to move to<br />
Louisiana to learn the business. He rented a farm near Jennings in 1898 <strong>and</strong> began<br />
growing rice. In the process he sent as m uch inform ation as he could to Arkansas,<br />
<strong>and</strong> in 1902 helped arrange for an experimental rice crop on the farm of his Arkansas<br />
neighbor, John M orris. W ith the assistance o f the Arkansas Agricultural Experim<br />
ent Station, M orris <strong>and</strong> others organized a local rice irrigation company, but again<br />
the crop failed. The would-be rice farmers learned from their mistakes (Tait, 1904;<br />
, Spicer, 1964).<br />
The next year, 1904, the Arkansas Agricultural Experiment Station continued to<br />
work with rice cultivation <strong>and</strong> planted a 160-acre (395-ha) plot o f virgin prairie l<strong>and</strong><br />
in Lonoke County. T he experimental plot yielded an average o f 65 bushels an acre.<br />
Meanwhile, Fuller returned to his Arkansas farm, <strong>and</strong> he, M orris, <strong>and</strong> other farmers<br />
also planted successful rice crops in 1904. Commercial <strong>production</strong> in Arkansas thus<br />
began. But once the techniques o f <strong>production</strong> were mastered, milling <strong>and</strong> marketing<br />
problems confronted Arkansas growers. Only the development o f local milling facilities<br />
could support exp<strong>and</strong>ed <strong>production</strong>. In 1906, local merchants <strong>and</strong> bankers in<br />
Stuttgart built the state’s first rice mill. By 1910, four additional mills were in operation.<br />
Newly arriving Arkansas farmers began a massive move into rice. Between 1899<br />
<strong>and</strong> 1909, rice <strong>production</strong> in tlie central prairies o f Arkansas jum ped from 310 bushels<br />
to over 1.25 m illion bushels (Table 1.3.2) (Tait, 1904; U.S. Bureau o f the Census, 1930;<br />
Spicer, 1964).<br />
TABLE 1.3.2. <strong>Rice</strong> Production (Bushels)" by States, 1879-1909<br />
1879 1889 1899 1909<br />
South Carolina 1875 292 1091329 541 570 122465<br />
Louisiana 834112 2721059 6213397 10839973<br />
Texas 2236 3 900 258520 8 991745<br />
Arkansas — 256 310 1282830<br />
Source: U.S. Census, 1930, Part III, Agriculture, p. 759.<br />
“In theory, a bushel o f rough rice weighs 45 lb (20.5 kg) <strong>and</strong> produces 27,8 lb (12.6 kg) of milled<br />
rice. Until almost 1890, vice was measured in barrels of 600 lb, <strong>and</strong> then for several decades in<br />
barrels o f350 lb. By 1900 the introduction of burlap <strong>and</strong> jute bagging resulted in a barrel or sack<br />
of rough rice weighing 162 lb, which produced a “pocket” of milled rice, also sacked' of 100 lb. A<br />
barrel or sack of rough rice could be expected to mill 100 lb of finished or polished rice, 30 lb of<br />
diaff, 22 lb of bran, <strong>and</strong> 10 lb of “polish” or fine particles.
Origin <strong>and</strong> History<br />
Several new elements were introduced in the first two decades o f the twentieth<br />
century which had long-term impacts on the American rice industry. New long-grain<br />
cultivars were imported from Honduras that becam e known as Honduras rice. Seaman<br />
A. Knapp sent new medium-grain cultivars o f rice from Kyushu, Japan in 1902,<br />
one called Chinriki, <strong>and</strong> the other Watera (or W ataribune). Wataribune becam e the<br />
preferred crop for rice <strong>production</strong> that began in California about 1915. Sol W right,<br />
in Louisiana, also introduced new medium-grain cultivars, including Early Prolific, a<br />
quick-maturing strain that became very successful. In addition, the U.S. Department<br />
o f Agriculture, through its agricultural experiment stations organized in 1914, effectively<br />
became a research com ponent o f the American rice industry. State agricultural<br />
experiment stations established research centers devoted primarily to rice studies in<br />
each o f the m ajor rice-producing states; Louisiana, Texas, Arkansas, <strong>and</strong> California.<br />
These centers continue to make enorm ous contributions to the industry (Ai'kansas<br />
Agricultural Experiment Station, 1904; Texas Agricultural Experiment Station, 1912;<br />
Anderson, 1977).<br />
Stimulated in part by the heavy influx o f Asian immigrants into California, who<br />
comprised a large consumer market for rice, the California Agricultural Experiment<br />
Station planted experimental plots o f long-grain rice in 1893, 1894, <strong>and</strong> in 1896 on<br />
Union Isl<strong>and</strong> in the San Joaquin River near Stockton. In each season, the rice failed<br />
to produce heads. In 1906, W illiam W. Mackie, who was conducting tests to study the<br />
resistance o f various crops to the alkali soils in the San Joaquin Valley, experimented<br />
with rice grown from a short-grain Japanese cultivar brought in from Hawaii. The<br />
rice headed nicely, which convinced Mackie that the right cultivars of rice could be<br />
grown in the San Joaquin Valley, He then went to Louisiana <strong>and</strong> Texas to learn about<br />
rice culture <strong>and</strong> returned to California hoping to get funding to experiment with rice<br />
cultivation. Secretary of Agriculture James W. W ilson, however, would not approve<br />
the special funding on the grounds that previous experiments with rice in California<br />
had failed (Bleyhl, 1955).<br />
Mackie, however, persisted. Lie obtained funds from the Sacramento Valley Development<br />
Association for the purchase o f short-grain Kiushu seed from Crowley,<br />
Louisiana, <strong>and</strong> planted several small plots o f rice on the grounds o f the state asylum<br />
in Stockton <strong>and</strong> on a private farm near Elk Grove in Sacramento County. The rice<br />
grew, <strong>and</strong> headed, but the heads failed to fill. Maclde believed that the cool nights<br />
were the contributing factor. Independent California farmers in Glenn <strong>and</strong> Butte<br />
counties also attempted to grow rice, but without success. Finally, Mackie, receiving<br />
support from the Biggs (California) Chamber o f Commerce, planted two plots o f rice<br />
totaling 23 acres (57 ha), one in Honduras rice <strong>and</strong> the other in Kiushu. The long-<br />
grain Honduras failed to mature, but the Kiushu yielded 3000 Ib/acre (3360 kg/ha)<br />
(Bleyhl, 1955).<br />
On the eve o f that success, M ackie’s l<strong>and</strong>-utilization project, <strong>and</strong> Mackie, were<br />
transferred to the Bureau of Plant Industry from the Bureau o f Soils, <strong>and</strong> his experiments<br />
with rice ceased. In 1909, however, the U.S. Departm ent o f Agriculture<br />
assigned Charles E. Chambliss o f the Office of Cereals Investigations in the Bureau<br />
o f Plant Industry to continue Mackie’s experiments. After hundreds o f tests, Cham <br />
bliss decided to move to Richvale, California, where he helped farmers organize the<br />
Sacramento Valley Grain Association, which provided financial support for further<br />
rice experiments. By the outbreak o f World War I, the feasibility o f profitably producing<br />
short-grain rice in California had been proven. In 1914, California producers
American <strong>Rice</strong> Industry: Historical Overview of Production <strong>and</strong> Marketing 81<br />
delivered 405j000 bags (hundredweight) o f rice, 3.8% o f the U.S. crop. W artime dem<strong>and</strong>s<br />
caused California rice <strong>production</strong> to mushroom while <strong>production</strong> on the<br />
prairie regions o f Arkansas, Louisiana, <strong>and</strong> Texas more than doubled. In 1918, U.S.<br />
<strong>production</strong> reached 18 million bags, while California <strong>production</strong> totaled 3.1 m illion<br />
bags, 17% o f total <strong>production</strong>. Chambliss, incidentally, subsequently resigned<br />
from the Departm ent o f Agriculture, became a successful rice grower, <strong>and</strong> from 1924<br />
through World War II served as head o f the California <strong>Rice</strong> Growers' Association<br />
(Bleyhl, 1955).<br />
Under the influence o f the Farmers’ Alliance <strong>and</strong> tlie subsequent Populist (People’s<br />
Party o f America) movements o f the late nineteenth century, stimulated by the<br />
farm cooperative movement o f the twentieth century <strong>and</strong> encouraged by the agricultural<br />
experiment stations <strong>and</strong> the Agricultural Extension Service, U.S. rice growers<br />
<strong>and</strong> millers began to organize into state, regional, <strong>and</strong> national trade associations such<br />
as tlie American <strong>Rice</strong> Growers Cooperative Association; the Southern, Pacific, <strong>and</strong><br />
Delta <strong>Rice</strong> Growers; Texas, Louisiana, <strong>and</strong> Arlcansas growers <strong>and</strong> millers associations;<br />
the <strong>Rice</strong> Millers’ Association; <strong>and</strong> later the <strong>Rice</strong> Council for M arket Development.<br />
These associations helped create grades <strong>and</strong> market st<strong>and</strong>ards, established st<strong>and</strong>ard<br />
trade contracts <strong>and</strong> practices, <strong>and</strong> began to concentrate on the marketing o f the growing<br />
volumes o f rice being produced on U.S. farms.<br />
Acreage planted to rice declined sharply after World War I, with 1.2 million acres<br />
harvested in 1920 <strong>and</strong> only 838,000 harvested in 1924. Although the 1920s generated<br />
some dislocations, the general attitude among rice farmers remained optim istic <strong>and</strong><br />
expansive, especially in California. <strong>Rice</strong> <strong>production</strong> moved into the lower bootheel<br />
o f Missouri in the 1920s <strong>and</strong> was somewhat revitalized along the Mississippi River in<br />
Louisiana. The Great Depression, marked by the collapse o f stock prices on Wall Street<br />
in October 1929, followed by the collapse o f the U.S. banking system <strong>and</strong> spiraling<br />
unemployment, wreaked havoc among U.S. farm industries, already suffering from<br />
market tremors <strong>and</strong> over<strong>production</strong>. The farm value o f rice dropped from $39 million<br />
to $17 m illion in the three years following the market collapse on Wall Street In 1929,<br />
before tlie stock market crash. Congress approved the Agricultural Marketing Act,<br />
creating the Federal Farm Board, which would administer a $500 million revolving<br />
fund that could be loaned to producer cooperatives so that they m ight purchase<br />
commodities on tlie open market <strong>and</strong> store them, thus relieving farm surpluses <strong>and</strong><br />
improving prices. The election o f President Franldin D. Roosevelt <strong>and</strong> the “New Deal”<br />
Dem ocratic administration resulted, among other things, in the passage o f the Agricultural<br />
Adjustment Act on May 12,1933, creating the Agricultural Adjustment Administration<br />
(AAA), which assumed, with substantial modifications, the programs o f<br />
the Federal Fai'm Board. Under the AAA, farmers entered into voluntary agreements<br />
with the governmental agency by which they agreed to reduce <strong>production</strong> <strong>and</strong> marketing<br />
by accepting acreage allotments <strong>and</strong> marketing quotas, <strong>and</strong> the government<br />
agreed to support prices o f basic commodities, including rice, at a predetermined<br />
parity level (Benedict, 1953; Fite, 1954; Perkins, 1969).<br />
The needs <strong>and</strong> the response by rice farmers <strong>and</strong> millers to the crisis of the Great<br />
Depression differed from that o f other farmers, <strong>and</strong> the programs developed by the<br />
New Deal affected rice differently than other farm commodities. The Depression, <strong>and</strong><br />
related federal farm legislation, changed the general structure <strong>and</strong> style o f U.S. agriculture,<br />
<strong>and</strong> o f the rice industry in particular. World War II <strong>and</strong> the postwar reconstruction<br />
then brought tremendous new global dem<strong>and</strong>s for U.S. rice. Between 1946 <strong>and</strong>
82 Origin <strong>and</strong> History<br />
1954, acreage in rice rose from 1.5 m illion to 2.5 million. Production doubled from 32<br />
million hundredweight to over 64 million (Reid <strong>and</strong> Gaines, 1974). Traditional cotton<br />
l<strong>and</strong>s along the lower Mississippi River were converted to rice.,<br />
Rex L, Kimbriel, a Mississippi delta cotton farmer, first experimented with a small<br />
crop o f rice in 1947, <strong>and</strong> in 1948, with four neigliboring farmers, planted 400 acres<br />
(988 ha) of rice. Pumping problems <strong>and</strong> an early frost ruined their crop, but the<br />
potential was clear. In 1949, Kimbriel <strong>and</strong> other delta farmers planted 1800 acres<br />
(4448 ha) in rice, built their own rices dryer, <strong>and</strong> after political negotiations with<br />
Congress <strong>and</strong> the AAA won enlarged acreage allotments for rice in Mississippi. In<br />
1953, Mississippi farmers planted 70,000 acres (172 070 ha) <strong>and</strong> produced 1.8 million<br />
hundredweight o f rough rice (Kimbriel, n.d.).<br />
Under the impetus o f federal farm programs, the globalization of the U.S. economy,<br />
<strong>and</strong> improved financial, management, <strong>and</strong> scientific practices, the infrastructure<br />
o f U.S. agriculture, <strong>and</strong> o f the rice industry in particular, changed markedly after<br />
World War II. But the overall composite of the industry in tlie twentieth century<br />
was remarkably similar to what it had been in the eighteenth century. Ralph S. Newman,<br />
fhen president o f American <strong>Rice</strong>, Inc., a centralized rice milling <strong>and</strong> m arketing<br />
cooperative serving approximately 1800 rice farmers in the Gulf coast area o f<br />
Texas <strong>and</strong> Louisiana, described the U.S. rice industry in contem porary times as an<br />
international agribusiness preoccupied with overseas events (Newman, 1982). That<br />
profile has changed little since 1700. The modern rice industry, as was the colonial<br />
industry, is an international agribusiness, but far more so than in earlier days, it is<br />
related intrinsically to government policy <strong>and</strong> decisions.<br />
The Foreign Agricultural Service (FAS), established by Congress in 1930, became<br />
a partner with the U.S. rice industry in creating a global inform ation network to provide<br />
data <strong>and</strong> analyses o f worldwide agricultural <strong>production</strong>, trade, marketing, prices,<br />
<strong>and</strong> consumption. In 1957, the industry established what became the <strong>Rice</strong> Council for<br />
Market Development, which was designed to provide liaison <strong>and</strong> cooperation among<br />
producers, millers, allied industries, <strong>and</strong> government agencies in the development of<br />
botli domestic <strong>and</strong> international m arket opportunities. Research extended beyond<br />
the earlier experimental farm programs <strong>and</strong> technical studies o f drying, milling,<br />
<strong>and</strong> storage, <strong>and</strong> began to focus on rice diseases <strong>and</strong> genetic enhancement. In 1938,<br />
Congress established four regional research laboratories, two o f which, the Southern<br />
Regional Research Laboratory in New Orleans <strong>and</strong> the Western Regional Research<br />
Laboratory in Albany, California, becam e heavily involved in rice research work. A<br />
group headed by Joseph T. Hogan, a principal research chemist in the food crops<br />
laboratory o f the Southern Regional Research Laboratory, moved from research on<br />
impi'oved com bining techniques, to rice drying, to grain storage <strong>and</strong> food preparation<br />
studies. Associated studies in chemical milling <strong>and</strong> food storage <strong>and</strong> preparation were<br />
conducted by the Agricultural Research Division of the Bureau o f Agricultural <strong>and</strong> In <br />
dustrial Chemistry in New Orleans. Robert K. Webster o f the University o f California-<br />
Davis made significant contribution in the control of stem rot. J. W. Sorensen, Jr., B. D.<br />
Webb, G. W. Evers, J. P. Craigmiles, <strong>and</strong> R<strong>and</strong>all Stelly o f the Texas Agricultural Experiment<br />
Station <strong>and</strong> Extension Service were among the many agricultural scientists<br />
who made significant contributions in rice research, as did D. Troy Mullins <strong>and</strong> A, W.<br />
Woodward o f the University o f Arkansas, Jenldn W. Jones [a geneticists <strong>and</strong> head of<br />
the Biggs (California) <strong>Rice</strong> Experim ent Station for many years], <strong>and</strong> L. E. Johnson<br />
<strong>and</strong> J. Norman Efferson of Louisiana State University (Anonymous, 1978).
American <strong>Rice</strong> Industry; Historical OverView of Production <strong>and</strong> Marketing 83<br />
In 1953 the Rockefeller Foundation invited Efferson to investigate the possibilities<br />
o f establishing a rice research center to stimulate the <strong>production</strong> o f rice in Asia. This<br />
study led; 10 years later, to the opening o f the International <strong>Rice</strong> Research Institute<br />
(IRRI) in the Philippines. Established with a $10 million Ford Foundation grant<br />
<strong>and</strong> $600,000 from the Rockefeller Foundation, the institute becam e a global laboratory<br />
for the development o f high-yielding, disease-resistant strains o f early-maturing<br />
“m iracle” rice (Efferson, 1967). The governments of the United States, Canada, the<br />
United Kingdom, lap an, the Netherl<strong>and</strong>s, West Germany, <strong>and</strong> Australia, as well as<br />
tire World Bank <strong>and</strong> United Nations, became leading contributors to the institute’s<br />
scientific rice research (J. Norman Efferson, interview). While the U.S. rice industry<br />
had always been international in its focus, during the second half o f the twentieth<br />
century, the industry became even more globally interrelated <strong>and</strong> integrated in terms<br />
o f research <strong>and</strong> marketing.<br />
Under the impetus of scientific research <strong>and</strong> improved <strong>technology</strong>, yields o f rice<br />
harvested in the United States rose from approximately 3500 Ib/acre (3920 kg/ha) in<br />
1960 to in excess o f 5500 Ib/acre (6160 kg/ha) in 1990 (Figure 1.3,7). Although total<br />
U.S. <strong>production</strong> slipped to about 1.5% o f global <strong>production</strong> between 1970 <strong>and</strong> 2000,<br />
the U.S. share o f rice exports has generally averaged 20% o f the world total, a position<br />
that has been remarkably consistent over the past 300 years.<br />
At the close o f the twentieth century, U.S. rice entered the markets o f m ost nations<br />
o f the world. Regionally,, the single largest consumer o f U.S. rice is North America, including<br />
Mexico, Canada, <strong>and</strong> the United States. In 1999, after years o f virtually excluding<br />
U.S. rice from her markets, Japan became the second-largest importer. Nations<br />
comprising the European Union have historically been m ajor consumers o f U.S. rice,<br />
as have the Caribbean nations. Cuba consumed a dommant share o f the rice exported<br />
to the Caribbean until the Cuban Revolution ended U.S. <strong>and</strong> Cuban trade. The Middle<br />
East, the fifth-largest importer o f rice at the close o f the century, developed as a m ajor<br />
market after World War II. The export o f U.S. rice to Central <strong>and</strong> South American<br />
nations has varied markedly through the decades, but those markets have m ost often<br />
been an im portant com ponent o f total exports. The Pacific Isl<strong>and</strong>s, China <strong>and</strong> Hong<br />
Kong, <strong>and</strong> North African <strong>and</strong> South Asian markets are marginal but have enorm ous<br />
potential. While those regions include the world’s leading producers o f rice, tliey often<br />
Figure 1.3.7.<br />
<strong>Rice</strong> harvest in Texas, 1990s. (Courtesy of the <strong>Rice</strong> Millers Association.)
Origiil <strong>and</strong> History<br />
consume more than is produced. At the close o f the twentieth century, the 10 leading<br />
export markets for U.S. rice, ranked by volume, were Japan, Mexico, Canada, Haiti,<br />
Saudi Arabia, Indonesia, the United Kingdom, the Russian Federation, the Republic<br />
o f South Africa, <strong>and</strong> Turkey (U.S. Bureau o f the Census, 200.0).<br />
REFERENCES<br />
Anderson, R. S. 1977. The relations between rice research <strong>and</strong> development <strong>and</strong> the<br />
rice industry o f the southern United States before 1945. Unpublished m anuscript<br />
Institute o f Comparative <strong>and</strong> Foreign Area Studies, University o f Washington,<br />
Seattle, WA.<br />
Anonymous. 1892. Louisiana’s rice crop. Biographical <strong>and</strong> Historical Memoirs o f Louisiana,<br />
Vol. 2. Goodspeed Publishing, Chicago.<br />
Anonymous. 1978. <strong>Rice</strong> technical work group holds February session. R icef (Apr.).<br />
Arkansas Agricultural Experiment Station. 1904. Annual Report of Irrigation <strong>and</strong><br />
Drainage Inspection, 1904. University o f Arkansas, Fayetteville, AK.<br />
Babineaux, L. P. 1967. A <strong>history</strong> o f the rice industry o f southwestern Louisiana. M.A.<br />
thesis. University of Southwestern Louisiana, Lafayette, LA.<br />
Bailey, J. C. 1945. Seaman A. Knapp, Schoolmaster of American Agriculture. Columbia<br />
University Press, New York.<br />
Benedict, M. R. 1953. Farm Policies of the United States, 1790-1950. Twentieth Century<br />
Fund, New York.<br />
Bleyhl, N. A. 1955. A <strong>history</strong> o f the <strong>production</strong> <strong>and</strong> marketing o f rice in California.<br />
Ph.D. dissertation. University o f Minnesota,<br />
Cary, S. L. 1886. The prairie region o f southwest Louisiana. Biennial Report of the<br />
Louisiana Commissioner of Agriculture (Apr.).<br />
Cary, S. L. 1910. The appeal o f Louisiana to the western farmer. Logical Point, 1 (O ct.).<br />
Delavan, W. 1963. The N orth American L<strong>and</strong> <strong>and</strong> Tim ber Company, Limited: some<br />
notes on its beginnings. Ark. Acad. Sei Proc., 17.<br />
Dethloff, H. C. 1988. A History of the Am erican <strong>Rice</strong> Industry, 1685-1985. Texas<br />
A&M University Press, College Station, Texas.<br />
Drayton, J. 1802. A View of South Carolina. W. P. Young, Charleston, SC.<br />
Efferson, J. N. 1967. Interview. By Henry C. D ethloff <strong>and</strong> Lawson P. Babineaux, Baton<br />
Rouge, LA, Jan, 17. Southwestern Archives <strong>and</strong> Manuscripts Collection, University<br />
o f Southwestern Louisiana, Lafayette, LA.<br />
Fite, G. C. 1954. George N. Peek <strong>and</strong> the Fight for Farm Parity. University o f Oklahoma<br />
Press, Norman, OK,<br />
Ginn, M. K. 1940. A <strong>history</strong> o f rice <strong>production</strong> in Louisiana to 1896. La. Hist. Q. 23<br />
(Apr.).<br />
Gray, L. C. 1932. History of Agriculture in the Southern United States to 1860, 2 vols.<br />
Carnegie Institution, Washington, D C (reprinted, Gloucester, MA: Peter <strong>Smith</strong>,<br />
1958).<br />
Gregory, W. B. 1904. <strong>Rice</strong> irrigation in Louisiana <strong>and</strong> Texas in 1903 <strong>and</strong> 1904, Annual<br />
Report of Irrigation <strong>and</strong> Drainage Investigation, 1904. Separate No. 7. U.S,<br />
Department o f Agriculture, Washington, DC.<br />
Kimbriel, R. L. n.d. Papers, Southwestern Archives <strong>and</strong> Manuscripts Collection, U niversity<br />
o f Southwestern Louisiana, Lafayette, LA.
America Kl Ríce Industry: Historical Overview of Production <strong>and</strong> Marketing 85<br />
Lawson, D. T. 1972. No Heir to Take Its Place: The Story of <strong>Rice</strong> in Georgetown County.<br />
<strong>Rice</strong> Museum, Georgetown, SC.<br />
Littlefield, D. C. 1981. <strong>Rice</strong> <strong>and</strong> Slaves: Ethnicity <strong>and</strong> the Slave Trade in Colonial South<br />
Carolina. Louisiana State University Press, Baton Rouge, LA.<br />
Lucas family papers. South Carolina Historical Society, Charleston, SC.<br />
M cCorm ick, T. C. 1933, Rural Social Organization in the <strong>Rice</strong> Area. Ark. Agric. Exp.<br />
Stn. Bull. 296, Fayetteville, AR.<br />
Mumford, L. 1961. The City in History: Its Origins, Its Transformations, <strong>and</strong> Its Prospects.<br />
Harcourt, Brace 8c World, New York.<br />
Newman, R. S., Jr„ 1982. The American rice industry. In H. C. D ethloff <strong>and</strong> 1. M.<br />
May, Jr. (eds.), Southwestern Agriculture: Pre-Columbian to Modem. Texas A8cM<br />
University Press, College Station, TX . ‘<br />
Perkins, V. L. 1969. Crisis in Agriculture: The Agricultural Adjustment Administration<br />
<strong>and</strong> the New Deal, 1933. University o f California Press, Berkeley, CA.<br />
Ramsay, D. 1858, History o f South Carolina from Its First Settlement in 1670 to the Year<br />
1808. W.J, Duffie, Newberry, SC.<br />
Reid, W. M. <strong>and</strong> J. P. Gaines. 1974, Seventy-five Years with the <strong>Rice</strong> Millers* Association,<br />
1899-1974. Washington, D.C.: <strong>Rice</strong> M illers’ Association.<br />
Salley, A. S., Jr. 1919. The introduction o f rice culture into South Carolina. Bull. Hist.<br />
Comm. S.C. 6.<br />
Scanlon, F. A. 1954. The rice industry o f Texas. M .S. thesis. University o f Texas, Austin,<br />
TX.<br />
Southern Pacific Railroad, Passenger Department. 1901. Southwest Louisiana Up to<br />
Date. Southern Pacific Railroad, Houston, TX.<br />
Spicer, J. M. 1964. Beginnings of the <strong>Rice</strong> Industry in Arkansas, n.p,<br />
Stratton, F. n.d. The Story of Beaumont. Hercules Printing <strong>and</strong> Book Co., Houston,<br />
TX.<br />
Tait, C. E. 1904, <strong>Rice</strong> irrigation on the prairie l<strong>and</strong> o f Arkansas. Annual Report of<br />
Irrigation <strong>and</strong> Drainage Investigation, 1904. Separate No. 7. U.S. Departm ent o f<br />
Agriculture, Washington, DC.<br />
TannahMl, R. 1973, Food in History. Stein Sc Day, New York.<br />
Texas Agricultural Experiment Station. 1912. Annual Report. Substation 4, College<br />
Station, TX.<br />
U.S. Bureau o f the Census. 1930. Agriculture. Vol. 3. Bureau o f the Census, Washing<br />
ton, DC.<br />
U.S. Bureau o f the Census, 2000. U.S. Exports ofRke, Calendar Year 1995-1999 <strong>and</strong><br />
Year to Date Comparisons. See http://gov/scrip[sw/bico.ide?doc=626.<br />
U.S. Bureau o f the Census. 1975. Historical Statistics of the United States: Colonial<br />
Times to 1970, 2 vols, U.S. Bureau o f tlie Census, Washington, DC,<br />
Wilkinson, R. A. 1848. Production o f rice in Louisiana. DeBow*s Rev. 6 (July).
d i o p t e r<br />
1.4<br />
Origin <strong>and</strong> Characteristics of<br />
U.S. <strong>Rice</strong> Cultivars<br />
David J. Mackill<br />
International <strong>Rice</strong> Research Institute<br />
Los Baños, Philippines<br />
Kent S. McKenzie<br />
California Cooperative <strong>Rice</strong> Research Foundation<br />
Biggs, California<br />
INTRODUaiON<br />
CLASSIFICATION OF RICE CULTIVARS<br />
DERIVATION OF U.S. RICE CULTIVARS<br />
Long-Grain Cultivars<br />
Medium- <strong>and</strong> Short-Grain Cultivars<br />
CHARACTERISTICS OF U.S. RICE CULTIVARS<br />
Agronomic Characteristics<br />
Grain Quality Characteristics<br />
FUTURE TRENDS<br />
REFERENCES<br />
INTRODUCTION<br />
Whereas rice culture had its U.S. beginnings in Carolina plantations during the seventeenth<br />
century, present cultivation in the southern states <strong>and</strong> California had its <strong>origin</strong>s<br />
at the turn o f the twentieth century. At this tim e, the U.S. Departm ent of Agriculture<br />
(USDA) began im porting rice cultivars from various sources for experimentation<br />
<strong>and</strong> breeding. Breeding programs in the United States over the past century have<br />
developed distinctive germplasm pools for long- <strong>and</strong> medium-grain types that are<br />
known for their excellent grain quality. The short- <strong>and</strong> medium-grain cultivars are<br />
typical o f the temperate japónica subspecies, while the long-grain cultivars represent<br />
a unique group o f tvopiail japónica types com bining excellent grain quality <strong>and</strong> high<br />
yield.<br />
<strong>Rice</strong>: Origin, History, Technology, <strong>and</strong> Production, edited by C. Wayne <strong>Smith</strong><br />
ISBN 0-471-34516-4 © <strong>2003</strong> John Wiley & Sons, Inc.<br />
B7
Origin <strong>and</strong> History<br />
CLASSIFICATION OF RICE CULTIVARS<br />
The germs Oryza consists of over 20 species which are organized into four complexes<br />
(Vaughan, 1994). The two cultivated species, Asian rice (O. sativa) <strong>and</strong> African rice<br />
(O. glaherrima), belong to the sativa complex <strong>and</strong> are diploids with the AA genome.<br />
There is some record o f cultivation o f glaberrima rices in the United States by slaves,<br />
who m ust have brought them from West Africa (Carney, 1998). However, only sativa<br />
rices are grown currently, <strong>and</strong> there is no evidence that any glaberrima rices contributed<br />
to the U.S, germplasm pool. The sativa rices are thought to be derived from<br />
the aquatic perennial species O. rufipogon (Oka, 1988). Wild relatives o f rice can<br />
hybridize with cultivated rice, which is thought to be a source o f weedy populations<br />
that are found growing near rice fields in Asia (Langevin et al., 1990). Red rice is a<br />
weedy form of O. sativa <strong>and</strong> is a m ajor constraint in direct-seeded rice <strong>production</strong><br />
areas, including the southern United States.<br />
M ost Asian rice cultivars can be classified into one o f the two m ajor subspecies,<br />
indica or japónica. Indica cultivars constitute the m ajority o f rice <strong>production</strong> worldwide,<br />
probably about 80% (Mackill, 1995). Traditionally, only the cultivars grown<br />
in temperate areas, such as northeastern Asia, Europe, California, <strong>and</strong> Australia, were<br />
considered japónica types. The javanica or bulu cultivars o f Indonesia were often classified<br />
as a separate group distinct from the indicas <strong>and</strong> japónicas. In addition, many<br />
cultivars grown under upl<strong>and</strong> (unflooded) conditions were considered similar to ja <br />
vanica cultivars. As early as the 1950s, however, Oka (1958) divided rice cultivars into<br />
continental <strong>and</strong> insular groups. He included indica cultivars in the form er <strong>and</strong> both<br />
the typical temperate japónica gnd javanica cultivars in the latter. This classification<br />
system was not widely accepted at the time, however, <strong>and</strong> many researchers considered<br />
the indica-japonica classification to be synonymous with tropical or temperate adaptation,<br />
respectively. Confusion remained over the distinction among tropical rices,<br />
with the javanica <strong>and</strong> upl<strong>and</strong> cultivars variously considered as indica types or as a<br />
separate javanica subspecies.<br />
These problems in classification o f tropical rice were greatly alleviated by the<br />
isozyme studies o f Second (1982) <strong>and</strong> Glaszmann (1987). In Glaszmann’s study, 15<br />
isozyme markers were used to classify 1688 rice cultivars. Six isozyme groups were<br />
formed, two m ajor groups which included the indica (group 1) <strong>and</strong> japónica (group<br />
6) cultivars, <strong>and</strong> four small intermediate groups. The japónica group included the<br />
typical short- <strong>and</strong> medium-grain cultivars from temperate regions, as well as tropical<br />
types that included the upl<strong>and</strong> <strong>and</strong> javanica cultivars with a range o f grain sizes <strong>and</strong><br />
shapes. Groups 2 to 4 were m inor groups consisting o f cultivars from eastern India <strong>and</strong><br />
Bangladesh. Group 5 included the im portant Basmati cultivars <strong>and</strong> other aromatic<br />
<strong>and</strong> premium quality rices. In the isozyme studies o f Glaszmann (1987), the temperate<br />
<strong>and</strong> tropical japónica types were indistinguishable. In a follow-up study (Glaszmann<br />
<strong>and</strong> Arraudeau, 1986), it was observed that the tropical <strong>and</strong> temperate types formed<br />
a continuum based on morphological characters.<br />
Since the groundbrealdng study o f Glaszmann (1987), numerous researchers<br />
have applied the more powerful DNA markers, such as RELPs <strong>and</strong> RAPDs, to the classification<br />
o f rice cultivars. Wang <strong>and</strong> Tanksley (1989), who classified 70 rice cultivars<br />
using 10 RFLP probes with five restriction enzymes, found general agreement with the<br />
results o f Glaszmann. Groups 1 to 5, however, were grouped with the indica cluster.<br />
Similar RFLP studies by other authors confirmed their effectiveness in differentiating
1<br />
Origin <strong>and</strong> Characteristics of U.S. <strong>Rice</strong> Cultivars 89<br />
the indica <strong>and</strong> japónica subspecies (Nakano et al., 1992; Zhang et al., 1992; Ishii<br />
et al., 1993, 1995). Macldll (1995) used RAPD markers to study a selection o f 141<br />
rice accessions that included mostly japónica cultivars. He found tliat temperate <strong>and</strong><br />
tropical japónica cultivars formed separate subclusters within the japónica cluster.<br />
However, some medium-grain temperate types were clustered with the long-grain<br />
tropical types, <strong>and</strong> the two groups appeared to form a continuum. W ith the addition<br />
o f more markers, the temperate <strong>and</strong> tropical types were differentiated more clearly. All<br />
U.S. short- <strong>and</strong> medium-grain cultivars were classified as temperate japónicas, while<br />
long-grain cultivars were classified as tropical japónicas. The lone exception was the<br />
imported cultivar Jasmine 85, an indica breeding line developed at the International<br />
<strong>Rice</strong> Research Institute (IR R I) in the Philippines.<br />
These divisions ai'e more than just academic, as the indica <strong>and</strong> japónica subspecies<br />
are fundamentally different in many ways. Their Fj hybrids are partially to<br />
completely sterile, with the exception o f some crosses between tropical japónicas<br />
<strong>and</strong> indicas (see below), <strong>and</strong> breeders tend to avoid these crosses because they rarely<br />
produce good progeny. Because o f this, the two gene pools remain relatively distinct in<br />
breeding programs. Where intersubspecific crosses are made, the Fi plants are often<br />
backcrossed to one or the other subspecies, resulting in progeny that resemble the<br />
recurrent parent. True intermediate types are rare. Many tropical japónicas produce<br />
fertile progeny when crossed with indica cultivars. These cultivars possess the “wide<br />
compatibility” allele at the Ss sterility, locus (Ikehashi <strong>and</strong> Araki, 1986). This allele<br />
probably is com m on in U.S. long grains (Zheng et al., 1994). Although the Fi plants<br />
of these crosses are fertile, segregating progeny in the F 2 <strong>and</strong> subsec[uent generations<br />
still may show sterility, <strong>and</strong> these crosses usually are considered poor combiners.<br />
DERIVATION OF U.S. RICE CULTIVARS<br />
Adair et al. (1973), <strong>and</strong> Bollich <strong>and</strong> Scott (1975) have provided a discussion o f the<br />
introduction o f rice cultivars into the United States. The <strong>origin</strong>al introductions were<br />
made into South Carolina in the seventeenth century. The long-grain japónica cultivar<br />
Carolina Gold, introduced from Madagascar, was one o f the earliest cultivars<br />
grown in tlie United States. However, this area went out o f <strong>production</strong>, <strong>and</strong> current<br />
<strong>production</strong> in the southern United States is concentrated in Arkansas, Louisiana,<br />
Mississippi, <strong>and</strong> Texas, with smaller areas in M issouri <strong>and</strong> Florida. Carolina Gold<br />
survives as a parent in tlie pedigree o f the U.S. cultivar Dawn <strong>and</strong> its derivatives.<br />
U.S. breeding programs began rice improvement activities in 1909, as did public<br />
breeding programs in Arkansas, Texas, Louisiana, <strong>and</strong> California. Johnston et al.<br />
(1972) summarized the breeding work up until 1970 <strong>and</strong> listed the prom inent cultivars<br />
developed in these breeding programs (Table 1.4.1). Breeding focused on two<br />
m ajor grain types, medium (or short) <strong>and</strong> long. These represent the two basic gene<br />
pools in the United States, although crosses between them have been made. Figures<br />
1.4.1 <strong>and</strong> 1.4.2 show the pedigrees o f the basic short/medium- <strong>and</strong> long-grain cultivars<br />
developed in the United States until 1970. Dilday (1990) provided more detailed<br />
pedigrees o f the com mercial cultivars developed before 1990 in the four states m entioned<br />
above. He observed that aU U.S. cultivars developed at the time could be traced<br />
back to 22 plant introductions in the southern United States <strong>and</strong> 23 introductions in<br />
California. Pedigrees of cultivars developed after 1970 are shown in Table 1.4.2.
90 Origin <strong>and</strong> History<br />
TABLE 1.4.1. Cultivars Released in the United States by Public Breeding Programs Up to 1970<br />
Cultivar<br />
Grain Length<br />
Classification'^' Year Maturity^ State Parents<br />
Colusa S 1917 E Louisiana Chinese<br />
Fortuna L 1918 M Louisiana Pa Chiam<br />
Caloro S 1921 M California Early Wateribune<br />
Rexoro L 1928 L Louisiana Marong-Paroc<br />
Nira L 1932 L Louisiana Unnamed Philippine cultivar<br />
Zenith M 1936 E Arkansas Blue Rose<br />
Arkrose M 1942 M Arkansas Caloro/Blue Rose<br />
Texas Patna L 1942 L Texas Rexoro/Cl5094<br />
Bluebonnet L 1944 M Texas Rexoro/Portuna<br />
Cody S 1944 E Missouri Colusa/Lady Wright<br />
Magnolia M 1945 E Louisiana Imp. Blue Rose/Fortuna<br />
Calrose M 1948 M California Caloro/2*Calady<br />
TP49 L 1948 L Texas Texas Patna/Rexoro<br />
Lacrosse M 1949 E Louisiana Colusa-BR/Shoemed-Fortuna<br />
Bluebonnet 50 L 1951 M Texas Bluebonnet<br />
Century Patna 231 L 1951 M Texas Texas Patna/Rexoro-Sup. BL Rose<br />
Impr. Bluebonnet L 1951 M Texas Rexoro/Nira<br />
Sunbonnet L 1953 M Louisiana Bluebonnet<br />
Toro L 1955 M Louisiana Bbt/Rexoro/2’^Blue Rose<br />
Mo. R 500 M 1956 VE Missouri Mesh.-Zen./Gin Bozu-Ey BR<br />
Nato M 1956 E Louisiana Rexoro-Pr Leaf/Magnolia<br />
Gulfrose M 1960 E Texas Bruinmissie sel./Zenith<br />
Belle Patna L 1961 VE Texas Rexoro/Hill sel.-Bluebonnet<br />
Northrose M 1962 E Arkansas Lacrosse/Arkrose<br />
Nova M 1963 E Arkansas Lacrosse/Zenith-Nira<br />
Palmyra M 1963 E Missouri Caloro/Blue Rose<br />
Vegold L 1963 VE Arkansas Hill sel./(T. Patna/Rex-SBR)<br />
Saturn M 1964 E Louisiana Lacrosse/Magnolia<br />
Bluebelle L 1965 VE Texas CI9214/CP231-CI9122<br />
Dawn L 1966 E Texas CP231/TP49-CI9515<br />
Nova 66 M 1966 E Arkansas Nova<br />
Starbonnet L 1967 M Arkansas CP231 /Bluebonnet<br />
CS-M3 M 1968 M California Smooth No.4-Calady40/Calrose<br />
Delia L 1970 E Louisiana R- D/ (Century/Rexoro-Zenith)<br />
Vista M 1970 VE Louisiana Rexoro-Zenith/Lac. -Magnolia<br />
Source: Data from Johnston et al. (1972).<br />
"L, long; M> medium; S, short.<br />
•'VE, very early; B, early; M, medium; L, late.<br />
Long-Grain Cultivars<br />
Agronomicallly <strong>and</strong> morphologically, the long-grain types are distinct from the<br />
medium grains, <strong>and</strong> the similarity o f their grain dimensions to tropical lowl<strong>and</strong><br />
cultivars may have resulted in their being mistakenly identified as indicas. In the rice<br />
trade, it is still com m on for the long grains to be referred to as indicas. Although this is<br />
underst<strong>and</strong>able in view o f their similarity in terras o f marketing, it is unfortunate that
Origin <strong>and</strong> Characferistics of U.S, <strong>Rice</strong> Cultivars 91<br />
Unkown Marong Unkown<br />
Bertone Sinawpagh (Philippines) Faroe (Japan) T487 Hill sel. Pa Chain Guinosgar<br />
Carolina<br />
Gold<br />
Cl 5309<br />
Delitus INiraj Rexord Blue Rose<br />
|Foituna| Shoemed<br />
Zenith<br />
- _ j<br />
¡Texas Patna|<br />
Improved<br />
Bluebonnet<br />
Supreme<br />
Bluerose<br />
iCP231j<br />
Déliai<br />
|Pawñ||Belle Patna||VegoldjlBluebeiielIStarfacainet|froto][Bluelxinnet501|Sunbonnet|<br />
Figure 1.4.1. Derivation of Lf.S, long-grain cultivars developed before 1972. Cultivars in boxes are released<br />
long-grain cultivars.<br />
Smooth Lady Early Unkown Marong<br />
Bruinmissie No. 4 Wright Wataribune Chinese Nira (Japan) Pa Chain Guinosgar Faroe<br />
I Caloro I<br />
iColusaj<br />
I Blue Rose I<br />
Fortuna Shoemed Rexoro<br />
—<br />
I Caiady |<br />
ICodyj<br />
Zenith I<br />
ICSM^SI<br />
Icalrosel<br />
|Arkrose| |Lacmsse| |Magnolia<br />
1 _<br />
Gulfrose<br />
f Northrosel |Noval iSaturnf<br />
I Nova 6 6 1<br />
I Nato I I Vista I<br />
Figure 1.4.2. Derivation of U.S. short- <strong>and</strong> medium-grain cultivars developed before 1972. Cultivors in boxes are<br />
released short- or medium-grain cultivars.<br />
this botanical term is used incorrectly. The m ajor contributors to long-grain pedigrees<br />
are tropical japónica cultivars from Southeast Asia. The most prom inent o f tliese is<br />
Rexoro, derived from the Philippine cultivar Marong Faroe (Figure 1.4.1). Fortuna<br />
is also an im portant source, especially through its contribution to the popular cultivar<br />
Bluebonnet. Rexoro <strong>and</strong> Bluebonnet dominated rice <strong>production</strong> in the southern
1<br />
92<br />
Origin <strong>and</strong> History<br />
TABLE 1.4.2. Cultivars Released in the United States, 1971-2001<br />
Cultivar<br />
Grain Length<br />
Classification'' Year Maturity^ State Parents<br />
CS-S4 S 1971 M California Sm487-l/Caloro<br />
Della L 1971 L Louisiana Rexoro/Delitus/3/Century//Rexoro/<br />
Zenith<br />
Vista M 1971 M Louisiana Rexoro/ZLacrosse/Magnolia<br />
CS-S4 M 1972 L California Caloro/Smooth No, 3//Caloro/3/Caloro<br />
Labelle L 1972 VE Texas Belle Patna/Dawn<br />
Nortai S 1972 L Arkansas Northrose/PI 215936<br />
Bonnet 73 L 1973 L Arkansas Cl 9453/Bluebonnet 50//CI9187<br />
Braxos M 1974 E Texas Cl 9545/Nova<br />
Lebonnet L 1974 E Texas BluebelleZ/Belle Patna/Dawn<br />
M5 M 1975 L California CS-M3 mutation selections<br />
S6 S 1975 E California Colusa/CS-M3<br />
Calrose 76 M 1976 L California Induced mutant in Calrose<br />
LA 110 . M 1976 L Louisiana Taichung Native No.l/H4<br />
Nova 76 M 1976 E Arkansas Cl 9580/Nova 66<br />
Mars M 1977 E Arkansas Northrose/Zenith//Saturn<br />
M7 M 1978 L California Calrose 76/CS-MS<br />
M9 M 1978 L California IR8/CS-M3//10-7<br />
CaImochi-201 S 1979 E California Mutant of S6<br />
L-201 L 1979 E California Cl 9701/3/R134-1/R48-257//R50-11<br />
M-101 M 1979 VE California CS-M3/Calrose 76//D31<br />
Newrex L 1979 E ^ Texas Bluebelle/Dawn//Belle Patna/Dawn/3/<br />
Bluebonnet 50*2/fojutla<br />
M-301 M 1980 M California Calrose 76/CS-M3//M5<br />
S-201 S 1980 E . California Calrose 76/CS-M3//S6<br />
Bellemont L 1981 E Texas BluebelleZ/Belle Patna/Dawn/3/<br />
Bluebelle'^6/TN-1<br />
Calmochi-202 S 1981 E California R57-362M/D51//Calmochi-201<br />
Leah L 1981 E Louisiana Natural outcross in Cl 9902<br />
M-302 M 1981 M California Calrose 76/CM-M3//M5<br />
M-401 M 1981 L California Mutant of Terso<br />
M-2Ú1 M 1982 E California Terso/3/IR-8/CS-M3'^2//Kokuhorose<br />
Bond L 1983 VE Arkansas Vegokl/CI 9556//Dawn/3/Starbonnet/<br />
Taducan<br />
Lemont L 1983 E Texas Lebonnet/4/Bluebell//Belle Patna/<br />
Dawn/3/Bluebelle’'-6/TNM<br />
Newbonnet L 1983 E Arkansas Dawn/Bonnet 73<br />
Pecos M 1983 E Texas Cl 9545//Gulfrose/Tainan IKU 487 iku<br />
Skybonnet L 1983 VE Texas Bluebelle//BeEe Patna/Dawn<br />
Toro-2 L 1983 E Louisiana Cl 9902/5/Rexoro/Lacrosse/4/CI 654//<br />
Rexoro/Fortuna/3/dwarf<br />
L-202 L 1984 E California PI 723761/PI7232278//L-201<br />
Tebonnet L 1984 VE Arkansas Bonnet 73/CI 9841<br />
Calmochi 101 S 1985 VE California Tatsumimochi//M7/S6<br />
M-202 M 1985 E California IR-8/CS-M3^2//10-7''2/3/M-101<br />
Gulfmont L 1986 E Texas Lebonnet/4/Bluebell//Belle Patna/<br />
DiWn/3/Bluebelle’'‘6/TN -1<br />
continued
Origin <strong>and</strong> Ciiaracteristics of U.S. Rke Cultivars 93<br />
TABLE 1.4.2.<br />
Cultivar<br />
Cultivars Released in the United States, 1 9 7 1 -2 0 0 1 (Continued)<br />
Grain Length<br />
Classification'' Year Maturity'’ State Parents<br />
Rexmont L 1986 E Texas Newrex/Bellemont<br />
A-301 L 1987 M California IR-22/R48-257//5915C35-8/3/Della<br />
M-102 M 1987 VE California M-201/M-101<br />
Mercury M 1987 E Louisiana Short Mars/Nato<br />
Rico 1 M 1987 L Texas Nortai//CI 9545/Nova<br />
M-20'3 M 1988 E California Mutant of M-401<br />
S-101 S 1988 VE California 70-6526//R26/Toyohikari/3/M7/<br />
74-Y-89//SD7/73-221<br />
Jasmine 85 L 1989 L Texas IR262/Khao-Dawk-Mali 105<br />
Katy L 1989 E Arkansas Bonnet 73/CI 9722//Starbonnet/Tetep/<br />
3/Lebonnet<br />
M-103 M 1989 VE California 78-D-1S347/M-302<br />
Maybelle L 1989 VE Texas Skybonnet/L-201<br />
Alan L 1990 VE Arkansas Labelle/L-201<br />
Millie L 1990 VE Arkansas Lebonnet/L'-201<br />
S-30Í S 1990 M California SD7/73-221/M7P-1/3/M7P-5<br />
Texmont L 1990 VE Texas RU8303116/4/Lemont/PI 331581//<br />
L-201/3/Lemont<br />
L-203 L 1991 . E California J.-202/83-y-45<br />
Lacassine L 1991 E Louisiana Newboiinet/Lemont<br />
Orion M 1991 E Arkansas Brazos/Mars<br />
Rosemont L 1991 E Texas Bluebelle/ZBelle Patna/Dawn/3/<br />
BluebelleWN- 1/4/L-201<br />
Bengal M 1992 E Louisiana Mars//M-201/Mai‘s<br />
Cypress L 1992 E Louisiana L-202/Lemont<br />
Dellmont L 1992 E Texas Della-X2/LemonP'‘5<br />
Adair L 1993 E Arkansas L--201/4/iinknown off-type/3/CI<br />
9439//Bluebonnet/PI 184675<br />
Jackson L 1993 VE Texas Skybonnet/L-201<br />
Lagrue L 1993 E Arlcansas Bonnet 73/Nova 76//Bonnet 73/3/<br />
Newrex<br />
Jodon L 1994 VE Louisiana L-202/Lemont<br />
Kaybonnet L 1994 E Louisiana Katy/Newbonnet<br />
M~204 M 1994 E California M-201/M7/3/M7//ESD7-3/Kokuhorose<br />
DeJJrose L 1995 E Louisiana Lemont/Della<br />
Lafitte M 1995 E Louisiana Mercury/ZMercuiy/Koshihikari<br />
A-201 L 1996 E California L-202/PI 457920//L-202<br />
Dixiebelle L 1996 E Texas Newrex/Bellemont///CB 801<br />
Drew L 1996 E Arkansas Newbonnet/Katy<br />
jetierson L 1996 E Texas Rosemont/B82-761<br />
L-204 L 1996 E California LemontZ/Tainung-sen-yu 2414/L-201<br />
Litton L 1996 E Mississippi L-201//Tebonnet/BeUemont<br />
S-102 S 1996 VE California Calpearl/Calmochi-101//Calpearl<br />
Priscilla L 1997 E Mississippi L-201 //Tebonnet/Bellemont<br />
Cadet L 1998 VE Texas Cypress/P<strong>and</strong>a<br />
Cocodrie L 1998 VE Louisiana Cypress//L-202/Tebonnet<br />
Jacinto L 1998 E Texas Cypress/Pelde<br />
continued
94 Origin <strong>and</strong> History<br />
TABLE 1.4.2.<br />
Cuhivar<br />
Cultivara Released in the United States, 1971 “ 2001 (Continued)<br />
Grain Length<br />
Ctassificallon" Year Maturity^ State Parents<br />
Madison L 1998 E Texas Lemont/Katy<br />
Calhikari-201 S 1999 E California Koshihikari/ (Koshihikar i/ S-101)’^2<br />
Calmati“201 L 1999 E California 85H3942//L-202/PI373938/3/<br />
83-Y-45/PI457918<br />
L-205 L 1999 E California M7/79H4310//M7/R1588/3/<br />
82-Y-52/4/Rexmont/83-Y-45<br />
M-402 M 1999 L California Kokuhorose/4/M7*^2/M9//M7/3/<br />
M-401/Kokuhorose<br />
Wells L 1999 E Arkansas Newbonnet/3/Lebonnet/CI 9902//<br />
Labelle<br />
Delmati L 1999 VE Louisiana Domsiah/Lemont/Newbonnet/3/<br />
Lemont/D ella<br />
Earl M 2000 E Louisiana Mercury/Ricol/ZBengal<br />
M-104 M 2000 VE California M-103/6/Fl(M-102/4/M-201/3/M7/<br />
M9//M7/5/M-103)<br />
M-205 M 2000 E California M-201/M7//M-201/3/M-202<br />
Ahrent L 2001 E Arkansas Recurrent Sel from Vista, Nortai,<br />
Lemont, L-201,.STG77M11697,'Katy,<br />
Tebonnet, LabeUe<br />
Saber L 2001 E Texas Gulfmont/RU8703196//Teqing<br />
Francis L 2001 E Arkansas Lebonnet/9902/3/Dawn/9695/<br />
Starbonnet/4/LaGrue<br />
Bolivar L 2001 E ■ Texas Gulfmont’^2/Teqing<br />
Neches L 2001 E Texas Lebonnet-Waxy/BeUemont<br />
Sierra L 2001 E Texas Dellmont/B8462T3-710<br />
Lavaca L 2001 E Texas Dellmont/B8462T3-710<br />
"L, long; M) medium; S, short.<br />
^VE, very early; E, early; M, medium; L, late.<br />
United States during the 1940s <strong>and</strong> 1950s, respectively, <strong>and</strong> have contributed their<br />
genes to all nearly all currently grown long-grain cultivars.<br />
Since 1970, breeders in the southern United States have been releasing new long-<br />
grain cultivars developed from the initial germplasm base described in Figure 1.4.1<br />
(Table 1.4.2). In the 1970s, the cultivars Labelle (Belle Patna/Dawn) <strong>and</strong> Lebonnet<br />
(BluebelleZ/Belle Patna/Dawn) were released in Texas, <strong>and</strong> Bonnet 73 (a cross based on<br />
Blue Bonnet 50) was released in Arkansas. These featured prom inently in pedigrees of<br />
more recent cultivars. In 1979, the cultivar Newrex was released in Texas. This cultivar<br />
contained elevated levels o f amylose starch that conferred unique processing characteristics.<br />
This was inherited from the M exican japónica cultivar Jojutla. M ore recent<br />
cultivars developed from Newrex include Rexm ont (Texas, 1986), LaGrue (Arkansas,<br />
1993), <strong>and</strong> Dixiebelle (Texas, 1995). In a similar vein, the arom atic property o f Della<br />
was incorporated into higher-yielding cultivars such as Dellemont (Della/S’^Lemont)<br />
from Texas <strong>and</strong> Deliróse (Lemont/Della) from Louisiana.<br />
Developing long-grain cultivars for California was a m ajor undertaking considering<br />
that no long-grain rice with temperate adaptation was initially available.
Origin <strong>and</strong> Characteristics of U.S. <strong>Rice</strong> Cultivars 95<br />
A m ajor breakthrough was attained with tlie release o f L-201 in 1979. This cultivar<br />
ultimately traces to southern germplasm (Tseng et al., 1979; Dilday, 1990). This tall<br />
cultivar had some drawbacks, including poor milling recovery <strong>and</strong> susceptibility to<br />
low temperature. Subsequent semidwarf releases, from 1-202 in 1984 <strong>and</strong> to L-205<br />
in 1999, have resulted in better adaptation to low temperature, <strong>and</strong> improved milling<br />
<strong>and</strong> yield. The California long-grain types form a rather unique classs representing a<br />
long-grain “tropical” japónica cultivar adapted to more temperate conditions.<br />
Medium- <strong>and</strong> Short-Gmin Cultivars<br />
The medium-grain U.S. cultivars are derived from temperate japónica introductions<br />
from Japan or Europe (Figure 1.4.2). The medium-grain cultivars Blue Rose <strong>and</strong> Early<br />
Prolific were selected by a Louisiana farmer, S. L. Wright. They dominated m edium -<br />
grain <strong>production</strong> in the early part o f the century (BoHich <strong>and</strong> Scott, 1975). Nato <strong>and</strong><br />
Zenith were other popular medium-grain cultivars. Zenith has achieved prominence<br />
as the source of one o f the most widely used blast-resistant genes, Pi-z (Kiyosawa, 1967).<br />
Im portant medium-grain cultivars developed in the 1970s included Brazos<br />
(CI9545/Nova) in Texas <strong>and</strong> Nova 76 (Northrose/Zenith//Nova 66) <strong>and</strong> Mars (North-<br />
rose/Zenith//Saturn) in Arkansas (Table 1.4.2). CI9545 was a selection from the cross<br />
between T487 (a Japanese “ponlai” japónica cultivar) <strong>and</strong> Rexark (Rexoro/Bluerose<br />
background). Brazos <strong>and</strong> Mars were noted for their high yields, <strong>and</strong> the latter features<br />
prominently in the pedigrees o f subsequently developed medium-grain cultivars<br />
in the South. Pecos (CI9545//Gulfrose/T487) was released, in 1983 in Texas,<br />
Mercury (Short Mars/Nato) was released in 1987 in Louisiana, <strong>and</strong> Rico 1 (Nor-<br />
tai//Cl9545/Nova) was released in 1987 in Texas. (Nortai was a short-grain cultivar<br />
developed from the cross Northrose/T487.) These cultivars were shorter in height<br />
than previous releases. M edium-grain releases in the southern states in recent decades<br />
have built on the same germplasm base o f the cultivars released previously.<br />
The earliest releases in California were the short-grain cultivars Colusa <strong>and</strong> Caloro.<br />
Colusa was selected from the cultivar Chinese <strong>and</strong> released in 1917. Caloro<br />
was selected firom the Japanese cultivar Early Wataribune <strong>and</strong> released in 1921. The<br />
medium-grain cultivar Calrose was developed from the cross o f Caloro backcrossed<br />
to Calady <strong>and</strong> released in 1948. This became the st<strong>and</strong>ard for high-quality California<br />
medium-grain rice, <strong>and</strong> subsequent medium grains have been marketed under the<br />
Calrose label. The first semidwart rice released in the United States was Calrose 76;<br />
the semidwarfism was induced through gamma irradiation o f seed (Rutger <strong>and</strong> Peterson,<br />
1976). Newer cultivars have focused on higher yields <strong>and</strong> earlier maturity. The<br />
cultivar M -202 has been the dom inant cultivar in California in the 1990s. “Prem ium-<br />
quality” medium-grain cultivars include M -401, selected from the cultivai' Terso, <strong>and</strong><br />
the proprietary cultivar Kokuho Rose. All o f these medium-grain cultivars have the<br />
temperate japónica background o f northeastern Asian cultivars.<br />
Although seed samples are not available for some o f the <strong>origin</strong>al progenitors of<br />
U.S. cultivars, it appears that nearly all the parents are japónica types. In the temperate<br />
environment o f California, this is certainly underst<strong>and</strong>able, because the cool temperatures<br />
require use of cold-tolerant germplasm. In the southern United States, however,<br />
indica cultivars can be very productive. The traditional indica cultivars are photoperiod<br />
sensitive, <strong>and</strong> most will not flower under the longer daylengths o f the higher
96 Origin <strong>and</strong> History<br />
latitudes. Therefore, it is not surprising that the relatively photoperiod-insensitive<br />
tropical japónica cultivars found a niche in tlie southern United States. Recently developed<br />
indica rices, especially those from subtropical locations such as China, are very<br />
productive in the southern United States. They have not found favor, hov^ever, because<br />
of their inferior grain quality (see below). The most im portant indica contributors<br />
to modern U.S, cultivars are Taichung Native 1 (T N I) <strong>and</strong> 1R8, the sources o f the<br />
major semidwarf gene. In California, the sdl gene from IR8 was introduced into the<br />
medium-grain cultivar M 9, <strong>and</strong> in the southern United States the cultivar Lemont<br />
derived this gene from T N I. In both cases, however, several backcrosses were made<br />
to japónica types to reconstitute the properties needed for U.S. cultivars.<br />
CHARACTERISTICS OF U.S. RICE CULTIVARS<br />
Agronomic Characteristics<br />
There has been a general trend o f reduced plant height <strong>and</strong> shorter growth duration<br />
in cultivars developed by U.S. breeding programs over the years. Some of the cultivars<br />
released in the southern United States (e.g., Newbonnet) possessed quantitatively<br />
inherited shorter plant height. The first cultivar with semidwarfism was Calrose 76,<br />
released in 1976 (Rutger <strong>and</strong> Peterson, 1976). Subsequently, medium-grain cultivars<br />
with the semidwarfism o f the tropical source IR8 were utilized in breeding the California<br />
cultivar M 9. In the southern United States, Lemont was released incorporating<br />
the semidwarf gene from Taichung Native 1. Although some taller cultivars continue<br />
to be released in Arlcansas, most U.S. breeding programs are currently developing only<br />
semtdwarf cultivars.<br />
As m entioned above, U.S. rice cultivars share the overall features o f the japónica<br />
subspecies. They generally are lower in tillering ability than indica types, which is<br />
not necessarily an undesirable feature for direct-seeded environments. The California<br />
breeding program has concentrated on breeding for water seeding, with selection for<br />
larger panicles, larger kernel size, stronger straw strength, <strong>and</strong> less lodging. Introductions<br />
from Japan typically lodge under this system. The U.S. medium grains tend to<br />
have intermediate levels o f threshability, compared to hard-threshing Japanese cultivars<br />
<strong>and</strong> easy-threshing tropical types (M ackill <strong>and</strong> Lei, 1997), California cultivars are<br />
adapted to the cool temperate environment, have strong seedling vigor under lower<br />
temperatures, <strong>and</strong> have relatively good tolerance o f low-temperature induced sterility<br />
during the booting stage. They are strongly thermosensitive, witli durations o f less<br />
than 70 days to flowering under tropical conditions. Thus soutliern U.S. cultivars tend<br />
to be late under California conditions, while California cultivars may often be too<br />
early when grown in the South. Long-duration cultivars such as Calrose <strong>and</strong> M -401<br />
are strongly sensitive to photoperiod compared with earlier cultivars.<br />
The U.S. long-grain cultivars represent a relatively unique germplasm pool. On<br />
a worldwide scale, the tropical japónica cultivars have been relatively neglected in<br />
intensive breeding programs. Much o f the breeding has been conducted for upl<strong>and</strong><br />
conditions, where yield potential is limited by drought, intense blast disease pressure,<br />
<strong>and</strong> low inputs. Breeders in the United States have produced tropical japónica<br />
cultivars with high yield potential <strong>and</strong> exceptional long-grain quality that surpasses
Origin <strong>and</strong> Characteristics of Ü.S. <strong>Rice</strong> Cullivars 97<br />
that found in indicas. Although indica cultivars from higher-latitude regions such<br />
as China will outyield local japónica long grains, the excellent cooking <strong>and</strong> milling<br />
characteristics o f the U.S. long grains have not been matched in these adapted indicas.<br />
Grain Quality Characteristics<br />
Grain quality, which would include physical appearance, <strong>and</strong> cooking <strong>and</strong> processing<br />
characteristics, has been one o f the defining features o f U.S. rice since its beginnings<br />
with Carolina Gold. This coarse, long-grain type cooked dry <strong>and</strong> fluffy <strong>and</strong> becam e<br />
the target quality for the U.S. long grains as germplasm was introduced <strong>and</strong> selected<br />
for the southern U.S. region. The founding parent for U.S. long-grain cultivars was<br />
Rexoro <strong>and</strong> it became a quality st<strong>and</strong>ard <strong>and</strong> parental cultivar for the hybridization<br />
programs o f the first USDA rice breeders, H. Beachell, N. Jodon, <strong>and</strong> C. Adair. Prom<br />
Rexoro came the bonnet cultivars (Bluebonnet, Bluebonnet 50, Starbonnet). The<br />
Indian patna type arose out o f Texas (Texas Patna, Belle Patna, Bluebelle <strong>and</strong> Labelle)<br />
<strong>and</strong> had a heavy emphasis on a highly translucent grain. These pools were combined<br />
to produce Lebonnet, a very successful large-kernel long grain that was in <strong>production</strong><br />
in the 1980s <strong>and</strong> was popular as parboiled rice. Lebonnet became the parent for the<br />
successful semidwarf long-grain Lem ont that has now, in turn, been followed by its<br />
offspring. Cypress.<br />
Before the 1950s, rice quality was judged solely on the basis o f its milling yields,<br />
factors affecting milling yields, <strong>and</strong> cleanliness <strong>and</strong> purity (Webb, 1975). Long-grain<br />
breeding encountered a m ajor quality problem with the release o f Century Patna 231.<br />
This cultivar had superior agronom ic characteristics, but after it was released it was<br />
discovered that its cooking <strong>and</strong> processing characteristics were atypical o f the U.S.<br />
long grains <strong>and</strong> completely unacceptable. This led to an expansion in rice quality<br />
research <strong>and</strong> establishment o f the USDA-ARS <strong>Rice</strong> Quality Research Laboratory at<br />
Beaum ont, Texas, in 1955. This laboratory has developed grain quality tests <strong>and</strong> conducts<br />
physiocheraical quality evaluations on breeding lines from all the U.S. public<br />
rice breeding programs <strong>and</strong> has been involved in evaluation <strong>and</strong> release o f all<br />
subsequent U.S. public rice cultivars. This has ensured that new cultivars have tire<br />
desired quality characteristics needed for their target market class, primarily the long-,<br />
m edium -, <strong>and</strong> short-grain market classes.<br />
Efforts to further improve long-grain quality by developing a drier, fluffier table<br />
rice with improved canning stability <strong>and</strong> low washout losses in processing led to the<br />
development o f Newrex (Webb et al., 1985). The Newrex type has a much lower<br />
amylographic breakdown viscosity, 2 to 4% higher apparent amylose content, <strong>and</strong><br />
lower solids loss in processing thus improving kernel integrity during processing <strong>and</strong><br />
a firmer cooked kernel texture.<br />
In the development o f adapted long grains for the cool arid California climate,<br />
achieving the desired cooking <strong>and</strong> milling yield proved to be a difficult breeding<br />
challenge. Cultivar L-202 was well adapted <strong>and</strong> productive in California <strong>and</strong> became<br />
the m ajor European cultivar. However, L-202 cooks softer than U.S. southern long<br />
grains, even though it has 2% higher apparent amylose content. <strong>Rice</strong> quality research<br />
revealed that it has a weaker amylographic profile tliat differs fi-om that o f other U.S.<br />
loi^g grains. This inform ation was used to develop an improved-cooking California<br />
[ t UM UniversMflsbib'iothsk 1<br />
1 TeifoibliolfekW eihaastepnaa |
98 Origin <strong>and</strong> History<br />
long grain, L-204 (Tseng et al., 1997), which also had an improved milling yield. The<br />
next step was to develop a firmer-cooking Newrex type for California, <strong>and</strong> this was<br />
achieved with the release o f L-205 in 1999.<br />
Traditional U.S. medium <strong>and</strong> short grains cook m oist <strong>and</strong> clingy, with a low amy-<br />
lose content <strong>and</strong> low gelatinization temperature. The ancestral introductions in this<br />
germplasm were the short-grains Caloro <strong>and</strong> Colusa. These were the primary cultivars<br />
grown in California until the 1960s. By crossing these short grains with a long grain,<br />
a bolder grain type was achieved with the starch characteristics o f the short grains<br />
that is now the U.S. medium-grain market class. Nato, Saturn, <strong>and</strong> Mars became the<br />
predominant medium grains in Louisiana <strong>and</strong> Arkansas. Calrose was released in 1948<br />
in California, remaining in <strong>production</strong> until the late 1970s <strong>and</strong> was the basis for the<br />
Australian rice industry. This cultivar <strong>and</strong> its progeny shifted the state’s <strong>production</strong><br />
away from short grain to its current level o f approximately 90% medium-grain <strong>production</strong>.<br />
Because of its long-term success <strong>and</strong> marketing, Calrose became a trade term<br />
for California medium grain <strong>and</strong> is still used to identify California medium-grain<br />
quality.<br />
Short-grain <strong>production</strong> in California declined as Calrose exp<strong>and</strong>ed <strong>and</strong> new im <br />
proved semidwarfs such as M -202 were released. It continued to decline with loss of<br />
traditional short-grain markets such as Puerto Rico. Recently, <strong>production</strong> of Japanese<br />
short grains (Aldtakomachi <strong>and</strong> Koshihikari) has appeared in California <strong>and</strong> Arkansas<br />
in response to export market opportunities in Japan. Short-grain <strong>production</strong> has<br />
occupied only a very limited area in the southern United States.<br />
FUTURE TRENDS<br />
Conventional plant breeding has produced germplasm pools o f highly adapted<br />
medium- <strong>and</strong> long-grain cultivars <strong>and</strong> breeding lines with excellent grain quality.<br />
Naturally, crossing with exotic cultivars that lack these unique adaptation <strong>and</strong> quality<br />
requirements usually results in inferior breeding material. Therefore, U.S. rice breeders<br />
have concentrated on making improvements within the current gene pool. There is<br />
no evidence that progress in breeding has been slowed due to lack o f sufficient genetic<br />
diversity. Breeders continue to make incremental improvements in yield while adding<br />
important characteristics such as disease resistance <strong>and</strong> unique quality factors. On<br />
the other h<strong>and</strong>, it is thought that long-term progress will depend on broadening the<br />
germplasm base, <strong>and</strong> most breeders maintain crossing programs for this purpose.<br />
Making crosses between the U.S. japónica types <strong>and</strong> indica cultivars has not<br />
produced very promismg results. The hybrids must be backcrossed to the U.S. types<br />
several times, <strong>and</strong> the net effect is transfer o f only one or a few genes or chromosomal<br />
segments. Recently developed indica long-grain cultivars from the tropics appear to<br />
be approaching the grain quality level o f the U.S. cultivars, <strong>and</strong> some o f tlie indica<br />
introductions greatly outyield U.S. long grains in the southern states. Therefore, a<br />
breeding program to develop adapted <strong>and</strong> high-quality Índica types has been proposed<br />
(J. N. Rutger, personal com m unication). Another activity that may affect the<br />
future composition o f the U.S. gene pool is hybrid rice breeding. The development of<br />
indica-japonica hybrid rice is an active area o f research, <strong>and</strong> these hybrids can produce<br />
extremely high yields. It appears likely that efforts to exploit indica germplasm will<br />
increase in the future. It is unclear, however, if this will necessarily produce a new gene
Origin <strong>and</strong> Characteristics of U.S. Rke Cultivars 99<br />
pool with many intermediate types, or rather, two main gene pools, the japónica <strong>and</strong><br />
indica types, each with its own unique characteristics <strong>and</strong> uses.<br />
Quality continues to receive emphasis as a high-priority breeding objective. There<br />
has been a clear expansion in quality research, thus reflecting its importance. New analytical<br />
methods <strong>and</strong> instrum ents (Rapid Visco Analyzers, Near-infrared spectrophotometers,<br />
gas chromatography, <strong>and</strong> image analyzers) have been developed to assist<br />
in quality evaluations. These tools are being used currently in rice cultivar development.<br />
Dem<strong>and</strong>s by millers, processors, <strong>and</strong> marketers for a very high level o f quality,<br />
including uniform ity or processing behaviors, is increasing. There has been a great<br />
expansion into specialty rice types including brown rice, aromatics, Basmati, Japanese<br />
premium short grains, <strong>and</strong> Mediterranean types like Arborio for use in the domestic<br />
<strong>and</strong> export markets. These quality dem<strong>and</strong>s already are impacting traditional<br />
germplasm pools as new parents are introduced <strong>and</strong> foretell o f many challenges for<br />
future U.S, cultivar development.<br />
REFERENCES<br />
Adair, C. R., C. N. Bollich, D. H. Bowman, N. E. Jodon, T. H. Johnston, B. D. Webb,<br />
<strong>and</strong> J. G. Atkins, 1973. <strong>Rice</strong> breeding <strong>and</strong> testing methods in the United States.<br />
In <strong>Rice</strong> in the United States: Varieties <strong>and</strong> Production. USDA-ARS H<strong>and</strong>book 289.<br />
U.S, Deptartm ent o f Agriculture, Washington, D C , pp, 2 2 -75.<br />
Bollich, C. N., <strong>and</strong> J. E. Scott. 1975. Past, present <strong>and</strong> future varieties o f rice. In Six<br />
Decades o f <strong>Rice</strong> Research in Texas. Tex. Agrie. Exp. Stn. Res, Monogr. 4, College<br />
Station, TX , pp. 3 7 -4 2 ,<br />
Carney, J, A. 1998. The role o f African rice <strong>and</strong> slaves in the <strong>history</strong> o f rice cultivation<br />
in the Americas. Hum. Ecol 26:525-545.<br />
Dilday, R. H. 1990. Contribution o f ancestral lines in the development o f new cultivars<br />
of rice. Crop Sei 30:905-911.<br />
Glaszmann, J. C. 1987. Isozymes <strong>and</strong> classification o f Asian rice varieties. Theor. A ppl<br />
Genet, 74:21-30.<br />
Glaszmann, J. C., <strong>and</strong> M . Arraudeau. 1986. <strong>Rice</strong> plant type variation: “Japonica”-<br />
“Javanica” relationships. <strong>Rice</strong> Genet. Newsl, 3:41-43.<br />
Ikehashi, H., <strong>and</strong> H, Araki. 1986. Genetics o f Fi sterility in rice. In <strong>Rice</strong> Genetics.<br />
International <strong>Rice</strong> Research Institute, Manila, The Philippines, pp: 119-132.<br />
Ishii, T., T. Terachi, N. M ori, <strong>and</strong> K. Tsunewald. 1993. Comparative study on the<br />
chloroplast, mitochondrial <strong>and</strong> nuclear genome differentiation in two cultivated<br />
rice species, Oryza sativa <strong>and</strong> O. glaberrima^ by RFLP analyses, Theor. Appl. Genet.<br />
86:88-96.<br />
Ishii, T., D. S. Brar, G, Second, K. Tsunewaki, <strong>and</strong> G. S, Khush. 1995. Nuclear genome<br />
differentiation in Asian cultivated rice as revealed by RELP analysis. Jpn. J. Genet.<br />
70:643-652.<br />
Johnston, T. H., N. E. Jodon, C. N, Bollich, <strong>and</strong> J. N, Rutger. 1972. The development<br />
o f early maturing <strong>and</strong> nitrogen-responsive rice varieties in the United States. In<br />
<strong>Rice</strong> Breeding. International <strong>Rice</strong> Research Institute, Manila, The Philippines, pp.<br />
61-76.<br />
Kiyosawa, S. 1967. The inheritance o f resistance o f the Zenith type varieties o f rice to<br />
the blast fungus. Jpn. J. Breed. 17:99-107,
100 Origin <strong>and</strong> History<br />
Langevin, S. A., K. Clay, <strong>and</strong> B. Grace. 1990. The incidence <strong>and</strong> effects o f hybridization<br />
between cultivated rice <strong>and</strong> its related weed red rice {Oryza sativa L.).<br />
Evoiwticin 44:1000-1008.<br />
Mackill, D. J. 1995. Classifying japónica rice cultivars with RAPD markers. Crop Set.<br />
35:889-894.<br />
Mackill, D. J., <strong>and</strong> X. M. Lei. 1997. Genetic variation for traits related to temperate<br />
adaptation o f rice cultivars. Crop Sci. 37:1340-1346.<br />
Nakano, M ., A. Yoshimura, <strong>and</strong> N. Iwata. 1992. Phylogenetic study o f cultivated rice<br />
<strong>and</strong> its wild relatives by RFLP. <strong>Rice</strong> Genet, Newsl 9.T32-134.<br />
Oka, H. I. 1958. Intervarietal variation <strong>and</strong> classification o f cultivated rice. Indian J.<br />
Genet. Plant Breed. 18:79-89.<br />
Oka, H. 1 .1988. Origin o f Cultivated <strong>Rice</strong>, Elsevier, Tokyo.<br />
Rutger, J. N., <strong>and</strong> M. L. Peterson. 1976. Improved short stature rice. C alif Agrie. 3 0 :4 -<br />
6.<br />
Second, G. 1982. Origin o f the genic diversity o f cultivated rice {Oryza spp.): study of<br />
the polymorphism scored at 40 isozyme loci. Jp n .}. Genet. 57:25-57.<br />
Tseng, S. T., H. L. Carnaha, C. W. Johnson, <strong>and</strong> D. M . Br<strong>and</strong>om. 1979. Registration<br />
o f ‘L -2 0 r rice. Crop Sci 19:745-746.<br />
Tseng, S. T , C, W. Johnson, K. S. McKenzie, J. J. Oster, J. E. Hill, <strong>and</strong> D, M. Br<strong>and</strong>on.<br />
1997. Registration o f ‘L-204’ rice. Crop Sci 37:1390,<br />
Vaughan, D. A. 1994. The Wild Relatives o f <strong>Rice</strong>, International <strong>Rice</strong> Research Institute,<br />
Manila, The Philippines.<br />
Wang, Z. Y., <strong>and</strong> S. D. Tanksley. 1989. Restriction fragment length polymorphism in<br />
Oryza sativa L. Genome 32:1113-1118.<br />
Webb, B, D. 1975. Cooking, processing <strong>and</strong> milling qualities o f rice. In Six Decades<br />
o f <strong>Rice</strong> Research in Texas. Texas Agricultural Experiment Station, College Station,<br />
TX , pp. 97-106.<br />
Webb, B. D., C. N. Bollich, H. L. Carnahan, K, A. Kuenzel, <strong>and</strong> K. S. McKenzie, 1985.<br />
Utilization characteristics <strong>and</strong> qualities o f United States rices. In <strong>Rice</strong> Grain Quality<br />
an d Marketing. International <strong>Rice</strong> Research Institute, Manila, The Philippines,<br />
pp, 26-35.<br />
Zhang, Q. R, M. A. S. M aroof, T. Y. Lu, <strong>and</strong> B. Z. Shen. 1992. Genetic diversity <strong>and</strong><br />
differentiation o f indica <strong>and</strong> japónica rice detected by RFLP analysis. Theor. Appl.<br />
Genet. 83:495-499.<br />
Zheng, K., H. Qian, B, Shen, J. Zhuang, H. Lin, <strong>and</strong> J. Lu. 1994. RFLP based phylogenetic<br />
analysis o f wide com patibility varieties in Oryza sativa L. Theor. Appl<br />
Genet. 88:65-69.
SECTION<br />
II<br />
The Ríce Plant
Chüßter<br />
2.1<br />
<strong>Rice</strong> Morphology <strong>and</strong> Development<br />
Karen A. K. M o ld e n h a u e r <strong>and</strong> Julia H. G ib b ons<br />
<strong>Rice</strong> Research <strong>and</strong> Extension Center<br />
University of Arkansas<br />
Stuttgart, Arkansas<br />
INTRODUCTION<br />
MORPHOLOGY OF CULTIVATED RICE {ORYZASATIVAL.)<br />
Shoot Unit Concept<br />
Leaves<br />
Culm<br />
Roots<br />
Panicle<br />
Flower<br />
Grain<br />
DEVELOPMENT OF CULTIVATED RICE<br />
Growth Phases <strong>and</strong> Yield Components<br />
Vegetative Phase<br />
Germination<br />
Seedling Development<br />
Plant Growth Rate<br />
Tillering<br />
Root Development<br />
Reproductive Phase<br />
Internode Elongation<br />
Leaf Development <strong>and</strong> Canopy Architecture<br />
Tiller Development<br />
Root Development<br />
Panicle Formation<br />
Ripening Phase<br />
Grain-Ripening Process<br />
Senescence<br />
REFERENCES<br />
<strong>Rice</strong>; Origin, History, Technology, <strong>and</strong> Production, edited by C. Wayne <strong>Smith</strong><br />
ISBN 0-471-34516-4 © <strong>2003</strong> John Wiley & Sons, Inc.<br />
103
104 The <strong>Rice</strong> Plant<br />
INTRODUCTION<br />
The study of rice morphology <strong>and</strong> development is interdisciplinary. It has its <strong>origin</strong>s<br />
in plant anatomy <strong>and</strong> has application in rice research <strong>and</strong> crop <strong>production</strong>. M orphological<br />
characters are used as discrete markers to identify plant growth stagesj provide<br />
indicators for crop management, <strong>and</strong> provide selection criteria in crop improvement<br />
programs. The purpose of this chapter is to review rice morphology <strong>and</strong> development,<br />
illustrate aspects o f morphological diversity, <strong>and</strong> highlight applications in whole plant<br />
research, plant breeding, <strong>and</strong> crop <strong>production</strong>.<br />
Morphological characters are used to m onitor plant development. M onitoring is<br />
done by visual identification of critical growth stages Ci.e., emergence, tillering, the<br />
first visible signs of panicle form ation, booting, heading, <strong>and</strong> m aturation) (M olden-<br />
hauer et al., 1994). It can also involve counting the number o f emerged leaves on the<br />
main cuhn <strong>and</strong> relating a given leaf number to the total number loiown to develop for<br />
that cultivar (M iller et al., 1993; Nemoto et a l, 1995; Counce et al., 2000), Both systems<br />
have found application by farmers <strong>and</strong> researchers. Each has been incorporated<br />
into crop management models such as the Arkansas DD50 or California CARICE<br />
programs. These programs predict cultivar growth stages within the limits o f yearly<br />
weather conditions <strong>and</strong> facilitate improved timing o f cultural practices (Keisling et al.<br />
1984; Miller et al., 1993; Norman et al., 1998).<br />
<strong>Rice</strong> breeders typically select for morphological characters in crop improvement<br />
programs. These characters may include reduced plant height; sturdy culms; moderate<br />
tillering; short, erect leaves; large, com pact panicles; <strong>and</strong> earHness o f maturation.<br />
The im portance o f these characters with regard to nitrogen responsiveness in rice<br />
was established in studies on rice physiology (Tanaka, 1965b; Stansel, 1975b) <strong>and</strong><br />
genetics (Chang, 1964; Jennings, 1964; BeacheU <strong>and</strong> Jennings, 1965). Their use in the<br />
1960s as breeding objectives led to the first high-yielding varieties (HYVs) o f rice for<br />
tropical areas (the green revolution). These efforts established the concept o f an HYV<br />
as a variety that conserves a productive plant type under conditions o f high planting<br />
density <strong>and</strong> nitrogen fertility (i.e,, m odern, intensive cultivation). These concepts <strong>and</strong><br />
objectives have influenced all modern breeding programs; development <strong>and</strong> adoption<br />
o f improved cultivars have doubled world rice yields during the period 1966-1990<br />
(Kliush, 1997).<br />
MORPHOLOGY OF CULTIVATED RICE (ORYZA SATIVA L.)<br />
Shoot Unit Concept<br />
In rice literature, the shoot unit concept has been used to describe repetitive <strong>and</strong><br />
synchronous aspects o f vegetative growth (Kaufman, 1959; Hoshikawa, 1989; Nemoto<br />
et al., 1995), The shoot unit is a basic, repeating unit defined as an internode that<br />
produces a leaf at its upper end, a tiller bud on its lower end, <strong>and</strong> a root b<strong>and</strong> on both<br />
its upper <strong>and</strong> lower ends (Figure 2.1.1), The initiation <strong>and</strong> emergence o f tillers <strong>and</strong><br />
roots (from the lower portion o f the unit) are delayed relative to that o f the leaf (from<br />
the upper portion o f the unit). This delay shifts emergence o f plant parts to successive<br />
nodes, where each node is in turn defined by two internodes (Figure 2.1,1).
<strong>Rice</strong> Morphology <strong>and</strong> Development 105<br />
- 3<br />
O O O O o<br />
1. node<br />
2. interaode<br />
3. leaf sheath<br />
4. root primordia<br />
5. tiller bud<br />
O O O o o<br />
Figure 2.1.1. <strong>Rice</strong> shoot unit showing two internodes, one<br />
node, emerged leaves, tiller buds, <strong>and</strong> root primordia. (Based on<br />
drawings by Yoshido, 1981, <strong>and</strong> Hoshikawa, 1989.)<br />
The shoot unit concept is based on that o f the phytomer, which has been used to<br />
describe the botanical structure o f grasses since 1879 (Gray, quoted in Nemoto et al.,<br />
1995). In rice, the concept was considered useful although somewhat artificial, since<br />
it may not always be possible to define the leaf <strong>and</strong> internode as a morphologically<br />
distinct unit (Kaufinan, 1959). Also, the rice node includes not only tlie nodal plate<br />
but also the base o f the internode above it (associated with the next-higher leaf).<br />
Leaves<br />
The leaf consists o f a leaf sheath <strong>and</strong> a leaf blade (lamina) (Figure 2,1.2). At their<br />
junction are a pair o f auricles <strong>and</strong> a ligule. The basal portion o f the leaf sheath is<br />
attached to a nodal plate. The leaf sheath is an elongated leaf rolled into a cylinder that<br />
encloses developing new leaves (Figure 2.1.2). It supports the plant during vegetative<br />
LeafPaits<br />
1. sheath<br />
2. blade<br />
3. ligule<br />
4. auricle<br />
5. collar<br />
Culm under slieafh<br />
6. node<br />
7. internode<br />
Figure 2.1.2. Leaf <strong>and</strong> stem showing leaf parts <strong>and</strong> an<br />
external view of the culm.
106 The <strong>Rice</strong> Plant<br />
growth <strong>and</strong> acts as a storage site for starch <strong>and</strong> sugars before heading. During reproductive<br />
growth, the sheath helps to support the stem by contributing 30 to 60%<br />
toward shoot breaking strength (Chang, 1964). It is photosynthetically active <strong>and</strong><br />
encloses <strong>and</strong> protects the developing panicle.<br />
The leaf blade is long <strong>and</strong> lanceolate <strong>and</strong> has a midrib with large <strong>and</strong> small parallel<br />
veins on each side (Figure 2.1.2). The leaf blade is the m ajor organ for photosynthesis<br />
<strong>and</strong> transpiration. The leaf blade surface can be smooth (glabrous), intermediate,<br />
or pubescent (IB P G R -IR R I, 1980). American cultivars have been selected for the<br />
glabrous character since these leaves are less abrasive <strong>and</strong> ease work in rice fields.<br />
There is genetic variation for leaf length <strong>and</strong> width between cultivars (Jennings<br />
et a l, 1979) <strong>and</strong> with position on the main culm for a given cultivar (Hoshikawa,<br />
1989). The length o f the entire leaf (sheath + blade) increases with successively higher<br />
positions on the main culm. The length o f the blade relative to that o f the sheath also<br />
increases at higher stem positions. M axim um leaflength is reached in the uppermost<br />
three to five leaves (Tanaka, 1965a; Hoshikawa, 1989).<br />
The flag leaf is the last leaf to emerge on the culm. In m ost m odern cultivars,<br />
the flag leaf blade i§ often shorter <strong>and</strong> broader tlian the lower leaves. As the panicle<br />
emerges from the sheath, the flag leaf blade is nearly parallel to the panicle axis. It can<br />
remain erect, or descend after panicle emergence. M ost m odern cultivars have been<br />
selected for erect flag leaves.<br />
Leaf angle is measured during reproductive growth as the angle of openness<br />
between the blade tip <strong>and</strong> the culm. This character can be measured for the flag leaf<br />
<strong>and</strong>/or the leaf immediately below it (the penultimate leafs) (Figure 2.1.3). The angle<br />
o f the flag leaf is often independent o f that for lower leaves (Jennings et ah, 1979).<br />
Leaf angle is im portant because it affects light interception <strong>and</strong> shading o f lower<br />
leaves (mutual shading), all o f which influences the balance o f photosynthesis <strong>and</strong><br />
respiration within the canopy (Tanalca, 1965b; Stansel 1975b). Erect leaves favor in <br />
creased light interception for photosynthesis, which optimizes yield.<br />
The ligule is a thin, white triangular membrane at the base of the leaf blade,<br />
located between the leaf blade <strong>and</strong> the sheath (Figure 2.1.1).. The ligule shape during<br />
the vegetative stage can be acute to acuminate, two-cleft, or truncate (Figure 2.1.4). It<br />
maybe white, purple lined, or purple. A colored ligule m aybe associated with color in<br />
the leaf sheath. Some cultivars lack the ligule <strong>and</strong> auricle (Hguleless rice). The function<br />
of the ligule is unclear; it is thought to regulate moisture or airflow between the culm<br />
<strong>and</strong> leaf sheath, or to prevent entry o f rainwater (Hoshikawa, 1989).<br />
Figure 2.1.3. Leaf angles: (4) erect; (fi) 45°; (C) horizontal; (0)<br />
descending. (Adapted from IBPGR-IRRI 1980.)
<strong>Rice</strong> Morphology <strong>and</strong> Development 107<br />
B<br />
D<br />
Figure 2.1.4. Ligule shapes: (yi) acute; {B) acuminate; (f) two-cleft; (fl) truncate. (Adopted from<br />
!BPGR-IRRtl980.)<br />
Auricles are located at the boundary between the leaf sheath <strong>and</strong> collar (Figure<br />
2.1.1). They may be pale green or purple. They are sickle shaped <strong>and</strong> hairy. Some<br />
rice cultivars have no auricles, but generally tlie presence o f auricles distinguishes rice<br />
from barnyardgrass {Bchinochloa spp.). The collar is a b<strong>and</strong> that forms around the<br />
junction between the blade <strong>and</strong> sheatli (Figure 2,1.1). It can be pale green, green, or<br />
purple at the late vegetative stage.<br />
Culm<br />
The culm is the plant stem (Figure 2.1.5). The culm remains enclosed in the leaf sheath<br />
<strong>and</strong> does not emerge until a small portion is exserted witli the panicle after heading.<br />
1. panicle<br />
2. peduncle<br />
3. elongated internode<br />
4. node<br />
5. Unelongated (root) internode<br />
Figure 2.1.5, Moture culm showing pannicle, nodes, elongated<br />
upper internodes <strong>and</strong> unelongated ones at the base (also referred<br />
to as root nodes).
108 The <strong>Rice</strong> Plant<br />
The culm is composed o f a series o f nodes <strong>and</strong> internodes. During vegetative growth,<br />
internode elongation is generally less than 1 m m <strong>and</strong> the culm remains close to tlie<br />
ground. During reproductive growth, the three to five uppermost internodes elongate<br />
to exsert the panicle above the leaf sheaths. The fully mature culm therefore has an<br />
unelongated portion <strong>and</strong> an elongated one.<br />
The main culm is the first plant stem, developing during early vegetative growth<br />
<strong>and</strong> prior to tillering (Figures 2.1.6 <strong>and</strong> 2.1.7). It has a genetically predetermined num <br />
ber of leaves that develop during the growing season. M ost modern, early-maturing<br />
'coco 0 a C<br />
7 '^<br />
" l i<br />
Á<br />
4<br />
1. Seminal root<br />
2. Cotyledonary (coleoptilar) node<br />
3. Internode<br />
4. Leaf sheath<br />
5. Tiller bud<br />
6. Tiller<br />
7. Root primordia (thin roots)<br />
8. Root primordia (thick: roots)<br />
9. 4th node<br />
Figure 2.1.6, Lower culm; first five nodes os a seríes of shoot units. Units<br />
show emerged leaves, tiller buds <strong>and</strong> a developing tiller, primordia for the<br />
developing root system which includes the seminal root, five coleoptilar roots,<br />
increasing numbers of roots from successive nodes, <strong>and</strong> differentiation of thin<br />
versus thick roots beginning at the fourth node. (Adopted from drowings ond<br />
doto by Hoshikawa, 1989.)<br />
- 1<br />
1. main culm<br />
2. primary tiller<br />
3, secondary tiller<br />
4, roots<br />
Figure 2.1.7, External view of the base of the rice plant;<br />
main culm, tillers, <strong>and</strong> roots. (Adapoted from Hoshikawa,<br />
1989.}
<strong>Rice</strong> Morphology <strong>and</strong> Development 109<br />
cultivars develop 12 to 18 leaves on their main stem; late-maturing cultivars can have<br />
up to 23 leaves (Hoshikawa, 1989; Vergara, 1991).<br />
The cotyledonary node, at the culm base, is morphologically unique (Figure<br />
2.1.6) (Hoshikawa, 1989). It has no tiller bud at its lower end, <strong>and</strong> tire lower root<br />
b<strong>and</strong> gives rise to a single seminal root. The ear-neck node, at the top o f the culm,<br />
is also morphologically unique. It lacks both leaf <strong>and</strong> tiUer buds. Usually, its upper<br />
root b<strong>and</strong> is not differentiated. Because the cotyledonary <strong>and</strong> ear-neck nodes do not<br />
produce shoots, the total number o f nodes on the main culm o f the rice plant is equal<br />
to the number o f leaves plus two. If a cultivar produces 13 leaves on the main cuhn, it<br />
has 15 nodes.<br />
Tillers are culms that develop from the main culm <strong>and</strong> are analogous to branches<br />
(Figure 2.1.7). Tiller primordia <strong>origin</strong>ate in each shoot unit <strong>and</strong> can develop from<br />
each leaf axil during vegetative growth (Figure 2.1.6). Individual tillers are composed<br />
o f shoot units, each capable o f developing roots, leaves, tillers, <strong>and</strong> panicles. Tillers becom<br />
e morphologically indistinguishable from a main culm with time (Figure 2.1,7).<br />
The main culm has to be labeled during early growth in order to distinguish it later.<br />
The first leaf formed on a tiller is the prophyU. It is similar to the coleoptile in that<br />
it is white, pointed, <strong>and</strong> not a true leaf. It is enclosed within the leaf sheath on the main<br />
culm <strong>and</strong> not readily visible. Upon close inspection, it can be determined that leaves<br />
developing outside the tiller prophyU belong to the main culm; those developing<br />
inside the prophyU belong to the tUler (Hanada, 1993).<br />
TiUer emergence is first visible upon emergence o f the first tiller leaf, which is a<br />
true leaf with a sheath <strong>and</strong> blade (Figure 2 .1 .13P). Tillers developing from the main<br />
culm are called primary tillers (Figure 2.1.7); diose developing from prim ary tiUers<br />
are called secondary tiller$\ subsequently, tertiary or quaternary tillers may develop.<br />
Individual tiUers can be removed <strong>and</strong> used as cuttings for vegetative propagation.<br />
Culm height can be measured to either the base or tip o f the panicle. It is a measurement<br />
o f overall plant height. Because panicle length varies relatively little among<br />
cultivars or lines, it is often most practical to measure height from the ground to the<br />
panicle tip. Culm angle is measured after flowering <strong>and</strong> is a measurement o f plant<br />
type or shape (IB P G R -IR R I, 1980). It is defined as erect, intermediate, spreading, or<br />
procum bent (Figure 2.1.8). M ost modern cultivars have been selected for erectness,<br />
since spreading shapes are m ore prone to lodging.<br />
Roots<br />
The rice plant develops three distinct root types: the seminal root, mesocotylar roots,<br />
<strong>and</strong> the nodal, crown, or adventitious roots. These roots develop from different plant<br />
parts or tissues: from the embryo, the mesocotyl, <strong>and</strong> the shoot nodes, respectively.<br />
D<br />
E<br />
Figure 2.1.8. Culm Angles; (/I) erect; (S) intermediate; (C) open; (0) spreading; (f) procumbent. (Adapated<br />
from IBPGR-I RRIJ980,)
110 The <strong>Rice</strong> Plant<br />
The radicle or seminal root emerges from the cotyledonary node within the<br />
embryo. It is a single root that grows 3 to 5 cm within the first 3 days after germination,<br />
<strong>and</strong> typically extends to 12 cm (Figures 2.1.6 <strong>and</strong> 2.1.13). It contributes to plant<br />
nutrient uptake from emergence through the seven-leaf stage.<br />
Mesocotylar roots usually do not form , but can form under conditions o f deep<br />
sowing or chemical seed treatment (Hoshikawa, 1989) (Figure 2.1.15.S). These roots<br />
are thin, mibranched, <strong>and</strong> develop from the lower to the upper part o f the mesocotyl.<br />
They grow horizontally (nongeotropic).<br />
Nodal or crown roots develop from each shoot unit (Figure 2.1.6). They emerge<br />
simultaneously from a given root b<strong>and</strong> as a crown around the culm. Each shoot unit<br />
has an upper <strong>and</strong> a lower root b<strong>and</strong>. R oot emergence from the upper root b<strong>and</strong><br />
has been observed to be delayed relative to that o f tlie lower root b<strong>and</strong> (Hoshikawa,<br />
1989). Thus roots emerge around successive nodes: from the lower b<strong>and</strong> o f one internode<br />
<strong>and</strong> the upper b<strong>and</strong> o f the internode below. Star'ting in the fourth internode,<br />
roots from the lower root b<strong>and</strong> are thicker than those emerging from the upper<br />
b<strong>and</strong> (Hoshikawa, 1989) (Figure 2.1.6). The number o f roots emerging from successive<br />
shoot units increases until heading (Figure 2.1.6). Root numbers have shown<br />
linear increases from five at the coleoptilar node to 22 at the ninth node (Hoshikawa,<br />
1989).<br />
Panicle<br />
The panicle is composed o f a papicle neck node (base), rachis (axis), prim ary <strong>and</strong><br />
secondary branches, pedicels, rudim entary glumes, <strong>and</strong> spikelets (Figure 2.1.9). The<br />
basic structure of the panicle is similar to that of the shoot units o f the culm. However,<br />
the leaf becomes a vestigal bract (not visible) <strong>and</strong> the tiller becomes a branch<br />
(Hoshikawa, 1989).<br />
1. panicle neck<br />
2. panicle neck node<br />
3. central rachis (axis)<br />
4. primary branch<br />
5. secondary branch<br />
6. pedicel<br />
7. spikelet<br />
F igure 2.1.9.<br />
Parts of tlie panicle.
<strong>Rice</strong> Morphology <strong>and</strong> Deveiopment<br />
n i<br />
The central rachis is usually 12 to 15 cm long at anthesis, with 8 to 10 nodes<br />
(Figure 2.1.9). Rachis internode lengths fluctuate greatly, <strong>and</strong> primary branches may<br />
emerge in close succession at the base o f the central rachis under favorable conditions.<br />
Primary branches usually become visible 8 to 10 days after heading when they<br />
separate from the rachis. They have many nodes, <strong>and</strong> from several nodes at their base,<br />
may have secondary branches. The degree o f secondary branching can vary from none<br />
to light, heavy, or clustering (IBPGR~1RRI, 1980).<br />
Pedicels form from nodes at the tip o f primary branches <strong>and</strong> from all nodes o f<br />
secondary branches. Spikelets form at the end o f the pedicels.<br />
Panicle shape can be compact, intermediate, or open (IBPG R~IRR1,1980). Com <br />
pact panicles have been selected for in modern cultivars, because spreading panicles<br />
have generally been associated with lower yields.<br />
Flower<br />
The flower, or spikelet, has a pair o f rudimentary glumes <strong>and</strong> a lem m a <strong>and</strong> palea that<br />
enclose the floral organs (Figure 2.1.10). <strong>Rice</strong> has a perfect flower composed o f six<br />
stamens (anther <strong>and</strong> filament) <strong>and</strong> one pistil (two stigmas, two styles, <strong>and</strong> one ovary).<br />
It also contains two lodicules at the base o f the pistil (not visible in the figure). The<br />
lodicules provide the mechanism for floral opening by swelling upon hydration <strong>and</strong><br />
causing separation o f the lem m a <strong>and</strong> palea (Hoshikawa, 1989).<br />
Grain<br />
The rice kernel is composed o f a hull <strong>and</strong> caryopsis. The unpolished caryopsis is<br />
referred to as brown rice (Figure 2.1.11). The hull is comprised o f sterile lemmas,<br />
rachilla, palea, <strong>and</strong> lemma. The lemma covers two-thirds o f the seed, with the edges<br />
o f the palea fitting inside so that the two close tightly around the seed. The caryopsis<br />
contains the embryo <strong>and</strong> starchy endosperm, surrounded by the seed coat (tegmen)<br />
<strong>and</strong> the pericarp (Figure 2.1.12) (Juliano <strong>and</strong> Bechtel, 1972).<br />
Pistil<br />
1. stigma<br />
2. style<br />
3. ovaiy<br />
Stamen<br />
4. anther<br />
5. filament<br />
6. palea<br />
7. lemma<br />
8. sterile lemmas<br />
9. rudimentary ghunes<br />
10. pedicel<br />
Figure 2,1.10.<br />
Parts of the flower.
112 The <strong>Rice</strong> Plant<br />
1. Pedicel<br />
2. Sterile Lemmas<br />
3. Rachilla<br />
4. Lemma<br />
5. Palea<br />
6. Embryo<br />
7. Caryopsis (Brown <strong>Rice</strong>)<br />
Figure 2.1.11. Structure of a rice grain. (From Moldenhauer et al., 1998.)<br />
12-<br />
10-<br />
14- 15<br />
16<br />
■<br />
13<br />
11<br />
1. Scutellum (Cotyledon)<br />
2. Coleoptile<br />
3. Epicotyl (Plumule)<br />
4. Apical Meristem<br />
5. Radicle<br />
6. Coleorhiza<br />
7. Pericarp<br />
8. Tegmen (Seed Coat)<br />
9. Aleurone Layer<br />
10. Subaleurone Layer<br />
11. Starchy Endosperm<br />
12. Lemma<br />
13. Palea<br />
14. Sterile Lemmas<br />
15. Rachilla<br />
16. Part of Pedicel<br />
t ",<br />
Figure 2.1.12, Cross section of a rice kernel. (From Moldenhauer etal., 1998.)<br />
The embryo is the rudimentary plant tissue that will develop into the rice plant<br />
upon germination. The largest portion is the scutellum (cotyledon), which is shaped<br />
like a shield around the coleoptile <strong>and</strong> coleorhiza (Figure 2.1.12). The coleoptile<br />
encloses the first three leaves (plumule) as well as the apical meristem. The coleorhiza<br />
encloses the radicle (seminal root). All o f these cells are very small <strong>and</strong> swell greatly<br />
when water is absorbed during germination.<br />
The endosperm is the tissue formed during die ripening period which serves as<br />
nutrition for the embryo during germination <strong>and</strong> early seedling growth. It is com <br />
prised o f starch storage tissue, filled with starch granules <strong>and</strong> a small number o f<br />
protein bodies. It is surrounded by the aleurone layer o f cells, which are small <strong>and</strong><br />
almost cubicle, <strong>and</strong> contain protein <strong>and</strong> lipid bodies but no starch. The subaleurone<br />
layer, lying immediately below the aleurone, has characteristics intermediate to the<br />
aleurone <strong>and</strong> starch storage tissue (Juliano <strong>and</strong> Bechtel, 1972).<br />
The seed coat or tegmen is a thin m embrane with broken cell walls, which is a<br />
remnant o f the inner integument o f the ovary (Figure 2.1.12).<br />
The pericarp is the mature ripened ovary wall, consisting o f an epidermis <strong>and</strong><br />
several layers o f parenchyma that surround a vascular bundle (Juliano <strong>and</strong> Bechtel,<br />
1972). This transports solutes <strong>and</strong> minerals to the developing seed during ripening.<br />
In fully ripe seed, the parenchyma die <strong>and</strong> become spongy <strong>and</strong> the vascular bundles<br />
lose their function.
Rite Morphology <strong>and</strong> Development 113<br />
During milling, the aleurone, tegmeii, pericarp, <strong>and</strong> embryo are all removed.<br />
These removed parts constitute the rice bran.<br />
DEVELOPMENT OF CULTIVATED RICE<br />
Growth Phuses <strong>and</strong> Yield Components<br />
The growth duration o f cultivated rice varies from less than 80 to 280 days, with U.S.<br />
cultivars ranging from 105 to 145 days. Cultivars can generally be divided into three<br />
maturity groups; early-maturing cultivars (80 to 130 days), intermediate-maturing<br />
cultivars (130 to 160 days), <strong>and</strong> late-maturing cultivars (160+ days) (Yoshida, 1981).<br />
The growth duration can be divided into many stages, but the m ost basic division<br />
is into three phases: the vegetative phase, reproductive phase, <strong>and</strong> ripening phase<br />
(Tanaka, 1965a). The vegetative phase begins with germination <strong>and</strong> ends at panicle<br />
initiation, when the plant begins to partition assimilates to the developing panicle.<br />
During the reproductive phase, the panicle forms within the leaf sheath, is exserted,<br />
<strong>and</strong> undergoes an thesis (flowering). The ripening or grain-filling phase begins after<br />
an thesis <strong>and</strong> ends at m aturation.<br />
The duration o f the vegetative phase (germination to panicle initiation) is generally<br />
considered the m ost variable o f all the growth phases (Tanaka, 1964; Yoshida<br />
1981; Vergara, 1991). It can range from 25 to 90 days, <strong>and</strong> largely accounts for overall<br />
cultivai* differences in growtli duration. Cultivars selected for earliness have shorter<br />
vegetative phases <strong>and</strong> therefore earlier panicle initiation <strong>and</strong>/or fewer leaves.<br />
The duration of the reproductive phase (panicle initiation through anthesis) is<br />
generally considered to be 30 days for m ost cultivars (Yoshida, 1981; Hoshikawa,<br />
1989). However, it can vary from 15 to 46 days, depending on cultivar <strong>and</strong> temperature<br />
(Blanco, 1982). Early-maturing cultivars also may have a shorter reproductive<br />
phase (i.e., faster panicle form ation). The duration o f the ripening phase (anthesis<br />
to m aturation) varies from 25 to 45 days. In the southern United States, long-grain<br />
cultivars fill in approximately 35 days compared to medium-grain cultivars, which<br />
require 45 days, <strong>and</strong> short-grain cultivars, which can require 50 days.<br />
<strong>Rice</strong> grain yield results from developmental processes that are synchronized with<br />
plant growth. The division o f yield into four yield com ponents reflects the interdependence<br />
o f yield with sequential plant development (Table 2.1.1).<br />
Yield potentials are realized when all com ponents are optimized. Yield constraints<br />
can be evaluated by identifying which o f the com ponents are limiting. Yield<br />
improvements in subsequent crop years can then be addressed through improved<br />
management <strong>and</strong>/or plant breeding.<br />
Vegetative Phase<br />
The vegetative phase begins with seed germination <strong>and</strong> proceeds with a repetitive <strong>production</strong><br />
o f shoot units until panicle initiation. Each shoot unit produces a leaf, tiller,<br />
<strong>and</strong> root primordia. Plant development has synchrony, with main stem leaf emergence<br />
being highly conserved (i.e., a consistant character for a given cultivar across environments).<br />
The rate o f main stem leaf emergence is used to describe plant development
114 The Ri(e Plañí<br />
TABLE 2.1.1.<br />
Relationship of Yield Components to Plant Growth Phase<br />
Yield Com ponent<br />
Panicles per unit area<br />
(panicles/m^)<br />
Number of spiJcelets per panicle<br />
Percentage of filled grains<br />
(% filled, or % sterile, at<br />
maturity)<br />
Weight of filled grains<br />
(1000 seed weight)<br />
Growth Phase<br />
Vegetative phase. Numbers of panicles reflect plant<br />
vigor, tillering, planting density, soil fertility, <strong>and</strong><br />
flood depth.<br />
Reproductive phase. All potential spikelets are formed<br />
during panicle differentiation.<br />
Reproductive phase. Spikelet development is sensitive to<br />
environmental factors. Either developmental or<br />
pollination failure precludes grain filling during the<br />
next phase.<br />
Ripening phase. The weight of filled grains is<br />
determined by carbohydrate metabohsm <strong>and</strong><br />
partitioning. Grain weight can be reduced by<br />
metabolic failure. *•<br />
(Nemoto et al., 1995; Coimce et al., 2000). Emergence o f tillers <strong>and</strong> roots is m ore environmentally<br />
sensitive, but there is a steady increase in numbers <strong>and</strong> sizes o f all three<br />
plant parts. Growth during this phase results in cultivar development that is m orphologically<br />
distinct with respect to leaf characteristics (num ber on the main culm,<br />
shape, size, color, <strong>and</strong> erectness) <strong>and</strong> culm characteristics (num ber <strong>and</strong> erectness).<br />
Germination<br />
Seeds germinate upon absorption o f water <strong>and</strong> initiation o f the biochem ical processes<br />
involved in embryo growth. The process begins with im bibition <strong>and</strong> ends with<br />
sufficient swelling <strong>and</strong> growtli o f plant primordia to cause opening o f the hull <strong>and</strong><br />
visible signs o f radicle <strong>and</strong>/or coleoptile protrusion (Figures 2 .1 .13A <strong>and</strong> 2.1.14A).<br />
Germination is affected by moisture, seed dormancy, aeration, <strong>and</strong> temperature.<br />
Seeds generally begin to germinate at 15% moisture <strong>and</strong> attain full germination<br />
at 25% moisture (Hoshikawa, 1989). The process has been found to be triphasic<br />
(Talcahashi, 1984):<br />
• Phase 1: imbibition<br />
• Phase 2: metabolic activation (respiration <strong>and</strong> carbohydrate metabolism)<br />
• Phase 3: growth <strong>and</strong> emergence o f root <strong>and</strong> shoot primordia from the hull<br />
Water uptake is rapid during phases 1 <strong>and</strong> 3 <strong>and</strong> controlled by seed coat permeability.<br />
Phase 2 is regulated by gases (oxygen, carbon dioxide, <strong>and</strong> ethylene), endogenous<br />
inhibitors or horm ones, <strong>and</strong> enzymatic activity. Seed coat permeability is also a<br />
factor affecting gas exchange during germination.<br />
The seed coat can inhibit germination by reduced permeability to water <strong>and</strong><br />
gases, <strong>and</strong> also for reasons related to dormancy. Several dormancy factors, or chemicals,<br />
are contained in the seed coat. Therefore, removal o f the seed coat will often<br />
brings about more rapid germination.<br />
Dormancy refers to low germinability of viable, freshly harvested kernels. It generally<br />
is overcome by heat treatment at 40 to 50°C for 5 days (Jennings <strong>and</strong> Josue,
<strong>Rice</strong> Morphology <strong>and</strong> Development 115<br />
D<br />
1. Coleoptile<br />
2. Coleorhiza<br />
3. Seminal root (radical)<br />
4. Prophyll<br />
5. ColeoptUar (nodal) roots<br />
6. First true leaf<br />
7. Second leaf<br />
8. Third leaf<br />
9. Fourth leaf<br />
10. Tiller<br />
Figure 2.1.131 Seedling development under aerobic, light conditions (shallow upl<strong>and</strong> seeding);<br />
(ji) germinated seed; (ff) developing coleorhiza <strong>and</strong> coleoptile; (C) emerging prophyll <strong>and</strong> semlnol root; (/?) VI<br />
growth stage; (f) V2 growth stage; [F) V4 growth stage.<br />
1964). Cultivars show varying levels of dorm ancy <strong>and</strong> requirements for heat treatment.<br />
U.S. cultivars have moderate levels o f dormancy, which prevents sprouting in<br />
the field (Beachell <strong>and</strong> Evatt, 1961). High dormancy in some cultivars allows their<br />
seed to remain viable in the soil for several years.<br />
Aeration determines the order o f coleorhiza <strong>and</strong> coleoptile emergence from the<br />
hull: under aerobic conditions, the coleorhiza emerges first or together with the
116 The <strong>Rice</strong> Plont<br />
1. coleoptile<br />
2. coleorhiza<br />
Figure 2 .U 4 . Seedling development under anaerobic conditions (water seeding);<br />
[A] germinoted seed; [B) developing coleoptile; (Q developing coleoptile <strong>and</strong> delayed<br />
coleorhiza.<br />
B<br />
1, coleoptile<br />
2, prophyll<br />
3, seminal root (radical)<br />
4, coleoptilar (nodal) roots<br />
5, mesocotylar roots<br />
Figure 2.1.15. Seedling development under aerobic, dork conditions (upl<strong>and</strong><br />
seeding); (4) elongation of the mesocotyl at 1-inch planting depth; (S) further elongation<br />
of the mesocotyl with deeper planting, with possible development of mesocotylar roots.<br />
coleoptile (Figure 2 .1 .13A <strong>and</strong> B). Under anaerobic conditions, the coleoptile emerges<br />
first (Figure 2.1.15). <strong>Rice</strong> shows adaptation to hypoxic <strong>and</strong> anoxic conditions by<br />
anaerobic fermentation (Juliano, 1972). The coleoptile is the only organ o f the embryo<br />
that can emerge from the seed on energy derived solely from anaerobic fermentation.<br />
Adaptability to anaerobic germination varies with cultivar.<br />
Temperature is one of the most im portant factors affecting germination. Germination<br />
percentages o f 90 to 97% occur within 48 hours if temperatures are between 27
<strong>Rice</strong> Morphology <strong>and</strong> Development 117<br />
<strong>and</strong> 37”C (Yoshida, 1981). Germination drops sharply below these temperatures (e.g.,<br />
at 10°C, germination proceeds slowly <strong>and</strong> radicle emergence may take m ore than 30<br />
days) (J, W. Gibbons, personal com m unication).<br />
Seedling Development<br />
Seedling growth continues after germination with extension o f the coleoptUe <strong>and</strong><br />
coleorhiza <strong>and</strong> emergence o f the prophyU <strong>and</strong> radicle. During this growth stage, rice<br />
seedlings exhibit great morphological plasticity in response to changes in aeration,<br />
light, <strong>and</strong> temperature. <strong>Rice</strong> is a semiaquatic plant <strong>and</strong> has many characteristics that<br />
facilitate establishment under either aerobic or anaerobic conditions.<br />
Under aerobic conditions o f dryl<strong>and</strong> seeding, coleorhiza development is favored<br />
(Figure 2.1.13A <strong>and</strong> B). The coleorhiza develops root hairs, followed by emergence<br />
o f the seminal root (radicle). W ithin the coleoptile, the prophyU develops rapidly <strong>and</strong><br />
emerges (Figure 2.1.13ft <strong>and</strong> C).<br />
Under anaerobic conditions o f water seeding, the coleoptile elongates without<br />
simultaneous development o f other tissues. Emergence o f the coleorhiza, seminal<br />
root, <strong>and</strong> prophyU are delayed (Figure 2.1.14) until the coleoptile emerges from the<br />
floodwater surface <strong>and</strong> oxygen levels to the root are increased ( Hoshikawa, 1989).<br />
Oxygenation <strong>and</strong> root development also can be promoted by draining flood waters<br />
(Helms <strong>and</strong> Slaton, 1994). Under anaerobic conditions, roots have been observed to<br />
develop few, if any, root hairs (Hoshikawa, 1989).<br />
Light conditions affect mesocotyl elongation. W ith adequate light, or under conditions<br />
o f shaUow planting, the mesocotyl does not elongate (Figure 2.1.13D ). However,<br />
in the dark, or under conditions o f deep planting, the mesocotyl elongates to<br />
promote seedling emergence from the soil (Figure 2.1.15A ). Under conditions o f very<br />
deep planting, or chemical treatment, roots may develop from the mesocotyl (Figure<br />
2.1.15ft).<br />
Environmental effects on coleoptile <strong>and</strong> mesocotyl elongation have been attributed<br />
to changes in the com position o f the gaseous environment (oxygen, carbon<br />
dioxide, ethylene) <strong>and</strong>/or hydration (Takahashi, 1984; see also Chapter 2.2). There<br />
also are pronounced cultivar differences in seedling responses (Takahashi, 1984; Re-<br />
dona <strong>and</strong> MacldU, 1996).<br />
Temperature affects the rate o f seedling growth. Effects are m ost pronounced<br />
during tlie first week o f growth, when temperatures between 22 <strong>and</strong> 31®C are required<br />
for linear growth rates (Yoshida, 1981). This reflects temperature effects on enzymatic<br />
activity associated with the breakdown o f seed carbohydrate reserves. FoUowing the<br />
first week, temperature effects on rice growth are less pronounced. Optimal tem <br />
peratures are between 22 <strong>and</strong> 31°C, with a critical maxim um at 40“C <strong>and</strong> a critical<br />
minim um at 10°C (Yoshida, 1981).<br />
Plant growth stage can be determined by marking <strong>and</strong> counting leaves as they<br />
emerge. The first leaf to emerge from the coleoptUe, tlie prophyU, is not a true leaf<br />
since it lacks a blade. It may or may not be counted as leaf 1 when describing shoot<br />
development. The first true leaf to develop is the second leaf. Counce et al. (2000)<br />
refer to this first true leaf as leaf 1.<br />
The VI stage is defined by Counce et al. (2000) as a seedling with a prophyU <strong>and</strong><br />
a fully emerged first true leaf (leaf collar present) (Figure 2.1.13D ). This seedling also<br />
has five roots from the coleoptilar node.
118 The <strong>Rice</strong> Plant<br />
The V2 stage is defined by full emergence o f the second true leaf <strong>and</strong> is synonymous<br />
with the three-leaf stage if the prophyll is counted as the first leaf (Figure<br />
2.1.135). Seedlings at tliis stage have roots emerging from th e first node. At this stage,<br />
plants becom e autotrophic, meaning that endosperm seed reserves are exhausted <strong>and</strong><br />
photosynthesis contributes 100% o f the carbohydrate used by tlie plant (Yoshida,<br />
1981; Counce et a l, 2000). Some researchers consider this stage the end o f seedling<br />
growth.<br />
If seedlings have been grown completely in the dark, they will cease to grow<br />
beyond the V2 stage. In seedlings grown with light, photosynthesis contributes to<br />
an increasing proportion of total carbohydrate with time: During the first week of<br />
growth, it contributes 8.4%; <strong>and</strong> by<br />
approximately the third week (second true leaf) it contributes 100% (Yoshida, 1981).<br />
The V4 stage is defined by full emergence of the fourth true leaf <strong>and</strong> is synonymous<br />
with the five-leaf stage if the prophyll is counted as the first leaf (Figure 2.1.135).<br />
This growth stage usually is considered the end o f the seedling stage (IBPG R -IR RI,<br />
1980; Hoshikawa, 1989; Moldenhauer et al., 1994; Nemoto et al,, 1995), Seedling<br />
height is usually measured at this growth stage (IBPG R -IR RI, 1980).<br />
Plant Growth Rate<br />
Plant growth rate is determined by the rate at which leaves are initiated in the shoot<br />
apex. This is done in a rhythmic fashion (Fahn, 1974). Before leaf initiation, the apical<br />
meristem widens, undergoes pronounced changes in shape, <strong>and</strong> then narrows again<br />
with the appearance o f the new leaf primordium. This period o f rhythmic change<br />
between emergence o f successive leaf primordia is called plastochron. The duration<br />
o f plastochron change determines the rate o f plant growth <strong>and</strong> development. In rice,<br />
the plastochron is not uniform throughout the life cycle o f the plant <strong>and</strong> is also<br />
susceptible to environmental influences (Nemoto et al., 1995).<br />
The rate at which leaves visibly develop on the main culm is called the phyllochron.<br />
The phyllochron is strongly tied to the plastochron in rice <strong>and</strong> other grasses (Nemoto<br />
et al., 1995). Because o f this synchrony, there is orderly shoot development. This<br />
synchrony also allows the leaf number to be used as a developmental index for plant<br />
growth.<br />
By knowing the total num ber o f leaves that have developed on the m ain culm,<br />
one can relate a given leaf num ber to a particular growth stage for that variety. This<br />
system accurately identifies the onset o f reproductive growth (panicle initiation) <strong>and</strong><br />
the developmental stages of the panicle prior to heading (Hoshikawa, 1989; Nemoto et<br />
a l, 1995; Counce et a l, 2000). A rice developmental timeline based on leaf num ber is<br />
described in Figure 2.2,2. This system has been used extensively in lapan to coordinate<br />
management activities with crop development.<br />
Many environmental factors influence the rate o f development: temperature,<br />
daylength, nutrition, planting density, <strong>and</strong> humidity (Nemoto et al., 1995). Effects of<br />
thermal time (degree days) on rice plant development appear to be m ore pronounced<br />
than any other factor. Therm al time units are highly conserved (e.g., thermal time exerts<br />
a dom inant influence that is constant across (otherwise) different environments]<br />
(Miller et al., 1993; Nemoto et a l, 1995). Therm al time has provided the basis for the<br />
DD50 crop management program in Arkansas since the 1970s (Keisling et al., 1984)<br />
<strong>and</strong> remains a fundamental measurement in rice growth models developed since then<br />
(Miller et a l, 1993).
<strong>Rice</strong> Morphology <strong>and</strong> Development 119<br />
Tillering<br />
First tillering usually occurs at, or before, V 4 (Figure 2.1.13.F). Tiller <strong>and</strong> root emergence<br />
are delayed relative to that o f the leaf. Leaves emerge visibly from a given shoot<br />
unit while the corresponding root <strong>and</strong> tiller primordia are just being initiated. The<br />
latter do not become visible protrusions until the leaf from the third node above<br />
begins to emerge. Thus for a given leaf that is emerging at the «th node o f the plant,<br />
there are crown roots <strong>and</strong> a tiller bud potentially emerging at the {n - 3)th node.<br />
Although primordia for roots <strong>and</strong> tillers always are initiated by the plant, they do not<br />
always develop or may show delayed development (Nemoto et al., 1995).<br />
Active tillering refers to the growth period when tillers emerge in rapid succession<br />
(<strong>and</strong> coincides with a phase o f rapid leaf development). Tillers can potentially emerge<br />
three nodes below each emerging leaf, in a continuous pattern up the culm. These<br />
primary tillers emerge from unelongated internodes <strong>and</strong> result in a branching pattern<br />
that remains close to the ground. After the onset o f reproductive growth, tillers do not<br />
develop from the upper three to five elongating internodes, but tliey may continue to<br />
develop from preexisting tillers to exp<strong>and</strong> branching further in widely spaced plants.<br />
Under ideal conditions, a plant developing 13 leaves on the main culm before<br />
panicle initiation could have a total o f 40 tillers: 9 primary, 21 secondary, <strong>and</strong> 10<br />
tertiary (Figure 2.1.16). However, in reality, not all tiller buds develop into tillers.<br />
Under field conditions, cultivars have a maximum tiller number <strong>and</strong> are also observed<br />
to have a term ination point for effective tillering. This is a point where tiller num ber<br />
equals the number o f panicles at maturity. Tillers developed after this stage do not<br />
form panicles,<br />
Cultivars vary in tiller num ber as well as in earliness <strong>and</strong> vigor o f tillering. Some<br />
cultivars tiller very early <strong>and</strong> profusely; otliers show delayed <strong>and</strong>/or sparse tillering.<br />
Tillering also is affected by plant spacing <strong>and</strong> soil fertility. W hen seeds are drilled or<br />
broadcast densely, <strong>and</strong> plant density is high, m axim um tiller number is low (one to<br />
three tillers per plant) <strong>and</strong> is reached within 30 days o f seedling emergence (Yoshida,<br />
1. main culm<br />
2. primaiy tiller<br />
3. secondaiy tiller<br />
4. tertiary tiller<br />
Figure 2.1.16. Tillering, showing all potential primary through tertiory tillers on a plant.<br />
(From Yoshida, 1981; courtesy of the International <strong>Rice</strong> Research Institute.)
120 Th0 <strong>Rice</strong> Plant<br />
1981). W hen planting densities are low, tiller numbers increase (10 to 30 per plant)<br />
<strong>and</strong> the duration o f tillering is extended. This, in turn, can stagger the development<br />
of mature panicles <strong>and</strong> may also be associated with high levels o f ineffective tillers<br />
(Stansel, 1975a; Yoshida, 1981; Moldenhauer et al., 1994; Counce et al., 1996).<br />
Tillering characteristics are im portant to yield because they affect the num ber of<br />
culms per square meter, the uniform ity o f ripening in the field, <strong>and</strong> grain yields per<br />
panicle. Profuse tillering is considered disadvantageous because it can cause excessive<br />
increases in leaf area, mutual shading, numbers o f ineffective tillers, <strong>and</strong> lower yields<br />
by increased blanking (Wells <strong>and</strong> Faw, 1978; lennings et al., 1989). At the other extreme,<br />
elimination o f tiUering at excessive planting densities does not increase yields<br />
either (Yoshida, 1981; Gravois <strong>and</strong> Helms, 1996).<br />
Moderate numbers o f vigorous early tillers are considered the rnost advantageous.<br />
These tiUer characteristics compensate for low st<strong>and</strong> densities under conditions<br />
o f poor establishment <strong>and</strong> optimize yields by producing uniformly maturing panicles<br />
(Jennings et al., 1979; Ntamatungiro et al., 1993; Counce et al., 1996).<br />
Root Development<br />
Development o f primary roots during germination <strong>and</strong> seedling growth is described<br />
in earlier sections on root morphology <strong>and</strong> seedling growth. Root lengths in field-<br />
grown rice show rapid linear increases during yegetative growth <strong>and</strong> reach maximum<br />
lengths by panicle initiation (Beyrouty et al., 1996).<br />
Root branching during vegetative growth is synchronized with leaf emergence<br />
(Hoshikawa, 1989). For a given leaf emerging at the nth node <strong>and</strong> primary roots<br />
emerging at the (n - 3)th node, there are many short secondary roots that develop<br />
from primary roots at the (n - 4)th node. At the (n - 5)th node, tertiary roots begin to<br />
develop from secondary roots. This pattern continues, resulting in fullest expression<br />
o f branching in older roots.<br />
Soil aeration has a fundamental effect on root growth <strong>and</strong> overall morphology.<br />
Under upl<strong>and</strong>, aerobic conditions, roots develop hairs <strong>and</strong> grow downward, reaching<br />
rooting depths o f 1 m or more. Under flooded, anaerobic conditions, there may be<br />
no root hair development, growth is more horizontal, <strong>and</strong> rooting depths seldom<br />
exceed 40 cm (Beyrouty 1996; Yoshida, 1981). Rooting depths are increased when<br />
soil densities do not restrict downward movement o f floodwater <strong>and</strong> when flooding<br />
is delayed by 2 weeks (Beyrouty, 1996).<br />
Reproductive Phase<br />
The reproductive phase, from panicle initiation through anthesis, is characterized by<br />
changes in vegetative growth characteristics <strong>and</strong> form ation (differentiation) o f the<br />
panicle. Internode elongation results in increased plant height, with a concom itant<br />
reduction in tillering <strong>and</strong> root growth. Leaf architecture during the reproductive<br />
phase is critical to optimizing yields <strong>and</strong> reducing lodging (Jennings, 1964; Tanaka,<br />
1965b; Stansel, 1975a,b). Panicle form ation is synchronized with development o f the<br />
uppermost four leaves on the culm. Environmental conditions <strong>and</strong> crop management<br />
directly influence the num ber o f spikelets formed <strong>and</strong> pollen fertility (second <strong>and</strong><br />
third yield com ponents).
<strong>Rice</strong> Morphology <strong>and</strong> Development 121<br />
Internode Elongation<br />
Internodes begin to elongate at, or near, panicle initiation (PI). In late-maturing cultivars,<br />
internodes may begin to elongate before panicle initiation, while in intermediate<strong>and</strong><br />
short-season cultivars, internode elongation coincides with panicle initiation.<br />
Internode elongation also signals the beginning o f the development o f the final tliree<br />
to five internodes o f the stem. Internode lengths increase from 2 cm in the first in <br />
ternode to elongate after PI to 30 cm in the final one (the peduncle o f the panicle).<br />
The final <strong>and</strong> longest internode grows about 15 to 20 cm during the 2 days before<br />
heading <strong>and</strong> continues to grow for up to 2 days after heading. This is the greatest<br />
growth increm ent in the life o f the plant (Hoshikawa, 1989).<br />
Leaf Development <strong>and</strong> Canopy Architecture<br />
Leaves developing after panicle initiation can have different shape, erectness, <strong>and</strong><br />
color relative to leaves developing during the vegetative phase (Jennings et ah, 1979).<br />
Thus plants with long, droopy leaves during the vegetative phase may have short, erect<br />
ones during reproductive growth, <strong>and</strong> vice versa. Unless there are prolonged cloudy<br />
periods, lack o f sunlight during early vegetative growth is not considered to lim it rice<br />
yields (Stansel, 1975a; Jennings et aL, 1979). Large leaves during this stage o f developm<br />
ent have been considered advantageous because they favor crop establishment<br />
<strong>and</strong> com petition with weeds. However, during reproductive growth, canopy light<br />
conditions are critical to optimizing yields. Erect leaves have been shown to optimize<br />
light interception <strong>and</strong> reduce mutual shading. Since light reduction in the canopy can<br />
increase panicle sterility as weU as internode elongation, mutual shading was linked<br />
directly to yield reductions <strong>and</strong> increased lodging. Thus the short-statured, erectleaved<br />
plant type was found to be fondamentaUy im portant to the development o f<br />
high-yielding varieties o f rice (Jennings, 1964). The synchrony between development<br />
o f the upper four leaves <strong>and</strong> the developmental stages o f the panicle is described under<br />
panicle differentiation.<br />
Tiller Development<br />
Early-maturing varieties have short vegetative stages, <strong>and</strong> panicle initiation either<br />
coincides with, or may occur before, maxim um tillering. Heading may not be uniform<br />
within the plant because late tiUers produce late panicles (Tanaka, 1965a; Stansel,<br />
1975a). Medium- <strong>and</strong> late-maturing varieties have long periods o f vegetative growth<br />
<strong>and</strong> may reach maxim um tillering well before panicle initiation. The period between<br />
maximum tillering <strong>and</strong> panicle initiation in late varieties is referred to as the vegetative<br />
lag phase (Tanaka, 1965a).<br />
The number of plants <strong>and</strong> the tiller num ber per plant determine the total number<br />
o f panicles per unit area ( first yield com ponent). There is often a trade-off between<br />
tiller number <strong>and</strong> panicle size; few tillers with large panicles versus many tillers with<br />
small panicles (Wells <strong>and</strong> Faw, 1978; Jennings et ah, 1979).<br />
Late-maturing tillers can lower head rice yield by reduction o f milling quality<br />
(Stansel, 1975a). The first three tillers mature about the same time as the main<br />
culm, but additional tillers may mature progressively later <strong>and</strong> have reduced milling<br />
quality.
122 The <strong>Rice</strong> Plant<br />
Root Development<br />
Root growth typically remains constant from panicle initiation to heading. This has<br />
been observed with respect to root numbers emerging from a given node (Hoshrkawa,<br />
1989) as well as total root length measurements (Beyrouty, 1996). Roots developing<br />
at this time in flooded rice typically have a horizontal, shallow-growth habit, forming<br />
a root m at at the soil surface (see the review o f root growth literature by Slaton, 1989).<br />
Panicle Formation<br />
Panicle initiation marks the onset o f the reproductive phase <strong>and</strong> begins with the first<br />
(microscopic) differentiation o f bract primordia at the shoot apex. The timing o f this<br />
event is about 30 (± 2 ) days prior to heading in most intermediate-maturing cultivars.<br />
In early-maturing cultivars, panicle initiation can occur only 15 days before heading<br />
(Blanco, 1982). Panicle initiation is not visible to the naked eye. The first visible sign<br />
that it has taken place is referred to as the %reen ring stage, at which point a thin green<br />
b<strong>and</strong> is briefly visible at tlie lowermost internode prior to its elongation (Moldenhauer<br />
et al., 1994). This is the agronomic definition o f panicle initiation <strong>and</strong> is used to tim e<br />
management practices.<br />
Panicle differentiation stage is an agronomic term referring to the growth stage<br />
where panicle form ation is first visible. It occurs when the panicle is 1 to 2 m m long<br />
<strong>and</strong> the internode below it has elongated 1 to 2 cm (Figure 2,1.17). This stage is<br />
often referred to as the half-inch elongation stage. It usually occurs 3 to 5 days after<br />
microscopic panicle initiation.<br />
v m<br />
I i<br />
1. Main culm<br />
2 . Differentiated panicle<br />
3. First elongating internode. 1/2” elongation<br />
4. Node<br />
5. Unelongated internode (root node)<br />
6. Root<br />
Figure 2.1.17. Cross section of the cuim at agronomic panicle differentiation stage. Panicle is 1 to 3<br />
mm long; the first internode below has elongated 1 in.
<strong>Rice</strong> Morphology <strong>and</strong> Development 123<br />
TABLE 2.1.2.<br />
Synchrony of Ponicie Differentiation with Leaf Emergence<br />
Leaf Number from Top<br />
Fourth leaf<br />
Third leaf<br />
Second leaf (penultimate leaf)<br />
First leaf (flag leaf)<br />
Panicle Developmental Stage<br />
Necknode differentiation, initiation of panicle primordia<br />
Branch differentiation<br />
Spikelet differentiation<br />
Microsporogenesis, pollen formation<br />
The process o f panicle differentiation^ or form ation, is from initiation until heading,<br />
This process is synchronous with leaf development (Table 2.1.2) (Yoshida, 1981;<br />
Hoshikawa, 1989; Counce et al., 2000).<br />
The last process to occur prior to heading is microsporogenesis <strong>and</strong> pollen form a<br />
tion. Microsporogenesis can be estimated morphologically by the movement o f the<br />
flag leaf (Yoshida, 1981). Meiosis begins when the flag leaf auricle is 3 cm below the<br />
auricles o f the penultimate leaf (flag leaf auricle still witliin the sheath, but flag leaf<br />
blade partially emerged). The end o f meiosis coincides with the auricle o f the flag leaf<br />
reaching 10 cm above the auricle o f the penultimate leaf, without being iuUy emerged.<br />
The period o f panicle form ation represents a very vulnerable period in the growth<br />
o f a rice plant (Stansel, 1975a; Yoshida, 1981; Hoshikawa, 1989). During this period,<br />
environmental factors such as temperature extremes, drought, nutrient deficiencies,<br />
or toxicities can reduce numbers o f panicle branches <strong>and</strong>/or spikelets <strong>and</strong> reduce<br />
poUen viability. This affects directly the second <strong>and</strong> third yield components (i.e.,<br />
number o f spikelets <strong>and</strong> percentage of filled grains).<br />
Booting is the period where the leaf sheath visibly thickens during panicle formation.<br />
The panicle doubles in size every 3 days during its formation (Nagai, 1959),<br />
<strong>and</strong> booting generally is defined by the first visual evidence of panicle swelling within<br />
the leaf sheath (M oldenhauer et al., 1994), It can also be defined as beginning 10 to<br />
13 days after PI (Vergara, 1991) or 6 days prior to heading (Hoshikawa 1989).<br />
Heading means panicle exsertion from the flag leaf sheath. There is variability in<br />
heading among the culms o f a single plant <strong>and</strong> between plants in the same field, Thus<br />
crop heading may take as long as 14 days. W hen the tiller number is small <strong>and</strong>/or<br />
planting densities high, the crop heading time is relatively short (4 to 5 days) <strong>and</strong><br />
heading is uniform. W hen tillering is prolonged under sparse planting, crop heading<br />
is prolonged (Hoshikawa, 1989). Agronomically, heading is defined as the time when<br />
50% o f booting culms have partially exserted panicles. The degree o f panicle exsertion<br />
is a genetic characteristic o f the plant (Figure 2.1.18) that is selected for in breeding<br />
programs (IB P G R -IR R I, 1980) since poor panicle exsertion can lead to increased<br />
disease incidence (Jennings et al., 1979).<br />
Anthesis (flowering) begins with panicle exsertion or on the following day. As<br />
tlie panicle emerges, spikelets at tlie uppermost tip o f the panicle begin to undergo<br />
anthesis <strong>and</strong> proceeds in a descending order down the panicle. It can take 7 to 10 days<br />
for all the spikelets on the panicle to complete anthesis, with most completed within 5<br />
days. Antliesis refers to events between the opening <strong>and</strong> closing o f the spikelet (floret).<br />
It lasts 1 to 2.5 hours <strong>and</strong> usually occurs between 9:00 a.m . <strong>and</strong> 2:00 p .m . At lower<br />
temperatures <strong>and</strong> on cloudy days, anthesis may begin later <strong>and</strong> take longer, lasting<br />
well into die afternoon. It can be inhibited completely by temperatures below 22°C<br />
or above 32°C, causing sterility (Vergara et al., 1970).
^¡yf (<br />
■ t '<br />
124 The <strong>Rice</strong> Plant<br />
Figure 2.1.18. Categories of panicle exsertion: (/I) well exserted; (fi) itioderately well<br />
exserted; (Q |ust exserted; (i) partly exserted; (f) enclosed. (Adapoted from IBPGR-IRR<br />
During anthesis, the spikelet opens by movement o f the lemma. Anther filaments<br />
elongate <strong>and</strong> are exserted, <strong>and</strong> the tip of the feathery stigma may becom e visible.<br />
Anther filaments continue to elongate to bring the anther completely past the tips<br />
o f the lepima <strong>and</strong> palea. Then the spikelet closes, leaving the anthers outside to die.<br />
Anther dehiscence (pollen shed) occurs just before, or as, the palea <strong>and</strong> lemma open.<br />
Pollen grains thus fall onto the stigma, resulting in rice being predominantly selfpollinated.<br />
Once outside the floret, pollen grains are released into the air <strong>and</strong> may<br />
blow to other spikelets. However, since self-pollination precedes cross-poUination, the<br />
fraction o f cross pollinations is only 1 to 4% on average (Beachell et al., 1938). Pollen<br />
grains are viable for only about 10 minutes after dehiscence, whereas the stigma can<br />
be fertilized for 3 to 7 days. Fertilization o f the ovary by the pollen grain generally is<br />
completed within 5 to 6 hours after pollination. Once pollination is completed, the<br />
ovary becomes rice grain.<br />
Ripening Phase<br />
Grain-Ripening Process<br />
Grain ripening begins 3 weeks after fertilization <strong>and</strong> usually talces 25 to 50 days. It is<br />
accompanied by senescence of leaves <strong>and</strong> roots. The steps in the ripening process are;<br />
• Milk stage. Developing starch grains in the kernel are soft <strong>and</strong> the interior of<br />
the kernel is filled with a white liquid resembling milk.<br />
• Soft dough stage. Starch is beginning to firm, but is still soft.<br />
• Hard dough stage. W hole kernel is firm, moisture content is greater than 20%.<br />
• Mature. W hole kernel is hard <strong>and</strong> moisture content is less than 20% (Yoshida,<br />
1981).<br />
<strong>Rice</strong> yield usually is reported as rough rice at 14% moisture (Yoshida, 1981),<br />
During ripening, grain growth is characterized by increase in size <strong>and</strong> weight of<br />
kernels as starch <strong>and</strong> sugars are translocated from culms <strong>and</strong> leaves. Grain dry weight<br />
increases despite fresh weight decreases due to water loss from 58% to 20% (Yoshida,<br />
1981). All plant parts, including grain, also undergo a color change from green at early<br />
stages to brownish at maturity.<br />
M ost Arkansas cultivars ripen in 35 days, with the exception o f some medium-<br />
grain cultivars that require 45 days (Mars) <strong>and</strong> short-grain cultivars that require 50
<strong>Rice</strong> Morphology <strong>and</strong> Development 125<br />
days (Nortai). Cool temperatures can extend the ripening period to 60 days (Jennings<br />
et al., 1979). Cool temperatures <strong>and</strong> extended ripening periods are associated with<br />
higher yields due to increased grain weights <strong>and</strong>/or improved grain quality with<br />
respect to starch packing. Rapid seed filling results in loose packing o f starch granules,<br />
<strong>and</strong> higher incidence o f chalky grains.<br />
Senescence<br />
The five upper leaves provide photosynthate to the ripening panicle, with the flag leaf<br />
being the primary supplier. These upper leaves have the longest physiological lifespan<br />
on the p lan t In some cultivars, they remain green throughout the ripening phase.<br />
Root length measurements decline after heading. This has been attributed to<br />
senescence, a decrease in numbers o f roots emerging from nodes, <strong>and</strong> a change in root<br />
morphology (Beyrouty et al., 1996; Hoshikawa, 1989). During this developmental<br />
stage, emerging roots have been observed to be shorter <strong>and</strong> to have m ore branching<br />
near the root tip. This gives them a “lion's tail” appearance. These superficial roots<br />
are especially conducive to root mat formation.<br />
REFERENCES<br />
Beachell, H. M ., <strong>and</strong> N. S. Evatt. 1961. Yield performance o f an introduced japónica<br />
rice variety in the Texas Gulf coast. IRCNewsl. 10(4): 1-4.<br />
Beachell, H. M., <strong>and</strong> P. R. Jennings. 1965. Need for modification o f plant type. In The<br />
Mineral Nutrition of the <strong>Rice</strong> Plant, Proceedings o f a Symposium at IRRI, Feb.<br />
1964. Johns Hopldns University Press, Baltimore.<br />
Beachell, H. M ., C. R. Adair, N. E. Jodon, L. L. Davis, <strong>and</strong> J. W. Jones. 1938. Extent of<br />
natural crossing in rice. J. Am. Soc. Agron. 30:743-753.<br />
Beyrouty, C. A., R. J. N orm an, B. R. Wells, N. A. Slaton, B. C. Grigg, Y. H. Teo, <strong>and</strong><br />
E. E. Gbur. 1996. A decade o f rice root characterization studies. In R. J. Norman<br />
<strong>and</strong> B. R. Wells (eds.), Arkansas <strong>Rice</strong> Research Studies, 1995. Ark. Agrie. Exp. Stn.<br />
Res. Ser. 453, pp. 920.<br />
Blanco, P. H. 1982. Growth <strong>and</strong> assimilate partitioning in rice cultivars o f different<br />
maturity groups. M .S. thesis. University o f Arkansas, Fayetteville, AR.<br />
Chang, T. T. 1964. Varietal differences in lodging resistance. IRC Newsl. 13(4): 1- 11.<br />
Counce, P. A., T. J. Siebenmorgen, M. A. Poag, G. E, Holloway, M . F. Kocher, <strong>and</strong><br />
R. Lu. 1996. Panicle emergence o f tiller types <strong>and</strong> grain yield of tiller order for<br />
direct-seeded cultivars. Field Crops Res. 47:235-242.<br />
Counce, P. A., T. C. Keisling, <strong>and</strong> A. J. Mitchell. 2000. A uniform, adaptive <strong>and</strong> objective<br />
system for expressing rice development. Crop Sci. 40(2):436-443.<br />
Falm, A. 1974. Plant Anatomy, 2nd ed. Pergamon Press, Elmsford, NY.<br />
Gravois, K., <strong>and</strong> R. S. Helms, 1996, Seeding rate effects on rough rice yield, head rice,<br />
<strong>and</strong> total milled rice. Agron.}. 88:82-84.<br />
Hanada, K. 1993. Tillers. In T. Matsuo <strong>and</strong> K. Hoshikawa (eds.), Science of the <strong>Rice</strong><br />
Plant Food <strong>and</strong> Agriculture Policy Research Center, Tokyo, pp. 222-258.<br />
Helms, R., <strong>and</strong> N. Slaton. 1994. Water-seeded rice. In R. S. Helms (ed.). <strong>Rice</strong> Production<br />
H<strong>and</strong>book. Extension Service Print Shop, Little Rock, AR, pp. 21-23.<br />
Hoshikawa, K. 1989. The Growing <strong>Rice</strong> Plant: An Anatomical Monograph. Nobunkyo,<br />
Tokyo.
126 The <strong>Rice</strong> Plant<br />
IBPG R -IR R I <strong>Rice</strong> Advisory Committee. 1980. Descriptors for <strong>Rice</strong> Oryza sativa L<br />
International <strong>Rice</strong> Research Institute, Manila, The Phñippines.<br />
Jennings, P, R. 1964. Plant type as a rice breeding objective. Crop Sei 4:13-15.<br />
Jennings, P. R., <strong>and</strong> J. de J. Josué. 1964. Effect of heat on breaking seed dormancy in<br />
rice. Crop Sei 4:530-533.<br />
Jennings, P. R., W. R. Coffman, <strong>and</strong> H. E. Kauffman. 1979. <strong>Rice</strong> Improvement. International<br />
<strong>Rice</strong> Research Institute, Manila, The Philippines.<br />
Juliano, B. O., 1972, Biochem ical properties o f rice. In B. O. Juliano (ed.). <strong>Rice</strong>: Chemistry<br />
<strong>and</strong> Technology. American Association o f Cereal Chemists, St. Paul, M N, pp.<br />
175-205.<br />
Juliano, B. O., <strong>and</strong> D. B. Bechtel. 1972. The rice grain <strong>and</strong> its gross composition.<br />
In B. O. Juliano (ed.). <strong>Rice</strong>: Chemistry <strong>and</strong> Technology. American Association o f<br />
Cereal Chemists, St. Paul, MN, pp. 17-58.<br />
Kaufman, P. B, 1959. Development o f the shoot of Oryza sativa L. III. Early stages in<br />
histogenesis of the stem <strong>and</strong> ontogeny o f the adventitious root. Phytomorphology<br />
9:382-404.<br />
Keisling, T, C., B. R. Wells, <strong>and</strong> G. L. Davis. 1984. <strong>Rice</strong> Management Decision Aids Based<br />
upon Thermal Time Base 50°F. Ext. Comput. Tech. BuU. 1. Cooperative Extension<br />
Service, University o f Arkansas, U.S. Departm ent o f Agriculture <strong>and</strong> cooperating<br />
county governments.<br />
Khush, G. S. 1997. Origin, dispersal, cultivation <strong>and</strong> variation o f rice. Plant Mol. Biol<br />
35:25-34.<br />
MiUer, B. C., T. C. Foin, <strong>and</strong> J. E. Hill. 1993. CARICE: a rice model for scheduling <strong>and</strong><br />
evaluating management actions. Agron. /. 85:938-947.<br />
Moldenhauer, K. A. K., B. Wells, <strong>and</strong> R. Helms. 1994. <strong>Rice</strong> growth stages. In R. S.<br />
Helms (ed.). <strong>Rice</strong> Production H<strong>and</strong>book. Cooperative Extension Service Print<br />
Shop, Little Rock, AR, pp. 5-12.<br />
Moldenhauer, K. A., E, T. Champagne, D. R. McCaskill, <strong>and</strong> H. Guraya. 1998. Functional<br />
products from rice. In G. Mazza (ed.), Functional Foods: Biochemical <strong>and</strong><br />
Processing Aspects. Technom ic Publishing, Lancaster, PA, pp. 71-90.<br />
Nagai, I. 1959. Japónica rice; its breeding <strong>and</strong> culture. Yokendo LTD., Tokyo, p, 843.<br />
Nemoto, K., S. M orita, <strong>and</strong> T. Baba. 1995. Shoot <strong>and</strong> root development in rice related<br />
to the phyllochron. Crop Sei 35:24-29.<br />
Norman, R. J., N. A. Slaton, <strong>and</strong> K, A. K. Moldenhauer. 1998. Development o f the<br />
D D 50 database for new rice cultivars. In R. J. Norman <strong>and</strong> T. H. Johnston, (eds.),<br />
B. R. Wells <strong>Rice</strong> Research Studies, 1997. Ark. Agrie, Exp. Stn. Res. Ser. 460, pp. 144-<br />
146.<br />
Ntamatungiro, S., R. S. Helms, B. R. Wells, <strong>and</strong> R. J. Norman. 1993. Influence of<br />
Uneven Emergence on <strong>Rice</strong> Grain Yield, Yield Components <strong>and</strong> Milling Quality.<br />
Univ. Ark. Agrie. Exp. Stn. Bull. 936, Fayetteville, AR.<br />
Redona, E. D., <strong>and</strong> D. J. Mackill. 1996. Genetic variation for seedling vigor traits in<br />
rice. Crop Sei 36:285-290.<br />
Slaton, N. A., 1989. Evaluation o f shoot growth <strong>and</strong> environment on rice root growth<br />
determined using several root study techniques. M .S. thesis. University o f Arkansas,<br />
Fayetteville, AR.<br />
Stansel, J. W. 1975a. The rice plant: its development <strong>and</strong> yield. In She Decades of <strong>Rice</strong><br />
Research in Texas. Res. Monogr. 4. Texas Agricultural Experim ent Station, Texas<br />
A 8cM University System, <strong>and</strong> U.S. Departm ent o f Agriculture, pp. 9 -2 1 .
<strong>Rice</strong> Morphology <strong>and</strong> Development 127<br />
Stansel, J. W. 1975b. Effective utilization o f sunlight. In Six Decades of <strong>Rice</strong> Research<br />
in Texas. Res. Monogr. 4. Texas Agricultural Experiment Station, Texas A&M<br />
University System, <strong>and</strong> U.S, Department o f Agriculture, pp. 9-21.<br />
Takahashi, N, 1984. Seed germination <strong>and</strong> seedling Growth. In S. Tsunoda <strong>and</strong> N. Ta-<br />
kahashi (eds.), Developments in Crop Science, Vol. 7, Biology of <strong>Rice</strong>. Elsevier<br />
Science, New York, pp. 71-88,<br />
Tanaka, A. 1965a. Examples o f plant performance. In The Mineral Nutrition of the <strong>Rice</strong><br />
Plant, Proceedings o f a Symposium at IRRI, Feb. 1964. Johns Hopkins University<br />
Press, Baltimore, pp. 3 7 ^ 9 .<br />
Tanalca, A. 1965b. Plant characters related to nitrogen response in rice. In The Mineral<br />
Nutrition o f the <strong>Rice</strong> Plant, Proceedings of a Symposium at IRRI, Feb. 1964. Johns<br />
Hopkins University Press, Baltimore, pp. 4 19-435.<br />
Vergara, B. S. 1991. <strong>Rice</strong> plant growth <strong>and</strong> development. In B. S. Luh (ed.), <strong>Rice</strong><br />
Production, Vol. I. Van Nostr<strong>and</strong> Reinhold, New York, pp. 13-22.<br />
Vergara, B. S., T. M. Chu, <strong>and</strong> R. M. Vísperas. 1970. Effect o f temperature on the<br />
anthesis o f IR 8. IRCNewsl 19(3);11-17.<br />
Wells, B, R., <strong>and</strong> W. F. Faw. 1978. Short-statured rice response to seeding <strong>and</strong> N rates.<br />
Agron. J. 70:477-480.<br />
Yoshida, S. 1981. Fundamentals o f <strong>Rice</strong> Crop Science. International <strong>Rice</strong> Research In <br />
stitute, M anila, The Philippines.
Chopter<br />
2 .2<br />
<strong>Rice</strong> Physiology<br />
Paul A. Counce<br />
<strong>Rice</strong> Research <strong>and</strong> Extension Center<br />
University of Arkansas<br />
Stuttgart, Arkansas<br />
David R. Gealy<br />
Dale Baimpers National <strong>Rice</strong><br />
Research Center<br />
USDA-ARS<br />
Stuttgart, Arkansas<br />
Shi-Jean Su sa n a Sung<br />
USDA-FS Southern Research Station<br />
Institute of Tree Root Biology<br />
Athens, Georgia<br />
INTRODUCTION<br />
ROLE OF COORDINATED FUNCTION IN DEVELOPMENT<br />
PLANT DEVELOPMENT<br />
GERMINATION AND SEEDLING DEVELOPMENT<br />
PHOTOSYNTHESIS<br />
AERENCHYMA<br />
REPRODUCTIVE DEVELOPMENT<br />
GRAIN DEVELOPMENT<br />
PATH OF THE CARBON IN THE ENDOSPERM<br />
RESPONSES, SIGNALS, HORMONES, AND PROTEIN MODIFICATIONS<br />
MINERAL NUTRITION OF RICE, PLANT ABNORMALITIES, AND ASSOCIATED STRESSES<br />
CONCLUSION<br />
REFERENCES<br />
INTRODUCTION<br />
Physiology occurs in physical space through chemical reactions constrained by anatomy<br />
<strong>and</strong> morphology, yet guided by genetics. Physiology has been called the logic<br />
of life. Genes encode structural <strong>and</strong> functional proteins. These proteins are subsequently<br />
processed to produce enzymes that direct <strong>and</strong> govern the biochemical processes<br />
involved in the physiology o f the plants. The enzymes do the work o f tlie plant<br />
in a controlled, coordinated manner so that life can continue <strong>and</strong> development can<br />
proceed.<br />
<strong>Rice</strong>: Origin, History, Technology, <strong>and</strong> Production, edited by C. Wayne <strong>Smith</strong><br />
ISBN 0-471-34516-4 © <strong>2003</strong> )ohn Wiley & Sons, Inc,<br />
129
130 The <strong>Rice</strong> Plant<br />
The genes <strong>and</strong> gene order o f tlie rice plant have very m uch in com m on with other<br />
plants, especially with other grass species (Devos <strong>and</strong> Gale, 2000). Consequently,<br />
literature that describes plant physiological processes in general <strong>and</strong> in detail are cited.<br />
Some processes, such as selective uptake <strong>and</strong> deposition o f silica are somewhat different<br />
for rice compared with m ost other plant species. <strong>Rice</strong> takes up more silica than<br />
do m ost crop plant species. We discuss nutritional disorders o f rice, which manifest<br />
themselves differently in rice compared with other plant species. We discuss the grainfilling<br />
process in detail because of its econom ic importance. Photosynthesis is treated<br />
very well in other places (Taiz <strong>and</strong> Zeiger, 1998), so our treatm ent o f photosynthesis<br />
is limited.<br />
Initiation o f growth from the quiescent stage begins seedling development. During<br />
vegetative growth <strong>and</strong> development, a succession o f leaves is formed, with each<br />
leaf going through initiation, elongation, maturity, <strong>and</strong> senescence. The leaves are<br />
subtended by nodes, internodes, two rows of nodal roots, <strong>and</strong> in some cases, a tiller<br />
bud. After the last leaf on the culm initiates, the apical meristem initiates <strong>and</strong> begins<br />
to differentiate. This differentiation leads to development o f the panicle, which<br />
successively forms branches, florets, <strong>and</strong> gametes. Subsequently, the panicle exerts,<br />
ovaries are fertilized, embryos <strong>and</strong> endosperm exp<strong>and</strong>, <strong>and</strong> endosperm fills <strong>and</strong> dries<br />
down. Even after drying down, the seed continues to change <strong>and</strong> develop internally,<br />
which leads to significant changes in milling quality during storage (Hamaker et al.,<br />
1993), The relevant physiology is constrained within this space <strong>and</strong> tim e unity o f plant<br />
development.<br />
ROLE OF COORDINATED FUNCTION IN DEVELOPMENT<br />
Plant development is mathematically regular <strong>and</strong> follows repeatable leaf <strong>and</strong> seed<br />
arrangement patterns (Jean, 1994). The repeatable arrangement is guided by the<br />
microtubules, which guide the <strong>production</strong> o f cell walls within <strong>and</strong> between individual<br />
cells (Taiz <strong>and</strong> Zeiger, 1998; Baskin, 2000) <strong>and</strong> lead to the eventual repeating patterns<br />
of leaf arrangement around the orthostichy.<br />
PLANT DEVELOPMENT<br />
Plant development is under tight genetic <strong>and</strong> physiological control. "The mode in<br />
which one cell forms many; <strong>and</strong> how these, dependent on the influence o f the former,<br />
assume their proper figure <strong>and</strong> arrangement, is exactly the point upon which the<br />
whole knowledge o f plants turns; <strong>and</strong> whosoever does not propose this question . . .<br />
or does not reply to it, can never connect a clear scientific idea with plants <strong>and</strong> tlieir<br />
life” (Schleiden, 1842, quoted in Taiz <strong>and</strong> Zeiger, 1998).<br />
Plant development is guided by genetic inform ation tliat leads to the form ation of<br />
proteins which function to guide cell wall development (Baskin, 2000), Consequently,<br />
the enzymes involved in laying down cell walls are guided to regularity in all normal<br />
plant tissues. Once these tissues have begun to senesce, the degradation o f the cell<br />
com ponents <strong>and</strong> cell walls are likewise determined by orderly biochem ical activities
<strong>Rice</strong> Physiology 131<br />
stage**^ {SO Si S2 S3 VI V2 V3 V4 V5 V6 V7 V8 V9 VIO Vil V12 V13<br />
RO R1<br />
R2 R3 R4 R5 R6 R7 R8 R9<br />
Photosynthesis<br />
Nutrient Uptake<br />
Proteolysis, amino acid <strong>and</strong> protein synthesis<br />
Protection from photo oxidative damoge<br />
Transport of nutrients including amino acids <strong>and</strong> sugars<br />
Caryopsis enlargement<br />
6rain filling<br />
6ratn dry down<br />
Figure 2.2.1.<br />
Physiological processes throughout the stages of rice development.<br />
regulated by the plant’s genetics (Taiz <strong>and</strong> Zeiger» 1998). Several physiological processes<br />
are conducted at all stages o f a plant’s life, whereas others are needed only at<br />
certain times (Figure 2 .2, 1).<br />
GERMINATION AND SEEDLING DEVELOPMENT<br />
Plant growth begins at the quiescent state with the seed’s embryo sending gibberellic<br />
acid to the aleurone layer where amylase proteins are transcribed. These proteins are<br />
transported to the starchy endosperm where the starch is mobilized to provide energy<br />
to the developing embryo. The amylase substrates are branched <strong>and</strong> unbranched<br />
starch molecules. The products are maltose <strong>and</strong> shorter-chained starch molecules.<br />
<strong>Rice</strong> seeds im bibe water at adequate temperature in the presence o f oxygen (Yo-<br />
shida, 1981). Counce et al. (2000) described four stages o f rice seedling development<br />
(Figure 2 .2 ,2). Chaudhary <strong>and</strong> Ghildyal (1969) <strong>and</strong> Alocilja <strong>and</strong> Ritchie (1991) indicate<br />
tliat ( 1) m inim um temperatures for rice germination <strong>and</strong> development are<br />
between 6 <strong>and</strong> 8°Q (2) the optim um temperature for rice germination <strong>and</strong> development<br />
is 37°C; <strong>and</strong> (3) the maximum temperature for rice germination is 41°C <strong>and</strong><br />
for development is 44°C. The m ajority o f temperature studies on rice germination<br />
indicate the optim um to be 30 to 32'’C (N. Takahashi, 1995c). In dry-seeded rice,<br />
the radicle normally appears first, whereas in water-seeded (submerged) rice, the<br />
radicle is suppressed <strong>and</strong> the coleoptile emerges first. This appeared to be related<br />
to the low-oxygen environment o f water-seeded rice compared to m ore oxygen for<br />
the dry-seeded rice. N. Takahashi (1995a) suggests that emergence o f the suppressed<br />
radicle is related to water in tliat formation of the radicle is sensitive to the degree
132
Rite Physiology 133<br />
^1<br />
of hydration in the root zone. The greater tlie degree o f hydration, the greater the<br />
suppression o f the radicle (N. Takahashi, 1995a). In rice seeds germinated in aerated<br />
water, the coleoptiles.emerge before the radicles (Counce et al., 2000). After growth<br />
stage S3 in a water-seeded culture, the flood is sometimes removed to allow the rice<br />
to peg down (to allow the seminal root system to penetrate the soil <strong>and</strong> anchor the<br />
plant).<br />
<strong>Rice</strong> goes into dorm ancy after harvest in some cases (Cohn <strong>and</strong> Hughes, 1981;<br />
N. Takahashi, 1995b). Domesticated rices frequently lack seed dormancy, whereas<br />
their wild Oryza relatives typically produce dorm ant seed. Red rice is a wild ( O. sativa<br />
L.) relative o f domestic rice with a red testa (Juliano <strong>and</strong> Bechtel, 1985), Red rice<br />
<strong>and</strong> other wild Oryza species have extensive mechanisms for survival, including seed<br />
dormancy (N. Takahashi, 1995bi Vaughan et al., 1999)'.<br />
After growth stage S3, the first true (complete) leaf develops. Vegetative development<br />
for a rice cultivar with 13 leaves on tlie main stem are presented in Figure 2.2.3.<br />
(Cultivars differ in the total number o f leaves produced on the main stem.) Events<br />
occur in the following order for each node o f a rice plant: ( 1) leaf initiation, (2) leaf<br />
elongation, (3) leaf blade maturation, (4) collar form ation, (5) leaf sheath elongation,<br />
(6) node form ation, <strong>and</strong> (7) internode elongation. Internode elongation occurs only<br />
for the final five internodes o f the rice main stem (Figure 2.2.4).<br />
PHOTOSYNTHESIS<br />
Photosynthesis is described well elsewhere (e.g., Taiz <strong>and</strong> Zeiger, 1998) <strong>and</strong> is critical<br />
to the life of rice (<strong>and</strong> other green plants). Photosynthesis is accomplished by<br />
the conversion o f light energy into chemical energy to fix carbon from CO 2 into<br />
carbohydrates. All the yield o f a plant is a result o f photosynthesis. The regulation<br />
o f photosynthesis over a plant’s life affects the growth <strong>and</strong> yield o f the rice plant<br />
(Ishii, 1995a,b). In particular, the integrated photosynthesis o f the flag leaf over the<br />
grain-filling period is correlated directly with per cuhn yield (Ishii, 1995a; Yoshida,<br />
1972). Photosynthesis is highly related to the presence <strong>and</strong> amount of sinks (such as<br />
filling rice grains) for carbohydrates (Evans, 1975). Area yield is determined by yield<br />
com ponents (num ber o f culms per unit area, num ber o f spikelets per culm, filled<br />
spikelet percentage, <strong>and</strong> grain weight). The yield components are in turn determined<br />
by photosynthetic rate. The area yield is also related to the leaf area index (LAI; ratio o f<br />
leaf area to l<strong>and</strong> area). Usually, the yield-to-LAI relationship is positive (Murata <strong>and</strong><br />
Matsushima, 1975; Counce, 1992). The relationship o f LAI varies greatly with the<br />
cultural system, plant type, <strong>and</strong> the growth stage at which LAI is measured (M urata<br />
<strong>and</strong> Matsushima, 1975). For example, prior to the availability o f grass herbicides, the<br />
rice crop in the dry-seedbed, direct-seeded culture o f the southern U.S. rice-growing<br />
area was composed o f large, fast-growing rice plants that could compete successfully<br />
with grass weeds. In such a system, nitrogen fertilization was delayed until internode<br />
elongation (growth stage R l) , to avoid lodging. Consequently, the timing o f the m idseason<br />
nitrogen application in the southern United States was crucial. Elim ination o f<br />
grass weeds by herbicide use allowed development o f shorter rice cultivars with more<br />
erect leaves, higher LAI, higher harvest indices, <strong>and</strong> higher yields.<br />
In transplanted culture, where cultivation reduces the im pact o f weeds <strong>and</strong> the<br />
plants grow smaller <strong>and</strong> m ore compact, earlier nitrogen fertilization o f rice can be
<strong>Rice</strong> Physiology 137<br />
Growth Stage<br />
50<br />
51<br />
52<br />
53<br />
VI<br />
V2<br />
V3<br />
V4<br />
V5<br />
V6<br />
V7<br />
V8<br />
Morphological Development<br />
Coieoptiie or radicle emergence<br />
Coleoptile <strong>and</strong> radicle emergence<br />
Prophyll emergence from coleoptile<br />
Usual nodal root formation<br />
Tillering possible<br />
Early Tillering<br />
Mid-Tillering<br />
I Late Tillering<br />
Normal Tillering<br />
Vr-^ V9<br />
Vf.j<br />
VIO<br />
Vr.2 Vll<br />
RO<br />
lU<br />
• Panicle initiation ] Green ring<br />
¡Panicle branch diflferentation<br />
1st<br />
2nd<br />
Vf-, V12<br />
Vi. V13 R2<br />
R3<br />
R4<br />
Glume, lemma, palea differentiation<br />
I Miorosporogenesis |Boot split<br />
50% Heading<br />
Pollination<br />
3rd<br />
4th<br />
Pedimcle<br />
(intomode under<br />
flag leaf slieatli<br />
bearing panicle)<br />
.a<br />
•I<br />
R5<br />
R6<br />
R7<br />
R8<br />
R9<br />
Caiyopsis expansion<br />
Milk Stage<br />
ISoft Dough Stage<br />
I Hard Dough Stage<br />
Grain Dry-Down<br />
Grain Fill<br />
Continued developmental changes after harvest<br />
I “Physiological maturity’'<br />
Figure 2.2.4. <strong>Rice</strong> developmenlal timeline. (From Counce et al., 2000.)<br />
done <strong>and</strong> can increase yields substantially. W ith the development o f effective herbicides,<br />
rice cultivars with reduced mature height have been selected that can yield weU<br />
in response to nitrogen, without lodging which would reduce effective crop yield.<br />
Tillering in rice, as in other grasses, proceeds positively when plant nitrogen<br />
contents are at or above 3.5% , <strong>and</strong> solar irradiance (light) is sufficient to stimulate<br />
tiller development (M urata <strong>and</strong> Matsushima, 1975). Phosphorus levels below 0.25%<br />
in the main stem o f the plant reduces tillering. Optimum water temperatures for tiller<br />
emergence are 16°C at night <strong>and</strong> 31°C during the day. Water temperatures above or
138 The Ríce Plant<br />
below 3 1°C therefore lim it tiller emergence. Tillering proceeds as long as light reaches<br />
the base of the rice plant, beginning at V3 or V4, <strong>and</strong> normally ending around V 8 for<br />
direct, dry-seeded rice. Tillering is enhanced by thin st<strong>and</strong>s (low plant populations per<br />
unit area). Isolated plants can easily produce 30 to 40 tillers, which reach growth stage<br />
R 4 within 3 days o f the m ain stem (Counce et a l, 1996). Tillering in rice accounts<br />
for large amounts o f the rice crop's yield. Some tillers almost always die prior to<br />
producing grain. The result o f dead, nonproductive tillers may be inconsequential<br />
in some cases, but in other cases the yield potential may be decreased, due to tiller<br />
death <strong>and</strong> to reduction in tillers that produce grain. Many o f the nutrients o f dying<br />
tillers are translocated to the rest o f the plant (M urata <strong>and</strong> Matsushima, 1975).<br />
Until internode elongation begins, rice appears to store starch mainly in leaf<br />
sheaths. The nodal roots, <strong>and</strong> even seminal roots, typically live until the grain is<br />
mature. Consequently, the roots could potentially store starch. However, it appears<br />
that the roots do not store much carbohydrate for growing the rice crop, although<br />
roots do contain starch. Leaf sheaths have the potential for storing either starch or<br />
sucrose, <strong>and</strong> they do store either or both at various times in leaf development, especially<br />
on fhe top five elongating internodes as the leaves grow longer <strong>and</strong> leaf sheaths<br />
are not penetrated by the nodal roots. These top internodes rarely form any nodal<br />
roots, except for very short roots, which even more rarely penetrate their covering<br />
leaf sheaths. It is well known that leaf sheaths <strong>and</strong> cukns store considerable amounts<br />
o f carbohydrates, which can potentially increase rice yields (Stansell, 1975; Yoshida,<br />
1981; Dat <strong>and</strong> Peterson, 1983a,b). Turner <strong>and</strong> Jund (1993) found that much o f the<br />
rattoon rice crop yield was attributable to starch stored in leaf sheaths <strong>and</strong> culms of<br />
the first crop. Consequently, there are several reasons to think that starch stored in<br />
the leaf sheaths <strong>and</strong> culms is a potential source o f higher rice yields. Even with large<br />
amounts o f the rice leaves removed, rice yields can be quite high as a result o f stored<br />
carbohydrates (Counce, unpublished data; Counce et a l, 1994a,b).<br />
AERENCHYMA<br />
W ithin 24 hours after soil is flooded, the oxygen supply o f the soil is depleted by<br />
aerobic bacteria seeking oxidants (Ponnamperuma, 1972). Consequently, a rice plant<br />
is growing in hypoxic (low-oxygen) soil conditions by 1 day after flooding. In carefully<br />
excavated rice plants, all roots will be present, including the seminal roots, <strong>and</strong> all will<br />
be functional. The roots require oxygen to stay alive <strong>and</strong> to function. In m ost mineral<br />
soils that are flooded, the roots will be coated with ferrous iron. This iron appears to<br />
be associated with siderophores. The conversion o f ferric iron to ferrous iron requires<br />
oxygen. The leaves die within 3 to 6 phyllochrons o f their elongation. Consequently<br />
the leaves cannot provide the conduit for oxygen. The nodes <strong>and</strong> interriodes, however,<br />
persist. These nodes <strong>and</strong> internodes provide the conduit for oxygen from above the<br />
floodwater into tlie roots. The tissue capable o f conducting the oxygen is aerenchyma,<br />
which is formed by an orderly killing o f certain tissues within the plant to produce<br />
large intercellular spaces (D angl et a l, 2000). This orderly death o f tire tissues in<br />
organisms is called programmed cell death <strong>and</strong> occurs in response to a number of<br />
stimuli (Dangl et a l, 2000). After a period o f flooding aerenchyma form <strong>and</strong> conduct<br />
oxygen to the rice roots (Raskin <strong>and</strong> Kende, 1985; Sharm a et a l, 1994). Thus, the<br />
conduit for oxygen in flooded rice is the continuous line o f nodes <strong>and</strong> internodes<br />
containing aerenchyma.
Ríce Physiology<br />
REPRODUCTIVE DEVELOPMENT<br />
<strong>Rice</strong> reproductive developmental stages have been distinguished by objective m orphological<br />
developmental criteria by Cpunce et al. (2000) (Figure 2.2.5). The initiating<br />
panicle (growth stage RO) begins with a single cell. Subsequently, panicle branches<br />
form at growth stage R l, <strong>and</strong> at this stage o f growth the nm nber o f potential grains<br />
per panicle are beginning to be determined (Yoshida, 1981). Actual grain number per<br />
panicle is readjusted continually until the R5 or even R 6 growth stages. After reaching<br />
growth stage R 6, grains normally fill <strong>and</strong> complete their development.<br />
GRAIN DEVELOPMENT<br />
The development o f the grain proceeds over a relatively long period o f the plant’s<br />
development. At anthesis, the pollen tube germinates <strong>and</strong> elongates to connect to<br />
the ovaries to insert one male gamete into the egg nucleus <strong>and</strong> one into the polar<br />
nuclei (Hoshikawa, 1989). The growth o f the pollen grain requires energy provided<br />
by the action o f acid invertase in the elongating pollen tube. Upon fertilization, the<br />
embryo <strong>and</strong> endosperm must be provided with nutrients, the prim ary one being<br />
sucrose. Sucrose is broken down in rapidly exp<strong>and</strong>ing tissue in various parts o f the<br />
plant through acid invertase located in the vacuole. The caryopsis elongates, because<br />
o f cell wall expansion, to the m axim um space o f the lemma <strong>and</strong> palea (the “hull”<br />
for rice). Subsequently, the cells in the endosperm fill primarily with starch. Cells in<br />
the aleurone layer are filled primarily with oil <strong>and</strong> protein. Cells in the subaleurone<br />
layer have starch, oil, <strong>and</strong> protein. Cells in the starchy endosperm contain starch<br />
<strong>and</strong> a small amount (6 to 7% ) o f protein (Juliano <strong>and</strong> Bechtel, 1985). The genes o f<br />
the cereals are, in general, very similar <strong>and</strong> are in the same order (Bennetzen, 2000;<br />
Devos <strong>and</strong> Gale, 2000; Freeling, 2001). It dearly follows that the cereals share many o f<br />
the same enzymes, particularly enzymes related to the grain-filling process. We have<br />
learned a considerable am ount o f inform ation about the biochemistry/enzymology<br />
o f the grain-filling process from cereals, particularly maize <strong>and</strong> wheat. The process o f<br />
producing starch from imported sucrose is well documented <strong>and</strong> applicable to rice.<br />
PATH OF THE CARBON IN THE ENDOSPERM<br />
The primary transport carbohydrate in rice <strong>and</strong> other vascular plants is sucrose (Avigad<br />
<strong>and</strong> Dey, 1996; Taiz <strong>and</strong> Zeiger, 1998). Beginning at fertilization o f the egg nuclei<br />
<strong>and</strong> polar nuclei, the caryopsis begins to form (growth stage R4) <strong>and</strong> elongates<br />
(growth stage R5) to the length o f the lem m a <strong>and</strong> palea (growth stage R 6). Sucrose<br />
is imported during this time period (growth stage R 5), <strong>and</strong> the prim ary sucrolytic<br />
enzyme powering this cell elongation is acid invertase:<br />
sucrose —> glucose + fructose (1 )<br />
After the caryopsis has elongated, the grain-filling process begins, since at the<br />
end o f cell elongation there is no starch deposition in the cells. There are two cellular<br />
com partments where most o f the synthesis biochem istry for the grain-filling process<br />
takes place: the cytosol <strong>and</strong> the plastid (Figure 2.2.6).
Growtb Stage<br />
RO<br />
R1<br />
R2<br />
R3<br />
R 4<br />
Morphological<br />
Marker<br />
Panicle<br />
development<br />
has initiated<br />
Panicle branches<br />
have formed<br />
Flag leaf<br />
collar formation<br />
Panicle exertion<br />
from boot, tip o f<br />
panicle is above<br />
collar o f flag leaf<br />
One or more florets<br />
on the main stem<br />
panicle has reached<br />
anthesis<br />
Illustration<br />
H<br />
Figure 2.2.5. Reproductive gtoiwth stages. (From (ounce et a!., 20 0 0 .)<br />
41:,:<br />
t Other authors have chosen to use terms physiological maturity or cessation o f dry matter accumulation. W e avoid these terms because,<br />
for ric^ such determinations are difficult or impossible to make with any known morphological marker.<br />
:|; The brown hull indicates the grain has begun to dry.<br />
S Figure 2.2.5. (Continued)
142 The <strong>Rice</strong> Plant<br />
CYTO SO L<br />
Sucrose<br />
Ap<br />
PLASTID<br />
Am<br />
Fructose + UDPGIc<br />
.ATP yPPi<br />
UTP a"<br />
-► G lc-I-P -■<br />
l/ATP<br />
D-enzyme n ®<br />
DBE<br />
Glc-1-P<br />
l.'A t p<br />
SS<br />
A D P G Ic -- -^ "» - ADPGIc<br />
Figure 2.2.6. General pathway of starch biosynthesis. (From Myers<br />
et al., 2000, copyrighted by the American Society of Plant Physiologists<br />
<strong>and</strong> reprinted with permission.)<br />
In the cytosol the direct route o f carbon is from imported sucrose. During grain<br />
filling (growth stage R6), sucrose synthase breaks down sucrose, but the action of<br />
sucrose synthase is reversible:<br />
sucrose ^ UDP-glucose + fructose (2)<br />
During grain filling the primary sucrolytic enzyme in rice endosperm is one<br />
or more o f the isoforms of sucrose synthase (Avigad <strong>and</strong> Dey, 1996). Two forms of<br />
sucrose synthase have been found in corn endosperm: Susl <strong>and</strong> S h i, A lesion in the<br />
Shi isoform leads to the shrunken 1 mutant o f maize. Its sweet flavor comes from<br />
the lesion o f sucrose synthase, which leads to an inadequate breakdown o f sucrose for<br />
subsequent <strong>production</strong> o f starch. Huang et al. (1996) have identified three sucrose<br />
synthase isogenes for rice. These genes code for different forms o f the enzyme, which<br />
are active in different tissues <strong>and</strong> stages of development.<br />
Next, the glucose moiety, UDP-glucose (2), is converted to glucose-1-phosphate<br />
by the action o f UDP-glucose pyrophosphorylase:<br />
:■ :<br />
UDP-glucose + PPi ^ glucose-1-phosphate •+■UTP (3)<br />
(Fructose can also be converted to glucose phosphates <strong>and</strong> subsequently into starch<br />
via the actions o f several enzymes.) Step (3) m ust be faster than step (2), This is a<br />
requirement for grain filling. W ithout this step preventing buildup o f UDP-glucose,<br />
breakdown o f sucrose by sucrose synthase would be followed immediately by its<br />
resynthesis (Avigad <strong>and</strong> Dey, 1996).<br />
The G -l-P is then either transported into the plastid or converted to G -6-P via the<br />
action o f phosphoglucose isomerase. At this point, the first step necessary for starch<br />
synthesis begins in either the amyloplast or the cytosol with the action o f ADP-glucose<br />
pyrophosphorylase (AGP):<br />
G -l-P -f ATP ADP-glucose -h PPi (4)<br />
Just as cytoplasmic <strong>production</strong> of glucose phosphates is probably lim ited by sucrose<br />
synthase, starch <strong>production</strong> is probably limited in the plastid by AGP, In maize, <strong>and</strong><br />
1 T-
Ríce Physiology<br />
perhaps in rice, AGP is located in the cytosol (Shannon et al„ 1998). ADP-glucose<br />
is the starting point for starch synthesis. Subsequent starch synthesis reactions talce<br />
place in the plastid. After initiation o f the starch molecule, subsequent single glucosyl<br />
units additions to either branched or straight chains are accomplished by starch<br />
synthase:<br />
starch chain -f ADP-glucose -> starch chain + glucosyl unit + ADP<br />
Branching o f starch chains is accomplished by the starch branching enzyme (SBE;<br />
Figure 2.2,7). During starch synthesis, branching, debranching <strong>and</strong> resizing o f the<br />
starch molecule are necessary in what is a continual shaping, assembly, disassembly,<br />
<strong>and</strong> reassembly in the developing endosperm by the actions o f starch synthase,<br />
starch branching enzyme, D-enzyme, <strong>and</strong> starch debranching enzyme (Sm ith et al.,<br />
1997; Taylor, 1998; Myers et al., 2000). These activities result in a highly structured<br />
granule with starch packed in alternating zones o f more branched <strong>and</strong> less branched<br />
amylopectin (Taylor, 1998; Myers et al., 2000). The starch structure in rice <strong>and</strong> other<br />
grains is quite highly repeating, although it is subject to changes due apparently to<br />
the environment, particularly the temperature. <strong>Rice</strong> starch granules are smaller than<br />
starch granules o f other cereals. Soluble starch synthase is more sensitive to high<br />
temperatures than m ost other plant enzymes (Keeling et al., 1994). High temperatures<br />
during grain fiUing also lead to challdness in rice grains (Yoshida <strong>and</strong> Hai'a,<br />
1977; Fitzgerald, personal com m unication). This challdness is potentially the result<br />
o f reduced activity o f starch synthase or SBE. The starch synthase enzyme also has a<br />
requirement for potassium for optimal activity o f the enzyme (Marschner, 1995).<br />
The first element o f the process is the <strong>production</strong> o f individual starch molecules.<br />
The second com ponent o f the process o f rice grain filling is the com bining o f these<br />
starch molecules into granules (Sm ith et al., 1997; Myers et al., 2000). The granules are<br />
formations o f alternating layers of crystalline <strong>and</strong> amorphous lameUas (Figure 2.2.8)<br />
For rice in Arkansas, Downey <strong>and</strong> Wells (1975) found a positive correlation<br />
between rough rice yields <strong>and</strong> the number o f hours below 21“C (70° F) during the<br />
period between 40 <strong>and</strong> 110 days after emergence. We found that a 6°C (from 18°C<br />
to 24°C) increase in temperatures between midnight <strong>and</strong> 5 a m . resulted in a 5 to 7%<br />
reduction in head rice yields (P. A. Counce, unpublished data).<br />
RESPONSES, SIGNALS, HORMONES, AND PROTEIN MODIFICATIONS<br />
Although plants cannot think, they do process inform ation. The discovery o f several<br />
compounds called hormones was an early manifestation that plants can process information.<br />
Plants are exposed continuously to a num ber o f external signals to which they<br />
respond. Som e o f those responses are internal <strong>and</strong> lead to the synthesis o f horm ones.<br />
There are at least nine classes of hormones: auxins, abscisic acid, brassinosteroids,<br />
cytokinins, ethylene, gibberellins, jasm o n k acid, polypeptide hormones, <strong>and</strong> salicylic<br />
acid (Crozier et al., 2000; Ryan <strong>and</strong> Pearce, 2001). The hormones often have pronounced<br />
effects on plant growth <strong>and</strong> development when applied at relatively high<br />
concentrations: application o f gibberellins causes internodes to elongate, application<br />
o f cytokinins may cause plants to green up, <strong>and</strong> application o f abscisic add may cause<br />
seeds to stop the germination process. W ithin the plant, however, the amounts of
* +<br />
0 '^ L -/ ^ O H HO<br />
D-enzyme:<br />
Figure 2 2.7.<br />
Diogrommetic lepiesentotion of stoich biosynthesis. (From Myers et ol., 2000, copyrighted by<br />
the American Society of Plant Physiologists ond reprinteri r«ith permission.)
<strong>Rice</strong> Physiology 145<br />
•A chain<br />
-6 chain<br />
nonreducing<br />
end<br />
reducing<br />
end<br />
B ____ nonreducing<br />
fSX, anrt<br />
-10 nm crystalline<br />
lamella<br />
Ap side<br />
chain<br />
■ clusters<br />
reducing<br />
end<br />
crystalline !-►<br />
lamellae<br />
-^-lamotphous<br />
-♦ ^lamellae<br />
~100 nm<br />
Figure 2.2.8. Diagrammatic representation of the first three levels of amylopectin structure. (From<br />
Myers et al., 2000, copyrighted by the American Society of Plant Physioiogists ond reprinted with<br />
permission.)<br />
hormones released are in low concentrations (picom olar concentrations). Both the<br />
synthesis <strong>and</strong> degradation o f the hormones is closely regulated. The horm ones are<br />
part of com plex webs o f plant signaling networks. The plant horm ones signal to a<br />
plant to take certain actions in response to other signals. Many, probably all, o f the<br />
hormones lead to <strong>and</strong> proceed from signals to encode proteins. Root systems o f plants<br />
are a part o f the central processing center for plants. At least five o f the nine classes o f<br />
plant hormones are produced in the roots (Itai <strong>and</strong> Birnbaum , 1995). Critical underst<strong>and</strong>ing<br />
o f the role o f horm ones was gained by pioneering work in plant adaptation<br />
<strong>and</strong> survival. Various stimuli elicit signals that alter genetic expression o f metabolism<br />
in plants. In plants, various stimuli cause genes to send mRNA to the ribosomes,<br />
which, in turn, transcribe proteins. The hormones are part o f an interrelated crosstalk<br />
o f plant signals.<br />
M icroorganisms also produce some o f the horm ones, <strong>and</strong> consequently, the bacteria<br />
<strong>and</strong> fungi are capable of controlling the plant they inhabit. In fact, fungi often<br />
produce m uch larger quantities o f the horm ones than do higher plants. Gibberellic<br />
acid was discovered through efforts to underst<strong>and</strong> “foolish seedling” disease in rice,
146 The <strong>Rice</strong> Plant<br />
which was caused by the fungus Gibberellafujikuroi The disease was characterized by,<br />
among other things, excessive shoot elongation (Crozier et al., 2000).<br />
f\<br />
MINERAL NUTRITION OF RICE, PLANT ABNORMALITIES, AND<br />
ASSOCIATED STRESSES<br />
V f'<br />
A host o f biochemical <strong>and</strong> physical processes are necessary for survival <strong>and</strong> re<strong>production</strong>.<br />
The rice plant must acquire the mineral nutrients needed for growth <strong>and</strong><br />
development. The plant must develop the structural com ponents, primarily cell walls,<br />
to occupy both aboveground <strong>and</strong> belowground space. Nitrogen nutrition affects both<br />
growth <strong>and</strong> development o f rice plants. Nitrogen is talcen up rapidly by seedlings<br />
<strong>and</strong> converted into leaf protein. The leaves successively exp<strong>and</strong>, attain a maximum<br />
photosynthetic rate near the completion o f expansion, <strong>and</strong> gradually senesce. Much<br />
of this early nitrogen apparently remains in the plant, moving from older leaves to<br />
younger leaves until after the grain is filled. During its lifetime a leaf must either<br />
repair or disassemble damaged proteins. As the leaves become less viable due to age,<br />
shading, <strong>and</strong> irreversible oxidative damage, the balance o f protein activity is tilted<br />
toward degradation, not repair.<br />
Various constituent amino acids in leaves o f rice are transformed by proteinase<br />
' activities into primarily glutamate, glutamine, <strong>and</strong> serine. These are readily translocated<br />
to sink tissue, such as developing leaf tissue.<br />
Consequently, we expect the nitrogen in early season growth to be redistributed<br />
to younger leaves throughout the vegetative period. Leaf area is usually maximum<br />
just before growth stage RO (Murata <strong>and</strong> Matsushima, 1975). Initiation o f the young<br />
panicle (growth stage RO) at arpund the time o f collar form ation of leaf 4 below the<br />
flag leaf (growth stage Vp_/t) for m ost U.S. rice cultivars <strong>and</strong> differentiation o f tire<br />
panicle (growth stage R l)a t the completed leaf blade elongation (collar formation) for<br />
leaf 3 below the flag leaf (Vp.3) leads to a large dem<strong>and</strong> for translocated nitrogen. This<br />
dem<strong>and</strong> arises fi'om the differentiating panicle’s requirements for nitrogen (Yoshida,<br />
1981). Consequently, rice leaves frequently appear to be somewhat deficient in nitrogen<br />
during this period. Similarly, nitrogen fertilization during panicle differentiation<br />
is a st<strong>and</strong>ard practice tlrat usually increases grain yield. Yield com ponents responsible<br />
for the yield increase when nitrogen fertilizer is applied at this tim e are increased panicle<br />
branching <strong>and</strong> an increase in grains per panicle. Another relevant process is also<br />
occurring. <strong>Rice</strong> leaves may fail to becom e visibly green after this yellowing occurs, even<br />
witli nitrogen fertilization. Although it is universally accepted that the developing<br />
branching panicles are greater sinks for nitrogen than are the leaves, floret numbers<br />
per panicle <strong>and</strong> grain yield are correlated with leaf area (Yoshida, 1981; Counce, 1992).<br />
Consequently, midseason (i.e., near panicle differentiation, growth stage R l) nitrogen<br />
fertilization o f rice contributes to maintaining optim um leaf area to maximize yield,<br />
thereby supplying adequate carbohydrates to the differentiating panicles.<br />
The nutritional phenomena that com m only occur in rice affect the productivity<br />
o f the crop. Some nutritional disorders are related partially to intensive cropping,<br />
saline water, depletion or unavailability o f various nutrients, <strong>and</strong> elevated pH. Reports<br />
o f the nutritional disorders occur in different languages with different st<strong>and</strong>ards<br />
o f comparison, which makes unified underst<strong>and</strong>ing difficult. However, several<br />
distinctive nutritional conditions com monly occur in rice. All o f these conditions
<strong>Rice</strong> Physiology 147<br />
are somewhat unique to paddy rice <strong>and</strong> all can affect grain yield substantially. These<br />
conditions include straighthead, akagare, zinc deficiency, <strong>and</strong> selective silica uptake<br />
(<strong>and</strong> silica deficiency).<br />
E. Takaliashi (1995) noted the selective uptake o f silicic acid by rice. Silica is<br />
laid down in cell walls <strong>and</strong> in epidermal ceUs o f rice <strong>and</strong> other grasses as a crystalline<br />
structure. Silica fertilization increases rice photosynthesis, reduces water use,<br />
increases leaf erectness, <strong>and</strong> reduces excessive <strong>and</strong> therefore harmful uptake o f some<br />
nutrients (E. Takahashi, 1995). The failure to include silica as an essential plant nutrient<br />
is probably a com bination o f a flawed definition o f essentiality <strong>and</strong> difficulty in<br />
excluding silica from nutrient solutions (Epstein, 1999).<br />
Straighthead is a general condition caused by various factors. W hen a rice panicle<br />
develops normally, the top o f the panicle is bent over at m aturity <strong>and</strong> the top o f the<br />
panicle is yellow or brown. In straighthead conditions, the panicle is erect (or partially<br />
erect) <strong>and</strong> the panicle is often green long after the norm al time for grain development<br />
from R4 to R9. Two types o f straighthead have been found: Hideri aodachi <strong>and</strong> arsenic<br />
induced straighthead. H. aodachi is drought injury straighthead caused by draining<br />
at certain stages o f growth.<br />
Straighthead can be either dramatic or barely noticeable. In U.S. rice-growing<br />
areas, straightliead can be induced by arsenical pesticides in fairly high levels in the soil<br />
or by relatively low concentration in the plants at the time o f male gamete <strong>production</strong>,<br />
during growth stage R3. At this stage o f growth, application o f arsenical materials kills<br />
the male gametes. Eemale gamete <strong>production</strong> is also reduced but to a lesser degree.<br />
In distinction to drought-injury straighthead, arsenic-related straighthead can be<br />
prevented by draining <strong>and</strong> drying rice soils before growth stage RO.<br />
Akagare disease is caused by iron toxicity in flooded rice due to the plant s in <br />
ability to exclude iron from inside the plant. Consequently, ferrous iron accumulates<br />
in the plant. In m ost mineral soils, the roots of flooded rice are red. This is because<br />
the norm al rice plant chelates iron on the root surface which is coated with a layer o f<br />
oxygen. The red color is due to the iron layer that coats flooded rice roots. The akagare<br />
condition also occurs in acidic soils in Japan.<br />
Alcagare (type I) (Tadano, 1995) is similar to certain symptoms, Slaton et al.<br />
(1996), observed on saline or alkaline soils in Arkansas, although there are differences<br />
in the conditions leading to these symptoms. The similarities are leaf bronzing, high<br />
ferrous iron content in tissue, <strong>and</strong> low phosphorus content. The conditions leading<br />
to the symptoms are, however, quite different: acid, hum ic soils in Japan, <strong>and</strong> alkaline<br />
<strong>and</strong> saline soils in Arkansas. Akagare is also caused by iodine toxicity <strong>and</strong> zinc<br />
deficiency.<br />
Akagare has many causes in com m on with a similar problem. Acid sulfate soil,<br />
zinc deficiency, iodine toxicity, <strong>and</strong> saline soil conditions lead to rice plants that cannot<br />
exclude harm ful ions <strong>and</strong> take up needed nutrients selectively. <strong>Rice</strong> roots are incapable<br />
o f functioning effectively to carry out critical iron exclusion <strong>and</strong> nutrient uptake<br />
activities. Depending on the particular situation, an ion may be either deleterious or<br />
deficient. The key similarity is that the integrity o f the root system is compromised<br />
<strong>and</strong> the roots cannot function properly. In this situation, mass flow o f ions into tlie<br />
roots occurs followed by severe plant osmotic stress, leading to different m etabolic<br />
conditions in the shoots, predominated by bronzing. The exception appears to be<br />
zinc-deficient akagare, in which the m idrib become chlorotic but the leaves do not<br />
bronze (Tanaka, 1995).
Zinc is a cofactor in several enzymes that perform key oxidation-reduction reactions,<br />
Among these enzymes are alcohol dehydrogenase <strong>and</strong> copper-zinc superoxide<br />
dismutase. After flooding o f rice <strong>and</strong> prior to aerenchyma form ation, the roots are<br />
in low-oxygen conditions in which ethanol accumulates due to anaerobic respiration.<br />
W ithout detoxification, ethanol accumulation becomes toxic. Kram er <strong>and</strong> Boyer<br />
(1995) note, however, that ethanol probably does not kill flooded plants. Alcohol<br />
dehydrogenase must either increase in activity, or more o f the enzymes must be<br />
transcribed (coded from DNA)in order for the plant to function optimally. Also, soon<br />
after flooding, the water <strong>and</strong> air temperature are low, due to cold water from wells <strong>and</strong><br />
often, low air temperatures. In this situation, photosynthetic rates are reduced <strong>and</strong> the<br />
radiation normally utilized in photosynthesis is, in fact, directed to reducing oxygen<br />
(O2) (Fridovich, 1991) to superoxides (O 2') (Ham ilton, 1991). Superoxide radicals<br />
(0 2‘) degrade membranes <strong>and</strong> lead rapidly to degeneration o f chloroplast membranes<br />
<strong>and</strong> other membranes unless they are detoxified (Elstner, 1991). Radical oxygen is<br />
enzymatically converted to hydrogen peroxide (H 2O 2) by superoxide dismutase. Hydrogen<br />
peroxide is also toxic to plants <strong>and</strong> must be detoxified by ascorbate peroxidase<br />
<strong>and</strong> subsequent action by glutathione reductase in the chloroplast (Figure 2.2.9). As<br />
the temperature o f water in the rice field <strong>and</strong> the air increase, the problem o f radical<br />
oxygen-related stress decreases.<br />
The first line of defense in plants against radiative stress is probably the carotenoids,<br />
which are located by the chorophyll molecules. The carotenoids can either<br />
absorb light energy or detoxify radical oxygen. Oxidation <strong>and</strong> reduction o f xantho-<br />
phyll cycle carotenoids is presented in Figure 2.2.10. Probably, radical oxygen-related<br />
stress is present at all tim es'during the rice plant’s development in all cultural <strong>and</strong><br />
geographic situations. The shortage o f zinc during critical early stages o f development<br />
may lead to chlorosis o f leaf tissue. Zinc-deficient plants sometimes float in the water,<br />
indicating that the zinc deficiency leads to root deterioration. The severity o f the<br />
condition depends on temperature (lower temperatures being worse, especially below<br />
16°C), the zinc-supplying capacity o f the soil, the zinc-extracting capacity o f the plant,<br />
<strong>and</strong> the metabolic makeup o f the plant. Also, larger plants have larger nodal roots,<br />
GSSG<br />
NADPH<br />
Ascorbate<br />
Ascorbate<br />
Peroxidase<br />
Monodehydro-<br />
Ascorbate<br />
Reductase<br />
Dehydro-<br />
Ascorbate<br />
Reductase<br />
Gluthatione<br />
Reductase<br />
MDHA<br />
A NAD(P)H<br />
DHA 2GSH NADP<br />
Figure 2.2.9. Cycle of oscorbote-dependent H2O2scovenging in chloroplasts. (From Foyer<br />
<strong>and</strong> Lel<strong>and</strong>ois, 1993, copyrighted by the American Society of Plant Physiologists <strong>and</strong> reprinted<br />
with permission.)
Ríce Physiology 149<br />
'<br />
HO<br />
AJ^O<br />
Vioiaxanthin<br />
n .<br />
OH<br />
ZE<br />
(<br />
/ ho Antheraxanthin<br />
VDe [<br />
Zeaxanthin<br />
Figure 2.2.10. Reactiofjs of ihexonfhophyll cycle. (From Adams <strong>and</strong><br />
Demming-Adoms, 1993, copyrighted by the Americon Society of Plant<br />
which extract nutrients <strong>and</strong> withst<strong>and</strong> stressful external conditions in the root zone<br />
Physiologists <strong>and</strong> reprinted with permission.)<br />
better than do smaller roots.<br />
CONCLUSION<br />
Scientists worldwide have specialized to produce a large body o f inform ation on rice<br />
plant physiology. Underst<strong>and</strong>ing physiology can lead to m ore productive rice cultivars<br />
having higher quality <strong>and</strong> greater resistance to various biotic <strong>and</strong> abiotic stresses.<br />
The rice genome is currently bemg sequenced. The availability o f the DNA sequence<br />
coupled with powerful research techniques in proteonom ics <strong>and</strong> genomics<br />
should lead to even greater underst<strong>and</strong>ing o f rice plant biology in the future.<br />
REFERENCES<br />
Adams, W. W. <strong>and</strong> B. Denmig-Adams, 1993. Energy dissipation <strong>and</strong> photoprotection<br />
in leaves o f higher plants. In H. Y. Yamamoto <strong>and</strong> C. M. <strong>Smith</strong> (eds.) Photosynthetic<br />
responses to the environment. American Study o f Plant Physiologists,<br />
Rockville, MD, pp. 27-36,<br />
Alocilja, E. C., <strong>and</strong> J, T, Ritchie. 1991. A model for the phenology o f rice. In T. Hodges<br />
(ed.), Predicting Crop Phenology. CRC Press, Boca Raton, PL, pp, 181-189.<br />
Avigad, G.) <strong>and</strong> P. M . Dey. 1996. Carbohydrate metabolism: storage carbohydrates.<br />
In P. M. Dey <strong>and</strong> J. B. Harborne (eds.), Plant Biochemistry. Academic Press, New<br />
York, pp. 143-204.<br />
Baskin, T. J. 2000. The cytoskeleton. In B. B. Buchanan, W. Gruissem, <strong>and</strong> R. L, Jones<br />
(eds.), Biochemistry <strong>and</strong> Molecular Biology o f Plants. Am erican Society o f Plant<br />
Physiologists, R o c^ ille , M D, pp. 202-258.<br />
Bennetzin, J. L, 2000. Comparative sequence analysis o f plant nuclear genomes: m i-<br />
crolinearity <strong>and</strong> its many exceptions. Plant Cell 12:1021-1029.
150 The <strong>Rice</strong> Plant<br />
Chaudhary, T. N., <strong>and</strong> B. P. Ghildyal. 1969. Germination response o f rice seeds to<br />
constant <strong>and</strong> altering temperatures. A gron.}. 61:328-330.<br />
Cohn, N, A., <strong>and</strong> J, A. Hughes. 1981. Seed dormancy in red rice (O ryza sativa L ).<br />
I. Effect of temperature on dry after ripening. W eed S ei 29:402-404.<br />
Counce, P. A. 1992. Responses <strong>and</strong> ramifications o f rice canopy leaf stratification. Crop<br />
S ei 32:779-781.<br />
Counce, P. A., B. R. Wells, <strong>and</strong> R. J. Norman. 1994a. Simulated hail damage in rice.<br />
I. Susceptible growth stages. Agron. J. 86:1107-1113.<br />
Counce, P. A., B. R. Wells, R, J. Norman, <strong>and</strong> J, Leong. 1994b. Simulated haü damage<br />
in rice. II. Effects during four reproductive growth stages. Agron. J. 86:1 U S<br />
U IS .<br />
Counce, P. A., T. J. Siebenmorgen, A. Poag, G. E. Holloway, M. E Kocher, <strong>and</strong> R. Lu.<br />
1996. Panicle emergence o f tiller types <strong>and</strong> grain yield o f tiller order by direct-<br />
seeded rice cultivar. Field Crop Res. 47:235-242,<br />
Counce, P. A., T. C. Keisling, <strong>and</strong> A. J. Mitchell. 2000, A uniform objective <strong>and</strong> adaptive<br />
system for expressing rice development. Crop S ei 40:436-443.<br />
Crozier, A., Y. Kamiya, G. Bishop, <strong>and</strong> T. Yokota. 2000. Biosynthesis o f hormones<br />
<strong>and</strong> elicitor molecules. In B. B. Buchanan, W. Gruissem, <strong>and</strong> R. L. Jones (eds.),<br />
B ioehem istry <strong>and</strong> M olecular Biology o f Plants. American Society o f Plant Physiologists,<br />
Rockville, M D, pp. 850-929.<br />
Dangl, J. L., R. A. Dietrich <strong>and</strong> H. Thomas. 2000. Senescence <strong>and</strong> programmed cell<br />
death. In B. B. Buchanan, W. Gruissem <strong>and</strong> R. L. Jones (eds.), Biochem istry <strong>and</strong><br />
Molecular Biology o f Plants. American Society o f Plant Physiologists, Rockvile,<br />
M D ,pp. 1004-1100. .<br />
Dat, T. V., <strong>and</strong> M. L. Peterson. 1983a. Performance o f near- isogenic genotypes o f rice<br />
differing in growth duration. I. Yields <strong>and</strong> yield components. Crop S ei 23:239-<br />
242.<br />
Dat, T. V., <strong>and</strong> M. L. Peterson. 1983b. Performance o f near-isogenic genotypes o f rice<br />
differing in growth duration. II. Carbohydrate partitioning during grain filling.<br />
Crop S ei 23:243-246.<br />
Devos, K. M ., <strong>and</strong> M . D. Gale. 2000. Genome relationships: the grass model in current<br />
research. P lant Cell 12:637-646.<br />
Downey, D. A., <strong>and</strong>B, R. Wehs. 1975. Air Tem peratures in the S tarhonnetR ice Canopy<br />
an d T heir R elationship to N itrogen Timing, G rain Yield an d W ater Temperture.<br />
Univ. Ark. Agric. Exp. Stn, Bull. 796.<br />
Elstner, E. F. 1991. Mechanism of oxygen activation in different compartments of<br />
plant cells. In E. Pell <strong>and</strong> K. Steffen (eds.), Active O xygen/O xidative Stress <strong>and</strong><br />
P lant M etaholism . American Society o f Plant Physiologists, RoclcviUe, MD, pp.<br />
13-25.<br />
Epstein, E. 1999. Silicon. A nna. Rev. P lant P hysiol Plant M o l B io l 50:641-664.<br />
Evans, L. T. 1975. The physiological basis o f crop yield. In L. T. Evans (ed.), Crop<br />
Physiology. Cambridge University Press, Cambridge, pp, 327-355.<br />
Foyer, C. H. <strong>and</strong> M . Lel<strong>and</strong>ais. 1993. The role o f ascorbate in the regulation o f photosynthesis.<br />
In H. Y. Yamamoto <strong>and</strong> C. M. <strong>Smith</strong> (eds.) P hotosynthetic responses<br />
to the environm ent. American Society of Plant Physiologists, Rockville, MD, pp.<br />
88- 101.<br />
Freeling, M. 2001. Grasses as a single genetic system: reassessment 2001. P lant Physiol<br />
125:1191-1197.
<strong>Rice</strong> Physiology 151<br />
Fridovich, I. 1991. M olecular oxygen: friend or foe. In E. PeU <strong>and</strong> K. Steffen (eds.),<br />
Active O xygen/O xidative Stress an d P lant M etabolism . American Society o f Plant<br />
Physiologists, Rockville, M D, pp. 1-5.<br />
Hamaker, B. R„ T. J. Siebenmorgen, <strong>and</strong> R. H. Dilday, 1993. Aging o f rice in the first<br />
six months after harvest. Ark. Farm Res. 4 2 :8 -9 .<br />
Hamilton, G. A. 1991. Chemical <strong>and</strong> biochemical reactivity o f oxygen. In E. Pell <strong>and</strong><br />
K. Steffen (eds.), Active O xygen/O xidative Stress an d P lant M etabolism . American<br />
Society o f Plant Physiologists Rockville, MD, pp. 6-12.<br />
Hoshikawa, K. 1989. T he Growing <strong>Rice</strong> Plant. Nobunkyo, Tokyo.<br />
Huang, J.-W,, J.-T. Chen, W .-P Yu, L.-P. Shyur, A.-Y, Wanj, H.- Y.. Sung, P.-D Lee, <strong>and</strong><br />
J.-C, Su. 1996. Complete structures o f three rice sucrose synthase isogenes <strong>and</strong><br />
differential regulation o f their expressions. Biosci. Biotechnol. Biochem . 6 0 :2 3 3 -<br />
239.<br />
Ishii, R. 1995a. Cultivar differences. In T. Matsuo, K. Kumazawa, R. Ishii, K. Ishihara,<br />
<strong>and</strong> H. Hirata (eds.), Science o f the <strong>Rice</strong> Plant, Vol. 2, Physiology. Food <strong>and</strong> Agricultural<br />
Policy Research Center, Tokyo, pp. 566-572.<br />
Ishii, R. 1995b. Leaf senescence. In T. Matsuo, K. Kumazawa, R. Ishii, K. Ishihara, <strong>and</strong><br />
H. Hirata (eds.), Science o f the <strong>Rice</strong> Plant, Vol. 2 Physiology. Food <strong>and</strong> Agricultural<br />
Policy Research Center, Tokyo.<br />
Itai, C., <strong>and</strong> H. Birnbaum . 1995. Synthesis o f plant growth regulators by roots. In<br />
Y. Wausil, A. Eshel, <strong>and</strong> U. Kafkafi (eds.), P lant Roots: T he H idden H alf, 2nd ed.<br />
Marcel Dekker, New York, pp. 273-284.<br />
Jean, R. V. 1994. Phyllotaxis: A Systemic Study in P lant M orphogenesis. Cambridge<br />
University Press, Cambridge.<br />
Juliano, B. O., <strong>and</strong> D. R, Bechtel. 1985. The rice grain <strong>and</strong> its gross com position.<br />
In B. O, Juliano (ed.), <strong>Rice</strong> Chem istry an d Technology. American Association of<br />
Cereal Chemists, St. Paul, MN, pp. 17-57.<br />
Keeling, P. L., R. Banisadr, L. Barone, B. R Wasserman, <strong>and</strong> G. W. Singletary. 1994.<br />
Effect o f temperature on enzymes in the pathway o f starch biosynthesis in developing<br />
wheat <strong>and</strong> maize grain. A ust.}. P lant P hysiol 21:807-827.<br />
Kramer, P, J., <strong>and</strong> J. S. Boyer. 1995. y/ater R elations o f Plants an d Soils. Academic Press,<br />
San Diego, CA.<br />
Marschner, H. 1995. M ineralN utrition o f Plants. 2nd ed. Academic Press, San Diego, CA.<br />
Murata, Y., <strong>and</strong> S. Matsushima. 1975. <strong>Rice</strong>. In L. T. Evans (ed.), Crop Physiology,<br />
Cambridge University Press, Cambridge, pp. 73-99.<br />
Myers, A. M ., M. K, Morell, M. G. James, <strong>and</strong> S. G. Ball. 2000. Recent progress toward<br />
underst<strong>and</strong>ing biosynthesis o f the amylopectin crystal. P lant P hysiol 1 2 2 :9 8 9 -<br />
997.<br />
Ponnamperuma, F. N. 1972. The chemistry o f submerged soils. Adv. Agron. 24:29-96.<br />
Raskin, L, <strong>and</strong> H. Kende. 1985. Mechanism o f aeration in rice. Science 228:327-329.<br />
Ryan, C., <strong>and</strong> G. Pearce. 2001. Polypeptide hormones. P lant P hysiol 125:65-68.<br />
Shannon, J. C., F.-M. Pien, H. Cao, <strong>and</strong>K .-C . Liu. 1998. B rittle-1, an adenylate translocator,<br />
facilitates transfer o f extraplastidial syntliesized ADP-glucose into amylo-<br />
plasts o f maize endosperms. P lant P hysiol 117:1235-1252.<br />
Sharma, P. K,, G. Pantuwan, K. T. Ingram, <strong>and</strong> S. K. De Datta. 1994. Rainfed lowl<strong>and</strong><br />
rice roots: soil <strong>and</strong> hydrological effects. In G. J. D. Kirk (ed.), <strong>Rice</strong> Roots: N utrient<br />
an d W ater Use. International <strong>Rice</strong> Research Institute, Manila, The Philippines,<br />
pp. 55-66.
152 The <strong>Rice</strong> Pinnt<br />
Slaton, N. A., B. R. Wells, D. M. Miller, C. E. W ilson, <strong>and</strong> R. J. Norman. 1996. Definition<br />
o f rice <strong>production</strong> problems related to soil alkalinity <strong>and</strong> salinity. In R. J.<br />
Norman <strong>and</strong> B. R. Wells (eds.), A rkansas <strong>Rice</strong> Research Studies, .1995. Ark. Agrie,<br />
Exp. Stn. <strong>Rice</strong> Res. Ser. 453, pp. 178-185.<br />
<strong>Smith</strong>, A. M., K. Denyer, <strong>and</strong> C. Martin. 1997. The synthesis o f the starch granule,<br />
Annu. Rev. P lant P hysiol P lant M o l B io l 46:67-87.<br />
Stansell, ]. W. 1975. Effective utilization o f sunlight. In Six D ecades o f <strong>Rice</strong> Research,<br />
Res. Monogr. 4. Texas A&M University, College Station, TX , pp. 4 3 -50.<br />
Tadano, T. 1995. Akagare disease. In T. Matsuo, K. Kumazawa, R. Ishii, K. Ishihara,<br />
<strong>and</strong> H. Hirata (eds.), Science o f the <strong>Rice</strong> Plant, Vol. 2, Physiology. Food <strong>and</strong> Agricultural<br />
Policy Research Center, Tokyo, pp. 939-953.<br />
Taiz, L., <strong>and</strong> V. Zeiger. 1998. P lant Physiology. 2nd ed. Sinauer Associates, Sunderl<strong>and</strong>,<br />
MA.<br />
Takahashi, E. 1995. Uptake mode <strong>and</strong> physiological functions of silica. In T. Matsuo,<br />
K. Kumazawa, R. Ishii, K. Ishihara, <strong>and</strong> H. Hirata (eds.), Science o f the <strong>Rice</strong> Plant,<br />
Vol. 2, Physiology. Food <strong>and</strong> Agricultural Policy Research Center, Tokyo, pp. 420-<br />
433.<br />
Takahashi, N. 1995a. Longevity o f seeds. In T. Matsuo, K. Kumazawa, R. Ishii, K. Ishihara,<br />
<strong>and</strong> H. Hirata (eds.), Science o f the <strong>Rice</strong> Plant, Vol. 2, Physiology. Food <strong>and</strong><br />
Agricultural Policy Research Center, Tokyo, pp, 57-61.<br />
Takahashi, N. 1995b. Physiology o f dormancy. In T. Matsuo, K. Kumazawa, R. Ishii,<br />
K. Ishihara, <strong>and</strong> H. Hirata (eds.)> Science o f the <strong>Rice</strong> Plant, Vol. 2, Physiology. Food<br />
<strong>and</strong> Agricultural Policy Research Center, Tokyo, pp. 4 5 -5 7 .<br />
Takahashi, N. 1995c. Physiology o f seed germination. In T. Matsuo, K. Kumazawa,<br />
R. Ishii, K. Ishihara, <strong>and</strong> H. Hirata (eds.), Science o f the <strong>Rice</strong> Plant, Vol. 2, Physiology.<br />
Food <strong>and</strong> Agricultural Policy Research Center, Tokyo, pp. 35-45.<br />
Tanalca, A. 1995. Alcagare caused by zinc deficiency. In T. Matsuo, K. Kumazawa,<br />
R. Ishii, K. Ishihara, <strong>and</strong> H. Hirata (eds.). Science o f the <strong>Rice</strong> Plant, Vol. 2, Physiology.<br />
Food <strong>and</strong> Agricultural Policy Research Center, Tolcyo, pp. 944-948.<br />
Taylor, C. 1998. Synthesizing starch: roles for rugosus5 <strong>and</strong> duUl. P lant Cell 10:311-<br />
314.<br />
Turner, F. X , <strong>and</strong> M. F. Jund. 1993, <strong>Rice</strong> ratoon crop yield linked to main crop stem<br />
carbohydrates. Crop S ei 33:150-153.<br />
Vaughan, D. A., H. Watanabe, H. Hille Ris Lambers, M. O. Zain, <strong>and</strong> N. Toniooka.<br />
1999. Weedy rice complexes in direct seeding rice cultures. Proceedings o f the<br />
International Sym posium on W orld Food Security, pp. 227-280.<br />
Yoshida, S. 1972. Physiological aspects o f rice grain yield. Annu. Rev. P lant Physiol<br />
12:89-97.<br />
Yoshida, S. 1981. Fundam entals o f <strong>Rice</strong> Crop Science. International <strong>Rice</strong> Research Institute,<br />
Manila, The Phillipines.<br />
Yoshida, S., <strong>and</strong> T. Hara. 1977, Influence o f air temperature <strong>and</strong> light on grain filling<br />
of an indica <strong>and</strong> a japónica rice { Oryza sativa L.) in a controlled environment.<br />
Soil S ei P lant Nutr. 23:93-107.
Chopter<br />
2.3<br />
Genetics, Cytogenetics, Mutation,<br />
<strong>and</strong> Beyond<br />
Georgia C. Eizenga <strong>and</strong> J. Neil Rutger<br />
U S D A -A R S -S P A<br />
Dale Bumpers National <strong>Rice</strong> Research Center<br />
Stuttgart Arkansas<br />
GENETICS<br />
Chromosome Number<br />
Genomes<br />
Karyotype<br />
Linkage Groups <strong>and</strong> Gene Symbols<br />
CYTOGENETICS<br />
Trisomic Series<br />
Additional Methods of Chromosome Identification<br />
Introgression of Oryza Species DNA<br />
INDUCED MUTATION<br />
History<br />
Useful Mutants<br />
Breeding Tool Mutants<br />
Knockout Mutants<br />
HYBRID RICE<br />
Methods of Seed Production<br />
Apomixis<br />
REFERENCES<br />
<strong>Rice</strong>: Origin, History, Technology, <strong>and</strong> Production, edited by C. Wayne <strong>Smith</strong><br />
ISBN 0-471-34516-4 © <strong>2003</strong> John Wiley & Sons, Inc.
154 The <strong>Rice</strong> Plant<br />
GENETICS<br />
Chromosome Number<br />
Cultivated rice (Oryza sativa L.) is a diploid species having 24 chromosomes, with<br />
a basic num ber o f 12. Kuwada (1910) was the first to report this (2n = 2x — 24),<br />
after studying rice mitosis, microsporogenesis, <strong>and</strong> megasporogenesis. This was subsequently<br />
confirmed by other workers. Besides O. sativa, 23 additional species have<br />
been identified in the Oryza genus to date. M ost o f these species are diploid, but a few<br />
are tetraploid.<br />
Genomes<br />
The O. sativa chromosomes have been designated as the A-genome. In West Africa,<br />
O. glaherrima is an endemic cultivated rice. This species also is diploid, crosses easily<br />
with O. sativa, <strong>and</strong> its genome designation is A^. The other 22 Oryza species that have<br />
been identified have genome designations o f either AA, BB, CC, BBCC, CCDD, EE, FF,<br />
GG, HHJJ, or HHKK (Table 2.3.1). These species are described further in Chapter 1.2.<br />
Karyotype<br />
ii<br />
The agreed num bering system for cultivated rice is from 1 to 12, with chi'omosome<br />
1 being the longest <strong>and</strong> chrom osom e 12 being the shortest. In som atic cells, chromosomes<br />
that can be identified by their distinguishing features are chromosomes 1,<br />
2, <strong>and</strong> 3, which can be identified by their length; chromosom es 4 <strong>and</strong> 7, which are<br />
' subtelocentric; chromosom e 8, which is dark staining; <strong>and</strong> chrom osom e 10, which has<br />
a satellite. The other chromosom es are not easily distinguished (Khush <strong>and</strong> Kinoshita,<br />
1991).<br />
Because it is difficult to differentiate rice chromosom es from som atic cells, the<br />
pachytene chrom osom e com plement was first studied by Shastry et al. (1960), who<br />
identified chromosomes ranging in length from 79.0 to 18,0 /xm. M uch later, Khush<br />
et al. (1984) described the pachytene chromosom es, <strong>and</strong> this becam e the agreed-upon<br />
numbering system, with chromosom e 1 being the longest. Chromosomes 2 <strong>and</strong> 3 are<br />
differentiated by their length, with chromosom e 2 being subm etacentric <strong>and</strong> chrom<br />
osom e 3 being m etacentric. Chromosome 4 has a very short, dark-staining short<br />
arm. Chromosomes 5 <strong>and</strong> 6 are submetacentric, but chrom osom e 6 has a shorter<br />
short arm than chromosom e 5. Chromosome 7 is submetacentric <strong>and</strong> chromosome<br />
8 m etacentric with many dark-staining centromeres. Chromosome 9 is subtelocentric<br />
with a dark-staining short arm containing the nucleolar organizing region. The<br />
short arm o f chromosom e 10 is longer than chromosom e 9; thus chromosom e 10 is<br />
submetacentric. Chromosomes 11 <strong>and</strong> 12 are submetacentric <strong>and</strong> the same size, but<br />
the short arm o f chrom osom e 11 is stained darkly. The ideogram o f the pachytene<br />
chromosomes is included in Figure 2.3.1. For a m ore detailed discussion o f the rice<br />
karyotype, see Khush <strong>and</strong> Kinoshita (1991), Khush <strong>and</strong> Singh (1991), <strong>and</strong> Khush et al.<br />
(1996).
Genetics, CylogeneticS; Mutation, <strong>and</strong> Beyond 155<br />
TABLE 2.3.1. Chromosome Number, Genomic Composition, <strong>and</strong> Potential Useful Traits of<br />
Oryza Species“<br />
Species 2ji G enom e Useful or Potentially Useful Traits'^<br />
0. sativa complex<br />
O. sativa 24 AA Gültigen<br />
0, nivara 24 AA Resistance to grassy stunt virus, blast, drought<br />
avoidance<br />
0. rufipogon 24 AA Elongation ability, resistance to BB, source of<br />
CMS<br />
0. breviligulata 24 AS AS Resistance to GLH, BB, drought avoidance<br />
0. glaberrima 24 ASA« Gültigen<br />
0. longistaminata 24 A®A® Resistance to BB, drought avoidance<br />
0. meridionalis 24 A'” A“ Elongation ability, drought avoidance<br />
O, glumaepatula 24 ASP Asp El ongation ability, source of CMS<br />
0. officinalis complex<br />
0. punctata 24 BB Resistance to BPPI, zigzag leafliopper<br />
0. minuta 48 BBCC Resistance to sheath blight, BB, BPH, GLH<br />
0. officinalis 24 c c Resistance to thrips, BPH, GLH, WBPH<br />
O. rhizomatis 24 c c Drought avoidance, rhizomatous ‘<br />
0. eichingeri 24 c c Resistance to yellow mottle virus, BPH, WBPH,<br />
GLH<br />
O. latifolia 48 CCDD Resistance to BPH, WBPH, GLH<br />
O. alta 48 CCDD Resistance to striped stemborer, high biomass<br />
<strong>production</strong><br />
O. gr<strong>and</strong>iglutnis 48 CCDD High biomass <strong>production</strong><br />
0. australiensis 24 EE Drought avoidance, resistance to BPH<br />
0. hrachyantha 24 PF Resistance to yellow stemborer, leaf-folder,<br />
whorl maggot, tolerance to laterite soil<br />
0. meyeriana complex<br />
O. granulata 24 GG Shade tolerance, adaptation to aerobic soil<br />
0. meyeriana 24 GG Shade tolerance, adaptation to aerobic soil<br />
0. ridleyi complex<br />
0. longiglumis 48 HHJJ Resistance to blast, BB<br />
0. ridleyi 48 HHJJ Resistance to stemborer, whorl maggot, blast, BB<br />
Unknown genome<br />
0, schlerchteri 48 Unknown Stoloniferous<br />
Source: Adapted from Jena <strong>and</strong> Khush (2000).<br />
"Additional information can be found in Chapter 1.2.<br />
''BB, bacterial blight; BPHj brown pknthopper; CMS, cytoplasmic male sterility; GLH, green leafliopper;<br />
WBPH, white-backed planthopper.<br />
Linkage Groups <strong>and</strong> Gene Symbols<br />
The first reported linkage in rice was between black hull <strong>and</strong> colored internode (Parnell<br />
et al., 1917), soon after the chromosome number o f rice had been determined.<br />
Researchers continued to discover markers <strong>and</strong> to determine linkages between the<br />
markers. Jodon (1956) proposed seven linlcage groups, <strong>and</strong>Nagao <strong>and</strong> Takahasi (1963)<br />
proposed 12 linkage groups, but additional studies reduced the number o f linkage
156 The <strong>Rice</strong> Plant<br />
ReW72<br />
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17.0<br />
4.8<br />
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18<br />
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8.6<br />
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20<br />
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9.8<br />
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62<br />
at<br />
6-30<br />
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119<br />
125<br />
132<br />
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■8f>3<br />
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149<br />
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141<br />
146<br />
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jcSlol<br />
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RG536<br />
RG3S0<br />
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9.0<br />
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167<br />
-¡»f-i<br />
RQ520<br />
176<br />
189<br />
■im<br />
201<br />
■d-29<br />
2-12 (S)<br />
Figure 2.3.1. Reiotionships between {from left to right) the pachytene idiograin of rice, the molecular linkage itKip,<br />
nfid the classical mop. Positions of the kinetochores are indicated by O's on the Idiograin, dark areas on the molecular<br />
linkage map, <strong>and</strong> C on the classical map. Relationships between the molecular <strong>and</strong> morophologlcal morkers, where<br />
known, are indicated by dashed lines. (From Khush et ol,, 1996; courtesy of the International <strong>Rice</strong> Research Institute.)
158 The <strong>Rice</strong> Plant<br />
ní-2<br />
10,2<br />
W0Xy ^s<br />
ff¿3 1 6<br />
14,2<br />
R24B0<br />
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s tl<br />
6 6 - ' ¡ r ^Éfí-2<br />
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» 2 7 6 8 \<br />
» a 4 0<br />
101 -<br />
14 ,3<br />
9 .3<br />
» 0 6 5 3<br />
i<br />
«ui (L)<br />
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9 .5<br />
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C 0 O 2 1 3<br />
1 2 4 ÜP-I<br />
sp(-4 (3)<br />
groups to nine. Finally, Isono et al. (1978) established a linkage group represented by<br />
su (now 5ug), sugary endosperm on chromosome 8, which lead to the establishment<br />
o f twelve linkage groups for the first time. Through the efforts o f many researchers,<br />
these linkage maps have been exp<strong>and</strong>ed further.<br />
Another problem that developed because there was no system for assigning gene<br />
symbols was that different symbols were assigned to the same genes. To summarize the<br />
genetic markers that had been identified <strong>and</strong> create a system for assigning gene symbols,<br />
the Sixth Meeting o f the FAO International <strong>Rice</strong> Commission Worldng Party on<br />
<strong>Rice</strong> Breeding in 1955 established an international committee cliaired by N. E. Jodon;.<br />
of the United States. The committee submitted its report in 1959 <strong>and</strong> it was approved<br />
by the Tenth International Genetics Congress. This report was published under the<br />
title <strong>Rice</strong> Gene Symbolization <strong>and</strong> Linkage Groups (USDA, 1963). The rules for gene
Genetics, Cytogenetics, Muiation, <strong>and</strong> Beyond 159<br />
R Q 128<br />
«•1<br />
7<br />
8<br />
I------1<br />
' 1^81<br />
R
Genetics, Cytogenetics, Mutation, <strong>and</strong> Beyond 161<br />
■<br />
11<br />
0 -S3<br />
Πa<br />
osp-2<br />
\^9<br />
sfrl<br />
P^a<br />
sp<br />
tf28<br />
nomenclature <strong>and</strong> gene symbols were reviewed <strong>and</strong> accepted during the <strong>Rice</strong> Genetics<br />
<strong>and</strong> Cytogenetics (Anonymous, 1964) symposium held at the International <strong>Rice</strong><br />
Research Institute (IRRI) in the Philippines. Unfortunately, no mechanism was established<br />
for monitoring the gene symbols, so the Japanese scientists organized a com <br />
mittee in 1979 to promote cooperation <strong>and</strong> adoption o f uniform gene symbols for rice<br />
in Japan. Eventually, the <strong>Rice</strong> Genetics Newsletter (RGN) was published in 1984, <strong>and</strong><br />
it contained proposed rules for gene symbolization. The following year, at the First<br />
International <strong>Rice</strong> Genetics Symposium, the <strong>Rice</strong> Genetics Cooperative (RGC) was<br />
organized to promote international cooperation in rice genetics <strong>and</strong> publish the RGN.<br />
The RGC now coordinates <strong>and</strong> m onitors gene symbols with new symbols <strong>and</strong> revised<br />
linkage maps being published in the annual RGN (Khush <strong>and</strong> Kinoshita, 1991).<br />
■<br />
E U<br />
■B<br />
- Cfrp-7<br />
d-27<br />
Pt-k<br />
CYTOGENETICS<br />
Trisomie Series<br />
For use in mapping the individual genes to chromosom e, various researchers identified<br />
trisom ie rice plants, plants having 25 chromosomes {2n + 1 = 2x — 25). These<br />
plants have an additional complete chromosome or primary trisóme. This means<br />
that a plant trisomie for chromosome 1 has three copies o f chromosome 1 <strong>and</strong> two<br />
copies o f chromosomes 2 through 12. Triploid plants crossed as female with diploid<br />
plants were often the source o f trisomie plants. The first report o f primary trisomies<br />
was Yunoki <strong>and</strong> Masuyama (1945), who obtained at least six morphologically distinguishable<br />
trisomie plants. Later, there were additional reports o f primary trisomies<br />
being obtained from triploid plants (Khush <strong>and</strong> Singh, 1991). Complete series o f all<br />
12 primary trisom ie chromosom es have been reported in the background o f seven<br />
different rice cultivars, including CS-M 3, a California breeding line (Khan, 1974),<br />
Guangluai 4 (Zhang <strong>and</strong> Zhu, 1986), IR36 (Khush et al., 1984), Kehtza (C. Hu, 1968),<br />
Nipponbare (Iwata <strong>and</strong> Omura 1984), Sona (M isra et al., 1986), <strong>and</strong> Zhongxian 3037<br />
(Cheng et al., 2001).<br />
Three o f these rice cultivars: (1) IR36, an indica cidtivar developed by IR R I in<br />
the Philippines (Khush et al., 1984,1996; K. Singh et al., 1996, R. Singh <strong>and</strong> Khush,<br />
2000); (2) Nipponbare, a temperate japónica cultivar developed in Japan (Iwata <strong>and</strong><br />
Omura, 1984; Wang <strong>and</strong> Iwata, 1995); <strong>and</strong> (3) Zhongxian 3037, a Chinese indica<br />
cultivar (Cheng et al., 2001), have various secondary trisomie, telotrisom ic, <strong>and</strong>/or<br />
alien addition lines available. Plants identified as secondary trisomies have the additional<br />
chrom osom e as an isochrom osome, a chrom osom e with two identical arms.<br />
In telotrisomic plants, the additional chromosom e has only one arm, <strong>and</strong> in the alien<br />
addition lines, the additional chrom osom e is from an Oryza species other than O.<br />
sativa.<br />
The IR36 trisomie series was used to develop a classical linkage map (Figure<br />
2.3.1), which located 43 marker genes to the chromosom e arm (K. Singh et al., 1996;<br />
Khush et a l, 1996). Further efforts were carried out on these lines to develop a<br />
molecular linkage map using restriction fragment length polymorphism (RFLP)<br />
markers which corresponded to the physical map <strong>and</strong> classical map. M ost o f the<br />
markers are from the Cornell University map (Causse et a l, 1994), but a few markers<br />
are from the <strong>Rice</strong> Genome Research Program (RGP) map (Kurata et a l, 1994). Since
162 The Rite Pioni<br />
this map was developed, many additional DNA markers, including amplified fragm<br />
ent length polymorphism (A F iP ), microsatellite, r<strong>and</strong>om amplified polymorphic<br />
DNA (RAPD), <strong>and</strong> sequence-tagged site (STS) markers, have been mapped to chromosome,<br />
<strong>and</strong> these are updated continually in the Gramene database {http://www.<br />
gramene.org). This database also includes isozyme markers, morphological markers,<br />
<strong>and</strong> links to other rice databases, including IRRI (Philippines), Japan, <strong>and</strong> Korea <strong>and</strong><br />
to other grass species databases.<br />
Additional Methods of Chromosome Identification<br />
During the past decade, the uneven staining pattern o f rice prometaphase root tip<br />
chromosomes has been used to identify the 12 individual rice chromosomes. This<br />
feature, called the condensation pattern by Fukui <strong>and</strong> Ohniido (2000), was used to<br />
develop the CHromosome Image Analysis System (CHIAS). The m ost recent version,<br />
CPIIÁS III, requires only a personal computer <strong>and</strong> has been used with several plant<br />
species, including other species with small chromosomes, such as rice. This program<br />
is available via the Internet {http://133.1.}31.81/Eudejas /chias3/chias3.htnil). At the<br />
same time, the in situ hybridization method was developed using ribosomal RNAs<br />
<strong>and</strong>/or DNAs. The first reports in rice were detection o f tire 45S rDNA probes (Fukui<br />
et al., 1987; Fukui, 1990; Islam-Faridi et al., 1990) <strong>and</strong> several RFLP probes (Gustafson<br />
<strong>and</strong> Dilié, 1992; Song <strong>and</strong> Gustafson, 1995). Initially, radioactive isotopes were used to<br />
label the probes, but this was soon replaced with biotin <strong>and</strong> fluorescent labels, which<br />
are still used. Use o f fluorescence in situ hybridization (FISH) has becom e a st<strong>and</strong>ard<br />
technique.<br />
W ith the development o f FISH for extended DNA fibers or fiber-FISH (Jiang<br />
et al., 1995; Fukui <strong>and</strong> Ohmido, 2000), a higher sensitivity was achieved. Using this<br />
technique, it is now possible to map clones 1 to 2 kb in length <strong>and</strong> map DNA clones<br />
as close together as 100 kb. Fiber-FISH is being used in the rice genome mapping<br />
program at Clemson to physically map the position o f the BAG clones when there are<br />
discrepancies in the mapping data obtained from sequencing (Jackson et al., 1999).<br />
Another variation o f FISH is genomic in situ hybridization (G ISH ), which is<br />
used to differentiate the Oryza species genomes (Table 2.3.1). In this technique, the<br />
chromosomes in a hybrid or hybrid derivative are distinguished by total genomic<br />
DNA from one parent, usually the non-A-genome parent being labeled with a fluo-<br />
rochrome <strong>and</strong> used as a probe together with excess amounts o f uniabeled DNA from<br />
cultivated rice (A-genome). Aggarwal et al. (1996) used GISH to distinguish the E-<br />
genome o f O. australiensis from the A-genome o f O. sativa. By means o f GISFI, Yasui<br />
et al. (1997) differentiated the single O. punctata-, B-genom e chrom osom e from the<br />
24 0 . sativOy A-genome chromosom es in m onosom ic alien addition lines. Multicolor<br />
GISH or M cGISH was used to identify the A, B, <strong>and</strong> C genomes in som atic hybrids<br />
between diploid O. sativGy with an A-genome <strong>and</strong> a tetrapioid O. punctata w ith both a<br />
B <strong>and</strong> C genome (Shishido et al., 1998). In this example, the A-genome chromosomes<br />
fluoresced red, C-genome chromosom es fluoresced green, <strong>and</strong> the counter stain was<br />
blue to identify the B-genom e chromsomes. In China, Yan et a l (1999) used GISH to<br />
distinguish O. eichingeri C-genome chromosomes in Fi, Fa, <strong>and</strong> backcross progenie?<br />
from crosses with O. sativa.
Genetits, Cytogenetics, Mutotion, <strong>and</strong> Beyond 163<br />
Introgression of Oiyza Species DNA<br />
Early research on the Orym species focused on determining the relationships between<br />
the genomes o f the various species <strong>and</strong> their ability to cross with each other. In the<br />
United States, efforts to utilize the Oryza sp, gerniplasm were first exploited by M.<br />
T. Henderson <strong>and</strong> his graduate student Birdie Yeh in Louisiana (Henderson, 1964).<br />
These studies report on analyses o f chrom osom e pairing in hybrids between seven<br />
different Oryza sp. <strong>and</strong> O. sativa to determine the genome relationships between these<br />
species. Later, Nowick (1986) studied the chromosom e pairing in hybrids between<br />
O. sativa, cultivated rice, <strong>and</strong> O. latifoUa. In addition, Nowick <strong>and</strong> Robinson (1988)<br />
collected <strong>and</strong> screened O. glumaepatula accessions native to the lower Amazon river<br />
basin, where there are high populations o f rice water weevil, for resistance to rice water<br />
weevil,<br />
Rutger et al. (1987) identified stem rot resistance in O. rufipogon <strong>and</strong> introduced<br />
the resistance into cultivated rice. Additional efforts to incorporate this resistance into<br />
a cultivated long grain resulted in tire germplasm release, PI 566666 {Tseng <strong>and</strong> Oster,<br />
1994). Macldll et al. (1998) identified an AELP fraginent(s) associated with the stem<br />
rot resistance. This marker will be used to follow the incorporation o f tlie stem rot<br />
resistance identified in O. rufipogon into California rice cultivars.<br />
W ith the form ation o f the Dale Bumpers National <strong>Rice</strong> Research Center in Stuttgart,<br />
Arkansas, Eizenga et al. (in press a,b) began screening the Oryza sp. for new<br />
sources o f resistance to sheath blight <strong>and</strong> blast, two m ajor rice fungal diseases in the<br />
United States. To date, the m ost promising sources o f resistance were identified in O.<br />
nivara <strong>and</strong> O. rufipogon accessions, <strong>and</strong> this DNA is being incorporated into rice cultivars<br />
<strong>and</strong>/or experimental lines adapted to the United States. Microsatellite markers<br />
are being used to follow the introgression o f Oryza sp. DNA into cultivated rice.<br />
Research utilizing tlie Oryza sp. gene pool at IRRI began witli tlie Symposium<br />
on <strong>Rice</strong> Genetics <strong>and</strong> Cytogenetics held at IRRI in 1963 (Anonymous, 1964), which<br />
served to bring researchers in the area together from around tlie world. Reports o f<br />
Oryza sp. revsearch focused on the genome relationships between die various Oryza<br />
species, including cultivated rice, O. sativa. Efforts to utilize the tertiary gene pool o f<br />
the Oryza sp, as a source o f pest resistance genes achieved its first success at IRRI<br />
with the identification o f one O. nivara accession (IRG C No. 101508), which had<br />
resistance to grassy stunt virus, fh e O, nivara resistance was incorporated into high-<br />
yielding cultivars that were released by IRRI, IR29, IR 30, IR32, IR34, <strong>and</strong> IR36 (Jena<br />
<strong>and</strong> Khush, 2000). Subsequently, genes for resistance to bacterial leaf blight, green<br />
leafhopper, zigzag leafhopper, white-backed planthopper, brown planthopper, blast,<br />
sheath blight, yellow stem borer, thrips, yellow mottled virus, leaf folder, <strong>and</strong> whorl<br />
maggot have been identified in the Oryza sp. Other agronomically useful traits identified<br />
in the Oryza sp. are cytoplasmic male sterility, shade tolerance, adaptation to<br />
aerobic soil, elongation ability, drought avoidance, <strong>and</strong> high biomass <strong>production</strong><br />
(Table 2.3.1).<br />
Efforts at WARDA have focused on exploiting O, glaberrima (Jones et al., 1997),<br />
which is cultivated in some parts o f Africa as an upl<strong>and</strong> rice, for high yield potential,<br />
rapid leaf canopy establishment, high nitrogen responsiveness, <strong>and</strong> improved com <br />
petitiveness with weeds. Research has focused on identifying these characteristics <strong>and</strong><br />
transferring the characters into O. sativa.
Oryza punctata has resistance to brown planthopper <strong>and</strong> zigzag leafhopper (Jena<br />
<strong>and</strong> Khush, 2000). Yasui <strong>and</strong> Iwata (1998a,b) developed alien addition lines carrying<br />
O. punctata chromosomes in the background o f the japónica rice cultivar Nipponbare.<br />
At tlie present time, these authors have not reported on the results o f their<br />
evaluation for useful genes from the progenies.<br />
Knowledge o f rice genetics was further exp<strong>and</strong>ed by induced mutations, which came<br />
into vogue after World War II, when the search began for peaceful uses of atomic<br />
energy. Early attempts, until about 1970, were characterized by heavy doses, induction<br />
o f curio mutants (defined as visible but o f little practical use, e.g., 15-cm -tall rice m u<br />
tants, etc.), <strong>and</strong>/or irreproducible results, Thus, by the middle 1960s, most researchers<br />
thought o f induced m utation as the “court o f last resort.” In the last three decades, the<br />
tide has turned, as researchers focused their efforts on <strong>production</strong> o f “useful” mutants,<br />
primarily in cultivars that needed correction for one or two undesirable agronomic<br />
traits, such as tall plant <strong>and</strong> late maturity.<br />
Induced mutation has been reported in rice more than in any other crop. Among<br />
the total o f 1847 accessions in the pAO/IAEA Mutant Varieties Database, 333 are rice<br />
mutants (Maluszynski, 1999). M ost (67.6% ) o f the rice mutants were “direct” releases<br />
o f mutants; others were progenies o f mutants that had been used in crossbreeding<br />
programs. Among the most widely used mutants are Reimei in Japan <strong>and</strong> Calrose 76<br />
in the United States (Maluszynsld, 1999). Calrose 76 was the first semidwarf cultivar<br />
in California <strong>and</strong> the second in the United States, being released on June 1, 1976<br />
(Rutger et al., 1977), just 17 days after the first semidwarf cultivar LA 110 was released<br />
(M cllrath et a l, 1979). The induced m utant semidwarfinggene {sdl) in Calrose 76 has<br />
been used as the ancestral semidwarfing source for development of nine improved<br />
semidwarf cultivars in the United States, nine in Australia, <strong>and</strong> two in Egypt. Similar<br />
uses have been made o f Reimei in Japan (Maluszynski, 1999), The total number of<br />
rice m utant cultivars listed in the IAEA database for the United States is 30, while<br />
35 are reported for Japan (Maluszynski, 1999). Maluszynski (1999) also describes<br />
the world’s m ost widely grown m utant rice cultivar, Yuan Fen Zao, which reached 1<br />
million hectares annually in China in the early 1990s. The mutant, which came from<br />
a complex induced mutation/crossing program, was both earlier <strong>and</strong> shorter than the<br />
<strong>origin</strong>al cultivars.<br />
The success o f the California program was due to the fact that Calrose, a cultivar<br />
used for 25 years, had many suitable characters but was prone to lodging at high<br />
fertility levels. Calrose also was a late-maturing, full-season cultivar that matured after<br />
fall rains began. Through gamma radiation, Rutger et al. (1976) produced semidwarf<br />
mutants, one of which was released directly as Calrose 76 (Rutger et a l, 1977). At a
Genotics, Cyrogenetics, Mutation, <strong>and</strong> Beyond 165<br />
mature height o f approximately 100 cm, Calrose 76 was about 25% shorter than its<br />
tall parent <strong>and</strong> thus resisted lodging at high fertility. Br<strong>and</strong>on et al. (1981) showed<br />
diat such semidwarfs produced 14% more grain <strong>and</strong> 13% less straw than the tall<br />
check cultivar CS-M 3, a derivative o f Calrose. Genetic studies by Rutger et al, (1976)<br />
demonstrated that the induced mutant had a semidwarfing gene at the sdl locus, the<br />
same locus that is present in the world’s Green Revolution cultivars o f the tropics.<br />
The importance o f the sdl locus as the desired source o f worldwide semidwarfism<br />
became apparent as evaluation o f nonallelic semidwarfs showed that none was as<br />
agronomically productive as sdl sources (Rutger, 1992b). Terming this phenom enon<br />
the sdl mystique, Rutger (1992) noted that use o f the sdl sources invariably results not<br />
only in greater lodging resistance but also in increased grain yield, mainly through an<br />
increase in harvest index. Nonallelic sources either had undesirable pleiotropic effects,<br />
such as smaller seed size in sd4 (Mackill <strong>and</strong> Rutger, 1979), or ju st equaled but did not<br />
exceed the grain yield o f the tall parent (Rutger, 1998).<br />
Another type o f useful mutant that can be induced readily in late-maturing cultivars<br />
is early-maturity mutants. Thus McKenzie et al. (1978) described a partially dom <br />
inant mutant for early maturity that was found in the same mutagenized population<br />
that produced Calrose 76. Through a stepwise series o f crosses, the early-maturity<br />
<strong>and</strong> semidwarf mutants were recombined with a gene for glabrous hull to produce<br />
the early-maturing, semidwarf, glabrous hull cultivar M -101 (Rutger et al., 1979),<br />
which also has figured prom inently in California cultivar development programs<br />
(Rutger, 1992).<br />
Rutger (1992b) noted that three types o f useful mutants can be found readily<br />
in mutagenized populations: semidwarfism, early maturity, <strong>and</strong> waxy endosperm. A<br />
particularly clever use o f induced m utation was the <strong>production</strong> by Carnahan et al.<br />
(1979) o f a waxy endosperm mutant, released as Calm ochi-201, in the otherwise best<br />
short-grain cultivar available in California at the tim e, S6. Since Calm ochi-201 was<br />
in the best short-grain background, it was competitive in yield to the parent cultivar.<br />
Prior to this work, it generally was accepted that low yield was a penalty that had to<br />
be accepted for growing waxy rice.<br />
Although researchers have “run out o f eyes” for selecting easily visible agronomic<br />
mutants, search continues for further applications o f the techniques. Thus Larson et<br />
al. (2000) have described the induction o f a low-phytic-acid m utant, Ipa 1, in the<br />
Arkansas cultivar Kaybonnet. This recessive mutant results in a 45% reduction in<br />
phytic acid. Phytic acid may be considered an antinutrient since it interferes with<br />
calcium <strong>and</strong> iron uptake.<br />
Oard <strong>and</strong> Rutger (1988) reported on efforts to induce mutants resistant to the<br />
imidiazolinone class o f herbicides. Although this work was inconclusive, Croughan<br />
(1999) subsequently was successful in producing a mutant resistant to this class o f<br />
herbicides.<br />
There have been many preliminary reports of inductions o f high protein, salinity<br />
tolerant, or disease resistance in rice, but m ost reports faded away apparently due to<br />
nonreproducibility o f results. Since m ost genes for disease resistance are dominant,<br />
<strong>and</strong> since m ost induced mutants are recessive, it is not surprising that success has<br />
eluded most researchers. However, a notable exception has been a carefully designed<br />
<strong>and</strong> conducted study by Bastos et al. (in press) on induction of blast resistance m u <br />
tants in the cultivar lAE 201.
166 The Rite Plant<br />
Breeding Tool Mutants<br />
Although they do not have direct agronomic application, Rutger <strong>and</strong> colleagues have<br />
described a number o f breeding tool mutants. These include gold hull <strong>and</strong> light<br />
green hull mutants for possible use in cultivar identification (Rutger et al., 1987),<br />
<strong>and</strong> elongated uppermost internode (eui) mutants for possible use in hybrid rice<br />
seed <strong>production</strong> (Rutger <strong>and</strong> Carnahan, 1981; Mackfil et al,, 1994). The hypothesis<br />
was that the eui mutant, which behaves as a recessive tall, would be useful for<br />
enhancing poUen distribution from a tall male parent onto the short female parent<br />
Thus the Fi has the desired semidwarf height o f the female parent. Although patented<br />
(Rutger <strong>and</strong> Carnahan, 1982), eui seed was freely distributed. A use totally unforeseen<br />
by the patent holders was incorporation o f the eui gene into female parents in<br />
crossing fields, in order to raise the panicle out of the boot <strong>and</strong> obviate the need<br />
for gibbereUin application to do this, as is com m only done in China (Zongtan <strong>and</strong><br />
Zuhua, 1989).<br />
Genetic male steriles have been induced by several researchers <strong>and</strong> proposed as<br />
tools for recurrent selection <strong>and</strong> population improvement schemes. They include<br />
recessive genetic male steriles (Fujimaki et al., 1977; Trees <strong>and</strong> Rutger, 1978; R, Singh<br />
<strong>and</strong> Ikehashi, 1979; Mese et al., 1984; J. Hu <strong>and</strong> Rutger, 1991, 1992). Recently, Zhu<br />
<strong>and</strong> Rutger (1999) reported a dominant genetic male sterile, which is more efficient<br />
for population improvement than recessive genetic male steriles, as male sterile plants<br />
appear every generation in the former versus every second generation in the latter.<br />
Rutger et al. (1986) used a recessive male sterile to produce 3728 crosses for an<br />
apomixis search (see the section “Apomixis”). The Japan <strong>and</strong> IRRI recessive male<br />
steriles, in japónica <strong>and</strong> indica backgrounds, respectively, apparently are being used in<br />
various population improvement schemes, but no documented results have appeared<br />
in the literature.<br />
Additional opportunities for application o f induced mutant in rice may include<br />
mutants for chemical composition. For example, altered fatty acid com position mutants<br />
should be inducible, since that has been done in the oil crops safflower, sunflower,<br />
<strong>and</strong> soybean, as well as in corn, Starch composition mutants have been reported<br />
widely in Japan (Yano et al., 1988), <strong>and</strong> undoubtedly can be induced in U.S. rice<br />
gcimplasm as well. Rutger (1999) proposed that “generic” chemical composition<br />
mutants could be induced for anything for which a m inim um o f 100 samples can<br />
be assayed per day. W hether such mutants will have value remains to be seen, but the<br />
situation could be thought o f analogous to the numerous corn endosperm mutants<br />
identified long ago, for which industrial uses have appeared in recent years (i.e., high-<br />
amylose cornstarch, etc.) (Neuffer et al., 1997).<br />
Knockout Mutants<br />
The newest use of induced m utation is in the field o f rice functional genomics. To<br />
determine the function o f a given gene, mutants are identified which are deficient for<br />
the particular gene function, These knockout mutants are used to determine the gene<br />
sequence that codes for the particular function being studied (Bouchez <strong>and</strong> Höfte,<br />
1998).
Genetics, Cytogenetics, Mutation, <strong>and</strong> Beyond 167<br />
HYBRID RICE<br />
Schemes for hybrid rice began appearing in Western literature in the 1960s (Stansel<br />
<strong>and</strong> Craigmiles, 1966; Erickson, 1969), <strong>and</strong> becam e apparent worldwide some 15<br />
years later (Lin <strong>and</strong> Yuan, 1980). Stansel <strong>and</strong> Craigmiles (1966) proposed a scheme for<br />
vegetative propagation (ratooning) o f hybrid plants, which would be labor intensive.<br />
Erickson (1969) sought <strong>and</strong> discovered sources o f cytoplasmic male sterility (cms), as<br />
did Shinjo (1969) <strong>and</strong> Athwal <strong>and</strong> Virmani (1972). Davis <strong>and</strong> Rutger (1976), using<br />
small plots, reported levels of heterosis in rice that they did not consider promising.<br />
Early hybrid rice work in California was soon shelved in favor o f <strong>production</strong> o f<br />
semidwarf cultivars, for which the return was immediate. The hybrid rice work at<br />
IRRI was also shelved when S. S. Virm ani transferred to a position at another center.<br />
The cms system reported by Shinjo had workable restorers, a feature that had been<br />
lacking in earlier cms systems <strong>and</strong> was used to a limited extent in the 1970s (Rutger<br />
<strong>and</strong> Shinjo, 1980).<br />
About 1977 the Western world was electrified by piecemeal reports o f hundreds<br />
o f thous<strong>and</strong>s o f hectares o f hybrid rice in China. The extent o f the China hybrid<br />
rice program was first documented by Lin <strong>and</strong> Yuan (1980), who reported successes<br />
with the WA male sterile cytoplasm <strong>and</strong> restorers. In 1983, the present junior author<br />
led a U.S. assessment team to China to see hybrid rice firsth<strong>and</strong>, by tlien grown on<br />
nearly 3 million hectares (unpublished). The assessment team concluded that there<br />
were two m ajor hurdles for successful <strong>production</strong> o f hybrid rice in the United States:<br />
(1) the high cost o f hybrid seed <strong>production</strong>, a problem that is h<strong>and</strong>led in China<br />
by labor-intensive practices, <strong>and</strong> (2) recovering grain quality satisfactory for U.S.<br />
rice markets. In China, emphasis was placed on increased quantity o f rice at the<br />
expense o f quality. In recent years, China, too, has turned to quality improvement<br />
in hybrid rice.<br />
At the present time, some 15 million hectares, h alf o f China^s rice area, is devoted<br />
to hybrid rice (Yuan <strong>and</strong> Fu, 1995). Outside China, Virm ani (1994) has developed<br />
many hybrid com binations for the tropics, the best o f which yielded 16% more than<br />
the best improved st<strong>and</strong>ard cultivar. Yield advantage o f the Chinese hybrid generally<br />
is about 20% (Yuan <strong>and</strong> Fu, 1995). Despite the success in China, <strong>and</strong> even though<br />
China has shared germplasm <strong>and</strong> <strong>technology</strong>, relatively little hybrid rice is produced<br />
outside China.<br />
Around 1980, a U.S. company, Ring-A-Around, purchased the Chinese hybrid<br />
rice materials <strong>and</strong> began an intensive effort to develop hybrids for the United States.<br />
After Ring-A-Round terminated its hybrid rice work, <strong>Rice</strong>Tec, Inc. continued this<br />
work for most o f the last decade. The latter company had several thous<strong>and</strong> hectares<br />
o f hybrid rice in com mercial <strong>production</strong> in the year 2000 (M ann, 2000).<br />
Methods of Seed Production<br />
Since private industry has assumed responsibility for hybrid rice <strong>production</strong>, there has<br />
been little public research in this area in the United States. Improved genetic m echanisms<br />
for hybrid seed <strong>production</strong> have been sought in U.S. public programs as well<br />
as in international programs in China <strong>and</strong> IRRI. By the time of the first International
2-line<br />
(pgms ortgms)<br />
1-line<br />
(apomixis)<br />
i Z ^<br />
F 1<br />
ms \<br />
j7Ms~<br />
^Tl<br />
Ms* is fertile in short days or low temperatures,<br />
<strong>and</strong> sterile in tong days or high temperatures.<br />
3-line system is cytoplasmic male sterility (cms) with steriles (A), maintainers (B), <strong>and</strong><br />
restorers (R)<br />
2-Iine system is photosensitive genetic male steriles (pgms) (Ms*) or thermosensitive<br />
genetic male steriles (tgms), <strong>and</strong> restorers (Ms)<br />
1-iine system is apomixis<br />
Figure 2.3.2. Elements of three-, two-, <strong>and</strong> one-line hybrid seed <strong>production</strong>. The three- <strong>and</strong> two-line<br />
systems ate in use in China. To date, the one-line (apomixis) system is theoretical.<br />
Hybrid <strong>Rice</strong> Symposium, held in Changsha, China, in 1986, the concept o f three-,<br />
two-, <strong>and</strong> one-line hybrids had evolved (Figure 2.3.2). Seed <strong>production</strong> under these<br />
decreasing line number systems would become progressively more efficient. At the<br />
present time the three-line system remains the workhorse method, although China is<br />
implementing suitable two-line systems (Yuan <strong>and</strong> Fu, 1995).<br />
The <strong>origin</strong>al two-line system in China traces its <strong>origin</strong> back to a sterile plant<br />
found by a farm er in 1973 in the cultivar Nongken 58 <strong>and</strong> hence dubbed the Nongken<br />
58S source o f photoperiod-sensitive genetic male sterility {pgms). Pursuit o f two-<br />
line hybrid rice research was in full swing <strong>and</strong> by the 1990s, Yuan <strong>and</strong> Fu (1995)<br />
had two-line systems in advanced testing. Testing involved not only pgms but also<br />
thermosensitive genetic male sterlity {tgms) systems. Virm ani (1994) at IRRI has<br />
identified tgms mutants that appear manageable by growing at different elevations.<br />
Currently, Yuan <strong>and</strong> colleagues (Yuan <strong>and</strong> Fu, 1995; NormÜe, 1999) have an<br />
intensive program to produce two-line intersubspecific hybrids (i.e., crosses between<br />
indicas <strong>and</strong> japónicas). This system is dependent on having wide-compatibility (WC)<br />
genes in the japónica parent, a phenom enon first described by Ikehashi <strong>and</strong> Araki<br />
(1984) in the 1980s.<br />
The China pgms work did not becom e Icnown in the United States until the middle<br />
1980s, about the time that Rutger (1988) independently found a pgms-like mutant<br />
in a Calrose 76-derived population. After finding the Calrose 76 source, Rutger<br />
<strong>and</strong> colleagues aggressively searched for additional pgms sources (Oard et ah, 1991;<br />
Rutger <strong>and</strong> Schaeffer, 1994; Rutger, 2001). Unfortunately, none o f Rutger’s putative<br />
sources has stood the test o f tim e (i.e., sources controlled only by photoperiod length<br />
were desired, but temperature <strong>and</strong>/or unknown factors seem to prevent reproducible<br />
management o f sterility).
Genetics, Cytogsnetics, Mutation, ond Beyond 169<br />
Apomixis<br />
Rutger (1985) initiated a search for apomixis in rice as a tool for producing true<br />
breeding Fi hybrid rice. These early studies (Rutger et al., 1986) involved (1) a search<br />
for aberrant segregation ratios suggestive o f apomixis with progenies tests o f 3728<br />
F] plants from a population improvement study utilizing a genetic male sterile as<br />
female <strong>and</strong> several hundred world collection lines as males; <strong>and</strong> (2) a search for excess<br />
<strong>and</strong>/or abnormal embryo sacs, the expected indication o f apomixis, in 547 entries o f<br />
the A-genome weedy species o f Oryza. Intergeneric hybridization attempts between<br />
rice <strong>and</strong> a known apomictic donor, Pennisetum setaceum> were added in 1987 <strong>and</strong><br />
1988. However, by 1992 it was evident that no conclusive evidence could be found o f<br />
rice apomixis in these studies (Rutger, 1992a).<br />
Numerous reports on searching for apomixis in rice have appeared in the 1990s,<br />
including Progress of Studies on <strong>Rice</strong> Apomixis in China (Guo, 1991) <strong>and</strong> Apomixis:<br />
Exploiting Hybrid Vigor in <strong>Rice</strong> (Khush, 1994). M ost reports have been on unusual<br />
reproductive phenom ena, including high-frequency twin seedlings. To date, no conclusive<br />
evidence o f useful levels o f apomixis has been reported.<br />
Future possibilities include transfer o f apomixis from known apomictic species<br />
such as Pennisetum <strong>and</strong> Tripsaccum^ by intergeneric hybridization <strong>and</strong>/or transgenic<br />
<strong>technology</strong>. Another approach being attempted by Kathiresan et al, (in press) is arresting<br />
sexual embryo development using a loss-of-function m utation <strong>and</strong> a meiosis-<br />
specific promoter. Plants with these genes would develop like the displospory form o f<br />
apomixis.<br />
REFERENCES<br />
Adams, W. W., Ill, <strong>and</strong> B. Demming-Adams. 1993. Energy dissipation <strong>and</strong> photoprotection<br />
in leaves o f higher plants. In H. Y. Yamamoto <strong>and</strong> C. M. <strong>Smith</strong> (eds.),<br />
Photosynthetic Responses to Environment. Current Topics in Plant Physiology, Vol.<br />
8. American Society o f Plant Physiologists, Rockvüle, MD.<br />
Aggarwal, R. K., D, S. Brar, <strong>and</strong> G. S. Khush. 1996. Two new genomes in the Oryza<br />
complex identified on the basis o f molecular divergence analysis using total genom<br />
ic DNA hybridization. Mol Gen. Genet. 254:1-12.<br />
Anonymous. 1964. <strong>Rice</strong> genetics <strong>and</strong> cytogenetics. Proceedings of the Symposium on<br />
<strong>Rice</strong> Genetics <strong>and</strong> Cytogenetics. Elsevier, Amsterdam,<br />
Athwal, D. S., <strong>and</strong> S. S. Virm ani. 1972. Cytoplasmic male sterility <strong>and</strong> hybrid breeding<br />
in rice. In <strong>Rice</strong> Breeding. International <strong>Rice</strong> Research Institute, Manila, The<br />
Philippines, pp. 615-620.<br />
Bastos, C. R„ L. E. Azzini, P. B. GaUo, J. Soave, L. H. S. Mello de Castro, <strong>and</strong> A. Tul-<br />
mann Neto. 2002. Improvement o f rice through somaculture <strong>and</strong> induced m u<br />
tation. In J. E. Hill (ed.). Proceedings of the 2nd Temperate <strong>Rice</strong> Conference, 13-17<br />
June 1999, Sacramento, CA.<br />
Bouchez, D,, <strong>and</strong> H. Höfte. 1998. Functional genomics in plants. Plant Physiol 118;<br />
725-732.<br />
Br<strong>and</strong>on, D. M „ H, L. Carnahan, J. N. Rutger, S. T. Tseng, C. W. Johnson, J. F, Williams,<br />
C. M. Wick, W. M . Canevari, S. C. Scardaci, <strong>and</strong> J. E. Hill. 1981. California <strong>Rice</strong>
Varieties; Description, Performance <strong>and</strong> Management Spec. Publ. 3271. Division<br />
o f Agricultural Science> University o f California, Berkeley, CA.<br />
Carnahan, H. L., C. W. Johnson, S. T. Tseng, <strong>and</strong> D. M . Br<strong>and</strong>on. 1979. Registration<br />
o f ‘‘Calm ochi-201” rice. CropSd 19:746.<br />
Causse, M. A., T. M. Fulton, Y, G, Cho, S. N. Ahn, J. Chunwongse, K. W u ,). Xiao,<br />
Z. Yu, P. C. Ronald, S. E. Harrington, G. Second, S. R. M cCouch, <strong>and</strong> S, D,<br />
Tanksley. 1994. Saturated molecular map o f rice genome based on an interspecific<br />
backcross population. Genetics 138:1251-1274.<br />
Cheng, Z., H. Yan, H. Yu, S. Tang, J. Jiang, M . Gu, <strong>and</strong> L. Zhu. 2001. Development<br />
<strong>and</strong> applications o f a complete set o f rice telotrisomics. Genetics 157:361-368.<br />
Croughan, T, P. 1999. Herbicide resistant rice. U.S. patent 5,952,553. Issued Sept. 14.<br />
Davis, M . D., <strong>and</strong> J. N. Rutger. 1976. Yield o f Fi, F2, <strong>and</strong> Fs hybrids o f rice (Oryza sativa<br />
L.). Euphytica 25:587-595.<br />
Eizenga, G. C., J. N. Rutger, <strong>and</strong> F. N. Lee. 2002a. Screening Oryza plants for rice<br />
sheath blight resistance. In J. E. Hill (ed.), Proceedings o f the 2nd Temperate Rke<br />
Conference, Sacramento, CA.<br />
Eizenga, G. C., T. H. Tai, F. N. Lee, <strong>and</strong> J. N. Rutger. 2002b. Identifying blast resistance<br />
in Oryza sp. <strong>and</strong> following its introgression into U.S. cultivated rice. In D. S.<br />
Brar (ed.), <strong>Rice</strong> Genetics IV: Proceedings of the 4th International <strong>Rice</strong> Genetics<br />
Symposium. International <strong>Rice</strong> Research Institute, Manila, The Philippines.<br />
Erickson, J. R. 1969. Cytoplasmic male sterility in rice {Oryza sativa L.). In Agronomy<br />
Abstracts. American Society o f Agronomy, Madison, W I. 6 p.<br />
Foyer, C. H ., <strong>and</strong> M . Lel<strong>and</strong>ais. 1993. The roles o f ascorbate in the regulation o f photosynthesis.<br />
In H. Y. Yamamoto <strong>and</strong> C. M . Sm ith (eds.), Photosynthetic Responses<br />
to the Environment Current Topics in Plant Physiology, Vol. 8. Am erican Society<br />
o f Plant Physiologists, RoclcviUe, MD.<br />
Fujimaki, H., S. Hiraiwa, K. Kushibuchi, <strong>and</strong> S. Tanalca. 1977. Artificially induced<br />
male-sterile mutants <strong>and</strong> their usages in rice breeding. Jpn. /. Breed. 27:70-77.<br />
Fukui, K. 1990. Localization o f rRNA genes on rice chromosomes. <strong>Rice</strong> Biotechnol Q,<br />
1:18.<br />
Fukui, K., <strong>and</strong> N. Ohmido. 2000. <strong>Rice</strong> genome research: an alternative approach<br />
based on molecular cytology. In J. R Gustafson (ed.), Genomes. Kluwer Aca-<br />
demic/Plenum Publishers, New York, pp. 109-121,<br />
Fukui, K., K, Kakeda, J. Hashimoto, <strong>and</strong> S. Matsuoka. 1987. In situ hybridization of<br />
*^T-labeled rRNA to rice chromosomes. <strong>Rice</strong> Genet Newsl 4:114.<br />
Guo, X. (ed.). 1991. Progress o f Studies on <strong>Rice</strong> Apomixis in China (in Chinese, with<br />
English abstracts). Chengdu, China.<br />
Gustafson, J. P,, <strong>and</strong> J. E. Dilié. 1992. Chromosome location o f Oryza sativa recombination<br />
linkage groups, Proc. Natl Acad. Sei. USA 89:8646-8650.<br />
Henderson, M. T. 1964. Cytogenetic studies at the Louisiana Agricultural Experiment<br />
Station o f species relationships in Oryza. In <strong>Rice</strong> Genetics <strong>and</strong> Cytogenetics. Elsevier,<br />
Amsterdam, pp. 103-110.<br />
Hu, C. H, 1968, Studies on the development o f twelve types o f trisomics in rice with<br />
reference to the genetic study <strong>and</strong> breeding program. J. Agrie. Assoc. China (N.S,)<br />
6 3:53-71.<br />
Hu, J., <strong>and</strong> J. N. Rutger, 1991, A streptomycin induced no-pollen male sterile mutant<br />
in rice (Oryza sativa L). /. Genet. Breed. 45:349-352.
Genotics, CytogGnetic, Mutation, qnd Beyond 171<br />
Hu, Jo <strong>and</strong> J. N. Rutger. 1992, Pollen characteristics <strong>and</strong> genetics o f induced <strong>and</strong><br />
spontaneous genetic male-sterile mutants in rice. Plant Breed, 109:97-107.<br />
Ikehashi, H., <strong>and</strong> H. Araki. 1984. Varietal screening for compatibility types revealed<br />
in F I fertility o f crosses in rice. Jpn. /. Breed. 34:304-312.<br />
Islam-Faridi, M . N,, T. Ishii, V, Kumai', L A. Sitch, <strong>and</strong> D. S. Brar. 1990. Chrom osom al<br />
location o f ribosomal RNA genes in rice by in situ hybridization. <strong>Rice</strong> Genet,<br />
NewsL 7:143.<br />
Isono Y., M. Satoh, <strong>and</strong> T. Onura. 1978. Characteristics o f carbohydrate-synthesis<br />
mutants, sugary <strong>and</strong> shrunken in rice. Jpn. J. Breed, 28(suppl.); 130-131.<br />
Iwata, N., <strong>and</strong> T. Omura. 1984. Studies on the trisom ics in rice plants {Oryza sativa<br />
L.). V I. An accom plishment o f a trisom ic series in japónica rice plants. Jpn, J.<br />
Genet. 59:199-204.<br />
Jackson, S. A., R G. Dong, <strong>and</strong> J. Jiang. 1999. Digital mapping o f bacterial artificial<br />
chromosomes by fluorescence in situ hybridization. Plant J. 17:581-587.<br />
Jena, K. K., <strong>and</strong> G. S. Khush. 2000. Exploitation o f species in rice improvement: opportunities,<br />
achievements <strong>and</strong> future challenges. In J. S. N<strong>and</strong>a (ed.). <strong>Rice</strong> Breeding<br />
<strong>and</strong> Genetics: Research Priorities <strong>and</strong> Challenges, Science Publisher, Enfield, NH,<br />
pp, 269-284.<br />
Jiang, J., B. S. Gill, G.-L. Wang, P. C. Ronald, <strong>and</strong> D. C. Ward. 1995. Metaphase <strong>and</strong><br />
interphase fluorescence in situ hybridization mapping o f the rice genome with<br />
bacterial artificial chromosomes. Froc, Natl Acad. Sei. USA 92:4487-4491,<br />
Jodon, N. E. 1956. Revision o f Pig. 3 to 6, “Present status o f rice genetics.” J. Agrie.<br />
Assoc. China (N.S.) 14:69-73.<br />
Jones, M. P., M. Dingkulin, G. K. Aluko, <strong>and</strong> M. Sem on. 1997. Interspecific Oryza<br />
sativa L. X. O. glaherrima Steud. progenies in upl<strong>and</strong> rice im provem ent Euphytica<br />
92:237-246.<br />
Khan, S. H. 1974, The identification <strong>and</strong> characterization o f a complete set o f twelve<br />
primary trisomics in rice (Oryza sativa L.). Ph.D. dissertation. University o f California,<br />
Davis, CA.<br />
Kathiresan, A., G. S. Kliush, <strong>and</strong> J. Bennett, In press. DMCl <strong>and</strong> REE5: Perspectives<br />
for arresting sexual embryo development in rice. In D. S. Brar (ed.) <strong>Rice</strong> Genetics<br />
IV: Proceedings of the 4th International <strong>Rice</strong> Genetics Symposium. International<br />
<strong>Rice</strong> Research Institute, Manila, The Philippines.<br />
BChush, G. S. (ed.). 1994. Apomixis: Exploiting Hybrid Vigor in <strong>Rice</strong>. International <strong>Rice</strong><br />
Research Institute, Manila, The Philippines.<br />
Khush, G. S., <strong>and</strong> T. Kinoshita. 1991. <strong>Rice</strong> karyotype, marker genes, <strong>and</strong> linkage<br />
groups. In G. S. Khush <strong>and</strong> G. H. Toenniessen (eds.). <strong>Rice</strong> Bio<strong>technology</strong>. CAB<br />
International, Wallingford, Oxon, Engl<strong>and</strong>, pp, 83-108.<br />
Khush, G. S., <strong>and</strong> R. J. Singh. 1991. Chromosome architecture <strong>and</strong> aneuploidy in<br />
rice. In P. K. Gupta <strong>and</strong> T, Tsuchiya (eds.), Developments in Plant Genetics <strong>and</strong><br />
Breeding, Vol. 2A, Chromosome Engineering in Plants: Genetics, Breeding, Evolution,<br />
Pt. A. Elsevier Science, Amsterdam, pp. 577-598.<br />
Khush, G. S., R. J. Singh, S. C, Sur, <strong>and</strong> A. L. Librojo, 1984. Prim ary trisomics o f rice:<br />
<strong>origin</strong>, morphology, cytology <strong>and</strong> use in linkage mapping. Genetics 107:141-163.<br />
Khush, G. S., K. Singh, T. Ishii, A. Parco, N. Huang, D. S. Brar, <strong>and</strong> D. S. Multani, 1996.<br />
Centromere mapping <strong>and</strong> orientation of the cytological, classical, <strong>and</strong> molecular<br />
linkage maps o f rice. In G. S. Khush (ed.). <strong>Rice</strong> Genetics III: Proceedings o f the
170 The <strong>Rice</strong> Plant<br />
Varieties; Description, Performance <strong>and</strong> Management. Spec. Publ. 3271. Division<br />
o f Agricultural Science, University of California, Berkeley, CA.<br />
Carnahan, H. L , C. W. Johnson, S. T. Tseng, <strong>and</strong> D. M . Br<strong>and</strong>on. 1979. Registration<br />
o f "C alm o ch i-20r'rice. Crop Sei 19:746.<br />
Causse, M. A., T. M. Pulton, Y. G, Cho, S, N. Ahn, J. Chunwongse, K. Wu, J. Xiao,<br />
Z. Yu, P. C. Ronald, S. E. Harrington, G. Second, S. R. McCouch, <strong>and</strong> S. D.<br />
Tanksley. 1994. Saturated molecular map o f rice genome based on an interspecific<br />
backcross population. Genetics 138:1251-1274.<br />
Cheng, Z., H. Yan, H. Yu, S, Tang, J. Jiang, M. Gu, <strong>and</strong> L. Zhu, 2001. Development<br />
<strong>and</strong> applications of a complete set o f rice telotrisomics. Genetics 157:361-368.<br />
Croughan, T. P, 1999. Herbicide resistant rice. U.S. patent 5,952,553. Issued Sept. 14.<br />
Davis, M. D., <strong>and</strong> J. N. Rutger, 1976. Yield o f Fj, Fa, <strong>and</strong> Fs hybrids o f rice (Oryza sativa<br />
L.). Euphytica 25:587-595.<br />
Eizenga, G. C., J. N. Rutger, <strong>and</strong> F. N. Lee. 2002a. Screening Oryza plants for rice<br />
sheath blight resistance. In J, E. HiU (ed.), Proceedings of the 2nd Temperate <strong>Rice</strong><br />
Conference, Sacramento, CA.<br />
Eizenga, G. C., T. H. Tai, F. N. Lee, <strong>and</strong> J. N. Rutger, 2002b. Identifying blast resistance<br />
in Oryza sp. <strong>and</strong> following its introgression into U.S. cultivated rice. In D. S.<br />
Brar (ed.), <strong>Rice</strong> Genetics IV; Proceedings of the 4th International <strong>Rice</strong> Genetics<br />
Symposium. International <strong>Rice</strong> Research Institute, Manila, The Philippines.<br />
Erickson, J. R. 1969. Cytoplasmic male sterility in rice (Oryza sativa L.). In Agronomy<br />
Abstracts. American Society o f Agronomy, Madison, W I. 6 p.<br />
Foyer, C. H., <strong>and</strong> M, Lel<strong>and</strong>ais. 1993. The roles o f ascorbate in the regulation o f photosynthesis.<br />
In H. Y. Yamamoto <strong>and</strong> C. M. Sm ith (eds.), Photosynthetic Responses<br />
to the Environment. Current Topics in Plant Physiology, Vol. 8. American Society<br />
of Plant Physiologists, Rockville, MD.<br />
Fujimaki, H., S. Hiraiwa, K. Kushibuchi, <strong>and</strong> S, Tanaka. 1977. Artificially induced<br />
male-sterile mutants <strong>and</strong> their usages in rice breeding. Jpn. J. Breed. 27:70-77.<br />
Fukui, K. 1990. Localization o f rRNA genes on rice chromosomes. <strong>Rice</strong> Biotechnol. Q.<br />
1:18.<br />
Fukui, K., <strong>and</strong> N. Ohmido. 2000. <strong>Rice</strong> genome research: an alternative approach<br />
based on molecular cytology. In J. P. Gustafson (ed.), Genomes. lOuwer Aca-<br />
deraic/Plenum Publishers, New York, pp. 109-121.<br />
Fukui, K., K. Kakeda, J. Hashimoto, <strong>and</strong> S. Matsuoka. 1987. In situ hybridization of<br />
'“ I-labeled rRNA to rice chromosomes. <strong>Rice</strong> Genet Newsl. 4:114.<br />
Guo, X, (ed.). 1991. Progress of Studies on <strong>Rice</strong> Apomixis in China (in Chinese, witli<br />
English abstracts). Chengdu, China.<br />
Gustafson, J. R, <strong>and</strong> J. E. D ill6 .1992. Chromosome location o f Oryza sativa recombination<br />
linkage groups. Proc. Natl. Acad. Sei USA 89:8646-8650.<br />
Henderson, M. T. 1964. Cytogenetic studies at the Louisiana Agricultural Experiment<br />
Station o f species relationships in Oryza. In <strong>Rice</strong> Genetics <strong>and</strong> Cytogenetics. Elsevier,<br />
Amsterdam, pp. 103-110.<br />
Hu, C. H. 1968. Studies on the development o f twelve types o f trisomics in rice with<br />
reference to the genetic study <strong>and</strong> breeding program. /. Agric. Assoc. China (N.S.)<br />
63:53-71.<br />
Hu, J., <strong>and</strong> J. N. Rutger. 1991. A streptomycin induced no-pollen male sterile mutant<br />
in rice {Oryza sativa L) .}. Genet. Breed. 45:349-352.
Genetics, Cytogenetics, Mulation, <strong>and</strong> Beyond 171<br />
Hu, J., <strong>and</strong> J. N. Rutger. 1992. Pollen characteristics <strong>and</strong> genetics o f induced <strong>and</strong><br />
spontaneous genetic male-sterile mutants in rice. Plant Breed. 109:97-107.<br />
Ikehashi, H., <strong>and</strong> H. Araki. 1984. Varietal screening for compatibility types revealed<br />
in F I fertility of crosses in rice. fpn. J. Breed. 34:304—312.<br />
Islam-Faridi, M. N., T. Ishii, V. Kumar, L. A. Sitch, <strong>and</strong> D. S, Brar. 1990. Chromosomal<br />
location o f ribosomal RNA genes in rice by in situ hybridization. <strong>Rice</strong> Genet.<br />
Newsl. 7:143.<br />
Isono Y., M . Satoh, <strong>and</strong> T. Onura. 1978. Characteristics o f carbohydrate-synthesis<br />
mutants, sugary <strong>and</strong> shrunken in rice. Jpn. J. Breed. 28(suppl.):130-131.<br />
Iwata, N., <strong>and</strong> T. Omura. 1984. Studies on the trisom ks in rice plants (Oryza sativa<br />
L,). V I. An accomplishment o f a trisomic series in japónica rice plants. Jpn. J.<br />
Genet. 59:199-204.<br />
Jackson, S. A., F. G. Dong, <strong>and</strong> J. Jiang. 1999. Digital mapping o f bacterial artificial<br />
chromosomes by fluorescence in situ hybridization. Plant J. 17:581-587.<br />
Jena, K. K., <strong>and</strong> G. S. Khush. 2000. Exploitation o f species in rice improvement: opportunities,<br />
achievements <strong>and</strong> future challenges. In J. S. N<strong>and</strong>a (ed.), <strong>Rice</strong> Breeding<br />
<strong>and</strong> Genetics: Research Priorities <strong>and</strong> Challenges. Science Publisher, Enfield, NH,<br />
pp. 269-284.<br />
Jiang, J., B. S. Gill, G.-L. Wang, P. C. Ronald, <strong>and</strong> D. C. Ward. 1995. Metaphase <strong>and</strong><br />
interphase fluorescence in situ hybridization mapping o f the rice genome with<br />
bacterial artificial chromosomes. Proc. Natl. Acad. Sei. l/SA 92:4487-4491.<br />
Jodon, N. E. 1956. Revision of Fig. 3 to 6, “Present status of rice genetics.” /. Agrie.<br />
Assoc. China (N.S.) 14:69-73.<br />
Jones, M. P., M . Dingkuhn, G. K. Aluko, <strong>and</strong> M . Semon. 1997. Interspecific Oryza<br />
sativa L. X. O. glaberrima Steud. progenies in upl<strong>and</strong> rice improvement. Euphytica<br />
92:237—246.<br />
Khan, S. H. 1974. The identification <strong>and</strong> characterization o f a complete set o f twelve<br />
primary trisomics in rice (Oryza sativa L.). Ph.D, dissertation. University o f California,<br />
Davis, CA.<br />
Kathiresan, A., G. S. Khush, <strong>and</strong> J. Bennett. In press, DMCl <strong>and</strong> REE5: Perspectives<br />
for arresting sexual embryo development in rice. In D. S. Brar (ed.) <strong>Rice</strong> Genetics<br />
IV: Proceedings o f the 4th International <strong>Rice</strong> Genetics Symposium. International<br />
<strong>Rice</strong> Research Institute, Manila, The Philippines.<br />
Khush, G. S. (ed.). 1994. Apomixis: Exploiting Hybrid Vigor in <strong>Rice</strong>. International <strong>Rice</strong><br />
Research Institute, M anila, The Philippines.<br />
Khush, G. S., <strong>and</strong> T. Kinoshita, 1991. <strong>Rice</strong> karyotype, marker genes, <strong>and</strong> linkage<br />
groups. In G. S. Kliush <strong>and</strong> G. H. Toenniessen (eds.), <strong>Rice</strong> Bio<strong>technology</strong>. CAB.<br />
International, Wallingford, Oxon, Engl<strong>and</strong>, pp. 83-108.<br />
Khush, G. S., <strong>and</strong> R. J, Singh. 1991. Chromosome architecture <strong>and</strong> aneuploidy in<br />
rice. In P. K. Gupta <strong>and</strong> T. Tsuchiya (eds.). Developments in Plant Genetics <strong>and</strong><br />
Breedings Vol. 2A, Chromosome Engineering in Plants: Genetics¡ Breedings Evolution,<br />
Pt. A. Elsevier Science, Amsterdam, pp. 577-598.<br />
Khush, G. S., R. J. Singh, S. C. Sur, <strong>and</strong> A. L. Librojo. 1984. Primary trisomics o f rice:<br />
<strong>origin</strong>, morphology, cytology <strong>and</strong> use in linkage mapping. Genetics 107:141-163.<br />
Khush, G. S., K. Singh, T. Ishii, A. Parco, N. Huang, D. S. Brar, <strong>and</strong> D. S. Multani. 1996.<br />
Centromere mapping <strong>and</strong> orientation o f the cytological, classical, <strong>and</strong> molecular<br />
linkage maps o f rice. In G. S. Khush (ed.). <strong>Rice</strong> Genetics III: Proceedings of the
172 The <strong>Rice</strong> Plant<br />
:IV-!<br />
3rd International <strong>Rice</strong> Genetics Symposium. International <strong>Rice</strong> Research Institute,<br />
Manila, The Philippines, pp. 57-75.<br />
Kurata, N., Y. Nagamura, K. Yamamoto, Y. Harushima, N. Su e,J. Wu, B. A. Antonio,<br />
A. Shomura, T. Shimizu, S. Y. Lin, T. Inoue, A. Fukuda, T. Shimano, Y. Kuboki,<br />
T, Toyama, Y. Miyamoto, T. Kirihara, K. Hayasaka, A. Miyao, L. M onna, H. S.<br />
Zhong, Y. Tamura, A.-X. Wang, T. M omma, Y. Umehara, M . Yano, T. Sasaki,<br />
<strong>and</strong> Y. M inobe. 1994, A 300-kilobase interval genetic map o f rice including 883<br />
expressed sequences, Nat. Genet. 8:365-372.<br />
Kuwada, Y. 1910. A cytological study o f Oryza sativa L. Shokubutsugaku Zasshi 24:<br />
267-281.<br />
Larson, S, R., J. N. Rutger, K. A. Young, <strong>and</strong> V. Raboy. 2000. Isolation <strong>and</strong> genetic<br />
linkage mapping o f a non-lethal rice {Oryza sativa L.) low phytic acid 1 mutation.<br />
Crop Sei. 40:1397-1405.<br />
Lin, S. C,, <strong>and</strong> L. P. Yuan. 1980. Hybrid rice breeding in China. In Hybrid <strong>Rice</strong>. International<br />
<strong>Rice</strong> Research Institute, M anila, The Philippines, pp. 39-54.<br />
Mackill, D. J., <strong>and</strong> J. N. Rutger, 1979. Inheritance o f induced-mutant semidwarfing<br />
genes in rice. /•Hered. 70:335-341.<br />
Mackill, D. J., J. N. Rutger, <strong>and</strong> C. W. Johnson. 1994. Allelism <strong>and</strong> pleiotropy of<br />
extended upper internode rice mutants. SAiJRAO /. 26:11-17.<br />
Mackill, D. J., P. M. Colowit, <strong>and</strong> J. J. Oster. 1998. An AFLP marker linked to stem rot<br />
resistance in rice. In Plant <strong>and</strong> Animal Genome VI. San Diego, CA, p. 143.<br />
Maluszynski, M. 1999. Crop germplasm enhancement through m utation techniques.<br />
In Proceedings o f the International Symposium on <strong>Rice</strong> Germplasm Evaluation <strong>and</strong><br />
Enhancement. Spec. Rep. 195. University of Arkansas, Stuttgart, AR, pp. 74-82.<br />
Mann, J. 2000. Hybrid <strong>Rice</strong> Field Tour. <strong>Rice</strong>Tec, Inc., Alvin, TX.<br />
M cllrath, W. O., N. E. Jodon, E. A. Sonnier, G. J. Trahan, <strong>and</strong> M . A. Marchetti. 1979.<br />
Registration of “LA 110” rice, Crop Sei 19:744-745.<br />
McKenzie, K. S., J. E. Board, K. W. Foster, <strong>and</strong> J. N. Rutger. 1978. Inheritance of<br />
heading date of an induced mutant for early m aturity in rice (Oryza sativa L.).<br />
SABRAOJ. 10:96-102.<br />
Mese, M. D., L. E. Azzini, <strong>and</strong> J. N. Rutger, 1984, Isolation o f genetic male sterüe<br />
mutants in a semidwarf japónica rice cultivar. Crop Sei 24:523-525.<br />
Misra, R. N„ K. K. Jena, <strong>and</strong> P. Sen. 1986. Cytogenetics o f trisomics in indica rices. In<br />
<strong>Rice</strong> Genetics: Proceedings of the International <strong>Rice</strong> Genetics Symposium. International<br />
<strong>Rice</strong> Research Institute, Manila, The Philippines, pp. 173-183.<br />
Myers, A. M., M . K. Morell, M. G. James, <strong>and</strong> S. G. Ball. 2000. Recent progress toward<br />
underst<strong>and</strong>ing biosynthesis o f the amylopectin crystal. Plant Physiol 122(4) :989-<br />
997.<br />
Nagao, S., <strong>and</strong> M. Takahashi. 1963. Genetical studies on rice plant. X XV II. Trial construction<br />
o f twelve linkage groups o f Japanese rice. /. Fac. Agrie. Hokkaido Univ.<br />
53:72-130.<br />
Neuffer, M , G., E. H. Coe, <strong>and</strong> S. R. Wessler. 1997. Mutants of Maize. Cold Spring<br />
Harbor Laboratory Press, Plainview, NY.<br />
Normile, D. 1999. Crossing rice strains to keep Asia’s rice bowls brim m ing. Science<br />
283:313.<br />
Nowick, E. M. 1986. Chromosome pairing in Oryza sativa L. x O. latifolia Desv.<br />
hybrids. Can. J. Genet. Cytol. 28:278-281.
1<br />
Genetic, CytogenelitS; Mutation, <strong>and</strong> Beyond 173<br />
Nowick, E, M ., <strong>and</strong> J. F. Robinson. 1988. Evaluation o f Oryza sp. for resistance to<br />
the rice water weevil. In 80th Annual Research Report of the <strong>Rice</strong> Research Station^<br />
Crowley, LA, pp. 4 7 -51.<br />
Oard, J. H., <strong>and</strong> J. N. Rutger, 1988. Selection o f rice lines tolerant to an imidazolinone<br />
herbicide: a progress report. In Proceedings of the 22nd <strong>Rice</strong> Technical Working<br />
Group, Davis, CA, p. 19.<br />
Oard, J. H., J. Hu, <strong>and</strong> J. N. Rutger. 1991. Genetic analysis o f male sterility in rice<br />
mutants with environmentally influenced levels o f fertility. Euphytica 5 5 :1 7 9 -<br />
186.<br />
Parnell, R R., G. N. R. Ayyangar, <strong>and</strong> K. Ramiah. 1917. Inheritance o f characters in<br />
rice. I. Mem. Dep. Agrie. India Bot Ser. 9:75-105.<br />
Rutger, J. N. 1985. Plant breeding problems needing solutions: conventional or biotechnological.<br />
In Proceedings of the 1985 California Plant <strong>and</strong> Soil Conference,<br />
Fresno, CA, pp. 87-90.<br />
Rutger, J, N, 1988. Outcrossing mechanisms <strong>and</strong> hybrid seed <strong>production</strong>. In Hybrid<br />
<strong>Rice</strong>: Proceedings of the International Symposium on Hybrid <strong>Rice</strong>, Changsha,<br />
China. International <strong>Rice</strong> Research Institute, Manila, The Philippines.<br />
Rutger, J. N. 1992a. Searching for apomixis in rice. In Proceedings of the Apomixis<br />
Workshop. Publication U SD A -A RS-104. U.S. Department o f Agriculture, Washington,<br />
DC, pp. 36-39.<br />
Rutger, J. N. 1992b. Impact of Mutation Breeding in <strong>Rice</strong>: A Review. M utât. Breed. Rev.<br />
8. FAO/IAEA, Vienna, pp. 1-23,<br />
Rutger, J. N. 1998. <strong>Rice</strong> genetics <strong>and</strong> germplasm enhancement. In R. J. Norman <strong>and</strong><br />
T. H. Johnston (eds.), <strong>Rice</strong> Research Studies. Ark. Exp. Stn. Res. Ser, 460, pp. 12-15.<br />
Rutger, J. N. 1999. Improving rice quality for value-added applications througli induced<br />
mutation. In E. T. Champagne (ed.), <strong>Rice</strong> Quality: Foundation for Value—<br />
Proceedings of the <strong>Rice</strong> Utilization Workshop. USA <strong>Rice</strong> Federation, Houston, TX ,<br />
pp. 110-112.<br />
Rutger, J. N. 2001. Induction o f photoperiod sensitive genetic male steriles for use in<br />
hybrid rice seed <strong>production</strong>. Euphytica. 120:399-400.<br />
Rutger, J. N., <strong>and</strong> H. L. Carnahan. 1981. A fourth genetic element for facilitating<br />
hybrid seed <strong>production</strong> in cereals: a recessive tall in rice. Crop Sei. 21:373-376.<br />
Rutger, J. N., <strong>and</strong> H. L. Carnahan. 1982. Recessive taU: a fourth genetic element to<br />
facilitate hybrid cereal <strong>production</strong>. U.S. patent 4,351,130.<br />
Rutger, J. N., <strong>and</strong> G. W. Schaeffer. 1994. An environmentally sensitive genetic male<br />
sterile mutant from anther culture of rice. In E. Humphreys, E. A. Murray, W. S.<br />
Clampett, <strong>and</strong> L. G. Lewin (eds.). Temperate <strong>Rice</strong>: Achievements <strong>and</strong> Potential.<br />
Conference Organizing Committee, NSW Agriculture, Griffith, New South<br />
Wales, Australia, pp. 171-174.<br />
Rutger, J. N., <strong>and</strong> C. Shinjo, 1980. Male sterility in rice <strong>and</strong> its potential use in breeding.<br />
In Innovative Approaches to <strong>Rice</strong> Breeding. International <strong>Rice</strong> Research Institute,<br />
Manila, The Philippines, pp. 53-66.<br />
Rutger, J. N., M. L. Peterson, C. H. Hu, <strong>and</strong> W. F. Lehman. 1976. Induction o f useful<br />
short stature <strong>and</strong> early maturing mutants in japónica rice {Oryza sativa L.)<br />
cultivars. Crop Sei. 16:631-635.<br />
Rutger, J. N., M . L. Peterson, <strong>and</strong> C. H. Hu. 1977. Registration o f Calrose 76 rice. Crop<br />
Sei. 17:978.
174 The <strong>Rice</strong> Plant<br />
Rutger, J. N., M. L. Peterson, H. L. Carnahan, <strong>and</strong> D. M. Br<strong>and</strong>on. 1979. Registration<br />
of “M -lO l” rice. Crop Sei 19:929.<br />
Rutger, J. N., J. Hu, <strong>and</strong> J. M. Ch<strong>and</strong>ler. 1986. Searching for aponaixis in rice. In 1986<br />
Agronomy Abstracts. Am erican Society o f Agronomy, Madison, WI> p. 80.<br />
Rutger, J. N., R. A. Figoni, R. K. Webster, J. J. Oster, <strong>and</strong> K. S. McKenzie. 1987. Registration<br />
o f early maturing, marker gene, <strong>and</strong> stem rot resistant germplasm lines<br />
o f rice. Crop Sei 27:1319-1320.<br />
Shastry, S. V. S., D. R. Rangao Rao, <strong>and</strong> R. N. Misra. 1960. Pachytene analysis in<br />
Oryza. I. Chromosome morphology in Oryza sativa L. Indian J, Genet Plant<br />
Breed. 29:15-21.<br />
Shinjo, C. 1969. Cytoplasmic-genetic male sterility in cultivated rice, Oryza sativa L.<br />
II. The inheritance of male sterility. Jpn. J. Genet 44:149-156.<br />
Shishido, R., S. Apistwanich, N. Ohmido, Y. Oldnaka, K. M ori, <strong>and</strong> IC Fukui. 1998.<br />
Detection o f specific chromosom e reduction in rice somatic hybrids with the<br />
A, B, <strong>and</strong> C genomes by multicolor genomic in situ hybridization. Theor. Appl<br />
Genet 97:1013-1018.<br />
Singh, K., D. S. Multani, <strong>and</strong> G. S. Khush. 1996. Secondary trisom ics <strong>and</strong> telotrisomics<br />
o f rice: <strong>origin</strong>, characterization, <strong>and</strong> use in determining orientation o f the chrom<br />
osom e map. Genetics 143:517-529.<br />
Singh, R. 1, <strong>and</strong> H. Ikehashi. 1979. Induction o f m onogenic recessive male sterility in<br />
IR36 by ethyleneimine treatment. Int. <strong>Rice</strong> Res. NewsL 4 :3 -4 .<br />
Singh, R. J., <strong>and</strong> G. S. Khush. 2000. Cytogenetics o f rice. In J, S. N<strong>and</strong>a (ed.), <strong>Rice</strong><br />
Breeding <strong>and</strong> Genetics: Research Priorities <strong>and</strong> Challenges. Science Publishers, Enfield,<br />
NH, pp. 285-310.<br />
^<br />
Song, Y. C., <strong>and</strong> J. P. Gustafson. 1995. The physical location o f fourteen RFLP markers<br />
in rice {Oryza sativa L.). Theor, Appl. Genet. 90:113.<br />
Stansel, J. W., <strong>and</strong> J. P. Craigmües. 1966. Hybrid rice: problems <strong>and</strong> potentials. <strong>Rice</strong>}.<br />
69(5):14~ 15,46.<br />
Trees, S. C., <strong>and</strong> J. N. Rutger. 1978. Inheritance o f four genetic male steriles in rice.<br />
J. Hered. 69:270-272.<br />
Tseng, S. T , <strong>and</strong> J. J. Oster. 1994. Registration o f 87-Y -550, a rice germplasm line<br />
resistant to stem rot disease. Crop Sei 34:314.<br />
USDA. 1963. <strong>Rice</strong> Gene Symbolization <strong>and</strong> Linkage Groups. USDA-ARS Publication<br />
ARS 34-28. U.S. Department of Agriculture, Washington, DC.<br />
Virmani, S. S. 1994. Heterosis <strong>and</strong> hybrid rice breeding. In R. Frankel, M. Grossman,<br />
H. F. Linskens, P. Maliga, <strong>and</strong> R. Riley (eds.), Monographs on the Theoretical<br />
Applications of Genetics, Vol. 22. Springer-Verlag, Berlin, p. 189.<br />
Wang, Z. X., <strong>and</strong> N. Iwata. 1995. Aneuhaploids <strong>and</strong> tetrasomics in rice {Oryza sativa<br />
L.) derived from anther culture o f trisomics. Genome 38:696-705.<br />
Yan, H. H., S. K. M in, <strong>and</strong> L. H. Zhu. 1999. Visualization o f Oryza eichingeri chrom o<br />
somes in intergenomic hybrid plants from O. sativa x O. eichingeri via fluorescent<br />
in situ hybridization. Genome 4 2:48-51.<br />
Yano, M ., K. Okuno, H. Satoh, <strong>and</strong> T. Omura. 1988. Chrom osom al location o f genes<br />
conditioning low anylose content o f endosperm starches in rice, Oryza sativa L.<br />
Theor. Appl. Genet 76:183-189.<br />
Yasui, H., <strong>and</strong> N. Iwata. 1998a. Cytogenetics o f ditelosomic alien addition lines in rice<br />
{Oryza sativa L.) each carrying an extra pair o f telocentric chromosom es o f O.<br />
punctata Kotschy. J. Fac. Agric., Kyushu Univ. 4 3 :1 -9 .
!----^<br />
Genetics, Cytogenetics, Mutation, <strong>and</strong> Beyond 175<br />
Yasui, H., <strong>and</strong> N. Iwata. 1998b. Development o f raonotelosom ic <strong>and</strong> monoacrosoraic<br />
alien addition lines in rice (Oryza sativa L.) carrying a single chromosom e o f O.<br />
punctata Kotschy. Breed. Sci 48; 181-186.<br />
Yasui, H., K .-I. Nonomura, <strong>and</strong> N. Iwata. 1997. Detection o f alien Oryza punctata<br />
Kotschy chromosom es in rice, Oryza sativa L., by genomic in situ hybridization.<br />
/. Fac. Agrie. Kyushu Univ. 42:63-68.<br />
Yuan, L. P., <strong>and</strong> X. Q. Fu. 1995. Technology of Hybrid Rke Production. Food <strong>and</strong><br />
Agriculture Organization o f the United Nations, Viale deUe Terme di Caracalla,<br />
Rome,<br />
Yunold, T., <strong>and</strong> Y, Masuyama. 1945. Investigation on tlie later generations o f au-<br />
totriploid rice plants. Scl Bull. Fac. Agrie. Kyushu Univ. 11:182-216.<br />
Zhang, T. B., <strong>and</strong> H. Zhu. 1986. Studies on trisomics developed from a Chinese<br />
cultivar, Guangluai 4. <strong>Rice</strong> Genet. Newsl. 3:65.<br />
Zhu, X ., <strong>and</strong> J. N. Rutger, 1999. Inheritance of induced dom inant <strong>and</strong> recessive genetic<br />
male-sterile mutants in rice (Oryza sativa. L ) . SABRAO J. 31:17-22.<br />
Zongtan, S., <strong>and</strong> H, Zuhua. 1989. Transfer eui gene to WA-MS line Zhen-Shan 91A<br />
(Oryza spp. indica) <strong>and</strong> eliminating its panicle enclosure. Int. <strong>Rice</strong> Res. Newsl.<br />
1 4 (4):8-9.
i !'
Chapter<br />
2 ^<br />
Techniques for Development<br />
of New Cultivars<br />
Anna Myers McClung<br />
USDA-ARS<br />
Texas A&M Research <strong>and</strong> Extension Center<br />
Beaumont, Texas<br />
U.S. RICE BREEDING PROGRAMS<br />
BREEDING OBJECTIVES AND METHODS OF SELECTION<br />
Agronomic Traits<br />
Plant Height <strong>and</strong> Lodging Resistance<br />
Tillering<br />
Maturity<br />
Yield<br />
Shattering <strong>and</strong> Threshability<br />
Disease Resistance<br />
<strong>Rice</strong> Blast Disease<br />
Sheath Blight<br />
Stem Rot<br />
Minor Diseases<br />
Insect Resistance<br />
Tolerance to Envrionmentol Stress<br />
Seedling Vigor<br />
Tolerance to Extremes in Temperatures<br />
Reduced Water Use<br />
Selection for Components of <strong>Rice</strong> Quality<br />
Amylose, Protein, Alkali Spreading Value, <strong>and</strong> Amylograms<br />
Molecular Markers for Cooking Quality<br />
Milling Quality<br />
Grain Appearance<br />
Specialty <strong>Rice</strong>s<br />
DEVELOPING GENETIC VARIABILITY<br />
<strong>Rice</strong>: Origin, History, Technology, <strong>and</strong> Production, edited by C. Wayne <strong>Smith</strong><br />
ISBN 0-471-34516-4 © <strong>2003</strong> John Wiley 8t Sons, Inc.<br />
177
178 The <strong>Rice</strong> Plant<br />
BREEDING METHODS<br />
FIELD TESTING METHODS<br />
EXPECTATIONS FOR THE FUTURE<br />
REFERENCES<br />
U.S. RICE BREEDING PROGRAMS<br />
Public rice breeding efforts started in the United States in the early 1930s. Research<br />
programs were established in California, Texas, Louisiana, <strong>and</strong> Arkansas. M ost of<br />
these programs were initiated by the U.S. Departm ent o f Agriculture (USDA), but<br />
most were later transferred to state experiment station programs or producer-run<br />
organizations (Rutger <strong>and</strong> Bollich, 1991). Public breeding programs were later established<br />
in Mississippi, Florida, <strong>and</strong> m ost recently, Missouri. Today, the USDA Agricultural<br />
Research Service has active research programs in Texas, Arkansas, <strong>and</strong> California,<br />
focused on rice genetics, <strong>production</strong>, <strong>and</strong> quality issues whereas m ost postharvest rice<br />
research is conducted at New Orleans, Louisiana <strong>and</strong> Athens, Georgia.<br />
All o f the rice breeding stations are located in the predominant rice-growing areas<br />
of the country (e.g., Biggs, California; Stoneville, Mississippi; Stuttgart, Arkansas;<br />
Beaumont, Texas; Belle Glade, Florida; Malden, Missouri; <strong>and</strong> Crowley, Louisiana).<br />
Location o f these research stations in the heart o f these rice-growing areas has permitted<br />
close interaction o f researchers with rice producers <strong>and</strong> millers. This has resulted<br />
in abetter underst<strong>and</strong>ing o f tlie U.S. industry’s needs <strong>and</strong> has helped to focus breeding<br />
objectives. Many o f these research programs also receive funding support through<br />
check-off funds from their state rice producers.<br />
O f the U.S. cultivars that have been released during tlie last two decades, most<br />
have taken about 10 years to develop. Thus it is im portant for breeders to be aware of<br />
the industry’s needs since the crosses that are made today will determine the cultivars<br />
that are available a decade from now. Recently, there has been increasing interest from<br />
the private sector in developing rice cultivars that can be used in specialty markets,<br />
possess proprietary <strong>technology</strong> (e.g., herbicide resistance), or can be used in hybrids.<br />
However, m ost public breeding programs are directed toward increasing <strong>production</strong><br />
capacity (grain <strong>and</strong> milling yield), decreasing risks <strong>and</strong> input costs to the producer<br />
(e.g., disease resistance), or increasing value (specialty rices for niche markets). The<br />
total income that a producer receives is related to quantity o f grain that is produced as<br />
well as the milling quality. Thus, both o f these com ponents are fundamental to most<br />
breeding programs.<br />
Although tliere has been a tremendous impact in rice <strong>production</strong> due to new<br />
technologies <strong>and</strong> cultural management practices, genetic improvement has been an<br />
important com ponent in the growth o f the industry. Table 2.4.1 compares two cultivars<br />
that were widely grown in tlie southern United States <strong>and</strong> demonstrates some<br />
of the changes that have been made in agronomic traits <strong>and</strong> milling quality through<br />
breeding (McClung, 1993).<br />
BREEDING OBJECTIVES AND METHODS OF SELECTION<br />
<strong>Rice</strong> breeding objectives have much in com m on with varietal improvement programs<br />
of other small grains: improve yield, disease resistance, insect resistance, lodging
Techniques for Development of New Cultivars 179<br />
TABLE 2.4.1.<br />
Programs<br />
Example of Progress from Breeding Efforts in U.S. <strong>Rice</strong> Varietal Development<br />
Coltivar<br />
Year of<br />
Release<br />
Yield<br />
{kg/ha)<br />
H ead <strong>Rice</strong><br />
{%)<br />
Height<br />
(era)<br />
H ead ing<br />
(days)<br />
Harvest<br />
(days)<br />
Bluebonnet 1944 5753 55 142 101 130<br />
Lemont 1983 7334 63 84 88 118<br />
Improvement -1-1581 +8 -58 -13 -12<br />
resistance, <strong>and</strong> so on. However, because rice is one o f the few grain crops tlrat goes<br />
from the field to the consumer with little modification, factors which affect rice<br />
quality are extremely important. In addition, ratoon or second-crop potential is also<br />
im portant in Texas <strong>and</strong> Louisiana, where there is a long growing season.<br />
Agronomic Traifs<br />
Plont Height <strong>and</strong> Lodging Resistance<br />
Since the development o f Bellm ont (Bollich, et al., 1983) <strong>and</strong> Calrose 76 (Rutger et al.,<br />
1977) the sdl semidwarf gene has been used extensively in U.S. rice breeding programs<br />
to reduce susceptibility to lodging (Rutger <strong>and</strong> Bollich, 1991). Other semidwarf genes<br />
have been reported to have negative affects on yield (Rutger, 1992), whereas the sdl<br />
gene has been shown to convey high tillering <strong>and</strong> harvest index (Roberts et al., 1993).<br />
Semidwarf cultivars average 85 to 95 cm in height, whereas current conventional<br />
height cultivars average 10 cm taller. There are also polygenic sources o f reduced<br />
height that have been used in breeding (Rutger <strong>and</strong> Bollich, 1991) <strong>and</strong> intermediate-<br />
height cultivars such as Labelle (Bollich et al., 1973), Maybelle (Bollich et al., 1991),<br />
<strong>and</strong> Jackson (Bollich et al., 1996) that have been commercially im portant. Reduced-<br />
height cultivars have allowed producers to increase fertilizer rates <strong>and</strong> increase yields<br />
without excessive loss due to lodging. Although the semidwarf gene has been used<br />
widely in U.S. cultivars, conventional-height varieties such as Drew (Moldenliauer<br />
et al., 1998), Kaybonnet (Gravois et al., 1995), <strong>and</strong> Earl (Linscombe et al., 2001), have<br />
recently been released.<br />
Breeders typically select for cultivars that will not be too short for combine harvesting<br />
in fields tliat are not laser leveled nor too tall <strong>and</strong> susceptible to lodging. Height<br />
is determined after flowering by measuring from the soil level to the tip of the panicle.<br />
Lodging is observed more com m only in large <strong>production</strong> fields than in experimental<br />
plots, but when it does occur, the percent of the plot lodged is recorded.<br />
Tillering<br />
U.S. cultivars have been bred to have relatively few tillers per plant that develop over<br />
a short period o f time. The main purpose o f this is to increase the uniform ity o f grain<br />
development <strong>and</strong> m aturation, which will enhance milling yield. A com parison o f tlie<br />
high-yielding indica cultivar Te Qing with the U.S. cultivar Gulfm ont demonstrated<br />
that Te Qing produced more panicle-bearing tillers (419 vs. 347) <strong>and</strong> spikelets per<br />
panicle (212 vs. 121) (Wu et al., 1998). Because the number o f panicle-bearing stems
180 The <strong>Rice</strong> Plont<br />
can vary in response to seeding rate, most breeders will use a com m on seeding rate<br />
to compare genotypes for tillering capacity.<br />
Maturit/<br />
M ost U.S, cultivars range 105 to 120 days in harvest maturity. The very early maturing<br />
cultivars are grown com monly in environments having a short growing season or<br />
where producers are interested in ratoon crop <strong>production</strong>. For the latter, tlie main<br />
crop has to be cut soon enough to allow the ratoon crop to develop <strong>and</strong> mature.<br />
Later-maturing cultivars are grown in areas where ratoon cropping is not practiced<br />
<strong>and</strong> producers try to utilize the full length o f the available growing season. In many<br />
rice-growing areas o f the United States, water availability is becoming more restricted,<br />
due to dem<strong>and</strong>s from urban growtli. Thus there is increasing interest in developing<br />
higher-yielding single-crop cultivars that may produce m ore grain per unit o f water<br />
used.<br />
Days from emergence to when 50% o f the plants in the plot have flowered are<br />
recorded as “days to heading.” The num ber o f days to harvest is m ore subjective.<br />
Commonly, as plots begin to ripen, breeders will harvest a small sample o f grain <strong>and</strong><br />
will determine the grain moisture. This is done on several samples to “calibrate their<br />
eyes” for determining when senescing plots are at 18 to 22% moisture, the optimum<br />
harvest moisture for maximizing milling quality. The num ber o f days from emergence<br />
to harvest date is recorded as “days to m aturity”<br />
Yield<br />
<strong>Rice</strong> yield is a function o f the number o f seed-bearing tillers, number o f kernels<br />
per panicle, <strong>and</strong> grain weight. Yield potential is commonly determined by com bineharvesting<br />
field plots that are approximately 5 m^ in size (Figure 2.4.1). In situations<br />
where plots are cut by h<strong>and</strong>, usually the two center rows o f a six- or seven-row plot<br />
(approximately 1.8 m^) wiU be harvested. Primarily along the Gulf Coast where there<br />
is an extended growing season, producers can also harvest a ratoon or second crop.<br />
To evaluate ratoon crop potential, breeders wUl harvest the main crop <strong>and</strong> leave<br />
about 20 to 30 cm of stubble. The straw is removed <strong>and</strong> the field is reflooded <strong>and</strong><br />
fertilized (Figure 2.4.2). In approximately 60 days, a second crop can be harvested that<br />
may be up to 50% o f the main crop yield. Producers have called this the providence<br />
crop because high yields are produced with relatively little input. Factors influencing<br />
ratoon crop yield potential include the health o f the m ain crop plant, the m ain crop<br />
yield, the total nonstructural carbohydrate content o f the main crop stems (Thrner<br />
<strong>and</strong> lund, 1993), <strong>and</strong> weather conditions during growth <strong>and</strong> flowering o f the ratoon<br />
crop, Ratoon yield from experimental plots tends to be more variable than main crop<br />
estimates, <strong>and</strong> thus it is m ore difficult to make progress from selection (Bollich et al.<br />
1988). Developing a better <strong>and</strong> less labor-intensive predictor of ratoon crop potential<br />
would benefit breeding efforts. The total yield of the crop is determined by summation<br />
of the main crop <strong>and</strong> ratoon crop yields.<br />
Shottering <strong>and</strong> Threshability<br />
Shatter-resistant cultivars do not lose their grain prior to harvest. This can be a problem<br />
when storms or high winds occur shortly before harvest. Conversely, when rice
Techniques for Development of New Cultivars 181<br />
Figure 2.4,1.<br />
A small plot combine is used to harvest experimental plots.<br />
Figure 2.4.2. After horvest of the main crop, the straw is removed <strong>and</strong> experimental plots are fertilized <strong>and</strong><br />
reflooded for evaluating ratoon crop potential.<br />
is combine-harvested, the grain must be reaped cleanly from the panicles <strong>and</strong> not<br />
remain attached to the rachis branches; otherwise, it may be lost out the back o f the<br />
combine witli the straw. Breeders will gently squeeze the ripened panicles on plants<br />
in the breeding nursery to see how eashy the grain comes off, to give an indication of<br />
shattering <strong>and</strong> threshability o f the genotype.
182 The <strong>Rice</strong> Plant<br />
Figure 2.4.3. Disease spreorier rows in an upl<strong>and</strong> blast nursery are overwhelmed by infection os cortipored t o ,<br />
some healthy breeding lines,<br />
Disease Resistance<br />
<strong>Rice</strong> Blast Disease<br />
<strong>Rice</strong> blast disease caused by Pyriculana grísea Sacc. is com monly found throughout<br />
the world wherever rice is grown. In U.S. rice-growing regions» yield losses due to blast<br />
are com m on hut generally not devastating as they are in some other countries. This is<br />
primarily due to winters that are cold enough to interrupt the pathogen life cycle» lack<br />
of continuous rice <strong>production</strong> as in some tropical areas o f the world (M archetti, 1994),<br />
<strong>and</strong> the presence o f relatively few (about 25) pathotypes (M archetti <strong>and</strong> Lai, 1998).<br />
Leaf blast symptoms are rarely seen in the field, but neck blast symptoms (rotten<br />
neck) are com m on. Presence o f the disease can result in losses in yield <strong>and</strong> milling<br />
quality. <strong>Rice</strong> blast com monly occurs each year in southern rice <strong>production</strong> areas, <strong>and</strong><br />
resistance is routinely selected for in inoculated tests. However, blast disease was not<br />
identified in the California rice-growing region until 1996 (Greer <strong>and</strong> Webster, 1997).<br />
Thus blast resistance had not been selected for, resulting in aU California cultivars being<br />
highly susceptible to most races. Although chemical control methods are available,<br />
these may be expensive, require field scouting to get the full benefit, <strong>and</strong> may have<br />
restricted use in certain regions o f the country. Utilizing naturally occurring disease-<br />
resistance genes will protect yield <strong>and</strong> milling quality o f cultivars <strong>and</strong> will reduce the<br />
need for fungicides which wfil lower producer input costs.<br />
Blast resistance is controlled by maj or genes, which each convey resistance to specific<br />
races o f blast, <strong>and</strong> minor genes, which slow the development o f disease regardless<br />
o f race. Breeders utilize both types o f resistance in their breeding programs. There<br />
is seldom enough disease pressure from Pyricularia grísea under field conditions to
Techniques for Development of New Cultivars 183<br />
allow breeders to select effectively. Thus, screening for resistance is usually conducted<br />
in inoculated trials under controlled conditions.<br />
M ajor gene resistance is determined by assessing the disease reaction of cultivars<br />
to individual races o f blast <strong>and</strong> comparing these to the reaction o f an established set<br />
o f international differentials (Atkins et al., 1967). This type o f screening is usually<br />
conducted under greenhouse conditions where individual pathotypes are used to<br />
inoculate genotypes using a dew chamber (M archetti et al., 1987). The races that are<br />
used are known to detect the presence o f specific m ajor genes <strong>and</strong> historically have<br />
produced consistent reactions under greenhouse conditions. Based on the cultivar’s<br />
reaction to a set o f races, the breeder can determine which m ajor genes are probably<br />
present, although some genes mask the presence o f other genes (Table 2.4,2),<br />
Another method that is used involves screening genotypes tliat have been planted<br />
in an upl<strong>and</strong> nursery (Figure 2.4.3) (M archetti, 1983, 1994; M archetti <strong>and</strong> Lai, 1986).<br />
A mixture of races is used to inoculate breeding lines <strong>and</strong> susceptible spreader rows,<br />
<strong>and</strong> overhead sprinklers ensure tliat leaves are wet which encourages infection. About<br />
30 days after planting, the genotypes are scored for susceptibility using a scale o f 0 to 9<br />
(IRRI, 1975). Known susceptible <strong>and</strong> resistant cultivars are included in the screening<br />
to verify the effectiveness o f the test. This method is not as laborious as screening<br />
against individual races <strong>and</strong> thus is the method diat breeders com monly use during<br />
early generations when there are large numbers o f progeny.<br />
These methods, coupled with weather conditions, cultural management techniques,<br />
<strong>and</strong> pathogen population dynamics, have effectively maintained control o f<br />
rice blast disease in the United States, in contrast to the "boom <strong>and</strong> bust” disease cycles<br />
that have been seen in some regions o f the world. Furthermore, U.S. cultivars such<br />
as Saturn (Jodon, 1965), Labelle (BoUich et al., 1973), Mars (Johnston et al., 1979),<br />
Newbonnet (Johnston et al., 1984), Lemont (BoUich et al., 1985), Gulfinont (Bollich<br />
et al., 1990), Cypress (Linscombe et al., 1993a), <strong>and</strong> Bengal (Linscombe et al., 1993b)<br />
remained as predominant cultivars for a decade or more after their release, being<br />
replaced primarily by higher-yielding cultivars, not more-disease-resistant ones. Various<br />
sources o f germplasm have been utilized over the years to build tliis base o f m ajor<br />
gene resistance. Although the cultivar Dawn (Bollich et al., 1968) was not grown on<br />
significant com mercial hectarage, it has served as the source o f the Pi-lé‘ gene, which<br />
is com m only found in southern U.S, long-grain cultivars. The Pi-lâ gene is believed to<br />
be an introgression from the cultivar Punjab (C I5309) that is in tlie lineage o f Dawn<br />
(M archetti, 1994). This gene is linked to the pi-d gene, which conveys resistance to<br />
TABLE 2.4,2. Resistant (R) or Susceptible [S] Reaction of Blast Resistance Genes to Specific<br />
Races of Pyrkvimia grisea<br />
Chrom osom al<br />
Location<br />
Com m on Races of fVrrriflor/o gr/sea Found in the United States<br />
IB 1 IB 54 IH 1 I G l IB 45 1C 17 l E I IE I K IB 49<br />
Pi-k!' 11 S R R R R S S S S<br />
11 s R S S S s S s s<br />
pi-d 11 R S S S S s s s s<br />
Pi-z 6 S S R R s R R R s<br />
Pi-ta^ 12 R R R R R R R s R
184 The <strong>Rice</strong> Plant<br />
one race o f blast found in the United States (M archetti et al, 1987). The Pi-k gene is<br />
allelelic to <strong>and</strong> was introduced into the United States in the cultivar Caloro, a<br />
selection from within a short-grain variety from Japan (M archetti, 1994). This gene<br />
conveys resistance to the IB -54 race <strong>and</strong> is one o f the few resistance genes that has been<br />
identified in some o f the California cultivars. The Pi-ta^ gene was introduced into U.S.<br />
germplasm from the Vietnamese cultivar Tetep, which was used in the development<br />
o f the Katy cultivar (Moldenhauer et a l, 1990), This single gene provides resistance to<br />
the broadest spectrum o f races o f blast that occur in the United States. The long-grain<br />
cultivar, Jefferson (M cClung et al., 1997) was the result o f a 20-year effort to stack<br />
the pi-d, Pi-k'', <strong>and</strong> Pi-z genes into one commercial cultivar, providing resistance to<br />
all but one m ajor race o f blast found in the United States. The Pi-z gene previously<br />
was found only in medium-grain cultivars <strong>and</strong> traces to the varieties, Zenith <strong>and</strong> Blue<br />
Rose. In 2001 the cultivar Saber was released as the first U.S. cultivar known to possess<br />
the Pi-b blast-resistance gene, which was introgressed from the Chinese cultivar, Te<br />
Qing. This gene is believed to convey resistance to IE-1, IE -IK , IC -17, IG -1, lB -1, <strong>and</strong><br />
perhaps other races. The spectrum o f races that each gene provides resistance to will<br />
be revealed only when, other masking genes are “unstacked” from the cultivar.<br />
Partial resistance which controls the rate o f disease development appears to be<br />
present in m ost southern U.S. germplasm. Southern cultivars such as Texm ont (Bollich<br />
et aL, 1993b), Rosemont (BoUich et al., 1993a), <strong>and</strong> Maybelle (Bollich et ah,<br />
1991), as well as m ost California cultivars, lack known m ajor resistance genes but<br />
the southern cultivars have significant partial resistance to blast (M archetti, 1994).<br />
Deployment o f cultivars possessing both race-specific <strong>and</strong> rate-reducing resistance<br />
genes to blast is an effective means o f disease control.<br />
Sheath Blight<br />
f-il. !<br />
Sheath blight disease caused by Rhizoctonia solani Kuhn is a com m on problem in<br />
most places where rice is grown <strong>and</strong> can cause significant yield losses. Worldwide, no<br />
complete resistance has been reported (Pan et a l, 1999) <strong>and</strong> thus chemical control<br />
is necessary. Similar to rice blast within the United States, weather conditions <strong>and</strong><br />
cultural management practices help to limit widespread losses in rice. Sclerotia from<br />
the organism can overwinter in the field <strong>and</strong> float on the surface o f the water in a<br />
flooded rice field. Infection occurs at the waterline on the plant <strong>and</strong> then spreads<br />
up the plant, eventually affecting grain <strong>production</strong>. Taller cultivars therefore generally<br />
have an advantage over semidwarf cultivars <strong>and</strong> escape significant yield losses<br />
(Marchetti, 1983b ). Although some fungicides are available that give excellent control,<br />
fields should be scouted, tlie application must be made at the right time, <strong>and</strong> the<br />
chemicals <strong>and</strong> aerial application can be costly. Therefore, development o f cultivars<br />
with improved tolerance to sheath blight would benefit producers. Te Qing <strong>and</strong> Gui<br />
Chow from China, Jasmine 85 from the Philippines, <strong>and</strong> CICA 6 <strong>and</strong> CICA 9 from<br />
Colombia are being used as sources o f resistance in U.S. research programs (Rush, et<br />
al., 1998; Pan et al., 1999), even though in their country o f <strong>origin</strong> they have not had<br />
high levels of resistance. Many U.S. medium-grain cultivars (i.e., japónicas) have better<br />
resistance to sheath blight than do long grains (i.e., javanicas). The medium-grain<br />
cultivars Vista (i.e., japónica) <strong>and</strong> Te Qing (indica from China) are in the respective<br />
lineages o f Jefferson <strong>and</strong> Saber <strong>and</strong> may be the reason for the modest improvement<br />
in sheath blight tolerance in these semidwarf cultivars (Table 2.4.3).
" W l<br />
Techniques for Development of New Cultivars 185<br />
TABLE 2.4.3.<br />
Comparison of Reaction to Sheath Blight (ff/trzocfon/o solani) Disease in<br />
Inoculated Field Plots Located at Beaumont, Texas‘S<br />
Gulfm ont<br />
Cypress<br />
M adison<br />
Kaybonnet<br />
Jefferson<br />
Saber<br />
Year<br />
Sem idw arf<br />
Sem idw arf<br />
Sem idw arf<br />
Tall<br />
Sem idw arf<br />
Sem idw arf<br />
1996 7 6 6 6 6 4<br />
1997 6 8 7 8 5 6<br />
1998 9 6 7 6 6 2<br />
1999 6 6 6 5 4 5<br />
2000 8 8 6 6 6 6<br />
Mean 7.2 6.8 6.4 6.2 5.4 4.6<br />
Min.-max. 6-9 6-8 6-7 5-8 4-6 2-6<br />
"Using a scale where 0 ~ immune to 9 = very susceptible.<br />
As with blast disease, the presence o f sheath blight does not occur frequently or<br />
uniformly enough to allow breeders to make effective selections outside inoculation<br />
nurseries. Thus each year, breeding lines are evaluated in flooded field plots that have<br />
been infested with sheath blight inoculum <strong>and</strong>, in some cases, sprinlder irrigation<br />
is used to increase the incidence o f disease (M archetti <strong>and</strong> BoUich, 1991; Pan et a l,<br />
1999). Ratings are made using a scale o f 0 to 9, with the higher number indicating<br />
greater susceptibility. Early-maturing cultivars may escape severe yield loss because<br />
grain development occurs faster than symptom development. Disease incidence <strong>and</strong><br />
yield loss estimates based on comparison o f inoculated <strong>and</strong> uninoculated yield plots<br />
can be helpful in identifying true resistance. (M archetti <strong>and</strong> BoUich, 1991). Another<br />
inoculation metliod using infected toothpicks has been developed that can be used<br />
to screen for sheath blight tolerance under growth chamber conditions <strong>and</strong> on single<br />
plants (Eizenga, Lee, <strong>and</strong> Rutger, accepted).<br />
Stem Rot<br />
Stem rot caused by Sclerotium oryzae Cattaneo is considered one o f the m ost serious<br />
diseases in rice <strong>production</strong> in California (McKenzie, et al., 1994). There are<br />
no fungicides registered for this disease in California, <strong>and</strong> burning o f rice stubble<br />
is a management practice that is being phased out. Screening methods have been<br />
developed (Oster, 1990) that have been effective in developing resistant germplasm<br />
(Oster, 1992, Tseng <strong>and</strong> Oster, 1994). Progress has been made in developing molecular<br />
markers for resistance using some o f this germplasm (MackiU et a l, 1998).<br />
Minor Diseases<br />
Narrow brown leaf spot caused by Cercospora janseana (Racib.) O. Const, is a disease<br />
that infects the leaves, sheaths, uppermost internodes <strong>and</strong> glumes o f rice. It has been<br />
considered a disease o f m inor importance because it usually occurs late in the season,<br />
after yield potential is established. However, research has shown that it can have a<br />
m ajor impact on milling quality (Castro et al. 1994) <strong>and</strong> thus may affect the yield<br />
potential o f the ratoon crop. Fungicides are available that give good control in <strong>production</strong><br />
fields, but these usually are not applied unless other yield-limiting diseases
The <strong>Rice</strong> Plont<br />
are present. Development o f effective screening methods for this disease have been<br />
limited; thus breeders usually make selections for resistance when the disease occurs<br />
naturally in the field. Sometimes this is best observed in late-planted nurseries or<br />
when nitrogen fertilizer is reduced.<br />
Panicle blight is described as grain abortion that occurs shortly after flowering.<br />
Glumes senesce prematurely, while panicle branches remain green <strong>and</strong> the panicle<br />
remains erect, with only a few partially filled grains (Figure 2.4.4) (M cClung et al.,<br />
1996b). Symptoms have been seen, although sporadic, most frequently along the Gulf<br />
Coast rice-growing region. In 1995 the symptoms were more widespread, <strong>and</strong> significant<br />
losses in yield <strong>and</strong> milling quality occurred. M cClung et al, ( 1996a) demonstrated<br />
that seed harvested from plots with symptoms had reduced grain weight <strong>and</strong> seedling<br />
vigor compared to plots without symptoms. Attempts to identify a causal organism<br />
had been unsuccessful, <strong>and</strong> it was considered a physiological problem associated with<br />
high nighttime temperatures (M cClung et al., 1996a) until 1998, when Shahjahan et<br />
al. isolated Burkholderia glumae from uninoculated plants that occurred in <strong>production</strong><br />
fields <strong>and</strong> found that similar symptoms were induced in plots when inoculated<br />
with this bacterial organism. Screening nurseries for resistance are now conducted<br />
using this bacterium.<br />
Straighthead is a physiological disorder that is not widespread but can result in<br />
significant yield <strong>and</strong> milling losses. The m ost characteristic symptoms are panicle<br />
blanking (lack o f grain development) <strong>and</strong> distortion o f the glumes, which is described<br />
as looking like a parrot beak (Br<strong>and</strong>on, 1992). These symptoms appear to occur most<br />
frequently in anaerobic soil conditions. Although draining the field prior to heading<br />
will allow aeration o f the soil <strong>and</strong> reduce symptoms, many producers do not have<br />
the flexibility to do this at such a critical time prior to grain development. No other<br />
control method is known other than to avoid planting highly susceptible cultivars m<br />
fields that have had a <strong>history</strong> o f this malady. A screening rnethod has been developed<br />
Figure 2.4.4.<br />
Erect panicles with aborted florets in plots having panicle blight symptoms,
fl<br />
Techniques for Development of New Cultivars 187<br />
using high levels o f arsenic incorporated in the soil before planting. Between heading<br />
<strong>and</strong> harvest, plots are evaluated for susceptibility using a scale o f 0 to 9 or based on<br />
yield loss (Gravois <strong>and</strong> Helms, 1996).<br />
Insect Resistance<br />
<strong>Rice</strong> research stations located in Biggs, California <strong>and</strong> Crowley, Louisiana have historically<br />
had high levels o f natural infestations o f rice water weevil (Lissorhoptus oryzophilus<br />
Kuschel) <strong>and</strong> have established screening nurseries. Plots are planted relatively<br />
late in the season <strong>and</strong> the fields are flooded early to encourage deposition o f eggs<br />
on the plants by the adults. Larvae will feed on the roots <strong>and</strong> stunt plant growth.<br />
Core samples o f soil are taken from the plots at Crowley <strong>and</strong> evaluated for number o f<br />
larvae present. Yield is determined on naturally infested plots <strong>and</strong> plots treated with<br />
an insecticide to measure the degree o f tolerance to feeding injury. Approximately 2<br />
m onths after planting at Biggs, plants are evaluated for vigor in response to feeding<br />
injury using a scale o f 1 to 9. PI 506230 (Tseng et al., 1987) was developed as an<br />
improved source o f resistance to rice water weevil that was derived from PI 162254, a<br />
cultivar from Korea.<br />
Tolerance to Environmental Stress<br />
Having an adequate num ber o f seedlings that emerge through the soil is fundamental<br />
to yield potential. It is recommended that fields with plant st<strong>and</strong>s o f fewer than 90<br />
to 100 plants per square meter should be replanted (Texas Agricultural Extension<br />
Service, 2001). Yield loss can be reduced by increased tillering in a poor st<strong>and</strong> o f<br />
plants where there is less plant-to-plant com petition <strong>and</strong> additional nitrogen fertilizer<br />
is applied. However, grain which develops on late-form ing tillers will not be at the<br />
same maturity as earlier tillers, <strong>and</strong> this may result in reduced milling yields at the<br />
time o f harvest.<br />
M ost conventional-height cultivars generally have excellent seedling vigor. However,<br />
widespread use of the sdl semidwarf gene has resulted in many o f tliese cultivars<br />
having poorer seedling vigor, due to a shortened mesocotyl (Turner et al. 1982). This,<br />
coupled with low temperatures at planting, can reduce st<strong>and</strong>s o f semidwarf cultivars<br />
(M cllrath, 1984). Results reported by Lai <strong>and</strong> M cClung (1998) in a study evaluating<br />
over 80 U.S. <strong>and</strong> foreign cultivars indicated that there are different mechanisms<br />
controlling vigor at the germination, emergence, <strong>and</strong> seedling stages. Breeders select<br />
for seedling vigor in various ways. Some drill seed tlieir nurseries early in the spring<br />
to maximize the opportunity for cool-temperature stress. Others evaluate seedling<br />
growth prior to spring planting using controlled-growth chambers <strong>and</strong> reduced tem <br />
peratures (Jones <strong>and</strong> Peterson, 1976). The breeding programs in California (M cKenzie<br />
et a l, 1994) <strong>and</strong> Louisiana evaluate seedling vigor following water seeding of<br />
pregerminated kernels in field plots. Redona <strong>and</strong> Macldll ( 1996a-c) identified genetic<br />
sources having high seedling vigor <strong>and</strong> molecular markers that could be used in<br />
breeding. Some o f the recent cultivars that have been released from tlie programs<br />
in California <strong>and</strong> Louisiana, such as Cypress (Linscombe et a l, 1993a), Cocodrie
The Ríce Plant<br />
{Linscombe et al., 2000), L-204 (Tseng et al,, 1997a), <strong>and</strong> L-205 (Tseng et al., 2001a),<br />
possess sdl <strong>and</strong> have excellent seedling vigor. Although seedling vigor is an im portant<br />
breeding criterion, horm onal seed treatments are available that can help producers<br />
overcome reduced seedling vigor in cultivars.<br />
Tolerance to Extremes in Temperatures<br />
Cold temperatures at flowering may occur in California <strong>and</strong> result in panicle blanking.<br />
The Biggs breeding program uses three locations <strong>and</strong> a winter nursery in Hawaii<br />
that have particularly cool temperatures to screen early-generation progeny for cold<br />
tolerance at flowering (McKenzie et al., 1994). Selecting for early-maturing cultivars<br />
has been an effective metliod for avoiding this environmentally induced problem<br />
(Rutger <strong>and</strong> Bollich, 1991). Cool temperatures at flowering can reduce the yield of<br />
the ratoon crop in the soutliern growing region (Bollich <strong>and</strong> Turner, 1988).<br />
Excessive heat during the tillering, flowering <strong>and</strong> grain-filling stage may effect<br />
yield potential <strong>and</strong> milling quality. Samonte et al. (2001) demonstrated that high<br />
total nonstructural carbohydrate concentrations (TNCs) at heading can serve as a<br />
resource for remobilization during grain filling. High temperatures during this stage<br />
may result in increased respiration rates <strong>and</strong> reduced TNC accumulation, which can<br />
lead to reduced yield potential. Selection for genotypes having high grain weight at<br />
hai'vest wfll result in greater remobilization o f stored TNC during grain filling.<br />
ReducGd Water Use<br />
<strong>Rice</strong> does not require flooded conditions for plant growth but is one o f the few crops<br />
that can thrive under such conditions. Producers use this as a nonchem ical means of<br />
weed control since many weed species cannot live under flooded conditions. Flooded<br />
rice fields also have m uch greater stability in yield <strong>production</strong> than does upl<strong>and</strong><br />
cropping. However, with increasing dem<strong>and</strong>s on water resources due to urban <strong>and</strong><br />
industrial expansion, there is increasing interest in developing cultivars that have high<br />
yield potential under upl<strong>and</strong> or reduced-water-use conditions. Upl<strong>and</strong> rice culture is<br />
not practiced in the United States, although it is widespread in other parts o f the<br />
world. These other countries may serve as a genetic resource for upl<strong>and</strong> germplasm<br />
that can be used in U.S. breeding programs.<br />
Selection for Components of <strong>Rice</strong> Quality<br />
I<br />
Cultivars developed in the United States have a reputation for high grain quality<br />
(Rutger <strong>and</strong> Bollich, 1991). This is because there has been a long-st<strong>and</strong>ing interaction<br />
between researchers <strong>and</strong> the U.S. rice industry, which has helped define grain<br />
dimension, milling, <strong>and</strong> cooking-quality st<strong>and</strong>ards. Accepted grain dimensions <strong>and</strong><br />
analytical measurements o f cooking quality for short-, medium-, <strong>and</strong> long-grain U.S.<br />
market classes have been presented by Webb (1980). Since 1955, U.S. breeding programs<br />
have been able to evaluate advanced breeding lines for key cooking-quality<br />
traits through interaction with the USDA-ARS <strong>Rice</strong> Quality Evaluation program at<br />
Beaumont, Texas. The integration o f rice cooking-quality assessment as part o f the<br />
breeding program is a concept that is. now used in many rice research programs<br />
around the world.
Techniques for Development of New Cultivars 189<br />
Am/lose, Protein, Alkali Spreading Value, <strong>and</strong> Amylograms<br />
Amylose content is the predominant factor in determining cooking <strong>and</strong> processing<br />
quality in rice (Juliano, 1985). St<strong>and</strong>ard methods for analysis o f amylose content<br />
include wet chemistry extraction (Juliano, 1971) followed by colorim etric determ i<br />
nation using a spectrophotometer (Webb, 1972). Near-infrared <strong>technology</strong> is also<br />
used as a predictor o f amylose (Delwiche et al., 1995) <strong>and</strong> protein contents. Alkali<br />
spreading value (ASV) is used as a predictor o f starch gelatinization temperature<br />
(Little et al., 1958). These two determinations— amylose content <strong>and</strong> ASV— together<br />
witli grain dimensions are generally adequate to assure that the cooking quality meets<br />
the st<strong>and</strong>ards for the U.S. market class (Table 2,4.4) (Webb, 1980).<br />
The starch paste viscosity profile is determined using a rapid-visco analyzer<br />
(RVA), which can differentiate cooking <strong>and</strong> utilization properties in rice (Blakney et<br />
al. 1991). This evaluation is useful in discriminating cultivars having superior parboilcanning<br />
stability. These cultivars have 2 to 3% higher amylose content <strong>and</strong> higher hot<strong>and</strong><br />
cool-paste amylographic viscosities than those o f conventional long grains, as well<br />
as reduced starch solids loss <strong>and</strong> better grain integrity following processing (Webb <strong>and</strong><br />
Adair, 1970). Thus the viscosity profile can distinguish between Dixiebelle (M cClung<br />
et al., 1998a), which has parboiLcanning stability, <strong>and</strong> L-202, (Tseng et al., 1984)<br />
which lacks this trait, although both have similar grain dimensions, amylose contents,<br />
<strong>and</strong> ASV. A com bination o f all o f these tests (amylose <strong>and</strong> protein contents, ASV, <strong>and</strong><br />
RVA) can be conducted on less than 20 g o f whole milled rice. Thus, hundreds o f<br />
midgeneration <strong>and</strong> more advanced breeding lines can be screened easily each year.<br />
Molecular Markers for Cooking Quality<br />
Recently, a microsatellite m olecular marker has been developed that can differentiate<br />
rice into various classes o f amylose content (Ayres et a l, 1997). This marker is associated<br />
with the granule-bound starch synthase gene {waxy)y which controls amylose<br />
<strong>production</strong> in the grain. The method has been modified so that large numbers o f<br />
breeding progeny can be evaluated in a very short period o f time (Bergman et al.<br />
2001), This microsatellite can also differentiate cultivars having parboil-canning stability<br />
which possess the (C T) lo or (C T)u allele from conventional long grains [(C T )2o<br />
allele]. However, it does not identify waxy cultivars (0% amylose), suggesting that<br />
other genetic factors are the cause o f this phenotype. The microsateUite marker associated<br />
with die waxy gene has been used to expedite the development o f two specialty<br />
TABLE 2.4.4. Apparent Amylose Content <strong>and</strong> Alkali Spreading Value of Conventional Market<br />
Classes of U.S. <strong>Rice</strong><br />
Apparent<br />
Amylose<br />
Content (%)<br />
Alkali Spreading Value<br />
Waxy<br />
I— Medium orshortgrainH<br />
Long grain -<br />
I— ^Supa-ior prooessing-longgrain—1
long-grain rice cultivars, Cadet <strong>and</strong> JacintOj that have low amylose contents (Bergman<br />
etal. 2001). Using marker-assisted selection, these cultivars were developed in Syears,<br />
compared to 10 years for most conventional breeding projects.<br />
Milling Quality<br />
Milling yield is as im portant as field yield in rice breeding because it largely determines<br />
the market value o f the rough rice. Fluctuations in environmental factors such as<br />
relative humidity <strong>and</strong> temperature prior to harvest <strong>and</strong> during postharvest h<strong>and</strong>ling<br />
can affect milling quality (Jodari <strong>and</strong> Linscombe, 1996). Cultural management m ethods,<br />
disease <strong>and</strong> insect pressure, <strong>and</strong> choice o f cultivar also influence milling yield.<br />
To determine milling quality, rough (paddy) rice is dehulled to produce brown rice.<br />
The brown rice is milled to produce white milled rice, followed by separation into<br />
whole milled <strong>and</strong> broken kernels. The proportion o f whole milled kernels derived<br />
from paddy rice is considered head rice or whole milling yield. A method for determining<br />
milling yield that uses only 125 g o f rough rice typically is used by breeding<br />
programs (Webb, 1980). However, a modification o f this method tliat uses only 50 g<br />
o f paddy rice has been developed which allows milling quality to be determined in<br />
earlier breeding generations when seed quantities are limited (M cClung <strong>and</strong> Castro,<br />
1994).<br />
Most breeding programs will evaluate milling quality o f breeding selections starting<br />
at the F.1or F5 generation, when quantities o f seed are less limitmg. Johnson (1994)<br />
reported evaluating all advanced-yield trial selections for milling yield response to<br />
declining harvest moisture. Samples are harvested at three different moisture levels to<br />
simulate the range in harvest moistures that m aybe found in com mercial <strong>production</strong><br />
fields. Methods have been developed to determine fissure resistance in rice under<br />
controlled conditions as a predictor o f milling yield stability <strong>and</strong> determ ination of optimum<br />
harvest moisture for various cultivars (Jodari <strong>and</strong> Linscombe, 1996). Ratoon<br />
crop milling quality is generally m uch lower than that o f the main crop, due to wide<br />
fluctuations in weather conditions in the fall (Bollich <strong>and</strong> Turner, 1988). Breeders<br />
generally do not determine the milling quality o f the ratoon crop since it is so variable.<br />
Grain Appearance<br />
Breeders evaluate thous<strong>and</strong>s o f genetic lines each year for grain appearance. This<br />
is first done in the field by looking at the grain shape o f the rough rice. Panicle or<br />
bulked row selections that are harvested are evaluated as brown or milled rice. At<br />
this stage of the breeding process, seed quantities are very limited <strong>and</strong> it is difficult<br />
to have enough rice to mil! <strong>and</strong> still have seed to plant in advanced trials. For this<br />
reason, a test-tube mill was developed that allows the breeder to evaluate about 1 g of<br />
milled rice (Scott et al. 1964). Some programs will forgo the milling process during<br />
early generations <strong>and</strong> observe only a few kernels o f brown rice dehulled from every<br />
panicle harvested (McKenzie et al., 1994). These methods allow the breeder to better<br />
observe grain shape, grain uniformity, fissuring, chalkiness, color, <strong>and</strong> translucency<br />
Chalkiness, which may occur around the edge o f the kernel or near the center, can<br />
reduce milling yields by weakening the grain (Webb, 1980). It is easier to observe<br />
chalk using a baddighted surface. The presence of grooves in the brown rice or other<br />
distortions in shape may indicate that deep milling will be required to remove all the
Techniques for Development of New Cultivars 191<br />
bran <strong>and</strong> will result in lower milling yields. Instruments are available that objectively<br />
measure the degree o f whiteness o f the grain, which is considered a desirable trait.<br />
However, these measurements will be artificially high if chalky grains are present.<br />
Spscialt/ <strong>Rice</strong>s<br />
Specialty rices have unique properties <strong>and</strong> usually have a higher value in niche markets.<br />
These markets are generally small in volume, but because they are frequently<br />
are grown under contract <strong>production</strong> <strong>and</strong> carry a price premium, the entire market<br />
stream including producer, miller, <strong>and</strong> processor can benefit. Although specialty cultivars<br />
may not be widely grown, breeders try to develop cultivars that m eet the needs<br />
o f these markets. However, inform ation on the specific traits that are desired for these<br />
niche markets is often limited or inconsistent.<br />
Aromatic rice cultivars have a popcorn or nutty scent, due to the presence o f<br />
high levels of 2-acetyl-1-pyrroline, which is produced throughout the plant (Buttery<br />
et al,, 1983, 1986). This is one o f the most im portant sensory traits which distinguishes<br />
basmati <strong>and</strong> Thai jasm ine from conventional rices. Both o f these rices are<br />
imported into the United States, <strong>and</strong> breeders would like to develop cultivars having<br />
these same traits which could be produced domestically. Previously, breeders selected<br />
for tlie presence or absence o f aroma by soaking a small am ount o f leaf tissue or<br />
grain in potassium hydroxide solution (Sood <strong>and</strong> Siddiq, 1978). However, more accurate<br />
methods o f quantification have since been developed tliat require only small<br />
amounts o f sample (Bergm an et ah, 2000; Grim m et al., 2001). Della (Jodon <strong>and</strong><br />
Sonnier, 1973), DeUmont (Bollich et al., 1993c), <strong>and</strong> Deliróse (fodari et ah, 1996)<br />
are examples o f aromatic long-grain cultivars that have been developed in the United<br />
States which have conventional long-grain quality <strong>and</strong> cook dry <strong>and</strong> flalcy. Although<br />
most sources o f aroma used in U.S. breeding programs possess the same single gene<br />
for 2-acetyI- 1-pyrroline, an additional gene has been reported in Amber <strong>and</strong> Dragon<br />
Eyeball 100 cultivars that could be used to enhance this trait (Pinson, 1994). Jasmine<br />
85 (M archetti et ah, 1998) was developed to compete with Thai jasmine, which is<br />
imported in quantities equivalent to over 400,000 m etric tons o f milled rice each<br />
year. Jasmine 85 is an aromatic long grain that cooks soft <strong>and</strong> sticlcy, lilce its imported<br />
counterpart. However, Rister et al. (1992) determined that imported Thai jasm ine<br />
was preferred to Jasmine 85 in Asian-American households, indicating that aroma<br />
<strong>and</strong> cooking quality were not the only traits o f importance for tliis niche market.<br />
Basmati-type rices are another specialty rice that com m<strong>and</strong> a premium m arket<br />
price <strong>and</strong> are im ported into the United States. Basm ati-370, which is grown in<br />
India <strong>and</strong> Pakistan, has been characterized as having 20 to 25% amylose content,<br />
intermediate-low ASV, aroma, long-grain shape, <strong>and</strong> cooked kernel elongation (Jo-<br />
dari <strong>and</strong> Linscombe, 1996), Cooked kernel elongation is determined by tlie ratio of<br />
grain length of the cooked grain versus the dry grain. Cultivars with this trait elongate<br />
almost twice as m uch as do conventional rices when cooked. U.S. breeders have<br />
developed basm ati-type rices such as A-201 (Tseng etal., 1997b), Calmati-201 (Tseng<br />
et ah, 2001b), <strong>and</strong> Dellmati (R U 9502171) (Jodari <strong>and</strong> Linscombe, 1998) but have had<br />
limited success in effectively competing with imports.<br />
There are U.S. breeding programs focused on developing cultivars for other specialty<br />
markets, including tlie Japanese premium -quality market (e.g., Koshihikari),<br />
waxy (sweet) rice that is used as a dessert (Rutger et al., 1998), <strong>and</strong> arborio rice,
192 The Rite Plont<br />
which is used in the Italian dish risotto. The cultivar M -401 (Carnahan et al., 1981),<br />
is an example o f a U.S. cultivar that has been developed for the Japanese premium-<br />
quality market. The cooked rice does not retrograde when cooled <strong>and</strong> has a very glossy<br />
appearance <strong>and</strong> sticky smooth texture (Rutger et ah, 1998).<br />
Molecular markers (RFLPs) have been identified on chromosome 8 that correspond<br />
to genes for aroma (Ahn et a l, 1992) <strong>and</strong> cooked kernel elongation in a cross<br />
using U.S. germplasm (Ahn et al., 1993). Sequence tag sites near the fragrance gene<br />
on chromosom e 8 have been reported by Garl<strong>and</strong> et al. (2000). Similarly, researchers<br />
at the USDA-ARS <strong>Rice</strong> Research Unit, Beaum ont Texas, have recently identified m i<br />
crosatellite markers near the genomic regions associated with aroma <strong>and</strong> elongation.<br />
Having PCR-based markers will facilitate marker-assisted selection programs in large<br />
breeding populations for these two traits. Bio<strong>technology</strong> should increase the effectiveness<br />
o f selection for these traits because they can be performed on individual plants<br />
using seedling leaf tissue <strong>and</strong> unlilce phenotypic traits, the markers are not subject to<br />
environmental variability.<br />
DEVELOPING GENETIC VARIABILITY<br />
I<br />
Most public rice breeding programs have relied on U.S. germplasm to generate genetic<br />
variability (Dilday, 1990). The primary reason for this is that attempts to introgress<br />
other world germplasm have resulted in difficulties in recovering tlie grain quality that<br />
is dem<strong>and</strong>ed in the U.S. market. A recent study comparing some o f the m ost recent<br />
southern U.S. cultivars with in^ica varieties that are well adapted to the same region<br />
demonstrated that U.S. cultivars have superior lodging resistance <strong>and</strong> m illing quality,<br />
whereas indica cultivars can be a resource for high tillering capacity <strong>and</strong> yield potential<br />
(McClung et al., 1998b). Cultivars from other countries have been used successfully<br />
in U.S. breeding programs for the improvement of seedling vigor, semidwarfism, cold<br />
tolerance, processing, quality, disease resistance, <strong>and</strong> insect resistance (Rutger <strong>and</strong><br />
Bollich, 1991). Private rice research programs have also used introduced materials<br />
for developing hybrid rice, brewing rice, <strong>and</strong> specialty rices.<br />
Other researchers have explored using other species for sources o f genetic variability<br />
for stem rot resistance (Tseng <strong>and</strong> Oster, 1994) <strong>and</strong> sheath blight resistance<br />
(Rush et al., 1998; Eizenga et al., accepted); as well as for improvements in height,<br />
yield, maturity, <strong>and</strong> blast resistance (M cCouch et al., 2001). Som aclonal variation has<br />
been repor ted to be an effective means o f generating useful genetic variability in rice<br />
(Xie et al., 1992).<br />
BREEDING METHODS<br />
Most U.S. breeding programs use pedigree, modified bulk, or backcross breeding<br />
schemes. Moldenhauer <strong>and</strong> Lee (1994) have reported using a modified recurrent<br />
selection program for developing cultivars having improved sheath blight tolerance<br />
<strong>and</strong> were successful in developing the cultivar Ahrent using this method. Anther<br />
culture <strong>technology</strong> was used to develop the U.S. rice cultivar Texm ont (Bollich et<br />
al., 1993b). The cultivar was grown on limited hectarage for several years before it<br />
was replaced by cultivars having better blast resistance. Although antlier culture has
Techniques for Deveiopment of New Cultivnrs 193<br />
continued to be used in the rice breeding programs in Texas, Arkansas, <strong>and</strong> Louisiana,<br />
it became less emphasized when molecular genetic <strong>technology</strong> became more widely<br />
employed. Recently, however, there has been renewed interest in using anther culture<br />
as a result o f optim ization o f culture media <strong>and</strong> the use of bridging parents that have<br />
high regenerability (Chu et al., 2000). The program in Louisiana is now capable o f<br />
generating some 8000 double haploid plants each year. Even with intensive selection,<br />
hundreds o f new homozygous lines are available for advanced yield trial testing.<br />
Breeders will malce hundreds o f crosses annually, using field or greenhouse facilities<br />
throughout the year. Plants chosen as females are emasculated using vacuum<br />
suction, <strong>and</strong> any florets that have shed pollen are removed. The female panicle is<br />
placed adjacent to plants that will serve as a pollen source, <strong>and</strong> then panicles are<br />
covered with a glassine bag to prevent contam ination from stray pollen. <strong>Rice</strong> plants<br />
can tolerate a lot o f manipulation in crossing. In some cases, tillers are cut from<br />
plants in the field, placed in water, <strong>and</strong> transported to the lab or greenhouse for use<br />
in crossing. Males <strong>and</strong> emasculated panicles (females) are paired according to the<br />
crossing plan <strong>and</strong> placed in water in a shalcer box (Figure 2.4.5). The shaker box has a<br />
small vibrating m otor that facilitates transfer o f pollen to the detached female tillers.<br />
After 3 to 5 days the hybrid seed can be seen developing. The rice breeding program<br />
at B eaumont, Texas uses molecular markers to verify heterozygosity o f F/s <strong>and</strong> to cull<br />
out inadvertent seifs.<br />
M ost public breeding programs also have access to winter nursery facilities. The<br />
California program uses a winter nursery in Hawaii to advance early generation m a<br />
terials, select for cold tolerance, <strong>and</strong> increase seed for summer yield testing. Breeding<br />
<strong>and</strong> genetics programs located in Mississippi, Arkansas, Louisiana <strong>and</strong> Texas use a<br />
winter nursery in Puerto Rico for early generation advance, seed increases for yield<br />
figure 2.4.5.<br />
Ponicles used in crosses ore placed under glossine bags in o water-filled shobr box.
trials, <strong>and</strong> initiation o f headrow purification programs. The Louisiana <strong>and</strong> Texas<br />
programs are able to harvest their summer nurseries early enough that two t<strong>and</strong>em<br />
nurseries can be planted during the winter in Puerto Rico.<br />
Breeding nurseries are conducted on site at each breeding station <strong>and</strong> may include<br />
20,000 to 60,000 progeny rows, representing several hundred crosses. The following<br />
is an example o f a typical rice breeding program; however, cultivar improvement<br />
programs are as diverse as plant breeders. In addition to program goals <strong>and</strong> m ethods<br />
which are modified to meet the needs o f the state, individual projects within a<br />
breeding program may be modified in a multitude of ways that will best accomplish<br />
the objectives of the cross.<br />
Seed o f the P2 generation are produced on Fi plants that are grown in greenhouses<br />
or have been transplanted to field nurseries. F2 progeny are space planted so<br />
that individual plants can be viewed <strong>and</strong> selected. Seed is harvested from selected<br />
plants <strong>and</strong> planted as an F3 bulk across one or more rows. This provides the first<br />
opportunity to view the progeny as a family. At these early generation stages, breeders<br />
will make general observations on plant architecture (erect versus prostrate leaves <strong>and</strong><br />
tillers), height, grain shape, <strong>and</strong> tillering ability in reference to parental or commercial<br />
checks. Notes will be made on any other pertinent traits (disease, lodging, panicle<br />
sterility, etc.) when the opportunity occurs. Days to heading is recorded <strong>and</strong> is used<br />
for grouping by maturity for field tests that follow. Panicles will be selected <strong>and</strong> singlerow<br />
bulks will be harvested from the m ost promising families. Seed from panicles or<br />
bulks will be evaluated m ore closely for grain characteristics using brown or milled<br />
rice. Usually, the first yield tests will be performed at the P5 or Fe level. These are<br />
probably unreplicated plots, due to limited amounts o f seed. The same seeding rate is<br />
used for aU lines <strong>and</strong> progeny having similar m aturity are tested in the same flooded<br />
field to facilitate timing o f cultural management practices (e.g., split applications of<br />
fertilizer, draining o f fields prior to harvest maturity, etc.). As noted above, water-<br />
seeded trials are conducted at Biggs (nursery <strong>and</strong> yield trials) <strong>and</strong> Crowley (yield<br />
trials). At this testing stage, yield, height, days to heading <strong>and</strong> maturity, milling yield,<br />
grain appearance, amylose content, ASV, plant architecture, seedling vigor, <strong>and</strong> blast<br />
nursery evaluations are recorded. In the Beaumont, Texas program, there are usually<br />
600 to 800 genotypes tested in this fashion each year, with about 2 0% being advanced<br />
to the next level o f testing. Following this unreplicated yield test, there is enough seed<br />
to conduct replicated tests at one or m ore locations in the following year, along with<br />
other disease <strong>and</strong> pest screening nurseries. Following statewide tests, the best entries<br />
are placed in the multistate yield trial that is conducted by each o f the cooperating<br />
southern states (Texas, Arkansas, Louisiana, Mississippi, <strong>and</strong> M issouri). The same<br />
parameters as noted above are measured in addition to reaction to individual races<br />
o f blast, screening nurseries for straighthead, panicle blight, <strong>and</strong> rice water weevil,<br />
<strong>and</strong> evaluations for minor diseases <strong>and</strong> pest damage to the grain. Some o f these<br />
evaluations are made at multiple locations <strong>and</strong> some at single localities (e.g., rice<br />
water weevil tests at Crowley <strong>and</strong> cool-tem perature seedling vigor tests at Biggs).<br />
Some breeders will use cultural management practices that are recommended for<br />
maximizing yield potential. Others prefer to utilize every opportunity to screen for
Techniques for Development of New Cultivars 195<br />
susceptibility to pest pressures <strong>and</strong> do not use any fungicides or insecticides. Entries<br />
generally remain in the multistate Uniform <strong>Rice</strong> Regional Nursery for up to 4 years<br />
before they are released as a cultivar. Usually, concurrent with the multistate tests,<br />
additional field trials within the breeder’s own state are conducted with their m ost<br />
advanced entries. Once a breeder has identified a c<strong>and</strong>idate for potential release <strong>and</strong><br />
seed is available, cooperators will include this entry in exp<strong>and</strong>ed field trials, screenings<br />
for other diseases, or testing for response to cultural management practices. Thus,<br />
at the tim e of release, there may be well over 40 environments (e.g., year-locations)<br />
where the cultivar has been tested. Each year the public rice breeders meet to discuss<br />
the results o f the regional trial, coordinate plans for future trials, present data on new<br />
releases, <strong>and</strong> discuss other research findings <strong>and</strong> trends in the industry.<br />
M ost yield trials are harvested by small plot combines, some o f which have autom<br />
atic weigh scales <strong>and</strong> moisture meters. Even though entries in a trial are grouped<br />
according to maturity, there may be a 5 to 7 day difference in maturity within a trial.<br />
Breeders will harvest a small section o f each plot by h<strong>and</strong> at 18 to 22% moisture for<br />
determining milling yield. Once all the plots have been sampled for milling quality,<br />
they are machine harvested for yield. In states where ratoon potential is im portant,<br />
only the most advanced trials will be evaluated for ratoon yield after the m ain crop is<br />
harvested. At some point in the latter stages o f the breeding project, the cultivars will<br />
be evaluated for milling yield response to declining harvest moisture. Milling yield<br />
samples are harvested three o r m ore times in a 10-day period to determine milling<br />
yield between 25% <strong>and</strong> 12% harvest moisture. Response curves are compared witli<br />
those o f commercial cultivars that are in the same test. St<strong>and</strong>ard experimental designs<br />
<strong>and</strong> statistical analyses are performed once all the field data aré collected. Breeders<br />
generally look to identify lines that have relatively high stable performance across<br />
environments.<br />
Usually, in parallel to the yield testing program, panicle selections are being<br />
advanced <strong>and</strong> purified for each entry that is in a yield trial. Thus several thous<strong>and</strong><br />
rows in the breeding nursery may be occupied by these selections, which are being<br />
advanced for pure seed increases. To ensure that the cultivar is highly homogeneous,<br />
one or more years o f headrow purification will be implemented prior to its release.<br />
Several hundred panicles o f tire cultivar are planted as rows in a separate block <strong>and</strong> any<br />
observed variation is removed. Once the cultivar appears to be stable <strong>and</strong> uniform, the<br />
bulk-harvested seed, called headrow seed, is used to produce Breeder seed as part o f the<br />
state seed certification process. Breeder seed is provided to cooperating foundation<br />
seed programs <strong>and</strong> is used to produce the Foundation, Registered, <strong>and</strong> Certified seed<br />
classes.<br />
EXPECTATIONS FOR THE FUTURE<br />
One o f the main differences between current U.S. rice breeding programs <strong>and</strong> those<br />
established some 70 years ago is the size <strong>and</strong> scope o f the cultivar improvement<br />
programs. Advances in mechanization <strong>and</strong> use o f computers have allowed breeding<br />
programs to exp<strong>and</strong> the num ber o f progeny evaluated <strong>and</strong> the number o f sites tested.<br />
In just the last 10 years, computer <strong>technology</strong> has revolutionized the amount of data<br />
that can be collected <strong>and</strong> the speed at which it can be analyzed. Previously, every<br />
row tag, plot stake, harvest bag, field book, pedigree designation, <strong>and</strong> data point was
196 The <strong>Rice</strong> Plant<br />
recorded by h<strong>and</strong>. Now m uch of this is done with small computers that can be taken<br />
into the field <strong>and</strong> from which data can be transferred to co-workers at other sites via<br />
e-mail.<br />
There has been an evolution in the scope o f breeding objectives covered by all<br />
breeding programs. Breeders are addressing conventional long-, medium-, <strong>and</strong> short-<br />
grain markets as well as those for specialty rices in an effort to keep the U.S. rice industry<br />
competitive in the exp<strong>and</strong>ing global market. Furthermore, breeders endeavor to<br />
incorporate diverse germplasms <strong>and</strong> technologies (e.g., anther culture, somaclones,<br />
transgenics, <strong>and</strong> molecular biology) into their programs. Even though many o f these<br />
technologies have been around for over a decade, their impact on conventional breeding<br />
has been limited. Clearly, the only way that these disciplines will make an impact<br />
on breeding will be if they are fully integrated into cultivar development programs<br />
<strong>and</strong> share the same objectives. Breeding has always been an interdisciplinary effort<br />
involving agronomists, geneticists, pathologists, <strong>and</strong> entomologists. Now, cultivar<br />
improvement teams include molecular geneticists, physiologists, <strong>and</strong> chemists as well<br />
as people skilled in bioinform atics <strong>and</strong> computer <strong>technology</strong>.<br />
The tremendous amount of inform ation that is starting to stream out o f the<br />
International <strong>Rice</strong> Genome Sequencing Proj ect demonstrates that we are on the brink<br />
of a new era in rice breeding. Many more years o f work will be needed to utilize this<br />
information in a meaningful way, but it will change conventional breeding. Clearly,<br />
the next big effort will be expended on tying genomic inform ation together with gene<br />
function. Essentially all the data being collected in m ost gene sequencing projects use<br />
germplasm that is unadapted to U.S. rice <strong>production</strong> areas. Only through concerted<br />
efforts by researchers working with U.S. germplasm under U.S. field conditions will<br />
this information truly have an impact on domestic agriculture.<br />
<strong>Rice</strong> is considered a model system from which functional genomic information<br />
will be extended to other, more complex crops. In addition, there is a great opportunity<br />
for exp<strong>and</strong>ing our underst<strong>and</strong>ing o f genetic interactions <strong>and</strong> the influence of<br />
the environment on im portant rice traits. Hopefully, molecular breeding will become<br />
commonplace within this next decade <strong>and</strong> there wiU be an exp<strong>and</strong>ed effort to use this<br />
<strong>technology</strong> to develop new markets <strong>and</strong> uses o f rice.<br />
REFERENCES<br />
Ahn, S. N., C. N. Bollich, <strong>and</strong> S. D. Tanksley. 1992. RPLP tagging o f a gene for aroma<br />
in rice. Theor. Appi Genet. 84:825-828.<br />
Ahn, S. N., C. N. Bollich, A. M. McClung, <strong>and</strong> S. D. Tanksley. 1993. RFLP analysis of<br />
genomic regions associated with cooked-kernel elongation in rice. Theor. Appl<br />
Genet. 87:27-32.<br />
Atkins, J. G ., A. L. Robert, C. R. Adair, K. Goto, X Kozaka, R. Yamagida, M. Yamada,<br />
<strong>and</strong> S. M atsumoto. 1967. An international set of varieties for differentiating races<br />
of Pyricularia oryzae. Phytopathology 57:297-301.<br />
Ayres, N. M ., A. M. McClung, P. D. Larkin, H, F. J. Bigh, C. A. Jones, <strong>and</strong> W. D.<br />
Park. 1997. Microsatellites <strong>and</strong> a single-nulceotide polymorphism differentiate<br />
apparent amylose classes in an extended pedigree o f U.S. rice germplasm. Theor.<br />
Appl Genet. 94:773-781.
Techniques for Development of New Cultivars 197<br />
Bergman, C., J. Delgado, R. Bryant, C. Grimm, K. Cadwallader, <strong>and</strong> B. Webb. 2000.<br />
A rapid gas chromatographic technique for quantifying 2"acetyl-l-'pyrroline <strong>and</strong><br />
hexanal in rice. Cereal Chem. 77:454-458.<br />
Bergman, C. J., J. T. Delgado, A. M . McClung, <strong>and</strong> R. G Fjellstrom. 2001. An improved<br />
method for using a microsatellite in the rice waxy gene to determine amylose<br />
class. Cereal Chem. 78: 257-260,<br />
Blakney, A. B., L. A. Welsh, <strong>and</strong> D. R. Bannon. 1991. <strong>Rice</strong> quality analysis using<br />
a computer controlled RVA. In D, J. M artin <strong>and</strong> C. W. Wrigley (eds.). Cereals<br />
International. Royal Australian Chemistry Institute, M elbourne, Australia, pp.<br />
108-182.<br />
Bollich, C. N., <strong>and</strong> F. T. Turner. 1988. Commercial ratoon rice <strong>production</strong> in Texas,<br />
USA. In <strong>Rice</strong> Ratooning. International <strong>Rice</strong> Research Institute, Manila, The Philippines,<br />
pp. 257-263.<br />
Bollich, C. N., J. G. Atkins, J. E. Scott, <strong>and</strong> B. D. Webb. 1968. Registration o f Dawn<br />
rice. Crop Sei 8:400.<br />
Bollich, C. N„ J. G. Atkins, J. E. Scott, <strong>and</strong> B. D. Webb. 1973. Registration o f Tabelle<br />
rice. Crop Sei 13:773-774.<br />
Bollich, C. N., B. D. Webb, M . A. M archetti, <strong>and</strong> J. E. Scott. 1983. Bellemont rice. Crop<br />
Sei 23:803-804.<br />
Bollich, C. N., B. D. Webb, M. A. Marchetti, <strong>and</strong> J. E. Scott. 1985. Registration o f<br />
'L em onf rice. Crop Sei 25:883-885.<br />
Bollich, C. N., B, D. Webb, <strong>and</strong> J. E. Scott. 1988. Breeding <strong>and</strong> testing for superior<br />
ratooning ability in rice. In <strong>Rice</strong> Ratooning. International <strong>Rice</strong> Research Institute,<br />
Manila, The Philippines, pp. 47-5 3 .<br />
Bollich, C. N., B. D. Webb, M. A. Marchetti, <strong>and</strong> J. E. Scott. 1990. Registration o f<br />
‘G ulfm onf rice. Crop Sei 30:1159-1160.<br />
Bollich, C. N., B. D. Webb, M. A. M archetti, <strong>and</strong> J. E. Scott. 1991. Registration o f<br />
‘Maybelle’ rice. Crop Sei 31:1090.<br />
Bollich, C. N„ B. D. Webb, M. A. M archetti, <strong>and</strong> J. E. Scott. 1993a. Registration o f<br />
‘Rosem onf rice. Crop Sei 33:877.<br />
Bollich, C. N., C. W. MagiU, A. B. Livore, H. H, Hung, B. D. Webb, M. A. M archetti,<br />
<strong>and</strong> J. E. Scott. 1993b. Registration o f'T exm o n f rice. Crop Sei 33:354.<br />
BoUich, C. N., H. H. Flung, B. D. Webb, M. A. Marchetti, <strong>and</strong> J. E. Scott. 1993c.<br />
Registration o f'D ellm o n f rice. Crop Sei 33:1410-1411.<br />
Bollich, C. N., B. R. Jackson, M , A. M archetti, J. E. Scott, <strong>and</strong> B. D. Webb. 1996.<br />
Registration o f ‘Jackson’ rice. Crop Sei 36:1412.<br />
Br<strong>and</strong>on, D. M. 1992. Straighthead. In R. K. Webster <strong>and</strong> P. S. Grunnell (eds.), Compendium<br />
of <strong>Rice</strong> Diseases. American Phytopathological Society, St, Paul, M N,<br />
p. 52.<br />
Buttery, R. G., L. C. Ling, B. O. Juliano, <strong>and</strong> J. G. Turnbaugh. 1983. Cooked rice aroma<br />
<strong>and</strong> 2-acetyH -pyrroline. /. Agrie. Food Chem. 31:823-826.<br />
Buttery, R. G., L. C. Ling, <strong>and</strong> T. R. Mon. 1986. Quantitative analysis o f 2-acetyl-1-<br />
pyiToline in rice. /. Agrie. Food Chem. 34:112-114.<br />
Carnahan, H. L., C. W. Johnson, S. T. Tseng, <strong>and</strong> D, M . Br<strong>and</strong>on, 1981. Registration<br />
o f ‘M -40T rice. Crap Sei 21:986-987.<br />
Castro, E. M., A. M. McClung, <strong>and</strong> M. A. Marchetti. 1994. Impact o f narrow brown<br />
leaf spot on harvest moisture <strong>and</strong> Assuring in rice. In Proceedings of the 25th
198 The <strong>Rice</strong> Plañí<br />
. !<br />
<strong>Rice</strong> Technical Working Group, New Orleans, LA, Mar. 5 -9 . Texas Agricultural<br />
Experiment Station, Texas A&M University System, College Station, T X , p. 102.<br />
Chu, Q. R., S. D. Linscombe, <strong>and</strong> H. X . Cao. 2000. <strong>Rice</strong> arither culture breeding<br />
strategy to develop elite southern U.S. long-grain lines. In Proceedings of the<br />
28th <strong>Rice</strong> Technical Working Group, Biloxi, MS, Feb. 27-M ar. 1. Louisiana State<br />
University Agricultural Center. Louisiana Agricultural Experim ent Station, <strong>Rice</strong><br />
Research Station, Crowley, LA, p. 47.<br />
Delwiche, S. R., M. M. Bean, R. E. Miller, B. D. Webb, <strong>and</strong> P. C. Williams. 1995.<br />
Apparent amylose content o f milled rice by near-infrared reflectance spectrophotometry.<br />
Cereal Chem. 72:182-187.<br />
Dilday, R.H. 1990. Contribution o f ancestral lines in the development o f new cultivars<br />
o f rice. Crop Science 30:905-911.<br />
Eizenga, G. C., E N. Lee, <strong>and</strong> J. N. Rutger. Accepted. Screening plants o f Oryza species<br />
for rice sheath blight resistance. Plant Dis.<br />
Garl<strong>and</strong>, S., L. Lewin, A. Blakney, R. Rienke, <strong>and</strong> R. Henry. 2000. PCR-based m olecular<br />
markers for the fragrance gene in rice {Oryza sativa L.). Theor. Appl Genet.<br />
101: 364-371.<br />
Gravois, K. A., <strong>and</strong>R. S. Helms. 1996. Assessing grain yield <strong>and</strong> head rice losses in rice<br />
due to straighthead. In Proceedings of the 26th <strong>Rice</strong> Technical Working Group, San<br />
Antonio, Texas, Feb. 25-28. Texas Agricultural Experiment Station, Texas A&M<br />
University System, College Station, TX , p. 133.<br />
Gravois, K. A., K. A. K. Moldenhauer, E N. Lee, R. J. Norman, R. S. Helms, <strong>and</strong> J. L.<br />
Bernhardt. 1995. Registration of'K aybonnef rice. Crop Sd. 35:586-587.<br />
Greer, C. A., <strong>and</strong> R. K. Webster^ 1997. First report o f rice blast caused by Pyricularia<br />
grísea in California. Plant Dis. 81.T094.<br />
Grimm, C. C., C. Bergman, J. T. Delgado, <strong>and</strong> R. Bryant. 2001. Screening for 2-acetyl-<br />
1-pyrroline in the headspace o f rice using SPME/GC-MS. /, Agrie. Pood Chem.<br />
49:245-249.<br />
IRRI. 1975. St<strong>and</strong>ard Evaluation System for <strong>Rice</strong>. International <strong>Rice</strong> Research Institute,<br />
Manila, The Philippines, 64 pp.<br />
Jodari, E , <strong>and</strong> S. D. Linscombe. 1996. Grain Assuring <strong>and</strong> milling yields o f rice cultivars<br />
as influenced by environmental conditions. Crop Sei. 36:1496-1502.<br />
Jodari, R, <strong>and</strong> S. D. Linscombe. 1998. Effects o f N rate <strong>and</strong> aging on cooked grain<br />
elongation of a basm ati-type rice selection. In Proceedings of the 27th <strong>Rice</strong> Technical<br />
Working Group. Reno, NV, Mar. 1 -4. Texas Agricultural Experim ent Station,<br />
Texas A&M University System, College Station, TX , p. 89.<br />
Jodari, R, S, D. Linscombe, P. K. BoUich, K. Bett, D, E. Groth, L. M. White, <strong>and</strong> R. T.<br />
Dun<strong>and</strong>. 1996. Registration o f 'Deliróse’ rice. Crop Sei. 36:1413.<br />
Jodon, N. E. 1965. Registration of'Satu rn ’ rice. Crop Sei. 5:288.<br />
Jodon, N. E., <strong>and</strong> E. A. Sonnier. 1973. Registration o f Della rice. Crop Set. 13:773.<br />
Johnson, C. W. 1994. Head rice factors in a multiple objective breeding program. In<br />
Proceedings of the 25th <strong>Rice</strong> Technical Working Group, New Orleans, LA, Mar. 5 -<br />
9. Texas Agricultural Experiment Station, Texas A&M University System, College<br />
Station, TX , pp. 48-49.<br />
Johnston, T. H., B. R. Wells, M. A. M archetti, E N. Lee, <strong>and</strong> S. E. Henry. 1979. Registration<br />
o f ‘M ars’ rice. Crop Sei. 19:743-744.<br />
Johnston, T. H., K. A. Kuenzei, F. N. Lee, B. R. Wells, S. E. Henry, <strong>and</strong> R. FI. Dilday.<br />
1984. Registration o f ‘Newbonnet’ rice. Crop Sei. 24:209-210.
1<br />
Techniques for Development of New Cultivars 199<br />
Jones, D. B., <strong>and</strong> M. L. Peterson. 1976. <strong>Rice</strong> seedling vigor at suboptimal temperatures.<br />
Crop Sei 16:102-105.<br />
Juliano, B. O. 1971. A simplified assay for milled rice amylose. Cereal Sei Today<br />
1 6 :3 3 4 -3 3 6 ,3 3 8 , 360.<br />
Juliano, B. O. 1985. Criteria <strong>and</strong> tests for rice grain qualities. In B. O. Juliano (ed.),<br />
<strong>Rice</strong> Chemistry <strong>and</strong> Technology. American Association o f Cereal Chemist, St. Paul,<br />
M N, pp. 443-513.<br />
Lai, X .-H ., <strong>and</strong> A. M. McClung. 1998. Development o f a cold tolerance screening<br />
test for use in a rice breeding program. In Proceedings o f the 27th <strong>Rice</strong> Technical<br />
Working Group, Reno, NV, Mar. 1 ^ . Texas Agricultural Experiment Station,<br />
Texas A&M University System, College Station, TX , p. 63.<br />
Linscombe, S. D., F. Jodari, K. S. McKenzie, P. K. Bollich, L. M. W hite, D. E. Groth,<br />
<strong>and</strong> R. T. Dun<strong>and</strong>. 1993a. Registration o f ‘Cypress’ rice. Crop Sei 33:355.<br />
Linscombe, S. D., E Jodari, K. S. McKenzie, P. K. Bollich, L. M . W hite, D. E. Groth,<br />
<strong>and</strong> R. T. Dun<strong>and</strong>. 1993b. Registration o f ‘Bengal’ rice. Crop Sei 33:645-646.<br />
Linscombe, S. D., F. Jodari, P. K. Bollich, D. E. Groth, L. M. W hite, Q. R. Chu,<br />
R. T. Dun<strong>and</strong>, <strong>and</strong> D. E. S<strong>and</strong>ers. 2000. Registration o f ‘Cocodrie’ rice. Crop Sei<br />
40:294.<br />
Linscombe, S. D., F. Jodari, P. K. Bollich, D. E. Groth, L. M . W hite, Q. R. Chu, R. T.<br />
Dun<strong>and</strong>, <strong>and</strong> D. E. S<strong>and</strong>ers. 2001. Registration o f ‘EaiT rice. Crop Sei 4 1 :2 0 0 3 -<br />
2004,<br />
Little, R. R., G. B. Hilder, <strong>and</strong> E. H. Dawson. 1958. Differential effect o f dilute alkali<br />
on 25 varieties o f milled rice. Cereal Chem. 35:111-126.<br />
Mackill, D. J., P. M . Colowit, <strong>and</strong> J. J. Oster. 1998. Molecular markers linked to stem rot<br />
resistance in rice. In Proceedings of the 27th <strong>Rice</strong> Technical Working Group, Reno,<br />
NV, Mar. 1-4. Texas Agricultural Experiment Station, Texas A&M University<br />
System, College Station, TX, p. 75.<br />
Marchetti, M. A, 1983a. Dilatory resistance to rice blast in U.S.A. rice. Phytopathology<br />
73:645-649.<br />
Marchetti, M. A. 1983b. Potential impact o f sheath blight on yield <strong>and</strong> milling quality<br />
o f short-statured rice lines in the southern United States. Plant Dis, 6 7 :1 6 2 -<br />
165.<br />
Marchetti, M. A. 1994. Race-specific <strong>and</strong> rate-reducing resistance to rice blast in U.S.<br />
rice cultivars. In R. S. Zeigler et al. (eds.). <strong>Rice</strong> Blast Disease. CAB International,<br />
pp. 231-244.<br />
Marchetti, M. A., <strong>and</strong> C. N. Bollich. 1991. Quantification o f the relationship between<br />
sheath blight severity <strong>and</strong> yield loss in rice. Plant Dis. 75:773-775.<br />
Marchetti, M. A., <strong>and</strong> X .-H . Lai. 1986. Screening techniques to identify slow-blasting<br />
lines. In Progress in Upl<strong>and</strong> <strong>Rice</strong> Research.. International <strong>Rice</strong> Research Institute,<br />
Manila, The Philippines, pp. 317-326.<br />
M archetti, M. A., <strong>and</strong> X .-H . Lai. 1998. Pathotype dynamics of Pyricularia grisea in die<br />
U.S. driven by race-specific resistance genes in rice. In Proceedings of the 27th <strong>Rice</strong><br />
Technical Working Group, Reno, NV, Mar. 1-4. Texas Agricultural Experiment<br />
Station, Texas A&M University System, College Station, TX , pp. 121-122.<br />
M archetti, M . A., X .-H . Lai, <strong>and</strong> C. N. Bollich. 1987. Inheritance o f resistance to<br />
Pyricularia oryzae in rice cultivars grown in the United States. Phytopathology<br />
77:799-804,
200 TKb <strong>Rice</strong> Plant<br />
M archetti, M. A„ C, N. Bollich, B. D. Webb, B. R. Jackson, A. M. McClung, J. E. Scott,<br />
<strong>and</strong> H. H, Hung, 1998. Registration o f ‘Jasmine 85’ rice. Crop Sei 38:896.<br />
McClung, A. M. 1993. Effect of Nitrogen Inputs on Yield <strong>and</strong> Milling Quality of<br />
<strong>Rice</strong> Varieties Released during Five Decades o f Research. Agron. Abstr. American<br />
Society of Agronomy, Madison, W I, p. 93.<br />
McClung, A, M ., <strong>and</strong> E, M . Castro, 1994. Screening for milling yield using rough rice<br />
<strong>and</strong> reduced sample size. In Proceedings of the 25th <strong>Rice</strong> Technical Working Group,<br />
New Orleans, LA, Mar. 5 -9 . Texas Agricultural Experiment Station, Texas A8cM<br />
University System, College Station, TX, pp. 4 9 -50.<br />
McClung, A. M.> X .-H . Lai, <strong>and</strong> M. A. Marchetti. 1996a, Association of panicle blight<br />
symptoms with rice seed quality. In Proceedings of the 26th Rke Technical Working<br />
Group, San Antonio, TX , Feb. 2 5 -28. Texas Agricultural Experiment Station,<br />
Texas A8cM University System, College Station, TX , p. 136.<br />
McClung, A, M ., M. A. Marchetti, X.-H . Lai, <strong>and</strong> B. L. Tillman. 1996b. Association o f<br />
genetic <strong>and</strong> environmental factors with panicle blight. In Proceedings of the 26th<br />
<strong>Rice</strong> Technical Working Group, San Antonio, TX , Feb. 2 5 -2 8 . Texas Agricultural<br />
Experiment Station, Texas A&M University System, College Station, TX , p. 135,<br />
McClung, A. M ., M . A. Marchetti, B. D. Webb, <strong>and</strong> C. N. Bollich. 1997. Registration<br />
o f ‘Jefferson’ rice. Crop Sei 37:629-630.<br />
McClung, A. M., M. A. Marchetti, B. D. Webb, <strong>and</strong> C. N. Bollich. 1998a. Registration<br />
o f ‘Dixiebelle’ rice. Crop Sei 38:898.<br />
McClung, A. M ., G. C. Eizenga, C. Bastos, B. L. TiUraan, <strong>and</strong> J. N. Rutger. 1998b. Yield<br />
comparison o f indica <strong>and</strong> U.S. commercial cultivars grown in the southern U.S.<br />
<strong>and</strong> Brazil. In Proceedings of the 27th <strong>Rice</strong> Technical Working Group, Reno, NV,<br />
Mar. 1-4. Texas Agricultural Experiment Station, Texas A8cM University System,<br />
College Station, TX, p, 59.<br />
M cCouch, S, R., M. J. Thom son, E. M . Septiningsih, P. Moncada, J. Li, J. Xiao, S. N.<br />
Ahn, T. Tai, C. Martinez, A. McClung, X .-H . Lai, S. Moeljopawiro, L. P. Yuan,<br />
H. Moon, E. Guimaraes, <strong>and</strong> J. Tohme. 2001. Wild QTLs for rice improvement.<br />
In W. G. Rockwood (ed.), Proceedings of the Ch<strong>and</strong>ler Symposium: <strong>Rice</strong> Research<br />
<strong>and</strong> Production in the 21st Century. June 15-1 7 ,2 0 0 0 . International <strong>Rice</strong> Research<br />
Institute, Manila, The Philippines, pp, 151-169.<br />
M cllrath. W. 0 . 1984. Seedling cold tolerance <strong>and</strong> vigor. In The Semidwarfs: A New Era<br />
in <strong>Rice</strong> Production, Publ. B-1462. Texas Agricultural Experim ent Station, Texas<br />
A&M University System, College Station, T X , pp. 11-14.<br />
McKenzie, K. S., C. W. Johnson, S. T. Tseng, J. J. Oster, <strong>and</strong> D. M . Br<strong>and</strong>on. 1994.<br />
Breeding improved rice cultivars for temperate regions: a case study. Aust. J. Exp.<br />
Agric. 34:897-905.<br />
Moldenhauer, K. A. K., <strong>and</strong> F. N. Lee. 1994. Recurrent selection for sheath blight<br />
tolerance in rice. In E. Humphreys, et al. (eds.). Proceedings on Temperate <strong>Rice</strong>:<br />
Achievements <strong>and</strong> Potential, VoL 1, Temperate <strong>Rice</strong> Conference, Leetou, NSW,<br />
Australia, Feb. 2 1 -24. Charles Sturt University, Wagga Wagga, New South Wales,<br />
Australia, pp. 2 5 -33.<br />
Moldenhauer, K. A. K., R N. Lee, R. J. Norman, R. S. Helms, B. R. Wells, R. H. Dilday,<br />
P. C. Rohm an, <strong>and</strong> M. A. Marchetti. 1990. Registration o f TCaty’ rice. Crop Sei<br />
30:747-748,<br />
Moldenhauer, K. A. K., K. A. Gravois, R N. Lee, R. J. Norman, J. L. Bernhardt, B. R.<br />
Wells, R. H. Dilday, M. M. Blocker, P C. Rohm an, <strong>and</strong> T. A. M cM inn. 1998.<br />
Registration o f ‘Drew’ rice. Crop Sei 38:896-897.
Techniques for Development of New Cultivars 201<br />
Oster, J. J. 1990. Screening techniques for stem rot resistance in rice in California.<br />
Plant Dis. 74:545-548.<br />
Oster, J. J. 1992. Reaction o f a resistant breeding line <strong>and</strong> susceptible California rice<br />
cultivars to Sclerotium oryzae. Plant Dis. 76;740-744.<br />
Pan, X. B., M. C. Rush, X. Y. Sha, Q. J. Xie, S, D, Linscombe, S. R. Stetina, <strong>and</strong> J. H,<br />
Oard. 1999. M ajor gene, nonallelic sheath blight resistance from the rice cultivars<br />
Jasmine 85 <strong>and</strong> Teqing. Crop Set. 39:338-346.<br />
Pinson, S. R. M. 1994. Inheritance o f aroma in six rice cultivars. Crop Set. 3 4 :1 1 5 1 -<br />
'1157.<br />
Redona, E. D., <strong>and</strong> D. J. Macldll. 1996a. Genetic variation for seedling vigor traits in<br />
rice. Crop Sei. 36:285-290.<br />
Redona, E. D., <strong>and</strong> D. J. Mackill. 1996b. Mapping quantitative trait loci for seedling<br />
vigor in rice using RFLPs. Theor. Appl Genet. 92:395-402.<br />
Redona, E. D., <strong>and</strong> D. J. MackiU. 1996c. Molecular mapping o f quantitative trait loci<br />
in japónica rice. Genome 39:395-403.<br />
Rister, M. E., H. L. Goodwin, R. E. Branson, J. W. Stansel, <strong>and</strong> B. D. Webb. 1992.<br />
The U.S. aromatic rice market: results o f an Asian-American household test. In<br />
Proceedings of the 24th <strong>Rice</strong> Technical Working Group, Little Rock, AR, Feb. 23-26.<br />
Texas Agricultural Experiment Station, Texas A&M University System, College<br />
Station, TX , p. 62.<br />
Roberts, S. R., J. E. Hill, D. M. Br<strong>and</strong>on, B. C. Miller, S. C. Scardaci, C, M . W ick, <strong>and</strong><br />
J. F. Williams. 1993. Biological yield <strong>and</strong> harvest index in rice: nitrogen response<br />
o f tall <strong>and</strong> semidwarf cultivars. J. Prod. Agrie. 6:585-588.<br />
Rush, M. C., S. D. Linscombe, X. B. Pan, X. Y. Sha, Q. M. Shaq, <strong>and</strong> S. R. Stetina. 1998.<br />
Development o f sheath blight resistance rice lines. In Proceedings o f the 27th <strong>Rice</strong><br />
Technical Working Group, Reno, NV, Mar. 1-4, Texas Agricultural Experiment<br />
Station, Texas A&M University System, College Station, T X , p. 129.<br />
Rutger, J. N. 1992. Impact of Mutation Breeding in <strong>Rice</strong>: A Review. Mutât. Breed. Rev.<br />
8. FAO/IAEA, Vienna, pp. 1-23.<br />
Rutger, J. N., <strong>and</strong> C, N, Bollich. 1991. Use o f introduced germplasm in U.S. improvem<br />
ent, In Use of Plant Introductions in Cultivar Development, Part 1. CSSA Spec.<br />
Publ. Crop Science Society o f America, Madison, W I, pp. 1-13.<br />
Rutger, J. N., M. L. Peterson, <strong>and</strong> C. Hu. 1977. Registration o f Calrose 76 rice. Crop<br />
Sä. 17:978.<br />
Rutger, J. N., K. S. McKenzie, K. A. K. Moldenhauer, A. M . McClung, K. A. Gravois,<br />
S. D. Linscombe, <strong>and</strong> D. G. Kanter. 1998. <strong>Rice</strong> quality breeding efforts in the<br />
USA, In Proceedings of the International Symposium on <strong>Rice</strong> Quality, Nottingham,<br />
Engl<strong>and</strong>, Nov. 2 4 -2 7 ,1 9 9 7 ,<br />
Saraonte, S. O. P. B., L. T. W ilson, A. M . McClung, <strong>and</strong> L. Tarpley. 2001. Seasonal dynamics<br />
o f nonstructural carbohydrate partitioning in 15 diverse rice genotypes.<br />
Crop Sei. 41:902-909.<br />
Scott, J. E., B. D. Webb, <strong>and</strong> H. M. BeacheU. 1964. A small scale rice test tube miller.<br />
Crop Sd. 4:231-232.<br />
Shalijahan, A. K, M, M . C. Rush, C. A. Clark, <strong>and</strong> D. E. Groth. 1998. Bacterial sheath<br />
rot <strong>and</strong> panicle blight o f rice in Louisiana. In Proceedings of the 27th <strong>Rice</strong> Technical<br />
Working Group, Reno, NV, Mar, 1-4, Texas Agricultural Experim ent Station,<br />
Texas A&M University System, College Station, T X , p. 131.<br />
Sood, B. C., <strong>and</strong> E, A. Siddiq. 1978. A rapid technique for scent determ ination in rice.<br />
Indian J. Genet, Plant Breed, 38:268-271.
202 The <strong>Rice</strong> Plant<br />
Texas Agricultural Extension Service. 2001. <strong>Rice</strong> Production Guidelines. Publication<br />
D -1253. Texas A&M University System, College Station, TX.<br />
Tseng, S. X , <strong>and</strong> J. J. Oster. 1994. Registration o f 87-Y-550 rice germplasm line resistant<br />
to stem rot disease. Crop Sei. 34:314.<br />
Tseng, S. X , H. L. Carnahan, C. W. Johnson, J. J. Oster, J. E. Hill, <strong>and</strong> S. C, Scardaci,<br />
1984. Registration o f X -2 0 2 ’ rice. Crop Sei. 24:1213-1214.<br />
Tseng, S, X , C. W. Johnson, A. A. Grigarick, J. N. Rutger, <strong>and</strong> H. L. Carnahan. 1987.<br />
Registration o f short stature, early maturing, <strong>and</strong> water weevil tolerant germ-<br />
plasm lines o f rice. Crop Sei 27:1320-1321.<br />
Tseng, S. X , C. W. Johnson, K. S. McKenzie, J. J. Oster, J. E. Hill, <strong>and</strong> D. M . Br<strong>and</strong>on.<br />
1997a. Registration o f X '-204’ rice. Crop Sei 37:1390.<br />
Tseng, S. X , K. S. McKenzie, C. W. Johnson, J. J, Oster, J. E. Hill, <strong>and</strong> D. M. Br<strong>and</strong>on.<br />
1997b. Registration o f o f A -2 0 X rice. Crop Sei 37:1390-1391.<br />
Tseng, S. X , C. W. Johnson, K. S. McKenzie, J. J. Oster, J. E. Hill, <strong>and</strong> D. M . Br<strong>and</strong>on.<br />
2001a. Registration o f'L -2 0 5 ’ rice. Crop Sei 41:2004.<br />
Tseng, S. X , K. S. McKenzie, C. W. Johnson, J. J. Oster, J. E, Hill, <strong>and</strong> D. M. Br<strong>and</strong>on.<br />
2001b. Registration o f ‘Calm ati-201’ rice. Crop Sei 41:2005.<br />
Turner, F. X , <strong>and</strong> M . F. Jund. 1993. <strong>Rice</strong> ratoon crop yield linked to main crop stem<br />
carbohydrates. Crop Sei 33:150-153.<br />
Turner, F. X , C. C. Chen, <strong>and</strong> C. N. Bollich. 1982. Coleoptile <strong>and</strong> mesocotyl lengths<br />
in semidwarf rice seedlings. Crop Sei 22:43-46.<br />
Webb, B. D. 1972, An automated system o f amylose analysis in whole-kernel rice.<br />
Cereal Sei Today 30:284<br />
Webb, B. D. 1980. <strong>Rice</strong> quality <strong>and</strong> grades. In B. S. Luh (ed.), <strong>Rice</strong>: Production <strong>and</strong><br />
Utilization. AVI, Westport, CT, pp. 543-565.<br />
Webb, B. D., <strong>and</strong> C. R. Adair. 1970. Laboratory parboiling apparatus <strong>and</strong> methods of<br />
evaluating parboil-canning stability o f rice. Cereal Chem. 47:708-714.<br />
Wu, G. W,, L. X W ilson, <strong>and</strong> A. M. McClung. 1998. Contribution o f rice tillers to dry<br />
matter accumulation <strong>and</strong> yield. Agron. J. 90:317-323.<br />
Xie, Q. J., S. D. Linscorae, M. C. Rush, <strong>and</strong> F. Jodari-Karimi, 1992. Registration of<br />
LSBR-33 <strong>and</strong> LSBR-5 sheath blight-resistant germplasm lines o f rice. Crop Sd.<br />
32:507.
Chapter<br />
IS<br />
<strong>Rice</strong> Bio<strong>technology</strong><br />
Thomas H. Tai<br />
U S O U R S -S P A<br />
Dale Bumpers National <strong>Rice</strong> Research Center<br />
Stuttgart, Arkansas<br />
INTRODUCTION<br />
<strong>Rice</strong> Bio<strong>technology</strong> <strong>and</strong> the Rockefeller Foundation<br />
<strong>Rice</strong> as a Model System<br />
RICE GENOME ANALYSIS<br />
Classical Genetic Linkage Maps<br />
Molecular Genetic Linkage Maps<br />
Physical Mapping of <strong>Rice</strong> Chromosomes<br />
Mapping ond Cloning Genes of interest<br />
Structural <strong>and</strong> Functional Genomics of <strong>Rice</strong><br />
CONVENTIONAL BIOTECHNOLOGY<br />
Marker-Assisted Selection<br />
Induced Mutotions<br />
TISSUE CULTURE AND TRANSFORMATION<br />
Anther Culture<br />
Somaclonal Variation ond Somatic Mutations<br />
Genetic Transformation<br />
GENETIC ENGINEERING IN RICE<br />
Nutrition <strong>and</strong> Grain Quality<br />
Yield Enhancement<br />
Herbicide Resistance<br />
Insect Resistance<br />
Disease Resistance<br />
Stress Tolerance<br />
FUTURE PROSPECTS<br />
ACKNOWLEDGMENTS<br />
REFERENCES<br />
<strong>Rice</strong>: Origin, History, Technology, <strong>and</strong> Production, edited by C, Wayne <strong>Smith</strong><br />
ISBN 0-471-34516-4 © <strong>2003</strong> John Wiley & Sons, Inc.<br />
203
204 The <strong>Rice</strong> Plont<br />
INTRODUCTION<br />
From the first studies on rice tissue culture in the 1950s to the development o f the<br />
framework molecular genetic maps 40 years later, rice bio<strong>technology</strong> has yet to provide<br />
the promised breakthroughs <strong>and</strong> reach the lofty status achieved by the Green<br />
Revolution. Recent events however, such as the development oigolden rice (Potrykus,<br />
2001) <strong>and</strong> the sequencing o f the rice genome (Pennisi, 2000; Davenport, 2001), have<br />
served to move rice center stage in agricultural bio<strong>technology</strong>, providing ju st a minor<br />
glimpse o f things to come. Furthermore, the past two decades have seen an explosive<br />
growth <strong>and</strong> continued refinement in the fields of molecular genetics <strong>and</strong> biology,<br />
which provide the foundation for modern bio<strong>technology</strong>. W ith these developments<br />
come unprecedented opportunities to increase the <strong>production</strong> <strong>and</strong> quality o f the<br />
foods we eat.<br />
<strong>Rice</strong> Bio<strong>technology</strong> <strong>and</strong> the Rockefeller Foundation<br />
i<br />
Recognizing the potential o f bio<strong>technology</strong>, the Rockefeller Foundation initiated an<br />
international program on rice bio<strong>technology</strong> in the early 1980s. The objective o f this<br />
program was to ensure that tlie benefits o f bio<strong>technology</strong> reach farmers in the developing<br />
world (Normile, 1999). To achieve this, leading plant laboratories in advanced<br />
countries were recruited to work with rice, developing the tools for bio<strong>technology</strong> <strong>and</strong><br />
training foreign scientists to continue this work in their hom e countries. Meanwhile<br />
in those developing countries, efforts to increase bio<strong>technology</strong> capacity <strong>and</strong> integrate<br />
that capacity into national rice-breeding programs were made with the involvement<br />
o f the International <strong>Rice</strong> Research Institute.<br />
In 1999, the Rockefeller Foundation brought an official end to the program with<br />
the knowledge that the funding it provided over the past 15 years had served to<br />
ensure the application o f rice bio<strong>technology</strong> in countries needing it most. Among the<br />
successes are development o f cornerstone molecular maps o f rice, generation o f rice<br />
tolerant o f high-alum inum soils, cloning o f the first disease resistance gene in rice (Xa-<br />
21), <strong>and</strong> the development o f cultivars using tissue culture <strong>and</strong> genetic engineering,<br />
some o f which are currently being field tested. The most notable o f these genetic<br />
engineering projects involves introduction of the provitamin A biosynthesis pathway<br />
into rice endosperm, resulting in golden rice, which has been hailed by proponents<br />
of bio<strong>technology</strong> as a prime example o f the potential o f agricultural bio<strong>technology</strong> to<br />
benefit humankind (Guerinot, 2000; Potrykus, 2001).<br />
Perhaps the m ost valuable outcome o f the Rockefeller program has been the<br />
integration o f molecular tools <strong>and</strong> resources, such as molecular markers, with traditional<br />
rice research <strong>and</strong> breeding programs, thus helping to bridge the gap between<br />
the development o f bio<strong>technology</strong> <strong>and</strong> the application o f bio<strong>technology</strong> to real-world<br />
problems. The close of the Roclcefeller rice bio<strong>technology</strong> program comes at a time<br />
when interest in rice around the world is probably at a peak, due to various efforts<br />
by the public <strong>and</strong> private sectors to sequence its genome. For those interested<br />
in applying bio<strong>technology</strong> to the improvement o f rice, the next decade holds great<br />
promise.
<strong>Rice</strong> Bio<strong>technology</strong> 205<br />
<strong>Rice</strong> as a Model System<br />
Its stature as one o f the two m ost im portant staple crops in the world (wheat being the<br />
other) notwithst<strong>and</strong>ing, the past two decades has seen rice becom e the best characterized<br />
at the molecular level of any crop species, for two main reasons. First, among<br />
the m ajor cereals, rice has the smallest genome (around 430 M b; Arumuganathan <strong>and</strong><br />
Earle, 1991), thus making it the m ost amenable to analyses such as genome mapping<br />
<strong>and</strong> sequencing. Second, as a m onocot <strong>and</strong> a grass, rice is viewed as the counterpart to<br />
the dicot model system, Arahidopsis thaliana^ <strong>and</strong> a baseline for examining the larger<br />
genomes of other members o f the Gramineae, including wheat, maize, barley, oats,<br />
sugarcane, sorghum, <strong>and</strong> miUet. The close relationship o f rice witli other crops o f<br />
worldwide importance <strong>and</strong> the implication that knowledge gained from rice will aid<br />
in the improvement o f other grass species has been further highlighted by recent<br />
research examining synteny among the Gramineae (reviewed by Devos <strong>and</strong> Gale,<br />
1997; Freeling, 2001).<br />
This chapter provides a summary o f the m ajor advances in rice molecular biology<br />
<strong>and</strong> genetics over the past two decades, the application o f these advances to rice<br />
improvement, <strong>and</strong> the impact that current research efforts, such as genomics, wiU<br />
have on rice bio<strong>technology</strong> in the future.<br />
RICE 6EN0ME ANALYSIS<br />
The <strong>history</strong> <strong>and</strong> current status of rice genome analyses has been reviewed extensively<br />
in recent years (Izawa <strong>and</strong> Shimamoto, 1996; Sasaki <strong>and</strong> Moore, 1997; Goff, 1999;<br />
Mackill, 1999; Yuan et al., 2001). The following is a brief sum mary o f the key aspects<br />
o f rice genome analysis.<br />
Classical Genetic Linkage Maps<br />
Work on genetic linkage maps in rice was initiated over 80 years ago (Chapter 2.3).<br />
By 1985, a map o f 119 genes (primarily morphological mutants) was available (Kinoshita,<br />
1986), although it was considered o f very limited value to rice improvement<br />
programs (Mackill, 1999). During the past decade various groups have contributed to<br />
the integration o f linlcage maps based on phenotype <strong>and</strong> the molecular linkage maps<br />
based on DNA markers (Yoshimura et al., 1997).<br />
Molecular Genetic Linkage Maps<br />
The first molecular genetic map was published in 1988 (M cCouch et al., 1988) <strong>and</strong><br />
was derived using restriction fragment length polymorphism (RFLP) markers. Several<br />
more detailed molecular linkage maps have been developed using RFLPs (Causse et<br />
al,, 1994; Kurata et al., 1994; Harushima et al., 1998; reviewed by Nagamura et al.,<br />
1997). M ore recently, polymerase chain reaction (PC R )-based markers, including<br />
r<strong>and</strong>omly amplified polymorphic DNA (RAPD) markers (Redona <strong>and</strong> Macldll,
206 The <strong>Rice</strong> Plant<br />
1996) , amplified fragment length polymorphism (AFLP) markers (Maheswaran e ta l,<br />
1997) , <strong>and</strong> simple sequences repeat (SSR) markers (M cCouch et al., 1997), have had<br />
a significant im pact on mapping <strong>and</strong> marker-assisted selection. Various markers are<br />
being integrated into a com m on map to increase their utility (Cho et al., 1998), Overall,<br />
more than 3000 molecular markers are currently available to the public, making<br />
rice the best characterized crop species. An overview o f these marker systems can be<br />
found in Henry (1997) <strong>and</strong> Mackill (1999) <strong>and</strong> the references cited therein.<br />
Physical Mapping of <strong>Rice</strong> Chromosomes<br />
With the generation o f high-density molecular marker linkage maps <strong>and</strong> the advent of<br />
large insert DNA cloning methods, the physical mapping o f genomes became a reality.<br />
In rice, both yeast artificial chromosom e (YAC) <strong>and</strong> bacterial artificial chromosome<br />
(BAG) libraries have been constructed from several rice genotypes (Kurata et al., 1997;<br />
Zhang <strong>and</strong> W ing, 1997), Analysis o f the clones from these libraries using previously<br />
developed molecular markers <strong>and</strong> DNA fingerprinting o f the ends o f the clones themselves<br />
has enabled researchers to develop physical maps o f the rice genome (Hong,<br />
1997; Kurata et al., 1997; Zhang <strong>and</strong> W ing, 1997). These maps enable researchers to<br />
determine the actual physical distance between two DNA markers where previously<br />
only a genetic distance was known. Such inform ation is im portant in term s o f underst<strong>and</strong>ing<br />
genome organization <strong>and</strong> physical isolation o f genes o f interest by positional<br />
cloning <strong>and</strong> for determining the DNA sequence o f a given region.<br />
Mapping <strong>and</strong> Cloning Genes of Interest<br />
The availability o f an array of molecular markers widely distributed throughout the<br />
rice genome has enabled the mapping o f simply inherited traits as well as complex<br />
traits (m ost traits of agronomic importance are quantitatively inherited). In this way,<br />
molecular markers have facilitated the genetic dissection o f quantitative traits (Yano<br />
<strong>and</strong> Sasaki, 1997) <strong>and</strong>provide the foundation for isolation o f m ajor <strong>and</strong> m inor genes.<br />
Genes involved in various traits, including growth <strong>and</strong> development, abiotic <strong>and</strong><br />
biotic stress tolerance, grain quality, <strong>and</strong> yield, have been mapped relative to the<br />
various molecular frameworks available in rice (reviewed by Mackill, 1999).<br />
High-density molecular maps, large insert genomic libraries, <strong>and</strong> other molecular<br />
genetic tools <strong>and</strong> resources have greatly advanced the identification o f genes <strong>and</strong><br />
loci controlling traits o f biological <strong>and</strong> agronomic importance in rice. With many of<br />
these resources in place in the early 1990s, researchers were able to begin employing<br />
map-based or positional cloning to isolate genes based on their phenotype <strong>and</strong> map<br />
position. The first gene to be isolated from rice in this manner was the Xa-21 gene,<br />
which provides resistance to bacterial leaf blight disease (Song et al., 1995). Several<br />
other resistance genes have been cloned recently (Yoshimura et al., 1998; Z. Wang<br />
et a l, 1999; Bryan et al., 2000; W, Wang et al., 2001).<br />
Structural <strong>and</strong> Functional Genomics of <strong>Rice</strong><br />
Analysis o f the rice genome (i.e., rice genomics) began with the development o f the<br />
first molecular genetics maps o f rice. Efforts were broadened in the late 1980s <strong>and</strong>
<strong>Rice</strong> Bio<strong>technology</strong> 207<br />
early 1990s, as Japanese researchers recognized the need to isolate <strong>and</strong> characterize<br />
rice genes of agronomic <strong>and</strong> scientific importance for the development o f improved<br />
cultivars, thus launching their <strong>Rice</strong> Genome Research Program in 1991 (referred to<br />
as the RGP, http://rgp.dna.affrc.go.jp; Stevens, 1994). During the past 10 years, the<br />
RGP has spearheaded the molecular characterization o f rice with the development<br />
o f extensive genetic <strong>and</strong> physical maps (Kurata et al., 1994, 1997; Harushiraa et al.,<br />
1998), <strong>and</strong> the large-scale sequencing o f expressed sequence tags (ESTs) derived from<br />
rice cDNAs (reviewed by Yamamoto <strong>and</strong> Sasald, 1997).<br />
In 1997, the RGP took the lead in a publicly funded international project to<br />
sequence the entire rice genome by the middle to late 2000s, with m ajor participation<br />
from the United States, Korea, the European Union, China, <strong>and</strong> various Asian<br />
nations. As the first (<strong>and</strong> perhaps the only) crop species to be targeted for complete<br />
sequencing, the decision to embark on a rice genome project reinforced tlie importance<br />
o f rice to tlie agricultural <strong>and</strong> plant research communities. Recent reports by life<br />
science companies M onsanto (Pennisi, 2000; Barry, 2001) <strong>and</strong> Syngenta (Davenport,<br />
2001) on tlie com pletion o f their efforts to sequence the rice genome means that<br />
the resources needed to advance the molecular dissection o f rice (<strong>and</strong> other grass<br />
species) are now at h<strong>and</strong> (Barry, 2001). Much work remains to annotate the genome<br />
sequence (i.e., identify putative genes) <strong>and</strong> ensure accuracy. Nevertheless, researchers<br />
are now in the position to employ functional genomics (Boguski <strong>and</strong> Hieter, 1997;<br />
Bouchez <strong>and</strong> Hofte, 1998) to determine how rice genes function during growth,<br />
development, <strong>and</strong> in response to the environment (M atsumura et al., 1999; Zhang<br />
et al., 2001),<br />
As with the achievements described later in this chapter, future applications o f<br />
bio<strong>technology</strong> in rice will be based on the knowledge gained from basic studies on<br />
gene <strong>and</strong> protein fiinction. The exp<strong>and</strong>ing tools <strong>and</strong> resource o f genomics will certainly<br />
help answer questions regarding fundamental life processes, <strong>and</strong> with these<br />
answers should come biotech-based solutions to feeding the world.<br />
CONVENTIONAL BIOTECHNOLOGY<br />
Although many equate bio<strong>technology</strong> with genetic engineering, several aspects o f<br />
bio<strong>technology</strong> involve “engineering” without the introduction o f recom binant DNA<br />
through genetic transform ation. The simple crossing o f different individuals to produce<br />
improved hybrid cultures represents the application o f bio<strong>technology</strong>. Although<br />
humans have practiced plant breeding for hundreds o f years, the development <strong>and</strong> use<br />
o f molecular markers over the past decade have proven to be a tremendous example<br />
o f the application o f modern tools to age-old methods (Mackill, 1999; Zhang <strong>and</strong><br />
Yu, 2000).<br />
Marker-Assisted Selection<br />
RFLPs were the first molecular markers to find broad use in genetic mapping <strong>and</strong><br />
have been used to map many rice genes involved in both simple <strong>and</strong> complex traits<br />
(Nagamura et al,, 1997; Zhang <strong>and</strong> Yu, 2000). Unfortunately, the expensive <strong>and</strong> cum <br />
bersome nature of hybridization-based RFLP analysis has somewhat limited their<br />
utility in large-scale breeding efforts.
"I'V.<br />
208 The <strong>Rice</strong> Plañí<br />
More recently, the development o f PCR-based markers has greatly reduced the<br />
cost <strong>and</strong> efficiency o f using DNA markers to follow or tag genes o f interest (McCouch<br />
et al,, 1997; Mackill, 1999). Such markers are now finding broad use in various breeding<br />
programs around the world (Chen et a l, 2000; Sanchez et a l, 2000; Bergman<br />
et a l, 2001).<br />
Induced Mutations<br />
The objective o f mutation breeding is to enhance elite germplasm or cultivars by altering<br />
single specific traits (e.g., early flowering, male sterility, semidwarfness) witliout<br />
affecting other traits that make those lines desirable. The use o f induced mutations has<br />
led to the development o f several improved cultivars that have had a significant impact<br />
on rice <strong>production</strong> (Rutger, 1992). The <strong>history</strong> o f this technique <strong>and</strong> a description of<br />
some useful rice mutants are given in Chapter 2.3.<br />
Although induced mutation <strong>technology</strong> has resulted in the rapid improvement<br />
of rice <strong>and</strong> other species, mutant phenotypes with no apparent agronomic value have<br />
typically been ignored. This disconnect between applied <strong>and</strong> basic research has been<br />
recognized in recent years as the im portance o f mutant phenotypes for dissecting gene<br />
function has becom e clear.<br />
The reverse genetics approach has found great utility in recent years (Bouchez<br />
<strong>and</strong> Hofte, 1998; Martienssen, 1998) <strong>and</strong> its application to rice will be im portant to<br />
determining tlie function o f the thous<strong>and</strong>s o f genes uncovered by sequencing o f the<br />
rice genome. Several strategies for generating populations with mutations o f interest<br />
have been <strong>and</strong> are being developed for rice. They include T-DNA tagging (Jeon et<br />
a l, 2000), transposon tagging (Izawa et a l, 1997; Greco et a l, 2001), use o f retrotransposons<br />
<strong>and</strong> tissue culture (Hirochika, 1997; Yamazaki et a l, 2001), <strong>and</strong> highthroughput<br />
screening o f induced point mutations (M cCallum et al> 2000; Colbert<br />
e t a l, 2001).<br />
TISSUE CULTURE AND TRANSFORMATION<br />
Japanese scientists first reported rice tissue culture experiments in the mid-1950s.<br />
Studies on callus induction <strong>and</strong> growth <strong>and</strong> the regeneration o f rice plants from callus<br />
cultures followed soon thereafter (see Lynch et a l, 1991, for review). Tissue culture<br />
in <strong>and</strong> o f itself serves as an agent of bio<strong>technology</strong> (e.g., anther culture, somaclonal<br />
variation, <strong>and</strong> som atic m utation). Moreover, the regeneration o f whole plants from<br />
cultured cells is the foundation for genetic transformation, a requisite for genetic<br />
engineering.<br />
Anther Culture<br />
O f particular importance to rice cultivar development was the finding that haploid<br />
rice plants could be produced by anther culture (Niizeki <strong>and</strong> O ono, 1968). This enabled<br />
the rapid creation o f homozygous lines, thus reducing the tim e required for<br />
breeding new cultivars by at least 3 to 5 years. Furthermore, the expression o f recessive
<strong>Rice</strong> Bio<strong>technology</strong> 209<br />
genes is uncovered in haploids <strong>and</strong> fixed on doubling o f the chromosomes. In addition<br />
to serving as a tool for cultivar development, populations derived by anther culture<br />
have enabled basic researchers to map molecular markers efficiently <strong>and</strong> to characterize<br />
genetically complex traits.<br />
Somoclonal Variation <strong>and</strong> Somatic Mutations<br />
Phenotypic variation is often observed in plants that have been regenerated from cultured<br />
cells. In this way, tissue culture m aybe used to identify variants or mutants that<br />
express improved or desirable traits, including increased stress tolerance (reviewed by<br />
Lynch et al., 1991).<br />
Genetic Transformation<br />
Genetic transformation is a key element in studying gene function <strong>and</strong> genetic engineering<br />
(transfer o f genes either from other rice accessions or other species for<br />
crop improvement). Transgenic rice plants were first produced in the late 1980s by<br />
direct gene transfer into protoplasts (reviewed by Hodges et al., 1991). Since then,<br />
several methods for genetic transform ation o f rice have been explored over the years<br />
(reviewed by Gao et al., 1991). The two m ost prom inent methods are direct transfer<br />
by particle bom bardm ent o f callus tissue <strong>and</strong> Agrohacterium-meáiatQá transfer.<br />
Christou et al. (1991) reported the recovery o f fertile transgenic rice from im m a<br />
ture embryos that had been transformed via particle bom bardm ent. Significantly, this<br />
m ethod enabled generation o f both japónica <strong>and</strong> indica cultivars at high frequency,<br />
thus bypassing the difficulty in transforming indicas which typically exhibit poor<br />
regeneration. Particle bom bardm ent is still used frequently for the <strong>production</strong> o f<br />
transgenics (Christou, 1997), altliough the need for high cost equipment <strong>and</strong> notable<br />
improvements in Agrobacterium-medhted transformation o f rice may lim it its utility<br />
in the future.<br />
Difficulties in infecting m onocots with Agrobacterium resulted in the developm<br />
ent o f alternative methods, such as particle bombardment. However, in the m id-<br />
1990s, researchers were finally able to develop efficient protocols for transforming<br />
rice using Agrobacterium (Hiei et al., 1994; Rashid et al., 1996). The selection o f<br />
actively dividing, embryonic tissues (e.g., immature embryos or calli derived from<br />
scutellar tissue), in conjunction with use o f the inducing compound acetosyringone,<br />
proved crucial in the successful <strong>production</strong> of transgenic rice at high frequency. Many<br />
other factors also must be considered, including the strain o f Agrobacterium used, the<br />
vectors <strong>and</strong> selectable markers, <strong>and</strong> tissue culture parameters (reviewed by Hiei et<br />
al., 1997). The development o f a robust <strong>and</strong> efficient genetic transformation system<br />
provides a key element necessary for both basic research on gene function <strong>and</strong> the<br />
application o f genetic engineering to rice improvement.<br />
GENETIC ENGINEERING IN RICE<br />
W ith the improvement o f genetic transformation methods <strong>and</strong> an ever-increasing<br />
knowledge base in the molecular genetics <strong>and</strong> biology o f rice <strong>and</strong> other plants, the
number o f projects aimed at improving yield <strong>and</strong> quality while lowering input/<br />
<strong>production</strong> costs through the development of genetically engineered rice will continue<br />
to rise. As with other food crops, rice bio<strong>technology</strong>, as it relates to genetic<br />
engineering, can be divided into those efforts aimed at reducmg <strong>production</strong> costs<br />
for the producer <strong>and</strong> those designed to increase value <strong>and</strong>/or improve quality for the<br />
consumer. The following represent some o f the most notable efforts to date.<br />
Although it is the main source o f calories for much o f the developing world, rice in its<br />
preferred, milled form provides relatively little nutritional value, as it lacks many vitamins<br />
<strong>and</strong> im portant micronutrients. In what st<strong>and</strong>s as the m ost prom inent example<br />
o f rice bio<strong>technology</strong> today, Ingo Potrykus <strong>and</strong> his collaborators recently engineered<br />
the provitamin A biosynthetic pathway into rice to address the issue o f vitam in A<br />
deficiency in children in developing countries (Potrykus, 2001). In the early 1990s,<br />
researdiers in the Potrykus lab demonstrated that specific expression o f the phytoene<br />
synthase from daffodil in the endosperm tissue o f rice resulted in the accumulation<br />
o f phytoene, a precursor to -carotene not normally found in the rice endosperm<br />
(Burkhardt et a l, 1997). This was followed up by the generation o f transgenic rice<br />
plants containing the phytoene synthase <strong>and</strong> lycopene )8-cyclase genes from daffodil<br />
<strong>and</strong> the phytoene desaturase gene from the bacteria Erwinia uredovora, resulting in<br />
the <strong>production</strong> o f -carotene <strong>and</strong> other carotenoid compounds in rice endosperm<br />
(Ye et al., 2000). Although m^ny studies still need to be conducted to determine<br />
the efficacy o f golden rice in alleviating vitam in A deficiency, its development has<br />
served to highlight the potential of bio<strong>technology</strong> to address issues o f importance to<br />
humanity (Guerinot, 2000; Potrykus, 2001).<br />
Another area o f current interest is increasing the iron content o f rice grains<br />
<strong>and</strong> improving the uptake o f the iron available in rice (Gura, 1999). Several groups<br />
have initiated efforts to increase iron by expressing tlie ferritin gene firom soybean<br />
(Goto et al., 1999; Drakakald et al., 2000) <strong>and</strong> bean (Lucca et al., 2000) in rice seed.<br />
These efforts have m et with varying degrees o f success. Another strategy involves tire<br />
expression o f foreign genes encoding proteins that may improve the absorption of<br />
iron during digestion (Lucca et al., 2000),<br />
In addition to efforts to increase tlie nutritional value o f rice that primarily are<br />
directed toward the needs o f developing countries, bio<strong>technology</strong> research also is<br />
aimed at altering physical traits o f the rice grain. Recently, Krishnamurthy <strong>and</strong> Giroux<br />
(2001) introduced the wheat puroindoline genes {pinA <strong>and</strong>pinB) into rice under the<br />
control o f the maize ubiquitin prom oter to examine their ability to alter grain texture.<br />
The proteins encoded by the pin genes are believed to play a m ajor role in wheat grain<br />
texture but are limited to the Triticeae species. Analysis o f transgenic rice indicated<br />
that expression o f ptnA <strong>and</strong>/or pinB genes reduced grain hardness <strong>and</strong> produced flour<br />
having reduced starch damage <strong>and</strong> an increased percentage o f fine flour particles,<br />
Yield Enhancement<br />
To increase the physiological efficiency o f rice, there has been great interest in engineering<br />
m etabolic pathways from other plants into rice, such as<br />
metabolism,
<strong>Rice</strong> Bio<strong>technology</strong> 211<br />
Transgenic rice expressing either the phosphoenolpyruvate carboxylase or the pyruvate,<br />
ortlrophosphate dikinase enzymes from maize show an increased photosynthetic<br />
capacity over untransformed controls (Ku et al., 2001). Preliminary field trials o f these<br />
transgenics indicated increased yield due to increased tiller number. Suzuki et al.<br />
(2000) reported alterations in carbon flow in rice transformed with the phosphoenolpyruvate<br />
carboxykinase gene from Urochloa panicoides. Together, these studies<br />
suggest that introduction o f the C4 photosynthesis enzymes may be an effective way<br />
to increase rice yields.<br />
Herbicide Resistance<br />
As with other plants, initial studies in rice involved the transfer o f selectable marker<br />
genes, many o f which provide protection against herbicidal compounds (thus the<br />
selection), to assist in the development o f genetic transform ation o f rice. Although<br />
weeds are the m ost costly problem associated with rice <strong>production</strong>, relatively little<br />
work on herbicide resistant transgenic rice has been reported compared with crops<br />
such as cotton <strong>and</strong> soybean.<br />
Currently, three systems for herbicide resistance (two o f which involve transgenics<br />
<strong>and</strong> one based on induced mutation) are close to being released to rice producers.<br />
They include glufosinate resistance via transfer o f the Bialophos resistance (bar) gene<br />
(Card et al., 1996; Sankula et al., 1997; Rood, 2000, 2001), glyphosate resistance via<br />
introduction o f the CP4 gene (Rood, 2000, 2001), <strong>and</strong> imidazolinone resistance via<br />
EM S-induced m utation oftheacetolactate synthase gene (C roughanetal., 1995,1996;<br />
Rood, 2000, 2001).<br />
insect Resistance<br />
Insects are a m ajor problem in Asia, where in addition to feeding on plants, many<br />
act as carriers o f plant viruses that can devastate rice fields. Since the early 1990s,<br />
researchers have been working on expression o f endotoxin genes from Bacillus thurin-<br />
giensisy a soil bacterium (Fujim oto et al., 1993). These toxins (com m only referred to<br />
as B t toxins) have specific biological activity against lepidopteran insects, including<br />
Icaffoldcr (Fujim oto et al., 1993; W unn et al., 1996), striped stem borer (Fujim oto<br />
et al., 1993; Wunn et al., 1996; Cheng et al., 1998), <strong>and</strong> yellow stem borer (Nayak<br />
et a l, 1997; Wunn et a l, 1996; Cheng et al., 1998). Recently, field tests were conducted<br />
with an elite Chinese com mercial hybrid lice (cultivar Shanyou 63) transformed with<br />
a recombinant B t toxin gene (Tu et a l, 2000). In this study, the transgenic plants<br />
displayed a high level o f protection against both natural <strong>and</strong> introduced infestations<br />
o f leaffolder <strong>and</strong> yellow stem borer without a reduction in yield. Genes from other<br />
species, such as corn (Irie et a l, 1996), potato (Duan et a l, 1996), <strong>and</strong> G alanthus<br />
nivalis (Rao et a l, 1998; Sudhakar et a l, 1998), have also been introduced into rice,<br />
although none have been field-tested to date,<br />
Disease Resistance<br />
Although a few disease resistance genes have been cloned from rice, transfer o f these<br />
genes to other accessions to generate new cultivars has not yet had a wide impact.
212 The <strong>Rice</strong> Plant<br />
The first gene cloned, Xa-21, has been introduced in other rice cultivars by genetic<br />
transformation (Zhao et al.> 2000). The resistance genes cloned to date are specific in<br />
nature, usually providing resistance against a single pathogen species or set o f races<br />
within a species. Several strategies for engineering resistance to pathogens have been<br />
examined in rice. The constitutive expression o f rice genes that normally are induced<br />
by infection has led to enhanced resistance against fungal pathogens, including rice<br />
blast <strong>and</strong> sheath blight (Schaffrath et al., 2000; Datta et al., 2001). Expression of<br />
genes from other organisms have also resulted in increased resistance to Xanthomonas<br />
oryzae pv. oryzae, the causal agent of bacterial leaf blight disease (Sharma et al., 2000;<br />
Tang et al., 2001). In the case o f viral pathogens, resistance has been obtained using<br />
various strategies, including the expression o f the coat protein o f rice stripe virus<br />
(Hayalcawa et al., 1992), the RNA-dependent RNA polymerase o f rice yellow mottle<br />
virus {Pinto et a l, 1999), <strong>and</strong> a ribozyme targeted, against the rice dwarf virus (Han<br />
et a l, 2000).<br />
Stress Tolerance<br />
Genetic engineering efforts to enhance rice’s tolerance to abiotic stress due to salt,<br />
drought, <strong>and</strong> cold have been reported recently. As with disease resistance, these strategies<br />
rely on the overexpression o f rice genes or the expression o f genes from other<br />
species.<br />
Two groups have reported the <strong>production</strong> o f transgenic rice expressing genes<br />
for the biosynthesis of glycinehetaine, an osraoprotectant. Sakamoto et a l (1998)<br />
developed transgenic rice that targeted the choline oxidase {codA) from Arthrobacter<br />
glohiformis to either the chloroplasts or the cytosol They found that their transgenics<br />
recovered from salt stress more rapidly than wildtype plants <strong>and</strong> that expression o f the<br />
protein in chloroplasts provided more tolerance to photoinhibition under stress conditions<br />
(salt <strong>and</strong> cold) than expression in the cytosol Kisliitani et a l (2000) observed<br />
enhancement of tolerance to salt <strong>and</strong> temperature stress in rice transformed with the<br />
betaine aldehyde dehydrogenase gene from barley. The protein, which is localized to<br />
peroxisomes, converted exogenously supplied betaine aldehyde into glycinehetaine,<br />
which increased stress tolerance. Salinity stress tolerance also appears to be enhanced<br />
by the expression o f arginine decarboxylavSe from oat (Roy <strong>and</strong> Wu, 2001). In addition<br />
to using foreign genes, stress tolerance in rice has been enhanced by overexpression<br />
of the rice genes encoding glutamine synthetase (Hoshida et a l, 2000) <strong>and</strong> calcium-<br />
dependent protein kinase (Saijo et a l, 2000).<br />
Low iron availability resulting from low soil pH is a growing problem in rice,<br />
which is particularly susceptible to deficiencies in ii'on. Recently, two genes from<br />
barley, which is not as susceptible to low-iron, encoding nicotianam ine aminotransferases<br />
were introduced into rice (Taltahashi et a l, 2001). These proteins are involved<br />
in the biosynthesis of phytosiderophores, iron chelators secreted from the roots o f cereal<br />
crops in order to solubilize iron in the soE. The transgenic rice exliibited improved<br />
tolerance to low-iron conditions, yielding about four times m ore tlian untransformed<br />
controls.<br />
FUTURE PROSPECTS<br />
i.<br />
Humans have been practicing bio<strong>technology</strong> for thous<strong>and</strong>s o f years. For example, the<br />
brewing o f beer <strong>and</strong> the making o f bread both depend on tlie use o f yeast, <strong>and</strong> the
<strong>Rice</strong> Biofóchnology 213<br />
selection o f high-yielding, good quality, naturahy occurring variants by our ancestors<br />
represents the basis for the many crop species we grow today. Nevertheless, bio<strong>technology</strong><br />
today is equated with genetic engineering, the application o f recom binant<br />
DNA <strong>technology</strong>, <strong>and</strong> genetic transformation. Hundreds o f examples of this form o f<br />
bio<strong>technology</strong> exist in the fields o f medicine <strong>and</strong> agriculture, <strong>and</strong> this num ber will<br />
continue to increase as more loiowledge o f life processes is attained <strong>and</strong> as technologies<br />
continue to be developed <strong>and</strong> refined.<br />
<strong>Rice</strong> provides a unique opportunity in basic research <strong>and</strong> the bio<strong>technology</strong> that<br />
springs from it. As the staple food for some o f the poorest, m ost underdeveloped,<br />
<strong>and</strong> m ost overpopulated countries in the world, rice represents a vehicle for modern<br />
researchers to put the positive aspects o f bio<strong>technology</strong> to work for humankind. As a<br />
model for other cereals, the lessons learned from the analysis o f the rice genome <strong>and</strong><br />
its genes should shed light on strategies for improving other crops. It is interesting to<br />
note that although the current enthusiasm for rice genomic research is well placed, the<br />
m ajority o f the examples o f genetic engineering described here are due to discoveries<br />
in other plant systems. No doubt, as the rice genome is unraveled over the years to<br />
come, many o f today’s questions concerning the promise o f bio<strong>technology</strong> wiU be<br />
answered.<br />
ACKNOWLEDGMENTS<br />
I wish to thank Dr. Robert Fjellstrom <strong>and</strong> Dr. Merle Anders for the many helpful<br />
suggestions <strong>and</strong> com ments on improving this chapter.<br />
REFERENCES<br />
Arumuganathan, K,, <strong>and</strong> E. D. Earle. 1991. Nuclear DNA content o f some im portant<br />
plant species. P lant M o l B io l 9:229-241.<br />
Barry, G. F. 2001. The use o f the Monsanto draft rice genome sequence in research.<br />
P lant P hysiol 125:1164-1165.<br />
Bergman, C. J., J. T. Delgado, A. H. McClung, R. G. Fjellstrom. 2001. An improved<br />
method for using a microsatellite in the rice w axy gene to determine amylase<br />
class. Cereal Chem. 78:257-260,<br />
Boguski, M „ <strong>and</strong> R Hieter. 1997. Functional genomics: it’s all how you read it. Science<br />
278:601-602<br />
Bouchez, D., <strong>and</strong> H. Hofte. 1998. Functional genomics in plants. P lant P hysiol 118:<br />
725-732.<br />
Bryan, G. X , K. S. Wu, L. Farrall, Y. Jia, H. P. Hershey, S. A. McAdams, K. N. Faulk,<br />
G. K, Donaldson, R. Tarchini, <strong>and</strong> B. Valent. 2000. A single amino acid difference<br />
distinguishes resistant <strong>and</strong> susceptible alleles o f the rice blast resistance gene P i<br />
ta. P lant Cell 12:2033-2045.<br />
Burkhardt, R K., R Beyer, J, W unn, A. Kloti, G. A. Armstrong, M . Schledz, J. von<br />
Lintig, <strong>and</strong> I. Potrykus. 1997. Transgenic rice (Ory^a sativa) endosperm expressing<br />
daffodil (Narcissuspseudonarcissus) phytoene synthase accumulates phytoene,<br />
a key intermediate o f provitamin A biosynthesis. P lan t /. 1 1 :1071-1078.<br />
Cao, J., W. Zhang, D. McElroy, <strong>and</strong> R, Wu. 1991. Assessment o f rice genetic transform<br />
ation techniques. In G. S. Khush <strong>and</strong> G. H. Toenniessen (eds.), P ice B io<strong>technology</strong>.<br />
CAB International, Wallingford, Oxon, Engl<strong>and</strong>, 175-198.
Causse, M ., T. Fulton, Y. Cho, S. Ahn, J. Chunwongse, K. Wu, J, Xiao, Z. Yu, P. Ronald,<br />
S. Harrington, G. Second, S. McCouch, <strong>and</strong> S. Tanksley. 1994. Saturated molec-<br />
ular map o f the rice genome based on an interspecific backcross population.<br />
Genetics 138:1251-1274.<br />
Chen, S., X. H. Lin, C. G. Xu, <strong>and</strong> Q. Zhang. 2000, Improvement o f bacterial resistance<br />
of ‘Minghui 63i an elite restorer line o f hybrid rice, by molecular marker-assisted<br />
selection. Crop S ei 40:239-244.<br />
Cheng, X., R. Sardana, H. Kaplan, <strong>and</strong> I. Altosaar. 1998. Agro&actermm-transformed<br />
rice plants expressing synthetic crylA (h) <strong>and</strong> crylA(c) genes are highly toxic to<br />
striped stem borer <strong>and</strong> yellow stem borer. Proc. N a tl Acad. S ei USA 95:2767-<br />
2772.<br />
Cho, Y. G., S. R. McCouch, M. Kuiper, M, R. Kang, J. Pot, J. T. M . Groenen, <strong>and</strong><br />
M. Y. Eun. 1998. Integrated map o f AFLP, SSLP, <strong>and</strong> RFLP markers using a<br />
recombinant inbred population of rice (O ryza sativa L.). Theor. A ppl Genet.<br />
97:370-380.<br />
Christou, P., T. L. Ford, <strong>and</strong> M . Kofron. 1991. Production o f transgenic rice (Oryza<br />
Sativa L.) plants from agronomicaliy important indica <strong>and</strong> japónica varities via<br />
electric discharge particle acceleration o f exogenous DNA into immature zygotic<br />
embryos. Bio/<strong>technology</strong> 9:957-962.<br />
Christou, P. 1997. <strong>Rice</strong> transform ation; bombardment. P lant M o l B io l 35:197-203.<br />
Colbert, T., B .}. Till, R. Tompa, S. Reynolds, M. N. Steine, A. X Yeung, C. M . McCal-<br />
lum, L. Comai, <strong>and</strong> S. Henikoff. 2001. High-throughput screening for induced<br />
point mutations. P lant P hysiol 126:480-484.<br />
Croughan, T. P., H. S. Utomo, D.'E. S<strong>and</strong>ers, <strong>and</strong> M. P. Braverman. 1995. Assessment<br />
o f imidazolinone-resistant rice. Annu. Res. Rep. La. State Vniv, (Baton Rouge, La.)<br />
87:491-525.<br />
Croughan, T, R, H. S. Utom o, D. E. S<strong>and</strong>ers, <strong>and</strong> M. R Braverman. 1996. Herbicide-<br />
resistant rice offers potential solution to red rice problem. La. Agrie, 39:10-12.<br />
Datta, K., J. Tu, N. Olivia, 1.1. Ona, R. Velazhahan, T. W. Mew, S. Muthukrishnan, <strong>and</strong><br />
S.K. Datta, 2001. Enhanced resistance to sheath blight by constitutive expression<br />
of infection-related chitinase in transgenic elite indica rice cultivars. Plant S d<br />
160:405-414.<br />
Davenport, R. J. 2001. Syngenta finishes, consortium goes on. Science 291:807.<br />
Devos, K. M ., <strong>and</strong> M. D. Gale. 1997. Comparative genetics in the grasses. P lant M ol<br />
B io l 35:3-15.<br />
Drakakaki, G., R Christou, <strong>and</strong> E. Stoger. 2000. Constitutive expression o f soybean<br />
ferritin cDNA In transgenic wheat <strong>and</strong> rice results in increased Iron levels in<br />
vegetative tissues but not in seeds. Transgen. Res. 9:445-452.<br />
Duan, X ., X . Li, Q. Xue, M . Abo-el~Saad, D. Xu, <strong>and</strong> R. Wu. 1996. Transgenic rice<br />
plants harboring an introduced potato proteinase inhibitor II gene are insect<br />
resistant. Nat. B iotechnol 14:494-498.<br />
Freeling, M . 2001, Grasses as a single genetic system: reassessment 2001. P lant Physiol<br />
125:1191-1197.<br />
Fujimoto, H., K. Itoh, M. Yamamoto, J. Kyozuka, <strong>and</strong> K. Shim am oto. 1993. Insect<br />
resistant rice generated by induction o f a modified 5 -endotoxin gene o f Bacillus<br />
thuringiensis. Bio<strong>technology</strong> (N. Y J 11:1151-1155.<br />
Goff, S. A. 1999. <strong>Rice</strong> as a model for cereal genomics, Curr. Opin. P lant B io l 2:86-89.<br />
Goto, F., T. Yoshihara, N. Shigemoto, S. Told, <strong>and</strong> F. Takaiwa. 1999. Iron fortification<br />
o f rice seed by the soybean ferritin gene. Nat. B iotechnol 17:282-286.
<strong>Rice</strong> Bio<strong>technology</strong> 215<br />
Greco, R., B. F. Ouwerkerk, C. Sallaud, A. Kohli, L. Colombo, P. Puifdomenech,<br />
E, Guiderdoni, P. Christou, H. C. Hoge, <strong>and</strong> A. Pereira. 2001.Transposon inser-<br />
tional mutagenesis in rice. P lant Physiol. 125:1175-1177.<br />
Guerinot, M. L. 2000. The green revolution strilces gold. Science 287:241-243.<br />
Gura, T. 1999. New genes boost rice nutrients. Science 285:994-995.<br />
Han, S., Z. Wu, H. Yang, R. Wang, Y. Yie, L. Xie, <strong>and</strong> P. Tien. 2000. Ribozyme-<br />
mediated resistance to rice dwarf virus <strong>and</strong> the transgenic silencing in the progeny<br />
o f transgenic rice plants. Transgen. Res. 9:195“ 203.<br />
Harushima, Y , M. Yano, A. Shom ura, M. Sato, T. Shimano, Y. Kuboki, T. Yamamoto,<br />
S. Y. Lin, B. A. Antonio, A. Parco, H. Kajiya, N. Huang, K. Yamamoto, Y. Naga-<br />
mura, N. Kurata, G. S. Kush, <strong>and</strong> X Sasaki. 1998. A high-density rice genetic linkage<br />
map with 2275 markers using a single F? population. Genetics 148:479-494.<br />
Hayakawa, X , Y. Zhu, K. Itoh, Y. Kimura, X Izawa, K. Shimamoto, <strong>and</strong> S. Toriyama.<br />
1992. Genetically engineered rice resistant to rice stripe virus, an insect-transm itted<br />
virus. Proc. N a tl Acad. Set. USA 89:9865-9869.<br />
Henry, R. J. 1997. Practical A pplications o f P lant M olecular Biology. Chapman 8c Hall,<br />
London.<br />
Hiei, Y , S. Ohta, X Komari, <strong>and</strong> X Kumashiro. 1994. Efficient transform ation o f<br />
rice (O ryza sativa L.) mediated by A grobacterium <strong>and</strong> sequence analysis of the<br />
boundaries o f the T-DNA. P lant /. 6:271-282.<br />
Hiei, Y , X. Komari, <strong>and</strong> Kubo, T. 1997. Transformation of rice mediated by A grohac-<br />
terium tum efaciens. P lant M o l B io l 35:205-217.<br />
Hirochika, H. 1997. Retrotransposons o f rice: their regulation <strong>and</strong> use for genome<br />
analysis. P lant M o l B io l 35:231-240.<br />
Hodges, T. K., J. Peng, L. A. Lyznik, <strong>and</strong> D. S. Koetje. 1991. Transformation <strong>and</strong><br />
regeneration of rice pi'otoplasts. In G. S. Khush <strong>and</strong> G. H. Toenniessen (eds.), <strong>Rice</strong><br />
B io<strong>technology</strong> CAB International, Wallingford, Oxon, Engl<strong>and</strong>, pp. 157-174.<br />
Hong, G. 1997. A rapid <strong>and</strong> accurate strategy for rice contig map construction by<br />
com bination o f fingerprinting <strong>and</strong> hybridization. P lant M o l B io l 35:129-133.<br />
Hoshida, H. X Y , X Hibino, Y. Hayashi, A. Tanaka, X Takabe, <strong>and</strong> X Talcabe. 2000.<br />
Enhanced tolerance to salt stress in transgenic rice that overexpresses chloroplast<br />
glutamine synthetase. P lant M o l B io l 43:103-111.<br />
Irie, K., H. Hosoyama, T. Talceuchi, K. Iwabuchi, H. Watanabe, M. Abe, K. Abe, <strong>and</strong><br />
S, Arai. 1996. Transgenic rice established to express corn cystatin exhibits strong<br />
inhibitory activity against insect gut proteinases. P lant M o l B io l 30:149-157.<br />
Izawa, X , <strong>and</strong> K. Shimamoto. 1996. Becoming a model plant: the importance o f rice<br />
to plant science. Trends P lant Set. 1:95-99.<br />
Izawa, X , X Ohnishi, X Nakano, N. Ishida, H. Enoki, J. Hashimoto, K. Itoh, R. Terada,<br />
C. Wu, C. Miyazake, X Endo, S. lida, <strong>and</strong> K. Shimamoto. 1997. Transposon<br />
tagging in rice. P lant M o l B io l 35:219-229.<br />
Jeon, J. S,, S. Lee, K. H. Jung, S. H. Jun, D. H. Jeong, J. Lee, C. Kim, S. Jang, K. Yang,<br />
J. Nam, K. An, M. J. Han, R. J. Sung, H. S. Choi, J. H. Yu, J. H Choi, S. Y<br />
Cho, S. S.Cha, S. I. Kim, <strong>and</strong> G. An. 2000. X-DNA insertional mutagenesis for<br />
functional genomics in rice. P lant J. 22:561- 570.<br />
Kinoshita, X 1986. St<strong>and</strong>ardization o f gene symbols <strong>and</strong> linkage maps in rice. In <strong>Rice</strong><br />
Genetics. Proc. o fth ein t. R ice Genetics Symp. May 27-31 1985. International <strong>Rice</strong><br />
Research Institute, M anila, pp. 215-228.<br />
Kishitani, S., X Xakanami, M . Suzuki, M. Oikawa, S, Yokoi, M . Ishitani, A, M. Alvarez-<br />
Nakase, X Takabe, <strong>and</strong> X Takabe. 2000. Compatibility o f glycinebetaine in rice
Üi<br />
plants: evaluation using transgenic rice plants with a gene for peroxisomal betaine<br />
aldehyde dehydrogenase from barley. P lant Cell Environ. 23:107-114.<br />
Krishnamurthy, K. <strong>and</strong> M. J. Giroux. 2001. Expression o f wheat'puroindoline genes<br />
in transgenic rice enhances grain softness. Nat. B iotechn ol 19:162-166.<br />
Ku, M., D. Cho, X. Li, D. M . Jiao, M . Pinto, M, Miyao, <strong>and</strong> M. Matsuoka. 2001. Introduction<br />
o f genes encoding C4 photosynthesis enzymes into rice plants; physiological<br />
consequences. N ovartis Found. Symp. 236:100-116.<br />
Kurata, N., Y. Nagamura, K. Yamamoto, Y. Harushima, N. Sue, J. Wu, B. Antonio,<br />
A. Shom ura, T. Shimizu, S. Lin, T. Inoue, A. Fukuda, T. Shimano, Y. Kubold,<br />
T. Toyama, Y. Miyamoto, T. Kirihara, K. Hayasaska, A. Miyao, L. M onna, H.<br />
Zhong, Y. Tamura, Z. Wang, T. M om m a, Y. Umehara, M. Yano, T. Sasaki, <strong>and</strong><br />
Y. M inobe. 1994. A 300 kilobase interval genetic map o f rice including 883 expressed<br />
sequences. Nat. G enet 8:365-372.<br />
Kurata, N., Y. Umehara, H. Tanoue, <strong>and</strong> T. Sasaki. 1997. Physical mapping o f the rice<br />
genome with YAC clones. P lant M o l B io l 35:101-113.<br />
Lucca, P., J. Wunn, R. E Hurrell, <strong>and</strong> I. Potrykus. 2000. Development o f iron-rich rice<br />
<strong>and</strong> improvement o f its absorption in humans by genetic engineering. J. Plant<br />
Nutr. 23:1983-1988.<br />
Lynch, P. T., R. P. Finch, M . R. Davey, <strong>and</strong> E. C. Cocldng. 1991. <strong>Rice</strong> tissue culture <strong>and</strong><br />
its application. In G. S. Khush <strong>and</strong> G. H. Toenniessen (eds.), <strong>Rice</strong> Bio<strong>technology</strong>.<br />
CAB International, Wallingford, Oxon, Engl<strong>and</strong>, pp. 135-155.<br />
Maddll, D. J. 1999. Genome analysis <strong>and</strong> breeding. In K. Shimamoto (ed.), M olecular<br />
B iology o f <strong>Rice</strong>. Springer-Verlag, Tokyo, pp. 17-41.<br />
Maheswaran, M ., P. K. Subudhi, S. N<strong>and</strong>i, J. C. Xu, A. Parco, D. C. Yang, <strong>and</strong> N, Huang.<br />
1997. Polymorphism, distribution, <strong>and</strong> segregation o f AELP markers in a doubled<br />
haploid rice population. Theor, A p p l Genet. 94:39-45.<br />
Martienssen, R. A. 1998. Functional genomics: probing plant gene function <strong>and</strong> expression<br />
with transposons. Proc. N a tl Acad. Sci. USA 95:2021-2026.<br />
Matsumura, H., Nirasawa, H., <strong>and</strong> Terauchi, R, 1999. Technical advance: transcript<br />
profiling in rice ( Oryza sativa L.) Seelings using serial analysis o f gene expression<br />
(SAGE). P lant J. 20:719-726.<br />
M cCallum, C. M ., L. Comai, E. A. Greene, <strong>and</strong> S. Henikoff. 2000. Targeted screening<br />
for induced mutations. Nat. B iotechnol 18:455-457.<br />
McCouch, S. R., G. Kochert, Z. H. Yu, Z. Y. Wang, G. S. Khush, W. R. Cofftnan,<br />
<strong>and</strong> S. D. Tanksley. 1988. Molecular mapping o f rice chromosom es. Theor. Appl<br />
Genet. 76:815-829.<br />
McCouch, S. R., X. Chen, O. Panaud, S. Temnylch, Y, Xu, Y. G. Cho, N. Huang,<br />
T. Ishii, <strong>and</strong> M. Blair. 1997. Microsatellite marker development, mapping <strong>and</strong><br />
applications in rice genetics <strong>and</strong> breeding. P lant M o l B io l 35:89-99.<br />
Nagamura,Y., B. A. Antonio, <strong>and</strong> T, Sasald. 1997. <strong>Rice</strong> molecular genetic map using<br />
RELPs <strong>and</strong> its application. P lant M o l B io l 35:79-87.<br />
Nayak, P., D, Basu, S. Das, A. Basu, D. Ghosh, N.A. Raraakrishnan, M . Ghosh, <strong>and</strong><br />
S, K. Sen. 1997. Transgenic elite in dica rice plants expressing CrylAc 8-endotoxin<br />
o f Bacillus thuringiensis are resistant against yellow stem borer (Scirpophaga incertulas).<br />
Proc. N atl Acad. S ci USA 94:2111-2116.<br />
Niizeld, H., <strong>and</strong> K. Oono. 1968. Induction o f haploid rice plant from anther culture.<br />
Proc. Jpn, Acad. 44:544-557.
Vi<br />
<strong>Rice</strong> Bio<strong>technology</strong> 217<br />
Normile, D. 1999, Rockefeller to end network after 15 years o f success. Science 286:<br />
1468-1469.<br />
Oard, J. H., S. D. Linscombe, M. P. Braverman, F. Jodari, D, C. Blouin, M. Leech,<br />
A. Kohli, P. Vain, J. C. Cooley, <strong>and</strong> P. Christou. 1996. Development, field evaluation,<br />
<strong>and</strong> agronomic performance o f transgenic herbicide resistant rice. M ol.<br />
Breed. 2:359-368.<br />
Pennisi, E. 2000. Stealth genome rocks rice researchers. Science 288:239-241.<br />
Pinto, Y. M ., R. A. Kok, <strong>and</strong> D. C. Baulcombe. 1999, Resistance to rice yellow mottle<br />
virus (RYMV) in cultivated African rice varieties containing RYM V transgenes.<br />
Nat. B iotechn ol 17:702-707.<br />
Potrykus, I. 2001. Golden rice <strong>and</strong> beyond. P lant P hysiol 125:1157-1161.<br />
Rao, K. V., IC S. Rathore, T. K. Hodges, X. Fu, E, Stoger, D.Sudhakar, S. Williams,<br />
P. Christou, M . Bharathi, D. P, Bown, K, S. Powell, J, Spence, A. M. Gatehouse,<br />
<strong>and</strong> J. J. Gatehouse. 1998. Expression o f snowdrop lectin (GNA) in transgenic<br />
rice plants confers resistance to rice brown planthopper. P lant J. 15:469-477.<br />
Rashid, H., S. Yokoi, K. Toriyama, <strong>and</strong> K. Hinata. 1996. Transgenic plant <strong>production</strong><br />
mediated b y A grohacterium in indica rice. P lant Cell Rep. 15:727-730,<br />
Redona, E. D., <strong>and</strong> D .}. Mackill. 1996. Molecular mapping o f quantitative trait loci in<br />
japónica rice. G enom e 39:395-403.<br />
Rood, M. A. 2000. Herbicide resistance: two technologies are on track for 2001. <strong>Rice</strong><br />
J. 103:8-10.<br />
Rood, M . A. 2001. Almost here: herbicide-resistant rice varieties expected. <strong>Rice</strong> J,<br />
104:16-18.<br />
Roy, M ., <strong>and</strong> R. Wu. 2001. Arginine decarboxylase transgene expression <strong>and</strong> analysis<br />
o f environmental stress tolerance in transgenic rice. P lant S ei 160:869-875.<br />
Rutger, J. N. 1992. Impact o f m utation breeding in rice: a review. M utât. Breed. Rev.<br />
8:1-23,<br />
Saijo, Y., S. Hata, J. Kyozuka, K. Shimamoto, <strong>and</strong> K. Izui. 2000. Over-expression o f<br />
a single Ca^+-dependent kinase confers both cold <strong>and</strong> salt/drought tolerance on<br />
rice plants. P lant J. 23:319-327.<br />
Sakamoto, A., Alia, <strong>and</strong> N. Murata. 1998. M etabolic engineering o f rice leading to<br />
biosynthesis o f glycinebetaine <strong>and</strong> tolerance to salt <strong>and</strong> cold. P lant M o l B io l<br />
38:1011-1019. [erratum: 40(1):195],<br />
Sanchez, A. C., D. S. Brar, N, Huang, Z. Li, <strong>and</strong> G. S. Khush. 2000. Sequence tagged<br />
marker-assisted selection for three bacterial blight resistance genes in rice. Crop<br />
S ei 40:792-797.<br />
Sanícula, S., M. P. Braverman, E Jodari, S. D. Linscombe, <strong>and</strong> J. H. Oard. 1997. Evaluation<br />
o f giufosinate on rice (O ryza sativa) transformed with the BAR gene <strong>and</strong><br />
red rice (Oryza sativa). W eed Technol 11:70-75.<br />
Sasaki, T. <strong>and</strong> G. M oore (eds.). 1997. Oryza: From M olecule to Plant. Kluwer Academic,<br />
Dordrecht, The Netherl<strong>and</strong>s.<br />
Schaffrath, U., E Mauch, E. Freydl, P. Schweizer, <strong>and</strong> R. Dudler. 2000. Constitutive<br />
expression o f the defense-related R irlb gene in transgenic rice plants confers<br />
enhanced resistance to the rice blast fungus M agnaporthe grísea. P lant M o l B io l<br />
43:59-66.<br />
Sharma, A., R. Sharma, M . Im am ura, M. Yamakawa, <strong>and</strong> H. Machii. 2000. Transgenic<br />
expression o f cecropin B, an antibacterial peptide from B om byx m orí, confers<br />
enhanced resistance to bacterial leaf blight in rice. FEBS Lett. 4 84:7-11.
The <strong>Rice</strong> Plant<br />
Song, W., G. Wang, L. Chen, H. Kim, L. Pi, T. Holsten, J. Gardner, B. Wang, W. Zhai,<br />
L. Zhu, C. Fauquet, <strong>and</strong> P. Ronald. 1995. A receptor kinase-like protein encoded<br />
by the rice disease resistance gene, X a2 L Science 270:1804^1806.<br />
Stevens, J. E. 1994. Japan picks a winner in the rice genome project. Science 266:1186-<br />
1187.<br />
Sudhakar, D., X, Fu, E. Stoger, S. Williams, J. Spence, D. P. Brown, M . Bharathi, J. A.<br />
Gatehouse, <strong>and</strong> P. Christou. 1998. Expression <strong>and</strong> im munoiocalisation o f the<br />
snowdrop lectin, GNA in transgenic rice plants. Transgen. Res. 7:371-378.<br />
Suzuki, S,, N. Murai, J. N. Burnell, <strong>and</strong> M . Aral. 2000. Changes in photosynthetic<br />
carbon flow in transgenic rice plants that express C4-type phosphoenolpyruvate<br />
carboxykinase from U rochloa panicoides. P lant Physiol. 124:163-172.<br />
Takahashi, M ., H. Nakanishi, S. Kawasaki, N. K. Nishizawa, <strong>and</strong> S. M ori. 2001. Enhanced<br />
tolerance of rice to low iron availability in alkaline soils using barley<br />
nicotianamine aminotransferase genes. Nat. Biotechnol. 19:466-469.<br />
Tang, K., X. Sun, Q. Hu, A. Wu, C. Lin, H. Lin, R. M. Twyman, P. Christou, <strong>and</strong> T. Feng.<br />
2001. Transgenic rice plants expressing the ferredoxin-Uke protein (A PI) from<br />
swfeet pepper show enhanced resistance to X anthom onas oryzae pv. oryzae. Plant<br />
Sei. 160:1035-1042.<br />
Tu, J., G. Zhang, K. Datta, C. Xu, Y. He, Q. Zhang, <strong>and</strong> G. S. Khush. 2000. Field perform<br />
ance o f transgenic elite com mercial hybrid rice expressing B acillus thuringiensis<br />
d-endotoxin. N a t Biotechnol. 18:1101-1104.<br />
Wang, W., W. Zhai, M . Luo, G. Jiang, X. Chen, X. Li, R. A. W ing, <strong>and</strong> L. Zhu. 2001.<br />
Chromosome l<strong>and</strong>ing at the bacterial blight resistance gene X a4 locus using a<br />
deep coverage rice BAG library. M ol. G en. Genet. 265:118-125.<br />
Wang, Z. X., M. Yano, U. Yamanouchi, M . Iwamoto, L. M onna, H. Hayasaka, Y. Kata-<br />
yose, <strong>and</strong> T. Sasaki. 1999. The Pib gene for blast resistance belongs to the nucleotide<br />
binding <strong>and</strong> leucine-rich repeat class o f plant disease resistance genes.<br />
P lan t}. 19:55-64.<br />
Wunn, J., A. Kloti, P. K. Burlchaardt, G. C. Biswas, K. Launis, V. A. Iglesias, <strong>and</strong><br />
I. Potrykus. 1996. Transgenic Índica rice breeding line IR 58 expressing a synthetic<br />
crylA (b)^ene from Bacillus thuringiensis provides effective insect pest control.<br />
Bio<strong>technology</strong> (N. Y.) 14:171-176.<br />
Yamamoto, K., <strong>and</strong> T. Sasald. 1997. Large-scale EST sequencing in rice. P lant M ol<br />
Bio/. 35:135-144.<br />
Yamazaki, M., H. Tsugawa, A. Miyao, M. Yano, J. Wu, S. Yamamoto, T. Matsumoto,<br />
T. Sasald, <strong>and</strong> H. Hirochika. 2001. The rice retrotransposon T osl7 prefers low-<br />
copy-nuraber sequences as integration targets. M o l G en et G enom . 265:336-344.<br />
Yano, M ., <strong>and</strong> T. Sasaki. 1997. Genetic <strong>and</strong> molecular dissection o f quantitative traits<br />
in rice. P lan t M o l B io l 35:145-153.<br />
Ye, X., S. Al-Bablili, A. Kloti, J. Zhang, P. Lucca, P. Beyer, <strong>and</strong> I. Potrykus. 2000. Engineering<br />
the provitamin A (ß -carotene) biosynthetic pathway into (carotenoid-<br />
free) rice endosperm. Science 287:303-305.<br />
Yoshimura, A., O. Ideta, <strong>and</strong> N. Iwata. 1997. Linkage map o f phenotype <strong>and</strong> RFLP<br />
markers in rice. P lant M o l B io l 35:49-60.<br />
Yoshimura, S., U. Yamanouchi, Y. Katayose, S. Told, Z. X . Wang, I. Kono, N. Kurata,<br />
M . Yano, N. Iwata, <strong>and</strong> T. Sasaki. 1998. Expression o f X a J, a bacterial blight-<br />
resistance gene in rice, is induced by bacterial inoculation. Proc. N a tl Acad. Set<br />
¡754 95:1663-1668.
<strong>Rice</strong> Bio<strong>technology</strong> 219<br />
Yuan, Q ., J. Qtiackenbush, R. Sultana, M. Pertea, S. L, Salzberg, <strong>and</strong> C. R. Buell. 2001.<br />
<strong>Rice</strong> bioinformatics; analysis o f rice sequence data <strong>and</strong> leveraging the data to<br />
other plant species. P lan t Physiol 125; 1166-1174.<br />
Zhang, Q. <strong>and</strong> S. Yu. 2000. M olecular marker-based gene tagging <strong>and</strong> its impact<br />
on rice improvement. In J. S. N<strong>and</strong>a (ed.), <strong>Rice</strong> B reeding an d Genetics: Research<br />
Priorities an d Challenges. Science Publishers, Enfield, NH, pp. 241-270.<br />
Zhang, H. B., <strong>and</strong> R. A. W ing. 1997. Physical mapping o f the rice genome with BACs.<br />
P lant M o l B io l 35; 115-127.<br />
Zhang, S., L. Chen, <strong>and</strong> S. A. Goff. 2001. Regulation o f gene expression by small<br />
molecules in rice. Novartis Found. Symp. 236:85-95.<br />
Zhao, B., W. M. Wang, X. W. Zheng, C. L. Wang, B. J. M a, Q. Z. Xue, L. H. Zhu, <strong>and</strong><br />
W. X. Zhai. 2000. Introduction o f wide spectrum rice bacterial blight resistance<br />
gene Xa21 into two-line genic male sterile rice variety pei’aai 64S (in Chinese).<br />
Sheng Wu G ong C heng X ue B a o 16:137-141.
Chopter<br />
2.6<br />
Studies on <strong>Rice</strong> Allelochemicals<br />
Agnes M. Rim<strong>and</strong>o <strong>and</strong> Stephen 0. Duke<br />
U SD A -A R S<br />
Natural Products Utilization Research Unit<br />
University of Mississippi<br />
University, Mississippi<br />
INTRODUCTION<br />
RICE ALLELOPATHY RESEARCH<br />
Secondary Metabolites Identified in <strong>Rice</strong><br />
Bioassays<br />
Systematic Isolation of Allelochemicals<br />
MECHANISMS OF ACTION OF POTENTIAL RICE ALLELOCHEMICALS<br />
SUMMARY AND OUTLOOK<br />
REFERENCES<br />
INTRODUCTION<br />
Weeds cause reductions in rice yield <strong>and</strong> quality, as well as problems associated with<br />
harvesting. Since weeds remain one o f the biggest problems in rice <strong>production</strong>, greater<br />
attention is being directed toward their control (Agrow, 2000). <strong>Rice</strong> allelopatliy <strong>and</strong><br />
its utilization as a possible means o f controlling weeds drew attention after observations<br />
o f this interaction occurring in the field. In field experiments carried out in<br />
1988 on 5000 rice accessions from the USDA-ARS germplasm collection in Stuttgart,<br />
Arkansas, 191 had activity against the aquatic weed Heteranthera limosa (ducksalad)<br />
(Dilday et aL, 1991). Field studies done the following year revealed an additional<br />
156, from a different set o f 5000 accessions, which inhibited ducksalad growth within<br />
a 10-cm radius. Subsequently, other field experiments were conducted to evaluate<br />
allelopathic potential o f rice cultivars against other com m on rice weeds. At the In <br />
ternational <strong>Rice</strong> Research Institute (IR R I) in the Philippines in the 1995 wet season<br />
<strong>and</strong> 1996 dry season, 111 rice cultivars were tested for allelopathic activity against<br />
\i-<br />
<strong>Rice</strong>: Origin, History, Technology, <strong>and</strong> Production, edited by C, Wayne <strong>Smith</strong><br />
ISBN 0-47 H34516-4 © <strong>2003</strong> John Wiley & Sons, Inc.<br />
221
222 The <strong>Rice</strong> Plant<br />
Echinochloa crus-galU (barnyardgrass) <strong>and</strong> Trianthema. portulacastrum (horse purselane)<br />
(Olofsdotter et aL, 1999). In Korea, 134 rice cultivars (24 cultivars from IRRI,<br />
30 improved cultivars, <strong>and</strong> 80 traditional Korean cultivars) were grown in the summer<br />
o f 1996 in a study evaluating allelopathic potential against barnyardgrass under<br />
local growing conditions (Kim <strong>and</strong> Shin, 1998). Similar studies were conducted in<br />
Egypt during 1993-1996 to screen 1000 cultivars for activity against barnyardgrass<br />
<strong>and</strong> Cyperus difformiSi the two m ost troublesome rice weeds in Egypt (Hassan et al.,<br />
1998). Prom studies over the last decade, 3.5% of rice accessions are estimated to have<br />
allelopathic activity against one or m ore weed species (Olofsdotter et a l, 2000), Some<br />
o f the highly aEelopathic cultivars identified are listed in Table 2.6. 1.<br />
Various bioassays (discussed in the section “Bioassays”) have been developed to<br />
screen or survey cultivars for allelopathic activity, to validate observed activity in the<br />
field, to demonstrate allelopathy in controlled laboratory conditions to distinguish<br />
between aUelopathy <strong>and</strong> com petition, to underst<strong>and</strong> the mechanism(s) o f action of<br />
allelochemicals, <strong>and</strong> also to isolate <strong>and</strong> identify allelochemicals in rice. In laboratory<br />
studies, allelopathic activity has been measured in term s o f inhibition o f germination<br />
or growth (reduction o f shoot <strong>and</strong>/or root length <strong>and</strong> weight), or general phytotoxicity<br />
to the test plant. In several instances, the test plant used was Lactuca sativa (lettuce),<br />
but a few assays have used target weeds (e.g., barnyardgrass or ducksalad).<br />
A number o f secondary metabolites have been identified in rice. These are mostly<br />
phenolic, aromatic acid, <strong>and</strong> benzene derivatives; long-chain hydrocarbons <strong>and</strong> fatty<br />
acids <strong>and</strong> their derivatives; <strong>and</strong> a few sterols. These compounds are almost ubiquitous<br />
in plants. A group o f tricyclic diterpenes, known as momilactones <strong>and</strong> oryzalexins,<br />
which may be unique to rice, has been isolated. Some o f the momilactones<br />
<strong>and</strong> oryzalexins have been reported to be highly phytotoxic. However, more work<br />
needs to be done to refer unequivocally to the momilactones <strong>and</strong> oryzalexins as the<br />
allelochemicals in rice.<br />
In this chapter we summarize the known research on rice aUelopathy. M ost of<br />
this inform ation has been generated during the past decade. Although considerable<br />
progress in our underst<strong>and</strong>ing has been made, much work remains to be done before<br />
we fuUy underst<strong>and</strong> this process in rice <strong>and</strong> can utilize it for more environmentally<br />
benign weed management.<br />
RICE ALLELOPATHY RESEARCH<br />
Secondary Metabolites Identified in <strong>Rice</strong><br />
I .:<br />
It is a generally accepted definition that allelochemicals are secondary metabolites<br />
released by a source plant into the environment, causing detrimental effects on the<br />
growth <strong>and</strong> development o f recipient plant(s) (<strong>Rice</strong>, 1984). Secondary metabolites, so<br />
caUed because they are not essential for plant growth <strong>and</strong> function, comprise a wide<br />
range o f organic molecules broadly classified based on the <strong>origin</strong> o f their metabolism.<br />
These include compounds such as alkaloids, terpenoids, steroids, carotenoids, polyacetylenes,<br />
prostagl<strong>and</strong>ins, cyclic peptides, quiñones, flavonoids, stilbenes, anthocyanins,<br />
lignans, condensed tannins, <strong>and</strong> hydrolyzable tannins (Robinson, 1991;<br />
Robbers et al., 1996). Several secondary metabolites have been identified in rice.<br />
Those that are reported are limited to the fatty acids, long-chain hydrocarbons, sterols,
Studies on <strong>Rice</strong> Allelochemicals 223<br />
TABLE 2.6. K<br />
<strong>Rice</strong> Accessions Showing Strong Allelopathic Activity in Field Tests<br />
Idenfiiictition O rigin " W eed Tested^ Reference<br />
AC 1423 n.n Barnyardgrass Kim <strong>and</strong> Shin (1998)<br />
n.r. Barnyardgrass Olofsdotter et al. (1999)<br />
n.r. Trianthema portulacastrum Olofsdotter et al. (1999)<br />
AUS 257 n.r. Barnyardgrass Olofsdotter et al. (1999)<br />
B1293 B-PN-24 PhilippincvS Ducksalad Dilday et al. (1996)<br />
BasmatiPAK 134 Pakistan Ducksalad Dilday et al. (1996)<br />
Cl-Selection 63 Bangladesh Barnyardgrass Hassan et al. (1998)<br />
Cica4 Brazil Ducksalad Dilday et al. (1996)<br />
Cin Shun China Ducksalad Dilday et al. (1996)<br />
Cuba 65 58A United States Redstem Dilday et al. (1998)<br />
Cuba 65 V 58 United States Redstem Dilday et al. (1998)<br />
Pou U Lan China Ducksalad Dilday et al. (1996)<br />
Dukr India Cyperus dijformts L. Hassan étal. (1998)<br />
Dulatom 298 (Dulai' 298-2) Pakistan Redstem Dilday et al. (1998)<br />
Hwei Ju China Ducksalad Dilday et al. (1996)<br />
lARI 10560-India India Ducksalad Dilday et al. ( 1996)<br />
lET 11754 India Cyperus difformis L. Hassan et al. (1998)<br />
II ziu Korea Redstem Dilday étal. (1998)<br />
India AC1423 India Ducksalad Dilday et al. (1996)<br />
IR14-6-2-1 Philippines Redstem Dilday et al. (1998)<br />
IR52 16 7 3 Philipines Redstem Dilday et al. (1998)<br />
IR52 30 6 2 Philippines Redstem Dilday et al. (1998)<br />
IR75 69 3 Philippines Redstem Dilday et al. (1998)<br />
IR781-497-2-3 Philippines Ducksalad Dilday et al. (1996)<br />
IR800-17-1-3 Philippines Redstem Dilday et al. (1998)<br />
IR1044 56 Philippines Redstem Dilday et al. (1998)<br />
IR2006-P-3~33^2 Philippines Cyperus difformis L. Hassan et al. (1998)<br />
Juma 10 Dominican Republic Ducksalad Dilday et al. (1996)<br />
Kim Rad F-87 Japan Cyperus difformis L. Hassan et al. (1998)<br />
Kingmen T.C. China Ducksalad Dilday et al. (1996)<br />
Kuoketsumochi n.r. Barnyardgrass Kim <strong>and</strong> Shin (1998)<br />
Mamoriaka Brazil Ducksalad Dilday et al. (1996)<br />
Melanothrix Japan Ducksalad Dilday et al. (1996)<br />
Musashikogaiie n.r. Barnyardgrass Kim <strong>and</strong> Shin (1998)<br />
Mushkan 41 India Redstem Dilday et al. (1998)<br />
NSSL 10/28 STP 8 United States Ducksalad Dilday et al. (1996)<br />
OR-131-5-8 India Barnyardgrass Hassan et al. (1998)<br />
0. glaherritna Pakistan Ducksalad Dilday et al. (1996)<br />
P828 Pakistan Ducksalad Dilday et al. (1996)<br />
RP 2271-433-231 Argentina Barnyardgrass Hassan et al. (1998)<br />
Saloia 2 n.r. Barnyardgrass Kim <strong>and</strong> Shin (1998)<br />
San Chiao Tswen China Ducksalad Dilday et al (1996)<br />
Santi Pak-209 Pakistan Ducksalad Dilday et al. (1996)<br />
Shuang-Chiang- 30-21 Taiwan Ducksalad Dilday et al (1996)<br />
T65/2X’^TN-1 Philippines Ducksalad Dilday et al (1996)<br />
Taichung 176 Taiwan Ducksalad Dilday et al. (1998)<br />
Taichung Native 1 China Ducksalad Dilday et al. (1996)<br />
n.r. Barnyardgrass Kim <strong>and</strong> Shin (1998)<br />
continued
224 The <strong>Rice</strong> Plant<br />
T A B LE 2.6.1.<br />
R ice A c c e ssio n s S h o w in g S tro n g A lle lo p a t h ic A ctivity in F ie ld Tests (Continued)<br />
Identification Origin“ Weed Tested^ Reference<br />
n.r. Trianthema portulacastrum Olofsdoter et al. (1999)<br />
Takanenishiki n.r. Barnyardgra.ss Kim <strong>and</strong> Shin (1998)<br />
Tang gan n.r. Barnyardgrass Kim <strong>and</strong> Shin (1998)<br />
Tono Brea 439 Dominican Republic Ducksalad Dildayet al. (1996)<br />
UN GU6 Korea Redstem Dildayet al. (1998)<br />
USSRY2178 6 Pakistan Ducksalad Dilday et al. (1994)<br />
Woo Co Chin Yu Taiwan Ducksalad Dilday et al (1996)<br />
n.r. Barnyardgrass Kim <strong>and</strong> Shin (1998)<br />
n.r. Barnyardgrass Olofsdotter et al. (1999)<br />
YH-1 n.r. Barnyardgrass Kim <strong>and</strong> Shin (1998)<br />
Yunlen 5 China Barnyardgrass Hassan et al (1998)<br />
Yunlen 6 Philippines Barnyardgrass Hassan et al (1998)<br />
"n.r., <strong>origin</strong> of accession tested was not reported.<br />
'’Barnyardgrass, Echinochloa crus-galU (L.) P, Beauv; Duclcsaladj H eteranfhera limosa (Sw.) Willd.; Redstem,<br />
A m m ania coccínea Rottb.<br />
tric)'clic diterpenes, cinnam ic <strong>and</strong> benzoic acids, <strong>and</strong> derivatives thereof (Figures 2.6.1<br />
to 2.6.5).<br />
The existence o f rice phytotoxins was reported years before allelopathic cultivars<br />
were identified. Chou <strong>and</strong> Lin (1976) observed decrease in productivity o f tlie second<br />
rice crop in a paddy containing residues from the first crop. Aqueous extracts of<br />
decomposing rice residues in soil inhibited radicle growth o f lettuce <strong>and</strong> rice seeds <strong>and</strong><br />
retarded root initiation o f mungbeans. Phytotoxins in the aqueous extract were separated<br />
by paper chromatography. Comparison o f Jiy values o f spots in the extract with<br />
synthetic st<strong>and</strong>ards indicated that the phytotoxins were cis- (1) <strong>and</strong> frans-p-coumaric<br />
(2), p-hydroxybenzoic (3), o-hydroxyphenylacetic (4), ferulic (5), <strong>and</strong> vanillic acids<br />
(6) (Figure 2,6.1). Several compounds in the extract were not identified. In addition<br />
to compounds 1 to 6, o-coum aric (7) <strong>and</strong> syringic (8) acids were identified also as<br />
ph)lotoxins from paddy soil (Chou <strong>and</strong> Chiou, 1979).<br />
The effect o f decomposing rice straw on the growth o f Anahaena cylindrica (a<br />
blue-green alga) has also been studied (<strong>Rice</strong> et al., 1980). The phytotoxic phenolic<br />
acids 2 ,4 , 5, <strong>and</strong> 6 (Figure 2.6.1) were reported to inhibit growth o f the alga at 10^^<br />
M concentration. At 10^''^ M, only 5 showed significant inhibition, while at this concentration,<br />
3 significantly stimulated growth. The com bined phenolics (each at 10“^<br />
M ) caused severe chlorosis <strong>and</strong> completely eliminated N 2 fixation in A. cylindrica. It is<br />
interesting to note that whereas individual compounds were shown to inhibit growth,<br />
extracts o f the highest straw-soil concentration stimulated growth o f the alga.<br />
In vitro studies have implicated volatile compounds as the allelopathic constituents<br />
from rice (Yang <strong>and</strong> Futsuhara, 1991). <strong>Rice</strong> callus co-cultured with soybean<br />
callus reduced the growth rate o f soybean by more than 100-fold. The experimental<br />
system was designed to prevent the influence o f diffusion through culture medium,<br />
<strong>and</strong> therefore only volatiles could influence growth. Results indicated that growth<br />
inhibition was due not to ethylene produced by the rice callus, but to other volatile<br />
(allelopathic) compounds. Inhibition was found to be specific to soybean <strong>and</strong> other<br />
legumes but not to the solanaceous species tested. It was found also, that treatment of
Studies on <strong>Rice</strong> Allelochemicals 225<br />
R Ri Ra Rs Ri Rj R3 R< R<br />
3 OH H OH H 2 H H OH H OH<br />
6 OH OCHs OH H 5 H OCH3 OH H OH<br />
8 OH OCH3 CH OCH3 7 OH H H H OH<br />
9 OH OH H H 10 H H OH OH OH<br />
12 H H OH H 36 H H H H OCH2CH=CHPIie<br />
13 OH H OCH3 OH 37 H H OH OCH3 OCH3<br />
35 H H OH OCH3 59 H H H H H<br />
49 OCH3 H OH OCHj<br />
58 H H H CHjCHj<br />
■ ^^C O O H<br />
.CH3<br />
NH<br />
40 R = H<br />
41 R = iPr<br />
r i i<br />
V<br />
Ri Ra Ra<br />
4 OH H R( R2 R3<br />
11 H OH 57 H CH3 CHjCHa<br />
61 OH H OH<br />
COOH<br />
Figure 2.6,1, Pfienol, oromatic add, <strong>and</strong> benzene derivatives identifedinrice: ], as-p-coumaric odd;<br />
2, te-p-coumoric; 3, p-hydroxybenzoic acid; 4, o-hydroxyphenylrfcetic acid; 5, ferulic acid; 6, vanillic acid;<br />
7, o^coumoric acid; 8, syringicacid; 9,3-hydroxybenzoîcacid; 10,3,4-difiydroxycinnamic; 11,4-hydroxyphefiylacetic<br />
acid; 12,4-hydroxybenzaldehyde; 13,3-hydroxy-4“metlio)iybenzoic; 33,2(3//)-benzofuranone;<br />
35.4- hydroxy-3-methoxybenzaldehyde; 36, cinnam-cinnamate; 37,3-(4-hydroxy-3-methoxypheriyl)-2-propenoic<br />
add methyl ester; 40, iV-phenylbenzenamine; 41,4-(l-niethylethyl}-iV-phenvlbenzenaniine;<br />
42.2.4- di(l-phenyleihy!)phenol; 49, d-hydroxy-S-niethoxybenzoic acidmethyl ester;<br />
57,1-ethyl-3,5'dimethylbenzene; 58,4-ethylbenzaldehyde; 59, cinnamaldéhyde; 61,2-methyl-l,4-benzenediol.<br />
33<br />
the supernatant fluid from rice cell cultures with 0.05 M KOH greatly increased the<br />
inhibitory effect o f the volatile compounds. Further analysis o f the volatiles was not<br />
carried out.<br />
Phenolic acids were found in higher levels in extracts o f water into which allelopathic<br />
rice (PI No. 294400 or PI No. 277414) was transplanted <strong>and</strong> left for 48<br />
hours. Levels o f phenolic acids were higher than in similar extracts o f water exposed
OCH3<br />
27<br />
'CHO<br />
CONH,<br />
60<br />
,OCH,<br />
CHO<br />
43<br />
'OCH,<br />
19<br />
OCHa<br />
46<br />
OH<br />
'OH<br />
OCHa<br />
Figure 2.6.2, Hydrocarbons, fatty acids, <strong>and</strong> derivatives identified in rice; 15, tetradecanoic odd; 16, valeric acid;<br />
17, hexodecanoic acid methyl ester; 18,3,7,11,15-tetromethyI-2'hexadecen-l-ol;<br />
19,6,10,14-trimethyi-2-pentodecanone; 2 0,9'hexodecenoic acid; 27,2-decenaI; 28,2,4-decadienal;<br />
29,9-oxo-nonanoicacid methyl ester; 30, dodecanamide; 32, tetradeconol; 43, methyltetrodecanoate;<br />
44, methylpentadecanoQte; 46, phylol; 54,2-hydroxy-î-(hydroxymethyl)-hexiKlecanoicocid ethyl ester;<br />
60,12-methyltrideconoic acid methyl ester; 65,7-hexodecenoic acid methyl ester.<br />
6S<br />
to a nonallelopatliic (Rexm ont) cultivar (M attice et al,, 1998). The compounds were<br />
identified by gas chromatography-mass spectrom etry (GC/MS) as 3-hydroxybenzoic<br />
(9), 3,4-dihydroxycinnamic (10), 4'hydroxyphenylacetic (11) acid, <strong>and</strong> compounds<br />
2 <strong>and</strong> 4 (Figure 2.6.1). It was noted that at the time o f transplanting rice to water,<br />
ducksalad gro\vth was more controlled in soil containing allelopathic rice than in<br />
soil containing nonallelopathic rice. W lien soil containing the allelopathic accession<br />
(PI No. 312777) <strong>and</strong> soil containing the nonallelopathic cultivar (Rexm ont) were<br />
analyzed before flooding, higher levels o f 4~hydroxybenzaldehyde (12), 3-hydroxy-4-<br />
methoxybenzoic acid (13), stearic acid (14), tetradecanoic acid (15), valeric add (16),<br />
as well as compounds 2 <strong>and</strong> 3, were found in the form er (Figures 2.6.1 <strong>and</strong> 2.6.2).
Studies on <strong>Rice</strong> Alielochemicals 227<br />
OCH,<br />
OCH3<br />
14<br />
COOH<br />
OCH3<br />
C0NH2<br />
a “ - 1 -CHîCHïCHîCHa<br />
Figure 2,6.2. {conf.) Hydromrbons, iatly acids, <strong>and</strong> derivatives identified in rice; 14, stearic add;<br />
2 1 ,9,12,-ûctadecadienoic acid methyl ester; 2 2 ,9,12,15-octadecotrienoic acid methyl ester; 31, V-octadecenemide;<br />
34, octadecanoic acid methyl ester; 39, isothiocyonatocydohexane; 45, methylheptadecanoate; 47, methyl<br />
9-ectadecenoat6; 4 8,2-meîhylcycloheptanone; 51,1 é-methylheptodecanoic acid methyl ester; 53, eicosanoic acid<br />
methyl ester; 55,2-hydroxy-1-hydroxymethyl-9,12-octadecadienoic acid ethyl ester; 56,9,12,15-octadecatrienal; 62,<br />
octadecane; 6 3 ,1-eicosanol; 64, cis-l-buiyl-2-methylcyclQpropane; 6 7 ,3-eicosene; 6 9 ,12-octadecenoicacid methyl<br />
ester,<br />
64<br />
Semipure fractions, obtained by colum n chromatography of plant tissue extracts<br />
<strong>and</strong> root exudates o f the allelopathic rice cultivai' Kouketsumochi, which were in <br />
hibitory to barnyardgrass in a bioassay, were anal)czed by GC/MS (Kim <strong>and</strong> Kim,<br />
2000). Several long-chain fatty acid esters, aldehydes, ketones, sterols, benzene derivatives,<br />
<strong>and</strong> amines were identified in these fractions. From the active column fraction<br />
o f the leaf extracts hexadecanoic acid methyl ester (17), 3,7,11,15-tetram ethyl-2-<br />
hexadecen-l-ol (18), 6,10,14-triraethyl-2-pentadecanone (19), 9-hexadecenoic acid<br />
(20), 9,12,-octadecadienoic acid methyl ester (21), 9,12,15'0ctadecatrienoic ad d<br />
methyl ester (22), 2,6,10-trimethyl-14-ethylenepentadecane (23), ergost-5-en-3(j6)-ol
228 The Rite Plant<br />
"‘‘rr-<br />
■■I'l<br />
Figure 2.6.3. Sterols identified in rice: 24, er90St-5-en-3(i!))-ol; 25, stigmasterol; 26, j8-sitosterol;<br />
38,24(Z}-m6thy!-25-honiocholesterol; 50, pre9na-5,20-dien-3(6)-ol; 70, cholest-5-en-3(j6)-ol.<br />
(24), stigmasterol (25), <strong>and</strong> jS-sitosterol (26) were identified (Figures 2.6.2 <strong>and</strong> 2.6.3),<br />
From the active fractions of root extracts 2-decenal (27), 2,4-decadienal (28), 9-<br />
oxo-nonanoic acid methyl ester (29), dodecanamide (30), 9-octadecenamide (31),<br />
tetradecanal (32), 2(3H )-benzofuranone (33), octadecanoic acid methyl ester (34),<br />
4-hydroxy-3-methoxybenzaldehyde (35), cinnam -cinnam ate (36), 3-(4-hydroxy-3-<br />
m ethoxyphenyl)-2-propenoic acid methyl ester (37), 2 4 ( 2 ) -m ethyl-25-homocholesterol<br />
(38), isothiocyanatocyclohexane (39), N-phenylbenzenamine (40), 4-(l-m eth "<br />
ylethyl)-W“phenylbenzenamine (41), 2,4-di(l-phenyletliyl)phenol (42), <strong>and</strong> compounds<br />
17, 24, 25, <strong>and</strong> 26 were identified (Figures 2.6.1 to 2.6.3, <strong>and</strong> 2.6.5).<br />
Compounds identified from the active fractions o f the whole plant extract o f Kouket-<br />
sumochi included methyl tetradecanoate (43), methyl pentadecanoate (44), methyl<br />
heptadecanoate (45), phytol (46), methyl 9-octadecenoate (47), 2-methylcyclohep-<br />
tanone (48), 4-hydroxy-3-methoxybenzoic acid methyl ester (49), pregna-5,20-dien-<br />
3(;S)-ol(50), 16-methylheptadecanoic add methyl ester (51),loliolide (52), eicosanoic<br />
acid methyl ester (53), 2-hydroxy-1-(hydroxymethyl)-hexadecanoic acid ethyl ester<br />
(54), 2-hydroxy-1 -hydroxymethyl-9,12-octadecadienoic acid ethyl ester (55), 9,12,15-
Studies on <strong>Rice</strong> Allelochemicals 229<br />
78 R < C o H<br />
79 R = 0<br />
Figure 2.6.4. Tricyclic diterpenes identified in rice; 71, momilactore A; 72, momilactone B; 73, momilactone C;<br />
74, ineketone; 7 6 ,3-diliydromomilacfone A; 77, acetyl momilactone B; 78, oryzalexin A; 79, oryzolexin C.<br />
HO.,<br />
52<br />
68<br />
76<br />
Figure 2.6.5. Miscellaneous compounds identified in rice: 52, loliolide; 68, dehydroabietic acid; 75,<br />
S(+)-detiydrovomiioliol.<br />
octadecatrienal (56), <strong>and</strong> compounds 17,2 0 ,2 1 ,2 2 , <strong>and</strong> 34 (Figures 2.6.1 to 2.6.3 <strong>and</strong><br />
2.6.5).<br />
Compounds identified from the acidic fractions o f root exudates o f Kouket-<br />
sum ochi determined to be most inhibitory to barnyardgrass growth were 1 -etliyl-3,5-<br />
dimethylbenzene (57), 4-ethylbenzaldehyde (58), cinnamaldéhyde (59), 12~methyl-<br />
tridecanoic acid methyl ester (60), 2-methyl-1,4-benzenediol (61), octadecane (62),<br />
1-eicosanol (63), ds-l-biityl-2-m ethylcyclopropane (64), 7-hexadecenoicacid methyl<br />
ester (65), 9,12-octadecadienoic acid (66), 3-eicosene (67), dehydroabietic acid (68),<br />
12-octadecenoic acid methyl ester (69), cholest-5"en-3(yS)-ol (70), as well as com <br />
pounds identified from whole plant, root, <strong>and</strong> leaf extracts (i.e., 16, 17, 34, 44, 45,<br />
<strong>and</strong> 47) (Figures 2.6.1 to 2.6.3, <strong>and</strong> 2.6.5).
230 Th0 Ri(e Plant<br />
iií't;<br />
The aforementioned compounds generally are present in many other plants.<br />
Some of these compounds hare been identified as being associated with allelopathic<br />
effects o f some crops <strong>and</strong> other plant species, such as barley {Hordeum vulgare) (Everall<br />
<strong>and</strong> Lees, 1996), wheat {TriUcum aesttvum) (Tanaka et al., 1990), ChamaccypaHs<br />
obtusa, <strong>and</strong> Cryptomeria japónica (Ishii <strong>and</strong> Kadoya, 1993). Perhaps the phytotoxic<br />
secondary metabolites that can be considered unique to rice are the tricarbocyclic<br />
diterpenes possessing a pimaradiene carbon skeleton (e.g., momilactones, oryzalex-<br />
ins, ineketone). M omilactones A (71) <strong>and</strong> B (72) (Figure 2.6.4) were first identified<br />
as the inhibitory components from rice husks [momi is the Japanese word for husk)<br />
of Oryzij sativa L. cv. Koshihikari, a poorly germinating cultivar, in investigations on<br />
the influence o f compounds present in the seed coat affecting seedling germination<br />
(Kato et al., 1973). M omilactones A <strong>and</strong> B inhibited growth o f rice roots at less<br />
than 100 ppm. In further studies, four other inhibitory compounds were identified:<br />
momilactone C (73), ineketone (74), S(H-)-dehydrovomifoliol (75), <strong>and</strong> 2 (Figures<br />
2.6.1 <strong>and</strong> 2.6.4). Compound 2 was weakly inhibitory (Tsunakawa et al., 1976; Kato<br />
et al., 1977a). Structural modifications o f 71 <strong>and</strong> 72 (Kato et al., 1977b) showed that<br />
3-dihydromomÜactone A (76) <strong>and</strong> acetylmomilactone B (77) (Figure 2.6.4) had the<br />
highest activity, with germination rates o f 8 <strong>and</strong> 0 percent, respectively. Reduction of<br />
the vinyl group on ring C diminished activity (i.e., germination o f 72 <strong>and</strong> 83% for 71<br />
<strong>and</strong> 72 with vinyl groups reduced, respectively) (Kato et al., 1977a).<br />
M omilactones A <strong>and</strong> B also were isolated <strong>and</strong> identified as phytoalexins from<br />
ultraviolet-irradiated, dark-grown rice coleoptÜes (Cartwright et al., 1981). Earlier<br />
studies showed that the fungicide 2,2-dichloro-3,3-dimethylcyclopropanecarboxylic<br />
acid (W L 28325) increases the capacity o f rice to synthesize 71 <strong>and</strong> 72 (Figure 2.6.4)<br />
in response to infection (Cartwright et ak, 1977). Other abiotic factors, such as the<br />
chloroacetamide herbicides pretilachlor <strong>and</strong> butachlor (Tamogarni et al., 1995), gib-<br />
berellic acid, sodium azide, penicillin (Ghosal <strong>and</strong> Purkayastha, 1987), cerebrosides<br />
A <strong>and</strong> C (Koga et al., 1998), CuCb (Kodama et al., 1988), <strong>and</strong> methionine (Nakazato<br />
et al., 2000), when applied to wounded rice leaves also induce accumulation o f 71.<br />
In one investigation, momilactones were not detected even in highly concentrated<br />
extracts from healthy <strong>and</strong> Pyricularia oryzae-infected rice leaves o f several<br />
cultivars (Matsuyama, 1983). In another study, m omilactones were again absent from<br />
blast-infected rice leaves pretreated with the fungicide probenazole, but other anticonidial<br />
germination substances were isolated (Shimura et a l, 1981). Subsequent<br />
research enabled the isolation o f antifungal compounds from P. oryzae-infected rice<br />
leaves referred to as S-1 (C2oH3202> mol. wt. 304) (Matsuyama <strong>and</strong> W akimoto, 1985),<br />
14-6M (C20H 3QO2, mol. wt. 302), 14-7M (C 20H 30O 2, mol. wt. 302), <strong>and</strong> 12-7M (M atsuyama<br />
<strong>and</strong> Wakimoto, 1988).<br />
It is worth m entioning that other phy to alexins have been isolated from rice [e.g.,<br />
oryzalexins A to C (Kono et a l, 1985), D (Sekido et a l, 1986), E (Kato et al., 1993), F<br />
(Kato et a l, 1994), <strong>and</strong> S (Kodama et a l, 1992a); sakuranetin (Kodama et a l, 1992b);<br />
<strong>and</strong> phytocassanes A to D (Koga et a l, 1995) <strong>and</strong> E (Koga et a l, 1997)]. Except for<br />
sakuranetin, which is a flavanone, these phytoalexins are tricyclic diterpenes: The<br />
momilactones <strong>and</strong> oryzalexins A to F are pimarane-type diterpenes, oryzalexin S is a<br />
stemarane-type diterpene, <strong>and</strong> the phytocassanes have the cassane skeleton.<br />
The content o f 71 <strong>and</strong> 72 (Figure 2.6.4) in rice straw (cv. Haresugata) grown in<br />
a greenhouse was determined at different stages o f seedling growth <strong>and</strong> found to be<br />
maximal 120 days after seeding, gradually decreasing thereafter (Lee et a l, 1999a).<br />
.1^ 1
Studies on <strong>Rice</strong> Allelochemícals 231<br />
í'<br />
The level o f 71 was always higher than that o f 72. An 80% aqueous methanol extract<br />
o f straw harvested 180 days after seeding contained 3.80 <strong>and</strong> 2.01 /ig/g dry weight<br />
o f 71 <strong>and</strong> 72, respectively. The authors found that the momilactones are extractable<br />
easUy into water even though these compounds are hydrophobic. An aqueous extract<br />
o f the straw contained 1.01 <strong>and</strong> 0.81 /ug/g dry weight o f 71 <strong>and</strong> 72, respectively.<br />
This cultivar was grown in a paddy field, <strong>and</strong> straw was harvested at full m aturity<br />
extracted, <strong>and</strong> fractionated in studies to identify the phytotoxic constituents (Lee<br />
etal., 1999b). Following chromatographic procedures, oryzalexin A (78) an d -C (79),<br />
71, <strong>and</strong> 72 (Figure 2,6.4) were isolated. The inhibitory activity o f these compounds<br />
against the weeds Amaranthus Uvidus L., Digitaria sanguinalisy <strong>and</strong> Poa annua was<br />
tested. Greatest activity was found with 72, inhibiting germination o f A. Uvidus by<br />
50% at 5 (mM. At 50 ¡xM, 72 inhibited root <strong>and</strong> shoot growth o f D. sanguinalis <strong>and</strong><br />
seed germination o f P, annua by more than 50% . From these results, these phytotoxins<br />
(allelochemicals) were postulated to affect germination <strong>and</strong> growth o f susceptible<br />
weeds <strong>and</strong> crops when rice straw is left in the field after harvesting.<br />
Bioassays<br />
À few bioassays have been developed to study rice allelopathy in more controlled<br />
(laboratory) environments. The plant box method was developed by Fujii (1995)<br />
to discriminate <strong>and</strong> identify allelopathy from com petition (for nutrients, light, <strong>and</strong><br />
water). This method employs a mixed culture in agar medium. Briefly described, test<br />
(allelopathic) plants were grown in s<strong>and</strong> culture for 1 to 2 months, the roots washed<br />
with distilled water, <strong>and</strong> those with root dry weights o f 100 to 300 mg were selected<br />
<strong>and</strong> transplanted into agar medium in plant tissue culture boxes (60 by 60 by 100 mm ,<br />
L by W by H ). Roots were confined in separating tubes set in place in one corner o f the<br />
box. The upper plant parts were fastened in place using transparent cellophane tape.<br />
Agar medium (low-temperature gelatinizing, 0.5% w/v, 250 m L) was gently poured<br />
into the box, <strong>and</strong> after congealing (within 15 minutes), seeds o f receiver/acceptor<br />
species (Lactuca sativa L. cv. Great Lakes 366) were introduced, placed 10 cm apart.<br />
The box was covered with black plastic film to avoid root phototropism. The surface<br />
was covered with a transparent film <strong>and</strong> held for 5 to 6 days at 23 to 25®C, which<br />
allowed lettuce radicles to grow <strong>and</strong> reach the bottom o f the box. Allelopathy was<br />
assessed by measuring lettuce radicle lengths. This method was used to screen 189<br />
rice cultivars for allelopathic potential in Japan (Fujii, 1993).<br />
A different laboratory screening procedure (called relay seeding) was established<br />
at IRRl to distinguish allelopathy from com petition (Navarez <strong>and</strong> Olofsdotter, 1996)<br />
(Figure 2.6,6). <strong>Rice</strong> seedlings were grown for 7 days in two rows on perlite in a petri<br />
dish contained inside a plastic germination box. The petri dish was lined with a bridge<br />
filter paper strip for continuous infusion o f water from the germination box. Barn-<br />
yardgrass seeds were then relay-seeded (i.e., in between the two rows o f rice seedlings)<br />
<strong>and</strong> the two species allowed to grow for 10 days. The lengths o f barnyardgrass roots<br />
were then used to indicate rice allelopathic activity. This procedure has produced<br />
qualitative results similar to those obtained from field tests (Olofsdotter et al., 1997).<br />
Mattice et al. (1998) employed a continuous root exudate trapping system <strong>and</strong><br />
a bench system in their endeavor to study root exudates from allelopathic rice. An<br />
XAD-4 trapping resin was used. Solid-phase (Cis, charcoal, styrene divinyl benzene)
232 The Rite Plant<br />
Figure 2.6.6.<br />
Reloy seeding method.<br />
extraction methods were also tried in trapping the chemicals used in this study, all of<br />
which were commercially available <strong>and</strong> reportedly allelochemically active. Extraction<br />
with ethyl ether gave the best recovery o f the phenolic acids m onitored in this study.<br />
A simple laboratory experiment was performed in our laboratory to demonstrate<br />
allelopathic activity of a known allelopathic rice cultivar. <strong>Rice</strong> was grown in sterilized<br />
potting soil in plastic boxes (310 by 170 by 90 m m , L by W by H) in a growth chamber<br />
for 30 days. <strong>Rice</strong> plants were removed, <strong>and</strong> soil was collected <strong>and</strong> transferred to culture<br />
dishes (100 by 80 mm, D by H ). Barnyardgrass seedlings were grown in these soils<br />
under growth chamber culture for 21 days. Barnyardgrass plants grown in soil that<br />
supported growth o f the allelopathic rice cultivar were shorter than those grown in<br />
soil from the nonallelopathic cultivar (Figure 2,6.7).<br />
Kim <strong>and</strong> Kim (2000) utilized a petri dish assay method in efforts to isolate the<br />
allelochemicals from allelopathic rice cv. Kuoketsumochi. Solutions o f colum n chromatography<br />
fractions at specific concentrations were applied to a 5.5-cm petri dish<br />
lined with W hatm an No. 2 filter paper. Solvent was evaporated, <strong>and</strong> 20 barnyardgrass<br />
seeds that had been sterilized with 1% sodium hypochlorite were placed on the filter<br />
paper; 1 m L of water was added, <strong>and</strong> seeds were incubated under 20,000 lux at 28°C<br />
Figure 2.6.7. Effect of soil from allelopathic <strong>and</strong> commercial<br />
(nonallelopathic) rice on growth of barnyordgrass.
Studies on <strong>Rice</strong> Allelochemicols 233<br />
for 6 days. Inhibitory activity was measured by comparing shoot <strong>and</strong> root length with<br />
same-age plants not exposed to the fractions. Dilday et al. (1996) also developed<br />
a petri dish assay to study the effect of rice root <strong>and</strong> leaf tissue water extracts on<br />
ducksalad. Ducksalad seeds were placed on filter paper in a petri dish (100 by 15 m m ),<br />
covered with a thin layer o f soil, <strong>and</strong> treated with 10 m L o f the root <strong>and</strong>/or leaf tissue<br />
water extract. Seeds were germinated in a growth chamber at 25“C with a 12-hour<br />
photoperiod. Lee at al. (1999b) employed a similar bioassay system in the isolation o f<br />
alíelo chemicals from O, sativa cv. Haresugata, except that glass vials (15 by 45 mm ,<br />
D by H) were used instead o f petri dishes. This assay required smaller quantities o f<br />
extracts, which is an advantage over the petri dish assay.<br />
Glass vials (30-m L, 2,5 cm inside diameter) were used in testing the effects o f<br />
O . sativa cv. Tsuldnohikai on Monochoria vaginalis (Burm. R ) Presl. var. plantaginea<br />
(Roxb.), a serious annual broadleaf weed in paddy fields in Asia (Kawaguchi et al.,<br />
1997). M. vaginalis seeds were germinated in vials (25 seeds/vial) containing 5 m L o f<br />
aqueous extracts (or water as a control) o f rice seeds, husks,, <strong>and</strong> seedlings inside a<br />
sealed polyethylene container incubated at 27 ± 1“C in the dark for 120 hours. Seeds<br />
with radicle lengths less than 3 m m indicated allelopathy effect.<br />
Independently, Matsuo <strong>and</strong> Shibayama developed the M onochoria test method<br />
(1996), <strong>Rice</strong> plants were incubated in plastic tubes (30 by 80 m m , D by H ), filled with<br />
sieved paddy soil, for 1 m onth. The rice plants developed a root-soil colum n within<br />
the tubes, <strong>and</strong> were taleen out o f the tubes <strong>and</strong> laid in petri dishes (90 m m diameter),<br />
M. vaginalis seeds that had broken dormancy were then sown on the surface o f the<br />
rice root-soil column. Water was added to the petri dish, <strong>and</strong> the system was left at<br />
room temperature. Inhibitory activity o f rice cultivars was evaluated by measuring<br />
the length o f the first leaf, coleoptile, <strong>and</strong> seminal root o f M. vaginalis seedlings<br />
10 days after sowing. The numbers o f dead or partly dead seedlings were counted<br />
to determine the lethal effects of the rice. Subsequent experiments demonstrated<br />
the necessity o f measuring hypocotyl root form ation o f M. vaginalis seedlings in<br />
evaluating allelopathic activity o f rice (Matsuo <strong>and</strong> Shibayama, 1998). This method<br />
involved germinating seeds in petri dishes, collecting seedlings at various intervals for<br />
up to 360 hours, fixing the seeds with a fixing agent, <strong>and</strong> observing the hypocotyl hair<br />
form ation as well as other growth parameters under the microscope.<br />
Kim et al. (2000) used a water extraction method to screen allelopathic cultivars.<br />
<strong>Rice</strong> samples (whole plants, leaves, roots, or seeds) were extracted with water for<br />
Specified periods o f time at 26 db 2®C. The water extract was filtered through filter<br />
paper <strong>and</strong> then loaded, at certain concentrations, onto 90-m m petri dishes containing<br />
10 harnyardgrass seeds, Barnyardgrass roots were evaluated 10 days after incubation<br />
in a growth chamber with 12-hour photoperiod at 26 ± 2°C, In these screening<br />
studies, agar medium <strong>and</strong> relay-seeding test methods were conducted, but the water<br />
extraction m ethod was found m ost reliable in determining the allelopathic among<br />
their particular set o f cultivars.<br />
Systematic Isolation of Allefochemicals<br />
Although several secondary metabolites have been reported, it is not certain that<br />
these are truly the compounds responsible for allelopathy in rice. W ork still has to<br />
be done to classify these compounds conclusively as allelochemicals. Identification
The <strong>Rice</strong> Plant<br />
of unknown secondary metabolites is often a daunting task but can be carried out<br />
in systematic ways (Duke et al,> 2000). A bioassay-guided isolation procedure is the<br />
suitable procedure to follow in identifying unknown compounds for which the biological<br />
activity being sought is known. This method is appropriate for searching<br />
allelochemicals in rice. For the success o f such an endeavor, it is necessary to choose<br />
an appropriate bioassay system, cultivar to extract, proper extraction procedure(s),<br />
<strong>and</strong> target receiver/test species. Some researchers have reported on results from their<br />
studies that alluded to the importance of considering these factors/elements, <strong>and</strong> these<br />
will be discussed subsequently.<br />
It is apparent from the preceding section that different allelopathic activity test<br />
methods have been developed to suit research objectives <strong>and</strong> goals. For a bioassay-<br />
guided isolation, ideally, the assay should be simple, rapid, econom ical, sensitive,<br />
reproducible, specific, <strong>and</strong> relevant. M ost of the assays noted above required 6 days,<br />
the Monochoria assay o f Kawaguchi et al. (1997), 90 days or more. The sensitivity<br />
<strong>and</strong> reproducibility o f the test method are critical to establish allelopathy^ as different<br />
bio assays sometimes give conflicting results. For example, with tlie relay-seeding<br />
method the rice cultivar Dongjinbyeo caused about 70% inhibition o f barnyardgrass<br />
root growth, whereas it was classified as nonallelopathic in the water extract bioassay<br />
(Kim <strong>and</strong> Kim, 2000), Conversely, this cultivar showed the highest activity in the agar<br />
medium test. The target species to use in the bioassay also is im portant in assessing<br />
activity. Lettuce is used in most phytotoxicity testing, but it is a very sensitive plant <strong>and</strong><br />
often gives false positive results (e.g., Quayyum et al., 1999). In laboratory tests, the<br />
rice cultivars Rexm ont <strong>and</strong> Palmyra, which did not have observable allelopathic activity<br />
in the field, reduced lettuce seed germination <strong>and</strong> radicle elongation significantly<br />
when highly concentrated extracts were tested (Dilday et al., 1996). There is evidence<br />
that a cultivar can be allelopathic only to some weed species. Aqueous extracts of<br />
field-grown rice (cv. Tsukinohikari) inhibited seed germination <strong>and</strong> growth o f watergrass<br />
{Echinochloa oryzicola Vasing) but promoted seed germination o f Monochoria<br />
korsakowii (Kawaguchi et al., 1997). The proper method(s) o f extracting samples to<br />
be subjected to bioassay-guided isolation must not be overlooked. Kawaguchi et al.<br />
(1997) found that when aqueous extracts of rice were partitioned with ethyl acetate,<br />
the inhibitory constituents were extracted into the organic solvent while the stimulatory<br />
constituents remained in the aqueous fraction. We obtained similar results in<br />
our studies with rice (Rim<strong>and</strong>o et al., 2001).<br />
Although many rice cultivars have been reported as allelopathic, the choice of a<br />
particular cultivar to be studied could greatly influence the success o f allelochem-<br />
ical discovery efforts. Taichung Native 1 (T N I) st<strong>and</strong>s out as a good representative.<br />
It has allelopathic activity against barnyardgrass, ducksalad, horse purselane<br />
(Trianthema portulacastrum)^ <strong>and</strong> redstem (Ammania sp.). It also carries the gene<br />
for semidwarfism (Olofsdotter et al., 1997), which is a desirable agronomic trait.<br />
Taichung Native 1 also consistently showed high activity in all tests conducted by<br />
Kim <strong>and</strong> Kim (2000) <strong>and</strong> had the highest inhibitory activity in the agar medium<br />
method.<br />
Another im portant factor to be considered is the plant part to be studied. Extracts<br />
from seeds, whole plants, leaves, roots, <strong>and</strong> root exudates, as well as soil that supported<br />
growth of rice, have been shown to have growth inhibitory effects on weeds tested<br />
(e.g., Chou <strong>and</strong> Lin, 1976; Dilday et al., 1996; Kim <strong>and</strong> Kim, 2000). Growth inhibitory<br />
constituents have been isolated from rice husks (Kato et al., 1973) <strong>and</strong> straw (Lee et al.,
■"'-we<br />
Studies on <strong>Rice</strong> Aileiociietnicais 235<br />
1999a <strong>and</strong> b ). However, it must be pointed out that allelopathy in rice was dem onstrated<br />
by clear zones (absence of weeds growing) around the rice plant in paddy<br />
fields (Dilday et al., 1991; Kim <strong>and</strong> Shin, 1998; Olofsdotter et al., 1999). It is highly<br />
likely, therefore, that the allelochemicals are secreted from <strong>and</strong> can be found in the<br />
highest concentrations in the roots. This is not unexpected, as some allelochemicals<br />
have already been isolated from roots [e.g., sorgoleone from Sorghum bicolor (Netzly<br />
<strong>and</strong> Butler, 1986) <strong>and</strong> saponins from Medicago sativa (Waller et al., 1993)]. Root<br />
exudates have been invoked to explain the allelopatliy o f Centura diffusa (Callaway<br />
<strong>and</strong> Aschehoug, 2000). Fractions from root extracts o f rice (cultivar Kuoketsumochi)<br />
were found to have higher inhibitory activity against barnyardgrass than were leaf<br />
extract fractions (Kim <strong>and</strong> Kim, 2000). Similarly, root extracts inhibited ducksalad<br />
germination significantly more than did leaf extracts (Dilday et al., 1996),<br />
Finally, in growing <strong>and</strong> collecting rice for activity-guided isolation, it is necessary<br />
to obtain a sample that is devoid o f artifacts. Roots from soil-grown rice may have<br />
accompanying microorganisms that may be sources o f biologically active secondary<br />
metabolites o r may have transformed compounds fi"om rice.<br />
Preliminary work done in our laboratory has demonstrated the usefulness o f<br />
a bioassay-guided m ethod in the isolation o f allelochemicals from T N I (Rim<strong>and</strong>o<br />
et al., 2001). <strong>Rice</strong> was grown hydroponically, <strong>and</strong> roots were collected, extracted, <strong>and</strong><br />
subsequently fractionated. Phytotoxic activity was followed using a 24-well microtiter<br />
plate microbioassay. This m ethod enabled the elim ination o f p-coum aric acid <strong>and</strong><br />
directed attention to fractions lacking p-coum aric acid, a reported rice aUelochemical.<br />
In our assay, p-coum aric acid had an effect on the growth o f lettuce at concentrations<br />
of 3 m M <strong>and</strong> higher (Figure 2.6.8). It had an effect on barnyardgrass roots at 5 mM<br />
<strong>and</strong> on shoots at 10 mM . Other fractions <strong>and</strong> compounds isolated were m uch m ore<br />
inhibitory than p-coum aric acid (Rim<strong>and</strong>o et al., 2001). These results suggest that<br />
other constituent(s) are responsible for the allelopathic activity o f this cultivar.<br />
Figure 2.6.8. Effect of p-coumaric acid on lottuce: a, control; b, control<br />
+ solvent; c, 1 nuiM; d, 2 m/H; e, 3 mil/l; f, 5 m^M; g, 10 mM p-coumoric<br />
acid.
The <strong>Rice</strong> Plant<br />
W ork by Lee et al. (1999b), which resulted in isolation o f the phytotoxins momilactones<br />
A <strong>and</strong> B> <strong>and</strong> o f oryzalexins A <strong>and</strong> C in pure form from rice straw, may<br />
be considered the best example of a bioassay-guided isolation. However, it would<br />
have been proven convincingly that these compounds are the true allelochemicals<br />
in rice had they been identified in roots <strong>and</strong> soil. Production o f m omilactones <strong>and</strong><br />
oryzalexins has also been reported to be induced by both biotic <strong>and</strong> abiotic factors in<br />
rice cultivars that are not known to be allelopathic. Moreover, the absence o f mom i<br />
lactones in healthy <strong>and</strong> even in blast-infected rice has also been reported (Matsuyama,<br />
1983). From these reports it is difficult to determine whether these compounds are the<br />
naturally occurring rice allelochemicals (phytotoxins) or phytoalexins or both. This<br />
matter needs to be resolved.<br />
MECHANISMS OF ACTION OF POTENTIAL RICE ALLELOCHEMICALS<br />
Knowing the mechanism o f action of allelochemicals could be very useful in deciding<br />
which com pound(s) a,breeder or molecular biologist would like to see in increased<br />
quantity in order to improve the allelopathic activity o f rice cultivars. Knowing the<br />
molecular target site can help to confirm that stunting or death o f weeds is due to a<br />
particular allelochemical. For example, if an alíelo chemical is loiown to inhibit mitosis,<br />
this symptom can be evaluated in affected plants. If this symptom is not found, it<br />
is unlikely that this allelochemical is involved in the crop’s allelopathic phenotype,<br />
Furthermore, for toxicological reasons, more emphasis might be placed on those<br />
compounds that target molecular sites found only in plants than on compounds with<br />
both plant <strong>and</strong> m am malian target sites.<br />
Another im portant aspect o f loiowing the mode o f action o f crop allelochemicals<br />
is the value of this inform ation in-determining the crop’s mechanism o f resistance<br />
to the phytotoxin, For example, in sorghum species that produce the allelochemical<br />
sorgoleone (Nimbal et al., 1996), Üiere is no resistance in the producing plant at<br />
the molecular site of this photosystem II inhibitor (M . Czarnota, unpublished data).<br />
Thus, the sorgoleone-producing plant must have mechanisms for avoiding the concentration<br />
o f this phytotoxin becom ing inhibitory in cells with chloroplasts.<br />
One paper has been published on the mode o f action of rice allelopathy. Lin<br />
et al, (2000) examined levels of extractable enzyme activities from barnyardgrass<br />
after treatm ent with crude extracts of allelopathic rice cultivars. They found lower<br />
levels o f several enzyme activities but did not look for in vitro effects that might<br />
have established a primary site o f action. As pointed out by Devine et a l (1993),<br />
descriptions of secondary <strong>and</strong> tertiary effects o f phytotoxins on plants have resulted<br />
in many publications, but rarely provide insight into mechanisms o f action.<br />
As stated in the preceding section, numerous rice phytotoxins have been reported.<br />
However, there is no conclusive proof that any o f them are partially or solely<br />
responsible for apparent allelopathy in rice. As with m ost allelochemicals, the molecular<br />
site o f action o f m ost o f them is unknown. However, literature exists to provide<br />
a start in examination o f their modes o f action.<br />
Several phenolic acids are com m on in rice. These include p-hydroxybenzoic acid,<br />
vanillic acid, p-coum aric acid, ferulic acid, 2~phenylpropionic add, 4-hydroxypheny-<br />
lacetic acid, 4-hydroxycinnamÍc acid, <strong>and</strong> 3-phenylproprionic acid (Chou <strong>and</strong> Lin,<br />
1976; Mattice et a l, 1998). Although mildly phytotoxic in bioassays without soil (e.g.,
Studies on <strong>Rice</strong> Allelochemitols 237<br />
Duke et al., 1983; Lydon <strong>and</strong> Duke> 1989), m ost o f these compounds are ubiquitous in<br />
plant tissues, making it unlikely that they have a significant role in allelopathy. Some<br />
have tried to avoid this conclusion by claiming the existence o f synergism among<br />
the compounds (e.g., Einhellig <strong>and</strong> Rasmussen, 1978); however, proper analysis for<br />
synergism was not conducted in tliese studies, <strong>and</strong> in the one study that was conducted<br />
properly (Duke et al., 1983), additive <strong>and</strong> even antagonistic effects were found. P roof<br />
o f synergism is rare in studies with phytotoxins (e.g., Streibig et al., 1999) or any<br />
other compounds with biological action. Knowledge o f the molecular mechanisms o f<br />
allelochemicals should provide a basis for the prediction o f synergisms. For example,<br />
if two compounds have overlapping binding sites on a molecular tai'get site, synergism<br />
is highly unlikely. In this case, tire less active o f the two compounds may antagonize<br />
the more active one.<br />
M ore m ode-of-action research probably has been conducted on phenolic acids<br />
than on any other class o f allelochemicals because they are so com m on <strong>and</strong> easy to<br />
obtain. They do not appear to have a strong effect on any m etabolic process. By strong<br />
effect, we mean compounds that are active growth inhibitors at concentrations o f 100<br />
fiM or lower <strong>and</strong> have pronounced in vitro effects at 1 ¡xM or lower. There are many<br />
plant-derived phytotoxins, such as sorgoleone <strong>and</strong> some o f its analogs (Rim<strong>and</strong>o et<br />
al., 1998), that meet the criteria for a highly active allelochemical.<br />
We will not catalog every effect that has been reported for phenolic acids but<br />
will provide a few examples. At relatively high concentrations (0.5 to 0.75 m M ),<br />
ferulic acid marginally inhibits photosynthesis when applied to leaves, apparently<br />
tlirough indirectly reducing stomatal conductance (Einhellig, 1995). Reductions in<br />
water potential <strong>and</strong> stomatal conductance have been reported in several crop species<br />
by phenolic acids at 0.15 to 0.5 m M concentrations (Einhellig et al., 1985, Barkosky<br />
<strong>and</strong> Einhellig, 1993; Einhellig, 1995). The effects o f several phenolic acids on seed<br />
germination at high concentrations were found to be similar to those o f water stress<br />
(Duke et al., 1983), suggesting that they might affect membrane functions. This result<br />
is in agreement with the results o f Bailee (1985) <strong>and</strong> Alsaadawi et al. (1986), who<br />
found that phenolic acids influence ion uptake, <strong>and</strong> Lyu et al. (1990), who showed<br />
that phosphorus uptake by cucum ber is inhibited by ferulic, vanillic, <strong>and</strong> p-coum aric<br />
acids. More recent findings indicate that tire effect o f ferulate on phosphorus uptake<br />
is due to interactions outside the root or on the root surface (Lehman <strong>and</strong> Blum,<br />
1999). Van Suraere et al. (1971) found that simple cinnam ic <strong>and</strong> benzoic acids inhibit<br />
uptake o f phenylalanine. Balke (1985) found salicylate to inhibit K+ uptake, to depolarize<br />
membranes, <strong>and</strong> to reduce ATP content of roots. Phenolic acids are very weak<br />
inhibitors of electron transport in both photosyntlresis <strong>and</strong> mitochondrial respiration<br />
(Morel<strong>and</strong> <strong>and</strong> Novitzky, 1987).<br />
Phenolic acids interact with horm one balances o f plants in complicated ways<br />
(Einhellig, 1995). For example, phenolic compounds can either increase or decrease<br />
natural auxin concentrations (Zenk <strong>and</strong> Muller, 1963; Tomaszewski <strong>and</strong> Thim ann,<br />
1966; Lee et al., 1982). Com m on phenolic acids antagonize the action o f both gib-<br />
bereUic acids (e.g., Jacobson <strong>and</strong> Corcoran, 1977) <strong>and</strong> abscisic acid (e.g., Ray <strong>and</strong><br />
Laloraya, 1984). Salicylic acid is a signal molecule that triggers many physiological<br />
events, especially response to pathogen infection (Crozier et al., 2000), but it is not<br />
considered a strong phytotoxin.<br />
All o f these findings are interesting, but careful studies by Blum et al. (1999) have<br />
shown that in natural soil systems, the concentration of phenolic acids available for
238 The <strong>Rice</strong> Plant<br />
1%... ;<br />
allelopatliic effects is strongly limited through binding to soil <strong>and</strong> m icrobial degradation.<br />
Considering the relatively high concentrations o f simple phenolic acids required<br />
to cause phytotoxicity <strong>and</strong> their low bioavailability in soil, claims o f the involvement<br />
o f such compounds in allelopathy must be viewed with skepticism (Blum et al., 1999).<br />
Derivatives of fatty acids <strong>and</strong> long-chain hydrocarbons <strong>and</strong> o f some sterols have<br />
been found in rice (M attice et al., 1998; Kim <strong>and</strong> Kim, 2000). Som e long-chain fatty<br />
acids are known phytotoxins. For example, nonanoic <strong>and</strong> decanoic acids were found<br />
to be phytotoxic in bioassays with algae (McCraleen et al., 1980). Pelargonio acid<br />
(nonanoic acid) is particularly phytotoxic <strong>and</strong> has been sold as a natural herbicide<br />
(Irzyk et al., 1997). The mechanism o f action o f these compounds is unlcnown; however,<br />
their properties would suggest that they may interfere with m embrane functions.<br />
Some steroids are known to be plant growth stimulators (Macias et al., 1999), but<br />
little is known o f their mechanism o f action. Steroids are thought to affect formation<br />
o f plant membranes <strong>and</strong> to play a role in cell división (Burden et al., 1989).<br />
Some tricyclic diterpenes (momilactones A, B, <strong>and</strong> C; oryzalexins A <strong>and</strong> C; <strong>and</strong><br />
ineketone) have been reported to be inhibitory to growth o f lettuce seedlings (Kato et<br />
al., 1973; Tsunakawa et al., 1976; Lee et al., 1999a <strong>and</strong> b ). Some o f these compounds<br />
are considered phytoalexins as well. M om ilactone B is quite active at submillimolar<br />
concentrations (Lee at al., 1999b), indicating that it could account for allelopathic<br />
effects o f certain rice cultivars. However, nothing is known o f the molecular site of<br />
action for these compounds as pathogen inhibitors or phytotoxins.<br />
SUMMARY AND OUTLOOK<br />
•• fr.<br />
i-<br />
The worldwide focus on allelopathy research in rice during the past decade (Olofs-<br />
dotter, 1998) is unprecedented in com parison with any other crop during the <strong>history</strong><br />
o f allelopathy research. Although rice cultivars with clear allelopathic activity have<br />
been identified, this trait has not been used as a selling point. A few studies have<br />
been conducted to isolate allelochemicals in rice. M ost o f the compounds isolated<br />
are com m on secondary metabolites (derivatives o f long-chain hydrocarbons, fatty<br />
adds, <strong>and</strong> aromatic acids, phenolic compounds, <strong>and</strong> sterols) that are ubiquitous in<br />
plants. A group o f tricyclic diterpenes loiown as momilactones <strong>and</strong> oryzalexins may<br />
be compounds that are unique to rice. Some o f the momilactones <strong>and</strong> oryzalexins<br />
have been reported to be highly phytotoxic. The momilactones <strong>and</strong> oryzalexins also<br />
have been reported as phytoalexins <strong>and</strong> to be induced by both biotic <strong>and</strong> abiotic<br />
stress factors. These compounds have also been reported in rice cultivars that are not<br />
known to be allelopathic. Therefore, it is doubtful that the momilactones <strong>and</strong>/or the<br />
oryzalexins are the true allelochemicals in rice. The search for allelochemicals in rice<br />
is evidently not over; discovery awaits.<br />
A bioassay-guided method o f isolation can facilitate the discovery of rice allelochemicals.<br />
This process can now be m ore conveniently carried out with availability<br />
of m odern instrum entation [e.g., use o f a GC/MS in studying allelochemicals from<br />
silvergrass {Vulpia spp.)] (An et al., 1996). After allelochemicals have been identified,<br />
it will be possible to use the inform ation to synthesize the com pound or to enhance<br />
its natural synthesis <strong>and</strong> have a cultivar with enhanced natural chemical defenses.<br />
Two approaches may eventually lead to the availability o f allelopathic rice cultivars<br />
that will consistently provide good yields <strong>and</strong> improved weed management. The
Studies on <strong>Rice</strong> ADelochemicols 239<br />
low-<strong>technology</strong> approach could do this simply by breeding for tliese traits. However,<br />
this approach has thus far been unsuccessful. The second approach is to genetically<br />
engineer highly allelopathic rice cultivars. The approaches to <strong>and</strong> pitfalls o f genetically<br />
engineering allelopathic crops are discussed in detail by Scheffler et al. (2001). Before<br />
allelopathy can be genetically engineered into rice, many questions wÜl have to be<br />
answered. For example, what are the most effective allelochemicals o f rice? W hat<br />
enzymes (thus, genes) are critical in their synthesis? How does the producing plant<br />
avoid autotoxicity?<br />
Considering the worldwide effort <strong>and</strong> the powerful, new scientific tools available,<br />
we expect that rice will be the first m ajor crop in which allelopathy, in conjunction<br />
with other methods,will be used to manage weeds. If so, this will be a model for<br />
utilization o f similar approaches to weed management in other crops.<br />
REFERENCES<br />
Agrow. 2000. Weeds Pose Most Threat to <strong>Rice</strong>. PJB Publications Ltd. No. 354, p. 23.<br />
Alsaadawi, I. S., S. M , Al-Harditliy, <strong>and</strong> B. A. Mahmoud. 1986. Effects o f tliree phe-<br />
■ nolic acids on chlorophyll content <strong>and</strong> ion uptake in cowpea seedlings. /. Chem.<br />
Ecol 12:221-227.<br />
An, M., J. E. Pradey, <strong>and</strong> T. Haig. 1996. Application o f GC/MS in allelopathy research:<br />
a case study. Rapid Comtnun. Mass Spectrom. 10:104-105.<br />
Bailee, N. E. 1985. Effects o f allelochemicals on mineral uptake <strong>and</strong> associated physiological<br />
process. Am. Chem. Soc. Symp. Ser. 268:161-178.<br />
Barkosky, R., <strong>and</strong> F. A. Einhellig. 1993. Effects o f salicylic acid on plant-w ater relationships.<br />
J. Chem. Ecol. 19:237-247.<br />
Blum, J., M. F. Austin, <strong>and</strong> S. R. Shafer. 1999. The fates <strong>and</strong> effects o f phenolic acids<br />
in a plant-m icrobial soil model system. In F, A. Macias, J. C. G. Galindo, J. M. G,<br />
M olinillo, <strong>and</strong> H. G. Cutler (eds.), Recent Advances in Allelopathy Vol. I, A Science<br />
for the Future. University of Cádiz Press, Cádiz, Spain, pp. 159-166.<br />
Burden, R. S., D. T, Cooke, <strong>and</strong> G. A. Carter. 1989. Inhibitors o f sterol biosynthesis<br />
<strong>and</strong> growth in plants <strong>and</strong> fungi. Phytochemistry 28:1791-1804.<br />
Callaway R. M ., <strong>and</strong> E. T. Aschehoug. 2000. Invasive plants versus their new <strong>and</strong> old<br />
neighbors: a mechanism for exotic invasion. Science 290:521-523.<br />
Cartwright, D. W., P. Langcake, R. J. Pryce, D. P. Leworthy <strong>and</strong> J. P. Ride. 1977.<br />
Chemical activation o f host defense mechanism as a basis for crop protection.<br />
Nature 267:511-513.<br />
Cartwright, D. W., P. Langcake, R. J. Pryce, D. P. I^wordiy, <strong>and</strong> J. P Ride. 1981.<br />
Isolation <strong>and</strong> characterization o f two phytoalexins from rice as momilactones<br />
A <strong>and</strong> B. Phytochemistry 20:535-537.<br />
Chou, C. H., <strong>and</strong> S. J. Chiou. 1979. Autointoxication mechanism o f Oryza sativa. II.<br />
Effects o f culture treatments on the chemical nature o f paddy soil <strong>and</strong> on rice<br />
productivity. /. Chem. Ecol. 5:35-859.<br />
Chou, C. H, <strong>and</strong> H. J. Lin. 1976. Autointoxication mechanism o f Oryza sativa. I.<br />
Phytotoxic effects o f decomposing rice residues in soÜ. J. Chem. Ecol 2:353-367.<br />
Crozier, A., Y. Kimiya, G. Bishop, <strong>and</strong> T. Yokota. 2000. Biosynthesis o f hormones<br />
<strong>and</strong> elicitor molecules. In B. B. Buchanan, W. Gruissem, <strong>and</strong> R. L Jones (eds.).
The <strong>Rice</strong> Pbnt<br />
Biochemistry <strong>and</strong> Molecular Biology of Plants. American Society o f Plant Physiologists,<br />
Rockville, MD, pp. 850-929.<br />
Devine, M. D., S. O. Duke, <strong>and</strong> C. Fedtke. 1993. Physiology of Herbicide Action. Prentice<br />
Hall, Englewood Cliffs, NJ, 441 pp.<br />
Dilday, R. H., P. Nastasi, <strong>and</strong> R. J. <strong>Smith</strong>, Jr. 1991. AUelopathic activity in rice {Qryza<br />
sativa L.) against ducksalad {Beteranthera Umosa) (Sw.) W illd.). In J. D. Hanson,<br />
M. J, Skalier, D. A. Ball, <strong>and</strong> C. V. Cole (eds.), Sustainable Agriculture for the Great<br />
Plains, Symposium Proceedings. Publ. ARS-89, U.S. Departm ent o f Agriculture,<br />
Washington, D C, pp. 193-201.<br />
Dilday, R. H., J. Lin, <strong>and</strong> W. Yan. 1994. Identification o f allelopathy in the USDA-ARS<br />
rice germplasm collection. Aust. J. Exp. Agric. 34:907-910.<br />
Dilday, R. H., W. Yan, <strong>and</strong> J. Lin. 1996. Identifying allelopathy in rice germplasm.<br />
In R. Naylor (ed.), Herbicides in Asian <strong>Rice</strong>: Transitions in Weed Management.<br />
Institute for International Studies, Stanford University, Palo Alto, CA <strong>and</strong> International<br />
<strong>Rice</strong> Research Institute, Manila, The Philippines, pp. 219-229.<br />
Dilday, R. H,, W. G. Yan, K. A. K. Moldenhauer, <strong>and</strong> K. A. Gravois. 1998. AUelopathic<br />
activity in rice 'for controlling m ajor aquatic weeds. In M. Olofsdotter (ed.),<br />
Allelopathy in <strong>Rice</strong>: Proceedings o f the Worhhop on Allelopathy in <strong>Rice</strong>, Nov. 25-27,<br />
1996. International <strong>Rice</strong> Research Institute, Manila, The Philippines, pp. 7-26.<br />
Duke, S. O., R. D. WiUiams, <strong>and</strong> A. H, M arkhart III. 1983, Interaction o f moisture<br />
stress <strong>and</strong> three phenolic compounds on lettuce seed germination. Ann. Bot,<br />
52:923-926.<br />
Duke, S, 0 -, A. M . Rim<strong>and</strong>o, R E. Dayan, C. Canel, D, E. Wedge, M . R. Tellez, K. K.<br />
Schrader, L. A. Weston, T J. Smillie, R. N. Paul, <strong>and</strong> M.V. Duke. 2000. Strategies<br />
for the discovery o f bioactive phytochemicals. In W. R. Bidlack, S. T. Omaye,<br />
M. S. Meskin, <strong>and</strong> D. K. W. Topham (eds.), Phytochemicals as Bioactive Agents.<br />
Technomic Publishing, Lancaster, PA, pp. 1-20.<br />
Einhellig, P. A. 1995. Mechanism o f action of allelochemicals in allelopathy. Am.<br />
Chem. Soc. Symp. Ser. 582:96-116.<br />
Einhellig, R A., <strong>and</strong> I. A. Rasmussen. 1978. Synergistic inhibitory effects o f vanillic <strong>and</strong><br />
p-hydroxybenzoic acids on radish <strong>and</strong> grain sorghum. /. Chem. Ecol. 4:425-436.<br />
Einhellig, R A., 1. Stille-Muth, <strong>and</strong> M . K. Schon, 1985. Effects o f aUelochemicals on<br />
plant-w ater relationships. Am. Chem. Soc. Symp. Ser. 268:179-195.<br />
EveraU, N. C., <strong>and</strong> D. R. Lees. 1996, The use of barley-straw to control general <strong>and</strong><br />
blue-green algal growth in a derbyshire reservoir. Water Res. 30:269-276.<br />
Fujii, Y. 1993. The aUelopathic effect o f some rice varieties. In Allelopathy in Control<br />
of Paddy Weeds. Tech. Bull. 134, ASPAC Food <strong>and</strong> Fertilizer Technology Center,<br />
Taiwan, pp. 1-6.<br />
Fujii, Y. 1995. The use o f aUelopathic chemicals in sustainable agriculture. Proceedings<br />
o f the Plant Growth Regulators Society, Am. 22nd. National Conference, M inneapolis,<br />
MN, luly 1 4 -1 8 ,1 9 9 5 .<br />
Ghosal, A., <strong>and</strong> R, P. Purkayastha. 1987. Biochem ical response o f rice (Oryza sativa<br />
L.) leaves to some abiotic elicitors o f phytoalexin. Indian J. Exp. Biol 25:395-399.<br />
Hassan, S. M ., I. R. Aidy, A. O. Bastawisi, <strong>and</strong> A. E. Draz. 1998. Weed management<br />
using aUelopathic rice varieties in Egypt. In M. Olofsdotter (ed.), Allelopathy<br />
in <strong>Rice</strong>: Proceedings of the Workshop on Allelopathy in <strong>Rice</strong>, Nov. 2 5 -2 7 , 1996.<br />
International <strong>Rice</strong> Research Institute, Manila, The Philippines, pp. 27-37.<br />
Irzyk, G. R , P. Zorner, <strong>and</strong> A. Kern. 1997 Sythe herbicide; a new contact herbicide<br />
based naturaUy occurring pelargonic acid. Weed Set. Soc. Am. Abstr. 37:103.
Studies on <strong>Rice</strong> Allelochemicals 241<br />
Ishii, T., <strong>and</strong> K. Kadoya. 1993. Phytotoxic constituents in the bark <strong>and</strong> sawdust extracts<br />
o f Chamccyparis obtusa <strong>and</strong> Cryptomeria japónica <strong>and</strong> their effects on the growth<br />
o f seedlings o f trifoliate orange {Pondrus trifoUata Raf.) <strong>and</strong> rice (Oryza sativa<br />
L,). /. ]pn. Soc. Hort. Sei. 62:285-294,<br />
Jacobson, A., <strong>and</strong>M . R. Corcoran. 1977. Tannins as gibberellin antagonists in the synthesis<br />
o f «-am ylase <strong>and</strong> acid phosphatase by barley seeds. Plant Physiol. 5 9 :1 2 9 -<br />
133.<br />
Kato, T., C. Kabuto, N. Sasaki, M . Tsunagawa, H. Aizawa, IC Fujita, Y. Kato, <strong>and</strong><br />
Y. Kitahara. 1973. M omilactones, growth inhibitors from rice, Oryza sativa L.<br />
Tetrahedron Lett. 39:3861-3864,<br />
Kato, X , M. Tsunakawa, N. Sasaki, H. Aizawa^ K. Fujita, Y. Kitahara, <strong>and</strong> N. Takahashi.<br />
1977a. Growth <strong>and</strong> germination inhibitors in rice husks. Phytochemistry 1 6 :4 5 -<br />
48.<br />
Kato, X , H. Aizawa, M. Tsunakawa, N. Sasaki, Y. Kitahara, <strong>and</strong> N. Talcahashi. 1977b.<br />
Chemical transformations o f the diterpene lactones m omilactones A <strong>and</strong> B.<br />
J. Chem. Soc. Perkin Trans. 1 3:250-254.<br />
Kato, H., O. Kodama, <strong>and</strong> X Akatsuka. 1993. Oryzalexin E, a diterpene phyto alexin<br />
from UV-irradiated rice hdives. Phytochemistry 33:79-81.<br />
Kato, H., O. Kodama, <strong>and</strong> X Akatsuka. 1994. Oryzalexin F, a diterpene phytoalexin<br />
from UV-irradiated rice leaves. Phytochemistry 33:229-301.<br />
Kawaguchi, S., K. Yoneyama, X Yokota, Y. Takeuchi, M. Ogasawara, <strong>and</strong> M . Konnai.<br />
1997. Effects o f aqueous extract o f rice plants {Oryza sativa L.) on seed germination<br />
<strong>and</strong> radicle elongation o f Monochoria vaginalis var. plantaginea. Plant<br />
Growth Regal 23:183-189,<br />
Kim, K. W., <strong>and</strong> K. U, Kim, 2000. Searching for rice allelochemicals. Proceedings of the<br />
International Workshop on <strong>Rice</strong> Allelopathy. Institute o f Agricultural Science <strong>and</strong><br />
Technology, Kyungpook National University, Tagen, Korea, pp. 73-84.<br />
Kim, K. U., <strong>and</strong> D. H. Shin. 1998. <strong>Rice</strong> allelopathy research in Korea. In M . Olofsdotter<br />
(ed,). Allelopathy in <strong>Rice</strong>: Proceedings of the Workshop on Allelopathy in <strong>Rice</strong>, Nov.<br />
2 5 -2 7 ,1 9 9 6 . International <strong>Rice</strong> Research Institute, Manila, The Philippines, pp.<br />
39-43.<br />
Kira, K. U., D. H. Shin, I. J. Lee, <strong>and</strong> H. Y. Kim. 2000. <strong>Rice</strong> allelopathy in Korea,<br />
Proceedings o f the International Workshop on <strong>Rice</strong> Allelopathy. Institute of Agricultural<br />
Science <strong>and</strong> Technology, Kyungpook National University, Tageu, Korea,<br />
pp. 4 8 -72.<br />
Kodama, O,, A. Yamada, A. Yamamoto, T. Takemoto, <strong>and</strong> X Akatsuka. 1988. In <br />
duction o f phytoalexins with heavy metal ions in rice leaves, Nippon Noyaku<br />
Gakkaishi 13:615-617,<br />
Kodama, O., W. X. Li, S. Tamogami, <strong>and</strong> X Akatsuka. 1992a. Oryzalexin S, a novel<br />
stemarane-type diterpene rice phytoalexin. Biosci. Biotechnol Biochem. 56:1 0 0 2 -<br />
1003.<br />
Kodama, O., J. Miyakawa, X Akatsuka, <strong>and</strong> S. Kiyosawa. 1992b. Sakuranetin, a fla-<br />
vanone phytoalexin from ultraviolet-irradiated rice leaves. Phytochemistry 31:<br />
3807-3809.<br />
Koga, J., M. Shimura, K. Oshim a, N. Ogawa, T. Yamauchi, <strong>and</strong> N. Ogasawara. 1995,<br />
Phytocassanes A, B, C, <strong>and</strong> D, novel diterpene phytoalexins from rice, Oryza<br />
sativa L. Tetrahedron 29:7907-7918.<br />
Koga, J., N. Ogawa, X Yamauchi, M. Kikuchi, N. Ogasawara, <strong>and</strong> M. Shimura. 1997.<br />
i ■’
The Rite Plant<br />
Functional m oiety for the antifungal activity o f phytocassanes E, a diterpene<br />
phytoalexin from rice. Phytochemistry 44:249-253.<br />
Koga, J., T. Yamauchi, M. Shimura, N. Ogawa> K. Oshima, K. Urnemura, M . Kikuchi,<br />
<strong>and</strong> N. Ogasawara. 1998. Cerebrosides A <strong>and</strong> C, sphingolipid elicitors o f hypersensitive<br />
cell death <strong>and</strong> phytoalexin accumulation in rice plants. J. Biol Chetn.<br />
273:31985-31991.<br />
Kono, Y., S. Takeuchi, O. Kodama, H. Sekido, <strong>and</strong> T. Akatsuka. 1985. Novel phytoalexins<br />
(oryzalexins A, B <strong>and</strong> C) isolated from rice blast leaves infected with Pyrkularia<br />
oryzae. II. Structural studies of oryzalexins. Agric, Biol Chem. 49:1695-<br />
1701.<br />
Lee, T. X , A. N. Starratt, <strong>and</strong> L J. Jernikar. 1982. Regulation of enzymatic oxidation<br />
of indole-3-acetic acid by phenolics: structure-activity relationships, Phytochemistry<br />
21:517-523.<br />
Lee, C. W., K. Yoneyama, Y. Takeuchi, M . Konnai, S. Tamogami, <strong>and</strong> O. Kodama.<br />
1999a. Momhactones A <strong>and</strong> B in rice straw harvested at different growth stages.<br />
Biosci. Biotechnol Bio.chem, 63:1318-1320.<br />
Lee, C. W., K. Yoneyama, M . Ogasawara, Y. Talceuchi, <strong>and</strong> M. Konnai. 1999b. Allelochemicals<br />
in rice straw. Proceedings 1(B); Weeds <strong>and</strong> Environmental Impact: 17th<br />
Asian-Pacific Weed Science Society Conference, Bangkok, Thail<strong>and</strong>, Nov. 22~T7.<br />
Lehman, M. E., <strong>and</strong>U. Blum. 1999. Evaluation of ferulic ad d uptake as a measurement<br />
o f allelochemical dose: effective concentration. /. Chem. Ecol 25:2585-2600.<br />
Lin, W. X., K. U. Kim, <strong>and</strong> D. H. Shin. 2000. <strong>Rice</strong> allelopathic potential <strong>and</strong> its modes<br />
o f action on barnyardgrass {Echinochloa crus-galli). Allelopathy!. 7:215-224.<br />
Lydon, J., <strong>and</strong> S. O. Duke. 1989. Xhe potential o f pesticides from plants. In L. E. Craker<br />
<strong>and</strong> J. E. Sim on (eds.), Herbs, Spices, <strong>and</strong> Medicinal Plants: Recent Advances in<br />
Botany, Horticulture, <strong>and</strong> Pharmacology Vol. 4. Oryx Press, Phoenix, AZ, pp.<br />
1-41.<br />
Lyu, S. W., U. Blum, T. M . Gerig, <strong>and</strong> T. E, O’Brien. 1990. Effects o f mixtures of<br />
phenolic acids on phosphorus uptake by cucumber seedlings. }. Chem. Ecol<br />
16:2559-2567.<br />
Macias, F. A., J. M. G. MoliniUo, J. C. G. Galindo, R. M . Varela, A. Torres, <strong>and</strong> A. M.<br />
Simonet. 1999. Terpenoids with potential use as natural herbicide templates. In<br />
H. G. Cutler <strong>and</strong> S. J. Cutler (eds.), Biologically Active Natural Products: Agrochemicals.<br />
CRC Press, Boca Raton, FL, pp, 15-31.<br />
Matsuo, M ., <strong>and</strong> H. Shibayama. 1996. The m onochoria test method, in a trial for<br />
studying allelopathic effects o f rice varieties to suppress or to control paddy weeds<br />
for the sustainable agriculture (in Japanese). Mar. Highl<strong>and</strong> 4:11-15. [Note: Journal<br />
title is English translation of Japanese title.]<br />
Matsuo, M ., <strong>and</strong> H. Shibayama. 1998. Observation on hypocotyl hair formation in<br />
juvenile seedlings o f Monochoria vaginalis, a test plant in the bioassay o f allelopathy<br />
in rice (in Japanese). Mar. Highl<strong>and</strong> 8:31-37, [Note: Journal title is English<br />
translation o f Japanese title.]<br />
Matsuyama, N. 1983, On the detection ofm om ilactones A <strong>and</strong> B in healthy <strong>and</strong> blast-<br />
infected rice leaves by GLC. Ann, Fhytopathol Soc. Jpn. 49:200-205.<br />
Matsuyama, N., <strong>and</strong> S. Wakimoto. 1985. Purification <strong>and</strong> characterization o f antiblast<br />
substance, S-1, formed mainly in blast-resistant lower rice leaves. Nippon<br />
Shokubutsu Byori Gakkaiho 51:498-500.<br />
Matsuyama, N., <strong>and</strong> S. Wakimoto. 1988. Isolation <strong>and</strong> identification o f diterpenoid
Studies on <strong>Rice</strong> Allelochemicals 243<br />
antiblast substances produced in the blast-infected rice leaves. Nippon Shokubutsu<br />
Byori Gakkaiho 54:183-188.<br />
Mattice, R., T. Lavy, B. Skulman, <strong>and</strong> R. Dilday. 1998. Searching for allelochemicals in<br />
rice that control ducksalad. In M . Olofsdotter (ed.), Allelopathy in <strong>Rice</strong>: Proceedings<br />
of the Workshop on Allelopathy in <strong>Rice</strong>, Nov. 25-27,1996. International <strong>Rice</strong><br />
Research Institute, Manila, The Philippines, pp. 81-98.<br />
McCraken, M . D., R. E. Middaugh, <strong>and</strong> R. S. Middaugh. 1980. A chemical characterization<br />
o f an algal inhibitor obtained from Chlamydomonas. Hydrobiologia<br />
70:271-276.<br />
Morel<strong>and</strong>, D. E., <strong>and</strong> W. P. Novitsky 1987. Effects o f phenolic acids, coumarins, <strong>and</strong><br />
flavonoids on isolated chloroplasts <strong>and</strong> mitochondria. Am. Chem. Soc. Symp. Ser.<br />
330:247-261.<br />
Nalcazato, Y., S. Tamogami, H. Kawai, M . Hasegawa, <strong>and</strong> O. Kodama. 2000. M ethionine-induced<br />
phytoalexin <strong>production</strong> in rice leaves. Biosci. Biotechnol. Biochem.<br />
64:577-583.<br />
Navarez, D., <strong>and</strong> M. Olofsdotter. 1996. Seeding technique for screening allelopathic<br />
rice {Oryza sativa L.). In Proceedings of the 2nd International Weed Control Conference,<br />
Copenhagen, pp. 1285-1290.<br />
Netzly, D. H., <strong>and</strong> L. G. Butler. 1986. Roots o f sorghum exude hydrophobic droplets<br />
containing biologically active components. Crop Sei. 26:775-778.<br />
Nimbal, C. I., J. E Pedersen, C. N. Yerkes, L, A. Weston, <strong>and</strong> S. C. Weller. 1996. Phytotoxicity<br />
<strong>and</strong> distribution of sorgoleone in grain sorghum germplasm. /. Agrie.<br />
Pood Chem. 44:1343-1347.<br />
Olofsdotter, M . (Ed.) 1998. Allelopathy in <strong>Rice</strong>. International <strong>Rice</strong> Research Institute,<br />
M anila, Pilippines, p. 154.<br />
Olofsdotter, M ., D. Navarez, <strong>and</strong> M. Rebulanan. 1997. <strong>Rice</strong> allelopathy: where are we<br />
<strong>and</strong> how far can we get? In Proceedings of the 1997 Brighton Crop Conference,<br />
British Crop Protection Council, Brighton, Engl<strong>and</strong>, pp. 99-104.<br />
Olofsdotter, M ., D. Wang, <strong>and</strong> D. Navarez. 1999. Allelopathic rice for weed control. In<br />
F. A. Macias, f. C. G. Galindo, J, M. G. Molinillo, <strong>and</strong> H. G. Cutler (eds.), Recent<br />
Advances in Allelopathy, Vol. I, A Science for the Future. Servicio de Publicaciones,<br />
Universidad de Cádiz, Cádiz, Spain, pp. 383-390.<br />
Olofsdotter, M.> L. Bach Jensen, D. Navarez, R. Pamplona, <strong>and</strong> A. Rim<strong>and</strong>o. 2000.<br />
Progress in rice allelopathy research. Book of Abstracts of the 3rd International<br />
Weed Science Congress, Foz do Iguassu, Brazil, June 6 -1 1 . International Weed<br />
Science Society, Oregon State University, Corvallis, O R (Abstr. 72).<br />
Quayyum, H., A. U. MaUik, <strong>and</strong> P. F. Lee. 1999. Allelopathic potential o f aquatic<br />
plants associated with wild rice (Zizinia palustris). I. Bioassay with plant <strong>and</strong> lake<br />
sediment samples, /. Chem. Ecol 25:209-220.<br />
Ray, S. D., <strong>and</strong> M. M. Laloraya. 1984. Interaction o f gibberellic acid, abscisic acid, <strong>and</strong><br />
phenolic compounds in the control o f hypocotyl growth o f Amaranthus caudatus<br />
seedlings. Can. J. Bot. 62:2047-2052.<br />
<strong>Rice</strong>, E. L. 1984. Allelopathy, 2nd ed. Academic Press, Orl<strong>and</strong>o, FL, 422 pp.<br />
<strong>Rice</strong>, E. L., C. Y. Lin, <strong>and</strong> C. Y. Huang. 1980. Effects o f decaying rice straw on growth<br />
<strong>and</strong> nitrogen fixation o f a blue green alga. Bot. Bull. Acad. Sin. 21:111-117.<br />
Rim<strong>and</strong>o, A. M., F. E. Dayan, M . A. Czarnota, L. A. Weston, <strong>and</strong> S. O. Duke. 1998. A<br />
new photosytem II electron transfer inhibitor from Sorghum bicolor (L.). /. Nat.<br />
Prod. 61:927-930.
244 The Ri(e Plant<br />
.'iUl<br />
iiiii<br />
Rim<strong>and</strong>o, A. M., M. Olofsdotter, F. E. Dayan, <strong>and</strong> S. O. Duke, 2001. Searching for<br />
allelochemicals in rice: an example o f bioassay-guided isolation. Agron, J. 93:1 6 -<br />
20.<br />
Robbers, J, E., M. K. Speedie, <strong>and</strong> V. E. Tyler. 1996. Pharmacognosy <strong>and</strong> Pharmacobio<strong>technology</strong>.<br />
Williams & Wilkins, Baltimore, 337 pp.<br />
Robinson, T. 1991. The Organic Constituents of Higher Plants. Their Chemistry <strong>and</strong><br />
Interrelationships, 6th ed. Cordus Press, North Amherst, MA, 346 pp.<br />
Scheffler, B. E., S. O. Duke, F. E. Dayan, <strong>and</strong> E. Ota. 2001. Crop allelopathy: enhancem<br />
ent through bio<strong>technology</strong>. Recent Adv. Phytochem. Vol. 35 (Regulation<br />
o f phytochemicals by molecular techniques) ISl-TJA..<br />
Sekido, H., T. Endo, R. Suga, O. Kodama, T. Akatsuka, Y. Kono, <strong>and</strong> S. Takeuchi. 1986.<br />
Oryzalexin D [3,7-dihydroxy-(+)-s<strong>and</strong>aracopimaradiene], a new phytoalexin<br />
isolated from blast-infected rice leaves. Nippon Noyaku Gakkaishi 11:369-372.<br />
Shunura, M ., M. Iwata, N. Tashiro, Y. Sekizawa, Y. Suzuki, S. Mase, <strong>and</strong> T. Watanabe.<br />
1981. Anti-conidial germination factors induced in the presence o f probenazole<br />
in infected host leaves. I. Isolation <strong>and</strong> properties o f four active substances. Agric.<br />
; Biol. Chem. ,45:1431-1435.<br />
Streibig, J. C., F. E. Dayan, A. M. Rim<strong>and</strong>o, <strong>and</strong> S. O. Duke. 1999. Joint action of<br />
natural <strong>and</strong> synthetic photosystem II inhibitors. Pestic. Sci. 55:137-146.<br />
Tamogami, S., O. Kodama, K. Hirose, <strong>and</strong> T. Akatsuka. 1995, Pretilachlor [2-chloro-<br />
N -(2,6-diethylphenyl-N -(2 -propoxyehtyl)acetamide] - <strong>and</strong> butachlor [N- (but-<br />
oxym ethyl)-2-chloro-N'“(2,6-diethylphenyl)acetamide] -induced accumulation<br />
of phytoalexin in rice {Oryza sativa) plants. J. Agric. Food Chem. 43:1695-1697.<br />
Tanaka, K, S. Ono, <strong>and</strong> T, Hayasaka. 1990. Identification <strong>and</strong> evaluation o f toxicity of<br />
rice root elongation inhibitors in flooded soils with added wheat straw. Soil Sci,<br />
PlantNutr. 36:97-103.<br />
Tomaszewski, M ., <strong>and</strong> K. V. Thim ann. 1966, Interactions o f phenolic acids, metallic<br />
ions, <strong>and</strong> chelating agents on auxin-induced growth. Plant Physiol. 41:1443-<br />
1454.<br />
Tsunakawa, M,, A. Ohba, N. Sasaki, C. Kabuto, T, Kato, Y. Kitahara, <strong>and</strong> N. Takahashi.<br />
1976. M omilactone C, a m inor constituent of growth inhibitors in rice husk.<br />
Chem. Lett 11:1157-1158.<br />
Van Sumere, C. F., J. Cottenie, J. DeGreef, <strong>and</strong> J. Kint, 1971. Biochem ical studies<br />
in relation to the possible germination regulatory role o f naturally occurring<br />
coumarin <strong>and</strong> phenolics. Recent Adv. Phytochem. 4:165-221.<br />
Waller, G. R., M. Jurzysta, <strong>and</strong> R. L. Z. Thorne. 1993. Allelopathic activity o f root<br />
saponins from alfalfa (Medigaco sativa L.) on weeds <strong>and</strong> wheat. Bot Bull. Acad.<br />
Sm. 34:1-11.<br />
Yang, Y. S,, <strong>and</strong> Y. Futsuhara. 1991. Inhibitory effects o f volatile compounds released<br />
from rice callus on soybean growth: allelopathic evidence observed using in vitro<br />
cultures. Plant Sci. 77:103-110.<br />
Zenk, M. H., <strong>and</strong> G. Muller. 1963. In vivo destruction of exogenously applied indolyl-<br />
3-acetic acid as influenced by naturally occurring phenolic acids. Nature 200:<br />
761-763.
SECTION<br />
III<br />
Production
il<br />
■I<br />
| i;><br />
^jS;:
Chapter<br />
3.1<br />
Global Ríce Production<br />
Bobby Coats<br />
Cooperative Erttensior Service<br />
Agricultural Economics Section<br />
University of Arkansas<br />
Little Rock, Arkansas<br />
INTRODUCTION<br />
REGIONAL RICE PRODUQIO N<br />
RICE PRODUCTION BY COUNTRY<br />
RICE AREA HARVESTED<br />
RICE MILLED YIELD AND MILLING RATE<br />
INTRODUCTION<br />
<strong>Rice</strong>, one o f the world’s m ost im portant food grains, is produced in at least 95 countries.<br />
Globally, no food grain is more im portant than rice from a nutritional perspective,<br />
a food security perspective, or an econom ic perspective. Few food commodities<br />
will contribute as much as rice to tlie development <strong>and</strong> sustainability of the emerging<br />
global economy.<br />
In 2000, the U.S. Departm ent o f Agriculture (USDA) estimated that Chinese rice<br />
farmers produced 33.2% o f the worldwide rice <strong>production</strong>, followed by India with<br />
21.6% , Indonesia 8.4% , Bangladesh 6.1% , <strong>and</strong> Vietnam 5.3% . China <strong>and</strong> India are<br />
two countries that have fuUy exploited rice’s nutritional, food security, <strong>and</strong> econom ic<br />
importance in the development o f their economies. As other less developed countries<br />
follow their econom ic development example, developed countries such as the United<br />
States, European Union, <strong>and</strong> Australia will find it increasingly difficult to compete in<br />
the export market.<br />
In 1961, global rice <strong>production</strong> was estimated at 147.3 million milled m etric tons<br />
produced on 115.8 million hectares with an average yield o f 1.272 mt/ha (Table 3.1.1).<br />
<strong>Rice</strong>; Origin, History, Tedinology, <strong>and</strong> Production, edited by C. Wayne <strong>Smith</strong><br />
ISBN 0-471-34516-4 © <strong>2003</strong> John Wiley & Sons, Inc.<br />
247
248 Production<br />
TABLE 3.1.1.<br />
Global <strong>Rice</strong> Area Harvested, M illed Yield, Wlilled Production, M ilied as a Percent<br />
of Rough, <strong>and</strong> Exports as a Percent of M illed, ]961~2000<br />
iiyiiii:'’- ' I<br />
1<br />
i<br />
Year<br />
1961<br />
1962<br />
1963<br />
1964<br />
1965<br />
1966<br />
1967<br />
1968<br />
1969<br />
1970<br />
1971<br />
1972<br />
1973<br />
1974<br />
1975<br />
1976<br />
1977<br />
1978<br />
1979<br />
1980<br />
1981<br />
1982<br />
1983<br />
1984<br />
1985<br />
1986<br />
1987<br />
1988<br />
1989<br />
1990<br />
1991<br />
1992<br />
1993<br />
1994<br />
1995<br />
1996<br />
1997<br />
1998<br />
1999<br />
2000<br />
Area<br />
Harvested<br />
(ha)<br />
115 817 000<br />
119719000<br />
121151000<br />
125 403 000<br />
123 967 000<br />
125 679 000<br />
126 990 000<br />
128 593 000<br />
131416 000<br />
132 654 000<br />
134 825 000<br />
132 665 000 .<br />
136 288 000<br />
137 796 000<br />
142 890 000<br />
141429 000<br />
143 412 000<br />
143 645 000<br />
141230000<br />
144414 000<br />
144376 000<br />
140 523 000<br />
144 617 000<br />
144 145 000<br />
144 823 000<br />
144 810 500<br />
141574000<br />
146 052 000<br />
146 621000<br />
146 741 000<br />
147 456 000<br />
146 409 000<br />
144 899 000<br />
147 432 000<br />
148 080 000<br />
149 747 000<br />
151290 000<br />
152 394000<br />
154 965 000<br />
152 058 000<br />
Milled Yield<br />
(mt/ha)<br />
1.272<br />
1.296<br />
1.395<br />
1.441<br />
1.395<br />
1.424<br />
1.487<br />
1.515<br />
1.530<br />
1.606<br />
1.600<br />
1.575<br />
1.670<br />
1.638<br />
1.702<br />
1.667<br />
1,747<br />
1.826<br />
1.818<br />
1.869<br />
1.925<br />
2,028<br />
2.122<br />
2.197<br />
2.196<br />
2.182<br />
2,222<br />
2.269<br />
2.346<br />
2.399<br />
2.405<br />
2.430<br />
2.453<br />
2.473<br />
2.508<br />
2.539<br />
2.557<br />
2.586<br />
2.634<br />
2.608<br />
Milled<br />
Production<br />
147 300 000<br />
155105 000<br />
169 013000<br />
180 738 000<br />
172 901000<br />
178 996 000<br />
188 853 000<br />
194 855 000<br />
201 082 000<br />
213 002 000<br />
215 770000<br />
208 935 000<br />
227 555 000<br />
225 662 000<br />
243 144 000<br />
235 807000<br />
250 572000<br />
262 355 000<br />
256 824000<br />
269 956 000<br />
277 885 000<br />
285 019 000<br />
306 924000<br />
316 737 000<br />
317 964000<br />
316 026 000<br />
314 597 000<br />
331424000<br />
343 902 000<br />
352 036000<br />
354670 000<br />
355 714 000<br />
355 396 000<br />
364 534 000<br />
371442000<br />
380 199 000<br />
386 805 000<br />
394 037 000<br />
408 207 000<br />
396 575 000<br />
Milled<br />
(% ) of<br />
Rough<br />
68.31<br />
68.00<br />
68.06<br />
68.08<br />
68.20<br />
68.30<br />
68.21<br />
68.18<br />
68.11<br />
68.16<br />
68.15<br />
68.23<br />
68.17<br />
68.16<br />
68.03<br />
68.00<br />
67.95<br />
68.07<br />
68.20<br />
68.00<br />
68.06<br />
68.14<br />
68.07<br />
68.13<br />
68.05<br />
68.03<br />
67.80<br />
67.68<br />
67.69<br />
67,63<br />
67.53<br />
67.50<br />
67.45<br />
67.48<br />
67.37<br />
67.48<br />
67.36<br />
67.29<br />
67.24<br />
67.20<br />
Exports,<br />
Jan."Dec.<br />
(% of milled]<br />
4.31<br />
4,73<br />
4.57<br />
4.56<br />
4.56<br />
4.35<br />
3.79<br />
3.85<br />
4.08<br />
4.02<br />
4.04<br />
4.01<br />
3,37<br />
■ 3.24<br />
3.45<br />
4.50<br />
3.83<br />
4.52<br />
- 4.88<br />
4.69<br />
4.13<br />
4.04<br />
3.95<br />
3.63<br />
3.90<br />
4.22<br />
3.77<br />
4.43<br />
3.58<br />
3.67<br />
4.23<br />
4.44<br />
4.91<br />
5,90<br />
5.58<br />
5.23<br />
7.43<br />
6.58<br />
5.82<br />
5.85<br />
Source: U S. Department of Agria,Uu,c Economic Research Sem ce ProducUon, Supply, <strong>and</strong> Dislribution<br />
(PS&D) Database, June 2000.
Global <strong>Rice</strong> Production 249<br />
By 1983, global rice <strong>production</strong> had more tlran doubled, to 307 million tons on 144.6<br />
million hectares with <strong>and</strong> average yield 2.122 mt/ha. In 2000, global rice <strong>production</strong><br />
was estimated at 396.6 m illion m etric tons produced on 152.1 m illion hectares with<br />
an average yield o f 2.608 mt/ha.<br />
Prom 1961 to 2000, global <strong>production</strong> increased by 169% , for an average annual<br />
increase o f 4.33% for tlie time period. This was a function o f hectarage expansion<br />
<strong>and</strong> a significant improvement in yields. Hectarage during the period 1961-2000<br />
increased 36 241000 ha, or 31.3% . The average annual increase from 1961 to 2000 was<br />
0.8% . Piirther increases in total global rice hectarage will be limited due to significant<br />
gains in productivity. Relocation o f exported rice probably wiU be quite significant<br />
as less developed countries that have a <strong>production</strong> <strong>and</strong> econom ic advantage build<br />
export market share. During the 1961-2000 period, yield increased 105% , an average<br />
annual increase o f 2.69% . For crop years 1995-2000, Australia averaged just under 6<br />
mt/ha compared to a 2000 global average o f2.6080. Due to the dynamics o f the global<br />
economy, the next doubling o f rice yields could take less than 20 years.<br />
The new global econom y will, with each passing year, increase com petition. The<br />
increased com petition among rice-producing countries will force m ajor gains in productivity.<br />
In the new global economy, rice <strong>production</strong> will be defined by need, food<br />
security, <strong>and</strong> the global export market. Global exports in 1961 were 4.31% o f milled<br />
<strong>production</strong> <strong>and</strong> 5.85% in 2000. In 1997 global exports were at an all time high o f<br />
7,43% o f milled <strong>production</strong>. If market barriers continue to fall, coupled with changes<br />
in consumer tastes <strong>and</strong> preferences, 20% o f the rice produced globally may well move<br />
to the consumer in tlie export marketplace.<br />
Even though need <strong>and</strong> food security will continue to be a significant issue for<br />
all rice-producing countries, the export market will increasingly influence the price<br />
that global consumers pay for rice. Ultimately, in a global marketplace, the rice export<br />
market belongs to the low-cost-producing countries.<br />
The implications are that com petition created by globalization will change how<br />
rice is produced <strong>and</strong> who produces rice. If countries continue to embrace the new<br />
global economy, change within the rice industry will occur very rapidly. Production<br />
gains <strong>and</strong> improved grain quality wiU exceed expectations because of technological<br />
advancements, improved agronomic <strong>production</strong> practices, <strong>and</strong> l<strong>and</strong> <strong>and</strong> water<br />
resource development activities. Thus those countries with a <strong>production</strong>, processing,<br />
<strong>and</strong>/or marketing advantage will exp<strong>and</strong> <strong>production</strong> tlirough acreage expansion<br />
<strong>and</strong>/or m ajor gains in productivity.<br />
REGIONAL RICE PRODUCTION<br />
Globally, the world is composed o f a large number o f geographic, trade, <strong>and</strong>/or<br />
business regions. Regional rice statistics are shown in Table 3,1.2. The table lists 45<br />
rice <strong>production</strong> <strong>and</strong>/or econom ic regions. Each region is defined in the footnotes o f<br />
Table 3.1.2.<br />
<strong>Rice</strong> producers in foreign countries (the world except for the United States)<br />
produced 145.5 million m etric tons o f milled <strong>production</strong> in 1961 <strong>and</strong> 390.5 million<br />
m etric tons in 2000. The milled yield per hectare was 1.26 m etric tons in 1961 <strong>and</strong><br />
2.59 m etric tons per hectare in 2000. Milled <strong>production</strong> in less developed countries<br />
(foreign ^ developed — Asian NICs — NIS — eastern Europe) was 133.1 in 1961 <strong>and</strong>
TABLE 3.1.2. Select <strong>Rice</strong> Regional Production, Processing, <strong>and</strong> Export Statistics, June 2000<br />
A rea Harvested M ille d Yield d Production<br />
M ille d<br />
Exports,<br />
% Change<br />
% C hange<br />
% o f '% C h ange<br />
( % o f<br />
J a n .-D e c<br />
Regions'"<br />
hectares from 1961 metric tons from 1961 metric tons W orld from 1961<br />
R ough)<br />
[ % o f M ille d )<br />
Foreign countries 150828000 30.96 2.589 104.87 . 390471000 98.46 168.30% 67.15 5.26<br />
Less developed 148476000 33.07 2.552 113.91 378983 000 95.56 184.65 67.03 4.74<br />
Asia <strong>and</strong> Near East 137040000 27.85 2.643 108.60 362 192 000 91.33 166.61 67.31 4.59<br />
Asia <strong>and</strong> Oceania 136454000 27.76 2.651 109.23 361 692000 91.20 167.21 67.33 4.77<br />
Asia 136268000 27.61 2.645 108.76 360433 000 90.89 166.47 67.31 4.60<br />
PECO 69528000 28.49 3.417 124.95 237592000 59.91 188.96 68.22 6.97<br />
APEC 61149000 24.71 3.499 ' 126.77 213979000 53.96 182.76 68.50 5.84<br />
Reorienting economies 40 358 000 18.67 3.874 188.46 156356000 39.43 242.21 69.23 3.73<br />
Greater Cliina 30000000 14.11 4.385 206.86 131537 000 33.17 250.13 70.00 1.37<br />
South Asia 60 095 000 29.91 1.977 88.11 118 835000 29.97 144.37 66.68 2.57<br />
Southeast Asia 42421000 48.85 2.203 100.64 93442000 23.56 198.62 63.83 11.84<br />
CER <strong>and</strong> AFTA 34160000 59.15 2.387 101.43 81 541000 20.56 220.61 64.80 13.95<br />
ASEAN 33 974000 58.43 2.363 99.92 80 282 000 20.24 216.86 64.70 13.33<br />
Western hemisphere total 6 895 000 29.02 2.900 111.99 19 998 000 5.04 173.50 67,65 20.10<br />
OECD 3 749 000 ^15.68 4.826 47.76 18 092 000 4.56 24.59 71.00 29.03<br />
Developed countries 3 582 000 -15-54 4.911 47.08 17592 000 4.44 24.25 71.15 29.89<br />
Northeast Asia 3 752 000 -34.54 4.429 42.82 16 619 000 4.19 -6.50 72.49 4.03<br />
Latin America total 5 665 000 20.51 2.453 107.88 13 894000 3.50 150.39 66.47 • 9.85<br />
South America 5113 000 25.01 2.472 106.17 12 637 000 3.19 157.79 66.62 10.72<br />
Africa 7326000 160.25 1.512 50.90 11079 000 2.79 292.87 63.15 4.60<br />
MERCOSUR 3 704000 8.05 2.309 100.43 8 551000 2.16 116.59 68.00 10.82<br />
Northern hemisphere Americas 1 7S2 000 42.11 4.131 1,14.93 7 361000 1.86 205.44 69.50 36.19<br />
Subsaharan Africa 6 667000 158.21 1.071 35.57 7138 000 1.80 250.07 62.17 0.00<br />
ArianNICS 1412 000 -26.69 4.698 68.87 6633 000 1.67 23.80 72.85 1.81<br />
NAFTA 1317 000 66.92 4.840 92.37 , 6 374000 1.61 221.11 70.33 4 1 .6 4<br />
North America 1317000 66.92 4.840 92.37 6 374000 1.61 221.11 70.33 41,64<br />
Middle East <strong>and</strong> North Africa 1274000 97.83 4.280 101.60 5453 000 1.38 298.90 65.37 Q7?<br />
Other South America 1 649 000 140.03 2.972 103,14 4901000 1.24 387.66 64.77 23.06<br />
West Africa 4205000 162.98 1.066 59.34 4483000 1.13 318.97 61.15 0.00<br />
North Africa 659000 182.83 5.980 78.40 3941 000 0.99 404.61 65.00 12.69<br />
Europe 611000 37.00 3.350 22.17 2 047000 0.52 67.38 65.13 67.56<br />
Southern Africa 1447000 75.61 1.305 26.70 1889000 0.48 122.50 64.19 0.00<br />
EU 15 396000 42.96 4.023 11.56 1 593 000 0.40 59.46 65.23 86.19<br />
Middle East 615 000 49.64 2.459 72.44 1 512 000 0.3S 158.02 66.34 1.98<br />
CER 186000 830.00 6.769 41.02 1 259 000 0.32 1211.46 71.49 53,61<br />
Oceania 186 000 830.00 6.769 41.02 1259 000 0.32 1211.46 71.49 53.61<br />
Transitioning Economies 372 000 120.12 1.884 42.19 701 000 0.18 212.95 64.79 2.85<br />
NIS/USSR 349000 195.76 1.908 56.39 666000 0.17 362.50 64.91 3.00<br />
Central America 245000 21.89 2.131 159.56 522 000 0.13 216.36 65.01 1.92<br />
East Africa 475 000 433.71 1.034 24.43 491000 0.12 563,51 65.55 0.00<br />
Caribbean 220 000 -16.67% 2.114 114.62 465 000 0,12 78.85 64.14 0.00<br />
Central Africa 540 000 671.43 0.509 -22.53 275 000 0.07 497.83 60.04 0.00<br />
Central Asian Republics 157000 0.00 1.573 0.00 247000 0.06 0.00 64,83 4.05<br />
Other European NIS Republics 22000 0.00 2.682 0.00 59000 0.01 0.00 64.84 0.00<br />
Eastern Europe 23000 -54.90 1.522 -3.00 35 000 0.01 -56.25 62.50 0.00<br />
World 152 058 000 31.29 2.608 105.03 396 575 000 100.00 169.23 67.20 5.85<br />
S ou rce: U.S. Department of Agriculture Economic Research Service Production, Supply, <strong>and</strong> Distribution (PSSD) Database, June 2000.<br />
‘^W orld: foreign + U.S.<br />
F o reisn cou n tries: world — U.S.; includes, but wili n o t add from: western hemisphere (-U.S.) + Etuope + Africa + Asia <strong>and</strong> Near East + Oceania.<br />
D ev elo p ed co u n tries: Canada + U.S. + EU + other western Europe + Israel + South Africa +' Japan + Australia -(- New Zeal<strong>and</strong>.<br />
L ess d ev elop ed cou n tries: forei^ — developed — Asian NICs — NTS — eastern Europe.<br />
Westerw h em isp h ere: Americas + South America.<br />
L a tin am e ric a : Mexico + Central America + Caribbean + South America.<br />
N orthern h em isp h ere A m erica s: North America + Caribbean + Central America.<br />
c o n tin u e d
o<br />
cn<br />
TABLE 3J .2.<br />
Select <strong>Rice</strong> Regionol Production, Processing, <strong>and</strong> Export Stotistics, June 2000 (Continued)<br />
N orth A m erica : Canada, Mexico, United States, Greenl<strong>and</strong> (geograpiiically North Anaerica, despite politically Terr, of Denmark; data separate from Denmark).<br />
C a ribb ea n : Bermuda, Bahamas, Barbados, Cuba, Dominica, Dominican Republic, French West Indies, Grenada, Guadelope, Haiti, Jamacia <strong>and</strong> dependencies, Martinique, Nctherl<strong>and</strong><br />
Antilles, Puerto Rico, St. Lucia, St. Kitts <strong>and</strong> Nevis, St. Vincent <strong>and</strong> Grenadines, Trinidad <strong>and</strong> Tobago, U.S. Virgin Isl<strong>and</strong>s.<br />
C en tral A m erica: Belize, Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua, Panama.<br />
S ou th A m erica to tal: Argentina + Brazil + other South America, Argentina, Brazil.<br />
O d ier S ou th A m erica : S. America — Brazil — Argentina, Bolivia, Chile, Colombia, Ecuador, Falkl<strong>and</strong> Isl<strong>and</strong>s, French Guiana, Guyana, Paraguay, Peru, Suriname, Uruguay, Venezuela.<br />
Europe: EU + other western Europe + eastern Europe — Baltics + other European NIS + Russia* + former USSR* (prior to 1986) (excludes Caucasus republics + Central Asian<br />
republics ofNIS from 1987).<br />
E U -15 (European Union): Austria, Belgium <strong>and</strong> Luxembourg, Denmark, Finl<strong>and</strong>, France, Germany, United (begins 199‘1), former FRG (ends 1990), former GDR (ends 1990), Greece,<br />
Irel<strong>and</strong>, Italy, Netherl<strong>and</strong>s, Portugal, Spain, Sweden, United Kingdom.<br />
O th er W estern E u rop e: Faroe Isl<strong>and</strong>s, Gibraltar, Icel<strong>and</strong>, Malta <strong>and</strong> Gozo, Norway, Switzerl<strong>and</strong>.<br />
E astern E u rop e: Albania, Bulgaria, former Czechoslovakia (ends 1991), Czech Republic (begins 1992), Slovakia (begins 1992), Hungary, Pol<strong>and</strong>, Romania, former Yugoslavia, Bosnia-<br />
Hercegovina (new country; no data yet), Croatia (new country; no data yet), Macedonia (new country; no data yet), Slovenia (new country; no data yet), Yugoslavia (Serbia +<br />
Montenegro; new country; no data yet).<br />
N IS (New Independent States): 15 FSU republics begmning 1987; former USSR ends 1986, Russia.<br />
B a ltics: Estonia, Latvia, Lithuania.<br />
O th er E u rop ean N IS rep u blics: Belarus, Moldova, Ukraine.<br />
C au casus rep u b lics (excluded from Europe): Armenia, Azerbaijan, Georgia.<br />
C en tral A sian rep u b lics (excluded from Europe): Kazakstan, Kyrgystan, Tajikistan, Turkmenistan, Uzbekistan.<br />
A frica toted: South Africa + sub-Saharan Africa + North Africa, South Africa.<br />
S u b sa k a ra n A frica : West, Central, <strong>and</strong> East Africa, + southern Africa (excludes South Africa).<br />
W est A frica : Benin, Burkina, Cameroon, Cape Verde Isl<strong>and</strong>s, Chad, Cote D’Ivoire, Gambia, Ghana, Guinea, Ginnea-Bissau, Liberia, Mali, Mauritania, Niger, Nigeria, Senegal, Sierra<br />
Leone, Togo.<br />
C en tral A frica : Central African Republic, Congo (Brazzaville), Equatorial Guinea, Gabon, Sao Tome <strong>and</strong> Priadpe, Zaire.<br />
E ast A frica : Burundi, Djibouti <strong>and</strong> Afers-Issas, Eritrea, Ethiopia, Kenya, Rw<strong>and</strong>a, Somalia, Sudan, Tanzania, Ug<strong>and</strong>a.<br />
S ou thern A frica : Angola, Botswana, Comoros Isl<strong>and</strong>s, Lesotho, Madagascar, Malawi, Mauritius, Mozambique, Reunion, Seychelles, Swazil<strong>and</strong>, Zambia, Zimbabwe.<br />
N orth A frica : Algeria, Libya, Egypt, Morocco, Tunisia.<br />
M idd le E ast a n d N orth A frica : Middle East <strong>and</strong> North A frica .<br />
M idd le E ast. Bahrain, Cyprus, Gaza Strip (new country; no data yet), Iran, Iraq, Israel, Jordan, Kuwait, Lebanon, Oman, Qatar, Saudi Arabia, Syria, Turkey, United Arab Emirates,<br />
West Bank (new country, no data yet) Yemen, United (begins 1991), Former Yemen, South (Aden) (ends 1990), former Yemen, North (Sanaa) (ends 1990).<br />
A sia an d N ea r E a s t Asia + Middle East + Caucasus republics + Central Asian republics.<br />
A sia a n d O cea n ia: Asia + Oceania.<br />
A sia : Greater China Northeast Asia -)- Southeast Asia -|- South Asia.<br />
G reater C h in a : China, Hong Kong, Macau.<br />
N o rthea st A sia: Japan, North Korea, South Korea, Mongolia, Taiwan.<br />
S ou theast A sia: Brunei, Burma/Myanmar, Cambodia/Kampuchea/Khmer Republic, Indonesia, Laos, Malaysia, P h ilip p in es , S in g a p o re, T h a ila n d , V ietn a m .<br />
S ou th A sia : Afghanistan, Bangladesh, Bhutan, India, Maidive Isl<strong>and</strong>s, Nepal, Pakistan, Sri Lanka.<br />
O cea n ia : Australia -I- New Zeal<strong>and</strong> + other Oceania (AustraHa, New Zeal<strong>and</strong>).<br />
O th er O cea n ia: Fiji, French Polynesia, Kiribati <strong>and</strong> Tuvalu/Gilbert <strong>and</strong> Ellice Isl<strong>and</strong>s, New Caledonia, Papua New Guinea, Solomon Isl<strong>and</strong>s, Tonga, Vanuatu/New Hebrides, western<br />
Samoa.<br />
A sian N IC s (newly industriahzed countries): Hong Kong + South Korea + Singapore -!- Taiwan.<br />
T ran sition in g eco n o m ies: NIS (15 FSU republics + former USSR) Eastern Europe.<br />
R eorien tin g eco n o m ies: transitioning economies + China + Mongolia + Cambodia + Laos + Vietnam (excludes North Korea <strong>and</strong> Cuba, so not precisely= former Centrally Planned).<br />
N A FTA : Canada -r Mexico + United States.<br />
M ER C O SU R : Argentina + Brazil + Paraguay + Uruguay.<br />
O EC D : Australia + New Zeal<strong>and</strong> + Japan + NAFTA + Icel<strong>and</strong> + Norway -I- Switzerl<strong>and</strong> + Turkey -t- EU.<br />
P E C C (Pacific Economic Cooperation Conference): NAFTA + Chile + Colombia + Peru + Brunei + China + Hong Kong + Indonesia -h Japan + South Korea 4- Malaysia +<br />
Phflippmes + Singapore + Taiwan + Thail<strong>and</strong> + Vietnam + Russia + Australia + New Zeal<strong>and</strong> + Papua New Guinea.<br />
A P E C (Asia-Pacific Economic Cooperation Forum): NAFTA + Chile - 1- Brunei -I- China -I- Hong Kong + Japan -f Indonesia + South Korea + Malaysia + PhiEppines + Singapore<br />
+ Taiwan + Australia -f New Zeal<strong>and</strong> -i- Papua New Guinea Thail<strong>and</strong>.<br />
A SEA N (Association of Southeast Asian Nations): Brunei + Burma + Cambodia + Indonesia -I- Laos + Malaysia + Philippines -I- Singapore + Thafr<strong>and</strong> + Vietnam.<br />
CER (Closer Econoinic Relations): AustraHa H- New Zeal<strong>and</strong>.<br />
C ER /A FTA (CER <strong>and</strong> ASEAN Free Trade Area): CER -h ASEAN.
254 Production<br />
379 million m etric tons in 2000; Asia <strong>and</strong> Near East (Asia + Middle East + Caucasus<br />
repubEcs + central Asian republics) was 135.9 in 1961 <strong>and</strong> 362.2 m illion m etric tons<br />
in 2000; Asia + Oceania was 135.4 in 1961 <strong>and</strong> 361.7 m illion m etric tons in 2000; Asia<br />
(Greater China + northeastern, + southeastern, + <strong>and</strong> southern Asia) was 135.3 in<br />
1961 <strong>and</strong> 360.4 million m etric tons in 2000 to list the top five rice <strong>production</strong> regions<br />
defined hy milled <strong>production</strong>.<br />
Table 3.1.3 shows the rice regional milled <strong>production</strong> percent change from 1961<br />
in descending order. CER (Australia + New Zeal<strong>and</strong>) <strong>and</strong> Oceania (Australia + New<br />
Zeal<strong>and</strong> + other Oceania) heads the list with a 1211% increase in <strong>production</strong>. East<br />
Africa was third with a 564% increase, followed by Central America, 498% increase;<br />
North Africa, 405% increase; other South America, 388% increase; NIS/USSR, 363%<br />
increase; West Africa, 319% increase; Middle East <strong>and</strong> North Africa, 293% ; <strong>and</strong> Africa,<br />
293% increase.<br />
In 2000 rice producers raised rice on 148.5 million hectares in the less developed<br />
countries (Table 3.1.4) as compared to 111.6 mfllion hectares in 1961. The top 10 rice<br />
<strong>production</strong> regions ranked by hectares are listed in Table 3.1,5.<br />
TABLE 3.1.3. <strong>Rice</strong> Regional fHlilled Production, June 2000<br />
R egions"<br />
M ille d Production<br />
( % change<br />
from 1961)<br />
\<br />
R egions"<br />
M ilted Production<br />
( % change<br />
froth 1961)<br />
CER 1211.46 APEC 182.76<br />
Oceania 1211.46 Western hemisphere total 173.50<br />
East Africa 563.51 Foreign countries ■168.30<br />
Central Africa 497,83 Asia <strong>and</strong> Oceania 167.21<br />
North Africa 404.61 Asia <strong>and</strong> Near East 166.16<br />
Other South America 387,66 Asia 166.47<br />
NIS/USSR 362,50 Middle East 158.02<br />
West Africa 318.97 South America 157.79<br />
Middle East <strong>and</strong> North Africa 298.90 Latin America total 150.39<br />
Africa 292,87 South Asia 144.37<br />
Greater China 250.13 Southern Africa 122.50<br />
Subsaharan Africa 250.07 MERCOSUR 116.59<br />
Reorienting economies 242.21 Caribbean 78.85<br />
NAFTA 221.11 Europe 67.38<br />
North America 221.11 EU 15 59.46<br />
CER<strong>and</strong>AFTA 220.61 OECD 24.59<br />
ASEAN 216.86 Developed countries 24.25<br />
Central America 216.36 Asian NICS 23,80<br />
Transitioning economies 212.95 Northeast Asia -6.50<br />
Northern hemisphere Americas 205.44 Eastern Europe -56,25<br />
Southeast Asia 198.62<br />
PECC 188.96 World 169.23<br />
Less developed countries 184.65<br />
base, June 2000.<br />
"See Table 3.1.2 for a key to the regions.
Global <strong>Rice</strong> Production 255<br />
T A B L E 3.1.4. R ice R e g io n a l A re a H a rv e ste d , J u n e 2 0 0 0<br />
A rea<br />
Harvested<br />
A rea<br />
Harvested<br />
R egions" (ha) Regions" ( M<br />
Less developed 148476000 Other South America 1649000<br />
Asia <strong>and</strong> Near East 137040000 Southern Africa 1447000<br />
Asia <strong>and</strong> Oceania 136454000 Asian NICS 1412000<br />
Asia 136 268 000 North America 1317 000<br />
PECC 69 528 000 NAFTA 1317000<br />
APEC 61 149000 Middle East <strong>and</strong> North Africa 1274000<br />
South Asia 60095000 North Africa 659000<br />
Southeast Asia 424-21000 Middle East 615000<br />
Reorienting economies 40358000 Europe 611000<br />
CER<strong>and</strong>AFTA 34160000 Central Africa 540 000<br />
ASEAN 33 974 000 East Africa 475 000<br />
Greater China 30 000 000 EU15 396000<br />
Africa 7 326000 Transitioning economies 372000<br />
Western hemisphere total 6895000 NIS/USSR 349000<br />
Subsaharan Africa 6667 000 Central America 245000<br />
Latin America total 5665000 Caribbean 220000<br />
South America 5 113 000 CER 186000<br />
West Africa 4205 000 Oceania 186 000<br />
Nortlieast Asia 3 752000 Central Asian Republics 157000<br />
OECD 3 749 000 Eastern Europe 23000<br />
MERCOSUR 3704 000 Other European republics 2 2 0 0 0<br />
Developed countries 3 582000<br />
Northern hemisphere Americas 1782000 World 152058000<br />
Source: U.S. Department of Agriculture Economic Research Service Production, Supply, <strong>and</strong> Distribution (PS&D) Database,<br />
Jun e 2000,<br />
"See Table 3.1.2 for a key to the regions.<br />
Twenty regions have increased yields by over a 100% since 1961 (Table 3.1,6).<br />
Greater China has increased its yield 207% , followed by reorienting economies 188% ,<br />
Central America 160% , APEC 127% , PECC 125% , northern hemisphere Americas<br />
114.9% , Caribbean 114.6% , less developed 114% , western hemisphere total 112% ,<br />
Asia <strong>and</strong> Oceania 109% , Asia 108.8% , Asia <strong>and</strong> Near East 108.6% , Latin America total<br />
107.9% , South America 106.2% , foreign 105% , other South America 103% , Middle<br />
East <strong>and</strong> North Africa 101.6% , CER <strong>and</strong> AFTA 101.4% , Southeast Asia 100.6% , <strong>and</strong><br />
M ERCO SU R 100.4%.<br />
The <strong>production</strong> <strong>and</strong> processing o f rice has become so competitive that optimal<br />
yields will be required o f rice producers if they are to survive in the global marketplace.<br />
Greater China (China, Hong Kong, Macau) in 1961 produced 37.568 million m etric<br />
tons o f milled <strong>production</strong> on 26.291 million hectares for an average milled yield per<br />
hectare o f 1.4290 mt. In 2000 Greater China produced 131.537 million m etric tons o f<br />
milled <strong>production</strong> on 30 m illion hectares, for an average milled yield per hectare o f<br />
4.385 mt. Southeast Asia (Brunei, Burma/Myanmar, Cambodia/Kampuchea/Khmer<br />
Republic, Indonesia, Laos, Malaysia, Philippines, Singapore, Thail<strong>and</strong>, Vietnam) in<br />
1961 produced 31,291 m illion m etric tons o f milled <strong>production</strong> on 28.5 million<br />
hectares, for an average milled yield per hectare o f 1.098 mt. In 2000, Southeast Asia
256 Production<br />
iTin-<br />
TABLE 3.1.5. Top 10 <strong>Rice</strong> Production Regions, 2000<br />
R egions"<br />
"See Tabic 3.1.2. for a key to the regions.<br />
TABLE 3.1.6. <strong>Rice</strong> Regional Milled IHeld, June 2000<br />
M ille d Yield<br />
( % change<br />
Regions"<br />
irom 1961}<br />
R egions"<br />
Area<br />
Harvested (ha)<br />
Less developed countries 148476000<br />
Asia <strong>and</strong> Near East 137 040 000<br />
Asia <strong>and</strong> Oceania 136454000<br />
Asia 136268 000<br />
PECO 69 528 000<br />
APEC 61 149000<br />
South Asia 60 095 000<br />
Southeast Asia 42421000<br />
Reorienting economies 40358000<br />
CER <strong>and</strong> AFTA 34 160 000<br />
M ille d Yield<br />
( % change<br />
from 1961)<br />
Greater China 206.86 North Africa 78.40<br />
Reorienting economies 188.46 Middle East 72.44<br />
Central America 159,56 Asian NIGS 68.87<br />
APEC 126.77 West Africa 59.34<br />
PECC 124.95 NIS/USSR 56.39<br />
Northern hemisphere Americas 114.93 Africa 50.90<br />
Caribbean 114.62 OECD 47.76<br />
Less developed 113.91 Developed countries 47.08<br />
Western hemisphere total 111.99 Northeast Asia 42.82<br />
Asia <strong>and</strong> Oceania 109.23 Transitioning economies 42.19<br />
Asia 108.76 CER 41.02<br />
Asia <strong>and</strong> Near East 108.60 Oceania 41.02<br />
Latin America total 107.88 Subsaharan Africa 35.57<br />
South America 106.17 Southern Africa 26.70<br />
Foreign 104.87 East Africa 24,43<br />
Otlier South America 103.14 EU15 11.56<br />
Middle East <strong>and</strong> North Africa 101.60 Central Asian Republics 0.00<br />
CER <strong>and</strong> AFTA 101.43 Other European NIS republics 0,00<br />
Southeast Asia 100.64 Eastern Europe -3.00<br />
MERCOSUR 100.43 Central Africa -22.53<br />
ASEAN 99,92<br />
NAFTA 92.37 World 105.03<br />
North America 92,37<br />
South Asia 88.11<br />
base, June 2000.<br />
"See Table 3,1.2 for a key to the regions.
Global <strong>Rice</strong> Production 257<br />
produced 93.442 million m etric tons o f milled <strong>production</strong> on 42.421 m illion hectares,<br />
for an average milled yield per hectare o f 2.203 mt.<br />
The EU 15 [European Union = Austria, Belgium <strong>and</strong> Luxembourg, Denmark,<br />
Finl<strong>and</strong>, France, Germany, United Kingdom (begins 1991), former ERG (ends 1990),<br />
form er GDR (ends 1990), Greece, Irel<strong>and</strong>, Italy, Netherl<strong>and</strong>s, Portugal, Spain, Sweden,<br />
United Kingdom] exports 86% o f its rice <strong>production</strong>. Additional regions exporting<br />
over 40% o f their <strong>production</strong> include Europe 68% , Oceania 54% , CER 54% , <strong>and</strong><br />
North Am erica <strong>and</strong> NAFTA 41.64% (Table 3.1.7). Developed countries will find it<br />
increasingly difficult to compete with developing <strong>and</strong> transitioning economies as the<br />
world increasingly moves toward open trade in a global market. W ithout the need for<br />
food security, many countries would not even produce rice at some point in the future.<br />
RICE PRODUCTION BY COUNTRY<br />
The top 10 rice-producing countries are China, India, Indonesia, Bangladesh, V ietnam,<br />
Thail<strong>and</strong>, Burma Myanmar, Japan, Philippines, <strong>and</strong> Brazil. China’s averaged<br />
milled <strong>production</strong> in 2000 was 131.5 million m etric tons, China’s milled <strong>production</strong><br />
was 33.2% o f global <strong>production</strong>, India produced 21.6% , Indonesia 8.4% , Bangladesh<br />
6.1% , Vietnam 5.3% , Thail<strong>and</strong> 4,2% , Burma Myanmar 2.5% , Japan 2.2% , Philippines<br />
TABLE 3.1.7. <strong>Rice</strong> Regional Exports, June 2000<br />
Exports,<br />
Exports,<br />
Jan.-Dec.<br />
Jan.-Dec.<br />
( % o f<br />
( % o f<br />
R egions"<br />
M ille d )<br />
Regions"<br />
M ille d )<br />
EU 15 86.19 APEC 5.84<br />
Europe 67.56 Foreign countries 5.26<br />
Oceania 53.61 Asia <strong>and</strong> Oceania 4.77<br />
CER 53.61 Less Developed countries 4.74<br />
North America 41.64 Africa 4,60<br />
NAFTA 41.64 Asia 4.60<br />
Northern hemisphere Americas 36.19 Asia <strong>and</strong> Near East 4.59<br />
Developed countries 29.89 Central Asian republics 4.05<br />
OECD 29.03 Northeast Asia 4.03<br />
Other South America 23.06 Reorienting economies 3.73<br />
Western hemisphere total 20.10 NIS/USSR 3.00<br />
CERaiidAFTA 13.95 Transitioning economies 2.85<br />
ASEAN 13,33 South Asia 2.57<br />
North Africa 12.69 Middle East 1.98<br />
Southeast Asia 11.84 Central America 1.92<br />
MERCOSUR 10.82 Asian NICS 1.81<br />
South America 10.72 Greater China 1.37<br />
Latin America total 9.85<br />
Middle East <strong>and</strong> North Africa 9.72 World 5.85<br />
PECC 6.97<br />
S ou rce; US. Department of Agriculture Economic Researcli Service Production, Supply, <strong>and</strong> Distribution<br />
(PS&D) Database, June 2000.<br />
"See Table 3.1.2 for a key to tlie regions.
258 Production<br />
I:'<br />
íüÍLt :<br />
2% , <strong>and</strong> Brazil 1.85%, Since 1961j milled <strong>production</strong> In these top 10 rice-producing<br />
countries has increased by 250% in China, 140% in India, 245% in Indonesia, 150% in<br />
Bangladesh, 246% in Vietnam, 158% in Thail<strong>and</strong>, 143% in.Burm a Myanmar, —24%<br />
in Japan, 218% in Philippines, <strong>and</strong> 94% in Brazil.<br />
Since 1961, 12 countries have exp<strong>and</strong>ed <strong>production</strong> by over 500% , 27 countries<br />
increased <strong>production</strong> between 200 <strong>and</strong> 499% , 16 countries increased <strong>production</strong><br />
between 100 <strong>and</strong> 199% , 19 countries increased <strong>production</strong> less than 100%, <strong>and</strong><br />
in 13 countries, <strong>production</strong> declined. The 12 countries that exp<strong>and</strong>ed <strong>production</strong><br />
by over 500% are Cameroon 2067% , Uruguayl650% , Australia 1211% , Paraguay<br />
945% , Benin 900% , Venezuela 862% , Nigeria 773% , Bolivia 733% , Tanzania 603%,<br />
Sudan 600% , Togo 567% , <strong>and</strong> Niger 543% . The 13 countries that reduced <strong>production</strong><br />
were Bulgaria —87.5% , Algeria —83.3% , Romania —65% , Hungary —58% , Angola<br />
—52.6% , Honduras —38% , France —28.6% , Taiwan —28% , Swazil<strong>and</strong> —25% , Japan<br />
—24% , Portugal —21.7% , Gambia —21% , <strong>and</strong> Cuba —5.8% .<br />
^Vhich will be the m ajor rice-producing <strong>and</strong> rice-exporting countries 5 ,1 0 ,1 5 ,<br />
<strong>and</strong> 25 years from now? This is a difficult question. As countries increasingly embrace<br />
the global ecpnomy by lowering trade barriers <strong>and</strong> by producing products that<br />
sell at a profit in export markets, the order o f m ajor rice-producing countries in<br />
Table 3.1.8 will change more than one might expect, because our thought process<br />
is still tied to supply control <strong>and</strong> government protectionistic policies. The biggest<br />
roadblock to achieving m ajor advances in productivity will be countries trying to<br />
maintain their own traditional <strong>production</strong> areas. Tradition dies hard, <strong>and</strong> embracing<br />
tlie global econom y will for many simply not seem practical. This will be especially<br />
problematic in rice-producing countries that do not have a comparative advantage in<br />
rice <strong>production</strong>.<br />
Today s rice farm business environm ent is still rich in old econom y problems,<br />
such as trade barriers, political obstacles, <strong>and</strong> financial corruption. In short, today’s<br />
global rice farm business environment is extremely rich with individual country protectionism.<br />
The reality is that the current generation o f global rice producers are facing<br />
a dynamic <strong>and</strong> fluid farm business environment filled with uncertainty, where the<br />
low-cost producer survives. Their traditional or for U.S. producers pre-1996 farm bill<br />
business environment embraced supply control <strong>and</strong> certainty. In the newly emerging<br />
global marketplace, rice producers must achieve a level o f productivity <strong>and</strong> cost control<br />
that assures their future survivability. For these producers the future will be rich<br />
with opportunity.<br />
RICE AREA HARVESTED<br />
Table 3.1.9 shows 17 rice-producing countries where rice hectarage for crop year 2000<br />
exceedes 1 million hectares, <strong>and</strong> seven o f these countries have hectarage exceeding<br />
5 million hectares. The countries with hectarage exceeding 5 million hectares are<br />
India with 44,600,000 ha, China with 30,000,000 ha, Indonesia with 11,700,000 ha,<br />
Bangladesh with 10,700,000 ha, Thail<strong>and</strong> with 10,048,000 ha, Vietnam with 7,539,000<br />
ha, <strong>and</strong> Burm a Myanmar with 6,000,000 ha.<br />
Table 3.1.10 shows the percent change by country since 1961. Since 1961, the<br />
countries with over 5,000,000 million hectares exp<strong>and</strong>ed their rice hectarage as follows:<br />
India’s rice hectarage has exp<strong>and</strong>ed by 29% , China’s hectarage by 14%, Indonesia
Global <strong>Rice</strong> Production 259<br />
T A B L E 3.1.8. R ice P ro d u c tio n b y C ountry, J u n e 2 0 0 0<br />
M ille d Production<br />
% Change<br />
Countries metric tons % of W orld from 1961 (metric tons)<br />
China 131537 000 33.1683 '250.32 187 910 000<br />
India 85 500 000 21.5596 139.74 128 263 000<br />
Indonesia 33 110 000 8,3490 245.44 52 389 000<br />
Bangladesh 24000000 6.0518 149.53 36 004 000<br />
Vietnam 20 818 000 5.2494 245.93 31542 000<br />
Thail<strong>and</strong> 16 830 000 4.2438 157.93 25500000<br />
Burma Myanmar 9860000 2.4863 143.22 17000000<br />
Japan 8 636000 2.1776 -23.58 11863 000<br />
Philippines 8095000 2.0412 218.45 12454000<br />
Brazil 7336000 1.8498 94.13 10 788 000<br />
United States 6104000 1.5392 246.23 8 658000<br />
Korea, South 5 291000 1.3342 52.79 7199000<br />
Pakistan 4700000 U851 317.04 7051000<br />
Egypt 3 900000 0.9834 409.80 6 000 000<br />
Nepal<br />
Cambodia<br />
2 470000 0.6228 75.93 3 709 000<br />
3 762 000<br />
Kampuchea Khmer 2370 000 0.5976 53.00<br />
Nigeria 2 000 000 0.5043 773.36 3 333 000<br />
Sri Lanka 1940 000 0.4892 217.51 2853 000<br />
Madagascar 1700000 0.4287 127.58 2 656000<br />
EU 15 1593 000 0.4017 59.46 2442000<br />
Malaysia 1425 000 0.3593 114.61 2192000<br />
Korea, North 1350000 0.3404 18.94 1957000<br />
Taiwan 1342000 0.3384 -28.43 1906000<br />
Colombia 1325 000 0.3341 330.19 2208 000<br />
Australia 1259000 0.3175 1211.46 1761000<br />
Iran 1 132000 0.2854 183.00 1700 000<br />
Peru 1 1 1 0 0 0 0 0.2799 400.00 1609000<br />
Laos 930000 0.2345 164.96 1550 000<br />
Italy 728000 0.1836 48.57 1 179 000<br />
Uruguay 700000 0.1765 1650.00 1000000<br />
NIS/USSR 666000 0.1679 362.50 1026 000<br />
Spain 600000 0.1513 138.10 857000<br />
Venezuela 510 000 0.1286 862.26 752 000<br />
Mali 500 000 0.1261 309.84 758 000<br />
Guinea 475 000 0.1198 234.51 731000<br />
Tanzania 450 000 0.1135 603.13 6 8 8 0 0 0<br />
Côte DTvoire 445 000 0.1122 358.76 809000<br />
Argentina 400000 0.1009 238.98 615000<br />
Ecuador 400000 0.1009 308.16 678000<br />
Guyana 365000 0.0920 168.38 562000<br />
Russia 360000 0.0908 0 .0 0 554000<br />
Zaire 275000 0.0693 497.83 458000<br />
Mexico 270000 0.0681 21.62 405000<br />
Dominican Republic 250000 0.0630 228.95 385 000<br />
continued
TABU 3.1.8.<br />
RKe Production by C o -n tt )u.e 2000 (C o « t in ^<br />
M ille d Production<br />
Countries<br />
Sierra Leone<br />
Turkey<br />
Afghanistan<br />
Bolivia<br />
Costa Rica<br />
Liberia<br />
Iraq<br />
Panama<br />
Cuba<br />
Kazakstan<br />
Nicaragua<br />
M ozambique<br />
Ghana<br />
Paraguay<br />
Greece<br />
Suriname<br />
Senegal<br />
Portugal<br />
Uzbeldstan<br />
Guinea Bissau<br />
Chile<br />
Burkina<br />
Cam eroon<br />
Haiti<br />
France<br />
M auritania<br />
Chad<br />
Ukraine<br />
Niger<br />
Malawi<br />
M orocco<br />
El Salvador<br />
Togo<br />
Kenya<br />
Guatemala<br />
Trinidad <strong>and</strong> Tobago<br />
Turkm enistan<br />
Gambia<br />
Form er Yugoslavia<br />
Tajikistan<br />
Hungary<br />
Benin<br />
Angola<br />
Honduras<br />
Zambia<br />
metric tons<br />
230000<br />
230 000<br />
225 000<br />
200 000<br />
178 000<br />
160 000<br />
150 000<br />
146000<br />
130 000<br />
130 000<br />
127 000<br />
125000<br />
125000<br />
115 000<br />
110 000<br />
100 000<br />
98000<br />
90 000<br />
83 000<br />
SOQOO<br />
76000<br />
75 000<br />
65 000<br />
65 000<br />
65 000<br />
60 000<br />
60 000<br />
59000<br />
45 000<br />
45000<br />
40 000<br />
40 000<br />
40 000<br />
30 000<br />
23 000<br />
20 000<br />
18000<br />
15 000<br />
15 000<br />
11000<br />
10 000<br />
10 000<br />
9 000<br />
8 000<br />
7 000<br />
^ ° *''**<br />
0.0580<br />
0.0580<br />
0.0567<br />
0.0504<br />
0.0449<br />
0.0403<br />
0.0378<br />
0.0368<br />
0.0328<br />
0.0328<br />
0.0320<br />
0.0315<br />
0.0315<br />
0.0290<br />
0.0277<br />
0.0252<br />
0.0247<br />
0.0227<br />
0.0209<br />
0.0202<br />
0.0192<br />
0,0189<br />
0.0164<br />
0.0164<br />
0.0164<br />
0.0151<br />
0.0151<br />
0,0149<br />
0,0113<br />
0.0113<br />
0.0101<br />
0.0101<br />
0.0101<br />
0.0076<br />
0.0058<br />
0.0050<br />
0.0045<br />
0.0038<br />
0.0038<br />
0.0028<br />
0.0025<br />
0.0025<br />
0.0023<br />
0,0020<br />
0.0018<br />
% Change<br />
irom I W l<br />
30,68<br />
64.29<br />
8.70<br />
733.33<br />
394.44<br />
107.79<br />
248.84<br />
105.63<br />
^5.80<br />
0.00<br />
429.17<br />
58.23<br />
443.48<br />
945.45<br />
115.69<br />
122.22<br />
81.48<br />
^21.74<br />
0.00<br />
2.56<br />
11.76<br />
275.00<br />
2066.67<br />
80.56<br />
-28.57<br />
0.00<br />
275.00<br />
0.00<br />
542.86<br />
0.00<br />
300.00<br />
233.33<br />
566.67<br />
233.33<br />
155.56<br />
185.71<br />
0.00<br />
-21.05<br />
25.00<br />
0.00<br />
-58.33<br />
900.00<br />
-52.63<br />
-38.46<br />
0.00<br />
Rough Production<br />
(metric tons]<br />
383000<br />
354 000<br />
346000<br />
308 000<br />
274000<br />
267 000<br />
225 000<br />
225000<br />
200 000<br />
200 000<br />
195 000<br />
189000<br />
208 000<br />
- 172000<br />
169 000<br />
159 000<br />
151 000<br />
129 000<br />
. 128 OOO<br />
123 000<br />
119 000<br />
115 000<br />
108 000<br />
108 000<br />
108000<br />
88 000<br />
88 000<br />
91000<br />
68 000<br />
68000<br />
62 000<br />
62000<br />
61000<br />
45 OOO<br />
35 000<br />
32000<br />
28000<br />
24000<br />
25000<br />
17 000<br />
15 000<br />
16000<br />
15 000<br />
12000<br />
10000
Global <strong>Rice</strong> Production 261<br />
TABLE 3.1.8. <strong>Rice</strong> Production by Country, June 2000 ( C o n tin u e d )<br />
M ille d Production<br />
% Change<br />
R ough Production<br />
Countries<br />
metric tons<br />
% of W orld<br />
from 1961<br />
(metric tons)<br />
Romania 7000 0.0018 -65.00 11000<br />
Sudan 7000 0.0018 600.00 10000<br />
Kyrgystan 5 000 0.0013 0.00 8 000<br />
Somalia 4 000 0.0010 0.00 6000<br />
Brunei 4000 0.0010 33.33 6 000<br />
Swazil<strong>and</strong> 3 000 0.0008 -25.00 5000<br />
Bulgaria 3 000 0,0008 -87.50 5 000<br />
Algeria 1000 0,0003 -83.33 1000<br />
World 396 575 000 100.0000 169.23 590 125 000<br />
S ou rce: US, Department of Agriculture Economic Research Service Production, Supply, <strong>and</strong> Distribution<br />
(PSScD) Database, June 2000.<br />
hectarage by 71% , Bangladesh by 26% , Thail<strong>and</strong> by 63% , Vietnam by 58% , <strong>and</strong><br />
Burm a Myanmar by 41% . Ten countries exp<strong>and</strong>ed rice hectarage 400% or more:<br />
Paraguay 1186% , Australia 830% , Nigeria 792% , Uruguay 733% , Zaire 671% , Sudan<br />
600% , Bolivia 504% , Cam eroon 471% , Tanzania 449% , <strong>and</strong> Benin 400% , Seventeen<br />
countries exp<strong>and</strong>ed hectarage between 100 <strong>and</strong> 399% , 32 countries exp<strong>and</strong>ed liectarage<br />
less than 100% , <strong>and</strong> 25 countries reduced rice hectarage.<br />
In calendar year 2001, Thail<strong>and</strong> ranked first in rice exports, with 6.700 million<br />
m etric tons. Thail<strong>and</strong> exp<strong>and</strong>ed hectarage during the 1961-1999 period by 63% .<br />
Vietnam ranked second, with 3,800 m illion m etric tons <strong>and</strong> exp<strong>and</strong>ed hectarage<br />
during the time period by 58% . The United States ranked third in exports, with<br />
2.650 million m etric tons, <strong>and</strong> exp<strong>and</strong>ed hectarage by 91% . Pakistan ranked fourth,<br />
with 2250 million m etric tons, <strong>and</strong> exp<strong>and</strong>ed hectarage by 94% . China ranked fifth,<br />
with 1.800 million m etric tons, <strong>and</strong> exp<strong>and</strong>ed hectarage by 14% . India ranked sixth,<br />
with 1,800 m illion m etric tons, <strong>and</strong> exp<strong>and</strong>ed hectarage by 28% . Uruguay ranked<br />
seventh, with 0.700 million m etric tons, <strong>and</strong> exp<strong>and</strong>ed hectarage by 733% . Australia<br />
ranked eighth, with 0.675 m illion m etric tons, <strong>and</strong> exp<strong>and</strong>ed hectarage by 830% .<br />
Egypt ranked ninth, with 0.550 million m etric tons, <strong>and</strong> exp<strong>and</strong>ed hectarage by 187%.<br />
The trend in hectarage expansion is coming from nontraditional rice-producing<br />
countries that are taking advantage of <strong>technology</strong> to better feed their population<br />
<strong>and</strong> a global marketplace that is increasingly open to trade. The global export rice<br />
trend is toward increasing amounts o f rice moving into the export market. The trend<br />
is being driven by a global econom ic environment where countries ai'e increasingly<br />
liberalizing trade.<br />
In 1961, global rice exports were 4.31% o f milled rice. In 1997 <strong>and</strong> 1998, when<br />
world <strong>production</strong> was affected by catastrophic weather events, exports as a percent<br />
o f milled rice were 7.43% <strong>and</strong> 6.58% , respectively. In 2000, global rice exports were<br />
estimated at 5.85% . As countries embrace the new global econom y <strong>and</strong> lower trade<br />
barriers, one would expect those with a comparative advantage in rice <strong>production</strong> to<br />
exp<strong>and</strong> tlieir exports. '
262 Production<br />
TABLE 3.1.9. R ice H a rv e ste d H e ctare s a n d A cre s b y C ountry, Ju n e 2 0 0 0<br />
Area Harvested<br />
Countries hectares acres % of World<br />
' India 44 600 000 110 206 600 29.33<br />
China 30 000 OOO 74130 000 19.73<br />
Indonesia 11700 000 28 910 700 7.69<br />
Bangladesh 10 700 000 26439700 7.04<br />
Thail<strong>and</strong> 10 048 000 24 828 608 6.61<br />
Vietnam 7 539 000 18 628 869 4.96<br />
Burma Myanmar 6 000 000 14 826 000 3.95<br />
Philippines 4 019 000 9 930 949 2.64<br />
Ï u Brazil 3 338 000 8 248 198 2.20<br />
Pakistan 2 350 000 5 806 850 1.55<br />
i - Cambodia Kampuchea Khmer 1872 000 4625 712 1,23<br />
I Japan 1770 000 4 373 670 1.16<br />
i m Nigeria 1650 000 4 077150 1.09<br />
! 1|■ Nepal 1500 000 3 706 500 0.99<br />
United States 1230 000 3039 330 0.81<br />
I '<br />
1 i ’-’i hi Madagascar 1200 000 2 965 200 0.79<br />
$ !|- :i j<br />
, , ■1 Korea, South 1072 000 2 648 912 0.70<br />
hi ’ Sri Lanka 770 000 1902670 0.51<br />
1 pS Côte DTvoire 700 000 1729 700 0.46<br />
Nils! , . '' y Malaysia 665 000 1643 215 0.44<br />
■'1,<br />
1<br />
. Egypt 650 000 1606150 0.43<br />
liiMi Ä Laos 575 000 1420 825 0,38<br />
f'ili! . , Korea, North 570 000 1408 470 0.37<br />
1 ■’ i Zaire 540 000 1334340 0.36<br />
i 1 f<br />
ji'-'<br />
i i. i Guinea 475 000 1 173 725 0.31<br />
1 1 ! ' Tanzania 450 000 1 111950 0.30<br />
i ii' 1 ■ Colombia 430 000 1062 530 0.28<br />
1 Jlts' é ■...... Iran 425 000 1050175 0.28<br />
1 liil" ii; "i EU15 396 000 978 516 0.26<br />
I '<br />
■ ' :‘ Mah 375 000 926 625 0.25<br />
' -i NIS/USSR 349 000 862 379 0.23<br />
li 1 , Taiwan 340 000 840 140 0.22<br />
j t t Sierra Leone 275 000 679 525 0.18<br />
1 i ÏF- ; Peru 240 000 593 040 0.16<br />
I I<br />
,i: ; Italy 220 000 543 620 0.14<br />
1 1 1<br />
;! ■ ' Ecuador 205 000 506 555 0.13<br />
I I ; ' Australia 186 000 459 606 0.12<br />
1<br />
Mozambique 180 000 444780 0,12<br />
i<br />
i i 4, Afghanistan 175000 432425 0.12<br />
4? ;; Liberia 175 000 432425 0.12<br />
1 1 Russia 170 000 420070 0,11<br />
1 1 ' ■' , Venezuela 155 000 383 005 0.10<br />
1 1 : y- : Guyana 150 000 370 650 0.10<br />
1 1 tijji 4fi Uruguay 150 000 370650 0.10<br />
Bolivia 145 000 358 295 0.10<br />
ST| Ghana 130 000 321230 0.09<br />
iff<br />
continued
Global Rite Production 263<br />
TABLE 3.1,9. R k e H a rv e ste d H e c ta re s a n d A cre s b y Country^ J u n e 2 0 0 0 (Continued)<br />
Area Harvested<br />
Countries<br />
heclores<br />
Argentina 126 000<br />
Spain 115 000<br />
Iraq 110000<br />
Panama 90000<br />
Paraguay 90 000<br />
Cuba 90 000<br />
Mexico 87 000<br />
Dominican Republic 80000<br />
Turkey 80 000<br />
Senegal 75 000<br />
Guinea Bissau 70 000<br />
Kazakstan 70 000<br />
Costa Rica 65 000<br />
Nicaragua 60 000<br />
Chad 60000<br />
Suriname 55 000<br />
Uzbeldstan 50 000<br />
Togo 50 000<br />
Burldna 50000<br />
Cameroon 40 000<br />
Haiti 40 000<br />
Malawi 40 000<br />
Niger 30000<br />
Chile 29 000<br />
Mauritania 25 000<br />
Ukraine 22000<br />
Portugal 22 000<br />
Turlcmenistan 20 000<br />
Greece 20 000<br />
France 19000<br />
Zambia 15 000<br />
Kenya 15 000<br />
Gambia 15 000<br />
El Salvador 13 000<br />
Guatemala 13 000<br />
Tajildstan 12 000<br />
Former Yugoslavia 10 000<br />
Angola 10 000<br />
Trinidad <strong>and</strong> Tobago 10 000<br />
Benin 10 000<br />
Morocco 8 000<br />
Sudan 7 000<br />
Romania 6 000<br />
Kyrgystan 5 000<br />
Hungary 5 000<br />
Honduras 4 000<br />
acres<br />
311346<br />
284165<br />
271810<br />
222390<br />
222 390<br />
222 390<br />
214 977<br />
197680<br />
197680<br />
185 325<br />
172970<br />
172 970<br />
160615<br />
148 260<br />
148 260<br />
135 905<br />
123 550<br />
123 550<br />
123 550<br />
98 840<br />
98 840<br />
98 840<br />
74130<br />
71659<br />
61775<br />
54362<br />
54 362<br />
49420<br />
49420<br />
46949<br />
37065<br />
37065<br />
37065<br />
32123<br />
32123<br />
29 652<br />
24 710<br />
24710<br />
24 710<br />
24 710<br />
19768<br />
17297<br />
14 826<br />
12 355<br />
12 355<br />
9 884<br />
% of W orld<br />
0,08<br />
0.08<br />
0.07<br />
0.06<br />
0.06<br />
0.06<br />
0,06<br />
0.05<br />
0.05<br />
0.05<br />
0.05<br />
0.05<br />
0.04<br />
0.04<br />
0.04<br />
0.04<br />
0.03<br />
0.03<br />
0.03<br />
0.03<br />
0.03<br />
0.03<br />
0.02<br />
0.02<br />
0.02<br />
0.01<br />
0.01<br />
0.01<br />
0.01<br />
0.01<br />
0.01<br />
O.OI<br />
0.01<br />
0.01<br />
0.01<br />
0.01<br />
0.01<br />
0.01<br />
0.01<br />
0.01<br />
0.01<br />
0.00<br />
0.00<br />
0.00<br />
0.00<br />
0.00<br />
continued
264 Production<br />
TABLE 3.1.9.<br />
R ice H a rv e s t e d H e c ta re s a n d A c re s b y Country^ J u n e 2 0 0 0 (C ontinued)<br />
A rea Harvested<br />
Countries hectares acres % of World<br />
i l i i<br />
Somalia 3000 74Í3 0.00<br />
Brunei 3000 7413 0.00<br />
Swazil<strong>and</strong> 2 000 4942 0.00<br />
Bulgaria 2000 4942 0.00<br />
Algeria 1000 2471 0.00<br />
World 152058000 375735 318 100.00<br />
Source; U .S. D ep artm en t o f A griculture E co n o m ic Research Service Prod u ctio n , Supply, <strong>and</strong> D istribution<br />
(PS& D ) D atabase, June 2000.<br />
Table 3.1.11 shows rice exports as a percent o f milled rice <strong>production</strong>. The data<br />
are sorted from largest to smallest. In 2000 there were 31 countries that exported<br />
significant amounts o f rice. About half of these countries have the potential to become<br />
extremely aggressive in the export market.<br />
RICE MILLED YIELD AND MILLING RATE<br />
1 f? :<br />
i i<br />
The potential to exp<strong>and</strong> future rice <strong>production</strong> lies with the yield. Countries that are<br />
able to consistently produce high-yielding rice cultivars with superior grain quality<br />
are going to have an advantage over other countries. In 1961, the global milled rice<br />
per hectare was 1.272 m t, compared to 2.608 m t estimated for 2000. Thus rice milled<br />
yields improved 105% from 1961 to 2000.<br />
Australia ranks number 1 in milled yield per hectare, with an average yield of<br />
6.769 mt/ha, followed by Egypt at 6.000, Greece 5,5, Spain 5.217, M orocco 5,000,<br />
United States 4.963, South Korea 4.936, Japan 4,879, Uruguay 4.667, Peru 4.625, <strong>and</strong><br />
China 4.385, to list only a few (Table 3.1.12.). Australia’s average o f 6.769 mt/ha<br />
exceeds the 2000 global average by 160% . China has improved its average yield on<br />
30,000,000 ha 207% since 1961. The top 10 countries are listed in Table 3.1.13 by<br />
harvested hectares, milled yield, <strong>and</strong> as a percent o f China’s rice yield.<br />
Table 3.1.13. Top 10 <strong>Rice</strong>-Producing Countries by Area Harvested, Milled Yield,<br />
<strong>and</strong> Percent o f China’s Yield<br />
Given extremely low rice yields in many rice-producing countries, the potential<br />
for increasing rice productivity is extremely large. I f the countries listed in Table<br />
3.1.13, excluding China, increased their <strong>production</strong> to 3 m t o f milled rice per hectare,<br />
the change in world <strong>production</strong> would be significant. India would increase <strong>production</strong><br />
to 48.3 million m etric tons, or 57% ; Indonesia 6% ; Bangladesh 34% ; Thail<strong>and</strong> 79%;<br />
Vietnam 9%; Burma Myanmar 83% ; Philippines 49% ; Brazil 37% ; <strong>and</strong> Pakistan 50%.<br />
Countries that have improved their average yields per hectare by 100% or more<br />
since 1961 are as follows: Burkina 305% , Cameroon 279% , Venezuela 260% , Costa<br />
Rica 250% , China 207% , Laos 186%, Philippines 152% , M orocco 150% , Dominican<br />
Republic 139% , Greece 137%, Liberia 137% , Colombia 137% , Sri Lanka 135%, El<br />
Salvador 131% , Panama 129% , Vietnam 119% , Iraq 119% , Pakistan 116% , Nicaragua
Global Ríce Production 265<br />
TA B LE 3 .1 . 1 0 . R ice A r e a H a rv e ste d , J u n e 2 0 0 0<br />
Area<br />
Area<br />
Harvested<br />
Harvested<br />
( % c h a n g e ( % change<br />
Countries from 1961} Countries from 1961)<br />
Paraguay 1185.71 Guatemala 44.44<br />
Australia 830.00 El Salvador 44.44<br />
Nigeria 791.89 Malaysia 43.63<br />
Uruguay 733.33 EU 15 42.96<br />
Zaire 671 A3 Costa Rica 41.30<br />
Sudan 600.00 Burma Myanmar 41.04<br />
Bolivia 504.17 Dominican Republic 37.93<br />
Cameroon 471.43 Nepal 37.87<br />
Tanzania 448.78 Turkey 35.59<br />
Benin 400.00 Sri Lanka 35.33<br />
Ghana 364.29 India 28.55<br />
Côte DTVoire 239.81 Philippines 26.42<br />
Niger 233.33 Bangladesh 26.13<br />
Togo 233.33 Guinea Bissau 14.75<br />
Peru 196.30 China 14.17<br />
NIS/USSR 195.76 Korea, North 9.62<br />
Egypt 187.61 Senegal 2.74<br />
Chad 172,73 Brazil -0.36<br />
Venezuela 167.24 Sierra Leone -2,83<br />
Nicaragua 150.00 Korea, South -4.96<br />
Kenya 15Q.00 Laos -7.26<br />
Argentina 137.74 Burkina -7.41<br />
Mozambique 125.00 Greece -9.09<br />
Mali 120.59 Panama -10.00<br />
Ecuador 115.79 Liberia -12.50<br />
Suriname 111.54 Cambodia Kampuchea Khmer -14.21<br />
Trinidad <strong>and</strong> Tobago 100.00 Afghanistan -16.67<br />
Pakistan 93.57 Haiti -16.67<br />
United States 91.29 Chile -25.64<br />
Spain 88.52 Gambia -37.50<br />
Guinea 82.69 Cuba -40.00<br />
Colombia 81.43 Mexico -40.41<br />
Italy 78.86 Portugal -42.11<br />
Indonesia 70.63 France -42.42<br />
Madagascar 67.36 Romania -45.45<br />
Former Yugoslavia 66.67 Japan -46.38<br />
Thail<strong>and</strong> 62.62 Algeria -50.00<br />
Morocco 60,00 Taiwan -56.58<br />
Iraq 59.42 Angola -60.00<br />
Vietnam 58.28 Honduras -69.23<br />
Iran 51,79 Hungary -77,27<br />
Guyana 47.06 Bulgaria -83,33<br />
Source: U.S. Department of Agriculture Economic Research Service Production, Supply, <strong>and</strong> Distribution<br />
(PS&D) Database, June 2000.
R ice E xports, Ju n e 2 0 0 0<br />
Exports,<br />
Exports,<br />
Jan."D ec.<br />
Jon.-Dec,<br />
( % o f<br />
( % o f<br />
Countries<br />
m illed)<br />
Countries<br />
milled)<br />
France 107.69 Egypt 12.82<br />
Uruguay 100.00 Taiwan 8.94<br />
EU 15 86,19 Kazakstan 7.69<br />
Italy 85.16 Japan 6.37<br />
Australia 53.61 Costa Rica 5.62<br />
Spain 51.67 Portugal 5.56<br />
Argentina 50.00 Peru 4.50<br />
Guyana 47.95 Burma Myanmar 3.55<br />
Pakistan 47.87 NIS/USSR 3.00<br />
Greece 45.45 Russia 2.78<br />
United States 43.41 Mexico 1.48<br />
Thail<strong>and</strong> ' 39.81 China 1.37<br />
Ecuador 25,00 India 0.94<br />
Suriname 25.00 Cambodia Kampuchea Khmer 0.42<br />
Vietnam 19.21 Brazil 0.34<br />
Venezuela 15.69<br />
S ou rce: U .S Department of Agriculture Economic Research Service Production, Supply, <strong>and</strong> Distribution<br />
(PS&D) Database, June 2000.<br />
112%, Haiti 117% , Uruguay 110% , Mexico 104% , Indonesia 102% , Benin 100%, Togo<br />
100%, <strong>and</strong> Honduras 100%.<br />
Table 3,1.14 shows by country milled rice as a percentage o f rough, sorted from<br />
highest to lowest. The U.S, St<strong>and</strong>ards definition for milled rice is whole or broken<br />
kernels o f rice (Oryza sativa L.) from which the hulls <strong>and</strong> at least the outer bran<br />
layers have been removed <strong>and</strong> which contain not m ore than 10.0% o f seeds, paddy<br />
kernels, or foreign material, either singly or combined. South Korea had a rice milled<br />
yield o f 73.5% , followed by Japan with 72.8% , Australia 71.5% , United States 70,5%,<br />
Taiwan 70.41% , Spain 70,1% , China 70% , Sudan 70% , Uruguay 70% , Zambia 70%,<br />
<strong>and</strong> Portugal 69,77% .<br />
T A B L E 3 .1 .1 2 . R ice M ille d Y ie ld b y Country^ Ju n e 2 0 0 0<br />
M ille d Yield<br />
M ille d Yield<br />
% C h ange from<br />
% C hange from<br />
Countries<br />
mt/ha<br />
1961 Countries mt/ha<br />
1961<br />
Australia 6.769 41.02 Guatemala 1.769 76.90<br />
Egypt 6.000 77.25 Thail<strong>and</strong> 1.675 58.62<br />
Greece 5.500 137.27 Uzbekistan 1.660 0.00<br />
Spain 5.217 26.29 Nepal 1.647 27,67<br />
Morocco 5.000 150.00 Burma Myanmar 1.643 72.40<br />
continued
Global <strong>Rice</strong> Production 267<br />
TABLE 3.1.12.<br />
<strong>Rice</strong> MilJed Yield by Country^ June 2000 (Continued)<br />
M ille d Yield<br />
M ille d Yield<br />
% C h an ge from<br />
% C h a n ge from<br />
Countries<br />
mt/fia<br />
1961 Countries mt/ha<br />
1961<br />
United States 4.963 81.00 Haiti 1.625 116.67<br />
Korea, South 4.936 60.78 Cameroon 1,625 278.79<br />
Japan 4.879 42.49 Panama 1.622 128.45<br />
Uruguay 4.667 110.04 Laos 1.617 185.69<br />
Peru 4.625 68.73 Bulgaria 1.500 -25.00<br />
China 4.385 206,86 Swazil<strong>and</strong> 1.500 -25.00<br />
Portugal 4.091 35.19 Niger 1.500 92.80<br />
BU15 4.023 11.56 Burkina 1.500 305.41<br />
Taiwan 3.947 64.80 Former Yugoslavia 1.500 -25.00<br />
France 3.421 24.04 Cuba 1.444 56.96<br />
Italy 3.309 -16.94 Madagascar 1.417 35.99<br />
Venezuela 3.290 259,96 Bolivia 1.379 37.90<br />
Argentina 3.175 42,63 Iraq 1.364 118.94<br />
Dominican Republic 3.125 138.55 Mali 1.333 85,65<br />
Mexico 3.103 104.01 Somalia 1.333 0,00<br />
Colombia 3.081 137.00 Brunei 1.333 33.30<br />
El Salvador 3.077 130.83 Senegal 1,307 76.62<br />
Turkey 2.875 21.15 Afghanistan 1.286 30.43<br />
Indonesia 2.830 102.43 Paraguay 1.278 -18.65<br />
Vietnam 2.761 118.61 Cambodia Kampuchea Khmer 1,266 78.31<br />
Costa Rica 2,738 249.68 Nigeria 1.212 -2,10<br />
Ukraine 2.682 0.00 Romania 1.167 -35.81<br />
Iran 2.664 86.42 Guinea Bissau 1.143 -10.63<br />
Chile 2.621 50.29 Malawi 1.125 0.00<br />
Sri Lanka 2.519 134.54 Tanzania 1.000 28.21<br />
Guyana 2.433 82.52 Sudan 1.00 0.00<br />
Mauritania 2.400 0.00 Kyrgystan 1.00 0.00<br />
Korea, North 2.368 8.47 Algeria 1.00 -66.67<br />
Bangladesh '2.243 97,80 Guinea 1.00 83.15<br />
Brazil 2.198 94.86 Gambia 1.00 26.26<br />
Malaysia 2.143 49.44 Benin 1.00 100.00<br />
Russia 2.118 0,00 Chad 1.00 37.55<br />
Nicaragua 2.117 111.70 Ghana 0.962 17,17<br />
Philippines 2.014 151.75 Tajildstan 0.917 0.00<br />
Honduras 2.000 100.00 Liberia 0.914 137.40<br />
Pakistan 2.000 115.52 Angola 0.900 18.42<br />
Hungary 2.000 83.32 Turkmenistan 0.900 0.00<br />
Kenya 2.000 33.33 Sierra Leone 0.836 34.41<br />
IVinidad <strong>and</strong> Tobago 2.000 42.86 Togo 0.800 100.00<br />
Ecuador 1.951 89.05 Mozambiqe 0.694 -29.76<br />
India 1.917 86.48 Côte DTvoire 0,636 35.03<br />
NIS/USSR 1.908 56.39 Zaire 0.509 -22.53<br />
Kazakstan 1.857 0.00 Zambia<br />
Suriname 1.818 5.03<br />
0.467 0.00<br />
Source: US. Department of Agriculture Economic Research Service Production, Supply, <strong>and</strong> Distribution (PS&D) Database,<br />
June 2000.
Production<br />
TABLE 3.1.13. Top 10 <strong>Rice</strong>-Producing Countries by Area Harvested,<br />
M illed Yield, <strong>and</strong> Percent o f China's Yield<br />
Area<br />
M ille d Yield<br />
Harvested<br />
Percent<br />
Country (ha) mt/ha of China<br />
India 44 600 000 1.917 44<br />
China 30 000 000 4.385 — .<br />
Indonesia 11700 000 2.830 65<br />
Bangladesh 10 700 000 2.243 51<br />
Thail<strong>and</strong> 10 048 000 1.675 38<br />
Vietnam 7 539 000 2.761 63<br />
Burma Myanmar 6 000 000 1.643 37<br />
Philippines 4 019000 2.014 46<br />
Brazil 3 338000 2.198 50<br />
Pakistan 2 350 000 2.000 46<br />
-<br />
TA B LE 3 .1 .1 4 . R ice M ille d , J u n e 2 0 0 0<br />
M ille d<br />
Countries [% of rough) Countries<br />
:■ ; 11<br />
!, : ;<br />
i, ^^<br />
■■i'i -<br />
I ' j :<br />
i<br />
!<br />
i<br />
i<br />
iä t i i ■<br />
I - ■<br />
H ' f " '<br />
Korea, South<br />
Japan<br />
Australia<br />
United States<br />
Taiwan<br />
Spain<br />
Sudan<br />
Uruguay<br />
China<br />
Zambia<br />
Portugal<br />
Peru<br />
Korea, North<br />
Mauritania<br />
Chad<br />
Brazil<br />
Sri Lanka<br />
Venezuela<br />
Paraguay<br />
Iraq<br />
Somalia<br />
Hungary<br />
Brunei<br />
Mexico<br />
Kenya<br />
Honduras<br />
73.50<br />
72.80<br />
71.49<br />
70.50<br />
70.41<br />
70.01<br />
70.00<br />
70.00<br />
70.00<br />
70.00<br />
69.77<br />
68.99<br />
68.98<br />
68.18<br />
68.18<br />
68.00<br />
68.00<br />
67.82<br />
66.86<br />
66.67<br />
66.67<br />
66.67<br />
66.67<br />
66.67<br />
66.67<br />
66.67<br />
Cuba<br />
Kazakstan<br />
Egypt<br />
Philippines<br />
Russia<br />
Guinea<br />
Turkey<br />
Costa Rica<br />
Guyana<br />
Dominican Republic<br />
Bolivia<br />
NIS/USSR<br />
Senegal<br />
Panama<br />
Uzbekistan<br />
Ukraine<br />
Tajikistan<br />
El Salvador<br />
Morocco<br />
Turkmenistan<br />
Madagascar<br />
Chile<br />
Romania<br />
Indonesia<br />
Cambodia Kampuchea Khmer<br />
Suriname
TABLE 3.1.14. R ie e A liile j June 2000 ( C o n tin u e d )<br />
M illed<br />
( % of rough}<br />
65.00<br />
65.00<br />
65.00<br />
65.00<br />
64.98<br />
64.98<br />
64.97<br />
64.96<br />
64.95<br />
64.94<br />
64.94<br />
64.91<br />
64.90<br />
64.89<br />
64.84<br />
64.84<br />
64.71<br />
64.52<br />
64.52<br />
64.29<br />
64.01<br />
63.87<br />
63.64<br />
63.20<br />
63.00<br />
62.89<br />
continued<br />
Counfries<br />
India<br />
Bangladesh<br />
Pakistan<br />
Nepal<br />
Iran<br />
Niger<br />
Malawi<br />
Mozambique<br />
Vietnam<br />
Thail<strong>and</strong><br />
Mali<br />
Guatemala<br />
Togo<br />
Tanzania<br />
EU 15<br />
Burkina<br />
Nicaragua<br />
Greece<br />
Argentina<br />
Guinea Bissau<br />
Afghanistan<br />
Malaysia<br />
M ille d<br />
{% of rough)<br />
66.66<br />
66.66<br />
66.66<br />
66.59<br />
66.59<br />
66.18<br />
66.18<br />
66.14<br />
66.00<br />
66.00<br />
65.96<br />
65.71<br />
65.57<br />
65.41<br />
65.23<br />
65.22<br />
65.13<br />
65.09<br />
65.04<br />
65.04<br />
65.03<br />
65.01<br />
Source; U.S. Department of Agriculture<br />
(PS8rD) Database, June 2000,<br />
Countries<br />
Gambia<br />
Trinidad <strong>and</strong> Tobago<br />
Benin<br />
Krygystan<br />
Italy<br />
Prance<br />
Haiti<br />
Cameroon<br />
Ghana<br />
Sierra Leone<br />
Zaire<br />
Colombia<br />
Nigeria<br />
Swazil<strong>and</strong><br />
Angola<br />
Laos<br />
Bulgaria<br />
Former Yugoslavia<br />
Liberia<br />
Ecuador<br />
Burma Myanmar<br />
Cote D’Ivoire<br />
M ille d<br />
( % o f rough)<br />
Economic Research Service Production. Supply, <strong>and</strong> Distribution
chapter<br />
3.2<br />
Ríce Production<br />
J o e E. Street<br />
Research <strong>and</strong> Extension Center<br />
Mississippi State University<br />
Stoneville, Mississippi<br />
P a trick K. B o llic h<br />
<strong>Rice</strong> Research Station<br />
Louisiona State University Agricultural Center<br />
Crowley, Louisiana<br />
INTRODUCTION<br />
LAND SELECTION AND FORMATION<br />
Topography <strong>and</strong> Soil Type<br />
L<strong>and</strong> Leveling<br />
Levee Construction<br />
WATER REQUIREMENTS<br />
Water Source<br />
Water Quality<br />
Water Temperature<br />
Water Volume<br />
Water Conservation<br />
Short-Term Toctics<br />
Long-Term Tactics<br />
PU N T IN G METHODS<br />
Water-Seeded <strong>Rice</strong><br />
Dry-Seeded <strong>Rice</strong><br />
WATER MANAGEMENT<br />
TILLAGE PRACTICES<br />
PLANTING DATES<br />
SEEDING RATES<br />
CULTIVARSELEaiON<br />
Grain Type<br />
CROP ROTATIONS AND DOUBLE-CROPPING<br />
RATOON PRODUCTION<br />
HARVEST OPERATION<br />
Drying <strong>Rice</strong><br />
REFERENCES<br />
SUGGESTED READING<br />
<strong>Rice</strong>: Origiii) History, Technology, <strong>and</strong> Production, edited by C. Wayne <strong>Smith</strong><br />
ISBN 0-471-34516-4 © <strong>2003</strong> John Wiley & Sons, Inc.<br />
271
272 Production<br />
INTRODUCTION<br />
"in-;;:?<br />
<strong>Rice</strong> <strong>production</strong> in the United States is concentrated primarily in the states o f Arkansas,<br />
Louisiana, Mississippi, Missouri, Texas, California, <strong>and</strong> a small hectarage in<br />
Florida. Econom ical <strong>production</strong> o f rice generally requires high average temperatures<br />
during the growing season, a plentiful supply o f water applied in a timely fashioUj..<br />
a smooth l<strong>and</strong> surface with less than 1% slope to facilitate uniform flooding ^rid<br />
drainage, <strong>and</strong> a subsoil hardpan tliat inhibits percolation o f water. These physical<br />
dem<strong>and</strong>s for growing rice limit its <strong>production</strong> range; however, physical suitability<br />
only sets the upper range on the size o f the rice-producing area; econom ic factors<br />
determine the area in <strong>production</strong> (Setia et al., 1994). /<br />
Inform ation on rice <strong>production</strong> in this chapter has been gathered iy' part from<br />
the <strong>production</strong> h<strong>and</strong>books o f the rice-growing states o f Arkansas (Helmes^<strong>and</strong> Slaton,<br />
1996), California (Canevari <strong>and</strong> Weir, 1992), Louisiana (Linscombe et a l, 1999),<br />
Mississippi (Miller <strong>and</strong> Street, 1999), <strong>and</strong> Texas (Klosterboer <strong>and</strong> Turner, 1999).<br />
LAND SELECTION AND FORMATION<br />
Topography <strong>and</strong> Soil Type<br />
ii'SN- I<br />
IIT-<br />
Although primarily alluvial in <strong>origin</strong>, soils used for rice <strong>production</strong> in the United<br />
States vary considerably in characteristics. Regardless o f soil texture, the presence<br />
of an impervious subsoil laypr in the form o f a fragipan, claypan, or massive clay<br />
horizon is necessary to minimize percolation o f irrigation water. Clays, clay loams,<br />
sUty clay loams, or silt loams are considered the m ost desirable soil types because<br />
they prevent excessive losses due to water seepage (Mikkelson <strong>and</strong> Evatt, 1973). Other<br />
sohs, including organic soils, can be used if they have a clay pan or hardpan that<br />
can maintain up to 2.5 cm (6 in.) o f floodwater. Deep s<strong>and</strong>y loam soils generally are<br />
not recommended for rice <strong>production</strong> because they lack the water-holding capacity<br />
necessary to m aintain a flood.<br />
<strong>Rice</strong> will grow well over a relatively wide pH range o f 5 to 7.5, although the best<br />
soils are slightly acidic (pH 5.5 to 6.6) (M artin et al., 1976). Flooding will temporarily<br />
shift the soil pH toward neutrality <strong>and</strong> allows a release o f available soil phosphorus.<br />
The shift can range from 0.5 to 2.0 pH units, depending on how acidic or alkaline<br />
the soil was prior to flooding. The organic matter <strong>and</strong> the chemical properties of the<br />
soil influence this change in pH (Mikkelson <strong>and</strong> Evatt, 1973). Soils with a high pH<br />
may cause <strong>production</strong> problems by reducing the availability o f plant nutrients such<br />
as zinc <strong>and</strong> iron. On silt or s<strong>and</strong>y loam soils, zinc deficiency may be induced as pH is<br />
increased above 6.5. Continuous use o f am m onium sources o f nitrogen (ammonium<br />
sulfate, urea, <strong>and</strong> anhydrous <strong>and</strong> aqua ammonia) may cause the pH o f the soil to shift<br />
as m uch as 2 pH units toward acidic.<br />
l i ; '<br />
L<strong>and</strong> Leveling<br />
Although an expensive practice that requires annual maintenance in order to utilize<br />
its full potential, precision l<strong>and</strong> leveling (Figure 3.2,1) is one o f the m ost beneficial
Ríce Production 273<br />
1<br />
Figure 3.2,1.<br />
L<strong>and</strong>-leveling equipment used to put rice l<strong>and</strong> to grade.<br />
practices that a farmer can carry out (Ellis, 1982). L<strong>and</strong> that is properly leveled drains<br />
quicker in the spring, so that seedbed preparation can begin earlier, makes it possible<br />
to maintain a uniform water depth o f 2 to 4 inches within the levees, <strong>and</strong> has better<br />
flooding <strong>and</strong> drainage cliaracteristics (Johnston <strong>and</strong> Miller, 1973). In properly leveled<br />
fields, irrigation levees can be constructed straight <strong>and</strong> perpendicular to the slope o f<br />
the l<strong>and</strong>. This reduces the am ount o f l<strong>and</strong> devoted to levees <strong>and</strong> decreases tillage <strong>and</strong><br />
harvest cost. Precision l<strong>and</strong> leveling also reduces the cost o f locating levees <strong>and</strong>, in<br />
general, allows for better water management that improves weed control <strong>and</strong> produces<br />
higher yields.<br />
Precision l<strong>and</strong> leveling does not mean that the l<strong>and</strong> surface is absolutely level or<br />
flat, since some slope or grade is desirable for good surface drainage. It is generally<br />
recommended that l<strong>and</strong> planted in rice be leveled to a uniform grade o f 0.2% (0.2 ft<br />
per 100 ft) or less slope, to achieve the necessary drainage <strong>and</strong> reduce the num ber of<br />
levees required. After a field is adequately graded, it can 1^ maintained by annual l<strong>and</strong><br />
planing or floating before seeding the rice.<br />
Wafer Leveling<br />
The practice of water leveling has proven to be a tremendous benefit to the rice<br />
industry in southwestern Louisiana. Early attempts to level rice l<strong>and</strong> consisted o f<br />
using l<strong>and</strong> planes, but little could be done to change natural slopes. In the 1960s,<br />
the practice o f leveling in the water was developed (Faulkner, 1965). This procedure<br />
allowed the farm er to construct levees in areas o f the field other than on the natural<br />
contour, with leveling carried out between the levees. The silt loam soils typical o f<br />
this coastal prairie area were ideal for this type o f l<strong>and</strong>-form ing activity. The shallow,<br />
clay hardpan supported tractors <strong>and</strong> leveling equipment, while the water wave action<br />
created by the tractors helped to keep the suspended topsoil in place while the plow<br />
sole was moved. Reductions in water requirements, fewer levees, improved flooding<br />
<strong>and</strong> drainage, improved planting <strong>and</strong> harvesting practices, <strong>and</strong> higher grain yields<br />
continue to make water leveling a very popular practice in southwestern Louisiana.
274 Production<br />
mm<br />
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N # ./<br />
A recent innovation in water leveling is the use o f laser <strong>technology</strong>, <strong>origin</strong>ally<br />
developed for dryl<strong>and</strong> leveling. Water leveling coupled with a laser system results in<br />
more precise changes in l<strong>and</strong> surfaces than could be obtained with manually controlled<br />
systems. An added benefit is the movement o f large amounts o f soil with lower<br />
horsepower requirements than is needed with dry leveling.<br />
Levee Construction<br />
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Accurate surveying is essential for maintaining a uniform flood <strong>and</strong> basic to good<br />
water management in rice. Surveying is used to locate irrigation canals, drainage<br />
ditches, <strong>and</strong> field levees. If canals, ditches, <strong>and</strong> levees are not located properly, losses<br />
can occur due to faulty irrigation <strong>and</strong> poor drainage. Irrigation canals should be<br />
large enough to supply ample water promptly when needed, whereas drainage ditches<br />
should be large enough to dispose o f water rapidly (Johnston <strong>and</strong> Miller, 1973).<br />
Construction o f levees is the key method for regulation o f water depth in rice fields<br />
(Figure 3.2.2). Levees are used to divide rice fields into subfields called bays or cuts<br />
in the United States <strong>and</strong> generally surveyed on a contour at vertical intervals of 0.1<br />
to 0,2 ft between levees. W hen surveying, a shallow furrow is com monly made on a<br />
contour o f the vertical intervals. The furrow acts as a guide for levee construction.<br />
^Vllen fields have been l<strong>and</strong>-formed for straight levees, <strong>and</strong> the grade maintained,<br />
levees can simply be placed by measuring a determined distance between them.<br />
Immediately after planting dry seeded rice, levee construction should begin over<br />
the contour furrow. Levees must be v/eU constructed to achieve <strong>and</strong> regulate a uniform<br />
water depth within each bay. Normally, on heavy clay soils, four to five passes with a<br />
levee disk are required to achieve the desired height o f 51 to 61 cm (20 to 24 in. ). Levees<br />
should be compact <strong>and</strong> high enough to hold 7 to 15 cm (3 to 6 m .) o f floodwater in<br />
a bay.<br />
The levees should be seeded just before or after the final pass with the levee disk<br />
for sût loam <strong>and</strong> clay soils, respectively. Levees on clay soils should be packed with a<br />
# ;<br />
!y.'<br />
Figure 3.2.2.<br />
<strong>Rice</strong> levee construction with a levee plow.<br />
m t
<strong>Rice</strong> Production 275<br />
spool-shaped levee packer before they are planted. After the field levees are completed,<br />
the perimeter levees are constructed <strong>and</strong> seeded in a sim ilar way. Approximately 7 to<br />
10 days before an anticipated flooding, field levees are joined to the perimeter levee.<br />
In fields with large bays, where levees run parallel to the direction o f prevailing<br />
winds, one or more wind levees should be constructed at a right angle to the prevailing<br />
wind to prevent the wind from “stacking” the flood on one end o f the bay. These levees<br />
are not tied to the levees constructed around the perimeter o f the field.<br />
Levee gates are installed to control water depth in each bay. They should be<br />
installed soon after levee construction is complete in case flushing is necessary <strong>and</strong><br />
to provide outlets that are necessary to prevent levee washout in the event of a heavy<br />
rain. Levee gates are com m only made o f plastic or metal <strong>and</strong> are usually installed 2 to<br />
10 days after planting (Figures 3.2.3 <strong>and</strong> 3.2.4). Gates should be installed in the field<br />
levees a few meters from the perimeter levee in a location that will make flood control<br />
Figure 3.2.3.<br />
Hostie levee gotes installed.<br />
Figure 3.2.4.<br />
Metal levee gate installed.
easy. Usually, one gate per levee is adequate; however, the Brst two to four levees near<br />
the water source may require two gates or one extrawide gate to h<strong>and</strong>le the water<br />
supply. In larger bays (greater than 25 ac or 10 ha), two gates are necessary, for more<br />
effective flood distribution. The need for extra gates obviously will depend on the size<br />
o f bays in the vicinity of the water source <strong>and</strong> the volume of water being discharged.<br />
To allow excess rain from every two or three bays to be diverted into an outside<br />
drainage ditch, wider gates, or emergency spillways or overflows, may need to be<br />
installed in every second or third bay. Excess water can be diverted from the rice field<br />
into drainage canals from the lowest bay by means o f a gate or gates installed in the<br />
perimeter levee.<br />
WATER REQUIREMENTS<br />
An ample supply of water <strong>and</strong> timely flooding o f fields are essential for optimum<br />
rice <strong>production</strong>. Sufficient water for flooding provides a favorable environment for<br />
rice growth, helps control weeds, <strong>and</strong> stabilizes soil am m onium nitrogen. To produce<br />
a rice crop in the southern region o f the United States, 1000 to 2500 mVha (24 to<br />
60 acre-in.) o f water are required per year (M artin et a l, 1976). About 250 to 850<br />
m^/ha (6 to 20 acre-in.) generally are supplied by rainfall during the growmg season,<br />
<strong>and</strong> the remaining water is supphed by irrigation (Figure 3.2.5). O n an average rice<br />
soil, about 3047 mVha (1 acre-ft) of water is required to prime the soil <strong>and</strong> flood the<br />
bays to a depth o f 15 cm (6 in,). After a rice field is flooded, a considerable amount<br />
o f water is required to mainta'in an optim um depth in the field because of losses<br />
due to transpiration from the plant leaf surface, evaporation from the water surface,<br />
downward percolation or movement o f water through the soU profile due to gravity<br />
or hydrostatic pressure, <strong>and</strong> runoff of excess water over field levees (De Datta, 1981).<br />
During a 4-year survey in Mississippi from 1991 to 1994, the overall water use on<br />
a contour-level field was 7897 mVha (31.1 in./acre). Average water use on straightleveed<br />
rice fields was 7338 mVha (28.9 in./acre) (Cooke et al., 1996),<br />
Figure 3,2.5,<br />
Woter from riser entering rice field.
Rite Production 277<br />
Water Source<br />
All o f the rice hectarage in the United States is irrigated. The water comes from deep<br />
or shallow underground wells, runoff reservoirs, rivers, bayous, lakes, <strong>and</strong> drainways.<br />
The main water source differs from region to region (Setia et aL, 1994). O n-farm wells<br />
are the m ajor source o f irrigation water in the Arkansas non-D elta <strong>and</strong> Mississippi<br />
River Delta, <strong>and</strong> to a lesser extent, in southwestern Louisiana <strong>and</strong> the lower Texas Gulf<br />
coast. In California <strong>and</strong> the upper coast o f Texas, m ost o f the rice hectarage receives<br />
water purchased from canal companies, associations, or irrigation districts.<br />
Water Quality<br />
The quality o f water available for irrigation is very im portant for successful rice <strong>production</strong>.<br />
The source <strong>and</strong> chemical composition o f rice irrigation water should be<br />
considered from both the immediate effect on the current crop <strong>and</strong> the long-range<br />
productivity o f the soil (Kapp, 1947). The characteristics that determine the quality<br />
o f irrigation water include total concentration o f soluble salts, relative proportion of<br />
sodium to other cations, concentration o f boron or other toxic elements, <strong>and</strong> under<br />
some conditions, the bicarbonate concentration relative to the concentration o f calcium<br />
<strong>and</strong> magnesium. Initial salinity o f the flooded soil, the effect o f internal drainage<br />
on the flooded soil, <strong>and</strong> the total salt content o f the soil are other considerations.<br />
Although a large part o f tlie rice hectarage in Arkansas <strong>and</strong> Louisiana is irrigated<br />
with water from wells with low concentrations o f chlorides (Adair <strong>and</strong> Engler,<br />
1955), water from coastal bayous used for irrigation may become excessively salty<br />
by the invasion o f seawater during periods o f low rainfall. High concentration of<br />
salts can accumulate in the soil when irrigation water contains high quantities o f<br />
soluble salts. These concentrations o f salt can be injurious to the rice plant, especially<br />
in the germination, early-tillering, <strong>and</strong> flowering growth stages. Although the rice<br />
plant can tolerate higher concentrations o f salt in the later stages o f growth, very high<br />
concentrations may kill the plant. Yields were reduced about 25 to 70% when rice was<br />
irrigated continuously with water containing 600 to 1300 parts per million (ppm ) o f<br />
salt, respectively (Adair <strong>and</strong> Engler, 1955). In addition, the accumulation o f salt over<br />
the years may deflocculate the soil so that stickiness, compactness, <strong>and</strong> impermeability<br />
o f the soil increase, making the soil hard to cultivate. <strong>Rice</strong> soils become less productive<br />
as salt accumulation increases.<br />
Salt injury will be greater if the salt water is applied to dry soils rather than soils<br />
that have been previously watered with fresh water (Adair <strong>and</strong> Engler, 1955). This is<br />
due to increased salt concentrations in the dry soil <strong>and</strong> more movement into the root<br />
zone, where it is taken up readily by tire rice plants. <strong>Rice</strong> grown on clay soils may not<br />
be injured by salt water to the same extent as on lighter soils.<br />
In Arkansas, soils that have been irrigated for many years with water from shallow<br />
wells containing high levels of calcium <strong>and</strong> magnesium have shifted in pH value from<br />
acidic to alkaline. This increase in pH decreased the availability o f phosphorus in<br />
the soil.<br />
Values com monly used in evaluating rice irrigation water quality include calcium,<br />
bicarbonate, <strong>and</strong> chloride concentrations, sodium absorption ratio (SAR), <strong>and</strong><br />
electrical conductivity (EC). Table 3.2.1 gives a general guideline for irrigation water
Production<br />
T A B LE 3 .2 .U<br />
<strong>Rice</strong> Ir r ig a t io n W a t e r Q u a lity G u id e<br />
Water Quality Variables Level of Concern“ Concern<br />
Calcium (Ca)<br />
Bicarbonate (HCOs)<br />
> 60 ppm (> 3 mEq/L)<br />
> 305 ppm (> 5 mEq/L)<br />
Together can cause soil pH increases near<br />
water inlet <strong>and</strong> in-flow areas, causing<br />
zinc deficiency in silt loam soils<br />
Electrical conductivity, EC<br />
(after lime deposition)<br />
> 770 ppm Causes high soil salinity that can damage<br />
<strong>and</strong> lull rice seedlings<br />
Chloride > 100 ppm (> 3 mEq) Contributes to the measured electrical<br />
conductivity level; High Cl alone may<br />
pose a problem for soybeans in rotation<br />
Sodium absorption ratio,<br />
SAR^<br />
> 10 Causes sodic soil that has poor physical<br />
condition<br />
Source: <strong>Rice</strong> Production H <strong>and</strong>book. University of Arkansas Cooperative Extension Service Publication MP 192,1996.<br />
“Lower levels can cause damage in some cases.<br />
^SAR= sodium -r [(square root of calcium + magnesium) -r 2], where sodium (Na), calcium (Ca), <strong>and</strong> magnesium (Mg)<br />
are expressed in inijliequivalents. ><br />
quality. A water supply should be tested every 5 years unless problems arise with the<br />
crop that is thought to be associated with water quality or when a significant change<br />
in the pumping rate or depth occurs.<br />
Water Temperature<br />
The temperature o f rice water is very important. Bhattacharyya <strong>and</strong> De Datta (1971)<br />
found that water temperatures between 20 <strong>and</strong> 30°C (68 <strong>and</strong> 86*^F) were optimum for<br />
rice growth <strong>and</strong> development. Water temperatures that are either too high or too low<br />
can be injurious to the rice crop. High temperatures decrease rice yields, decrease tire<br />
uptake o f silicon <strong>and</strong> potassium, reduce tiller number, <strong>and</strong> increase the percentage<br />
of unfilled spikelets (De Datta, 1981). Low temperatures (15°C/65°F) delayed panicle<br />
initiation, decreased panicle size, increased sterility, extended the tim e required for<br />
complete heading, <strong>and</strong> adversely affected nutrient uptake.<br />
Water supplied from deep wells may have temperatures o f 15°C (65®F) or less.<br />
Cold-water injury usually occurs in locations where underground water is pumped<br />
either directly into the upper bay of the rice field or around the gate areas where water<br />
flows into the field from flume ditches,<br />
Growers can reduce cold-water injury by a number of methods. Irrigation water<br />
from deep wells can be pumped directly into shallow basins that allow the cold water<br />
to warm before it is relifted into the rice field. Pumping water at night can also reduce<br />
the injury caused by cold water because it allows the sun to warm the water during<br />
the day. To allow better distribution o f cold water entering rice bays, installation of<br />
large overflows, greater than or equal to 4.5 m (15 ft or m ore), in the levees o f the<br />
upper first three bays where the water is pumped can be effective. Installation of large<br />
overflows probably is best used in com bination with night pumping. If only large<br />
overflows are used, the size of the cold water area will increase; however, total damage<br />
to the rice by cold water will be less because cold water is spread over a larger area
<strong>Rice</strong> Production 279<br />
than if the cold water is confined primarily to one or two bays. Side inlet irrigation,<br />
where water is pumped through poly pipe laid across one side o f the field, also works<br />
well for some growers. The pipe in each bay should have enough holes to h<strong>and</strong>le the<br />
volume o f water pumped from the well <strong>and</strong> to facilitate water flow into each bay. If<br />
possible, water should be added at night to further reduce the effect o f cold water.<br />
Wafer Volume<br />
Water volume requirement varies depending on soil texture, num ber <strong>and</strong> length o f<br />
irrigation ditches, soil moisture before flooding, perimeter levee <strong>and</strong> irrigation ditch<br />
seepage, transpiration by plants, <strong>and</strong> evaporation. A water supply is considered adequate<br />
for any given field if the field can be flushed in 2 to 4 days, flooded in 3 to 5 days,<br />
<strong>and</strong> the flood can be maintained for the entire season (Tacker et al„ 2000). Generally,<br />
the rule o f thumb for pumping rates is a m inim um o f 24 L/min per hectare (15<br />
gal/min per acre). In cases where more than one irrigation ditch is required or when<br />
the irrigation ditch is extremely long, 28 to 31 L/min per hectare (18 to 20 gal/min<br />
per acre) is advisable. Once a flood is established, 13 to 16 L/min per hectare (8 to 10<br />
gal/min per acre) is usually satisfactory for m aintaining the flood. As a more detailed<br />
guideline. Table 3.2.2 shows recommended pumping rates according to different soil<br />
textural groups.<br />
Pumping hours required vary from situation to situation due to pump flow<br />
capacity, as well as losses that may occur because o f soil type, field configuration, crop<br />
<strong>and</strong> weather dem<strong>and</strong>, or other factors that may affect the flow o f water in the field. Soil<br />
type has a significant impact on pumping capacity needs, due to the water-holding<br />
ability o f various soils type. For example, a pumping capacity o f 3785 L/min (1000<br />
gal/min) is sufficient to irrigate a 40-ha (100 acres) silt loam field with a hardpan, but<br />
if the field is a clay or silty clay soil, the same pumping capacity can irrigate only a<br />
27-ha (67 acres) field.<br />
The best m ethod o f determining pump discharge capacity is by using an inline<br />
flowmeter. Proper installation is very im portant to assure accurate reading <strong>and</strong> good<br />
service from the flowmeter. I f more than one pumping plant is to be monitored, a<br />
portable flowmeter can be used. To docum ent irrigation water requirement, most<br />
flowmeters can be equipped with a totalizing dial that records the total quantity o f<br />
water pumped. If a flowmeter is not available, the discharge can be estimated by<br />
various other methods.<br />
TABLE 3.2.2.<br />
Recommended Pumping Rates for Different Soil Textural Groups<br />
Pum ping Rate<br />
[L/m)n pe r hectare (gal/m in per ocre)]<br />
Soli Texturai G roup M inim um D esired<br />
Silt loam with pan 93 (10) 93 (15)<br />
S<strong>and</strong>y loam 140 (15) 232 (25)<br />
Silt loam without pan 93 (10) 140 (15)<br />
Clay <strong>and</strong> silty clay 140 (15) 186 (20)<br />
Source; <strong>Rice</strong> Production Plondbook. University of Arkansas Cooperative Extension Service Publication MP<br />
192,1996.
280 Produtfjon<br />
Water Conservation<br />
Water conservation in rice <strong>production</strong> is im portant, because m ost areas where water<br />
is pumped from wells have experienced declining water tables. Well depth varies from<br />
several 100 m in some areas to less than 30 m in other areas. Remedies include the use<br />
o f deeper wells [275 to 300 m (900 to 1000 ft)], the use o f reservoirs to supplement<br />
well water (Gerlow <strong>and</strong> Mullins, 1958), use o f underground pipelines to transport<br />
irrigation water, <strong>and</strong> water conservation measures. Following are both short- <strong>and</strong><br />
long-term tactics for water use conservation.<br />
Short-Term Tactics<br />
• Keep accurate water-use records (flush times, flood times, <strong>and</strong> replacement<br />
pumping times) on fields for future reference.<br />
• Determine the flow rate o f wells by measurenient, meter, or some other method.<br />
Use a flow rate meter on at least one well on each farm.<br />
• Plane fields to help eliminate high <strong>and</strong> low spots,<br />
•; W hen possible, divide fields that are 32 ha (80 acres) or larger into smaller fields<br />
' by cross leveling to make general management <strong>and</strong> water use'easier.<br />
• Fields, regardless o f size, should be accessible on aU sides by three- or four-<br />
wheeler trucks to make flood management easier. This may require additional<br />
construction o f farm turn rows or extrawide outside levees.<br />
• Use a stale seedbed, if possible, thereby drilling into m oist soil to get a st<strong>and</strong><br />
with little or no flushing.<br />
• Construct outside levees as soon as possible so that they will settle, thereby<br />
reducing seepage,<br />
• Construct permanent outside levees where possible.<br />
" Pack all levees well during construction.<br />
• Use metal or plastic gates in levees for better flood depth control,<br />
• Use more than one gate per levee.<br />
• Determine how long it takes to flush a field.<br />
• Determine approximate pumping time to establish a permanent flood.<br />
• Know how many hours are necessary to pump each day to m aintain a permanent<br />
flood.<br />
• To replace water, run engines at maxim um speed for short intervals. This will<br />
allow efficiency <strong>and</strong> reduce water cost.<br />
• Use surface water when possible.<br />
• Mark flood levels in each bay while rice is small so that the flood level is easier<br />
to identify <strong>and</strong> maintain when the rice is larger.<br />
• Aerial applicators should notify the grower if any water loss is observed.<br />
• Turn wells off or do not pump when rain is expected.<br />
• Check fields daily for water loss.<br />
• M aintain a shallow flood, especially on semidwarf varieties.<br />
• M aximum permanent flood time should be no more than 93 days.<br />
• Turn the well off several days before draining for harvest.<br />
Long-Term Toctlis<br />
• Have flow meters on every well.<br />
• Precision-level the fields to get uniform grades for straight levees.
<strong>Rice</strong> Producfion 281<br />
Construct perm anent roads around fields to act as outside levees.<br />
Develop long-term water-management plans for each farm.<br />
Encourage cooperation witli l<strong>and</strong>lords on water conservation matters.<br />
Improve water delivery systems, such as underground pipe or tailwater recovery<br />
systems.<br />
P U N T IN G METHODS<br />
Establishment o f a uniform st<strong>and</strong> o f rice is critical for successful rice <strong>production</strong>.<br />
Uneven emergence o f rice affects a num ber o f <strong>production</strong> practices, including proper<br />
application <strong>and</strong> timing o f herbicides, nitrogen, fungicides, <strong>and</strong> insecticides. It also can<br />
affect harvest tim ing <strong>and</strong> heat unit (degree day 50) management predictions.<br />
<strong>Rice</strong> produced in the United States is grown in either water- or dry-seeded cultural<br />
systems. There are three water-seeded systems. D ry seeding is the predom inant<br />
system employed in Arkansas, Texas, Mississippi, Missouri, <strong>and</strong> Florida (Helms <strong>and</strong><br />
Slaton, 1996; Klosterboer <strong>and</strong> Turner, 1999; Linscombe et al., 1999; Miller <strong>and</strong> Street,<br />
1999). California rice hectarage is cultured almost exclusively by water seededing. In<br />
Louisiana, water seeding is the predominant system, but dry seeding also contributes<br />
significantly to total <strong>production</strong>, especially in the northeastern region.<br />
Wafer-Seeded <strong>Rice</strong><br />
There are three basic water-seeding systems: (1) continuous flooding, (2) pinpoint<br />
flooding, <strong>and</strong> (3) delayed flooding. Water seeding is preferred over dry seeding in<br />
certain rice-producing regions, due to factors such as earliness in planting, red rice<br />
suppression, rapid st<strong>and</strong> establishment, <strong>and</strong> tradition (Griffin et al., 1986; Diin<strong>and</strong>,<br />
1988). In southwestern Louisiana, water seeding is the m ost extensive planting method<br />
used because significant rice hectarage is severely infested with red rice. Control or<br />
suppression o f red rice is highly dependent on the water-seeding system used. The<br />
effects o f water management on rice st<strong>and</strong> density <strong>and</strong> grain yields are shown in<br />
Figures 3.2.6 <strong>and</strong> 3.2.7, respectively.<br />
Continuous Pinpoint Deiayed<br />
Figure 3.2.6. Effect of water management on the st<strong>and</strong> density of red <strong>and</strong> domestic rice.<br />
(Adapted from Sonnier, 1975.)
282 Production<br />
■ i<br />
a i :<br />
Continuous Pinpoint Delayed<br />
Figure 3.2,7. Effect of woter monogement on groin yield of red <strong>and</strong> domestic rice. (Adopted<br />
from Sonnier, 1975.)<br />
Continuous flooding is the prim ary cultural system used in California. Continuous<br />
flooding is also employed on limited hectarage in other rice growing areas. This<br />
system provides excellent weed control, especially when coupled with herbicides (Hill<br />
et al., 1992). Design o f m ost irrigation systems with continuous flooding in California<br />
includes floodwater recirculation to minimize pesticide movement to public waterways.<br />
The permanent flood is established after fertilizer incorporation, final seedbed<br />
preparation, <strong>and</strong> application o f preplant pesticides. Pregerminated rice seeds are aerially<br />
seeded into the flood, <strong>and</strong> the developing seedling grows through a st<strong>and</strong>ing flood<br />
of 7 to 13 cm (3 to 5 in.).<br />
Pinpoint flooding is the m ost popular water seeding practice in Louisiana, especially<br />
in the southwestern area. In this system, fields are flooded, seeds are sown<br />
aerially, <strong>and</strong> then the fields are drained within 1 to 3 days. The floodwater is removed<br />
for a very brief period o f time, generally 3 to 5 days, <strong>and</strong> a shallow, perm anent flood<br />
is then established (Linscorabe et al., 1999). The brief drainage period in this system<br />
encourages better seedling anchorage than typically occurs with continuous flooding.<br />
A disadvantage with continuous flooding can be poor root anchorage, which occurs<br />
with varieties that possess poor seedling vigor. Flood removal allows for aeration that<br />
stimulates root growth. It is critical with pinpoint flooding that the seedbed remain<br />
saturated during the b rief drainage period, to m aintain preplant fertilizer nitrogen in<br />
a stable <strong>and</strong> available form <strong>and</strong> to suppress the germination o f red rice.<br />
In the water-seeded delayed-flooding system, the basic difference in water management<br />
from continuous <strong>and</strong> pinpoint flooding is the extended drainage period after<br />
seeding (Linscombe at al., 1999), The perm anent flood is not established until 15 to<br />
20 days after emergence. Adequate moisture for seedling growth <strong>and</strong> establishment is<br />
maintained by rainfall or flush irrigation. Fertilizer management <strong>and</strong> weed control are<br />
very similar to that prescribed below for dry seeding. This system is not recommended<br />
where red rice is a yield-limiting factor.
<strong>Rice</strong> Production 283<br />
Dry-Seeded <strong>Rice</strong><br />
Dry-seeded rice is either drilled in narrow rows or broadcast. In drilled systems (Figure<br />
3.2.8), row spacing typically ranges from 15 to 25 cm (6 to 10 in.), <strong>and</strong> rice<br />
is seeded to a depth o f 2.5 cm (1 in.) or less. M odern semidwarf rice cultivars are<br />
characterized by having shortened mesocotyls, resulting in slow emergence if soils are<br />
crusted or if rice is planted too deep. In recent years, gibberellic acid seed treatments,<br />
which results in longer mesocotyls, have been utilized to facilitate emergence <strong>and</strong><br />
st<strong>and</strong> establishment (Dmi<strong>and</strong>, 1993).<br />
For dry-seeded rice, the objective should be to prepare a shallow, firm, weed-free<br />
seedbed tliat is free o f clods. The seedbed should be well pulverized <strong>and</strong> firm to m aintain<br />
proper moisture for drilling, which ensures rapid germination <strong>and</strong> emergence o f<br />
the rice plant. Depending on the rotation crop planted prior to the rice crop, it may<br />
be beneficial to till the l<strong>and</strong> in the fall or early spring. Early preparation is especially<br />
critical when high-residue crops such as grain sorghum or corn are the previous crops<br />
(Klosterboer <strong>and</strong> Turner, 1999). I f decomposition o f crop residues is not complete<br />
at the time o f planting, microorganisms that decompose crop residue wiU compete<br />
with rice plants for nutrients, particularly nitrogen, resulting in nitrogen deficiency<br />
in the rice plant. If rice follows rice, the field should be disked or rolled in the fall or<br />
early spring to speed decomposition o f crop residue. <strong>Rice</strong> following soybeans does not<br />
usually require as m uch l<strong>and</strong> preparation, since die seedbed is norm ally left in fairly<br />
good condition.<br />
Although there was little difference between the yield of rice when fields were<br />
tilled in the fall or early spring, test results from Texas suggested that tüUng l<strong>and</strong> in<br />
the fall did allow better distribution o f labor during the season (Reynolds, 1954).<br />
In addition, l<strong>and</strong> tilled in the faU formed better tilth <strong>and</strong> was easier to prepare for<br />
seeding by disking <strong>and</strong> harrowing the following spring than l<strong>and</strong> tilled in the spring.<br />
Regardless o f when the soil is tilled, Reynolds (1954) found that soil tilled 13 to 20 cm<br />
(5 to 8 in.) deep produced somewhat larger rice yields than soil tilled only 5 cm (2 in.)<br />
deep. If l<strong>and</strong> is deep tilled in the spring, it should be disked <strong>and</strong> harrowed as soon as<br />
possible. This breaks up any large soil clods, prevents baking <strong>and</strong> crusting o f the soil<br />
/<br />
Figure 3,2.8.<br />
Grain drill used for planting dry-seeded drill rice.
284 Production<br />
surface, <strong>and</strong> avoids subsequent difficulty in preparation o f the seedbed (Johnston <strong>and</strong><br />
Miller, 1973). W here large clods exist, a drag pipe or a sm ooth or corrugated roller is<br />
used to firm tire seedbed to prevent deep placement o f the seed. The num ber o f times a<br />
field is cultivated before planting should be minimized, since' overcultivation adds cost<br />
without realization o f a corresponding yield increase (Klosterboer <strong>and</strong> Turner, 1999).<br />
There are times when the field has been prepared the previous fall or the field s<br />
condition is fairly smooth following the previous crop <strong>and</strong> further tillage is not necessary<br />
prior to plaiiting (stale seedbed planting), Under stale seedbed plantings, 2,4-D<br />
should be applied in winter for broadleaf weed control. A burndown herbicide, applied<br />
at a rate sufficient to eliminate all live vegetation, can then be used before<br />
planting or within 3 to 4 days after planting. The only difference in cultural practices<br />
using this approach is that early seedbed cultivation is eliminated.<br />
WATER MANAGEMENT<br />
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<strong>Rice</strong> grown in the. United States is cultured in a lowl<strong>and</strong> system, <strong>and</strong> flood management<br />
varies depending on planting method. In drUl-seeded culture, if rice is not<br />
planted to moisture, a flush irrigation is required to initiate germination <strong>and</strong> emergence.<br />
Additional flush irrigation is necessary in the absence o f rainfall to provide the<br />
necessary moisture for st<strong>and</strong> establishment <strong>and</strong> early-season growth. A shallow, permanent<br />
flood is established approximately 21 to 28 days after emergence, coinciding<br />
with the three- to four-leaf plant growth stage.<br />
In water-seeded culture, rice fields are flooded to a depth o f 5 to 10 cm (2 to 4<br />
in.) soon after seedbed preparation is completed. In continuous flooding systems, the<br />
initial flood is maintained throughout the season. W ith pinpoint flooding, the initial<br />
flood is removed from the field 1 to 3 days after seeding, <strong>and</strong> the permanent flood<br />
is established 3 to 5 days later. Flood management in a water-seeded delayed-flood<br />
system is similar to that of dry seeding. After seeding, the field is drained during the<br />
same tim e frame as that followed with pinpoint flooding. The permanent flood Is<br />
not established until 15 to 20 days after emergence, <strong>and</strong> flush irrigation is required<br />
during the extended drain in the absence of rainfall. In all o f these cultural systems,<br />
flood depth is increased gradually throughout the season to a depth o f 15 to 20 cm (6,<br />
to 8 in.) as rice plants increase in height.<br />
The permanent flood In all these systems usually is established by the four-leaf<br />
growth stage. In some instances, there are in-season management practices that require<br />
either complete removal or lowering o f the permanent flood. These practices<br />
may include fertilizer applications for nutrient disorders, soil aeration for physiological<br />
disorders, <strong>and</strong> pesticide applications for weeds <strong>and</strong> insects.<br />
Application of foliar-applied zinc materials may be necessary to correct zinc<br />
deficiency. Depending on the severity o f the deficiency <strong>and</strong> size o f the plants, complete<br />
removal or significant floodwater drawdown is necessary. All other nutrients used in<br />
rice can be applied into an existing flood once an adequate root system is established.<br />
Straighthead <strong>and</strong> hydrogen sulfide injury are disorders that require field draining<br />
during vegetative growth. Straighthead is a physiological disorder that occurs on<br />
s<strong>and</strong>y soils, soils where significant amounts o f organic residue have been incorporated<br />
prior to planting, <strong>and</strong> soils where arsenical herbicides have been used for weed control<br />
in other crops. Field draining for control o f straighthead is a preventive practice, since<br />
S i
J<br />
<strong>Rice</strong> Production 285<br />
no visual symptoms are exhibited prior to the irreversible damage that occurs. The<br />
flood is removed for a period o f 10 to 14 days or until the soil is completely dry<br />
<strong>and</strong> cracked. Complete aeration o f the soil must occur prior to panicle initiation<br />
to minimize potential straighthead damage. Hydrogen sulfide injury occurs when<br />
high sulfide levels accumulate under anaerobic conditions. This accumulation occurs<br />
when undecomposed plant residues are incorporated into the soil prior to planting.<br />
Field draining for hydrogen sulfide injury <strong>and</strong> injury from other toxic gases usually<br />
occurs once initial injury symptoms are recognized. Flood removal for 7 to 14 days<br />
<strong>and</strong> complete aeration o f the soil minimize potential yield loss.<br />
Some postemergence herbicides such as propanil <strong>and</strong> bentazon are applied with<br />
the floodwater removed, but typically the soil is still saturated. Other herbicides, such<br />
as 2,4-D , can be applied simply by lowering the floodwater to a shallow depth. This<br />
exposes the weeds <strong>and</strong> improves herbicide coverage.<br />
In lieu o f insecticide use, field drainage at the early- to mid-tillering growth stage<br />
is a cultural control m ethod for helping manage the rice water weevil. Complete<br />
floodwater removal <strong>and</strong> soil aeration to the point o f cracking is necessary to reduce<br />
root pruning by the rice water weevil larvae.<br />
Depending on soil type, fields are drained in preparation for harvest 2 to 3 weeks<br />
prior to the expected harvest date. Addition o f water is usually discontinued 7 to 10<br />
days prior to draining to allow loss o f a portion o f the floodwater through evaporation,<br />
percolation, or seepage. S<strong>and</strong>y-textured <strong>and</strong> silt loam soils usually dry within 2 weeks<br />
o f drainage, <strong>and</strong> clay soils require up to 3 weeks. Panicle m aturity also is used as an<br />
indicator for drainage. On soils that tend to dry quickly, such as s<strong>and</strong>y soils, floodwater<br />
is released when the top two-thirds to three-fourths o f the panicle has become yellow<br />
<strong>and</strong> turned downward. O n slow-drying clay soils, floodwater is released when the top<br />
one-half o f the panicle is yellow <strong>and</strong> turned down.<br />
Ratoon <strong>production</strong> is very com mon in southwestern Louisiana, Texas, <strong>and</strong> Florida.<br />
Water management in these systems generally consists o f shallow flooding within<br />
5 to 7 days o f main crop harvest, <strong>and</strong> this first flood is maintained until harvest<br />
drainage. It is very uncom m on for ratoon fields to be drained after the initial flood<br />
during the growing season.<br />
There has been considerable interest in recent years in closed irrigation systems<br />
for rice. The reasons are numerous, <strong>and</strong> include water conservation, reducing pesticide<br />
losses to receiving waters, <strong>and</strong> economics. California has taken the lead in implem<br />
entation o f these systems, due to the strict environmental guidelines placed on its<br />
agriculture, Water savings can be significant in these systems, since m ost o f the water<br />
has to be retained in holding basins or recirculated for additional use throughout<br />
the season. These systems are expensive to develop <strong>and</strong> to maintain. Presently, the<br />
use o f closed systems in the other rice-producing states is limited but growing in<br />
popularity.<br />
To reduce water use <strong>and</strong> increase grower flexibility, there have been attempts<br />
to culture rice with either sprinkler or furrow irrigation (Figure 3.2.9). Sprinkler<br />
irrigation research has demonstrated significant savings in water use when compared<br />
with flood irrigation, but this savings has been at the expense o f weed <strong>and</strong> disease<br />
control (Akkari et al., 1986; Westcott <strong>and</strong> Vines, 1986; McCauley, 1990). Furrow<br />
irrigation experiments have resulted in similar findings (Bollich et al., 1990). A few<br />
growers have utilized furrow irrigation with some success; however, weed control<br />
continues to be a problem with the herbicides currently available.
286 Production<br />
Figure 3.2,9.<br />
Irrigating furrow irrigated rice with poly pipe.<br />
TILLAGE PRACTICES<br />
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W<br />
Conventional tillage is the most com m on tillage m ethod used in U.S. rice <strong>production</strong>.<br />
In both water- <strong>and</strong> dry-seeded systems, intensive seedbed preparation has always<br />
been promoted as the first critical step toward successful rice <strong>production</strong>. Specific<br />
equipment used to accomplish this objective typically depends on soil type, environmental<br />
conditions, <strong>and</strong> locale. Disking, field cultivation, vibra-shanking, leveling,<br />
mulching, <strong>and</strong> seedbed firming are field operations that might be included in seedbed<br />
preparation. The desired result is to have a seedbed that is free o f weeds; uniform<br />
<strong>and</strong> level, to facilitate flooding <strong>and</strong> draining; <strong>and</strong> in a physical condition that promotes<br />
rapid emergence <strong>and</strong> plant growth. In drill-seeded systems, a well-prepared,<br />
smooth, <strong>and</strong> relatively clod-free surface is desired. In dry broadcast- <strong>and</strong> water-seeded<br />
systems, rougher seedbed surfaces are necessary to minimize seed movement <strong>and</strong><br />
seedling drift.<br />
In southwestern Louisiana, reductions in grain yield <strong>and</strong> quality due to red rice<br />
infestations have resulted in the development o f a tillage practice specific for red rice<br />
control. The practice is referred to as muddingin, a system in which m ost o f the tillage<br />
is performed under flooded conditions. These puddling operations destroy emerged<br />
red rice before planting, <strong>and</strong> various field implements are used to level <strong>and</strong> smooth<br />
the seedbed.<br />
Conservation tillage is a recent innovation in rice tillage in the United States<br />
(Figure 3.2.10). This protects the environment by eliminating unnecessary tillage that<br />
results in both soil erosion <strong>and</strong> degradation o f water quality in receiving streams.<br />
Reduced tillage also has offered opportunities to lower <strong>production</strong> costs <strong>and</strong> improve<br />
timeliness in planting. The introduction of improved no-till grain drills has greatly<br />
enhanced the capability to produce rice with reduced tillage.<br />
Approaches to reduced tillage include no-tillage <strong>and</strong> stale seedbeds. W ith notillage><br />
rice is planted directly into previous crop residue. Soybeans <strong>and</strong> wheat are
<strong>Rice</strong> Production 287<br />
Figure 3.2.10.<br />
Drill seeding in o reduced tilloge system.<br />
examples o f crops that have been grown in rotation with rice where no-tillage has been<br />
successful. In stale-seedbed systems, tillage operations are performed in the fall, <strong>and</strong> the<br />
seedbeds remain idle while winter vegetation becomes established. Stale seedbeds also<br />
can be established in the early spring.<br />
Reduced tillage <strong>production</strong> has been adapted to both water- <strong>and</strong> dry-seeded<br />
cultural systems. As with conventional tillage <strong>and</strong> water seeding, reduced tillage <strong>and</strong><br />
water seeding is primarily a system utilized where red rice, is a yield constraint. Non-<br />
selective herbicides are used to control winter vegetation prior to planting if fields<br />
remain drained over the winter months. If rice fields are flooded over the winter to<br />
control red rice <strong>and</strong> other problem weeds, or to encourage waterfowl habitat, the need<br />
for nonselective herbicides for preplant vegetation control in the water-seeded system<br />
may be reduced or eliminated. <strong>Rice</strong> is seeded directly into the winter floods. With<br />
dry-seeded culture, fields may also be flooded over the winter, <strong>and</strong> the need for weed<br />
control with herbicides varies. Flooded fields are drained in the early spring, <strong>and</strong> weed<br />
establishment is usually minimal.<br />
In recent years, the fall application o f phosphorus, potassium, <strong>and</strong> sulfur has<br />
become a popular fertility practice, especially in the stale-seedbed system. These nutrients<br />
are incorporated during the final phases o f seedbed preparation in the fall <strong>and</strong><br />
have resulted in better management of nitrogen fertilizer in the rice crop. This practice<br />
is not recommended if spring tillage operations result in significant movement o f<br />
topsoil, especially with l<strong>and</strong>-leveling operations that redistribute soil in which fertilizer<br />
has been incorporated. This results in uneven distribution o f fertilizer nutrients,<br />
which can cause nutrient deficiencies in some areas o f the field <strong>and</strong> excess nutrients in<br />
other areas. Fall application o f fertilizers should be avoided on soils that test very low<br />
in m ajor nutrients or those with cation-exchange capacities o f less than 5 milliequivalents<br />
per 100 grams.<br />
M" !<br />
PLANTING DATES<br />
<strong>Rice</strong> should not be planted until the average air <strong>and</strong>/or soil temperature reaches<br />
(60°F). <strong>Rice</strong> planted when air <strong>and</strong> soil temperatures are cool may not emerge as rapidly
288 Produtfion<br />
TA B LE 3.2.3.<br />
In flu e n c e of T e m p e ra tu re o n th e N u m b e r o f D a y s R e q u ire d fo r<br />
^ 1 1<br />
'l l ■'<br />
In itia tio n a n d F in a l G e rm in a tio n a n d G e rm in a tio n P e rc e n ta g e o f 21 R ice V a rie tie s<br />
Temperature<br />
r c m i<br />
H um ber of D ays<br />
for Initial G erm ination<br />
( % G erm ination)<br />
N um ber of D ays<br />
for Final G erm ination<br />
( % Germ ination)<br />
10 (50) 13 (4) 23 (70)<br />
13 (55) 7 (2) 14 (84)<br />
16 (61) 5 (6) 12 (90)<br />
19 (66) 4 (13) 11 (93)<br />
22 (72) 3 (11) 8 (92)<br />
'■pi|i:i'"-. '<br />
t I f ■i<br />
Source: <strong>Rice</strong> Production H <strong>and</strong>book. University of Arkansas Cooperative Extension Service Publication<br />
MP 192,1996.<br />
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i K :<br />
IjMIfl<br />
['ll<br />
as rice planted under ideal conditions. Table 3.2.3 shows the relations between temperature<br />
<strong>and</strong> speed <strong>and</strong> percent germination for 21 rice varieties grown in Arkansas,<br />
Under cool conditions [10°C (50°F)] the num ber o f days to final germination was<br />
23 days vs. 12 days when temperatures were 16°C (61°F). Percent germination also<br />
increased from 70% to 90% at 10 <strong>and</strong> 16°C, respectively. As temperatures increased<br />
to 22°C (72°F), rate of germination increased further. W hen rice is planted during cool<br />
temperatures, more time is required for emergence <strong>and</strong> development to the four- to<br />
five-leaf growth stage.<br />
In southern Louisiana <strong>and</strong> Texas, planting usually starts in early March. <strong>Rice</strong><br />
planting takes place between April 10 <strong>and</strong> June 20 in northern rice-growing regions;<br />
however, planting dates vary with cultivar <strong>and</strong> location.<br />
SEEDING RATES<br />
Establishment of an adequate plant population is critical for successful rice <strong>production</strong>.<br />
There is general agreement among the U.S. rice-producing states that the desired<br />
st<strong>and</strong> density should range from 107 to 215 plants/m^ (10 to 20 plants/ft^), regardless<br />
o f the planting method. <strong>Rice</strong> can be produced successfully from st<strong>and</strong> densities below<br />
100 plants/m^ (10 plants/ft^) with intensive agronomic management. There are<br />
no benefits with st<strong>and</strong> densities higher than 215 plants/m^ (20 plants/ft^) in most<br />
situations.<br />
<strong>Rice</strong> cultivars currently grown in the United States vary up to 25% in seed size,<br />
<strong>and</strong> this factor is considered when determining the desired seeding rate. In drill-<br />
seeded rice, seeding rates range from 78 to 112 kg/ha (70 to 100 Ib/acre). Seeding<br />
rates are typically higher with dry broadcasting <strong>and</strong> water seeding since there is less<br />
precision in seed placement. Dry broadcast rates range from 100 to 134 kg/ha (90 to<br />
120 Ib/acre), <strong>and</strong> water-seeding rates range from 134 to 168 kg/ha (120 to 150 Ib/acre).<br />
These recommended ranges address ideal to less desirable seedbeds. The higher rates<br />
are recommended when seed quality is a concern, when seedbed preparation is poor,<br />
in areas where seed depredation from blackbirds <strong>and</strong> waterfowl occurs, <strong>and</strong> when cool<br />
temperatures occur witli early seed ing.'
is??-<br />
<strong>Rice</strong> Production 289<br />
CULTIVAR SELECTION<br />
Choosing a rice cultivar to grow involves consideration o f many factors, including<br />
length o f growing season, grain type (long, medium, or short), availability o f red<br />
rice-free seed, disease susceptibility, processing characteristics, yield potential, <strong>and</strong><br />
market dem<strong>and</strong> (price). W hen a new cultivar is selected, it should be grown initially<br />
on a limited hectarage to allow a closer observation o f the new cultivar <strong>and</strong> determine<br />
how it fits into the overall farming operation.<br />
Grain Type<br />
In 1998, the United States produced 85258 m t (188 million pounds) o f rice (Table<br />
3.2.4). Seventy-five percent o f the rice produced was long grain, 24% was medium<br />
grain, <strong>and</strong> 1% was short grain. Arkansas, Louisiana, Mississippi, Texas, <strong>and</strong> M issouri<br />
produce most o f the long-grain rice. California produces the bulk o f the U.S. medium-<br />
grain rice. Arkansas, Louisiana, <strong>and</strong> to a lesser extent Texas also produce medium-<br />
grain rice, adjusting hectarage among types based on market conditions. Production<br />
o f short-grain rice is concentrated almost exclusively in California, with Arkansas producing<br />
only 4% o f the U.S. total in 1998. Since the 1950s, <strong>production</strong> o f short-grain<br />
rice has declined, due to loss o f the Japanese market. In addition, Puerto Rico recently<br />
has been substituting lower-priced southern medium-grain rice for California shortgrain<br />
rice.<br />
CROP ROTATIONS AND DOUBLE-CROPPING<br />
Red rice infestations have a significant influence on rice rotation systems in Louisiana.<br />
Very little rice m onoculture is practiced, because o f red rice. In soutliwestern Louisi-<br />
. ana, rice is usually grown in a 1;1 rotation with soybeans. This rotation allows the<br />
farmer to take advantage o f additional herbicides to control red rice. Another rotational<br />
system with rice <strong>and</strong> soybeans includes crawfish culture. In this 1:1; 1 rotation<br />
scheme, crawfish follows rice in a double-cropping system, <strong>and</strong> soybeans are grown in<br />
the second year. After rice harvest, stubble fields are usually flooded by early October.<br />
T A B L E 3.2.4. U.S. R íce P ro d u c tio n (1 0 0 ,0 0 0 p o u n d s ) b y Sto te , 2 0 0 1<br />
State Long Grain IVIedium Grain Short Grain Total<br />
Arkansas 91632 9 620 60 101312<br />
California 1001 35 939 1550 38490<br />
Louisiana 29 560 424 — 30 014<br />
Mississippi 16445 — —<br />
16445<br />
Missouri 12 257 60 — 12 317<br />
Texas 14405 62 — 14467<br />
Total 165330 46105 1610 213 045<br />
Source; U.S. Department of Agriculture, Crop Production 2001 Summary (Washington, DC: U.S. Department<br />
of Agriculture, National Ag Statistics Service, Jan. 2002).
290 Production<br />
•ivM<br />
H I ; '<br />
These fields may be flushed prior to flooding to m aintain adequate soil moisture for<br />
stubble regrowth in the absence o f rain. This forage source is extremely important<br />
in initiating the eventual detrhal system upon which crawfish development is dependent.<br />
Crawfish harvest proceeds through the late winter <strong>and</strong> spring months, <strong>and</strong> once<br />
pond <strong>production</strong> begins to decline, the fields are drained <strong>and</strong> prepared for soybean<br />
<strong>production</strong>. There is more flexibility with rotational crops in more northern ricegrowing<br />
regions, with corn, grain sorghum, cotton, <strong>and</strong> wheat being alternatives. In<br />
the upper Mississippi river valley, the m ost com m on rotation system is 1 year o f rice<br />
followed by 2 years o f soybeans.<br />
California rotation systems are unique in that crops grown in rotation with rice<br />
include safflower, dry beans, sugarbeets, vegetable seed crops, <strong>and</strong> tomatoes (Hill<br />
et a l, 1992), crops not grown in rotation with rice in other rice-producing states.<br />
Approximately 70% o f California’s rice is grown in a rice-rice or rice-fallow rotation.<br />
In Florida, rice is rotated with sugarcane or vegetables.<br />
RATOON PRODUCTION<br />
Ratoon cropping, or second cropping, is an im portant <strong>production</strong> practice in southwestern<br />
Louisiana <strong>and</strong> Texas. <strong>Rice</strong> regrows from the main crop stubble to produce<br />
a second crop. The climatic conditions o f these areas provide a favorable environment<br />
for successful <strong>production</strong> in m ost years. It is im portant for producers to take<br />
advantage o f early planting <strong>and</strong> early-maturing cultivars to increase the likelihood of<br />
ratoon crop success. M ain crop management practices affect ratoon <strong>production</strong>, <strong>and</strong><br />
significant disease or weed infestations in tlie main crop will adversely affect ratoon<br />
crop potential. Ratoon cropping should be avoided if fields are heavily rutted from<br />
wet harvest conditions in the main crop. Ratoon cropping also is discouraged if the<br />
main crop was infested with red rice, since this encourages additional buildup o f red<br />
rice seed reserves in the soil.<br />
Ratoon crop yield potential is quite variable, ranging from 20 to 40% o f the main<br />
crop, As stated previously, ratoon crop yields can be affected adversely by weeds <strong>and</strong><br />
disease infestations in the main crop. Modest ratoon crop yields can be realized with<br />
minimal inputs, but intensive management generally results in much higher yield<br />
potential.<br />
Nitrogen application to the ratoon crop increases grain yield significantly. The<br />
amount applied depends on the earllness o f the ratoon <strong>and</strong> the health o f the main<br />
crop stubble. In Louisiana, if the potential for ratoon <strong>production</strong> appears to be high,<br />
nitrogen rates as high as 84 kg/ha (75 Ib/acre) are applied. W ith later main crop<br />
harvest, the nitrogen rate is reduced to 50 kg/ha (45 Ib/acre). Recommended nitrogen<br />
rates for Texas ratoon <strong>production</strong> with high potential are 78 kg/ha (70 Ib/acre) for<br />
conventional cultivars <strong>and</strong> 112 kg/ha (100 Ib/acre) for semidwarf cultivars, August 15<br />
is the general cutoff date for ratoon crop initiation in each o f these states.<br />
Water management has been evaluated for its effects on ratoon <strong>production</strong>. The<br />
time o f ratoon flood establishment has a significant effect on ratoon grain yields.<br />
Research in Louisiana <strong>and</strong> Texas has shown that the highest yields are obtained when<br />
the m ain crop is fertilized with nitrogen <strong>and</strong> flooded immediately after harvest. Delays<br />
in flood establishment o f 10 days or more result in ratoon yield reductions. The effect<br />
o f delayed flood establishment on selected rice cultivars is shown in Figure 3.2,11.
<strong>Rice</strong> Production 291<br />
Cypress Bengal Jodon Kaybonnet<br />
Figure 3.2,11 Effect of flood establishment timing on ratoon crop grain yields. (Adapted<br />
from B o ilichetoU 995,1996,1997.)<br />
Cypress Kaybonnet Bengal Jodon Drew<br />
Figure 3.2.12. Effect of stubbie management on ratoon crop grain yields. (Adapted from<br />
Bollichetcl., 1996, 1997.)<br />
Studies have also been conducted in Louisiana to evaluate stubble management<br />
<strong>and</strong> its effects on ratoon <strong>production</strong>. Clipping m ain crop stubble to a shorter height<br />
after harvest, or rolling the main crop stubble flat, generally improves ratoon regrowth<br />
by increasing ratoon tiller <strong>production</strong> <strong>and</strong> encouraging faster regrowth. But in m ost<br />
situations, the positive effects on ratoon yields are few, <strong>and</strong> yield reductions have<br />
occurred. The current recomm endation is to harvest the main crop at a cutting height<br />
that results in maxim um harvest efficiency. The effects o f reduced cutting height <strong>and</strong><br />
rolling on selected rice cultivars are shown in Figure 3.2.12.<br />
HARVEST OPERATION<br />
Cutting rice at the proper stage o f m aturity is essential for obtaining high milling<br />
quality, which comm<strong>and</strong>s a premium price, <strong>and</strong> maximizing yields. The moisture<br />
content o f harvested rice generally is between 18 <strong>and</strong> 21% . At this growth stage, the<br />
kernels on the lower portion o f the head are in the hard dough stage. I f rice is harvested<br />
at an immature stage, when the moisture level is too high, lighter, chalky kernels will<br />
be present, thus reducing head (whole kernel) rice <strong>and</strong> total milled rice. Harvesting<br />
É
292 Production<br />
.Íl|]L<br />
É'<br />
11 1:<br />
l|i'<br />
i<br />
rice at low moisture levels causes shattering <strong>and</strong> more broken kernels, resulting in a<br />
reduction in milling quality.<br />
Because loss o f moisture in st<strong>and</strong>ing rice can occur, very quickly, harvesting<br />
should begin <strong>and</strong> proceed rapidly when the grain moisture content is approximately<br />
21% . Tim ing harvest for 21% moisture also allows m ore efficient harvesting o f upright<br />
plants, reduces shattering <strong>and</strong> mechanical breakage, <strong>and</strong> helps to ensure that<br />
harvesting is completed before the grain moisture content drops below a desirable<br />
level. If rice is allowed to field-dry to moistures less than 16%, the driest kernels are<br />
subject to wetting <strong>and</strong> drying cycles caused by air-drying changes from day to night.<br />
Rapid rewetting by rain once rice reaches 15% or less moisture content is a key cause<br />
o f lower head rice yields.<br />
Combine capacity should be anticipated such that harvest is complete by the<br />
time rice reaches 16% moisture. Hectarage o f cultivars with the same m aturity range<br />
should not exceed harvest capacity. Com bine capacity can be extended by planting<br />
cultivars with different maturities or by spreading the planting dates o f similarmaturity<br />
cultivars over a longer period o f time than is planned to com bine the rice.<br />
■ W hen sampling for moisture content, use a com bine to harvest a small, representative<br />
sample from a small area in the field. H<strong>and</strong>-harvested samples do not give an<br />
accurate indication o f rice moisture content, since the moisture content o f rice_.grain<br />
on a plant <strong>and</strong> even on a single panicle will vary. Average grain moisture is determined<br />
when a sample is taken.<br />
A st<strong>and</strong>ard-make combine will harvest rice, but a rice com bine, which is equipped<br />
with special options, can produce a more efficient harvest (Figure 3,2.13), Specially<br />
designed rice combines can be operated under muddy conditions <strong>and</strong> can be adjusted<br />
to do a thorough threshing job with a minim um o f shelling <strong>and</strong> cracking o f the grain.<br />
M ost combines are equipped with a straw spreader or chopper. The chopper cuts the<br />
rice straw as it leaves the com bine, spreading the straw particles uniformly over the<br />
stubble to facilitate tillage <strong>and</strong> residue decomposition (Johnston <strong>and</strong> Miller, 1973).<br />
The Shellbourne Reynolds stripper-header has added a new concept to the development<br />
of improved rice harvesting equipment (Figure 3.2.14). This header has flexible<br />
fingers that detach kernels by flailing through st<strong>and</strong>ing rice. In initial observation,<br />
the stripper-header performed very efficiently, reduced the amount o f plant material<br />
Figure 3.2.13.<br />
Haryesting rice with a conventional header.
<strong>Rice</strong> ProducHon 293<br />
Figure 3.2.14.<br />
Harvester equipped with a stripperhead.<br />
passing through the rice combines, increased speed o f harvest, harvested lodged rice,<br />
<strong>and</strong> produced a cleaner rice sample.<br />
In Louisiana, the use o f stripper-headers has not been very popular with ratoon<br />
cropping. Despite the obvious harvesting benefits o f a stripper-header in the main<br />
crop, there has been a tendency to produce lower ratoon yields. Yield reductions have<br />
been associated with smaller panicles, lower grain-filling percentage, <strong>and</strong> lodging o f<br />
the ratoon crop.<br />
Special cutter bars also are made that aid in harvesting lodged rice <strong>and</strong> may be<br />
installed on com bine headers if needed. W hen harvesting lodged rice with a pickup<br />
reel, the combine should be operated in the same general direction as the rice has<br />
lodged.<br />
Combine adjustment that allows satisfactory removal o f foreign matter with<br />
stems <strong>and</strong> otlier waste without blowing rice from the combine is important. Because<br />
there are many different types o f threshing mechanisms in present-day combines, it<br />
is very im portant to consult the operator's manual or dealer representative to assist<br />
in adjusting the com bine properly. Combines may have to be adjusted a couple o f<br />
times a day while harvesting, to compensate for crop moisture <strong>and</strong> environmental<br />
conditions.<br />
Drying <strong>Rice</strong><br />
The temperature <strong>and</strong> moisture content o f freshly harvested rice determines the allowable<br />
time lapse before the rice begins to spoil. Som e cooling must begin within 12 to<br />
24 hours (preferably within 12 hours) after harvesting. The time lapse between freshly<br />
harvested rice <strong>and</strong> cooling becomes more critical when the moisture content o f the<br />
rice is higher <strong>and</strong> die outside temperature is warmer.<br />
The main problem in storing rice is excess grain moisture. Although rice can be<br />
safely harvested when its moisture content is between 18 <strong>and</strong> 21% , grain cannot be<br />
stored safely at this moisture level. If harvesting is delayed to perm it all grain to field<br />
dry completely, weather conditions may cause considerable quality <strong>and</strong> yield loss.
294 Production<br />
Figure 3.2.15.<br />
Farm storage bins.<br />
I I<br />
i i<br />
O n-farm drying is the m ost widely used method o f conditioning wet grain to<br />
preserve its quality <strong>and</strong> nutritive value for food <strong>and</strong> feed, <strong>and</strong> to preserve seed germ<br />
ination (Figure 3.2.15). The advantages of on-farm drying <strong>and</strong> storage include an<br />
earlier harvest that reduces the chance o f weatlier-related losses <strong>and</strong> increased yields<br />
due to less grain shattering <strong>and</strong> breakage. O n-farm drying allows harvest to be timely.<br />
This maintains grain quality <strong>and</strong> quantity, <strong>and</strong> harvest can take place at a grower'sconvenience<br />
<strong>and</strong> speed. Spoilage is also reduced because grain is stored in better<br />
facilities, <strong>and</strong> stored rice permits versatile market management o f the crop.<br />
REFERENCES<br />
mr-‘<br />
Adair, C. R., <strong>and</strong> K. Engler. 1955. The Irrigation <strong>and</strong> culture o f rice. In Water. USDA<br />
Yearbook o f Agriculture. U.S. Department o f Agriculture, Washington, DC, pp.<br />
389-394.<br />
Aklcari, K. H,, R. E, Talbert, J. A. Ferguson, J. T. GUmour, <strong>and</strong> K. Khodayari. 1986.<br />
Herbicides <strong>and</strong> seeding rate effects on sprinlder-irrigated rice. Agron. J, 78:927"<br />
929.<br />
Bhattacharyya, A. K., <strong>and</strong> S. K. DeDatta. 1971. Effects o f soil temperature regimes on<br />
growth characteristics, nutrition <strong>and</strong> grain yield o f IR22 rice. Agron. J. 63:443-<br />
449. (<br />
Bolhch, P. K., W. J. Leonards, <strong>and</strong> D, M. Walker. 1990. Nitrogen management in<br />
furrow-irrigatedLemont rice. Annu. Res. Rep. 82. <strong>Rice</strong> Research Station, Louisiana<br />
Agricultural Experiment Station, Louisiana State University Agricultural Center,<br />
Baton Rouge, LA, pp. 157-162.<br />
BoUich, P. K., D. E. Groth, G. A. Meche, R, P. Regan, G. R. Romero, <strong>and</strong> D. M.<br />
Walker*. 1995. Cultural Management Studies. Annu. Res. Rep. 87. <strong>Rice</strong> Research<br />
Station, Louisiana Agricultural Experiment Station, Louisiana State University<br />
Agricultural Center, Baton Rouge, LA, pp. 204-217.<br />
Bollich, P. K., D. Jordan, D. E. Groth, G. A. Meche, R. P. Regan, G. R. Romero, <strong>and</strong><br />
D. M. Walker. 1996. Cultural Management Studies. Annu. Res. Rep. 88. <strong>Rice</strong> Research<br />
Station, Louisiana Agricultural Experiment Station, Louisiana State University<br />
Agricultural Center, Baton Rouge, LA, pp. 221-236.
Ríce Production 295<br />
Bollich, P . K.) R. P. Regaiij G. R. Romero, <strong>and</strong> D. M. Walker. 1997. Cultural m anagement<br />
studies. Annu. Res. Rep. 89. Ríce Research Station, Louisiana Agricultural<br />
Experim ent Station, Louisiana State University Agricultural Center, Baton<br />
Rouge, LA, pp. 185-208.<br />
Cooke, E T., Jr., D. E Caillavet, <strong>and</strong> J. C. Walker, Jr. 1996. <strong>Rice</strong> Water Use <strong>and</strong> Costs in<br />
the Missisippi Delta. Miss. Agrie. For. Exp. Stn. Bull. 1039, 8 pp.<br />
De Datta, S. K. 1981. Water use <strong>and</strong> water management practices for rice. In Principles<br />
<strong>and</strong> Practices of <strong>Rice</strong> Production. Wiley, New York, Chap. 9.<br />
Dun<strong>and</strong>, R. T. 1993. Gihberellic Add Seed Treatment in <strong>Rice</strong>. Agrie. Exp. Stn. Bull. 842.<br />
Louisiana State University Agricultural Center, Baton Rouge, LA, 19 pp,<br />
Dun<strong>and</strong>, R. T. 1988. Red rice— ^its im pact on grain quality <strong>and</strong> its cultural control:<br />
a review o f research in Louisiana, 1960-1982. La. Agrie. Exp. Stn. Bull. 792.<br />
Louisiana State University Agricultural Center, Baton Rouge, LA, 18 pp.<br />
Ellis, G. 1982. USD A National <strong>Rice</strong> Culture Workshop Proceedings, Little Rock, AR,<br />
Oct. 4 -8 .<br />
Faulkner, M . D. 1965. Leveling rice l<strong>and</strong> in water. Trans. Am. Soc. Agrie. Eng. 8 (4 ):5 1 7 -<br />
519.<br />
Gerlow, A., <strong>and</strong> T. Mullins. 1958. Reservoirs for Irrigation in the Gr<strong>and</strong> Prairie Area:<br />
An Economical Appraisal Ark. Agrie. Exp. Stn. Bull. 606.<br />
Griffin, J. L., J. B. Baker, R. T. Dun<strong>and</strong>, <strong>and</strong> E. A. Sonnier. 1986. Red <strong>Rice</strong> Control in<br />
<strong>Rice</strong> <strong>and</strong> Soybeans in Southwest Louisiana. La. State Univ. Agrie. Exp. Stn. Bull.<br />
776.<br />
Helms, R. S., <strong>and</strong>N . Slaton. 1996. <strong>Rice</strong> st<strong>and</strong> establishment. In <strong>Rice</strong> <strong>production</strong> h<strong>and</strong>book,<br />
Coop. Ext. Serv. Publ. M P 192. University o f Arkansas, Little Rock, AIC,<br />
pp. 17-20.<br />
Hill, J. E,, S. R. Roberts, D. M . Br<strong>and</strong>on, S. C. Scardaci, J. E W illiams, C. M . W ick,<br />
W. M . Canevari, <strong>and</strong> B. L. Weir, 1992. <strong>Rice</strong> Production in California. Coop. Ext.<br />
Univ. Calif. Div. Agrie. Nat. Res. Publ. 21498.<br />
Johnston, T, H., <strong>and</strong> M . D. Miller. 1973. Culture. In <strong>Rice</strong> in the United States: Varieties<br />
<strong>and</strong> Production. USDA-ARS H<strong>and</strong>book 289. U.S. Department o f Agriculture,<br />
Washington, D C, pp. 88-134.<br />
Kapp, L. C. 1947. The Effect of Common Salt on <strong>Rice</strong> Production. Ark. Agrie. Exp. Stn.<br />
Bull. 465.<br />
Klosterboer, A. D., <strong>and</strong> F. T. Turner. 1999. Seeding methods. In 1999 <strong>Rice</strong> Production<br />
Guidelines, Tex. Agrie. Ext. Serv. Publ. D -1253. Texas A&M University, College<br />
Station, T X , p. 8.<br />
Linscombe, S. D., J. K. Saichuk, K. P. Seilhan, P. IC. Bollich, <strong>and</strong> E. R. Funderburg.<br />
1999. General agronomic guidelines. In Louisiana <strong>Rice</strong> Production H<strong>and</strong>book.<br />
LSU Agrie. Ctr. Publ. 2321, pp. 5-12.<br />
M artin, J. H., W. H. Leonard, <strong>and</strong> D. L. Stamp. 1976. <strong>Rice</strong>. In Prindples of Field Crop<br />
Production. Macmillan, New York, pp. 539-562.<br />
McCauley, G. N. 1990. Sprinkler vs. flood irrigation in traditional rice <strong>production</strong><br />
regions in southeast Texas. Agron. J. 82:677-683.<br />
Mikkelson, D. S., <strong>and</strong> N. S. Evatt. 1973. Soils <strong>and</strong> fertilizers. In Rke in the United<br />
States: Varieties <strong>and</strong> Production. USDA-ARS H<strong>and</strong>book 289. U.S. Departm ent o f<br />
Agriculture, Washington, DC, pp. 76-87.<br />
Miller, T. C., <strong>and</strong> J. E. Street. 1999. Mississippi <strong>Rice</strong> Growers Guide, Mississippi State<br />
University Cooperative Extension Service, Mississippi State, MS.
296 Production<br />
Reynolds, E. B. 1954, Research on <strong>Rice</strong> Production in Texas, Texas Agri. E x p t Stn. Bul<br />
775.<br />
Setia, P., N. Childs, E. Wailes, <strong>and</strong> J. Livezey. 1994. The U.S. <strong>Rice</strong> Industry. USDA-ERS<br />
Agricultural Econom ics Report 700. U.S. Department of Agriculture, Washington,<br />
DC, p. 162.<br />
Sonnier, E. A. 1975. Red <strong>Rice</strong> Studies. Annu. Prog. Rep. 67. <strong>Rice</strong> Research Experiment<br />
Station, Louisiana Agricultural Experiment Station, pp. 93-99.<br />
Tacker, R, J. Langston, ). Ferguson, <strong>and</strong> E. Vories. 2000, Water management. In <strong>Rice</strong><br />
Production Pl<strong>and</strong>book. Cooperative Extension Service, University o f Arkasas,<br />
Little Rock, AR.<br />
USDA, 1999. <strong>Rice</strong>: Situation <strong>and</strong> Outlook Yearbook. Econom ic Research Service, U.S.<br />
Departm ent o f Agriculture, Washington, DC.<br />
Westcott, M. P., <strong>and</strong> K. W. Vines. 1986. A com parison o f sprinkler <strong>and</strong> flood irrigation<br />
for rice. Agron, J. 78:637-640.<br />
SUGGESTED READING<br />
<strong>Smith</strong>, W. D., J. J. Defies, <strong>and</strong> C. H. Bennett. 1938. Effect of Date of Harvest on Yield<br />
<strong>and</strong> Milling Quality of <strong>Rice</strong>. USDA Circular 484. U.S. Department o f Agriculture,<br />
Washington, DC.<br />
I<br />
|1 . '
C tio pfe r<br />
3.3<br />
Ríce Soils: Physical <strong>and</strong> Chemical<br />
Characteristics <strong>and</strong> Behavior<br />
H. D o n Scott a n d D a v id M . M ilie r<br />
Deportment of Crop, Soil, <strong>and</strong> Environmental Sciences<br />
University of Arkansas<br />
Fayetteville, Arkansas<br />
F a b ric e G. R e n a u d<br />
Cranfield Centre for EcoChemIstry<br />
Cranfield University<br />
Silsoe, Bedford, Engl<strong>and</strong><br />
INTRODUCTION<br />
MORPHOLOGICAL CHARAQERISTICS OF RICE SOILS<br />
Selected Soil Profile Descriptions<br />
Designotion of Morphological Features in <strong>Rice</strong> Soils<br />
PHYSICAL AND CHEMICAL PROPERTIES OF RICE SOIL PROFILES<br />
Physical Properties<br />
Color<br />
Texture <strong>and</strong> Structure<br />
Water Balance <strong>and</strong> Water Use<br />
Hydraulic Conductivity <strong>and</strong> Drainage<br />
Aeration<br />
Temperature <strong>and</strong> Thermal Characteristics<br />
Chemical Properties<br />
Oxidation-Reduction Status<br />
pH<br />
Electrical Conductivity<br />
Chemical Composition of the Soil Solution<br />
SEASONAL BEHAVIOR OF PHYSICAL AND CHEMICAL PROPERTIES IN RICE FIELDS<br />
Physical Properties<br />
Hydraulic Properties<br />
Water Infiltration <strong>and</strong> Redistribution<br />
Soil Thermal Regime<br />
Chemical Properties<br />
Oxidation-Reduction Status<br />
pH<br />
<strong>Rice</strong>: Origin, History, Technology, <strong>and</strong> Production, edited by C. Wayne <strong>Smith</strong><br />
ISBN 0-471-34516-4 © <strong>2003</strong> John Wiley 8c Sons, Inc.<br />
297
298 Production<br />
Electrical Conductivity<br />
Chemical Composition of the Soil Solution<br />
CONCLUDING REMARKS<br />
REFERENCES<br />
INTRODUCTION<br />
!<br />
Production o f rice in the United States requires optim um climatic <strong>and</strong> soil conditions.<br />
<strong>Rice</strong> is grown in areas having high rates o f solar radiation, warm air temperatures,<br />
a long growing season, <strong>and</strong> an extensive supply o f water for irrigation. Soil profiles<br />
in the rice areas have physical <strong>and</strong> chemical characteristics that support the plant,<br />
encourage exploration <strong>and</strong> development o f roots, <strong>and</strong> supply the required amounts<br />
of water, oxygen, <strong>and</strong> nutrients to the plant. Soil characteristics that result in optimal<br />
growth <strong>and</strong> development of rice typically include profile features such as a level to<br />
gently sloping topography, a deep profile, physical <strong>and</strong> chemical characteristics that<br />
restrict the redistribution <strong>and</strong> drainage o f water from the root zone, <strong>and</strong> moderately<br />
acid to moderately alkaline soil pH.<br />
Locations in the United States having the optimal com binations o f weather <strong>and</strong><br />
soil characteristics along with a plentiful supply o f water typically are found in the alluvial<br />
valleys o f the Mississippi River in the south-central states o f Arkansas, Louisiana,<br />
Mississippi, <strong>and</strong> Missouri, along the Gulf coastal prairies o f Louisiana <strong>and</strong> Texas, <strong>and</strong><br />
in the Sacramento <strong>and</strong> San Joaquin valleys o f north-central California. These areas<br />
correspond to m ajor l<strong>and</strong> resource areas (MLRAs) 131 <strong>and</strong> 134,150A, <strong>and</strong> 17, respectively,<br />
A MLRA is a geographically associated area that has a com m on pattern of soils,<br />
climate, water resources, <strong>and</strong> l<strong>and</strong> uses. Boundaries between MLRAs are natural <strong>and</strong><br />
not political. The soils in the MLRAs were formed either from an alluvial process or<br />
a com bination o f alluvial <strong>and</strong> aeolian processes, <strong>and</strong> tend to have level or nearly level<br />
topography, a poorly or somewhat poorly drained soil profile, <strong>and</strong> either a thermic<br />
or hyperthermic temperature regime. In this chapter we discuss the soil physical <strong>and</strong><br />
chemical properties <strong>and</strong> their behavior in soils during rice <strong>production</strong>.<br />
MORPHOLOGICAL CHARACTERISTICS OF RICE SOILS<br />
Selected Soil Profile Descriptions<br />
Soil morphology can be used to characterize the solid <strong>and</strong> pore phases qualitatively<br />
<strong>and</strong> provide inform ation on the status o f water, nutrient, <strong>and</strong> gas flow rates through<br />
the profile <strong>and</strong> on the soil physicochemical characteristics. Soils planted to rice tend<br />
to have physically <strong>and</strong> chemically heterogeneous profiles <strong>and</strong> occur in four orders:<br />
Alfisols, Vertisols, MoUisols, <strong>and</strong> Inceptisols (Flach <strong>and</strong> Slusher, 1978). The central<br />
concept morphologies o f three example soil profiles in the MLRAs where rice is grown<br />
in the United States are presented in Tables 3.3.1 to 3.3.3. Descriptions o f these example<br />
soils are presented so that the reader can gain a greater underst<strong>and</strong>ing <strong>and</strong><br />
appreciation o f physical <strong>and</strong> chemical characteristics of soil profiles typically used for<br />
rice <strong>production</strong>.
J<br />
Ríce Soils: Physical <strong>and</strong> Chemical Characterislics <strong>and</strong> Behavior 299<br />
TA B LE 3.3.1.<br />
S u m m a ry o f th e O ffic ia l D e sc rip tio n o f S h a rk e y S o ils in A r k a n s a s a n d M is s is s ip p i'’<br />
Soil series: Sharkey<br />
Taxonomic dass: very-fine, smectitic, thermic Chromic Epiaquerts<br />
Typical pedon: Sharkey clay, planed <strong>and</strong> smoothed, cultivated field<br />
Depth<br />
Interval<br />
Horizon (cm) Description<br />
Apl 0-15 Very dark grayish-brown (lOYR 3/2) clay; structureless, massive; firm;<br />
very sticky; very plastic; few fine roots; few fine pores; few stress<br />
cracks; common fine distinct dark yellowish-brown (lOYR 4/4)<br />
masses of iron accumulation around dead roots; few fine faint dark<br />
gray (10 YR 4/1) iron depletions around some root channels <strong>and</strong><br />
pores; slightly acid; clear smooth boundary<br />
Ap2 15-25 Dark grayish-brown (lOYR 4/2) clay; weak medium subangular<br />
blocliy structure parting to moderate fine angular blocky; firm; very<br />
sticky; very plastic; few fine roots; few fine pores; shiny pressure<br />
faces on some peds; many medium distinct dark yeUowish-brown<br />
(lOYR 4/4) masses of iron accumulation throughout matrix <strong>and</strong><br />
few fine prominent strong brown (7.5 YR 5/6) masses of iron<br />
accumulation on faces of some peds; few fine faint dark gray (lOYR<br />
■4/1) iron depletions throughout matrix; few fine charcoal<br />
fragments; slightly acid; clear wavy boundary<br />
Bssgl 25-61 Dark gray (lOYR 4/1) clay (color for ped interiors <strong>and</strong> faces); weak<br />
medium subangular blocky structure parting to moderate fine<br />
angular blocky; very firm/very sticky/very plastic; few fine roots;<br />
few fine-grooved intersecting slickensides that from coarse<br />
wedge-shaped aggregates; shiny pressure faces on some peds;<br />
common medium distinct dark yellowish-brown aggregates, shiny<br />
pressure faces on some peds; common medium distinct dark<br />
yellowish-brown (lOYR 4/4) masses of iron accumulation in matrix<br />
<strong>and</strong> on faces of peds; few fine prominent strong brown (7.5 YR 5/6)<br />
masses of iron accumulation of faces of some peds; neutral; gradual<br />
wavy boundary<br />
Bssg2 61-99 Dark gray (lOYR 4/1) clay (color for ped interiors <strong>and</strong> faces); weak<br />
medium subangtilar blocicy structure parting to moderate fine<br />
angular blocky; very firm; very sticky; very plastic; few fine roots;<br />
common intersecting slickensides that form coarse wedge-shaped<br />
aggregates; shiny pressure faces on some peds; many medium<br />
distinct dark yellowish-brown (lOYR 4/4), few fine distinct dark<br />
yellowish-brown (lOYR 3/4), <strong>and</strong> few fine prominent strong brown<br />
(7.5 YR 5/6) masses of iron accumulation in matrix <strong>and</strong> on faces of<br />
peds; slightly alkaline; gradual wavy boundary.<br />
Source: Adapted fro m th e O fficial S oil Series D escrip tion o f U SD A -N R C S O SD In fo rm atio n Sheet<br />
{www. nrcs. iastate. edu/soils/ods) .<br />
"These descriptions are for a 1-m ro o t zone.
300 Production<br />
TABLE 3.3.2. S u m m a ry o f th e O fficia l D e sc rip tio n o f C ro w le y S o ils in A c a d ia P a rish , L o u isia n a ”<br />
Soil series: Crowley<br />
Taxonomic class: fine, smectitic, hyperthermic Typic Albaqualfs ■<br />
Typical pedon: Crowley silt loam on a broad, nearly level area in cropl<strong>and</strong> at an elevation of<br />
about 9.75 m<br />
Depth<br />
Interval<br />
Horizon (cm) Description<br />
][¥='’■, i?’ -I<br />
■lifeMl-'-’<br />
Ap 0-18 Dark grayish-brown (lOYR 4/2) silt loam; weak fine granular<br />
structure; friable; many very fine <strong>and</strong> fine <strong>and</strong> few coarse roots; few<br />
fine rounded black <strong>and</strong> brownish iron-manganese concretions;<br />
common fine yellowish-brown (lOYR 5/6) <strong>and</strong> yellowish-red (5 YR<br />
5/6) oxidation stains around root channels; moderately acid; clear<br />
wavy boundary. (7.5 to 33 cm thick).<br />
Eg 18 -36 Light brownish-gray (lOYR 6/2) silt loam; weak fine subangular<br />
' biocky structure; friable; many very fine <strong>and</strong> fine roots; few very<br />
fine <strong>and</strong> fine tubular pores; few fine <strong>and</strong> medium rounded black<br />
<strong>and</strong> brownish iron-manganese concretions; common fine dark<br />
brown (7.5 YR 4/4) oxidation stains around root channels;<br />
moderately acid; abrupt wavy boundary, (10 to 38 cm thick),<br />
Btgl 36-64 Grayish-brown (lOYR 5/2) silty clay; moderate medium subangular<br />
biocky structure; firm; common very fine <strong>and</strong> fine roots; common<br />
very fine <strong>and</strong> fine tubular pores; many distinct clay films on surfaces<br />
of peds; few fine rounded black <strong>and</strong> brownish iron-manganese<br />
concretions; manly medium prominent red (2.5 R 4/6) masses of<br />
iron accumulation; many dark gray (10 YR 4/1) ped coatings;<br />
moderately acid; clear wavy boundary.<br />
Btg2 64-84 Grayish-brown (2.5 YR 5/2) silty clay; moderate coarse prismatic<br />
structure parting to moderate medium subangular biocky firm;<br />
common very fine <strong>and</strong> fine roots; many very fine tubular pores;<br />
many distinct clay films on surfaces of peds; many fine <strong>and</strong> medium<br />
prominent red (2.5 YR 4/6) <strong>and</strong> common medium prominent<br />
strong brown 97.5 YR 5/8) masses of iron accumulation; many dark<br />
gray (lOYR 4/1) ped coatings; common dark gray (lOYR 4/1) silt<br />
loam krotovina about 1.3 cm wide; moderately acid, clear wavy<br />
boundary.<br />
Btg3 84-102 Light brownish-gray (2.5 Y 6/2) silty clay loam; weak coarse prismatic<br />
structure parting to moderate medium subangular biocky; firm;<br />
common very fine roots; common very fine <strong>and</strong> fine tubular pores;<br />
many distinct clay films on surfaces of peds; many fine, medium.<br />
Coarse round black <strong>and</strong> brownish iron-manganese concretions;<br />
many medium prominent yellowish-brown (lOYR 5/6) <strong>and</strong><br />
common fine prominent yellowish-red (5 YR 4/6) masses of iron<br />
accumulation; neutral; gradual wavy boundary.<br />
Source: Adapted from the Official Soil Series Description of USDA-NRCS OSD Information Sheet<br />
{www. nrcs. iastate.edu/soih/osd).<br />
"These descriptions were for a l-m root zone.
<strong>Rice</strong> Soils; Physical <strong>and</strong> Chemical Charoderislics <strong>and</strong> Behavior 301<br />
T A B L E 3.3.3. S u m m a iy o f th e O ffic ia l D e sc rip tio n o f W illo w s S o ils in Y o lo C ounty, C a lif o r n ia ‘S<br />
Soil series; Willows<br />
Taxonomic class: fine, smectitic, thermic Sodic Endoaquerts<br />
Typical pedon: Willows clay on a east-facing slope of less than 1% in a rice field at an<br />
elevation of 6.7 m<br />
hr“'<br />
Depth<br />
Interval<br />
Horizon (cm) Description<br />
Ap 0-10 Gray (5 Y/1) clay, very dark gray (5 Y 3/1), moist; many fine<br />
prominent strong brown (7.5 YR 5/6), mottles, yellowish brown (10<br />
YR 5/6) moist; granular structure; extremely hard, very firm, sticky<br />
<strong>and</strong> very plastic; common very fine roots; many fine pores; neutral<br />
(pH 7.0); abrupt smooth boundary (5 to 25 cm thick).<br />
A 10-33 Gray (5 Y 5/1) clay, very dark gray (5Y 3/1), moist; many fine<br />
prominent strong brown (7.5 YR 5/6) motdes, yellowish brown<br />
(lOYR 5/6) moist; strong, very coarse prismatic structure; extremely<br />
hard, very firm, sticlcy <strong>and</strong> very plastic; many fine roots; few very<br />
fine pores; many prominent intersecting slickensides; slightly<br />
aUcaline (pH 7.5); clear smooth boundary ( 7 to 25 cm thick).<br />
Bsskl 33-71 Olive gray (5Y 4/2) clay, very dark gray (5Y 3/1), moist; strong very<br />
coarse prismatic structure; very hard, very firm, sticky <strong>and</strong> very<br />
plastic; common fine roots; many very fine pores; many prominent<br />
intersecting slickensides; slightly effervescent with segregated lime<br />
in soft masses; strongly alkaline (pH 8.8); diffuse boundary (25 to<br />
50 cm tliick).<br />
Bssk2 71-97 Olive gray (5Y 4/2) clay, very dark gray (5Y 3/1), moist; strong very<br />
coarse prismatic structure; very hard, very firm, sticky <strong>and</strong> very<br />
plastic; few fine roots; many very fine <strong>and</strong> few fine pores; many<br />
prominent intersecting slickensides; slightly effervescent with<br />
segregated lime; strongly allcaline (pH 9.0); dear smooth boundary<br />
(20 to 50 cm tliick).<br />
Bssk3 97-122 Olive gray (5Y 5/2) day, very dark gray (5Y 4/2), moist; strong coarse<br />
prismatic structure; very hard, very firm, sticky <strong>and</strong> very plastic; few<br />
fine roots; many very fine pores; many prominent intersecting<br />
slickensides; strongly effervescent with disseminated lime; strongly<br />
alkaline (pH 8.8); diffuse wavy boundary (10 to 33 cm thick).<br />
Source; Adapted from the Oflfidal Soil Series Description o f USDA-NRCS OSD Information Sheet<br />
(w w w. nrcs. iastate.edu/soils/osd).<br />
“These descriptions were for a 1-m root zone.<br />
The Sharkey series consists o f very deep, poorly to very poorly drained, very<br />
slowly permeable soils that formed in clayey alluvium (Table 3.3.1). The morphology,<br />
drainage, <strong>and</strong> hydrology o f Sharkey <strong>and</strong> similar soils in the Mississippi river valley has<br />
changed due to anthropogenic activities (USDA-N RCS, 2000). These soils occur on<br />
floodplains, lower parts o f natural levees, in backswamps <strong>and</strong> ab<strong>and</strong>oned channels,<br />
<strong>and</strong> on interfluves <strong>and</strong> low terraces o f the Mississippi River. They formed in clayey
302 Production<br />
w ■<br />
îiif<br />
alluvium that is dominantly smectitic. Elevation ranges from 6 to 76 m above mean<br />
sea level. Mean annual air temperatures range from 15 to 19“C, <strong>and</strong> the m ean annual<br />
precipitation ranges from 114 to 165 cm. The slope is predominantly less than 1%<br />
but can be as high as 5%. Surface runoff is negligible to very slight, depending on<br />
slope <strong>and</strong> water content at the soil surface. Sharkey soils are extensive (1.62 million<br />
hectares) in the Mississippi River floodplains <strong>and</strong> low terraces in Arkansas, Louisiana,<br />
Kentucky, Mississippi, Missouri, <strong>and</strong> Tennessee in MLRA 131.<br />
The Crowley series consists of very deep, somewhat poorly drained, very slowly<br />
permeable soils (Table 3.3.2). These soils occur on broad, nearly level coastal prairies<br />
<strong>and</strong> were form ed in clayey sediments on fluviatile terraces of Pleistocene age (USDA-<br />
NRCS, 2000), Slopes are dominantly less than 1% but range to 3% . R unoff is high<br />
on soils having 0 to 1% slopes <strong>and</strong> very high on soils having 1 to 3% slopes. Mean<br />
annual precipitation is 140 to 163 cm, <strong>and</strong> mean annual temperature is 19 to 2 rC .<br />
The soUs frequently are saturated above the clayey subsoil at a depth o f 15 to 45 cm<br />
during the winter <strong>and</strong> spring m onths in m ost years. Crowley soils are extensive in the<br />
coastal prairies of southwestern Louisiana <strong>and</strong> southeastern Texas in MLRA 150 A.<br />
Soils with many similar characteristics are also found in MLRA 134;<br />
The Willows series consists of very deep, poorly to very poorly drained sodic soils<br />
formed in alluvium from mixed rock sources (Table 3.3.3). Willows soils occur in<br />
nearly level basins on tlie western side o f the Sacramento <strong>and</strong> San Joaquin valleys<br />
<strong>and</strong> interm ountain valleys o f the Coast Range in California. Elevations are 6 m to<br />
as much as 515 m above sea level (USDA-NRCS, 2000). They have slopes ranging<br />
from 0 to 2% . The mean annual precipitation is about 38 cm, <strong>and</strong> the mean annual<br />
temperature is about 15°C. Willows soils have slow runoff <strong>and</strong> very slow permeability,<br />
with intermittent water tables at depths o f 60 to 152 cm (USDA-N RCS, 2000). Unless<br />
protected, this soil receives runoff from other areas. Willows soils are moderately<br />
extensive in MLRA 17.<br />
Designation of Morphologicol Features in <strong>Rice</strong> Soils<br />
i<br />
<strong>Rice</strong> soils typically have morphological features that indicate restricted movement of<br />
water, nutrients, <strong>and</strong> gas in the profile <strong>and</strong> poor soil aeration. Surface features such<br />
as roughness, clod form ation, dispersion, <strong>and</strong> surface sealing are transient features.<br />
Their physical properties can be altered drastically through tillage <strong>and</strong> water management<br />
<strong>and</strong> consequently are not included in soil taxonomy. Solid-phase features<br />
in the subsofi, such as clay <strong>and</strong> sodium (Na) accumulations, may be included in the<br />
description, along with profile features such as pans, including tillage pan, fi:agipan,<br />
duripan, <strong>and</strong> calcic pan; iron-m anganese concretions, mottling; <strong>and</strong> clay films.<br />
In soil profile descriptions, lowercase letters are used to designate specific characteristics<br />
of subsurface horizons (USDA-SCS, 1993). As shown m the profile descriptions<br />
in Tables 3.3.1 to 3.3.3, rice soils can have m ore than one o f these morphological<br />
characteristics in the same horizon. Morphological features o f rice soil profiles may<br />
include one or more of the following characteristics (SSSA, 1996):<br />
1. ArgiUic, t. The symbol “t” is used to indicate an accumulation o f clay fro<br />
horizons above. It is a mineral soil horizon tliat is characterized by the alluvial<br />
accumulation o f phyllosilicate clays. The argillic horizon has a certain minimum
<strong>Rice</strong> Soils; Physical gnd Chemical Charqiteristics cmd Behavior 303<br />
thickness, depending on the thickness o f the solum; a m inim um quantity o f clay in<br />
comparison with an overlying eluvial horizon, depending on the clay content o f the<br />
eluvial horizon; <strong>and</strong> usually has coatings of oriented clay on the surface o f pores or<br />
peds or bridging s<strong>and</strong> grains. A high clay content in the profile restricts the vertical<br />
movement o f water.<br />
2. NatriCi n. The symbol "n” is used for a mineral soil horizon that satisfies the<br />
requirements o f an argillic horizon, but that also has prismatic, columnar, or blocky<br />
structure <strong>and</strong> a subhorizon having greater than 15% saturation with exchangeable<br />
Na+. The presence o f sodium indicates the possibility o f clay dispersion, which results<br />
in a decrease in the hydraulic conductivity <strong>and</strong> an alkaline pH.<br />
3. Tillage pan, p. The symbol “p” is used to indicate a disturbed mineral horizon,<br />
usually in the A horizon. These usually thin, compacted soil layers are typically found<br />
near the soil surface <strong>and</strong> are due to cultivation, especially to disking used in rice<br />
seedbed preparation <strong>and</strong> to extensive traffic by heavy machinery such as harvesters.<br />
In rice <strong>production</strong>, these operations are performed frequently when the fine-textured<br />
soil is wet. The compacted pans tend to reduce or inhibit root distributions o f some<br />
arable crops <strong>and</strong> the infiltration <strong>and</strong> redistribution o f water in the profile.<br />
4. Fragipan, x. The symbol ‘‘x” is used to indicate genetically developed layers<br />
that have a com bination o f firmness, brittleness, <strong>and</strong> very coarse prisms with few to<br />
many bleached vertical faces. The fragipan is a natural subsurface horizon with a low<br />
organic matter content, high bulk density <strong>and</strong>/or high mechanical strength relative<br />
to overlying <strong>and</strong> underlying horizons, a hard or very hard consistence when dry, but<br />
showing moderate to weak brittleness when moist. Fragipan horizons tend to restrict<br />
the vertical redistribution o f water within <strong>and</strong> through the profile,<br />
5. Calcic horizon, k. This is a mineral soil horizon containing secondary<br />
carbonate enrichm ent that is greater than 15 cm thick, has a calcium carbonate<br />
(CaCOs) equivalent greater than 150 g/kg, <strong>and</strong> at least 50 g/kg more CaCOa tlian that<br />
o f the underlying C horizon.<br />
6. Petrocalcic horizon, km. This is a continuous, indurated calcic horizon that is<br />
cemented by CaCOs <strong>and</strong>, in some places, with magnesium carbonate (MgCOs). It<br />
cannot be penetrated with a spade or auger when dry, dry fragments do not slake in<br />
water, <strong>and</strong> it is impenetrable to roots.<br />
7. Duripan, qm. This is a subsurface soil horizon that is cemented by illuvial<br />
silica, usually opal or microcrystalline forms o f silica, to the degree that less than<br />
50% o f the volume o f air-dry fragments will slake in water or HCl.<br />
8. Iron-manganese concretions, c. The symbol “c” is used to indicate iron <strong>and</strong><br />
manganese accumulation. These are cemented bodies that can be removed from the<br />
soil intact. Concretions have cemented concentrations o f a chemical compound, such<br />
as hematite (FezOa), with crude, concentric internal symmetry usually organized<br />
around a point.<br />
9. Gleyed, g. The symbol “g” indicates that iron has been reduced <strong>and</strong> removed<br />
or that prolonged saturation with stagnant water has preserved a wet state. This is<br />
a result o f long-term poor aeration, usually because o f high water retention <strong>and</strong><br />
excess water. Soil colors are grays to pastel blues <strong>and</strong> greens <strong>and</strong> mottles of variously<br />
colored soils frequently are observed. Gleying occurs under reducing conditions, by<br />
which the ferric ion (Fe^+) is reduced predominantly to the ferrous ion (Fe^^).
ï|5i<br />
304<br />
Production<br />
10. Slickensidesy $s. The symbol "ss” is used to indicate that slickensides are<br />
present. Slickensides result from the swelling o f clay minerals <strong>and</strong> shear failure with<br />
subsequent large volumes of soil sliding over another in soils subject to targe changes<br />
in water content. The peds tend to have smooth pressure surfaces <strong>and</strong> are indicators<br />
that otlier vertical characteristics such as surface cracks m aybe present.<br />
Other morphological features o f rice soils that are frequently observed <strong>and</strong> included<br />
in the profile description are:<br />
-lils<br />
iS i<br />
Mf<br />
11. Clay films. These are coatings o f oriented clay on the surfaces o f peds <strong>and</strong><br />
mineral grains, <strong>and</strong> lining pores. They occur along the walls o f water-conducting<br />
macropores <strong>and</strong> may indicate flows associated with clay movement. In Alfisols, clay<br />
films o f very fine clay develop along ped faces, indicating low water flow rates. Sût<br />
<strong>and</strong> even s<strong>and</strong> particles may be moved at higher flow rates, which may occur after<br />
intense rainstorms.<br />
12. Mottles. M ottling phenomena are defined by the USD A -$CS (1993) in<br />
terms o f colors with chromas of two or less <strong>and</strong> indicate reducing conditions.<br />
Reducing conditions are defined as corresponding to pressure heads m ore than - 1<br />
IcPa. (U SD A-SCS, 1993). Mottles are spots or blotches o f different color or shades of<br />
color interspersed with the dom inant color. Visible mottling is formed by solution<br />
o f Fe <strong>and</strong> M n compounds during reduction. As the redox potential decreases, Mn<br />
compounds are reduced first, followed by Fe. The reverse occurs when a reduced<br />
solution containing both compounds oxidizes. ■<br />
In the humid regions o f the United States, rice soils often have an aquic moisture<br />
regime. This indicates that these soils are saturated with water <strong>and</strong> virtually free of<br />
gaseous oxygen for sufficient periods of time for evidence o f poor aeration (gleying,<br />
mottling) to occur.<br />
PHYSICAL AND CHEMICAL PROPERTIES OF RICE SOIL PROFILES<br />
Soil physical <strong>and</strong> chemical properties that affect the growth <strong>and</strong> development of<br />
rice tend to be expressed by the magnitude o f water, gas, <strong>and</strong> nutrient transport<br />
characteristics as well as the concentrations <strong>and</strong> chemical states o f the elements within<br />
the profile. In this section we discuss these soil properties as they relate to rice growth.<br />
Physical Properties<br />
Color<br />
Color results from parent material, soil development, cropping, <strong>and</strong> management.<br />
Color notation is divided into three components: hue, value, <strong>and</strong> chroma. Hue is the<br />
dom inant spectral color (e.g., red, yellow, blue, <strong>and</strong> green). Value indicates the relative<br />
blackness or whiteness (i.e., the amount o f reflected light). Chroma represents the<br />
purity o f the color. The color o f m ost rice soil horizons range from light to dark gray,<br />
<strong>and</strong> these soils often contain horizons with a chroma < 2, which is indicative o f a low
<strong>Rice</strong> Soils; Physical ond Chemical Charatteristics <strong>and</strong> Behavior 305<br />
level o f aeration (Tables 3.3.1 to 3.3.3). Due to periodic submergence <strong>and</strong> aeration<br />
during rice cultivation, many soil profiles have orange-red (rust-colored) mottles,<br />
which are caused by the oxidation o f iron to various oxides. This coloring develops in<br />
the most easily oxidized parts, such as cracks <strong>and</strong> root channels. The dom inant soil<br />
color may be gray.<br />
Dark soils tend to absorb more heat than light soils, which affects the energy<br />
balance at the soil surface. However, because tliese dark-colored soils often contain<br />
m ore water than light-colored soils, due to higher organic matter, dark soils are not<br />
necessarily warmer than adjacent lighter-colored soils.<br />
Texture <strong>and</strong> Structure<br />
<strong>Rice</strong> soils in the United States tend to be predominantly in the fine textural classes,<br />
such as loam , silt loam, silty clay loam, clay loam, <strong>and</strong> clay. Often with Alfisols, silty<br />
surface textures overlie clays <strong>and</strong> clay loams, due primarily to the mode <strong>and</strong> time<br />
o f soil formation. The mineralogical composition o f the clays tends to be mixed or<br />
smectitic, but kaolinites <strong>and</strong> vermiculites are also com mon. Soils with high clay contents<br />
tend to have restricted drainage <strong>and</strong> require less water during rice <strong>production</strong>,<br />
depending on the clay minerals present. Conversely, soils with higher s<strong>and</strong> contents<br />
tend to have greater drainage <strong>and</strong> therefore require greater amounts o f water during<br />
rice <strong>production</strong>.<br />
<strong>Rice</strong> soils containing sm ectitic clays (e.g,, the Sharkey <strong>and</strong> Willows series) tend<br />
to have large surface areas <strong>and</strong> form massive, cloddy structures upon drying. They<br />
also are easily puddled. These soils tend to swell upon flooding, which reduces the<br />
effective pore radius <strong>and</strong> hydraulic conductivity.<br />
Water Balance <strong>and</strong> Water Use<br />
The relationships between the inputs <strong>and</strong> outputs o f water in a rice field can be<br />
quantified by the seasonal water balance equation<br />
p + i - e t ± d ± R t:= a w<br />
(1)<br />
where P is precipitation, / is irrigation, E T h évapotranspiration, D is internal drainage,<br />
R is runoff, <strong>and</strong> A W is the change in soil water storage. The units o f equation<br />
(1) can be either cumulative units such as millimeters or differential units such as<br />
mm/day. Since over the rice-growing season, P < E T , rice grown in tlie United States<br />
is irrigated <strong>and</strong> requires extensive amounts o f water. For example, Scott et al. (1998)<br />
estimated that long-term cumulative water deficit from June to August was 221 m m in<br />
Stuttgart, Arkansas. Therefore, the quantity <strong>and</strong> quality o f available water <strong>and</strong> its subsequent<br />
use by the rice cropping system are m ost im portant factors in rice <strong>production</strong>.<br />
The inputs o f water include P <strong>and</strong> / <strong>and</strong> the proportion o f water added by P<br />
<strong>and</strong> I varies with location <strong>and</strong> tim e during the growing season. Almost no rainfall<br />
occurs during the rice-growing season in California, whereas rainfall during the<br />
summer in the m id-south <strong>and</strong> Gulf coastal plains regions contributes significantly<br />
to available water use. The sources o f irrigation water also varies by region. Surface<br />
water sources include on-farm reservoirs <strong>and</strong> canals that are connected hydraulically<br />
to rive:'*'. Groundwater sources include the water pumped from aquifers.
<strong>Rice</strong> soils are managed in a special way during tlie growing season. For example,<br />
water management practices in Arkansas usually include (1) leveling o f the l<strong>and</strong> <strong>and</strong><br />
construction o f levees to impound water, (2) flooding o f the field <strong>and</strong> maintenance<br />
o f 5 to 10 cm o f st<strong>and</strong>ing water during the 3 to 4 m onths that the crop is grown,<br />
<strong>and</strong> (3) draining <strong>and</strong> drying tlie fields for harvest. During the rice-growing season,<br />
water is added to the field as precipitation <strong>and</strong> irrigation, <strong>and</strong> lost from the field as<br />
évapotranspiration, internal drainage, seepage through the levees, <strong>and</strong> flow through.<br />
the field. In the raid-south region rice is often grown in rotation with crops such as<br />
soybean, wheat, <strong>and</strong> grain sorghum. O ther irrigation practices in the United States<br />
include:<br />
Water-seeded rice, where presoaked seeds are broadcast into the floodwater.<br />
This method is used primarily in parts o f Louisiana, Texas, <strong>and</strong> California<br />
(Arkansas Cooperative Extension Service, 1996). A variant o f this method is<br />
pinpoint irrigation, whereby germinated seeds are dropped into the floodwater,<br />
the field is drained 24 hours later, <strong>and</strong> the field is left to dry for a period of 3 to<br />
5 days before the flood is reestablished until harvest (Roel et 1999).<br />
Only a few farmers who cultivate gently slopping l<strong>and</strong>s use furrow irrigation.<br />
This method is viable only if the rice nitrogen fertilization strategy is modified<br />
(Wells et a l, 1991).<br />
Sprinkler irrigation has been shown to affect rice yields negatively (McCauley,<br />
1990) <strong>and</strong> is therefore not a recommended practice.<br />
<strong>Rice</strong> fields are typically flat <strong>and</strong> l<strong>and</strong> planed to a grade. Levees, which are constructed<br />
to retain the water within a paddy, are typically low, so that harvesting<br />
equipment can move across them. The trend toward precision grading the l<strong>and</strong> <strong>and</strong><br />
construction of rectangular paddies continues in the United States, resulting in more<br />
efficient water management than with paddies that follow the contour.<br />
The outputs o f water include E T , D, <strong>and</strong> R. Surface runoff includes the loss of<br />
water from the lower end of the field <strong>and</strong> from seepage through the levees. For well-<br />
managed rice grown on appropriate soils, ET is the predominant mode o f water loss.<br />
For example, measured average daily £!T in Florida was 6.5 mm/day, <strong>and</strong> cumulative<br />
ET ranged from 740 to 880 m m during flooding (Shih et al., 1982). In eastern Texas,<br />
McCauley (1990) estimated that cumulative rice E T over a 3-year period ranged from<br />
754 to 906 m m over an entire crop season. Roel et al. (1999) showed that flooded<br />
soil ET varied from 5.8 to 7.7 mm/day over a 2-year period. In Arkansas, Renaud<br />
et al. (2000) estimated rice ET with two different approaches, <strong>and</strong> cumulative rice<br />
ET in 1998 ranged from 609 to 663 m m , depending on the estimation method used.<br />
<strong>Rice</strong> yield also has been shown to be proportional to E T , It is therefore important to<br />
quantify rice<br />
so as to optimize yields <strong>and</strong> conservation of water resources.<br />
M any methods have been developed to estimate ET. These can be classified as<br />
mechanistic, based on com bination theory (both mechanistic <strong>and</strong> empirical in nature),<br />
or purely empirical, site-specific formulations (Burm an et a l, 1983; Rosenberg<br />
et al., 1983). An example o f a mechanistic model is the Penm an-M onteith equation,<br />
which assumes that water vapor diffuses first out o f the leaves o f a crop against<br />
stomatal resistance <strong>and</strong> then into the atmosphere against aerodynamic resistances<br />
(Shuttleworth, 1993). Allen et al. (1994) <strong>and</strong> Allison et al. (1994) proposed a modified
<strong>Rice</strong> Soils; Physical ond Chemical Characteristics <strong>and</strong> Behovior 307<br />
24-hour Penm an-M onteith equation for the calculation o f a grass reference crop ETq<br />
(defined as a hypothetical reference crop with a crop height o f 0.12 m, a fixed surface<br />
resistance o f 70 s/m, <strong>and</strong> an albedo o f 0.23):<br />
0.408A (j?„ - G ) -p K[900f/2(e„ - e,)j{T + 273)]<br />
A + r C l+ 0 .3 4 i7 a )<br />
(2)<br />
where ETqhas units o f mm/dayi A is the slope o f the vapor pressure-temperature<br />
curve (kPa/°C),<br />
is the net radiation flux density (MJ/m^) per day), G is the soil heat<br />
flux density away from the surface (MJ/m^ per day), y is the psychrometer constant<br />
(kPa/°C), U2 is the wind speed at 2 m height„e„ is the mean saturation vapor pressure<br />
o f air (kPa), e^i is the saturation vapor pressure at dewpoint (IcPa), <strong>and</strong> T is the<br />
mean daily air temperature (°C). ET^ needs to be multiplied by a crop coefficient<br />
(Doorenbos <strong>and</strong> Pruitt, 1977) to obtain rice ET. M ost o f the terms in equation (2)<br />
can be measured directly or at least estimated from com m only measured clim atic<br />
parameters (see Allen et al., 1994).<br />
In addition, there are many purely empirical models developed to estimate ET,<br />
For example, Yoshida (1979) derived linear relationships to relate rice iST to total<br />
incoming radiation <strong>and</strong> pan evaporation {Ep) for humid regions. Analyzing a large<br />
database from South <strong>and</strong> Southeast Asia, Tomar <strong>and</strong> O’Toole (1980a) determined that<br />
rice E T during flooding could be estimated fairly accurately by multiplying class A Ep<br />
by a coefficient o f 1,2. For the rice-producing regions o f the United States, however, it<br />
is possible that another coefficient should be used. Brown et al. (1978) in Texas found<br />
that the coefficient ranged from 1.2 to 1.4. On the other h<strong>and</strong>, Loiirence <strong>and</strong> Pruitt<br />
(1971) in California suggested that the coefficient should be close to 1. Finally, rice<br />
E T can also be determined in situ with specifically designed lysimeters (Tomar <strong>and</strong><br />
O ’Toole, 1980b).<br />
Hydraulic Conductivity <strong>and</strong> Drainage<br />
M ost rice soils have low saturated hydraulic conductivity (.STg^J in parts o f their soil<br />
profile, either naturally or artificially. This leads to a severe restriction in vertical<br />
drainage o f water. Since m ost rice soil profiles are physically heterogeneous, the drainage<br />
flux density under steady-state saturated conditions is given by Darcy’s law as<br />
- A / f<br />
(3)<br />
where<br />
is tlie drainage flux density (mYm^ per second), A H is the total hydraulic<br />
head (m) difference between the soil surface <strong>and</strong> bottom o f the root zone (i.e., approximately<br />
1 m ), <strong>and</strong> R is the hydraulic resistance to flow (s“^), which is summed<br />
over all horizons (or depth intervals) in the root zone. The total hydraulic head H can<br />
be written as<br />
H = p-\-z (4)<br />
where p is the soil water pressure head (m) <strong>and</strong> z is the gravitational head (m )<br />
assuming that the positive z direction is upward. The hydraulic resistance is given by
Production<br />
R =<br />
L<br />
i^err<br />
(5)<br />
where L is the thickness (m ) <strong>and</strong><br />
is the effective hydraulic conductivity (m/s) of<br />
the saturated profile. The effective hydraulic conductivity can be determined from<br />
E L ;<br />
S ( L ,/ ü:,-) L./ÜC, -f L,/K, + ■••+ L JK „<br />
(6)<br />
where the subscript i represents the horizon num ber starting from the soil surface to<br />
the lowest saturated horizon, designated as n. Equation (6) indicates that the effective<br />
hydraulic conductivity o f the saturated profile is a function o f the ratio o f the horizon<br />
thickness to the hydraulic conductivity o f each horizon. It also indicates that the<br />
horizon with the lowest has the greatest influence on restricting the drainage rate<br />
from the profile. Methods to measure o f undisturbed soil samples were published<br />
by Amoozegar <strong>and</strong> W arrick (1986), Klute <strong>and</strong> Dirksen (1986), <strong>and</strong> Hasegawa (1987).<br />
The effects o f clay <strong>and</strong> Na contents on the JCsat o f a Stuttgart sUt foam are presented<br />
in Table 3.3.4. The Stuttgart soil is classified as a fine, sm ectitic, therm ic lypic<br />
Natrudalfs <strong>and</strong> is the state soil of Arkansas. It is frequently planted to a 1:1 rotation of<br />
rice <strong>and</strong> soybeans. This soil was sampled in 10-cm increments to 1 m <strong>and</strong> subsequently<br />
analyzed for textural composition, total porosity, bulk density, Na content, <strong>and</strong><br />
pH. In the Stuttgart profile, the bulk density, clay, <strong>and</strong> sodium contents generally<br />
increased with depth, <strong>and</strong> total porosity, Agat, <strong>and</strong> silt content generally decreased with<br />
depth. Using equations (3) to (5), these tabular data can be used to calculate the<br />
<strong>and</strong> Qyj values from a saturated Stuttgart profile from conditions where 10 cm o f water<br />
was continuously ponded on the soil surface. The effective hydraulic conductivity of<br />
the Stuttgart profile is 3.9 x lO "'” m/s, <strong>and</strong> the steady-state drainage rate is 4.3 x<br />
10~‘* m/s. This is a very low drainage rate, which illustrates why the Stuttgart soil is<br />
efficient in restricting the internal drainage o f water during rice <strong>production</strong>. Over a<br />
ponding duration of 75 days, this drainage loss amounts to about 0.3 m m o f water<br />
from the profile. The primary reason for the low drainage rate from the profile is<br />
due to the low in the lower portion o f the profile (Table 3.3.4). These are the<br />
TABLE 3.3.4.<br />
S e le cte d P h y sic a l a n d C h e m ic a l P ro p e rtie s o f th e S tu ttga rt S o il in A r k a n s a s<br />
Soil B ulk Total Saturated Sodium<br />
Depth Density Porosity Hydraulic Conductivity Silt Clay Content<br />
H (Mg/m®) (m®/m®) (ms-1 X 10-^ {%) (%) (mg/ha) pH<br />
0 -0 .0 5 1.23 0.537 13.889 82.9 14.2 104 5.7<br />
0.10-0,15 1.43 0.462 6.944 77.4 17.5 221 6,6<br />
0 .2 0 -0 .2 5 1.45 0.451 8.75 74.4 20.7 283 5.8<br />
0.30-0.35 1.46 0.448 31.611 70.1 25.7 298 5.2<br />
0.4 0 -0 .4 5 1.41 0.467 33.333 64.8 30.7 356 5.1<br />
0 .50-0.55 1,42 0.462 0.361 69.1 23.8 505 5.3<br />
0.60-0.65 1.42 0.464 0.0028 60.7 34.7 794 5.2<br />
0.7 0 -0 .7 5 1.44 0.456 0.0025 51.5 44.5 1084 5.4<br />
0.80-0.85 1.56 0.411 0.0011 46.5 49.9 1313 5.2<br />
0.9 0 -0 .9 5 1.63 0.385 0 .0 0 1 1 48.7 47.8 1290 5.3
<strong>Rice</strong> Soils; Physical <strong>and</strong> Chemical Chargtferistics <strong>and</strong> Behavior 309<br />
depths at which the clay <strong>and</strong> Na contents increase significantly over those found in<br />
the surface depth intervals. Low drainage rates save water <strong>and</strong> reduce vertical losses<br />
o f plant nutrients <strong>and</strong> pesticides from the profile.<br />
Usually, poor internal drainage is caused by low permeability horizons such as<br />
clay layers, pans including traffic pans <strong>and</strong> fragipans, <strong>and</strong> to elevated Na contents.<br />
However, only clay minerals such as smectites <strong>and</strong> to a lesser extent vermiculites<br />
that have high shrink-swell potential are effective in limiting drainage under tlie<br />
wet conditions typically found in rice fields. In addition, some soils may have poor<br />
drainage because they occur in l<strong>and</strong>scapes where they accumulate more water than<br />
they can dissipate by their slow natural drainage. After heavy rains, poorly drained<br />
soils talce longer to lose surface water by internal drainage. However, even in soils<br />
with low A'sat, some drainage can occur rapidly through preferential flow pathways<br />
that may not be detected when determining A'sat in the laboratory with small soil<br />
samples. These pathways can be referred to as macropores^ which have been defined<br />
by Seven <strong>and</strong> Germann (1982) as pores formed by soil fauna, pores formed by plant<br />
roots, cracks, fissures, <strong>and</strong> natural soil pipes created by subsurface erosion. The three<br />
types of preferential flow in soils are (Miyazald, 1993) bypassing flow, fingering flow,<br />
<strong>and</strong> funneled flow. For example, in a poorly drained Calloway silt loam o f eastern<br />
Arkansas, some preferential flow was observed through the plow pan (Renaud, 2000)<br />
<strong>and</strong> the fragipan (J. Davis, personal com m unication, 2000).<br />
Aeration<br />
Soil aeration includes the status <strong>and</strong> biological availability of gases in soil <strong>and</strong> the<br />
exchange of these gases between the soil <strong>and</strong> the atmosphere (Scott, 2000). The status<br />
<strong>and</strong> availability o f gases in soil involves the com position o f soil air, solubility o f gases<br />
in water, <strong>and</strong> the gaseous transport coefficients in soil water <strong>and</strong> in soil air. Soil gases<br />
are im portant because they are involved in respiration processes, conducted by all<br />
plant <strong>and</strong> animal cells, <strong>and</strong> in photosynthesis, which creates sugars, a fundamental<br />
building block for all food.<br />
W hen the soil surface is wet <strong>and</strong> inundated with water, the exchange o f gases<br />
between the soil <strong>and</strong> the atmosphere is restricted considerably. Thus, the resupply<br />
o f oxygen to the soil is transport dependent, <strong>and</strong> the removal o f CO 2 from the soil<br />
profile also is restricted. W ithin a few hours o f soil submergence, microorganisms<br />
extract the O2 present in the water <strong>and</strong> trapped in the soil <strong>and</strong> render the submerged<br />
soil practically devoid o f molecular O2. Eventually, a decrease in aerobic respiration<br />
in the soil results. However, when a rice field is flooded, the floodwater generally<br />
has relatively high concentrations o f O 2 because of the low density o f O2-consuming<br />
organisms, photosynthetic O2 <strong>production</strong> by algae, <strong>and</strong> mixing o f water by wind<br />
action. This creates a shallow oxidized layer at the soil surface. Movement o f O 2<br />
below that layer is slow because o f the slow rates o f O2 diffusion in wet soils (Howeler<br />
<strong>and</strong> Bouldin, 1971). For m ost arable crops, poorly aerated soil conditions drastically<br />
affect the growth <strong>and</strong> development o f crops (Scott et al., 1989). However, this is not<br />
a problem with rice after the four- to five-leaf growth stages, because oxygen in rice<br />
shoots is transported down the stems via the aerenchyma tissue to support respiration<br />
o f root cells while growing in water-saturated soil.<br />
The com position o f gases in soil is a function o f the processes o f consumption <strong>and</strong><br />
<strong>production</strong> o f gases by microorganisms <strong>and</strong> plants, <strong>and</strong> transport within the profile.
310 Production<br />
B<br />
For soil, O 2 <strong>and</strong> CO 2 are the m ajor gases, with atmosphere as the dom inant source<br />
for O 2 <strong>and</strong> tlie soil as the source for CO2. Oxygen is consumed mainly in respiration;<br />
however, in rice <strong>production</strong>, O2 is also produced by algae assimilating CO 2 at the soil<br />
surface <strong>and</strong> by the diffusion of O2 from the leaves to the roots. Under weU-aerated,<br />
well-drained conditions, the com position o f the soil atmosphere is similar to the<br />
atmosphere with about 79.1% N2, 20.8% O2 <strong>and</strong> 0.035% CO 2. Under wet soil, poorly<br />
drained conditions, however, the concentration o f N 2 in soil air remains relatively<br />
constant, but soil air concentrations o f O 2 <strong>and</strong> CO 2 tend to be inversely related with<br />
a decrease in O2 accompanied by an increase in CO 2 concentration.<br />
The aqueous solubility o f gases is a function o f temperature (Glinski <strong>and</strong> Step-<br />
niewsld, 1985). The effects o f temperature on the solubility coefficients o f the O2 <strong>and</strong><br />
CO2 in air <strong>and</strong> in water is given in Table 3.3.5, This shows that the solubility o f these<br />
gases in both mediums decreases with an increase in temperature. Solubility o f O2 in<br />
water tends to be lower than that o f CO2 by a factor o f about 50.<br />
T he concentration o f gas in soil is the sum o f the proportional contributions from<br />
the water <strong>and</strong> air phases. Mathematically, this can be determined from the equation<br />
(7)<br />
1 6<br />
where C is the soil gas concentration (kg/m^), f„ is the aeration porosity (mVm^), Cg<br />
is the concentration o f the gas in the soil air phase (kg/m^),<br />
is the volumetric soil<br />
water content (mVm^) , <strong>and</strong> Q is the concentration o f the gas in the soil water phase<br />
(kg/m^). Under flooded conditions, values o f /
Rite Soils; Physical <strong>and</strong> Chemical Characteristics <strong>and</strong> Behavior 311<br />
Transport o f aqueous dissolved gases in rice soils occurs by two soil mechanisms:<br />
convective flow <strong>and</strong> diffusion, <strong>and</strong> by one plant mechanism, diffusion. Convective<br />
flow occurs when oxygen-saturated surface water enters the soil through vertical<br />
percolation. For steady-state flow conditions, the convective oxygen flux density is<br />
quantified by<br />
Jc ~ (8)<br />
where is the oxygen convective flux density (kg/m^ per second), is the Darcy flux<br />
density o f water (m/s), <strong>and</strong> Q is the concentration o f oxygen in the water (i.e., tlie<br />
dissolved oxygen in the percolating water). As presented in Table 3.3.5, the dissolved<br />
concentration o f oxygen in water is low, <strong>and</strong> under conditions where infiltration is<br />
low, the amount o f oxygen supplied by convective flow is insufficient to supply the<br />
needs o f the rice plant <strong>and</strong> the microbial community.<br />
Under steady-state conditions the diffusive transport o f dissolved gas in soil water<br />
can be quantified by Pick’s first law. Mathematically, this equation is<br />
/ n Jd = —D e-----<br />
Hz<br />
(9)<br />
where<br />
is the gas flux.density (kg/m^ per second), De is the effective diffusion<br />
coefficient (mVs) o f the gas, Q is the dissolved concentration o f the gas (kg/m^), <strong>and</strong><br />
z is the spatial coordinate. Pick’s law indicates that the diffusive flux density o f a gas<br />
is the product o f the molecular diffusion coefficient <strong>and</strong> the dissolved concentration<br />
gradient o f that gas. Values o f<br />
are positive in the positive z direction. The molecular<br />
diffusion coefficients o f O2 <strong>and</strong> CO2 in air <strong>and</strong> in water as a function o f temperature<br />
are presented in Table 3.3.6. These data show that the molecular diffusion coefficients<br />
o f O 2 are slightly greater than COain both mediums. Molecular diffusion coefficients<br />
o f these gases are roughly 10,000 times faster in air than in water. Therefore, the aeration<br />
porosity <strong>and</strong> water content are im portant factors in determining the magnitude<br />
o f the gas diffusion coefficient in soil.<br />
In rice soil systems, the gaseous diffusion coefficients are further reduced by the<br />
solid m atrix <strong>and</strong> tortuosity. The effective diffusion coefficient, D e, is defined as<br />
De —Do ■ (10)<br />
where Do is the molecular diffusion coefficient in a pure medium such as water or air<br />
(mVs) (Table 3.3.6) <strong>and</strong> x is the tortuosity factor with a magnitude ranging from 0.1<br />
in compacted systems to about 0.5 in rice-based saturated soil systems.<br />
Steady-state conditions rarely prevail in agricultural soils, <strong>and</strong> gaseous movement<br />
should be studied under transient-state mathematical formulations. The transientstate<br />
equation describing the one-dimensional transport by diffusion <strong>and</strong> convection<br />
<strong>and</strong> consumption o f dissolved oxygen in submerged soil is<br />
3C d'^C dC ^ ^<br />
Ht “ 3z^ "az<br />
( 11)<br />
where C is the dissolved oxygen concentration in the submerged soil, t is tim e, z is<br />
depth in the flow direction, D is diffusivity/dispersion coefficient o f dissolved oxygen.
Production<br />
TABLE 3.3.6.<br />
D iffu s io n C o e fficie n ts o f G a s e s a t N o r m a l P re ssu re Fre q u e n tly<br />
F o u n d in th e S o il as a Fu n c tio n o f T e m p e ra tu re<br />
O 2 (m Vs) CO 2 K / S )<br />
111<br />
Temperature<br />
X<br />
A ir<br />
(X 10”')<br />
W ater<br />
(X 10“')<br />
A ir<br />
(X 10”')<br />
W ater<br />
(X 10-’)<br />
10 1.89 1.54 1.48 1.46<br />
15 1.95 1.82 1.53 1,63<br />
20 2.01 2.1 1.59 1.77<br />
25 2.07 2.38 1.64 1.92<br />
30 2.14 2.67 1.7 2.08<br />
Source; A dapted fro m G linski <strong>and</strong> Stepniew sld (1985).<br />
i s :<br />
Vis the average pore water velocity (m/s), R (Q —C„,) is the oxygen consumption rate<br />
in the soil due to chemical <strong>and</strong> biological absorptions, <strong>and</strong><br />
is the lowest oxygen<br />
concentration (Phuc et a l, 1976). The average pore water velocity is the ratio of the<br />
soil water flux density<br />
<strong>and</strong> the water-filled porosity o f the soil. Equation (11) is<br />
known as the convective dispersion equation with consumption for mass transport<br />
in soil.<br />
W hen the velocity of soil water through the profile is negligible, the contribution<br />
o f convective flow to the transport of oxygen is negligible <strong>and</strong> diffusion is the<br />
only operating transport mechanism. Under these conditions, equation (11) can be<br />
rewritten as<br />
ac,<br />
dt '<br />
dz^<br />
R{Ct - C,„) ( 12)<br />
which is Pick’s second law with a consumption term (Phuc et al., 1976). If there is no<br />
gas transport in the system, equation (12) can be written as<br />
8 Q<br />
1 7<br />
= -R (Q - C,„) (13)<br />
which indicates that the rate o f change in dissolved oxygen concentration is proportional<br />
to the consumption rate. Dissolved oxygen consumption rates o f saturated soils<br />
were determined by Phuc et al. (1976) in a s<strong>and</strong>/clayey soil column to be 0.00656 per<br />
hour. Howeler <strong>and</strong> Bouldin (1971) found that soil O 2 consumption rates varied with<br />
the soil <strong>and</strong> the initial O2 concentration <strong>and</strong> ranged to about 3 x 1 0 “*^mg/cm"^ per<br />
second. These rates in soil were 300 to 800 times higher than in the overlying water.<br />
Soils with higher organic matter contents tend to have higher m icrobial respiration<br />
rates <strong>and</strong> a thin oxidized zone. In the soils used in their experiments, oxidation of<br />
chemically reduced species was about as large a sink for O2 as m icrobial respiration.<br />
TemperaturB <strong>and</strong> Thermal Characteristics<br />
Soil temperature is a physical property that affects m ost physical, chemical, <strong>and</strong> biological<br />
processes occurring in soil. For physical <strong>and</strong> chemical processes, the higher the<br />
temperature, the faster the rate o f the process. For biological processes where enzymes<br />
■
Ríce Soils: Physical <strong>and</strong> Chemicol Characteristics <strong>and</strong> Behavior 313<br />
are involved, however, a maxim um rate is usually observed. <strong>Rice</strong> plants vary widely<br />
in the soil temperature range (20 to 38°C) at which they grow best, <strong>and</strong> yet there is an<br />
optim um temperature between 30 <strong>and</strong> 32'^C (Sys, 1985).<br />
The temperature at the soil surface is a function o f the radiant energy balance<br />
(van W ijk <strong>and</strong> de Vries, 1963). The net radiation is affected by climatic factors such<br />
as tim e o f the year, tim e o f day, latitude, cloudiness, <strong>and</strong> so on, <strong>and</strong> soil factors such<br />
as color, mineralogy, water content, slope, aspect, <strong>and</strong> density <strong>and</strong> type o f vegetation.<br />
W hen all other factors are equal, dark-colored soils absorb m ore energy than light-<br />
colored soils, <strong>and</strong> wetter soils absorb more energy than drier soils. In a rice cropping<br />
system, the floodwater acts as an energy sink during periods o f high radiant<br />
energy <strong>and</strong> as an energy source during periods o f low radiant energy flux during low<br />
radiant energy fluxes (e.g., at night). Thus it provides the heat energy necessary to<br />
drive evaporation <strong>and</strong> m aintain higher temperatures. The deeper the flood depth, the<br />
greater the thermal capacity o f the source or sink, <strong>and</strong> the more constant the thermal<br />
environment (Ferguson, 1970).<br />
Soil temperature is a function o f the volumetric heat capacity, thermal conductivity,<br />
<strong>and</strong> therm al diffusivity o f the soil <strong>and</strong> is spatially <strong>and</strong> temporally variable. The<br />
volumetric heat capacity, C„, is defined as the am ount o f heat required to raise (or<br />
Ipwer) the temperature o f a unit volume o f soil by 1 degree Celsius (or Kelvin). In<br />
the SI system the units o f Cy are J/m^ per degree Kelvin. The heat capacity governs<br />
how rapidly the change in soil temperature will occur in response to the absorption<br />
or release o f heat. Examples o f the heat capacities o f soil materials in rice <strong>production</strong><br />
are given in Table 3.3.7. Mathematically, the heat capacity o f soil is a function o f the<br />
proportions o f the three soil phases. For mineral soils C„ can be estimated by<br />
Cy = 837p,, -b 4.18 X IQ% (14)<br />
where p,, is the bulk density (kg/m^) <strong>and</strong> Oy is the volumetric water content (mVmO-<br />
Equation (14) indicates that C„ is directly proportional to soil com paction, as expressed<br />
by bulk density <strong>and</strong> soil water content. For most rice soils, C„ ranges between<br />
1.5 <strong>and</strong> 3.5 MJ/m^ per degree Kelvin, with the higher values found when the soil is<br />
saturated <strong>and</strong> compacted.<br />
Heat can be transported in rice soils by conduction, convection, <strong>and</strong> radiation.<br />
O f these transport mechanisms, the m ost dom inant is conduction. Transport o f heat<br />
TABLE 3.3 J .<br />
Thermal Parameters of Selected Materials at 20°C <strong>and</strong> 1 atm<br />
Therm al<br />
Therm al<br />
Conductivity<br />
Heat Capacity<br />
{J/m<br />
Therm al<br />
Heat<br />
(MJ/m’<br />
per second<br />
Diffusivity<br />
M aterial<br />
per Kelvin)<br />
per Kelvin)<br />
{m V s X 1 0 "")<br />
Quartz 1.92 8.36 43<br />
Many soil minerals 1.92 2.93 15<br />
Organic matter 2.51 0.25 1<br />
Water 4.18 0.59 1.4<br />
Air 0.0012 0.026 2.1<br />
Source: Data from van Wijk <strong>and</strong> De Vries (1963).
314 Production<br />
by conduction occurs by the transm ission o f translational, rotational, <strong>and</strong> vibrational<br />
energy from molecule to molecule. Conduction can be viewed as the transfer o f heat<br />
from the more energetic to the less energetic particles <strong>and</strong> molecules due to the<br />
interactions between the particles <strong>and</strong> between the molecules. In one-dimensional<br />
steady-state soil systems, conduction o f heat is quantified by Fourier's law:<br />
dz<br />
(15)<br />
i : F<br />
where H is the heat flux density (J/m^ per second or W/m^), k is the thermal conductivity<br />
(J/m per second per degree Kelvin), T is the soil temperature (K), <strong>and</strong> z<br />
is the spatial coordinate. The ratio 9 T/9 ^ is the slope of the temperature-distance<br />
relationship <strong>and</strong> serves as the driving force for heat conduction in soil. Equation (15)<br />
indicates that the amount o f heat conducted is the product o f the heat transport<br />
coefficient k <strong>and</strong> the temperature gradient BT/dz- The heat flux density is positive<br />
in the positive z direction.<br />
The thermal conductivity, k, is the steady-state transport coefficient for conduction<br />
o f heat in soil <strong>and</strong> is defined by equation (15). Its value depends on the mineral<br />
<strong>and</strong> organic com position <strong>and</strong> soil water content (Table 3.3.7). Values o f ¿ are higher<br />
in soil minerals than in either water or air alone, <strong>and</strong> are higher in water than, in<br />
air, which is quite low. Therefore, thermal conductivity increases with increasing<br />
(Scott, 2000). This is due to the replacement o f gases by water, which has a higher k<br />
value in the soil pore space.<br />
The temperature regimes of most rice soils are transient-state systems where<br />
the heat flux density varies with external conditions such as solar radiation (time<br />
during the growing season <strong>and</strong> time o f day) <strong>and</strong> vegetative growth stages as well<br />
as soil properties such as water content, mineralogy, compaction, <strong>and</strong> so on. The<br />
one-dimensional transient-state Fourier heat flow equation for conduction can be<br />
expressed as<br />
" St dT V 3z /<br />
( 16)<br />
or if k <strong>and</strong><br />
are independent of z, equation (16) becomes<br />
BT _<br />
Bt<br />
B^T<br />
Bz^<br />
(17)<br />
where a is the thermal diffusivity (m^/s), which is defined by the ratio k ( C„. Values<br />
of a determine the rate at which a substance heats or cools as a result o f a thermal<br />
gradient. Thus it is the rate o f change o f soil temperature with time. Representative<br />
values o f a for soil components are given in Table 3.3.7. Solids such as quartz have<br />
tlie highest a, value. Since soils can be considered as a three-phase system, rice soils<br />
have considerably lower values o f a than soil minerals but considerably higher values<br />
than those o f organic matter, water, <strong>and</strong> air. In rice culture, the ponded water will<br />
have a low value o f a , which results in damped rates o f change in temperature of<br />
the profile. Therm al diffusivity increases rapidly with increases in in the dry soil<br />
range, typically from 0 to 0.2 mVm^ (Figure 3.3.2). From approximately 0.2 m7m^<br />
(depending on the soil texture, buUc density, etc.) to saturation, changes in a are small<br />
(de Vries, 1975; Scott, 2000). This is because k increases rapidly at first when water<br />
m
Rke Soils; Physical <strong>and</strong> Chemical Characteristics ond Behavior 315<br />
molecules surround soil particles <strong>and</strong> increase the amount o f contact between the<br />
solid particles. At that time, the increase in k is greater than the increase in thus<br />
the rapid initial increase in a. W ith greater quantities o f water entering the soil, k<br />
<strong>and</strong> Ct, tend to increase at the same rate, which explains why a remains more or less<br />
constant with increasing 6. Renaud (2000) solved equation (17) for a Calloway silt<br />
loam cropped to rice using a constant or over periods o f several days, with 9^ values<br />
ranging from 0.2 to 0.45 mVm^. H aul« et al. (1971) also concluded from their soil heat<br />
transfer simulations that as long as reasonable values o f a were selected, reasonable<br />
estimates o f T could be obtained.<br />
Chemical Properties<br />
<strong>Rice</strong> is grown on many soils that differ widely in their chemical characteristics. The<br />
suitability o f a soil for producing rice is determined more by soil physical properties<br />
(e.g., ability to hold a flood) than it is by the chemical properties o f the soil. Thus it<br />
is not possible to give the chemical characteristics o f a “typical” rice soil. However,<br />
submergence o f virtually aU soils brings about tlie same series o f profound chemical<br />
changes, regardless o f the soil’s chemical properties in the oxidized state. The focus<br />
o f this section o f the chapter, then, is on the changes in soil chemical properties that<br />
occur as a result o f soil submergence.<br />
Many chemical changes occur as a result of soil submergence, but the great bulk o f<br />
these can be discussed within the context o f only four chemical properties: redox status,<br />
pH, electrical conductivity, <strong>and</strong> chemical com position o f the soil solution. Prior<br />
to discussing how submergence alters these properties, some background inform ation<br />
on each o f the properties is presented.<br />
Oxidation-Reduction Status<br />
O f all the soil properties that are affected by submergence, none is more im portant<br />
than the oxidation-reduction (or redox) status. It is conceptually useful to think<br />
o f soil redox status as referring to the abundance o f free electrons in a soil. Under<br />
well-aerated (oxidizing) conditions, oxygen is tlie ultimate acceptor o f electrons ± a t<br />
are produced by microbial oxidation o f carbon (C) in organic compounds (i.e., the<br />
oxidation o f organic C is coupled with, or accompanied by, the reduction o f molecular<br />
oxygen). W hen a soil is flooded, the supply o f molecular oxygen (O 2) to the soil is<br />
reduced greatly because the rate at which O 2 diffuses into the soil profile through the<br />
overlying floodwaters is m uch lower than the rate at which O 2 diffuses into unsaturated<br />
soil. Because the rate at which O2 is consumed through aerobic respiration<br />
usually is large compared to the rate at which it can be supplied to saturated soil,<br />
anaerobic conditions usually develop in soil following flooding.<br />
If an adequate supply o f organic carbon exists, bacteria that are capable o f using<br />
electron acceptors other than oxygen proliferate in anaerobic soü. The respirational<br />
activity o f these anaerobic microorganisms effectively leads to an increase in electron<br />
“activity” in the soil. This results in the reduction o f previously oxidized forms o f<br />
redox active elements such as nitrogen (N ), manganese (M n), iron (Fe), <strong>and</strong> sulfur<br />
(S). A soil is said to be in a reduced condition when it contains significant quantities<br />
o f the reduced forms o f these <strong>and</strong> other elements.
316 Production<br />
Historically, soil redox status was described quantitatively by the redox potential,<br />
Eh. Inserting a platinum (Pt) electrode into the soil <strong>and</strong> connecting both it <strong>and</strong> a<br />
suitable reference electrode to a voltmeter makes a soil redox potential measurement.<br />
In the case o f submerged soils, the reference electrode need only be dipped into the<br />
floodwaters in order to complete the circuit. O nce the electrode has been allowed to<br />
equilibrate, the soil Eh [in volts (V) or millivolts (m V)] is determined by subtracting<br />
the potential o f the reference electrode from the reading displayed on the voltmeter.<br />
Patrick et al, (1996) described the construction, calibration, installation, <strong>and</strong> use of<br />
P t electrodes in detail.<br />
Today, the quantitative description o f soil redox status usually involves p £ , a<br />
dimensionless quantity that is defined formally as the negative com m on logarithm<br />
o f the free-electron activity [i.e„ p £ = — log(e~)]. In practice, it is the Eh value of<br />
a soil that is actually measured with a P t electrode, <strong>and</strong> p £ is then calculated using<br />
the equation that relates the two quantities: pE ~ Eh{mV)/59. Soil pE values range<br />
from + 1 3 (highly oxidized) to —6 (highly reduced). Soils having a p £ value above<br />
+ 7 (at pH 7) are defined as oxic soi/s, while soils having a p E value below + 2 (at pH<br />
7) are defined as anoxic soils, Soils with p £ values between + 2 <strong>and</strong> + 7 (at pH 7) are<br />
classified as suboxic soils.<br />
The need to specify the pH value at which a pE value is measured (as in tlie<br />
paragraph above) emphasizes the fact that p £ <strong>and</strong> pH are not independent o f one<br />
another, This can m ost readily be shown by considering a generalized reduction halfreaction:<br />
xAox + yH “'' + e zA,ed + H2O (18)<br />
where A is some redox active chemical species, the x, y , <strong>and</strong> z are stoichiom etric coefficients,<br />
<strong>and</strong> ox <strong>and</strong> red denote the oxidized <strong>and</strong> reduced forms of a redox-active species,<br />
respectively. Note that protons are consumed in this reduction reaction. Assuming<br />
that the activity of liquid water is one, the equilibrium constant for this half-reaction is<br />
K = (Ao.)^'(H^fye')<br />
(19)<br />
where parentheses denote activities. Taking the logarithm o f both sides o f this equation<br />
<strong>and</strong> rearranging gives<br />
pE — log i t + log<br />
(A.x)-'<br />
(Ar,dY - ypH<br />
(20)<br />
This equation clearly shows that pE <strong>and</strong> pH are not independent o f one another.<br />
It also shows that pE is determined not so much by the activity o f free electrons<br />
in solution (although this may still be a useful conceptual device) as it is by the<br />
relative amounts o f the oxidized <strong>and</strong> reduced form s of redox active chemical species<br />
in solution.<br />
Although equation (20) seems to indicate that a measured soil p £ value may<br />
be used to calculate the activity ratio of the oxidized <strong>and</strong> reduced form s o f a redox-<br />
active element in soils, this is seldom possible in practice. This is because there is not<br />
one but several redox-active elements in soils (e.g., 0> N, M n, Fe, S, C) <strong>and</strong> redox
Ríce Soils; Physical <strong>and</strong> Chemical Characteristics <strong>and</strong> Behavior 317<br />
reactions involving these elements occur in the soil simultaneously. A measured soil<br />
redox potential is therefore not determined by the redox behavior o f a single element<br />
but by the composite behavior o f several elements (i.e., it is a “mixed potential”). Furthermore,<br />
thermodynamic equilibrium between redox couples is seldom achieved in<br />
soil systems because o f inefficient coupling o f oxidation <strong>and</strong> reduction half-reactions.<br />
Thus a measured soil redox potential is actually a nonequilibrium mixed potential<br />
which must be interpreted <strong>and</strong> used with caution (Bohn, 1968,1971; Bartlett, 1999).<br />
pH<br />
Soil pH is often referred to as the master variable in soil chemistry because o f tlie profound<br />
impact that it has on so many other soil properties. For example, the solubility<br />
o f minerals in the soil, the surface charge properties (i.e., CEC <strong>and</strong> AEG) o f variable-<br />
charge minerals such as goethite, <strong>and</strong> the amount o f biological activity in soils are all<br />
affected by soil pH.<br />
Soil pH is a quantitative measure o f the soil reaction (acidity or alkalinity) <strong>and</strong> is<br />
defined as the negative logarithm o f the hydronium ion activity; pH = — log(Fl3 0 ^),<br />
where parentheses denote activity. Although it is com m on to see this definition written<br />
in the abbreviated form pH = ~ logfH"^), it is im portant to realize that protons<br />
in aqueous solution are always hydrated (i.e., they exist as the hydronium ion, which<br />
is usually denoted by the formula<br />
It is also im portant to recall that a soil pH<br />
measurement, whether it be made using dyes or a pH electrode (see below), measures<br />
only the active pool o f soil acidity. Such measurements give no indication o f the quantity<br />
o f acidity that resides in the two other pools o f acidity in soils, the exchangeable<br />
(also known as salt-replaceable) <strong>and</strong> residual pools. Thus soil pH measurements give<br />
no indication of soil buffer capacity, because the buffer capacity is determined by the<br />
am ount o f acidity in the two latter pools.<br />
Soil pH is com monly measured potentiometrically, although other methods (e.g.,<br />
pH-sensitive dyes) are available. In the potentiom etric method, the sensing element o f<br />
a hydronium ion-selective electrode <strong>and</strong> a suitable reference electrode are immersed<br />
in an aqueous suspension o f soil (Bohn, 1968). W hen connected to an appropriately<br />
calibrated potentiom eter (pH m eter), the pH o f the soil suspension can be read directly<br />
from the meter. The reading obtained in this way is influenced by a number<br />
o f factors, such as stirring, the placement o f the electrodes relative to the sedim ent-<br />
solution interface, <strong>and</strong> die time allowed for equilibration. Regardless o f the exact<br />
protocol followed, it is im portant that the same protocol be followed for all samples.<br />
The pH o f flooded rice soils can be measured potentiometrically in situ using long<br />
electrodes that allow the sensing element to be placed in the mud beneath the over-<br />
lying floodwaters. Soil pH varies spatially <strong>and</strong> temporaEy in all soils, but especially in<br />
soils used for rice <strong>production</strong>. The reasons for this are discussed below.<br />
Elettricfll Conductivity<br />
The electrical conductivity^ (EC) o f a solution is defined as the quantity of electricity<br />
transferred across electrodes o f unit area immersed in the solution per unit potential<br />
gradient per unit time. It is thus the reciprocal o f the solution resistivity. Because the<br />
amount o f electricity that a solution can conduct per unit tim e is proportional to<br />
the concentration o f ions in the solution, the EC o f a soil solution is an indication o f
318 Production<br />
m<br />
PiJ ■' ■<br />
m ^p<br />
■I<br />
Lii<br />
i-i<br />
the total quantity of soluble salts in a soil {i.e., it is a measure o f soil salinity). Empirical<br />
equations have been developed that relate either total dissolved salts or solution ionic<br />
strength to EC (U.S. Salinity Laboratory Staff, 1954; Sposito, 1988).<br />
The st<strong>and</strong>ard laboratory method for determination o f soil EC, known as the saturated<br />
paste extract method, involves preparation o f a saturated soil paste, extraction<br />
o f soil solution from the paste, <strong>and</strong> measurement o f the EC o f the extracted solution<br />
(U.S. Salinity Laboratory Staff, 1954). EoUowing an equilibration time o f from 8 to<br />
24 hours, the soil solution can be extracted from the paste using a variety o f methods,<br />
which are based on the application of either pressure or suction to the paste. The<br />
EC of the resulting solution is then determined using one o f several commercially<br />
available instruments. Unless automatic temperature compensation is a feature of<br />
the instrum ent being used, it is also im portant to measure the temperature o f the<br />
test solution, because EC is a function o f temperature. St<strong>and</strong>ard solutions having<br />
kirown values o f EC may be used to ensure that the conductivity cell <strong>and</strong> meter are<br />
functioning properly.<br />
The SI unit o f EC is the dedsiemens per meter (dS/m), but the non -Sl miUimho<br />
per centimeter (mpiho/cm) is still frequently used (1 dS/m = 1 mmho/cm). The<br />
saturated paste extract EC o f soils varies widely, but a typical range would be 0.1 to 10<br />
dS/ra, witli 4 dS/m traditionally being considered the boundary between nonsaline<br />
<strong>and</strong> saline soils.<br />
Alternatives to the saturated paste method generally involve the preparation of<br />
an aqueous soil suspension having a wider soil/solution ratio than a paste. Using a<br />
soil/solution ratio o f 1:2, 1:5, or 1:10 offers clear advantages over the use o f a paste<br />
when large numbers of soil EC measurements need to be made rapidly, such as in a<br />
soil testing laboratory. Because measured values o f soil EC are highly dependent on<br />
the soil/solution ratio used, it is im portant that any presentation o f soil EC data be<br />
accompanied by a detailed description o f the protocol used in making the measurements.<br />
In the case o f submerged soils, solution for EC measurement can be obtained<br />
directly from the saturated soE. However, both the sample o f saturated soil <strong>and</strong> the<br />
solution extracted must be protected from exposure to atmospheric oxygen. Procedures<br />
designed to minimize exposure to oxygen during sampling, extraction, <strong>and</strong> EC<br />
measurement are available (Hesslein, 1976; M oore et al., 1998).<br />
Chemical Composition of the Soli Soiution<br />
Soil solution is defined as soil water along with the gases <strong>and</strong> solids dissolved in it. The<br />
composition o f the soil solution can be characterized either in terms o f total analytical<br />
concentrations o f elements or in terms of the activities o f all aqueous species (free<br />
metals, free lig<strong>and</strong>s, <strong>and</strong> m etal-lig<strong>and</strong> complexes) present. It is accepted generally<br />
that the aqueous species activity approach provides a much more useful description<br />
of the chemistries of natural water samples. Because it is currently either analytically<br />
impossible or simply impractical to determine the activities (or concentrations) of<br />
all chemical species present in a solution experimentally, computer programs such as<br />
M INTEQ (Allison et a l, 1991) or GEOCHEM (Sposito <strong>and</strong>M attigod, 1980) are used<br />
to calculate the equilibrium activities o f all chemical species in solution, including free<br />
metals, free lig<strong>and</strong>s, <strong>and</strong> aU m etal-lig<strong>and</strong> complexes. To model soil solution chemistry<br />
accurately in this way, these thermodynamic equilibrium models require input such as
<strong>Rice</strong> Soils: Physical <strong>and</strong> Chemical Characteristics <strong>and</strong> Behovior 319<br />
soil solution temperature <strong>and</strong> pH, the partial pressures of any reactive gases (e.g., CO2)<br />
with which the solution may be in equilibrium, <strong>and</strong> tlie total analytical concentrations<br />
o f all metals <strong>and</strong> lig<strong>and</strong>s (including naturally occurring organic lig<strong>and</strong>s) in solution.<br />
M ost of these programs also allow the model system’s redox potential to be specified,<br />
which allows them to be used to speciate the soil solutions o f submerged soils,<br />
Soil solution can be obtained from well-aerated soils using the saturated paste extract<br />
procedure described previously. In the case o f submerged soils, soil solution can<br />
be obtained directly from the saturated soil as it is found in the field (Ponnaraperuma,<br />
1972). As noted previously, care must be taken to minimize exposure o f the solution<br />
to oxygen to avoid reoxidation o f reduced chemical species. A number o f innovative<br />
techniques exist for in situ soil solution sampling o f submerged (i.e,, reduced) soils<br />
(Hesslein, 1976; M oore et al., 1998).<br />
SEASONAL BEHAVIOR OF PHYSICAL AND CHEMICAL PROPERTIES<br />
IN RICE FIELDS<br />
In this section we present the behavior o f the soil physical <strong>and</strong> chemical properties in<br />
the field during the rice-growing season. Emphasis is placed on the magnitude o f the<br />
changes in these properties.<br />
Physical Properties<br />
H/draulit Properties<br />
In Arkansas, Alfisols planted to rice tend to have a higher Ksai value in the surface horizon<br />
than deeper in the profile. This can be attributed to (1) to coarser texture over fine<br />
texture, (2) to an increase in swelling clay content in the lower portion o f the profile,<br />
(3) to an increase in Na concentration in the lower portion o f the profile, <strong>and</strong>/or (4) to<br />
a water transport-restricting horizon such as a tillage pan near the surface <strong>and</strong>/or a<br />
fragipan located deeper within the profile. Examples o f Alfisols where extensive rice<br />
is grown include the DeW itt silt loam, which is similar to tlie Crowley silt loam in<br />
Louisiana, <strong>and</strong> the Calloway silt loam. DeW itt soils have a silt loam A horizon over a<br />
clayey B horizon. Calloway soils have a silt loam texture throughout the profile <strong>and</strong> a<br />
fragipan at about the 0.5 m depth. In most locations both soils also contain a traffic<br />
pan formed from extensive disking <strong>and</strong> traffic from tractors <strong>and</strong> harvesting combines.<br />
Vertisols in Ai'kansas planted to rice tend to have high clay contents throughout<br />
the profile with mostly smectitic or mixed clay mineralogy. These soils tend to have<br />
high shrink-swell capacity <strong>and</strong> a low<br />
value when wet. Example soils found in<br />
eastern Arkansas include the Sharkey clays <strong>and</strong> similar clayey soils. These soils tend<br />
to have a clay or clay loam texture throughout a deep profile.<br />
Water Infiltration <strong>and</strong> Redistribution<br />
Volumetric water content was monitored at different depths o f a Calloway silt loam<br />
over the entire cropping season in 1998 on a private farm using tim e-dom ain reflectometry<br />
(Renaud, 2000). The range o f 0,, was larger toward the soil surface than
320 Producfion<br />
below the plow pan (Figure 3.3.1). Fluctuations in water content were particularly<br />
pronounced at a depth o f 0.05 m, where wetting <strong>and</strong> drying cycles are noticeable.<br />
Initially, the soil was wetter in the fragipan (0.5 to 0.7 m below the soil surface) than<br />
in soil surface horizons, <strong>and</strong> the effects of drying <strong>and</strong> flooding during the rice-growing<br />
season were m uch less in magnitude than in horizons just above.<br />
A noticeable feature shown in Figure 3.3.1 is that the soil profile does not seem<br />
to reach complete water saturation even during the permanent flood. This is better<br />
visualized in Figure 3.3.2, where the aeration porosity, f„, is plotted vs. tim e during the<br />
year. It is obvious that at 0.05 m the soil reached complete saturation only immediately<br />
after the first flood. Complete saturation was almost reached upon flooding the field<br />
the second time, but after a few days, the /„ at that depth ranged between 0.05 <strong>and</strong><br />
0.1 mVm^. This was probably due to the presence o f entrapped air <strong>and</strong> possibly to<br />
gas <strong>production</strong> <strong>and</strong> exudation of the rice roots, algae, <strong>and</strong> other soil microorganisms.<br />
At the interface between the A pl horizon <strong>and</strong> the plow pan (Ap2 horizon starting at<br />
0.09 m ), aeration porosity was lower during the second flood than at 0.05 m, even<br />
though complete saturation was not reached. Several days after the second flood,<br />
complete saturation was reached in lower parts o f the soil profile.<br />
Soil Thermal Regime<br />
Soil temperature was also monitored at different depths o f the Calloway silt loam<br />
mentioned above. Air <strong>and</strong> soil surface temperatures increased rapidly from April 20<br />
. 0.05 m<br />
.0.09 m<br />
0.14 m<br />
0.26 m<br />
D a y o f Y e a r<br />
lli;<br />
.0,45 m<br />
0,6 m<br />
0.8m<br />
s:-. :i 1.<br />
Day of Year<br />
F igure 3,3.1, Volumetric water contents at several depths during rice <strong>production</strong> grown on a<br />
Calloway silt loam,
Ríce Soils: Physical <strong>and</strong> Chemical Characteristics <strong>and</strong> Behavior 321<br />
Day o f Y ear<br />
Figure 3.3:2.<br />
loam.<br />
Aeration porosity at two depths during rice <strong>production</strong> on a Calloway silt<br />
(D O Y 100, or 3 days after rice seedling emergence) to m id-M ay (approximately D O Y<br />
135), continued to increase at a slower rate until the end o f July (approximately DOY<br />
205), <strong>and</strong> started decreasing slowly until the end o f the experiment on September 19<br />
(D O Y 262). A cold spell from D O Y 154 to 161 affected the soil surface with a sharp<br />
decrease in temperatures during that period (Figure 3,3,3). As expected, seasonal<br />
temperatures in the surface horizons (0.05,0.09, <strong>and</strong> 0.14 m ) behaved similar to those<br />
o f the air <strong>and</strong> the soil surface (Figure 3.3.3). However, daily average soil temperatures<br />
were lower, peaicing at around 30“C toward the end o f May (D O Y 140) at 0.05 m<br />
but remaining in the range 25 to 30“C for m ost o f the season (D O Y 190) (data<br />
not shown).<br />
Observations similar to those above can be made for the subsurface horizons<br />
(0.26, 0.45, 0.6, 0.8, <strong>and</strong> 1 m ). However, maxim um average daily soil temperatures<br />
were reached later in the season (e.g., beginning of July at 0.26 m <strong>and</strong> end o f July at 1<br />
m ) (Figure 3.3.3). Again, the cold spell was noted at all depths monitored even though<br />
soil temperature changes at 1 m were small <strong>and</strong> delayed in time (Figure 3.3.3). Indeed,<br />
while average m inim um daily temperature during the cold speU was reached on DOY<br />
157 at the soil surface, minim um temperatures at 0 .26,0.6, <strong>and</strong> 1 m were reached on<br />
DOY 158, 160, <strong>and</strong> 161, respectively.<br />
During the early stages of rice development, air <strong>and</strong> soil temperatures followed<br />
identical patterns to those o f global solar radiation (Figure 3-.3.4). Diurnal temperature<br />
amplitudes were the highest at the soil surface <strong>and</strong> the surface horizons, decreasing<br />
rapidly with depth. Below the soil surface, maximum soil temperatures were<br />
reached later in the day than at the soil surface, resulting in a phase shift because<br />
heat transfer via conduction is a relatively slow process in soils. Furthermore, hourly<br />
fluctuations in solar radiation did not significantly affect soil temperatures at shallow<br />
depths in the soil profile. Once the permanent flood was established <strong>and</strong> the rice plant<br />
covered most of the soil surface, changes in daily global radiation tended to have a less<br />
pronounced effect on daily soil temperature variations (Figure 3.3.5). Furthermore,<br />
daily soil temperature amplitudes decreased with depth <strong>and</strong> were difficult to distinguish<br />
below the plow pan.
322 Production<br />
» .1<br />
Day of Year<br />
Figure 3.3.3.<br />
loam.<br />
Soil temperatures at several depths during rice <strong>production</strong> on a Calloway silt<br />
III;: ^ i^:<br />
Chemical Properties<br />
OxidoTion-Redutfion Status<br />
Soil pE will decline (i.e., a soil will becom e reduced) following submergence provided<br />
tliat the soil is anaerobic, the soil contains an adequate supply o f organic C, <strong>and</strong><br />
a viable population o f anaerobic bacteria exists in the soil. In an intuitive way, this<br />
decline in p £ can be viewed as resulting from an accumulation o f electrons in the soil<br />
that continue to be generated in the absence o f O 2 via the oxidation o f organic C by<br />
anaerobic soil bacteria. W ith no O2 to accept them, these electrons simply accumulate<br />
in the soil. Eventually, the electron activity increases (<strong>and</strong> the pE value decreases) to a<br />
point where the next m ost reducible species (after O2) begins to accept the electrons.<br />
Wlien the supply o f this reducible species has been exliausted, the electron activity
Ríce Soils; Physical ond Chemical Characteristics <strong>and</strong> Behavior<br />
323<br />
1800 j .<br />
«T" 1600<br />
E 1400<br />
w 1200<br />
C<br />
o 1000 ..<br />
’S 800<br />
600 ..<br />
Li<br />
324 Production<br />
For example, soon after the disappearance o f O 2, certain species o f anaerobic bacteria<br />
(such as the denitrifying genera Pseudomonas <strong>and</strong> Micrococcus) begin to efficiently<br />
couple organic C oxidation to nitrate reduction. In effect, bacteria act as catalysts in<br />
soil redox reactions; without them, these reactions would occur either very slowly or<br />
not at all.<br />
The result o f this bacterially mediated coupling o f an oxidation reaction with<br />
a reduction reaction can be represented chemically by adding an oxidation halfreaction<br />
to a reduction half-reaction. Using one of the denitrification reactions as<br />
an example;<br />
6N O 3- -F 30H+ -h 24e-<br />
-F I 5H 2O<br />
\og(K) = 453.6 (21)<br />
CeHizOfi -F 6H 2O 6CO2 + 24H+ + 24e“<br />
6N O 3- + 6H+ - F 3N 2O + 6CO 2 + 9H 2O<br />
log ( i f ) = 4.8 (22)<br />
lo g (if) = 458.4 (23)<br />
Equation (21) is a reduction half-reaction that represents the reduction o f nitrate to<br />
nitrous oxide, while equation (22) is an oxidation half-reaction that represents the<br />
oxidation of soil organic matter (represented here by glucose) to carbon dioxide <strong>and</strong><br />
water. Equation (23) is equal to the sum of equations (21) <strong>and</strong> (22) <strong>and</strong> represents<br />
the overall redox reaction between nitrate <strong>and</strong> soil organic matter. The fact that equation<br />
(23) does not explicitly include an electron term emphasizes the fact that redox<br />
reactions in soils m ust be coupled (i.e., electrons do not accumulate in soils but,<br />
instead, are instantaneously transferred between two redox active chem ical species). It<br />
is also im portant to remember that despite the large log (fiT) values that are frequently<br />
associated with these overall reactions, they would occur very slowly in soils were it<br />
not for bacteria, because bacteria are capable o f effectively catalyzing these reactions.<br />
To some extent, the order in which inorganic elements undergo reduction in<br />
a submerged soil is controlled by the log (K) values associated with overall redox<br />
reactions such as equation (23). Consider, for example, the log {K) value associated<br />
with the reduction of ferric iron in goethite:<br />
24FeOOH + 48H+ -F CeH^Oe -4^ 24Fe'^ + 6CO 2 + 42H 2O lo g fif) 276.0 (24)<br />
Recalling that the Gibbs free energy change associated with a chemical reaction<br />
is related to the reaction equilibrium constant according to the expression AG —<br />
—RTlnKy where T is temperature <strong>and</strong> R is the gas constant, it is apparent that the<br />
AG values for the reactions in both equations (23) <strong>and</strong> (24) will be less than zero,<br />
indicating that they will both occur spontaneously. However, the much larger lo g (if)<br />
(<strong>and</strong> tlie correspondingly much more negative Gibbs free energy change) for the<br />
denitrification reaction [equation (23)] indicates that nitrate is a better oxidant (i.e.,<br />
more easily reduced) than the ferric iron in goethite. Based strictly on thermodynamic<br />
reasoning, we would predict that the reaction in equation (23) would occur first. Fur-<br />
tlrermore, we would predict that the reaction in equation (24) would not occur until<br />
aU o f the nitrate in the system had been reduced. In practice, the relative magnitudes<br />
of log(/T) values can be used to predict the general order o f reduction o f inorganic<br />
elements in soils, but because o f differences in the efficiencies with which the various<br />
redox reactions are coupled by bacteria, there is considerable overlap in the pJ? ranges<br />
over which the reactions occur. One consequence o f this overlap is the smooth manner
<strong>Rice</strong> Soils: Physical <strong>and</strong> Chemical Characteristics <strong>and</strong> Behavior 325<br />
in which pE declines in a soil as a function o f time following submergence; contrary<br />
to the predictions o f our earlier analysis, such plots do not consist o f a series o f well-<br />
defined plateaus connected by brief, rapid drops in pE. The general order in which<br />
inorganic elements are reduced in soils, <strong>and</strong> the pE ranges over which the reduction<br />
reactions are observed to occur, were summarized by Sposito (1988).<br />
There is a considerable am ount o f variability among soils in terms o f their pE<br />
behavior following submergence. Specifically, there are large differences among both<br />
the initial rates at which the pE values decrease <strong>and</strong> among the final pjE" values<br />
attained after long periods o f submergence. Such differences can be caused by a variety<br />
o f factors, including differences in the availability o f oxidizable organic C compounds<br />
(i.e., differences in soil organic matter content <strong>and</strong> com position), soil temperature<br />
<strong>and</strong> pH, the numbers <strong>and</strong> types o f bacteria in the soil, the rate at which O 2 is being<br />
supplied to the soil, <strong>and</strong> the abundance o f one or more easily reducible chemical<br />
elements in the soil. Very high levels o f soil nitrate, for example, have been shown<br />
to slow the rate o f p £ decrease following submergence, presumably by poLsing the<br />
system in the pE range where nitrate reduction occurs. Similar results have been<br />
reported for soils high in Fe(III) compounds.<br />
After several days o f submergence, a characteristic depth distribution o f pE develops<br />
in most soil profiles. A layer develops near the soil surface that has a considerably<br />
higher pE than the soil deeper in the profile. The thickness o f this oxidized layer<br />
differs from soil to soil <strong>and</strong> is determined prim arily by the difference between the<br />
rate at which O 2 is supplied to the soil by diffusion through the overlying floodwaters<br />
<strong>and</strong> the rate at which O2 is used by aerobic soil organisms. The thickness o f the layer<br />
increases as the rate o f O 2 supply increases relative to the rate o f O2 consumption. The<br />
presence o f this oxidized layer in flooded soils is o f considerable practical importance<br />
with regard to loss o f nitrogen from the soil. Am m onium ions diffusing upward into<br />
this zone from anoxic zones deeper in the profile can be nitrified (i.e., oxidized to<br />
nitrate). If the nitrate subsequently reenters deeper, anoxic regions o f the profile, it is<br />
likely that it will be reduced (i.e., denitrified) to N O 2, N?.0> or N 2 gas <strong>and</strong> lost from<br />
the soil.<br />
pH<br />
Soil pH values generally tend to approach neutrality following submergence. Thus<br />
flooding tends to increase the pH o f acidic soils <strong>and</strong> decrease the pH o f alkaline<br />
soils. The increase in pH o f acidic soils following submergence is caused by the consumption<br />
o f protons during redox reactions. Note that in both equations (23) <strong>and</strong><br />
(24) there is a net loss o f protons during the redox reactions involving the oxidation<br />
o f organic matter <strong>and</strong> the reduction o f nitrate <strong>and</strong> goethite, respectively. Note that<br />
equation (23) also predicts that pE <strong>and</strong> pH will be inversely related to one another.<br />
The rate o f pH increase slows as neutrality is approached <strong>and</strong> the pH finally stabilizes<br />
in the range 6.5 to 7. This is believed to occur because the M nC 03~H20- C 02 <strong>and</strong><br />
FeC03- H 20- C 02 systems tend to buffer the soil in this pH range according to the<br />
theoretical equations pH = 5,9 ~ 0.65 log(pQQ^) <strong>and</strong> pH = 6 . 1 —0.38 log(P(^Q^),<br />
respectively (Ponnamperuma, 1972). However, in m ost flooded soils the solution<br />
activities o f both Mn^^ <strong>and</strong> Fe^^ are much higher than those that would be allowed<br />
by rhodocrosite <strong>and</strong> siderite, respectively. This may indicate that the ferrous carbonate<br />
<strong>and</strong> manganous carbonate minerals in soils are substantially more soluble than
326 Production<br />
rhodocrosite <strong>and</strong> siderite. The decrease in pH o f alkaline soils following submergence<br />
is attributed to the CaC03- H 20- C 02 system, which buffers soil pH according to the<br />
theoretical equation pH = 6,03 — 0.67 lo g lF ^ O j)'<br />
Electrical Conductivity<br />
The electrical conductivity (EC) o f soil solutions typically increases following flooding.<br />
This is due primarily to reductive dissolution o f iron <strong>and</strong> manganese oxides,<br />
which releases not only Fe^'^ <strong>and</strong><br />
to solution, but also other ions, such as phosphate,<br />
which may be adsorbed to the oxide surfaces. Following a rapid increase, the<br />
EC levels off <strong>and</strong> then declines as manganese <strong>and</strong> iron solids such as M nC 03 <strong>and</strong><br />
FeHP04 precipitate.<br />
Chemical Composition of the Soil Solution<br />
The com position o f the soil solution undergoes dramatic changes following submergence,<br />
primarily as a result o f the metabolic activities o f anaerobic bacteria. Once tlie<br />
soil has become anaerobic, nitrate is the first alternate electron acceptor to be utilized,<br />
<strong>and</strong> the concentration o f this ion in soil solution declines rapidly. The manganese<br />
oxides are the next to be reduced, which results in a large increase in solution concentrations<br />
o f Mn^“^, Iron oxides are next to undergo reduction. Because o f the relatively<br />
high concentrations o f iron oxides in m ost soils, reductive dissolution o f iron oxides<br />
releases not only large quantities o f Fe^+ to solution but also substantial quantities of<br />
transition metal cations <strong>and</strong> oxyanions that tend to exist in the adsorbed phase on<br />
the surfaces o f these oxides. For example, the increases in soil solution concentrations<br />
of phosphate that are brought about by flooding are believed to be due primarily<br />
to the reductive dissolution o f phosphated iron oxides (Patrick, 1964; Patrick et al.,<br />
1973). Sulfate reduction to sulfide occurs next, which results not only in decreases in<br />
concentrations o f soil solution sulfate, but in decreases in the concentrations o f ions<br />
such as Fe^ *' <strong>and</strong> which tend to form insoluble sulfide compounds. Finally, under<br />
highly reducing conditions, CO 2 can be reduced to methane (CH 4).<br />
CONCLUDING REMARKS<br />
By far, m ost rice grown in the United States occurs on poorly or somewhat poorly<br />
drained soils in MLRAs 131, 1 3 4 ,150A, <strong>and</strong> 17. Many o f these soils have chromas o f 2<br />
or less, sm ectitic or mixed clay mineralogy, <strong>and</strong> are in the soil orders Alfisols, Vertisols,<br />
Inceptisols, <strong>and</strong> MoUisols. <strong>Rice</strong> soils have physically <strong>and</strong> chemically heterogeneous<br />
profiles. For m ost o f the growing season rice is grown under anaerobic conditions<br />
maintaining a layer o f water on the soil surface. The depth o f the ponded water<br />
layer, which varies but averages about 10 cm, affects the rates o f transport of water,<br />
oxygen, <strong>and</strong> heat into the soil profile. As a result, soil physical properties o f water<br />
content, aeration, porosity, <strong>and</strong> thermal properties vary spatially <strong>and</strong> temporally in<br />
response to changes in climate <strong>and</strong> water management. Changes are also observed in<br />
soil chemical properties. Soil pH tends toward neutral when flooded, P <strong>and</strong> Fe are<br />
more soluble <strong>and</strong> plant available, <strong>and</strong> N is lost by denitrification. As a result, when<br />
rice is grown on submerged soils, the interactions among the soil physical, chemical,
Ríce Soils; Physitat <strong>and</strong> Chemical Charaderislics <strong>and</strong> Behavior 327<br />
<strong>and</strong> biological properties create a dynamic environment around the roots. The rice<br />
plant also contributes to these changes <strong>and</strong> is evolutionarily adapted to the dynamic<br />
soil characteristics associated with an anaerobic soil environment.<br />
REFERENCES<br />
Allen, R. G., M. <strong>Smith</strong>, A. Perrier, <strong>and</strong> L. S. Pereira, 1994. An update for the definition<br />
o f reference évapotranspiration. ICID Bull 43:35-92.<br />
Allison, J. D., D. S. Brown, <strong>and</strong> K. J. Novo-Gradac. 1991. MINTEQA2/PRODEFA2,<br />
a geochemical assessment model for environmental systems. Version 3.00 User's<br />
Manual EPA-600/3-91-021. USEPA, Athens, GA.<br />
Amoozegar, A., <strong>and</strong> A. W. Warrick. 1986. Hydraulic conductivity o f saturated soils:<br />
field methods. In A. Klute (ed.), Methods of Soil Analysis, Pt 1, Physical <strong>and</strong><br />
Mineralogical Methods, 2nd ed. American Society o f Agronomy, Madison, W I,<br />
pp. 735-770.<br />
Arkansas Cooperative Extension Service. 1996. <strong>Rice</strong> Production H<strong>and</strong>book. D ocum ent<br />
M P192. University o f Arkansas, Fayetteville, AR, 90 pp.<br />
Bartlett, R. J. 1999. Characterizing soil-redox behavior. In D. L. Sparks (ed.), Soil<br />
Physical Chemistry, 2nd ed. CRC Press, Boca Raton, FL, pp. 371-397.<br />
Beven, K., <strong>and</strong> P. Germann. 1982. Macropores <strong>and</strong> water flow in soils. Water Resour.<br />
Res. 18(5):1311-1325<br />
Bohn, H. 1968. Electromotive force o f inert electrodes in soil suspensions. Soil Sei.<br />
Soc. Am. Proc. 32:211-215.<br />
Bohn, H. 1971. Redoxpotentials. Soil Sei 112:39-45.<br />
Brown, K. W., F. T . Turner, J. C. Thom as, L. E. Deuel, <strong>and</strong> M. E. Keener. 1978. Water<br />
balance o f flooded rice paddies. Agrk. Water Manag. 1:277-291.<br />
Burman, R. D., P. R. Nixon, J. L. Wright, <strong>and</strong> W. O Pruitt. 1983. Water requirements.<br />
In M , E. Jensen (ed,), Design <strong>and</strong> Operation of Farm Irrigation Systems. ASAE<br />
Monogr, 3. American Society of Agricultural Engineers, St. Joseph, MO, pp. 1 8 9 -<br />
232.<br />
de Vries, D. A. 1975. Heat transfer in soils. In D. A. de Vries <strong>and</strong> N. H. Afgan (eds.).<br />
Heat <strong>and</strong> Mass Transfer in the Biosphere. Scripta, Washington, D C, pp. 5-28.<br />
Doorenbos, J., <strong>and</strong> W. O. Pruitt. 1977. Crop water requirements. FAO Irrigation <strong>and</strong><br />
Drainage Paper No. 24. Food <strong>and</strong> Agriculture Organization, Rome, 144 pp.<br />
Ferguson, J, A. 1970. The effect o f flood depth on environment o f rice plants. Ark.<br />
Farm Res. 19(1 ):3.<br />
Flach, K. W., <strong>and</strong> D. R Slusher. 1978. Soils used for rice culture in the United States.<br />
In Soils <strong>and</strong> <strong>Rice</strong>. International <strong>Rice</strong> Research Institute, Manila, The Philippines.<br />
Glinski, J., <strong>and</strong> W. Stepniewski. 1985. Soil Aeration <strong>and</strong> Its Role for Plants. CRC Press,<br />
Boca Raton, FL.<br />
Hanks, R. J., D, D. Austin, <strong>and</strong> W. T. Ondrechen. 1971. Soil temperature estimation<br />
by numerical method. Soil Scl Soc. Am. Proc. 35:665-667.<br />
Hasegawa, S. 1987. Hydraulic conductivity. In Physical Measurements in Flooded <strong>Rice</strong><br />
Soils: The Japanese Methodologies. International <strong>Rice</strong> Research Institute, Manila,<br />
The Philippines, pp. 23-31.<br />
Hesslein, R. H, 1976. An in situ sampler for close interval pore water studies. Limnol<br />
Oceanogr. 21:912-914.
Prodjcfion<br />
I<br />
■I<br />
J<br />
i : ! I<br />
Howeler, R. H., <strong>and</strong> D. R. Bouldin. 1971. The diffusion <strong>and</strong> consum ption o f oxygen<br />
in submerged soils. Soil Sä, Soc. Am. Proc. 35:202-208.<br />
Klute, A., <strong>and</strong> C. Dirksen. 1986. Hydraulic conductivity <strong>and</strong> dififusivity: laboratory<br />
methods. In A. Klute (ed.), Methods of Soil Analysis, Ft 1, Physical <strong>and</strong>Mineralogical<br />
Methods, 2nd ed, American Society o f Agronomy, Madison, W I, pp. 687-734.<br />
Lourence, R J., <strong>and</strong> W. O. Pruitt. 1971. Energy balance <strong>and</strong> water use o f rice grown in<br />
the Central Valley o f California. Agron. J. 63:827-832.<br />
McCauley, G. N. 1990. Sprinkler vs. flood irrigation in traditional rice <strong>production</strong><br />
regions of southeast Texas. Agron. J. 82:677-683.<br />
Miyazaki, T, 1993. Water Plow In Soils. Marcel Delcker, New York, 296 pp.<br />
Moore, P, A,, Jr„ K. R. Reddy, <strong>and</strong> M . M . Fisher. 1998. Phosphorus flux between<br />
sediment <strong>and</strong> overlying water in Lake Okeechobee, Florida: spatial <strong>and</strong> temporal<br />
variations. /. Environ. Qual 27:1428-1439.<br />
Patrick, W. H., Jr. 1964. Extractable iron <strong>and</strong> phosphorus in a submerged soil at<br />
controlled redox potentials. Trans. 8th Inti Congr. Soil Sei (Bucharest) 66:605-<br />
.609.<br />
Patrick, W. H., Jr., S, Gotoh, <strong>and</strong> B. G. Williams. 1973. Strengite dissolution in flooded<br />
soils <strong>and</strong> sediments. Science (Washington, D.C.) 179:564-565.<br />
Patrick, W. H., Jr., R. P. Gambrell, <strong>and</strong> S. P. Faulkner. 1996. Redox measurements of<br />
soils. In D. L. Sparks (ed.). Methods of Soil Analysis, P t 3, Chemical Methods. Soil<br />
Science Society o f America, Madison, W I, pp. 1255-1274<br />
Phuc, N., K Tanabe, <strong>and</strong> M . Kuroda. 1976. Mathematical analysis on the miscible<br />
displacement <strong>and</strong> diffusion o f dissolved oxygen in the submerged soils. /. Pac.<br />
Agric. Kyushu Univ.<br />
Ponnamperuma, F. N. 1972. The chem istry o f submerged soils. Adv. Agron. 24:29-96.<br />
Renaud, R 2000. Water <strong>and</strong> heat transfer in a soil cropped to rice. Ph.D. dissertation.<br />
University of Arkansas, FayetteviUe, AR.<br />
Renaud, F , J. A. Ferguson, H. D. Scott, <strong>and</strong> D. M. Miller. 2000. Estim ation o f seasonal<br />
rice évapotranspiration. In R. J, Norm an <strong>and</strong> C. A. Beyrouty (eds.), B.R. Wells <strong>Rice</strong><br />
Research Studies, 1999. Arkansas Agricultural Experiment Station, Fayetteville,<br />
AR, pp. 283-293.<br />
Roel, A., J. L. Heilman, <strong>and</strong> G. N. McCauley. 1999. Water use <strong>and</strong> plant response in<br />
two rice irrigation methods. Agric, Water Manag. 39:35-46,<br />
Rosenberg, J. R., B. L. Blad, <strong>and</strong> S. B. Verma. 1983. Microclimate: The Biological Environment.<br />
Wiley, New York, 495 pp.<br />
Scott, H. D. 2000. Soil Physics: Agricultural <strong>and</strong> Environmental Applications. Iowa State<br />
University Press, Ames, I A.<br />
Scott, H. D., J. DeAngulo, M. B. Daniels, <strong>and</strong> L. S, Wood. 1989. Effects o f flood<br />
duration on soybean growth <strong>and</strong> yield. Agron. /, 81:631-636.<br />
Scott, H. D., J. A. Ferguson, L. Hanson, T. Pugitt, <strong>and</strong> E. <strong>Smith</strong>. 1998. Agricultural<br />
Water Management in the Mississippi Delta Region of Arkansas. Res. Bull. 959.<br />
Arkansas Agricultural Experim ent Station, Division o f Agriculture, University of<br />
Arkansas, Fayetteville, AR, 98 pp.<br />
Shih, S. R, G. S. Rahi, <strong>and</strong> D. S. Harrison. 1982. Evapotranspiration studies on rice in<br />
relation to water use efficiency. Trans. ÄSAE 26(5):702-707.<br />
Shuttleworth, W. J. 1993. Evaporation, In D. R, M aidment (ed.), H<strong>and</strong>book of Hydrology.<br />
McGraw-Hill, New York, pp. 4.1-4.53.<br />
Sposito, G. 1988. The Chemistry of Soils, Oxford University Press, New York.
<strong>Rice</strong> Soils: Physical <strong>and</strong> Chemical Choratierisilcs <strong>and</strong> Behavior 329<br />
Sposito, G.> <strong>and</strong> S. V. Mattigod. 1980. GEOCHEM: A Computer Program for the Calculation<br />
o f Chemical Equilibria in Soil Solution <strong>and</strong> Other Natural Water Systems.<br />
Kearny Foundation for Soil Science^ University o f California, Riverside, CA.<br />
SSSA. 1996. Glossary of Soil Science Terms. Soil Science Society o f America, Madison,<br />
W I.<br />
Sys, C. 1985. Evaluation o f the physical environment for rice cultivation. In Soil Physics<br />
<strong>and</strong> <strong>Rice</strong>. International <strong>Rice</strong> Research Institute, Manila, The Philippines, pp. 3 1 -<br />
43.<br />
Tomar, V. S., <strong>and</strong> J. C. O’Toole. 1980a. Water use in lowl<strong>and</strong> rice cultivation in Asia: a<br />
review o f évapotranspiration. Agric. Water Manag. 3:83-106.<br />
Tomar, V. S., <strong>and</strong> J. C. O’Toole. 1980b. Design <strong>and</strong> testing o f a mycrolysimeter for<br />
wetl<strong>and</strong> rice. Agron.}. 72:689-692.<br />
USDA-NRCS, 2000. www. statlab.iastate.edu:8Ö/soUs/osd.<br />
USDA-SCS. 1993. Soil Survey Manual. USDA H<strong>and</strong>book 18, U.S. Departm ent o f<br />
Agriculture, Washington, DC.<br />
U.S. Salinity Laboratory Staff. 1954. Diagnosis <strong>and</strong> Improvement of Saline <strong>and</strong> Alkali<br />
Soils (L, A. Richards, ed.). USDA H<strong>and</strong>book 60. U.S, Departm ent o f Agriculture,<br />
Washington, DC.<br />
van W ijk, W. R., <strong>and</strong> D. A, de Vries. 1963. Physics of the Plant Environment. North-<br />
Holl<strong>and</strong>, Amsterdam.<br />
Wells, B. R., D. Kamputa, R. J. Norman, E. D. Vories, <strong>and</strong> R. Baser. 1991. Fluid fertilizer<br />
management o f furrow irrigated rice. /. Pert. Issues 8(1):14-19.<br />
Yoshida, S, 1979. A simple évapotranspiration model o f a paddy field in tropical Asia.<br />
Soil Sei. PlantNutr.25{l):81"91.
d i o p t e r<br />
3.4<br />
Soil Fertilization <strong>and</strong> Mineral Nutrition<br />
in U.S. Mechanized <strong>Rice</strong> Culture<br />
R ic h a rd J. N o r m a n<br />
Department of Crop, Soil, <strong>and</strong><br />
Errvironmental Sciences<br />
Universili/ofArkonsas<br />
Fayetteville, Arkansas<br />
C h a r le s E. W ils o n , Jr.<br />
Department of Crop, Soil, Soil, <strong>and</strong><br />
Environmental Services<br />
University of Arkansas<br />
Stuttgart, Arkansas<br />
N a t h a n A . S la t o n<br />
DepartmentofCrop, Soil, <strong>and</strong><br />
Environmental Sciences<br />
University of Arkansas<br />
Stuttgart, Arkansas<br />
INTRODUaiON<br />
NITROGEN BEHAVIOR, FERTILIZATION, AND NUTRITION<br />
Nitrogen Forms <strong>and</strong> Behavior in Flooded <strong>Rice</strong> Soils<br />
Nitrogen Nutrition <strong>and</strong> Fertilization Proctices<br />
Nitrogen Fertilizer Sources <strong>and</strong> Placement<br />
Nitrogen Nutrition <strong>and</strong> Fertilizer Application Timing<br />
Nitrogen Fertilization Management Options<br />
Application <strong>and</strong> Management of Early or Preflood Nitrogen Fertilizer<br />
Application <strong>and</strong> Management of Midseason Nitrogen Fertilizer<br />
Application <strong>and</strong> Management of Nitrogen Fertilizer In Alternative Irrigated <strong>Rice</strong><br />
Influences on Nitrogen Fertilizer Rate<br />
PHOSPHORUS BEHAVIOR, FERTILIZATION, AND NUTRITION<br />
Phosphorus Forms <strong>and</strong> Behavior in Flooded <strong>Rice</strong> Soils<br />
Phosphorus Nutrition, Fertilization Practices, <strong>and</strong> Diagnosis of Deficiency<br />
Phosphorus Nutrition<br />
Soil Test Methods for Phosphorus<br />
Phosphorus Fertilization Practices <strong>and</strong> Diagnosis of Deficiency<br />
POTASSIUM BEHAVIOR, NUTRITION, AND FERTILIZATION<br />
Potassium Forms <strong>and</strong> Behavior in Flooded <strong>Rice</strong> Soils<br />
Potassium Nutrition, Fertilization Practices, <strong>and</strong> Diagnosis of Dettciency<br />
SULFUR BEHAVIOR, NUTRITION, AND FERTILIZATION<br />
Sulfur Forms <strong>and</strong> Behavior in Flooded <strong>Rice</strong> Soils<br />
Sulfur Nutrition, Fertilization Practices, <strong>and</strong> Diagnosis of Deficiency<br />
<strong>Rice</strong>; Origin, History, Technology, <strong>and</strong> Production, edited by C. Wayne <strong>Smith</strong><br />
ISBN 0-471-34516“4 © <strong>2003</strong> John Wiley & Sons, Inc.<br />
331
332 Production<br />
MICRONUTRIENT AND OTHER ESSENTIAL ELEMENT BEHAVIOR, NUTRITION, AND FERTILIZATION<br />
Zinc Forms <strong>and</strong> Behavior in Fiooded Rite Soils<br />
Zinc Nutrition, Fertilization Practices, <strong>and</strong> Diagnosis of Deficiency<br />
Iron <strong>and</strong> Manganese Forms <strong>and</strong> Behavior in Flooded <strong>Rice</strong> Soils<br />
Iron <strong>and</strong> Manganese Nutrition, Fertilization Practices, <strong>and</strong> Diagnosis of Deficiency<br />
Silicon Nutrition <strong>and</strong> Fertilization<br />
Other Micronutrient <strong>and</strong> Essential Element Requirements<br />
RICE MANAGEMENT ON SALINE AND ALKALINE SOILS<br />
Saline Soil Management for <strong>Rice</strong> Production<br />
Characterization of Saline Soils <strong>and</strong> Water<br />
Sources of Soluble Salts<br />
Characterization of Irrigation Water Quality<br />
Behavior of Soluble Saits in <strong>Rice</strong> Soils<br />
Effects of Soluble Salts on <strong>Rice</strong> Plant Growth<br />
Stage of Growth<br />
Osmotic Effects<br />
Specific Ion Effects<br />
Management of Saline Soils<br />
Leaching Requirements<br />
Other Management Considerations<br />
Alkaline Soil Management for <strong>Rice</strong> Production<br />
<strong>Rice</strong> Production on Calcareous Soils<br />
<strong>Rice</strong> Production on Sodic Soils<br />
RECLAMATION AND FERTILIZATION OF PRECISION GRADED SOILS<br />
REFERENCES<br />
I :<br />
|j|f"<br />
INTRODUCTION<br />
Nutrient uptake by rice (Oryza sativa L.) has many similarities to that o f upl<strong>and</strong><br />
nioiiocot row crops such as corn {Zea mays L.) <strong>and</strong> wheat {Triticum aestivum L ).<br />
However, the flooded environment in which rice is grown has a profound impact on<br />
nutrient behavior <strong>and</strong> availability in the soil <strong>and</strong> thus on the manner in which we<br />
have to apply fertilizers to optimize nutrient uptake <strong>and</strong> growth. Chapter 3.3 gives<br />
a detailed review o f the impact that flooding has on the depletion o f oxygen (O 2)<br />
in the soil <strong>and</strong> other chemical <strong>and</strong> physical changes that occur in the soil following<br />
flooding that can influence a soil’s productivity. In this chapter we review <strong>and</strong> explain<br />
how the flooded soil, depleted o f O2, influences soil fertilization practices in rice<br />
culture. Flooding a soil can enhance the availability o f im portant nutrients such as<br />
phosphorus (P) in acid soils <strong>and</strong> cations such as potassium (K) but be o f benefit or<br />
detrim ent to nitrogen (N) availability, depending on if the N is the am m onium (NH'I )<br />
or nitrate (NO3 ) form , respectively, when the soil is flooded. The nutrients that are<br />
applied to rice in the largest quantities <strong>and</strong>/or have been shown to be most often<br />
deficient in U.S. soils on which rice is grown wÜl receive the b rant o f our discussion,<br />
A previous review o f nutrient behavior in U.S. rice <strong>production</strong> was written by Patrick<br />
etal. (1985).
Soil Fertilization <strong>and</strong> Minerol Nutrition in U.S. Mechanized <strong>Rice</strong> Culture 333<br />
I4ITR06EN BEHAVIOR, FERTILIZATION, AND NUTRITION<br />
Nitrogen is the nutrient that is applied the m ost frequently <strong>and</strong> in the greatest<br />
amounts in U,S. rice <strong>production</strong>. This is due primarily to the large N requirem ent by<br />
high-yielding rice cultivars to achieve acceptable grain yields in contem porary agriculture.<br />
O ther reasons for the relatively large quantities o f N fertilizer required in U.S.<br />
rice <strong>production</strong> are that ( 1) crop rotations involving rice do not permit accumulation<br />
o f soil N; (2) the many chemical, biochemical, <strong>and</strong> m icrobial transformations o f N in<br />
flooded soil; <strong>and</strong> (3) the degree that the N loss mechanisms operate in flooded soil.<br />
Even under the best management, not all o f the N fertilizer applied will be taken up by<br />
the rice. Some o f the N fertilizer will be immobilized by microbes into the soil organic<br />
fraction or fixed by the clay minerals, with the rest being lost via denitrification,<br />
amm onia (NH3) volatilization, <strong>and</strong>/or leaching within several weeks following application.<br />
M ost of the N in the rice plant at maturity is in the grain, <strong>and</strong> thus removed at<br />
harvest. This results in very little carryover o f fertilizer N or available m ineral N to the<br />
next crop in rotation. Clay-fixed N in soils containing appreciable amounts o f ilHte,<br />
verraiculite, or smectite clay minerals is the only form o f mineral N not readily susceptible<br />
to loss or m icrobial assimilation <strong>and</strong> is also not immediately available for crop<br />
uptake. Because of these aforementioned reasons, substantial amounts o f N have to<br />
be applied each year to almost every rice crop in the United States. Notable exceptions<br />
are when new l<strong>and</strong> is put into rice <strong>production</strong> following pasture or forests, when rice<br />
is grown on organic soils or in ponds used previously for commercial fish <strong>production</strong>,<br />
<strong>and</strong> when rice is grown organically without the aid o f manure or synthetic fertilizers.<br />
Previous reviews on N fertilization in U.S. rice <strong>production</strong> are those o f Patrick (1982),<br />
Wells <strong>and</strong> Turner (1984), Br<strong>and</strong>on <strong>and</strong> Wells (1986), <strong>and</strong> Mikkeisen (1987).<br />
Nitrogen Forms <strong>and</strong> Behavior in Flooded <strong>Rice</strong> Soils<br />
To fully appreciate the current N fertilizer recommendations in the mechanized rice<br />
culture practiced in the United States, one must first know the chemical form s o f N<br />
utilized by the rice plant <strong>and</strong> then gain some underst<strong>and</strong>ing o f the influence that the<br />
flooded environment has on the behavior <strong>and</strong> transform ation o f N, <strong>and</strong> hence on<br />
the N forms that exist in the flooded soil (Figure 3.4.1). The two chemical forms o f<br />
N taken up by the rice plant are NH:f <strong>and</strong> NO^. Although many forms o f N exist<br />
in the soil or can be added to the soil from the atmosphere or as fertilizers, they<br />
must be transformed to NH4 or<br />
to be talcen itp by the rice plant. Am monium<br />
moves through the soil solution to the rice roots mostly by diffusion, whereas NO^,<br />
an anion, moves by mass flow <strong>and</strong> diffusion. The lack o f O 2 in the flooded soil results<br />
in anaerobic conditions that causes NH4 to be stable <strong>and</strong> accumulate <strong>and</strong> N O 3 to<br />
be unstable. The instability o f N O 3 in flooded soil is due to its use in the anaerobic<br />
environment as an electron acceptor for microbes in place o f O 2, <strong>and</strong> subseqitent loss<br />
to the atmosphere via denitrification as N 2. Consequently, rice mostly utilizes NPI4 in<br />
a flooded soil, <strong>and</strong> N fertilizer sources recommended for rice are NH4 or NH4-form ing<br />
N fertilizers.<br />
Conceptually, the rice-w ater-soil system can be divided into three distinct environments:<br />
( 1) the floodwater, ( 2) the oxidized surface soil layer along with the<br />
oxidized zone around the rice roots, <strong>and</strong> (3) the reduced soil layer (Figure 3.4.1). The
Soil Fertilization <strong>and</strong> Mineral Nutrition in U.S. Mechanized <strong>Rice</strong> Culture 335<br />
N behavioral <strong>and</strong> transform ation processes tliat take place in these environments can<br />
be broken down into N processes that result in a net gain, a net loss, or no net gain or<br />
loss o f N from the system.<br />
Processes that result in net N gains to the rice-w ater-soil environment are ( 1) N 2<br />
fixation by cyanobacteria form ing organic N, (2) NH3- <strong>and</strong> NO3-N addition in rainwater,<br />
(3) organic N addition from manure application as well as N contained in plant<br />
residue from the previous crop, <strong>and</strong> (4) NH4- <strong>and</strong> NH3-N supplied from synthetic<br />
fertilizers. O rganic-N sources must be mineralized to NH4-N by bacteria in the water<br />
<strong>and</strong>/or soil in order to be available to the rice plant under flooded conditions.<br />
Cyanobacteria (formerly termed blue-green algae) have been used for some tim e to<br />
supply N to rice in Asian countries. Research in Arkansas with cyanobacteria inoculation<br />
o f soil <strong>and</strong> flood water has shown that the N contribution to rice from this<br />
source is no m ore than 25 kg N/ha. In the highly mechanized rice culture practiced<br />
in the United States, where high yields <strong>and</strong> high-quality rice are essential, 25 kg N/ha<br />
is too minute to be o f practical value. M ost rice cultivars grown in the United States<br />
require application o f N fertilizer in the range 135 to 200 kg N/ha to produce profitable<br />
grain yields. Am monia- <strong>and</strong> NOs-N contained in rainwater have been reported to be<br />
somewhere around 10 kg N/ha per year, although the amount can vary, with urban<br />
areas having slightly m ore than this am ount <strong>and</strong> rural areas less. The residue from<br />
the previous crop can have a considerable influence on the N fertilizer available for<br />
a rice crop, especially when comparing crop residues from a legumeous crop such as<br />
soybean [Glycine m ax (L.) Merr.] <strong>and</strong> a nonlegume crop such as rice. Manures, such<br />
as poultry litter, can be a source o f N as well as other nutrients. However, research<br />
has not proven manures to be a better N som ce than synthetic NH4 fertilizer sources.<br />
There will be m ore discussion later on N sources for rice as well as the utility o f poultry<br />
litter for reclaiming graded or disturbed soils on which rice is grown.<br />
Nitrogen-loss processes have received a considerable am ount o f attention from<br />
researchers in rice because the flooded environm ent <strong>and</strong> the warm climates in which<br />
rice is grown can accentuate these processes. The two m ajor N-loss mechanisms in<br />
the rice-w ater-soil system are denitrification <strong>and</strong> NHs volatilization (Patrick, 1982;<br />
Mfldcelsen, 1987), Other N-loss mechanisms o f practical agronomic significance, but<br />
usually o f less importance in rice, are leaching <strong>and</strong> runoff. Althougli these aforem entioned<br />
N-loss mechanisms are from the soil <strong>and</strong> water, the most recently established<br />
loss mechanism in rice <strong>production</strong> is the volatilization of N H 3 <strong>and</strong> possibly other<br />
gaseous N products from rice foliage (da Silva <strong>and</strong> Stutte, 1981; Norman et al., 1992a).<br />
Nitrogen loss from rice foliage helps to explain at least a portion o f the N loss that is<br />
“unaccounted for” by N balance studies conducted with the isotopic tracer *^N when<br />
sampling was not performed until maturity.<br />
Denitrification is the N-loss mechanism that is the most difficult to measure in<br />
the field <strong>and</strong> is usually determined by differences in N mass balance equations. Due to<br />
the lack o f 0 2 Ín the reduced soil layer o f a flooded soil, the NOs form o f N is used by<br />
soil microbes in place o f O 2 as an electron acceptor <strong>and</strong> is quickly reduced to nitrous<br />
oxide (N2O) or<br />
gases, which are then lost to the atmosphere. Denitrification losses<br />
o f N after flooding can be substantial if the large N fertilizer rate applied at preflood<br />
is applied as N O 3 or is applied as NH4 weeks before flooding <strong>and</strong> allowed to be<br />
transformed to N O 3 via nitrification. Denitrification can compete quite well with the<br />
rice plant for N O 3-N during the vegetative stage, when it can take from 3 to 7 weeks to<br />
reach maxim um fertilizer N uptake, depending on whether the N fertilizer is applied
336 Production<br />
llffií ■i- >■<br />
l E T<br />
at beginning tillering or at seeding, respectively. In water-seed rice, where the rice<br />
plant can take as long as 7 weeks to reach maxim um fertilizer N uptake, denitrification<br />
maybe the m ajor N-loss mechanism. Research o f Patrick <strong>and</strong> Reddy (1976a, 1976b;<br />
Reddy et a l, 1976) established that NH^j'can diffuse upward from the reduced soil to<br />
the oxidized soil layer <strong>and</strong> be nitrified, <strong>and</strong> then the resulting N O 3 diffuse or leach<br />
downward back to the reduced soil <strong>and</strong> be denitrified. This diffusion-nitrification-<br />
denitrification process appears to be rapid enough to be a significant loss mechanism<br />
in water-seeded rice when the N fertilizer is not deep placed, but mixed into the upper<br />
surface soil or applied to the surface soil <strong>and</strong> incorporated shallowly with tlie flood<br />
water. Deep placem ent o f N fertilizer is thus required in water-seeded rice to minimize<br />
this process. The diffusion-nitrification-denitrification process appears to be o f minor<br />
significance in dry-seeded, delayed flood rice culture, because only about 3 weeks is<br />
required by the rice plants to reach maximum uptake o f the early or preflood fertilizer<br />
N application.<br />
The other m ajor N-loss mechanism is am m onia (NH3) volatilization. Ammonia<br />
volatilization losses increase as N H 3 concentrations, soil or flood water pH, <strong>and</strong><br />
temperatures along with wind speeds increase (Mikkelsen et al., 1978). Thus, evaporative<br />
loss conditions can favor N H 3 volatilization losses if the N is located at the soil<br />
surface. Soil cation exchange capacity (CEC) also plays a role in NH3 volatilization<br />
losses, with losses increasing as soil CEC decreases. A soil with a low CEC enables<br />
more o f the NH^in a soil to be in solution <strong>and</strong> vulnerable to this loss mechanism.<br />
Ammonia volatilization losses can be significant if an NHs forming fertilizer, such<br />
as urea [(NHa)2CO ], is applied to a moist soil surface prior to flooding during high<br />
evaporative loss conditions ^nd not incorporated in a few days with the flood water<br />
(> 25 % of the applied N; Table 3.4.1 <strong>and</strong> Figure 3.4.2). Am m onia <strong>and</strong> water have<br />
similar properties <strong>and</strong> a high affinity for each other. Thus, when water is lost from<br />
the soil surfiice, so will be NH3 located at the soU surface. Although soil CEC <strong>and</strong> pH<br />
play a role in NH3 volatilization prior to flooding, they have little effect on floodwater<br />
pH <strong>and</strong> thus little effect on volatilization after flooding. Am monia volatilization from<br />
TA B LE 3.4.1.<br />
In flu e n c e o f S o il IV Ioisture C o n d it io n s a n d N Fe rtilize r A p p lic a tio n T im e P r io r to<br />
F lo o d in g o n N H 3 V o la tiliz a tio n L oss, R ice Fe rtilize r N U p ta k e , a n d <strong>Rice</strong> G r a in Y ie ld "<br />
Application<br />
Time Priot to<br />
Flooding<br />
Soil<br />
mioislure<br />
Fertilizer N Recovery<br />
{ % of applied)<br />
N H 3<br />
Plant N<br />
Grain<br />
Yield<br />
(days)<br />
Conditions<br />
Loss<br />
Uptake<br />
(kg/ha)<br />
10 Mud 30 42 5443<br />
Dry 9 65 6753<br />
5 Mud 22 49 5848<br />
Dry 4 71 7045<br />
0 Mud 16 56 6302<br />
Dry 2 72 7225<br />
Flood 42 28 4193<br />
Source: Data from Norman et al. (1993).<br />
"Means of a 2-Year Study, Urea fertilizer labeled with '^N was applied at a rate of 134 kg N/ha to a DeWitt<br />
silt loam (Typic Albaqualfs) when Lemont rice was beginning to tiller.
Soil Fertilization <strong>and</strong> Mineral Nutrition in U.S. Mechanized <strong>Rice</strong> Culture 337<br />
Dry Soil<br />
• O " Muddy Soil<br />
Flooded soil<br />
5 10 15 20<br />
D a ys After N Fertilizer Application<br />
25<br />
Figure 3.4.2. Accumulative ammonia volnfilizatlon losses when urea-N was<br />
applied to a <strong>and</strong> saturated soil <strong>and</strong> not flooded, <strong>and</strong> when ureo-M was applied<br />
into thefloodwater. (From unpublished doto of R, J. Herman.)<br />
floodwater is related highly to the diurnal fluctuation o f floodwater pH (Mildidsen<br />
et al., 1978) as well as the growth stage <strong>and</strong> rate o f N uptake by tlie rice plant. Flood-<br />
water pH rises during the day <strong>and</strong> declines at night due to carbon dioxide (CO2)<br />
fluctuations in the water from the photosynthetic <strong>and</strong> respiratory activities o f algae<br />
<strong>and</strong> bacteria. Floodwater can exceed a pH of 9 during the day from this process,<br />
which greatly accelerates NH3 volatilization losses (Mikkelsen et al., 1978). Ammonia<br />
volatilization losses can be extensive, > 40% o f applied N, when NFI4 fertilizers are<br />
applied into the floodwater during early rice vegetative growth stages (Table 3.4.1 <strong>and</strong><br />
Figure 3.4.2). <strong>Rice</strong> in the early vegetative stages does not have ample foliage to shade<br />
the sunlight from the floodwater sufficiently to prevent the algae <strong>and</strong> cyanobacteria<br />
from photosynthesizing <strong>and</strong> depleting the floodwater o f CO 2, <strong>and</strong> does not take up N<br />
rapidly enough from the floodwater to compete effectively with this loss mechanism.<br />
N ot until reproductive growth does the rice plant have an adequate root system <strong>and</strong><br />
N uptake rate to effectively acquire N applied into the floodwater (Table 3.4.2) <strong>and</strong><br />
compete with the NH3 volatilization loss mechanism.<br />
Nitrogen leaching through the soil profile is a m inor loss mechanism in rice soils.<br />
M ost rice is grown on soils with low saturated hydraulic conductivity or permeability<br />
to minimize irrigation costs. In addition, NO^" is the mineral form o f N most<br />
susceptible to leaching losses, but due to denitrification in flooded soils, very little<br />
N O 3 leaches deep into the soil profile. A small amount o f rice in the United States<br />
is grown commercially on s<strong>and</strong>y soils that have low CEC <strong>and</strong> high permeability. O n<br />
these s<strong>and</strong>y soils, leaching o f NH4 can possibly be significant. Similarly, N fertilizer<br />
loss in ru noff water from flooded rice fields is a m inor N-loss process. For m ost o f the<br />
season, rice floodwater contains very low amounts o f N due to the soil’s attraction for<br />
NH^, the rice crop’s dem<strong>and</strong> for N, <strong>and</strong> the susceptibility o f N 0 3 to denitrification<br />
<strong>and</strong> NH3 to volatilization. Even immediately after N fertilizer has been applied at<br />
preflood <strong>and</strong> midseason, there is characteristically not high enough N concentrations<br />
in the floodwater to pose a threat to the surrounding environment if runoff occurs
338 Production<br />
TABLE 3.4.2.<br />
Percent Fertilize r N U p ta k e b y th e R ice P la n t at D iffe re n t T im e s a fte r N Fertilizer<br />
W a s A p p lie d "<br />
N<br />
Application<br />
Timing<br />
Sam p lin g Period<br />
(days after application)<br />
Fertilizer N Uptake<br />
{% of applied fertilizer N)<br />
Preflood^ 7 11<br />
14 28<br />
21 63<br />
28 65<br />
Panicle differentiation^ 3 63<br />
7 74<br />
10 79<br />
14 76<br />
Panicle differentiation -t- 14 days' 3 70<br />
7 67<br />
10 76<br />
14 66<br />
Source: Data from Wilson et al. (1989).<br />
"Application times used in the split method.<br />
-labeled urea was applied onto a dry soil surface <strong>and</strong> the flood established the same day. Soil was a<br />
DeWitt silt loam (Typic Albaqualfs).<br />
“^'^N-labeled urea was applied into the floodwater.<br />
l- f !<br />
(M oore et aL, 1992b). Fertilizer N concentrations in the floodwater can be minimized<br />
by application of the early or preflood N fertilizer onto dry soil, <strong>and</strong> not saturated<br />
soU, immediately prior to flooding <strong>and</strong> m ost im portant, not into the floodwater.<br />
Application of the N fertilizer into the floodwater at midseason results in elevated<br />
floodwater N concentrations for only about 3 to 5 days, <strong>and</strong> then it is again usually<br />
not high enough to pose a tlireat to tlie surrounding environment (Turner et al., 1980;<br />
Moore et al., 1992b). However, to achieve maximum fertilizer N uptake <strong>and</strong> minimize<br />
any threat to tlie surrounding environment, it is prudent simply to not allow runoff<br />
from the rice fields during the first week after N fertilizer applications.<br />
The most recently documented N-loss mechanism in rite is N loss from die rice<br />
foliage (Mikkelsen, 1987). It appears that NHamay be lost during photorespiration<br />
in rice. Stutte <strong>and</strong> co-workers (da Silva <strong>and</strong> Stutte, 1981; Stutte <strong>and</strong> da Silva, 1981;<br />
Foster <strong>and</strong> Stutte, 1986) measured this N-loss mechanism directly <strong>and</strong> established<br />
that the N loss from the rice foliage varied between cultivars <strong>and</strong> was climate <strong>and</strong><br />
N-rate sensitive. Because they were working with young rice plants grown in the<br />
greenhouse <strong>and</strong> the N loss measured was small, little attention was given to diis N-<br />
loss mechanism. Furtlier research, conducted in die field, utilizing the isotopic tracer<br />
has determined that there is potential for a sizable am ount o f N (up to 65 kg<br />
N/ha) to be lost from the rice foliage during the late reproductive <strong>and</strong> grain-filling<br />
growth stages <strong>and</strong> that the N loss (1) varies from year to year, (2) increases as the N<br />
rate increases, (3) is cultivar sensitive, <strong>and</strong> (4) appears to be worse during abnormally<br />
hot summers (Norman et al., 1992a; Guindo et al., 1994a,b). The influence o f this<br />
N-loss mechanism on rice grain yields is unclear <strong>and</strong> deserves study. W liat was clear<br />
from the research was the proper tim e to sample the rice plant to accurately determine
Soli Fartilization <strong>and</strong> Mineral Nutrition in U.S. Mechanized liice Culture 339<br />
maximum fertilizer N iiptalce when the<br />
isotopic tracer technique is used. The rice<br />
plant should be sampled at panicle differentiation when evaluating the uptake o f N<br />
applied preplant <strong>and</strong> prefLood <strong>and</strong> no later than 50% heading when evaluating the<br />
uptalce o f N applied at panicle initiation <strong>and</strong> differentiation. If sampling is delayed<br />
until maturity, as has been done in most N balance studies utilizing<br />
to determine<br />
fertilizer N uptake, a large amount o f “unaccounted for” N fertilizer could result when<br />
using this isotopic method <strong>and</strong> be attributed erroneously to N-loss mechanisms from<br />
the soil <strong>and</strong> water (Guindo et aL, 1994a).<br />
Mechanisms in the soil that do not result in a net gain or loss o f N from the system,<br />
but can affect the availability o f N for uptake by the rice plant, are (1) microbial<br />
m ineralization-im m obilization turnover, (2) nitrification, (3) NH^ fixation by clays,<br />
<strong>and</strong> (4) chemical N H 3 fixation by organic matter. Mineralization is the m icrobial<br />
transformation o f organic N to NH4, <strong>and</strong> immobilization is the reverse process, where<br />
mineral N (i.e., NH4 or NO3) is transformed to organic N via microbial assimilation.<br />
Consequently, immobilization is competing with the rice plant for available N. Both<br />
of these processes occur simultaneously in the soil with one often dominating, depending<br />
on the carbon (C)/N ratio o f the crop residue or the am ount o f organic N<br />
present (Gilmour et al., 1998). The addition o f crop residues such as rice or wheat with<br />
wide C/N ratios results in a net immobilization o f N, while residues such as soybean<br />
with narrow C/N ratios result in a net mineralization o f N. Because flooded soils are<br />
m ostly in the reduced state, NH4 is the only inorganic N form involved to any extent<br />
in im m obilization-m ineralization turnover in rice soils, except possibly in the aerobic<br />
layer at the soil surface <strong>and</strong> aerobic area surrounding the rice roots (Patiick, 1982).<br />
M ineralization-im m obilization o f N in flooded soils also differs from well-drained<br />
soils in other ways. Anaerobic decomposition o f organic materials by soil microbes<br />
proceeds at a slower rate, requires less N for decomposition, <strong>and</strong> thus results in less<br />
fertilizer N being involved in this process tlian in aerobic decomposition in drained<br />
soils. Typically, 20 to 30% o f the fertilizer N applied at preplant or preflood <strong>and</strong> 10 to<br />
20% o f the N applied at midseason is recovered in the soil organic fraction <strong>and</strong> not<br />
taken up by the rice crop at st<strong>and</strong>ard N fertilizer rates (Norman et al., 1989; W ilson et<br />
al., 1989; Bufogle et al., 1997c). However, immobilization o f fertilizer N does appear<br />
to lead to a corresponding mineralization o f soil N, <strong>and</strong> the exchange o f N may result<br />
in more or less net N available for rice, depending on the soil, N source, <strong>and</strong> previous<br />
crop (Wescott <strong>and</strong> Mikkelsen, 1985; Kaboneka, 1998).<br />
Nitrification is the m icrobial transformation o f NH4 to NO3 . This results in no<br />
loss or gain o f N from the soil <strong>and</strong> the rice plant can take up either form. Nitrification<br />
can take place only in the presence o f O 2 <strong>and</strong> thus can occur in the soil prior to<br />
flooding, but after flooding only takes place in the floodwater, oxidized surface soil<br />
layer, <strong>and</strong> the oxidized area encompassing the root rhizosphere. Nitrification is not<br />
a desirable process in rice <strong>production</strong> simply because o f the susceptibility o f N O 3 to<br />
denitrification loss in the reduced zone o f the flooded soil.<br />
Am m onium can become fixed in the interlayer space o f 2:1 clay minerals <strong>and</strong><br />
not be readily available for plant uptake. Fixation o f NH4 can take place in soils that<br />
contain appreciable amounts o f the 2:1 clays illite, smectite, or vermiciilite (Nommik<br />
<strong>and</strong> Vahtras, 1982). Fixation by smectite should not be a problem in flooded rice soils<br />
since smectite cannot fix NH4 under moist conditions. Potassium is also susceptible<br />
to fixation by clay <strong>and</strong> the NH4 fixed is actually occupying space formally held by K^.<br />
The amount o f NH4 fixed by 2:1 clays depends on the am ount o f NH4added, the type
340 Production<br />
^<br />
I<br />
of clay, <strong>and</strong> the degree that the NH4 fixation sites are occupied (Nom m ik <strong>and</strong> Vahtras,<br />
1982; Norman et al., 1987; Chen et al., 1989). The am ount o f NH4 fertilizer fixed in<br />
rice soils in the United States <strong>and</strong> the degree to which this process affects N fertilizer<br />
rates <strong>and</strong> N uptake by rice are unknown <strong>and</strong> deserve study. Keerthisinghe et al. (1984)<br />
studied NH4fixation in clayey soils used for rice <strong>production</strong> in the Philippines <strong>and</strong><br />
found that from 5 to 20% o f the NH4 broadcast applied was fixed in these soils. B<strong>and</strong><br />
application o f NH4 or NH3 fertilizers can reduce the amount o f NH4 fixed by clay.<br />
Clay-fixed NH4 is in equilibrium with solution <strong>and</strong> exchangeable NH4 held on the<br />
surfaces o f the clay. W hen the concentration o f solution <strong>and</strong> exchangeable NH4 are<br />
depleted, they will be replenished by the clay-fixed NH4. The dilution effect o f flooding<br />
a soil should facilitate the reversibility o f the fixation reaction <strong>and</strong> the plant availability<br />
o f clay fixed NH4. The rate at which N H 4 fertilizer fixed by clay is released <strong>and</strong> talcen<br />
up by plants varies with the plant species, soil or type o f clay, am ount o f NH4 applied<br />
<strong>and</strong> fixed, soil moisture, <strong>and</strong> soil K status (N om m ik <strong>and</strong> Valitras, 1982; Norman<br />
<strong>and</strong> Gilmour, 1987; Chen et al., 1989). Keerthisinghe et al, (1984) reported that rice<br />
utilized approximately 40% o f the NH4 fertilizer fixed by clay in the soils they studied.<br />
Reports o f crops only taking up 25% or less o f the NH4 fertilizer fixed by clay is not<br />
uncom m on (Norman <strong>and</strong> Gilmour, 1987). The flooded environment in which rice<br />
is grown appears to facilitate the release <strong>and</strong> plant uptake o f NH4 fertilizer fixed by<br />
clay. Besides b<strong>and</strong> application o f N fertilizer, another method to lim it NH4 fixation<br />
by clay is to maintain a large amount o f exchangeable K*' in a NHi-fixing clayey soil<br />
<strong>and</strong>/or to apply K fertilizer prior to the NH4fertilizer. If K is applied simultaneously<br />
or especially after the NH4 fertilizer, the K^' can cause the clay layers to contract, trap<br />
the recently fixed N H J fertili;^er in the clay, <strong>and</strong> make it less plant available.<br />
Nitrogen applied to soil as anhydrous NH3, aqua NH3, or N sources such as urea<br />
that transform to NH3 can chemically react with the soil organic matter <strong>and</strong> form<br />
NHs-organic matter complexes that are chemically stable, highly resistant to microbial<br />
decomposition, <strong>and</strong> thus quite unavailable for plant uptake (N om m ik <strong>and</strong> Vahtras,<br />
1982). Hydrolysis of urea does not raise tlie soil pH to the extent that anhydrous<br />
NHs <strong>and</strong> aqua NH3 do, <strong>and</strong> the result is less fixation o f urea derived N H 3 by organic<br />
matter. W hen the aforementioned N H 3- or NHs-forming fertilizers are applied to a<br />
soil at rates used in rice <strong>production</strong>, NHs fixation by organic matter probably does<br />
not exceed 5% o f the added N (Norman et al., 1987). This is fortunate because very<br />
little o f the chemically fixed NH3 by organic matter is plant available (Norman <strong>and</strong><br />
Gilmour, 1987).<br />
Nitrogen Nutrition <strong>and</strong> Fertilization Practices<br />
Nitrogen fertilization practices employed in U.S. mechanized rice <strong>production</strong> have become<br />
quite st<strong>and</strong>ardized, due to the volume o f research conducted on N fertilization<br />
of rice, the many cooperative research studies conducted by scientists from various<br />
institutions in rice-producing states, the interaction <strong>and</strong> interchange o f ideas between<br />
university, federal, <strong>and</strong> industry scientists at the biannual <strong>Rice</strong> Technical Working<br />
Group Meetings, <strong>and</strong> the excellent dissemination of new research information to<br />
rice producers, consultants, <strong>and</strong> the industry by the Cooperative Extension Services.<br />
Thus most attention will be concentrated on N fertilization practices used in the<br />
various cultural <strong>and</strong> tillage systems rather tlian between states or regions, except when
Soil Fertilization <strong>and</strong> Mineral Nutrition in U.S. Mechanized <strong>Rice</strong> Culture 341<br />
warranted. The four essential components involved in proper N nutrition o f rice are<br />
correct N fertilizer source, rate, application timing, <strong>and</strong> management.<br />
Nitrogen Fertilizer Sources <strong>and</strong> Placement<br />
The large potential for NO3 to be lost via denitrification in the rice-w ater-soil environm<br />
ent necessitates that an NH4- or NH4-form ing N fei'tilizer be applied to rice im <br />
mediately prior to flooding. I f the N fertilizer applied preflood is NH4 or NH4 forming,<br />
the anaerobic environment in the soil following flooding will inhibit nitrification o f<br />
the NH4 fertilizer, in turn minimize denitrification losses, <strong>and</strong> allow the rice crop the<br />
tim e it requires to take up the N fertilizer (Patrick <strong>and</strong> Reddy, 1976a). It is essential that<br />
the NH4 fertilizer be placed at least a few centimeters deep into the reduced zone o f the<br />
soil <strong>and</strong> as much as possible below the oxidized zone at the soil surface (Figure 3.4.1).<br />
Prilled urea [(N H 2)2CO] followed by granular am m onium sulfate [(NH4)2S04]<br />
has seen the most use in dry-seeded, delayed-flood rice, where the N fertilizer has to<br />
be applied aerially, due to the network o f levees previously constructed in the fields.<br />
Urea (45% N) is the N fertilizer o f choice for aerial application because o f its relatively<br />
low cost <strong>and</strong> high N analysis. Urea, however, is an alkaline-forming N fertilizer upon<br />
hydrolysis <strong>and</strong> is first converted to NH3, a gas. Thus it has to be incorporated into the<br />
soil within a few days after application, where it can acquire a atom <strong>and</strong> become<br />
NH4 , a salt. Hydrolysis o f urea in soil requires a few days, after which if it has not<br />
been incorporated into the soil either mechanically or with water can be lost rapidly<br />
via NH3 volatilization. Am monia volatilization losses from urea applied preflood can<br />
be minimized if the urea is applied to a dry soil surface <strong>and</strong> the flood is established<br />
within 5 days after application (Table 3.4.1 <strong>and</strong> Figure 3.4.2). If urea cannot be applied<br />
to a dry soil surface prior to flooding, application to a saturated or muddy soil surface<br />
is an alternative. Urea should not be applied into the floodwater prior to the beginning<br />
o f reproductive growth. Thus urea requires good management.<br />
Ammonium sulfate (21% N) is an excellent N source that has slightly acidic<br />
properties <strong>and</strong> thus is less prone than urea to N H 3 volatilization loss. However, urea<br />
is as effective as am m onium sulfate in supplying N to rice when managed correctly<br />
(Bufogle et al., 1998). Drawbacks of am m onium sulfate are that it currently costs<br />
about twice as much as urea, on a N-weight basis, <strong>and</strong> the lower N analysis o f am <br />
monium sulfate than that o f urea increases aerial application expense, especially with<br />
large rates o f N applied early in the season immediately prior to flooding, termed<br />
preflood. Consequently, the use o f amm onium sulfate is only warranted on high-pH<br />
soils, where NH3 volatilization losses can be substantial if urea is used <strong>and</strong>/or the flood<br />
cannot be established in a timely manner. Frequently, amm onium sulfate is not used<br />
solely as the early N source but is blended with urea to offset some of the costs <strong>and</strong><br />
still possibly gain some o f the beneficial effects o f the am m onium sulfate.<br />
In water-seeded rice, urea, ammonium sulfate, aqua NH3 (20% N), or anhydrous<br />
NHs (82% N) are the NH4 fertilizers of choice. Urea or, to a much lesser extent,<br />
amm onium sulfate is applied to the soil surface prior to flooding <strong>and</strong> seeding <strong>and</strong> then<br />
incorporated either mechanically or most com monly with floodwater in the southern<br />
U.S. rice belt. Wet climatic conditions during the spring in the soutli necessitate the<br />
application o f N fertilizer in the most expeditious manner, <strong>and</strong> granular fertilizers can<br />
be applied rapidly using aircraft. In California’s water-seeded rice culture, where the<br />
time required to apply the N is not as crucial, due to the normally dry climate, wide
342 Production<br />
Si<br />
] i<br />
i f .<br />
1:1<br />
■ :p'<br />
iliiirji<br />
i 1i<br />
S f<br />
S:;i:: ii: .<br />
use o f tlie m ore cost-effective aqua NH3, <strong>and</strong> to a m uch lesser extent, anhydrous NHj,<br />
are knifed into the soil prior to flooding <strong>and</strong> seeding (Hill et al., 1992). To supply the<br />
rice seedlings with N prior to their roots reaching the NH3 b<strong>and</strong>s, an application of<br />
30 to 40 kg N/ha as ammonium sulfate, <strong>and</strong> sometimes urea, is applied immediately<br />
before flooding. Under wet spring conditions in California, urea <strong>and</strong> ammonium<br />
sulfate fertilizers are used in a manner similar to their use in the southern rice belt.<br />
Urea-am m onium nitrate (UAN; 28 to 32% N) solution has seen some use in US.<br />
rice <strong>production</strong>. Because as much as 25% of the N in UAN solution is NO3, UAN has<br />
been recommended for use in rice only as a topdress N fertilizer for applications at<br />
midseason during early reproductive growth when the rice plant takes up the applied<br />
N in a few days (W ilson et al,, 1994).<br />
Soil incorporation o f these aforementioned N fertilizers applied prior to flooding<br />
is achieved in several ways. Urea <strong>and</strong> am m onium sulfate are incorporated into the soil<br />
successfully almost entirely with water in the dry-seeded, delayed-flood system in the<br />
southern rice belt. The technique o f applying granular urea to a dry soil surface just<br />
prior to flooding <strong>and</strong> allowing the floodwater to transport the urea into the soonto-be<br />
reduced zone pf the soil following flooding has worked quite successfully in the<br />
soutli. W hen N fertilizer is applied preplant, mechanical incorporation into the upper<br />
5 to 10 cm o f the surface soil with a field cultivar or fine-toothed harrow is practiced.<br />
In the water-seeded system, best uptake of the preflood N seems to result when<br />
liquid NH3 fertilizers such as Cold-Flo anhydrous NH3 or aqua NH3 are knifed deep,<br />
■5 to 15 cm, into the soil reduced zone. The next best option is to broadcast-apply urea<br />
or ammonium sulfate preflood <strong>and</strong> incorporate mechanically in the upper 10 cm of<br />
the surface sod. The least preferred choices are to use the floodwater to incorporate<br />
the urea or am m onium sulfate applied at preplant or on the muddy soil at peg-down<br />
(BoUich et al., 1998a). This could be due to the floodwater not incorporating the<br />
N fertilizer deep enough into the soil reduced zone to prevent tlie NH4 diffusionnitrification-denitrification<br />
N-loss process (Patrick <strong>and</strong> Reddy 1976b; Reddy et al.,<br />
1976). Although preplant mechanical incorporation is best when urea <strong>and</strong> ammonium<br />
sulfate are used, even this metliod ordinarily does not result in high enough<br />
N uptake by water-seeded rice to eliminate the need for topdress N applications at<br />
midseason in commercial rice fields. Only deep placement o f a N fertilizer into the<br />
soil zone that will become reduced after flooding can achieve those results (Reddy<br />
<strong>and</strong> Patrick, 1977).<br />
The expense of aerially applying N fertilizer to delayed flood rice has stimulated<br />
interest in developing controlled-release N sources, nitrification inhibitors, <strong>and</strong> cultural<br />
practices to enable all of the N fertilizer to be applied in a single preplant soil<br />
incorporation. Controlled-release N sources such as sulfur-coated urea (35 to 40% N)<br />
<strong>and</strong> polyolefin-coated urea (40% N) are prilled urea encased in a protective coating<br />
that decomposes over time. These controlled-release N fertilizers have shown great<br />
promise in university studies as the first consistently successful preplant N fertilizers<br />
(Wells <strong>and</strong> Shodcley, 1974; Wells <strong>and</strong> Norman, 1993; Bollich et al., 2000). Currently,<br />
however, the high cost o f slow-release N sources relative to urea or amm onium sulfate<br />
lim it their use in commercial rice <strong>production</strong>. Nitrification inhibitors such as dicy<strong>and</strong>iamide<br />
proved too inconsistent in inhibiting the nitrification o f preplant-applied<br />
urea in delayed-flood rice (Wells et a l, 1989). Deep placement o f urea applied preplant<br />
limits nitrification <strong>and</strong> decreases N loss, but even with a nitrification inhibitor does<br />
not lim it nitrification enough prior to application o f the delayed flood to produce
Soil Fertilization <strong>and</strong> Mineral Nutrition in U.S. Mechanized <strong>Rice</strong> Cuitare 343<br />
rice grain yields achieved with urea aerially applied in split topdress applications<br />
(Norman et al., 1989). The extra tim e <strong>and</strong> expense o f using a nitrification inhibitor in<br />
conjunction witli deeply placed b<strong>and</strong>s of urea is certainly more tim e consuming than<br />
for aerially applied urea <strong>and</strong> probably similar in application costs. Anhydrous NH3<br />
<strong>and</strong> aqua NH3 are the best suited NH4- or NH4-form ing N sources for deep placement.<br />
Nonetheless, because o f the extra time required to apply these NH3 fertilizers, coupled<br />
with the cost o f the nitrification inhibitor being similar in cost to aerial application<br />
o f urea, anhydrous or aqua NH3 have seen only limited use in dry-seeded, delayedflood<br />
rice.<br />
Nitrogen Nutrition <strong>and</strong> Fertilizer Application Timing<br />
Proper application tim ing is equal in importance in effective N fertilizer management<br />
in rice to choosing the proper N fertilizer source <strong>and</strong> rate. Proper application timing,<br />
however, is m ore controversial due to (1) misunderst<strong>and</strong>ings concerning the N uptake<br />
characteristics o f the rice plant; (2) the shift over the last two decades from tall, leafy,<br />
lodging-susceptible cultivars to higher-yielding lodge-resistant semidwarf <strong>and</strong> short-<br />
statured rice cultivars (hereafter collectively termed stiff-strawed cultivars); (3) the<br />
influence o f soil characteristics oh N fertilizer availability <strong>and</strong> loss; <strong>and</strong> (4) water<br />
management. Numerous application tim ing schemes have been proposed, <strong>and</strong> in<br />
some years many may produce a high-yielding rice crop. However, some methods<br />
are more cost-effective <strong>and</strong> consistent in maximizing fertilizer N uptake, grain yield,<br />
<strong>and</strong> accordingly, the <strong>production</strong> o f a profitable rice crop. One’s ability to discern the<br />
m ost consistent o f the various N fertilizer application timing strategies requires an<br />
underst<strong>and</strong>ing o f the N uptake characteristics o f the rice plant <strong>and</strong> their influence on<br />
growth <strong>and</strong> grain yield.<br />
Uptake o f N by rice follows a sigmoidal growth curve, with total N uptalce nearly<br />
paralleling total dry matter accumulation until heading (Figure 3.4.3) (M oore et al.,<br />
1981; Guindo et al., 1994a,b; Bufogle et al., 1997a). After heading <strong>and</strong> during grain fill.<br />
Total N Uptake<br />
Total Diy Matter Accumulation<br />
0 20 40 60 80 100 120<br />
D ays after <strong>Rice</strong> Em ergence<br />
Figure 3.4.3. Typical season total dry matter <strong>production</strong> <strong>and</strong> total N accumulation<br />
of the rice plant. (From Guindo et al, 1994a.)
344 Production<br />
1:;.;<br />
I !<br />
the total N accumulation by the rice plant slows <strong>and</strong> may increase slightly, cease, or<br />
decrease slightly, depending on the year, cultivar, native N fertility, <strong>and</strong>/or N fertilizer<br />
rate. Total dry matter <strong>production</strong> increases dramatically after heading, due to grain<br />
filling, <strong>and</strong> does not cease until a week or so before maturity. Nitrogen fertilizer<br />
supplies the rice plant with most o f the N from emergence to early reproductive<br />
growth. Native soil N supplies the rice plant with N during the remainder o f the<br />
growth q^'cle. By maturity, there is a similar amount of fertilizer N <strong>and</strong> native soil<br />
N accumulated by tlie rice plant, with 50 to 70% o f the N in the plant residing<br />
in the grain, depending on N fertilizer rate <strong>and</strong> seeding method (Norman et al.,<br />
1992a; Guindo et a l, 1994b; Bufogle et al., 1997b,c). The am ount o f N that has to<br />
be accumulated by the rice plant to achieve maximum grain yield is dependent on<br />
the cultivar, year, soil, <strong>and</strong> geographic location. Typically, the rice cultivars grown in<br />
die United States accumulate 150 to 200 kg N/ha to achieve maxim um grain yields<br />
(Guindo et al., 1994b; Bufogle et al., 1997b; W ilson et al., 1998).<br />
The N concentration in the rice straw declines during the season as the rice<br />
plant foliage increases in size <strong>and</strong> N is translocated from the straw to the developing<br />
panicle (M oore et al„ 1981; Guindo et a l, 1994a,b; Bufogle et al„ 1997c). Figure<br />
3.4.4 illustrates the characteristic decline in rice straw tissue N concentration during<br />
rice plant development. The N concentration in the rice straw is highest at the<br />
beginning tillering stage (3 to 5% N) <strong>and</strong> is influenced by the year, cultivar, <strong>and</strong><br />
most im portant, the native N fertility <strong>and</strong> prefiood N fertilizer rate. Straw tissue N<br />
concentration declines dramatically during the rapid vegetative growth period. By<br />
beginning reproductive growth or panicle initiation <strong>and</strong> differentiation, the N concentration<br />
in the rice straw tissue has declined typically to one-half (1.5 to 2,5% N) of<br />
the N concentration measured at beginning tillering. The decline in N concentration<br />
during the first weeks o f reproductive growth is dependent on whether midseason N<br />
has been applied, <strong>and</strong> thus the decline is slower if N has been applied at midseason.<br />
The decline in straw tissue N concentration accelerates again during late reproductive<br />
growth <strong>and</strong> early heading due to stem, flag leaf, <strong>and</strong> panicle development. <strong>Rice</strong> straw<br />
^Sit-<br />
Figure 3.4,4. Characteristic seasonal N concentration decline in the rice straw<br />
tissue. (From Guindo et oL, 1994a.} .
Soil Fertilization <strong>and</strong> Mineral Nutrition in U.S. Mechanized <strong>Rice</strong> Culture 345<br />
tissue N concentration declines to about 1% during heading <strong>and</strong> flowering. Tissue<br />
N concentration declines slowly from heading until m aturity as N is translocated<br />
from the rice straw to the developing grain. By maturity, the rice straw tissue N<br />
concentration has declined to < 1% N <strong>and</strong> com monly ranges from 0.6 to 0.8% N<br />
by harvest, depending on total N uptake. Rough rice grain typically contains 0.9 to<br />
1.3% N, depending on the year <strong>and</strong> total N uptake, with N concentration increasing<br />
as total N uptake or N fertilizer rate increases (Guindo et al., 1994b). Thus a rice crop<br />
with a total aboveground biomass (grain T straw) of 20,000 kg/ha <strong>and</strong> a grain yield<br />
o f 9000 kg/ha would talce up on average 176 kg N/ha, o f which 99 kg N/ha would be<br />
removed in the grain.<br />
The rice plant usually accumulates very little N during grain fill (Figure 3.4.3).<br />
M ost o f the N in the grain comes from N remobilized <strong>and</strong> translocated from the rice<br />
stems <strong>and</strong> leaves. Consequently, the uptake o f fertilizer N early in the season affects<br />
the uptake o f the native soil N later in the season, the size or dry matter <strong>production</strong><br />
o f the rice plant, the harvest index or sink-source relationships o f the rice plant, <strong>and</strong><br />
thus ultimately, the rice grain yield (Guindo et a l, 1994a,b). If N is not in adequate<br />
supply during active vegetative growth, a stunted plant with a limited num ber of<br />
tiUers, yellowish-green upper leaves, <strong>and</strong> yellow older leaves will be produced. W hen N<br />
deficiency occurs during reproductive growth, the m ost recognizable symptom will<br />
be the noticeable yellowish leaf canopy o f the rice crop <strong>and</strong> to a lesser degree the<br />
subtle stunting. For optimum growth <strong>and</strong> yield, rice requires that N be in adequate<br />
supply in the soil for uptake at the beginning o f the rapid growth (tillering) period.<br />
The number o f panicles per unit area is determined by either st<strong>and</strong> density or tiller<br />
development during vegetative growth <strong>and</strong> is the first yield com ponent determined<br />
(Stansel, 1975). By beginning reproductive growth or at panicle initiation, the m axim<br />
um tiller num ber has been reached. The second yield com ponent, potential number<br />
o f grains per panicle, is determined at the beginning o f early reproductive growth <strong>and</strong><br />
is influenced by the plants’ N nutritional status during this tim e period. Wells <strong>and</strong><br />
Faw (1978) showed that under optim um st<strong>and</strong> densities, increasing N rate did not<br />
significantly increase the num ber o f tillers per unit area. But when st<strong>and</strong> density was<br />
constant, the number o f florets <strong>and</strong> filled grains per panicle increased significantly<br />
with increasing N rate. The third <strong>and</strong> final yield com ponent is grain weight, which<br />
is determined prim arily by genetics <strong>and</strong> influenced only slightly by N nutritional<br />
status. Consequently, N has to be available for uptake during the rapid vegetative rice<br />
growth or tillering period <strong>and</strong> be in proper supply or already taken up by the early<br />
reproductive growth period for maxim um grain <strong>and</strong> milling yields.<br />
The two prim ary application timing methods used in the United States that<br />
consistently result in the highest N uptake as well as grain <strong>and</strong> milling yields o f rice<br />
are the split <strong>and</strong> the optim um preflood (O FF) application methods (Wells et al.,<br />
1989; BoUich et al., 1998c; Norman et al., 1999, 2000; W ilson et al., 2001). The split<br />
method involves application o f 50 to 65% o f the N fertilizer immediately prior to<br />
flooding <strong>and</strong> the remaining 35 to 50% o f the N fertilizer applied at midseason. This<br />
method works very well on tall, leafy cultivars by not supplying too much N fertilizer<br />
during vegetative growth, which can cause reduced yields from mutual shading o f<br />
leaves <strong>and</strong>/or lodging. The tall cultivars take up preflood N fertilizer as efficiently<br />
as the stiff-strawed cultivars even when the large preflood N rates required by stiff-<br />
strawed cultivars is applied (Guindo et al., 1994b; Bufogle et al., 1997b). No m atter<br />
what the plant type, it is critical that the early or preflood N be applied <strong>and</strong> managed
346 Production<br />
correctly. If the preflood N fertilizer is underapplied, grain yield will be reduced<br />
because o f a reduction in the number o f panicles per area, grains per panicle, <strong>and</strong><br />
uptake o f the midseason N. The preflood N should not be oyerapplied because it<br />
can accentuate diseases (Long et al., 1997; Cartwright et al., 2000). The large, early<br />
N fertilizer application is applied prior to flooding <strong>and</strong> seeding in water-seeded rice<br />
<strong>and</strong> prior to flooding at beginning tillering in dry-seeded, delayed-flood rice. The<br />
midseason N fertilizer in the split application method is applied into the floodwater<br />
at panicle initiation or differentiation in one or two applications spaced about 1 week<br />
apart. The split application method should be used to fertilize taU, lodging prone<br />
cultivars <strong>and</strong> to fertilize stiff-strawed rice cultivars when grown on permeable s<strong>and</strong>y<br />
soils, with furrow or flush irrigation, <strong>and</strong> on some clayey soils that require abnormally<br />
high N rates.<br />
Cooperative research among the rice-producing states in the late 1980s with a<br />
nitrification inhibitor indicated that the stiff-strawed cultivars could produce high<br />
grain yields without lodging when N fertilizer was applied in a single early application<br />
in both dry-seeded, delayed-flood <strong>and</strong> water-seeded cultural systems (Wells<br />
et a l, 1989). Research throughout the 1990s confirmed that stiff-strawed rice cultivars<br />
responded at least equally, <strong>and</strong> often better, with less N when the N fertilizer was<br />
applied in a single preflood N application compared to in split applications on aU<br />
silt loam <strong>and</strong> many clayey soils studied (BoUich et a l, 1994, 1998c; Norman et al,<br />
1994b, 1999, 2000). From this research, the O FF N fertilizer application method <strong>and</strong><br />
philosophy were born. Figure 3.4.5 illustrates how the different rice cultivars achieve<br />
a similar or greater grain yield with less N fertilizer when aU the N was applied in<br />
a single preflood or OFF application compared to in split applications. These stiff-<br />
strawed rice cultivars are early-maturing <strong>and</strong> not as prone to mutual shading <strong>and</strong><br />
lodging as their tall, leafy predecessors. The O FF method involves application o f a<br />
large preflood N rate that is ordinarily 34 kg N/ha more than the preflood N rate in<br />
the split application method (Wilson et a l, 2001), <strong>and</strong> then m onitoring the rice plant<br />
on<br />
¿c<br />
s" o<br />
><br />
c<br />
2<br />
o<br />
10000<br />
9 0 0 0<br />
800 0<br />
700 0<br />
6000<br />
5 00 0<br />
4 00 0<br />
3000<br />
1000|<br />
— Cocodrie-Split<br />
•-0-- cocodrEe-OPF<br />
WaUs.Spli(<br />
—V Well8-OPF<br />
~ - m - Priscilla-Spllt<br />
-O '- PrEscllla-OPF p / /<br />
0 50 100 150 200<br />
Total N Fertilizer Rate, kg N ha<br />
1<br />
250<br />
Figure 3.4.5. Groin yield response of three rice cultivars when different rates of N<br />
fertilizer were applied in the optimum preflood (OFF) application method ond split<br />
application method. (From Norman et al, 1999.}
Soil Fertilization <strong>and</strong> Mineral Nutrition in U.S. Mechanized <strong>Rice</strong> Culture 347<br />
at midseason with one o f the following N diagnostic techniques developed for rice:<br />
(1) chlorophyll meter (Turner <strong>and</strong> Jund, 1991, 1994; Wells et al. 1992), (2) Y-leaf N<br />
concentration (Mildcelsen, 1970), <strong>and</strong> (3) rice gauge (Wells et al. 1992; Ntamatungiro<br />
et al., 1999). The OPh method cotrpled with a N diagnostic tool can reduce or eliminate<br />
midseason N fertilizer applications <strong>and</strong> costs when they will not result in greater<br />
grain yield but could cause increased disease <strong>and</strong>/or insect damage. Furthermore,<br />
milling yields o f the stiff-strawed cultivars were highest at the N fertilizer rates that<br />
produced the m axim um grain yields (Jongkaewwattana et al., 1993) <strong>and</strong> thus usually<br />
favors the O PF application method (Norman et al,, 2000).<br />
These stiff-strawed cultivars are short in stature <strong>and</strong> must have adequate amounts<br />
o f N during tillering <strong>and</strong> vegetative growth to produce a rice plant o f sufficient size<br />
to contain the quantity o f carbohydrates <strong>and</strong> nutrients required to achieve their high<br />
genetic yield potential. Nitrogen is stored in the plant stem <strong>and</strong> leaf tissue during<br />
vegetative growth. The stored carbohydrates <strong>and</strong> N is mobilized, translocated, <strong>and</strong><br />
utilized within the plant later in the season during periods o f peak needs, such as<br />
during grain fill (Guindo et al., 1994b). Thus the grain yield potential o f stiff-strawed<br />
cultivars appears to be set by the N taken up <strong>and</strong> resulting growth during the vegetative<br />
period, <strong>and</strong> consequently, by the preflood N fertilizer application. The larger the<br />
preflood N fertilizer application rate or amount o f N taken up during vegetative<br />
growth, the less rice grain yield will be increased by midseason N fertilizer application<br />
(Bollich et al., 1994, 1998c; Norman et al., 1994b, 1999, 2000). Paradoxically, if ffie<br />
preflood N is not taken up in a sufficient amount, resulting in poor plant growth,<br />
midseason N applications are not talcen up efficiently <strong>and</strong> are incapable o f recovering<br />
aU o f the lost yield potential (W ilson et a l, 1998). There is a greater chance o f this<br />
happening with the lower preflood N rate applied in the Split application method than<br />
with the larger preflood N rate used in the O PF N application method. As a general<br />
rule, when more than 67 kg N/ha o f fertilizer is needed at midseason as indicated with<br />
one o f the N diagnostic tools, the yield potential o f stiff-strawed cultivars has been<br />
lost. Therefore, the best N application method for these stiff-strawed rice cultivars is<br />
to apply an optim um am ount o f N fertilizer preflood that is capable o f fulfilling the<br />
rice plants’ N requirements <strong>and</strong> then m onitor the rice plant at midseason with one o f<br />
the N diagnostic techniques to ensure adequate N nutrition.<br />
If die N fertilizer applied at preflood has not been applied at the correct rate<br />
or managed properly, additional N fertilizer will have to be applied at midseason in<br />
order for the rice cultivar to reach its full yield potential. Traditionally, the midseason<br />
N fertilizer has been applied in two applications, with the first applied at panicle<br />
initiation (i.e., beginning internode elongation or green ring) or differentiation (i.e.,<br />
the top internode has 1.5-cm spacing) <strong>and</strong> the second about 1 week later. A study on<br />
the grain yield response o f a semidwarf rice cultivar to midseason N demonstrated<br />
that there was not an exact time to apply midseason N, but a window o f application<br />
existed between panicle initiation <strong>and</strong> differentiation to apply the first midseason N<br />
application (W ilson et al., 1998). In addition, the research found that if 67 kg N/ha<br />
or less was being applied at midseason, the entire midseason N application could<br />
be applied in a single application between panicle initiation <strong>and</strong> differentiation <strong>and</strong><br />
result in similar grain yields achieved when the N was applied in two applications.<br />
Application o f N fertilizer during late reproductive growth, com monly termed<br />
the booting stage, to improve grain <strong>and</strong> milling yields o f rice has been pondered <strong>and</strong><br />
discussed off <strong>and</strong> on for decades with little p roof to confirm or refute the prudence
348 Production<br />
îP'ji'i<br />
I t :<br />
ü '<br />
o f N application at this growth stage. A positive response to N applied at booting<br />
has been attained with both a short-statured <strong>and</strong> semidwarf cultivai (Norman et ah,<br />
2000). This positive response could possibly be due to the inability o f stiff-strawed<br />
rice cultivais to remobilize N adequately from the leaves <strong>and</strong> stems for translocation<br />
to the developing panicle to produce the large yields they are capable o f producing.<br />
However, it could be that the soil at the location at which the study was conducted<br />
lacked adequate native soil N mineralization late in the season to meet the N-uptake<br />
dem<strong>and</strong>s o f the rice. For native N mineralization to be inadequate, it would seem tlrat<br />
either the rice requires more N late in the season in some situations, the root system is<br />
incapable o f adequately scavenging native soil N, <strong>and</strong>/or the native N mineralization<br />
o f our soils has declined over the last few decades due to changes in crop rotations,<br />
more intensive crop management, <strong>and</strong> tillage. During the past 30 years in the southern<br />
rice belt, rice <strong>and</strong> wheat hectarage or involvement in the crop rotation has increased<br />
<strong>and</strong> soybean hectarage has decreased. In light of these questions, research needs to<br />
be directed at N applied at booting, the native N mineralization o f our soils, how N<br />
mineralization is influenced by crop rotations, <strong>and</strong> the ability o f rice to acquire native<br />
soil N late in the season.<br />
There have been a variety of proposed N application methods that involve many<br />
multiple applications of small amounts of N fertilizer. These multiapplication methods,<br />
termed spoon-feeding, can be expensive, due to the added application costs <strong>and</strong><br />
because they do not consistently produce as good N uptake <strong>and</strong> grain yield o f rice<br />
as do the split or OFF N application metliods on the low-permeable soils associated<br />
with rice <strong>production</strong> (Norman et al., 1988, 1994a). Spoon-feeding appears to have<br />
a place only when rice is grown on highly permeable, low-cation-exchange-capacity<br />
s<strong>and</strong>y soils subject to N leaching losses <strong>and</strong> difficulty m aintaining a perm anent flood.<br />
Spoon-feeding works best on s<strong>and</strong>y soils when the NFh fertilizer is applied a few<br />
weeks apart at rates no greater than 35 kg N/ha. The spoon-feeding methods are<br />
usually no more than a variation o f the split method. The most consistent o f these<br />
multiapplication methods involves splitting the preflood N rate <strong>and</strong> applying some<br />
at preflush (three- to four-leaf stage) <strong>and</strong> the remainder at preflood (Table 3,4.3),<br />
followed by midseason applications o f the split metliod. The least efficient ones apply<br />
too much o f the preflood N rate at preplant <strong>and</strong>/or, even worse, apply some into the<br />
floodwater during the vegetative stage, <strong>and</strong> then they generally use the midseason<br />
applications of the split method with perhaps some applied near the heading stage.<br />
The latter multiapplication method greatly increases application costs <strong>and</strong> can result<br />
in greater N fertilizer costs, reduced N uptalce, <strong>and</strong>/or reduced rice grain yields. In<br />
the next section we explain further why N has to be applied only at certain times<br />
to achieve maxim um N uptalœ by rice <strong>and</strong> what management options exist to give<br />
the producer some flexibility in managing the N fertilizer in U.S. mechanized rice<br />
<strong>production</strong>.<br />
Nitrogen Fertilization Management Options<br />
Management o f no other fertilizer nutrient presents a greater challenge to the rice producer<br />
than does the effective management of N fertilizer. Although no other nutrient<br />
requires as much detailed management attention as N fertilizer, no other nutrient<br />
can deliver greater benefits in increased rice grain yields for effective management.<br />
The many N-loss mechanisms in the rice-w ater-soil environment coupled with the
Soil Fertilization <strong>and</strong> Mineral Nutrition in U.S. Mechanized <strong>Rice</strong> Culture 349<br />
T A B LE 3.4.3.<br />
In flu e n c e o f A p p lic a tio n T im e o n E a rly N F e rtilize r U p ta k e a n d G ra in Y ie ld s o f<br />
le m o n t R ice ''<br />
Fertilizer N Application^ (kg N/ho)<br />
Postflood'^<br />
N Fertilizer<br />
Uptake<br />
G rain<br />
Yield<br />
Preplant Preflush' Preflood<br />
1 W e e k 2 W eeks<br />
{ % of ap plied N)<br />
(kg/ha)<br />
34^^ 100 31 9072<br />
34’* 100 50 9400<br />
34 100* 76 9223<br />
67=^ 67 25 8114<br />
67** 67 45 8770<br />
67 67* 77 8240<br />
134’'^ 22 6703<br />
Source; Data ftom Norman cl al. (1994a).<br />
"Means of a 2-year study.<br />
134* 73 9450<br />
100 34* 25 8744<br />
100 34* 30 8921<br />
67 67* 23 7963<br />
67 67* 24 8190<br />
'’Asterisk indicates fertilizer N application monitored with the isotopic tracer ’^N,<br />
'PreJflush treatments applied 1 week prior to hooding.<br />
‘'Postflood treatments applied into die water 1 <strong>and</strong> 2 weeks after flooding.<br />
rapidity at which they can operate punctuate die im portance o f proper N managem<br />
ent; for these N-loss processes can compete quite effectively with the young rice<br />
plant for N fertilizer. Thus the proper N fertilizer management options available in<br />
rice <strong>production</strong> are based on our current underst<strong>and</strong>ing o f N behavior in the flooded<br />
soil environment <strong>and</strong> die N-uptake characteristics o f the rice p lan t<br />
The flooded environment in which rice is grown has such a profound impact on<br />
its N fertilizer uptake efficiency that rice can be the m ost efficient or inefficient of<br />
the agronomic crops in this respect, depending on how the N fertilizer is applied <strong>and</strong><br />
managed. <strong>Rice</strong> is capable o f taking up the N fertilizer consistently with a 65 to 75%<br />
efficiency when the N fertilizer is applied utilizing the split or O FF application m ethods<br />
<strong>and</strong> managed properly (W ilson et al., 1989, 1994; Norman et a l, 1991a; Guindo<br />
et a l, 1994a,b; Bufogle et al., 1997a,c). Generally, N fertilizer applied at midseason is<br />
taken up with slightly higher efficiency than N applied at preflood, but the preflood-<br />
apphed N has a much greater impact on the grain yield o f rice. The N fertilizer uptake<br />
efficiency o f dry-seeded rice is ordinarily similar to slightly better than water-seeded<br />
rice. Nevertheless, the grain yields o f dry- <strong>and</strong> water-seeded rice are quite similar when<br />
the recommended N fertilizer application <strong>and</strong> management methods specified in the<br />
following sections are utilized.<br />
Application <strong>and</strong> Management of Early or Preflood Nitrogen Fertilizer. In dry-seeded,<br />
delayed-flood culture, 65 to 100% o f the total N fertilizer rate is applied at roughly<br />
the four- to five-leaf growth stage (i.e., beginning tillering) onto a dry soil surface<br />
immediately prior to flooding (Bollich et a l, 1994; W ilson et a l, 2001). Once the early<br />
or preflood N fertilizer has been applied, a permanent flood should be established
350 Production<br />
i t<br />
as quickly as possible, preferably within 5 days o f the N application (Table 3.4.1<br />
<strong>and</strong> Figure 3.4.2). The flood incorporates the N fertilizer into the soil, where it is<br />
protected against losses via NHs volatilization <strong>and</strong>/or nitrification-denitrification as<br />
long as a flood is maintained. If the soil does not stay flooded or saturated, the<br />
preflood N fertilizer can nitrify to N O 3 during unflooded periods <strong>and</strong> then be lost<br />
via denitrification after reflooding. Consequently, the flood must be maintained for<br />
at least 3 weeks to give the young rice plant tim e to achieve maxim um uptake o f<br />
preflood-applied N fertilizer (Table 3,4.2). If the flood cannot be established in a<br />
timely manner (i.e., < 5 days), NH3 volatilization losses from urea can be substantial<br />
<strong>and</strong> ammonium sulfate or a mixture o f am m onium sulfate <strong>and</strong> urea should possibly<br />
be applied to minimize these losses. W hen as many as 10 to 14 days are required to<br />
establish a flood, some nitrification o f the N H 4fertilizer can occur <strong>and</strong> be subject to<br />
denitrification losses after flooding. Similarly, urea-am m onium nitrate solution is not<br />
recommended for the preflood N fertilizer application, because as much as 25% o f the<br />
N in UAN solution is N O 3, which will be quicldy lost via denitrification after flooding<br />
(Wilson et al., 1994).<br />
Saturated (muddy) sofl conditions can prohibit rice farmers from applying the<br />
early N onto a dry soil at the four- to five-leaf growth stage. An application window<br />
o f a couple o f weeks past the four- to five-leaf growth stage exists to apply the early<br />
N preflood onto a dry soil surface <strong>and</strong> not reduce N fertilizer uptake or grain yield<br />
(Norman et al., 1992b). Consequently, every effort should be made to apply the<br />
preflood N onto a dry soil surface. However, if wet soil conditions persist <strong>and</strong> the<br />
preflood N cannot be applied during this window onto a dry soil, the preflood N<br />
should be applied onto the saturated or muddy soO <strong>and</strong> flooded as quickly as possible<br />
to minimize NH 3 volatilization N losses (Table 3.4.1 <strong>and</strong> Figure 3.4.2). For best results,<br />
the flood should cover the field in 5 days or less. The large early N rate should not<br />
be applied into the floodwater because the rice plant does not have an extensive<br />
root system at this stage nor a capacity to take up N quickly enough to compete<br />
witli the N-loss processes. Nitrogen fertilizer applied into the floodwater does not<br />
get incorporated into the soil where the young rice roots are located (M oore et al,<br />
1992b) <strong>and</strong> thus is subject to large losses via NH3 volatilization within 7 to 14 days<br />
after application (Table 3.4.1 <strong>and</strong> Figure 3.4,2). Since the preflood N fertilizer applied<br />
at the four- to five-leaf growth stage takes at least 3 weeks to be talcen up by young<br />
rice plants, application o f the preflood N fertilizer into the floodwater will result in<br />
it being taken up very inefficiently. Increasing the N rate will not fully compensate<br />
for inefficient N uptake when N is applied into the floodwater during the vegetative<br />
growth stage. There ai*e times when the rice crop becomes deficient in N during the<br />
vegetative growth stage because of an inadequate rate or mismanagement o f the early<br />
N application, The only feasible N management option available with the currently<br />
procurable N fertilizers to obtain adequate N fertilizer uptake by the rice crop in tlie<br />
middle of the vegetative stage is to drain the flood, apply the N fertilizer onto the soil,<br />
<strong>and</strong> reflood the field as expeditiously as possible.<br />
The large N rates required at the preflood N application time can be difficult<br />
to apply evenly with aircraft <strong>and</strong> an irregular pattern o f rice growth across the field<br />
may result, termed streaking. Streaking can cause significant yield loss due to over<strong>and</strong><br />
underfertilization (Helms et a l, 1987). The best way to avoid streaking is to<br />
use an aerial applicator who knows exactly how to operate aircraft when applying<br />
heavy rates o f fertilizer. All aircraft have a maxim um material flow rate that limits
Soil Fertilization <strong>and</strong> Mineral Nutrition in U.S. Mechanized <strong>Rice</strong> Culture 351<br />
their useful swath width. Large aircraft <strong>and</strong> spreaders may be able to apply heavy<br />
rates o f materials with little or no sacrifice in distribution uniformity. The operative<br />
swath width o f all aircraft decreases as the application or flow rate increases. Double<br />
flying (using one-half the desired application rate <strong>and</strong> flying at one-half the optim um<br />
swath width for that application rate) m aybe used for m ost aircraft applications when<br />
the maxim um practical flow rate is exceeded. Double flying typically results in more<br />
uniform application.<br />
An alternative method o f reducing the chance o f streaking in delayed flood rice<br />
culture is to split the preflood N fertilizer rate into two applications, applying some<br />
prior to flushing the field <strong>and</strong> the remainder immediately prior to flooding (Table<br />
3.4.3) (Norman et al., 1988). Apply about one-third o f the preflood N rate onto<br />
dry soil immediately prior to flushing at the two- to three-leaf growth stage <strong>and</strong> the<br />
remainder onto dry soil just before flooding. The alternative m ethod is recommended<br />
only when the preflood N rate is 100 kgN/ha or more. The preflush N fertilizer applied<br />
a week or two before perm anent flooding is at greater risk o f nitrification followed by<br />
denitrification losses after flooding, <strong>and</strong> therefore is not utilized as efficiently as when<br />
the N is applied immediately before flooding. Application o f a portion o f the preflood<br />
N 1 or 2 weeks after flooding at the fqur- to five-leaf growth stage is discouraged<br />
because o f the large N losses (Tables 3.4.1 <strong>and</strong> 3.4.3). Similarly, preplant incorporation<br />
o f a portion or all o f the preflood N rate to reduce streaking is a poor alternative <strong>and</strong><br />
is not recommended, due to large amounts o f nitrification prior to flooding, followed<br />
by large denitrification losses after flooding (Table 3.4.3). Preplant N fertilizer is<br />
recommended in delayed-flood rice only as a starter fertilizer <strong>and</strong> then no more than<br />
25 to 35 kg N/ha should be applied, because the young rice plant can take up only 20<br />
to 30 kg N/ha by the four- to five-leaf growth stage or tim e o f flooding. Consequently,<br />
starter N fertilizer should not be included in tlie preflood N budget. Nitrogen fertilizer<br />
applied immediately prior to flooding or preflood m ost consistently results in the<br />
greatest N fertilizer use efficiency <strong>and</strong> highest yields. Accordingly, if N fertilizer can<br />
be applied evenly, the large preflood N rate should be applied preflood, not preflush,<br />
<strong>and</strong> under no circumstances applied preplant in delayed-flood rice culture.<br />
Preplant N fertilizer application is not recommended for dry-seeded, delayed-<br />
flood rice culture in m ost situations because there are usually more than adequate<br />
levels o f native soil N available at the beginning o f the season to meet the needs o f the<br />
young rice plant. Additional reasons are that (1) preplant N fertilizer remaining at<br />
the soil surface is subject to am m onia volatilization losses; (2) preplant N fertilizer is<br />
subject to nitrification in the aerobic soil <strong>and</strong> is prone to loss via denitrification from<br />
saturated soils conditions created from heavy rains <strong>and</strong> flushing; (3) any preplant N<br />
fertilizer not taken up by the young rice prior to flooding will be quicldy lost after<br />
flooding via denitrification; (4) preplant N fertilizer can accelerate weed growth <strong>and</strong><br />
make the weeds more difficult to control with herbicides; <strong>and</strong> (5) preplant N fertilizer<br />
can aggravate salinity damage to rice seedlings on soils prone to salinity problems.<br />
There are situations, however, when a preplant starter N fertilizer is beneficial in<br />
obtaining a uniform , adequate st<strong>and</strong> to accelerate rice growth in order to establish<br />
the flood more quicldy or simply to achieve optimum rice growth: (1) <strong>Rice</strong> seeded<br />
early in the season, when the tempertures are cool, can suffer from N deficiency as<br />
well as other nutrient deficiencies that can be minimized with a preplant application<br />
o f a starter fertilizer mixture containing N; (2) rice grown on some clayey soils exhibits<br />
slow growth prior to flooding, <strong>and</strong> a 20 to 30 kg N/ha preplant application<br />
i ,
352 ProdutHon<br />
I".I<br />
P^|:! lii-<br />
W.!-<br />
m<br />
of N fertilizer can promote growth <strong>and</strong> hasten flooding on tliese soils; <strong>and</strong> (3) rice<br />
seeded in fields containing large amounts o f decomposing plant residue from the<br />
previous crop or winter weeds. N o-till dry-seeded, delayed-flood rice is at times sown<br />
on fields with large amounts o f decaying plant residue. Soil microorganisms decomposing<br />
this residue can immobilize the available soil N, <strong>and</strong> a preplant application<br />
o f N fertilizer may be required for optim um growth o f the young rice plants in tins<br />
situation. Typically, by the four- to five-leaf stage, the rice crop contains only 20 to 30<br />
kg N/ha. Consequently, application o f m ore preplant N than this amount will not be<br />
utilized by flooding, but will certainly be nitrified by then <strong>and</strong> susceptible to loss via<br />
denitrification after flooding (Table 3.4.3).<br />
N o-till dry-seeded, delayed-flood rice should have the N managed in the same<br />
manner as conventional-till dry-seeded, delayed-flood rice. Initial research conducted<br />
on silt loam <strong>and</strong> clay soils found no significant difference between the two tillage<br />
systems relative to the N uptake efficiency o f rice (Bollich, 1995; W ilson et al., 1996).<br />
However, if there is a substantial am ount o f plant residue from weeds or a cover crop,<br />
a preplant N fertilizer application <strong>and</strong>/or extra N may have to be added to the preflood<br />
N fertilizer rate to compensate for losses due to NH3 volatilization, <strong>and</strong> N that will be<br />
immobilized to decompose the plant residue. Immobilization o f fertilizer N has been<br />
reported to be twice as m uch in no-till as in plowed soils (<strong>Rice</strong> <strong>and</strong> Sm ith, 1984).<br />
Continuous use o f no-till has been shown to cause soil bulk densities to increase,<br />
which could influence movement o f the preflood N fertilizer into the soil with the<br />
floodwater. More research is required on no-till delayed-flood rice to fully ascertain<br />
if more N is required in this tillage system.<br />
Nitrogen fertilizer management in water-seeded rice involves the same fundamental<br />
principles o f N behavior in flooded soil as does dry-seeded, delayed-flood rice,<br />
but the N placement <strong>and</strong> management methods used to attain efficient uptake o f the<br />
preflood N application are quite different. This is because in dry-seeded, delayed-<br />
flood rice, the preflood N is applied at or around the four- to five-leaf growth stage<br />
<strong>and</strong> takes about 3 weeks to be taken up, whereas in water-seeded rice the N is applied<br />
pieplant, immediately before flooding <strong>and</strong> seeding, <strong>and</strong> takes about 7 weeks to be<br />
utilized by the young rice plants (Bufogle et al., 1997c). Because o f this longer time<br />
period between N application <strong>and</strong> plant uptake in water-seeded rice culture, the preflood<br />
N must be stored for a longer period of time in the soil before the rice crop can<br />
utilize this large am ount of N fertilizer. The longer the preflood N fertilizer remains<br />
in the flooded soil without being utilized by the rice, the more prone it is to being<br />
lost via the NH4 diffiision-nitrification-denitrification N-loss process (Patrick <strong>and</strong><br />
Reddy, 1976b; Reddy et al., 1976). To minimize this loss process in water-seeded rice,<br />
the prefiood N fertilizer must be incorporated deep into the soil that will be reduced<br />
following flooding. The floodwater used to incorporate the preflood N fertilizer in<br />
dry-seeded, delayed-flood rice does not work well in water-seeded rice, because it<br />
will n ot incorporate the N fertilizer deeply enough (Bollich et al., 1998a,b; Norman<br />
et al., 1998).<br />
Deep placement o f the preflood N in water-seeded rice is achieved most successfully<br />
by b<strong>and</strong>ing liquid NHj fertilizers such as Cold-Flo anhydrous NH3 or aqua<br />
ammonia NH3 at a 10- to 15-cm depth. Because it takes a few weeks for the rice roots<br />
to contact this deeply placed N fertilizer, a surface application of a granular fertilizer is<br />
applied at a rate o f about 30 kg N/ha immediately before flooding to supply the young<br />
rice plant with N until it can access the deeply placed N fertilizer. In the southern rice<br />
J
Soil Fertilization <strong>and</strong> Mineral Nutrition in U.S. Mechanized <strong>Rice</strong> Culture 353<br />
belt, granular N fertilizers, urea or ammonium sulfate, are utilized in water-seeded<br />
rice <strong>production</strong>. T he best grain yields o f water-seeded rice have been achieved with<br />
these granular N fertilizers when 50 to 100% o f the N fertilizer rate is broadcast-<br />
applied <strong>and</strong> mechanically incorporated in the upper 10 cm of the surface soil prior<br />
to seeding <strong>and</strong> flooding (Wescott et al., 1986; Bollich et al., 1998a). Because the N<br />
fertilizer is mixed in the surface 10 cm <strong>and</strong> not all deeply placed, this method does<br />
not always appear to reduce the NH4 diffusion-nitrification-denitrification N loss<br />
process enough to result in high-enough N uptake by water-seeded rice to eliminate<br />
tlie need for topdress N applications at midseason.<br />
In water-seeded rice it is very im portant that the early N fertilizer be applied<br />
preplant/preflood, incorporated deep <strong>and</strong> the flood applied immediately <strong>and</strong> m aintained<br />
tliroughout the vegetative growth stage to prevent nitrification-denitrification<br />
N losses. If the soil does not stay flooded or at least saturated, the fertilizer N can nitrify<br />
to N O 3 during the nonflooded periods <strong>and</strong> be lost via denitrification upon reflooding.<br />
Logically, the soil must remain saturated when tlie field is drained for peg-down to<br />
prevent nitrification-denitrification N losses. Do not apply the early N fertilizer onto<br />
the muddy soil at peg-down, because fertilizer N will be lost <strong>and</strong> rice yields will suffer<br />
(Bollich et al., 1998a,b). One advantage o f preplant N application is that the levees<br />
are not constructed yet <strong>and</strong> the preplant/preflood N fertilizer can be applied with<br />
ground equipment, which potentially, may reduce streaking <strong>and</strong> application costs.<br />
One alternative method o f early N fertilizer application <strong>and</strong> management for water-<br />
seeded rice is not to apply any N fertilizer preplant, but to drain the flood from the<br />
field a couple o f weeks prior to the four- to five-leaf growth stage, allow the soil to dry,<br />
<strong>and</strong> then apply <strong>and</strong> manage the N fertilizer as in dry-seeded, delayed-flood rice.<br />
No-till water-seeded rice <strong>production</strong> does not easily lend itself to efficient N m anagement.<br />
Incorporation o f the early N fertilizer with the floodwater does not move<br />
tlie N deep enough into the soil to prevent substantial N loss (Bollich et al., 1998a,b).<br />
Spoon-feeding the rice with biweekly topdress N applications requires m uch more N<br />
fertilizer <strong>and</strong> application costs <strong>and</strong> will probably not produce maxim um rice grain<br />
yields (Norman et al., 1998). The m ost feasible alternative for application o f pre-<br />
plant/prefiood N fertilizer to achieve efficient N management in a no-tiU water-seeded<br />
system is to knife anhydrous or aqua NH3 into the soil to a depth o f 10 to 15 cm prior<br />
to planting. Unless the preplant N fertilizer is knifed deep into the soil, no-tiU waterseeded<br />
rice is not a recommended practice in terms o f maximizing N uptake efficiency,<br />
grain yield, <strong>and</strong> thus profit. Another option is to drain <strong>and</strong> dry the field prior to the<br />
four- to five-leaf or early tillering growth stage, apply early N rate on to a dry soil, <strong>and</strong><br />
then reflood.<br />
Application <strong>and</strong> Management of Midseason Nitrogen Fertilizer. Fertilizer N applied at<br />
midseason, at the proper times <strong>and</strong> in the proper amounts, is talcen up in 3 to 7 days<br />
with 65 to 80% efficiency (Table 3.4,2). By the reproductive growtli stage, the rice<br />
plant has developed an extensive root system near the soil surface <strong>and</strong> has a high N<br />
uptake capacity (Beyrouty et al., 1987,1992; Bufogle et al., 1997a). That, coupled witli<br />
the small N rate, is why the midseason N can be applied into tlie floodwater without<br />
substantial losses via NH3 volatilization. Midseason N rates greater than 67 kg N/ha<br />
should be avoided for several reasons. In general, when rates greater than 67 kg N/ha<br />
are recommended, the rice crop is N deficient <strong>and</strong> yield potential has been reduced<br />
significantly. Even though application o f rates greater than 67 kg N/ha at midseason
354 Production<br />
i<br />
i<br />
; i<br />
may gain back some o f the lost yield, they may also increase lodging <strong>and</strong> disease..<br />
Thus one should apply <strong>and</strong> manage the preflood N so that no more than 67 kg N/ha<br />
is needed at midseason, <strong>and</strong> ideally, no more than 34 kg N/ha should be required.<br />
Midseason N application should be timed according to plant development; that is,<br />
applied at any time from panicle initiation (i.e., beginning internode elongation or<br />
green ring) to differentiation (i.e., the top internode has a 1.5-cm spacing), <strong>and</strong> if a<br />
second application is required, it should be applied about 1 week later (W ilson et al.,<br />
1998). However, when 67 kg N/ha or less N is applied, it can be applied in a single<br />
application during the week or so between panicle initiation <strong>and</strong> differentiation.<br />
Although midseason N fertilizer is taken up by rice very efficiently, it is not always<br />
required to produce top yields (Bollich et al., 1998c; Norman et al., 1999; Ntamatim-<br />
giro et al., 1999), If a sufficient am ount o f N fertilizer has been applied preflood <strong>and</strong><br />
managed correctly, the stiff-strawed rice cultivars grown in the United States require<br />
no midseason N application to reach their full grain <strong>and</strong> milling yield potential on<br />
most soils (BoHich et al., 1994, 1998c; Norman et al., 1994b, 1999, 2000; WUson<br />
et al., 1998). Soil characteristics that influence the uptake o f preflood N or cause the<br />
preflood N rate to h e inadequate, <strong>and</strong> tlius midseason N fertilizer application a re-<br />
quirement, are soil texture, permeability, <strong>and</strong> native soil N fertility. Clayey soils can fix<br />
some o f the preflood N fertilizer <strong>and</strong> make it at least temporarily unavailable for plant<br />
uptake. Clayey soils can also inhibit diffusion o f the preflood NH4 fertilizer to the rice<br />
roots (Trostle et al., 1998). Uptake o f N fertilizer applied at midseason should not be<br />
inhibited as m uch by NH4 diffusion constraints, because at this growth stage the rice<br />
roots are at die soil surface <strong>and</strong> the midseason N is applied into the water. Permeable<br />
s<strong>and</strong>y soils can lose some o f the preflood N fertilizer via leaching before the young rice<br />
plant can utilize the N adequately <strong>and</strong> necessitate that N fertilizer be applied using<br />
the split method. <strong>Rice</strong> grown on soils with low native N fertility <strong>and</strong> mineralization<br />
requires higher N fertilizer rates <strong>and</strong> the need for midseason N applications to provide<br />
a continuous supply o f N that the soil is incapable o f providing.<br />
Several N diagnostic techniques have been developed <strong>and</strong> are used in the United<br />
States to m onitor rice plants at midseason to determine if a N fertilizer application<br />
is warranted at this time. These diagnostic techniques are: (1) chlorophyll or SPAD<br />
meter (Turner <strong>and</strong> fund, 1991, 1994; Wells et al., 1992), (2) Y-leaf N concentration<br />
(Mikkelsen, 1970), <strong>and</strong> (3) plant area or rice gauge (Wells et al., 1992; Ntamatungiro<br />
et al., 1999; W ilson et al., 2001). Each o f these N diagnostic techniques makes the<br />
assumption that aU other nutrients in the rice plant are at an optim um level <strong>and</strong> there<br />
has been no injury from herbicide application. In addition, each method has to be<br />
calibrated for the particular rice cultivar <strong>and</strong> for degree-day thermal unit accumulation<br />
or proper rice growth stage to take the measurement. None o f the N diagnostic<br />
methods work well during vegetative growth or active tillering when the rice plant is<br />
growing vigorously <strong>and</strong> taking up N, except in situations o f gross underfertilization<br />
with N. It is only when the rice plant has depleted the soil of readily available N<br />
<strong>and</strong> slows in growtli that these methods can accurately assess N nutrition or total<br />
N uptake o f the rice plant. W lien preflood N fertilizer has been applied in the general<br />
range recommended for the cultivars <strong>and</strong> managed appropriately, the rice plants require<br />
3 to 4 weeks to maximize uptake o f this application, which is usually around<br />
the panicle initiation or differentiation stage o f growth. Hence these methods are<br />
customarily calibrated for use during early reproductive growth. Additional reasons
Soji Fertilization <strong>and</strong> Mineral Nutrition in U.S. Mechanized <strong>Rice</strong> Culture 355<br />
for calibration at early reproductive growth is that this is the earliest opportunity<br />
to apply N fertilizer into the flood water <strong>and</strong> achieve efficient N uptake by the rice<br />
plant, <strong>and</strong> typically the latest tim e to apply N to the rice crop <strong>and</strong> still have a significant<br />
effect on yield.<br />
The SPAD meter has seen some use in com mercial rice <strong>production</strong> across the<br />
southern rice belt, whereas the Y-leaf N concentration <strong>and</strong> rice gauge methods are<br />
used primarily where they were developed, in California <strong>and</strong> Arkansas, respectively.<br />
Turner <strong>and</strong> Jund (1991) were the first to evaluate the SPAD meter, Wells et al. (1992)<br />
the rice gauge, <strong>and</strong> Miklcelsen (1970) the Y-leaf N concentration method. These scientists<br />
demonstrated that these methods had some capability o f ascertaining the N<br />
requirements o f rice plants at midseason. However, only the study by Ntam atungiro<br />
et al. (1999) in Arkansas has compared <strong>and</strong> evaluated these three N diagnostic<br />
methods in rice. They determined that aU three o f the N diagnostic techniques had<br />
some utility for estimating the total N uptake o f rice plants during the latter stages<br />
o f vegetative growth <strong>and</strong> early reproductive growth, but that the rice gauge was more<br />
sensitive <strong>and</strong> correlated best with total N uptake o f the rice plant at this time. From this<br />
finding it was concluded that the rice gauge was the best of the N diagnostic methods<br />
in determining if <strong>and</strong> how much N fertilizer should be applied to the rice crop at<br />
midseason to maximize grain yields in the southern rice belt. Furthermore, they<br />
determined that coupling the rice gauge measurement with the Y-leaf N concentration<br />
or SPAD meter reading at panicle initiation resulted in a hybrid technique that was<br />
better than any o f the techniques used alone for determining the total N uptake o f the<br />
rice plants, <strong>and</strong> hence the N fertilizer needs o f the rice crop at midseason.<br />
Application <strong>and</strong> Management of Nitrogen Fertilizer in Alternative Irrigated <strong>Rice</strong>. M ost<br />
o f the rice in the United States is grown in the presence o f a permanent flood from<br />
seeding in water-seeded rice or the four- to five-leaf growth stage in dry-seeded rice<br />
until just prior to physiological maturity. However, there are alternative water m anagement<br />
systems utilized to a limited extent in commercial rice <strong>production</strong> in the<br />
United States, <strong>and</strong> some are m ore feasible than others. Sprinkler irrigation (Westeott<br />
<strong>and</strong> Vines, 1986; McCauley, 1990) <strong>and</strong> flush irrigation (Beyrouty et al., 1994; Grigg<br />
et al., 2000) o f rice for the entire season have proven to result routinely in lower grain<br />
yields <strong>and</strong> at times, drastic grain yield reductions, due to the rice plant s inability to<br />
tolerate any kind o f drought stress during the reproductive growth stage. The only<br />
feasible alternative water management systems used commercially for growing rice<br />
that have seen the m ost success in terms of acceptable N fertihzer uptake <strong>and</strong> profitable<br />
rice grain yields are delaying the flood until just before or at panicle initiation<br />
(McCauley <strong>and</strong> Turner, 1979; Norman et a l, 1992b; Beyrouty et a l, 1994; Grigg et al.,<br />
2000) <strong>and</strong> furrow-irrigated rice (Bollich et a l, 1990; Hefner <strong>and</strong> Tracy, 1991a,b; Wells<br />
et a l, 1991; Vories <strong>and</strong> Counce, 1992). Delaying the flood <strong>and</strong> flush-irrigating the<br />
rice until beginning reproductive growtli, followed by establishment of the perma nent<br />
flood, can produce rice grain yields similar to those o f flooded rice, but ordinarily with<br />
less consistency than flooded rice, due to tlie increased susceptibility o f the large early<br />
(preflood) N fertilizer application to losses via N H 3 volatilization <strong>and</strong>/or nitrification-<br />
denitrification. If the flood is delayed for only a few weeks until late vegetative growth,<br />
the early N fertilizer application should be delayed with the flood to achieve com parable<br />
N fertilizer uptake <strong>and</strong> grain yields o f full-season flooded rice (Norman et al..
Produttian<br />
p:-<br />
:r I<br />
1992b). Delaying the flood will delay maturity <strong>and</strong> possibly cause increased herbicide<br />
costs <strong>and</strong> increased susceptibility to rice blast disease {Pyricularia grísea). Furrowirrigated<br />
rice experiences the problems just mentioned but does not appear to suffer<br />
from the inability to replenish soil moisture quickly <strong>and</strong> adequately as is associated<br />
with sprinkler or full-season flush irrigation. Only Vories <strong>and</strong> Counce (1992) directly<br />
compared furrow-irrigated <strong>and</strong> flooded rice. They concluded that furrow-irrigated<br />
rice yielded as m uch as 15% less than flooded rice. Surprisingly, additional N fertilizer<br />
did not enable furrow-irrigated rice to attain the yields o f flooded rice. Similarly,<br />
Hefner <strong>and</strong> Tracey (1991b) concluded furrow-irrigated rice did not require m ore N<br />
than flooded rice. Our loiowledge o f N behavior when the soil undergoes alternate<br />
drying <strong>and</strong> rewetting cycles such as those associated with furrow-irrigated rice suggests<br />
that furrow-irrigated rice is more prone to N loss. Nitrogen fertilizer uptake in<br />
furrow-irrigated rice is also probably less consistent from year to year than in flooded<br />
rice. However, N fertilizer loss in furrow-irrigated rice via NHs volatilization <strong>and</strong>/or<br />
nitriflcation-denitriflcation can apparently be held to a m inim um if the irrigations<br />
are frequent <strong>and</strong> plentiful enough to maintain the soil in a saturated state. Because of<br />
the potential for N loss when rice is grown with furrow irrigation, the split <strong>and</strong> probably<br />
the multiapplication N method should be utilized along with a slightly higher total<br />
N fertilizer rate. Furrow irrigation appears to be a sound alternative cultural system in<br />
the following situations: ( 1) when the water source is limited, (2) on severely sloped<br />
flelds, or (3) on fields with highly permeable s<strong>and</strong>y soils.<br />
PI i;! ‘<br />
Influences on Nitrogen Fertilizer Rate<br />
The N fertilizer rate required to produce the best grain <strong>and</strong> milling yields o f rice<br />
is dependent on the rice cultivar, st<strong>and</strong> density, previous crop, straw management,<br />
soil texture <strong>and</strong> permeability, N fertilizer application method, water management,<br />
soil pH, N fertilizer source, <strong>and</strong> possibly, tillage. The stiff-strawed, early-maturing<br />
short-stature <strong>and</strong> semidwarf rice cultivars are more N responsive than are their taller<br />
predecessors (Roberts et ak, 1993; Norman et a l, 1996; Bufogle et al,, 1997b) <strong>and</strong><br />
generally require 135 to 200 kg N/ha o f N fertilizer to produce maxim um grain yields<br />
(H illetaL, 1992; Norman etal., 1994b, 1999;BoUiGhetal., 1998c). By comparison, the<br />
taUer, leafier longer-season cultivars required only 100 to 135 kg N/ha o f N fertilizer<br />
to produce maxim um yields, but they also produced substantially lower grain yields<br />
<strong>and</strong> were much more subject to lodging. The milling quality o f stiff-strawed rice<br />
cultivars was highest at the N fertilizer rates that produced the maximum grain yields<br />
(Jongkaewwattana et al., 1993). It has also been observed that the milling quality of<br />
a good milling cultivar was affected less by the N fertilizer rate, whereas a poor or<br />
inconsistent milling cultivar was influenced more by the N fertilizer rate (Norman<br />
et a l, 2000).<br />
<strong>Rice</strong> grain yield is influenced by the number o f tillers, which, in turn, is influenced<br />
by the N fertilizer rate (Wells <strong>and</strong> Faw,1978). Wlren rice st<strong>and</strong>s are thin in dry-seeded,<br />
delayed-flood rice, grain yield can be reduced if the preflood N rate for adequate plant<br />
populations is utilized. Hence, when plant st<strong>and</strong>s are thin but uniformly thin (i.e.,<br />
Soil Fertilization <strong>and</strong> Mineral Nutrition in U.S. Mechanized <strong>Rice</strong> Culture 357<br />
The N fertilizer rate required to achieve optim um yields in rice can be influenced<br />
significantly by the preceding crop. W hen new l<strong>and</strong> is put into rice <strong>production</strong> following<br />
long term-pasture or forest, or when rice is grown in ponds used previously<br />
for commercial fish <strong>production</strong>, readily available N has accumulated in these soils<br />
<strong>and</strong> little if any fertilizer N is required by the rice to achieve the full yield potential<br />
during the first few years. In these situations it is probably best not to apply any early<br />
or preflood N fertilizer, but to use one o f the N diagnostic methods at midseason<br />
to determine if any N fertilizer is required. More typically, in the United States, rice<br />
is grown on l<strong>and</strong> that was cropped to corn {Zea mays L.), grain sorghum [sorghum<br />
bicolor (L.) M oench]., rice, or soybean, or that was left fallow the preceding year.<br />
The decomposition o f the residues from these crops can influence the N fertilizer<br />
rate required by the following rice crop (Norman et al., 1990), Use o f the isotopic<br />
tracer<br />
can give additional insight into the contributions o f crop residues to tlie<br />
following rice crop. Comparisons between the total N uptake <strong>and</strong> the residue N uptake<br />
o f rice utilizing the *^N tracer technique provides a measure o f the influence that tlie<br />
crop residues selected have on the total N uptake o f the following rice crop (Table<br />
3.4.4). Residues from a soybean crop have a narrow C/N ratio, a high N content,<br />
<strong>and</strong> tlius can contribute substantial amounts o f N to the following rice crop through<br />
mineralization (Gilmour et al.,1998). Conversely, residues from rice have a relatively<br />
low N content, a wide C/N ratio, <strong>and</strong> thus can deprive N from the following rice<br />
crop via immobilization. Grain sorghum residue is intermediate in C/N ratio <strong>and</strong> N<br />
content but has a large enough mass o f residue to contribute a significant am ount o f<br />
N to the following rice crop. The field used in this study was tilled during the summer<br />
prior to crop residue application in the fall to prevent grassy weeds from growing<br />
<strong>and</strong> to eliminate any fallow effect. Although it was not desired in this study, allowing<br />
grassy weeds or winter cover crops to grow when l<strong>and</strong> is fallow is beneficial to the<br />
soil, native soil N fertility, <strong>and</strong> thus can decrease the fertilizer N requirements o f a<br />
TABLE 3.4.4. Mean Total N <strong>and</strong> Residue N Accumulations by the Newbonnet <strong>Rice</strong> Cultivar after<br />
Selected Crop Residues Labeled witK^^N Were Fall Applied to a DeW itt Silt Loam (Typic<br />
Albaqualfs), 1988 <strong>and</strong> 1989<br />
Crop Residue"<br />
<strong>Rice</strong> Crop N Uptake<br />
Rate<br />
(kg N/ha)<br />
Type<br />
kg/hn k g N/ha C;N ratio<br />
Total N * Residue N ‘^<br />
Tilled fallow .— . — — 108 0<br />
<strong>Rice</strong> 7800 41 78:1 96 3<br />
Grain sorghum 8300 77 44:1 1 2 0 19<br />
Soybean 3800 81 19:1 131 26<br />
Source: Unpublished data of R. J, Norman <strong>and</strong> J. T. Gilmour.<br />
"The summer prior to residue application the soil was maintained weed-free with frequent tillage. All crop<br />
residues were applied in September, mechanically incorporated into the soil to a 10-cm depth, <strong>and</strong> the<br />
subsequent rice crop seeded the foUowing May.<br />
''Urea was applied at 34 kg N/ha immediately prior to flooding to promote rice growth.<br />
‘Crop residues were labeled with '®N. The contribution of the N contained in the crop residues to tlie total<br />
N uptake of die following rice crop was calculated utilizing the total N <strong>and</strong> atom % of the selected crop<br />
residues <strong>and</strong> the resulting total N <strong>and</strong> atom % '®N of the following rice crop.
358 Production<br />
subsequent rice crop. Hence fallowed l<strong>and</strong> should not be tilled until just prior to rice<br />
seeding if the fallow effect is to be realized. <strong>Rice</strong> grown on l<strong>and</strong> that was fallowed the<br />
previous year frequently requires less ISl fertilizer than rice following soybeans. A ban<br />
on burning rice straw in California was shown after several years to have a positive<br />
impact on the N fertilizer requirement o f continuous water-seeded rice (Eagle et al.,<br />
2000). A few years o f rice straw incorporation led to higher native soil N levels <strong>and</strong><br />
less N fertilizer required to reach maxim um grain yields. Thus increased retainment<br />
o f plant residues should increase native soil N levels, but it may take a few years to<br />
realize the benefits.<br />
The soil texture can have a profound influence on the N fertilizer rate required<br />
for rice. S<strong>and</strong>y soils have a low CEC <strong>and</strong> can be highly permeable. Consequently,<br />
NH4 fertilizer can be subject to considerable leaching losses in s<strong>and</strong>y soils, <strong>and</strong> the<br />
N rate may have to be increased <strong>and</strong>/or multiple applications utilized to overcome<br />
these losses. <strong>Rice</strong> grown on clayey soils generally requires 35 to 65 kg N/ha more N<br />
fertilizer than does rice grown on silt loam soils to achieve similar grain yields (Figure<br />
3.4.6), although clayey soils ordinarily contain higher total N content (Chen et al.,<br />
1989; Trostle et a l, 19,98; Norman et al. 1999). Two plausible chemical mechanisms to<br />
explain this phenom enon are NH4fixation in clayey soil by 2; 1 clay minerals (Norman<br />
et ah, 1987; Chen et a l, 1989) <strong>and</strong> NH4 diffusion constraints in clayey soils (Trostle<br />
et al,, 1998). Silt loam soils contain considerably less clay minerals than do clayey<br />
soils; thus there is potentially less clay fixation o f the NH4 fertilizer in sût loam soils.<br />
Also, NH4 fertilizer can diffuse to the rice roots more readily in sÜt loam soils than<br />
in clayey soils. Diffusion is the m ajor mechanism by which NH4 is transported to<br />
plant roots in soil (Tisdale et a l, 1993). The only ways to overcome fixation by clay<br />
<strong>and</strong> diffusion constraints is to increase the concentration o f N H 4 fertilizer in clayey<br />
soils. This can be accomplished by increasing the N H 4 fertilizer rate or with b<strong>and</strong><br />
application o f NH4 fertilizer. The split method also appears to facilitate N uptake by<br />
rice on some clayey soils.<br />
^10- . t<br />
Figure 3.4.6. Grain yield response of two rice cultivars grown on a Sharkey clay ond<br />
DeWitt silt loam soils when different rates of N fertilizer were applied, (Unpublished data<br />
of R. J. Horman.)
Soil Fertilization <strong>and</strong> Mineral Nutrition in U.S, Mechanized <strong>Rice</strong> Culture 359<br />
Different N fertilizer application metliods require different N fertilizer rates. The<br />
OPP N application method characteristically requires 35 kg N/ha less N fertilizer than<br />
does the split N method, <strong>and</strong> at times 65 kg N/ha less N fertilizer to achieve com parable<br />
rice grain yields (Figure 3.4.5). In general, when the number o f N applications<br />
in the split method are increased, the greater the probability that the N fertilizer<br />
rate will have to be increased to achieve maximum yields. Multiapplication methods<br />
require higher N fertilizer rates than does the O FF method, because as the frequency<br />
o f applications increases, the probability increases for the N to be applied at times<br />
when the rice plant cannot utilize the fertilizer efficiently.<br />
Water management, soil pH, <strong>and</strong> N source can play a large role in efficient N<br />
fertilizer uptake by rice <strong>and</strong> thus on the N rate needed. More N fertilizer will be needed<br />
if there is an inability to flood the field in a timely manner following N fertilizer<br />
application (Table 3.4.1 <strong>and</strong> Figure 3.4.2). This is especially true if urea is applied<br />
to soil with a pH > 7, due to the increased probability o f NH3 volatilization losses.<br />
In these situations, am m onium sulfate should possibly be used in place o f urea, but<br />
the N fertilizer rate will still probably have to be increased by 20 to 40 kg N/ha. The<br />
inability to maintain a flood can cause the N fertilizer rate to be inadequate due to N<br />
loss via nitrification-denitrification. Furrow <strong>and</strong> flush-irrigated rice may suffer from<br />
this problem. M aintenance o f the floodwater in rice culture is im portant not only in<br />
efficient N fertilizer management but also for the availability of many other nutrients<br />
im portant for proper rice growth.<br />
No-till systems may increase the probability o f immobilization <strong>and</strong> NH3 volatilization<br />
losses o f fertilizer N, because o f the plant residue that remains on the soil<br />
surface. Immobilization o f fertilizer N has been reported to be twice as great in no-till<br />
than in plowed soils (<strong>Rice</strong> <strong>and</strong> <strong>Smith</strong>, 1984). No-tiU usually leads to higher soil bulk<br />
densities, which could influence the movement o f N fertilizer into the soil with the<br />
floodwater. Initial research conducted on silt loam <strong>and</strong> clay soils found no significant<br />
influence o f the tillage system on the N fertilizer rate required by rice to reach m axim<br />
um grain yield (Bollich, 1995; W ilson et al„ 1996). M ore research is required with<br />
reduced <strong>and</strong> no-till systems to fuUy ascertain its impact on the N fertilization o f rice.<br />
PHOSPHORUS BEHAVIOR, FERTILIZATION, AND NUTRITION<br />
Historically, direct P fertilization has rarely resulted in a grain yield response from rice<br />
grown in the United States, due to the positive effects o f flooding on soil P availability<br />
(Bartliolomew, 1931; Beacher, 1952; Place et a l, 1971b). However, recent occurrences<br />
o f P deficiency by rice in the United States have led to a resurgence o f interest in better<br />
underst<strong>and</strong>ing soil P transformations <strong>and</strong> availability under flood conditions. The<br />
following discussion o f rice P nutrition <strong>and</strong> P behavior in flooded soil will center<br />
on summarizing our current underst<strong>and</strong>ing o f P availability to flooded rice <strong>and</strong> to<br />
highlight areas that should be considered for future research.<br />
Phosphorus Forms <strong>and</strong> Behavior in Flooded <strong>Rice</strong> Soils<br />
To underst<strong>and</strong> the response o f rice to P fertilizers, it is first necessary to have some<br />
Imowledge o f the chemistry o f P in soils in both aerobic <strong>and</strong> waterlogged soils. A vast
360 Production<br />
I I<br />
U<br />
l l ; i<br />
■ Il<br />
amount o f research has been conducted during the twentietli century on the chemical<br />
transformations o f soil P (Olsen <strong>and</strong> Khasawneh, 1980). Although our underst<strong>and</strong>ing<br />
o f P chemistry in flooded soils has increased dramatically during the past 50 years,<br />
there are still areas that need further research to better underst<strong>and</strong> P fertilizer needs<br />
for rice.<br />
Phosphorus exists in soils in two basic pools, organic <strong>and</strong> inorganic. The organic<br />
P consists o f P that is part of the soil organic matter <strong>and</strong> soil biomass. Although<br />
these forms are not immediately available for plant uptake, the dynamic nature of<br />
soil organic matter mineralization <strong>and</strong> immobilization processes dictate that some of<br />
this P can contribute to plant-available P. However, it is the inorganic P that regulates,<br />
to the greatest degree, the availability o f P for plant uptake. Inorganic P in soils has<br />
been characterized into the following forms: (1) calcium phosphate (C a-P), (2) iron<br />
phosphate (Fe-P), (3) aluminum phosphate (Al-P), (4) occluded P [reductant-soluble<br />
phosphate (R SP )], <strong>and</strong> (5) P in solution as the soluble orthophosphates PO 4“ , HPO^”,<br />
o rH 2P 04 (Chang <strong>and</strong> Jackson, 1957).<br />
The solution P form most readily utilized for plant uptake is H 2PO4 , which is the<br />
therrpodynamically stable form o f P in the pH range 6.0 to 6.5. As the soil pH increases<br />
above 7.0, tlie ratio of H 2PO4 to HPO 4" narrows, with HPO4“ becoming the dominant<br />
form at a pH near 8.0. Although HPO^^ is a plant-available form o f P, it is talcen<br />
up by plants nearly 10 times more slowly than HaPOy (Olsen <strong>and</strong> Khasawneh, 1980).<br />
The P anions are taken up by rice from the soil solution. The most im portant source<br />
of replenishment of this P is the P associated with primary <strong>and</strong> secondary minerals<br />
(i.e., Fe-P, Al-P, <strong>and</strong> Ga-P, <strong>and</strong> RSP). Subsequently, it is the transformations o f these<br />
minerals under flooded conditions that becom es the forem ost factor in determining<br />
P availability to rice.<br />
The dom inant inorganic P fractions described previously (Ca-P, Fe-P, Al-P, <strong>and</strong><br />
RSP) are found in all soils to some degree. However, the proportions o f each fraction<br />
differ considerably. In acid soils, Fe-P, Al-P, <strong>and</strong> RSP are the dom inant forms, with<br />
little or no Ca-P present. Neutral soils generally have a balance o f all four fractions. In<br />
alkaline or calcareous sods, the proportion o f Ca-P to other forms becomes considerably<br />
greater. The distribution o f each fraction at various soil pH levels is important<br />
because it affects the availability o f P after flooding.<br />
Flooding soils causes significant physiochemical changes as oxygen is depleted<br />
<strong>and</strong> reduction proceeds. Specifically, the soil pH tends to adjust toward neutrality,<br />
the partial pressure o f CO 2 <strong>and</strong> the ionic strength of the soil solution tend to increase,<br />
<strong>and</strong> the redox potential decreases (Ponnamperuma, 1972). Each o f these phenomena<br />
affect P solubility, either directly or indirectly. The adjustment in soil pH <strong>and</strong> increase<br />
in ionic strength tends to increase the solubility o f Fe, Al, <strong>and</strong> Ca phosphates. The<br />
reduction in redox potential coincides with the dissolution o f ferric oxides <strong>and</strong> the<br />
liberation of RSP.<br />
After O 2 <strong>and</strong> NO3 have become depleted, Fe <strong>and</strong> M n become significant electron<br />
acceptors for anaerobic <strong>and</strong> facultative bacteria <strong>and</strong> are reduced from Fe^'*' to Fe^'^<br />
<strong>and</strong> Mn^^‘ to Mn^^, respectively. As the redox potential declines to the level where<br />
Fe^+ reduction occurs, stable ferric oxides <strong>and</strong> hydroxides, such as strengite, are transformed<br />
to soluble ferrous oxides <strong>and</strong> hydroxides, such as vianite [Fe3(P 04)2 •8H 2O]<br />
(Lindsay, 1979). Phosphorus that is occluded with coatings o f relatively insoluble Fe<br />
<strong>and</strong> Al hydroxides <strong>and</strong> oxides, also referred to as RSP, tends to be solubilized due<br />
to dissolution o f the Fe <strong>and</strong> Al-oxide coatings as soil pH increases. This occluded P
Soil Fertilization <strong>and</strong> Mineral Nutrition in U.S. Mechanized <strong>Rice</strong> Culture 361<br />
provides a significant am ount o f the available P in flooded soUs, particularly in acid<br />
soils (Patrick <strong>and</strong> Mahapatra, 1968).<br />
In acid soils, the reduced Fe-P <strong>and</strong> the RSP are m ajor contributors to available <strong>and</strong><br />
readily available P for rice due to increased solubility <strong>and</strong> increased rates o f P diffusion<br />
in the soil (Patrick <strong>and</strong> Mahapatra, 1968; Turner <strong>and</strong> Gilliam, 1976a,b). Labile P is<br />
in equilibrium with solution P. In contrast, P availability in allcaline soils is more<br />
closely related to the sorption <strong>and</strong> desorption o f Ca-P (Patrick <strong>and</strong> Mahapatra, 1968).<br />
Although Ca-P minerals are not directly affected by reduction processes, increased P<br />
availability in flooded alkaline soils has been observed, due to increased P diffusion in<br />
the soil <strong>and</strong>, in turn, increased root uptake (Turner <strong>and</strong> Gilliam, 1976a,b). Although<br />
increased P diffusion <strong>and</strong> an increase in Ga solubility caused from the increase in<br />
ionic strength are observed in flooded alkaline soils, this increase in solubility does<br />
not always provide sufficient amounts o f available P to rice (W ilson et ah, 1999).<br />
Lower amounts o f RSP <strong>and</strong> Fe-P found in alkaline soils result in less solubilized P after<br />
flooding (Sail <strong>and</strong> Mikkelsen, 1986). Subsequently, the response of rice to P fertilizer<br />
on alkaline soils becomes twofold: ( 1) smaller amounts o f RSP <strong>and</strong> Fe-P result in less<br />
solubilized P, <strong>and</strong> (2) the increase in HPO^" relative to H2PO4 reduces the available<br />
P because o f the uptake differences between these forms o f P (Olsen <strong>and</strong> Khasawheh,<br />
1980). It is not completely understood how the change in P fractionation associated<br />
with an increase in soil pH affects P availability in flooded soils. Research suggests<br />
that P deficiency is m ore likely to occur in rice produced on alkaline soils than in<br />
tliat produced on acid soils (Table 3.4.5). In contrast, decreased rice yields have been<br />
measured on acid soils from excessive P fertilization (Wilson et al., 1997).<br />
Phosphorus Nutrition, Fertilization Practices, <strong>and</strong> Diagnosis of Deficiency<br />
Phosphorus fertilization o f rice in the United States appears to be largely dependent<br />
on soil characteristics such as texture, pH, <strong>and</strong> whether the soil has been altered<br />
by l<strong>and</strong> forming. However, cropping pattern <strong>and</strong> intensity also appear to have an<br />
TABLE 3.4.5. Comparison of P tissue concentration <strong>and</strong> rice grain yield in response to P<br />
fertilization at two locations that differ in soil pH, but have similar Mehlich 3 extractoble P<br />
concentrations<br />
P Fertilizer Rate<br />
Midtillering <strong>Rice</strong> P Concentration<br />
(aP/kg)<br />
Grain Yield<br />
tkg/ha)<br />
P Fertilizer Rate<br />
(k g P / h a }~ '<br />
Poinsett Co., AR Cross Co., AR Poinsett Co., AR Cross Co., AR<br />
County, County, County, County,<br />
%<br />
kg ha“ '<br />
0 03.2 0 . 1 0 7515 4170<br />
2 0 0.36 0 . 1 1 7067 6066<br />
LSD(o,o5) n.s. 1 n.s. 443 350<br />
Mehlich 3 extractable P (mg P/kg)~* 7 8<br />
Soil pH 5.8 8 . 0<br />
Source; Data from Wilson et a t (1997).<br />
'f'n.s., not significant at the 0.05 level of probability.
362 Production<br />
influence on the P fertilization o f rice. Very little P fertilizer was recommended for<br />
direct application to rice in the southern rice belt prior to the late 1980s. In Arkansas,<br />
as the frequency o f soybean in the crop rotation with rice declined <strong>and</strong> the pH values<br />
o f our soils increased from the continued use o f high-bicarbonate groundwater for<br />
irrigation, the need for m ore direct application o f P fertilizer to rice resulted. The<br />
development o f higher-yielding stiff-strawed rice cultivars has also played a role in<br />
the need for more direct P fertilization o f rice, due simply to the greater removal o f P<br />
from the soil in the harvested grain. There has not been any proof that stijff-strawed<br />
cultivars require m ore P than their predecessors or that U.S. rice cultivars differ to<br />
any great extent in their P requirements. However, if equal concentrations o f P are<br />
assumed, higher grain yield results in larger amounts o f P required for grain filling.<br />
Therefore, the discussion o f P nutrition <strong>and</strong> fertilization o f rice will focus on (1) the<br />
P-uptake characteristics o f rice; (2) how soil characteristics, soil testing, <strong>and</strong> cropping<br />
patterns influence P fertilization; (3) how P application timing influences rice growth<br />
<strong>and</strong> grain yields; <strong>and</strong> (4) P deficiency <strong>and</strong> diagnosis in rice.<br />
Phosphorus Nutrition<br />
i<br />
m -<br />
Adequate P nutrition o f rice is essential since it is required for energy storage <strong>and</strong><br />
transfer within the plant. In addition to the m etabolic functions, P has. been observed<br />
to increase root growth <strong>and</strong> promote early maturity, straw strength, crop quality, <strong>and</strong><br />
disease resistance. Solution P in the forms o f HPO^" <strong>and</strong> H 2PO4 are the forms taken<br />
up by rice, with H 2PO 4 being the dom inant form . Although P is considered a m ajor<br />
nutrient, P is taken up in much smaller quantities than are N <strong>and</strong> K. Typical seasonal<br />
concentration <strong>and</strong> uptake o f P by rice is illustrated in Figure 3.4.7. The concentration<br />
o f P in the plant tissue (straw) remains relatively constant with age until heading<br />
<strong>and</strong> then decreases as P is translocated to the panicles (Sims <strong>and</strong> Place, 1968). Thus<br />
total P uptake increases in conjunction with total dry matter. M axim um uptake is<br />
achieved around heading with the entire crop containing approximately 30 to 50 kg<br />
P/ha, depending on the yield. A rice crop with a grain yield o f 9000 kg/ha would have<br />
a total P uptake o f 47 kg P/ha. Approximately 30 kg P/ha would be contained in the<br />
grain <strong>and</strong> about 17 kg P/ha in the straw. The am ount o f P in the grain comprises<br />
approximately 60 to 75% o f the total P taken up by the rice plant.<br />
Soil Test Methods for Phosphorus<br />
Unlike N, P fertilizer is applied to rice based on the am ount o f P in the soil that<br />
can be extracted using various chemical reagents. Unfortunately, it is not quite that<br />
straightforward since the soil test methods currently used by both university <strong>and</strong><br />
private laboratories are somewhat limited in their ability to predict rice response to<br />
P fertilization (Shah<strong>and</strong>eh et al., 1994, 1995; W ilson et al., 1999). This is because aU<br />
the soil test methods currently employed were developed for estimating available P<br />
for upl<strong>and</strong> crops grown under aerobic conditions. The lack o f confidence in these<br />
methods is illustrated by the fact that a consensus cannot be reached among the riceproducing<br />
states on which soil test extractant is best for estimating P availability for<br />
rice. The lim itation o f these methods tend to be their inability to extract the RSP<br />
fraction, which is critical to estimating P availability in flooded soils (Shali<strong>and</strong>eh et a l,<br />
1994,1995). The best scientific approach for development o f a soil test procedure for
Soil Fertilization <strong>and</strong> Mineral Nutrition in U.S. Mechanized <strong>Rice</strong> Culture 363<br />
I<br />
li<br />
Figure 3.4.7. Seasonal tissue P concentration (/Ij, total P uptake (fi),<br />
<strong>and</strong> total dry matter (C) of poddy rice (average of about 50 studies. (From<br />
Wilson etal, 1999.)<br />
a particular nutrient is first to determine what forms o f the nutrient are being utilized<br />
by the plant <strong>and</strong> then develop a method to extract those forms (Bray <strong>and</strong> Kurtz, 1945).<br />
Although some soil tests for P were developed on this premise, they were developed<br />
for use with upl<strong>and</strong> crops. Because the flooded environm ent associated with paddy<br />
rice <strong>production</strong> alters the chemical forms o f P in these soils significantly, the methods<br />
do not adequately characterize the change in labile P associated with flooding.<br />
Soil test methods used for estimation o f P availability to rice in each U.S. riceproducing<br />
state are Mehlich 3, Arkansas; Olsen, California; Bray 2, Louisiana; Lancaster,<br />
Mississippi; Bray 1, Missouri; <strong>and</strong> am m onium acetate-EDTA, Texas. It is
:■/I<br />
364 Production<br />
i :<br />
common for each o f these methods to underestimate P availability in flooded rice<br />
soils. Other methods have been shown to be perhaps more suitable for rice. Probably<br />
the most consistent <strong>and</strong> accurate method is P extraction by anion-exchange resin,<br />
which was developed as a means o f estimating the P quantity factor (Teo et al., 1995b).<br />
This method involves a lengthy incubation period, <strong>and</strong> the time required is not conducive<br />
for use in routine sod testing laboratories. However, the anion-exchange resin<br />
method may possibly be used as a st<strong>and</strong>ard in the development o f a P soil test method<br />
suitable for use in routine sod testing laboratories.<br />
Although it is well Icnown that P availability is dependent on soil pH, little information<br />
has previously documented the relationship between soil pH <strong>and</strong> P fertilizer<br />
response by flooded rice. It is well established that P fertilizer applications often result<br />
in increased dry matter <strong>production</strong> by rice with no appreciable effect on grain<br />
yield (Place et a l, 1971b). However, research has documented increased dry matter<br />
accumulation <strong>and</strong> grain yield by rice from P applicatiori, particularly on alkaline sods<br />
(Table 3.4,5). By contrast, the excessive vegetative dry matter or straw produced from<br />
P applications to the acid soils in the southern United States may result in increased<br />
lodging arid reduced yield (Place et al., 1971b) (Table 3.4.5).<br />
Although data suggest tliat fertilizer response is related to soil pH (Table 3.4.5),<br />
the utilization o f sod pH alone is not reliable as an indicator o f P fertilizer response<br />
(Wilson et al., 1999). Sod pH is not static <strong>and</strong> can vary by as m uch as 1.0 pH unit,<br />
depending on sample time, environmental conditions, <strong>and</strong> method o f pH determination.<br />
However, for soils in the southern United States it is clear that the soil testing<br />
procedures currently used are inadequate for flooded rice culture. Because o f the<br />
growing environmental concerns related to non-point-source pollution presumably<br />
caused by excessive fertilizer applications, it is imperative that a method be developed<br />
to accurately estimate P availability for rice.<br />
Many producers in the southern United States are concerned about low extractable<br />
P <strong>and</strong> are interested in raising these sods to higher values with extra P<br />
fertilizer. The flooded soil conditions used for rice <strong>production</strong> are known to limit the<br />
availability o f P to upl<strong>and</strong> crops following rice in rotation. Differences in extractable P<br />
foUowing rice compared to soybean idustrate the effects o f flooded rice on extractable<br />
P after the soils are aerated (Slaton et al., 2000). On silt loam sods in Arkansas, sod<br />
test P increased with increasing P fertilizer rate foUowing soybeans but decreased<br />
following the subsequent rice crop (Figure 3.4.8). The magnitude appeared to be<br />
greater on an alkaline soil than on an acid soil. In contrast, when P was applied to<br />
continuous rice, a slight initial increase was observed on the alkaline soil, but no<br />
appreciable effect was observed on the acid soil (Figure 3.4.8). It is clear that previous<br />
cropping <strong>history</strong> plays a significant role in Mehlich 3 extractable P. Simdarly, soil pH<br />
<strong>and</strong> previous crop seemed to affect P uptake by the subsequent rice crop (Table 3.4,6).<br />
On the aUcaline soil, the P concentration <strong>and</strong> uptake by rice was greater following<br />
soybean than following rice, However, the P concentration in the rice tissue was<br />
greater foUowing rice on the acid soil <strong>and</strong> no difference in total P uptake between<br />
the two rotational crops. Phosphorus that is solubdlzed during flooding becomes<br />
occluded upon aeration, resulting in less available P present prior to flooding (Figure<br />
'3.4.8) (Sah <strong>and</strong> Mikkelsen, 1986). The result is that upl<strong>and</strong> crops grown following<br />
flooded rice often experience P deficiency despite adequate soil test P (Br<strong>and</strong>on <strong>and</strong><br />
Mikkelsen, 1979). This effect does seem to dissipate with time as P deficiency observed<br />
in the second <strong>and</strong> third crops following rice becom e less severe. Consequently, soil pH
Soil Fertilization <strong>and</strong> Mineral Nutrition in U.S. Mechanized <strong>Rice</strong> Culture 365<br />
8>R-S Rotation<br />
Dewitt silt loam<br />
initial ;pH»6.0; P *8 mg kg ’<br />
Soy boon Crop<br />
1<strong>Rice</strong> Crop<br />
Continuous <strong>Rice</strong> Rotation<br />
Dewitt silt loam<br />
Initial: pH**6.0; P«12.5 mg kg ’<br />
10 15 20 25 30 35 0 5 10 15<br />
Tim e After A p plication (mo)<br />
20 25 30 35<br />
Figure 3,4.8. Influence of P fertilizer rate <strong>and</strong> crop rototion or Mehlkh 3-extractoble P in 3 years of<br />
soybean-rice-soybean (S-R-S) rotation or continuous rice at two locations between f 998 <strong>and</strong> 2000. (From<br />
unpublished data of N. A. Slaton, R. J. Norman, <strong>and</strong> C. E. Wilson, Jr.)<br />
<strong>and</strong> previous crop significantly aiEfect measured P availability, particularly in relation<br />
to time o f sampling. Thus, increasing Mehlich 3 extractable P <strong>and</strong> perhaps P extracted<br />
by other methods appears to be difficult when rice is regularly grown in the rotation.<br />
A better underst<strong>and</strong>ing o f the transformations of P following flood removal is needed<br />
to know the proper time to sample the soil to obtain an accurate measurement <strong>and</strong><br />
underst<strong>and</strong>ing o f soil P availability to subsequent crops.<br />
Phosphorus Fortllization Practices <strong>and</strong> Diagnosis of Deficiency<br />
The soil test methods employed in each o f the m ajor rke-producing states extract<br />
a different quantity o f P from soU. Thus it is impossible for there to be a consensus<br />
among the states as to how m uch P fertilizer to apply for a given am ount o f extractable<br />
P. In general, P fertilizer rates o f30,2 0 , <strong>and</strong> 10 kg P/ha are recommended for rice when<br />
the soil tests very low, low, <strong>and</strong> medium in P, respectively.<br />
Although the need for adequate P fertilization is com m on am ong all the rice<br />
<strong>production</strong> systems utilized in the United States, the tim ing o f application can vary
366 Production<br />
TABLE 3.4,6.<br />
In flu e n c e o f P re v io u s C ro p ( 1 9 9 8 crop) o n P C o n c e n tra tio n a n d Total P U p ta k e by<br />
th e S u b s e q u e n t R ice C ro p [1 9 9 9 crop] a t Tw o L o catio n s<br />
Previous Crop <strong>Rice</strong> Tissue P concentration <strong>Rice</strong> Total P Uptake<br />
PT B St RREC PTBS RREC<br />
I-Ir<br />
i<br />
I I :;<br />
% kg P h a “ '<br />
<strong>Rice</strong>* 0.27 0.30 9.5 17.8<br />
Soybean 0.31 0,28 13.8 18.8<br />
Source: Data from Slaton et al. (2000).<br />
"ipTBS = University of Arkansas Pine Tfee Experiment Station} soil pH 7.5) Mehlich 3 extractable P =<br />
11.5 mg P kg“ ‘, RREC, University of Arkansas <strong>Rice</strong> Research <strong>and</strong> Extension Center; soil pH 6.1, Mehlich<br />
3-extractable P = 11.5 mg P/kg.<br />
*1998 crop.<br />
ü<br />
H i<br />
I<br />
1i:!.<br />
■ iT'P<br />
^I<br />
ii;:r i<br />
slightly depending on the cultural management system. For dry-seeded, delayed-<br />
flood rice culture, P fertilizer is generally applied to fields eitlier in the fall, in the<br />
spring immediately prior to seeding, or prior to establishment o f the permanent<br />
flood (i.e., four- to five-leaf growth stage). In water-seeded rice <strong>production</strong>, P is<br />
usually incorporated prior to establishment o f the permanent flood in either the fall<br />
or spring. Phosphorus fertilizer applied prior to seeding is normally incorporated<br />
mechanically in soil; however, this is not a necessity, since available P near the soil<br />
surface is readily accessible to the extensive fibrous root system o f flood-irrigated<br />
rice (Teo et al., 1995c). Preplant application o f P without incorporation is a common<br />
practice in no-till seeded rice.<br />
Several P fertilizer sources <strong>and</strong> application times are effectively utilized in U.S.<br />
rice <strong>production</strong>. Triple superphosphate (TSP) typically contains 20% P (46% P2O5)<br />
<strong>and</strong> is the most com m only used P source in the southern U.S. rice belt for applications<br />
made prior to seeding or preplant. D iam m onium phosphate (DAP) contains a similar<br />
amount o f P as TSP, is usually competitive with TSP in price, <strong>and</strong> frequently is used<br />
either preplant or preflood because o f the additional N. The most com m on grade<br />
of DAP contains 20% P (46% P2O 5) <strong>and</strong> 18% N. If other preplant fertilizers are not<br />
required, P fertilizer can be blended <strong>and</strong> applied at the four- to five-leaf growth stage<br />
with the N fertilizer that is normally applied just prior to establishment o f the permanent<br />
flood. Diam m onium phosphate is com monly used in this situation since it contains<br />
appreciable NH4-N. Preflood P applications have been shown to be as effective<br />
as preplant P applications <strong>and</strong> may offer a small savings in application costs if applied<br />
aerially with the urea at preflood (Table 3.4.7). In addition, for soils that are responsive<br />
to P fertilizer, application of P immediately prior to establishment of the permanent<br />
flood provides available P to the rice at the beginning of the period o f pealc dem<strong>and</strong>.<br />
A flooded soil can take 1 to 2 weeks to become sufficiently reduced to liberate RSP.<br />
On soils that have a <strong>history</strong> o f P deficiency or are highly responsive to P fertilization,<br />
split applications have been utilized successfully. O ne-half o f the P fertilizer is<br />
applied prior to seeding, followed by the remaining amount applied prior to flooding.<br />
Phosphorus fertilizer should be applied directly to the rice crop at preplant or preflood<br />
on responsive soils, since P fertilizer applied to previous crops or in the faU may<br />
be unavailable to rice during critical growth stages. Questions persist regarding the<br />
kinetics of'P fertilizer transformations, particularly on aUcaline soils.
Soil Fertilization <strong>and</strong> Mineral Nutrition in U.S. Mechanized Rite Culture 367<br />
T A B LE 3.4.7.<br />
In flu e n c e o f P A p p lic o t io n T im in g o n R ice G r a in Y ie ld s<br />
<strong>Rice</strong> G rain Yield (kg/ha)<br />
D avis Farm<br />
W im p y Farm<br />
Time of P Application<br />
1997 1998 1997 1998<br />
Control 6372 7222 7665 6953<br />
Preemerge 7656 7561 8196 6760<br />
Preflood 7204 7868 8579 7011<br />
Postflood (7 days) 7914 7839 9416 6873<br />
Panicle differentiation 6612 7420 8198 6713<br />
LSDo,05 806 512 574 n.s.<br />
Soil test P (kg/ha) 1 0 17 28 20<br />
Soil pH 7.6 6 . 8 8 . 0 7.7<br />
Source: Data from Wilson et al, (1999).<br />
Midseason applications o f P fertilizer have been found to increase grain yield<br />
for salvage situations (Table 3.4,7). W hen P fertilizer was not applied preplant or<br />
preflood, application o f P at midseason did provide some recovery o f rice grain yields.<br />
However, full recovery has not been achieved in these situations. Phosphorus fertilizer<br />
applications later than midseason have not been investigated.<br />
Phosphorus is often needed on soils that have recently been altered by l<strong>and</strong> form <br />
ing. Although poultry litter is an effective means o f increasing productivity on these<br />
soils, addition o f P fertilizer at arate of20kgP/ha along with poultry litter often results<br />
in the highest rice grain yields (M iller et al., 1991). Available P generally decreases<br />
as soil depth increases, particularly on the silt loam soils com m only used for rice<br />
<strong>production</strong> in the southern United States. Subsequently, removal o f topsoil during<br />
l<strong>and</strong> forming results in reduced available P. Although, poultry litter provides some P<br />
to the rice crop, P fertilizer is still recommended on graded soils to ensure adequate<br />
P availability for optim um plant growtli.<br />
Severe foliar P-deficiency symptoms are rarely observed in the field. W hen symptoms<br />
are present, they are usually very subtle <strong>and</strong> difficult to identify. However,<br />
absence of deficiency symptoms does not necessarily indicate that the P level is adequate.<br />
Plants generally suffer from deficiency prior to exhibiting symptoms. This<br />
phenomenon, known as hidden hunger, occurs when the soil nutrient level is low<br />
enough to limit the plants’ yield potential but high enough to sustain growth without<br />
visual deficiency symptoms. Hidden hunger can lead to reduced yields. Subsequently,<br />
when plants do exhibit deficiency symptoms, m ajor yield losses may be observed.<br />
Phosphorus-deficiency symptoms are most com monly observed in rice during<br />
active tillering, but may be observed in seedling rice in severe cases. Phosphorus<br />
is mobile in the plant, <strong>and</strong> therefore deficiency symptoms may appear in the older<br />
leaves first. As a result, mature leaves <strong>and</strong> tillers may die when P is limiting plant<br />
growth. Classic P-deficiency symptoms are moderate to severe stunting; small, very<br />
erect, <strong>and</strong> dark bluish-green leaves; small stem diameter; reduced or no tillering; <strong>and</strong><br />
delayed plant development. Nondassical P-deficiency symptoms may be displayed<br />
when an interaction occurs witli other nutrient deficiencies or stresses. <strong>Rice</strong> subjected<br />
to salinity stress <strong>and</strong> P deficiency prior to flooding has been observed to have moderate
368 Production<br />
III;<br />
stunting with pale green or chlorotic leaves. Another symptom that may be observed<br />
is bronzed leaves, although tliis particular symptom alone is not indicative o f P deficiency.<br />
Other nutrient deficiencies, such as Zn, also cause bronzing to appear on<br />
rice leaves. Phosphorus <strong>and</strong> Zn deficiency in rice have some com m on symptoms. The<br />
expression o f both deficiencies is m ost dramatic soon after establishment o f the perm<br />
anent flood, <strong>and</strong> cause bronzed leaves <strong>and</strong> the obvious stunted plants expected from<br />
m ost nutrient deficiencies. Consequently, diagnosis o f nutritional disorders based<br />
entirely on symptomology can often result in misdiagnosis <strong>and</strong> create confusion.<br />
Plant analysis is critical for correct diagnosis o f P <strong>and</strong> other nutrient deficiencies<br />
in commercial field conditions, because visual diagnosis o f deficiencies can be<br />
misleading due to the possibility o f nonclassical symptomology. Successful diagnosis<br />
with plant analysis is most often achieved by collecting <strong>and</strong> analyzing plants from both<br />
good <strong>and</strong> poor growing areas o f the field. Because P <strong>and</strong> other nutrient concentrations<br />
can vary among growth stages, plant parts, locations, <strong>and</strong> environments, this simply<br />
serves as a comparison to determine the P or nutrient status in the particular field<br />
o f interest at the current growth stage. <strong>Rice</strong> typically has an average P concentration<br />
in the whole plant o f 0,2% or greater at the midtHlering growth stage (Reuter <strong>and</strong><br />
Robinson, 1986). Deficiencies are suspected when the P concentration is < 0.15% .<br />
The Y-leaf concentration is typically in the range 0.14 to 0.27% P at midtiUering <strong>and</strong><br />
0.18 to 0.29% P at panicle initiation (Bell <strong>and</strong> Kovar, 2000).<br />
lliti!5V-.<br />
POTASSIUM BEHAVIOR, NUTRITION, AND FERTILIZATION<br />
l i<br />
ft?“-“<br />
•‘[■t<br />
if<br />
ilM.<br />
cl ■I i'<br />
i';;<br />
Potassium deficiency has not been a com m on problem in rice or crops grown in<br />
rotation with rice in the United States. Inherent characteristics o f the rice plant,<br />
its method o f cultivation, <strong>and</strong> crop fertilization practices generally result in very<br />
efficient use o f K. In the United States, detailed research has not been conducted<br />
to clearly define the relationships between soil K <strong>and</strong> rice uptake o f K during the<br />
growing season. Potassium deficiency can easily be predicted by routine soil testing,<br />
prevented by adequate fertilization, <strong>and</strong> plant available K is not subject to the many<br />
loss mechanisms com m on to N, except leaching, or involved in the complex soil<br />
chemistry that influences P availability to rice. Thus compared to N <strong>and</strong> P, few studies<br />
have been published investigating K nutrition o f rice in the United States.<br />
Potassium Forms <strong>and</strong> Behavior in Flooded <strong>Rice</strong> Soils<br />
Conceptually, K exists is the soil in four basic forms: (1) solution, (2) exchangeable,<br />
(3) nonexchangeable or clay fixed, <strong>and</strong> (4) primary <strong>and</strong> secondary minerals. These<br />
four forms o f K are all in a state of dynamic equilibrium. The availability o f K to<br />
rice increases after flooding, due to exchangeable K+ being displaced from the soil<br />
exchange complex into the soil solution by NH| ft'om early N fertilization <strong>and</strong> by Fe^^<br />
<strong>and</strong> Mn'‘+, which are reduced to the more soluble Fe^+ <strong>and</strong> Mn^"'" forms witli soil reduction<br />
(Patrick et al., 1985). Thus initially, soil solution K concentration increases after<br />
flooding. Soil solution<br />
is believed to remain at a more constant level under flooded<br />
conditions compared to upl<strong>and</strong> conditions, although little is known about the availability<br />
o f K later in the growing season after several weeks o f flooded soil conditions.
Soil Fertilization <strong>and</strong> Mineral Nutrition in U.S. Mechanized <strong>Rice</strong> Culture 369<br />
Due to differences in cropping practices <strong>and</strong> soils, the occurrence o f K deficiency<br />
differs among the geographical rice-producing areas o f the United States. In<br />
the midsouth, K deficiencies occur primarily on s<strong>and</strong>y loam soils that have low CEC<br />
<strong>and</strong> potentially high leaching losses <strong>and</strong> on silt loam soils that have not received<br />
adequate K fertilization to replenish K removed by the crop in the harvested grain.<br />
Although K deficiency probably occurred in Arkansas prior to the 1990s, K deficiency<br />
in rice was not documented until 1991 (Slaton et al., 1995; W ilson et al., 1995a).<br />
In 1994, K deficiency com m only affected a few rice cultivars in several northeastern<br />
Arkansas counties. Soil analysis suggested that soil-exchangeable K'^ levels were very<br />
low {
370 Production<br />
m .<br />
i<br />
si:«:<br />
1:<br />
50% heading, remains constant for a few weeks, <strong>and</strong> then has a tendency to decline<br />
slightly until physiological maturity. The pattern o f uptake agrees well with the time of<br />
visual deficiency symptoms. Potassium deficiencies in rice routinely appear between<br />
panicle initiation <strong>and</strong> heading. Acutely K-deficient rice usually displays symptoms<br />
around panicle initiation, with milder K-deficient rice tending to display symptoms<br />
closer to heading.<br />
<strong>Rice</strong> crop uptalce <strong>and</strong> removal of K in the grain has been examined in Arkansas.<br />
Analysis of rough rice (huUs <strong>and</strong> brown rice kernels) from 20 cultivars seeded at<br />
two locations in the Arkansas rice performance trials showed that rough rice ranged<br />
from 0.26 to 0.31% K, with an average of 0.30% . Thus the total removal o f K in<br />
harvested rice grain for rice yielding 9000 kg/ha would be 27 kg/ha. Total crop uptake<br />
<strong>and</strong> removal o f K in the grain were also determined in other studies by taking total<br />
dry matter samples 3 weeks after 50% heading, separating panicles from straw at the<br />
uppermost node, <strong>and</strong> analyzing both straw <strong>and</strong> panicles for nutrients. These studies<br />
showed a much higher total K uptake of 160 kg K/ha with the grain containing<br />
50 kg K/ha. Total crop uptake (straw <strong>and</strong> panicles) o f K in excess o f 200 kg K/ha<br />
has been measured. The amount o f K removed in the harvested grain ranges from<br />
10 to 30% o f the total amount o f K taken up by the rice during tlie season. If rice<br />
straw is found usefirl for energy generation, bedding, or other purposes, a significantly<br />
higher amount o f K will be removed by harvesting both rice straw <strong>and</strong> grain, <strong>and</strong> K<br />
fertilization practices wiU need to be adjusted.<br />
General soil test critical levels at which K fertilization is suggested are listed by<br />
state <strong>and</strong> by extraction method in Table 3.4.8. Although K fertilization recommendations<br />
<strong>and</strong> extraction methods vary among rice-producing states, fertilizer application<br />
is generally recommended when soil test levels are below 50 to 90 mg K/kg.<br />
Potassium chloride (KCl) contains 50 to 52% K (60 to 63% K2O) <strong>and</strong> is the most<br />
common source o f K fertilizer used for rice in the United States. Studies have shown<br />
no management or yield advantage by use o f the recommended rates o f the more<br />
expensive potassium nitrate (37% K or 44% K jO ) or potassium sulfate (42 to 44% K<br />
or 50 to 53% K2O ). Compared to other K sources, KCI has the highest K content <strong>and</strong><br />
T A B LE 3.4.8.<br />
C ritica l S o il T est K L e v e ls b y S ta te a n d Extractant'’<br />
Soil Test Critical LeveP<br />
Fertilizer Rale*^<br />
State<br />
Extractant<br />
(m g K/kg)<br />
(kg KaO/lia)<br />
Arkansas Mehlich 3 8 8 67-100<br />
California I N NHiOAc 60 67-135<br />
Louisiana 1 N NH^OAc 1 0 0 - 2 0 0 22-67<br />
Mississippi Lancaster Method < 60-100 45-90<br />
Texas 1.4 M NH4OAC + 0.025 M EDTA < 50 56<br />
"Extrac:ion methods <strong>and</strong> critical soil test K levels were obtained by contacting each states extension<br />
agronomist responsible for rice <strong>production</strong>.<br />
Louisiana <strong>and</strong> Mississippi botli account for different soil textures or cation-exchange capacities in K<br />
recommendations. As CEC increases or soil particle size decreases, the critical soil K -level increases.<br />
■"When a range of fertilizer application rates are given, the recommended fertilizer rate increases as soil test<br />
K decreases,
Soil Fertilization <strong>and</strong> Mineral Nutrition in U.S. Mechanized <strong>Rice</strong> Culture 371<br />
is the least expensive source o f K. Broadcast applications of K fertilizer typically are<br />
applied prior to planting. Preflood (five-leaf stage) <strong>and</strong> midseason (panicle initiation<br />
to differentiation growth stage) applications o f K fertilizer have been shown to be<br />
equally effective as preplant-incorporated application o f K fertilizer. However, application<br />
o f K fertilizer during late reproductive growth, at the mid-to-late boot stage<br />
(flag leaf emerged), has failed to increase grain yields in field studies in Arkansas.<br />
Preliminary data have shown that tissue K concentration at the midtillering growth<br />
stage is highly correlated with preplant Mehlich 3 extractable K o f silt loam soils<br />
(Figure 3.4.9). This suggests that the Mehlich 3 extractant <strong>and</strong> probably other conventional<br />
soil test methods are reliable indicators o f K nutritional requirements o f flood-<br />
irrigated rice. Additional calibration <strong>and</strong> correlation data are needed to improve our<br />
confidence in current soil test critical levels for K, fertilization recommendations, <strong>and</strong><br />
soil test methods.<br />
The recent occurrence o f K deficiency in the southern rice belt is believed to be<br />
related primarily to the cultivation o f higher-yielding rice <strong>and</strong> soybean cultivars that<br />
deplete the soil o f K m ore rapidly. Higher yields certainly would remove more K in<br />
the harvested grain <strong>and</strong> in turn deplete the soil o f K m ore quickly. It is also possible<br />
that some rice cultivars require a higher concentration o f K in the soil. In either<br />
case, an adjustment in soil test recommendations <strong>and</strong> an increase in K fertilization<br />
may have to be made. Additionally, K deficiencies have been rather com m on in areas<br />
believed to have soil salinity problems. Depletion o f soil K was hastened because<br />
growers often avoided direct application of K fertilizer to rice for fear o f aggravating a<br />
salinity problem. In Arkansas, approximately 64% o f the 1996-1997 soil samples from<br />
I ■,<br />
! ,<br />
Figure 3.4.9. Relationship beween Mehlich 3-extractable K for silt loam soils<br />
in Arkansas <strong>and</strong> rice whole-plant tissue K concentration otthe midtillering<br />
{approximately 14 days after the five-leaf stoge] growth stage. Each data point<br />
represents the mean rice tissue concentration of four replications of a 0-kg k<br />
fertilizer per hectare treatment In fertilizer studies. (From unpublished data of N.<br />
A. Slaton, C. E. Wilson, Jr., <strong>and</strong> R. i. Norman.)
372 Production<br />
l i .i i<br />
ii'-^'i; '<br />
m<br />
rice <strong>and</strong> irrigated soybean fields tested were below 246 kg K/ha with the Mehlich 3<br />
extraction method (D elo n g et al., 1999). In California, rice is grown in a water-seeded<br />
monoculture predominately on clay soils, but some rice is grown on coarser-textured<br />
soils. Potassium deficiency has been observed on some o f the coarser-textured soils<br />
where rice straw was baled <strong>and</strong> removed following harvest. <strong>Rice</strong> straw can contain an<br />
appreciable amount of K, <strong>and</strong> if removed from the field, should be accounted for in<br />
K fertilization practices.<br />
Potassium deficiency in rice is typically observed between panicle initiation <strong>and</strong><br />
heading as a chlorosis o f the older leaves. Potassium deficiency is m ost worrisome<br />
when it occurs around panicle initiation, because this is when the deficiency affects<br />
rice yield most severely <strong>and</strong> is the m ost difficult time to diagnosis symptoms correctly.<br />
At this time, the initial deficiency symptoms o f chlorosis on the older leaves are difficult<br />
to differentiate from N-deficiency symptoms or the yellowing that may occur<br />
before plants make the transition from vegetative to reproductive growth. <strong>Rice</strong> that is<br />
K deficient may fail to “green up” after application o f midseason N. If the deficiency<br />
is not corrected, the rice leaves will develop severe brown leaf spot (Bipolris oryzae)^<br />
causing the field to change to a reddish-brown color due to the disease infestation (Slaton<br />
et al., 1995). Other opportunistic diseases, such as stem rot (Sderotium oryzae)y<br />
scab {Fusarium graninearum), black kernel {Curvalria lunata), <strong>and</strong> Fusarium sheath<br />
rot {Fusarium proliferatum) will also infest K-deficient leaves, stems, <strong>and</strong> panicles,<br />
resulting in additional yield loss. Deficiency symptoms may be m ost dramatic in<br />
levée ditches because the rice is growing in a deep flood <strong>and</strong> rooted in subsoil that<br />
is low in K. Soil K concentration is usually highest in the top 5 cm o f soil <strong>and</strong> declines<br />
with increasing depth. The upper ^rice leaves may develop a dark green color from K<br />
deficiency, while the lower leaves nearly always show chlorotic leaf margins <strong>and</strong> tips.<br />
The lower leaves o f K-deficient plants may turn necrotic <strong>and</strong> die. The extent o f lower<br />
leaf death is dependent on the severity o f the K deficiency.<br />
Once visual symptoms o f a deficiency have been displayed, it is best to verify the<br />
diagnosis with plant analysis. The rice Y-leaf has been shown to be a good indicator of<br />
the nutrient status o f the rice plant, <strong>and</strong> Sedberry et al. (1987) suggested that the rice<br />
Y-leaf critical concentration for K was 1.5% at panicle differentiation. In California,<br />
the suggested critical Y-leaf values are 1 .4 ,1 .2 ,1 .0 , <strong>and</strong> 1.0% at the midtillering, maximum<br />
tillering, panicle initiation, <strong>and</strong> flag leaf growth stages (Hill et ah, 1992). Tissue<br />
analysis comparing whole-plant K concentrations o f rice showing K-deficiency symptoms<br />
to those not showing deficiency symptoms suggest that whole-plant analysis is<br />
adequate for correct diagnosis o f plant K nutritional status (Table 3.4.9). Sampling<br />
individual leaves at the late boot stage shows that tissue K concentration decreases as<br />
leaf age increases. A tissue K concentration gradient normally occurs among leaves<br />
o f plants that are both K sufficient <strong>and</strong> deficient. However, the decline in tissue K<br />
concentration is greatest in plants that are K deficient. Potassium-deficient plants also<br />
tend to have higher Na, Mg, <strong>and</strong> Zn concentrations <strong>and</strong> have a greater N/K ratio for<br />
whole-plant <strong>and</strong> individual leaf samples. Soil samples taken from flooded rice fields<br />
during the late boot stage or shortly after draining for harvest have failed to show significant<br />
differences in exchangeable K from K-sufficient <strong>and</strong> K-deficient areas within<br />
a field. This is probably due to the high total K content o f the rice straw. O ther nutrient<br />
deficiencies may influence tissue K concentration <strong>and</strong> can lead to misinterpretation<br />
o f tissue analysis results. Thus tissue analysis results should be used along with plant<br />
symptoms <strong>and</strong> field characteristics to make the correct diagnosis.
Soil Fertilization <strong>and</strong> Mineral Nutrition in U.S. Mechanized <strong>Rice</strong> Culture 373<br />
TABLE 3,4.9.<br />
T issu e A n a ly s is o f K -D e fic ie n t B e n g a l R ice a t th e Late B o o t S ta g e fro m a F ie ld S h o w in g<br />
M o d e r a t e K -D e fic ie n c y S y m p to m s<br />
Plant<br />
Part<br />
Nutritional<br />
Status<br />
A n alysis by Percent<br />
A n alysis by W eight (m g/kg)<br />
N P K Ca M g S N a Fe M n Zn Cu<br />
Whole Sufficient 1.71 0.33 1.64 0.26 0.15 0.15 3 338 148 593 26.3 12.6<br />
Deficient 2.08 0.35 1.05 0.34 0.18 0.18 7389 258 643 33.6 13.4<br />
Flag Sufficient 3.15 0.28 1.81 0.22 0.15 0,22 186 86 244 30.2 12.5<br />
Deficient 2.99 0.30 1.50 0.20 0.17 0.22 307 83 210 36.3 28.1<br />
Flag-1 Sufficient 3.60 0.29 1.78 0.32 0.15 0.22 232 91 279 23.2 16.5<br />
Deficient 3.51 0,30 1.50 0.31 0.17 0.23 654 97 256 27.3 20.6<br />
Flag-2 Sufficient 3.35 0.31 1.78 0.38 0.15 0.20 308 94 341 18.5 14.9<br />
Deficient 3.65 0.33 1.06 0.34 0.18 0.23 1055 94 297 21.3 7.6<br />
Flag-3 Sufficient 2.91 0.34 1.98 0.42 0.17 0.18 367 78 449 16.7 13.7<br />
Deficient 3.27 0.37 1.03 0.48 0.20 0.20 1376 116 451 17.3 9.1<br />
Flag-4 Sufficient 2.56 0.34 1.94 0.70 0.19 0.16 568 93 711 18.0 16.6<br />
Deficient 3.18 0.41 1.19 0.60 0.25 0.19 1483 156 598 18.7 14.1<br />
Flag-5 Sufficient 1.72 0.24 1.94 0.94 0.23 0.15 655 189 1222 31.2 25.2<br />
Deficient 2.61 0.47 1.19 0.80 0.27 0.17 1360 218 833 25.5 20.8<br />
Flag-6 Sufficient 2.38 0.31 1.63 0.85 0.21 0.16 654 493 1379 36.7 29.9<br />
Deficient 1.89 0.36 0.92 0.98 0.25 0.16 1281 666 1357 40.3 29.7<br />
Stems Sufficient 0.88 0.33 1.23 0.11 0.11 0.11 7 002 181 596 31.9 10.3<br />
Deficient 1.41 0.40 0.87 0.10 0.13 0.13 11244 245 396 39.1 9.1<br />
Source: Unpublished data of N. A. Slaton.<br />
SULFUR BEHAVIOR, NUTRITION, AND FERTILIZATION<br />
Sulfur (S) behavior in flooded soils is quite dynamic,* sulfur is involved in transformations<br />
from inorganic <strong>and</strong> organic forms through m ineralization-im m obilization<br />
reactions <strong>and</strong> oxidized <strong>and</strong> reduced forms through oxidation-reduction reactions,<br />
similar to those o f N. These consequential transformations govern the availability o f<br />
S to rice.<br />
Sulfur Forms <strong>and</strong> Behavior in Flooded <strong>Rice</strong> Soils<br />
Sulfur is present in the soil in both inorganic <strong>and</strong> organic forms, but exists predominately<br />
as organic S. The organic S fraction in soil is im portant since it regulates the<br />
mineralization o f plant-available S, which is the sulfate {SO 4“ ) ion. The SO4 supply<br />
to plants is largely dependent on the mineralization o f SO4 from the soil organic<br />
matter or crop residues (Tisdale et al., 1993). Thus S, like N, undergoes cycling in soil<br />
by microorganisms as it is continually being immobilized into the organic fraction<br />
<strong>and</strong> mineralized back to SO4 under aerobic conditions <strong>and</strong> sulfides under anaerobic<br />
conditions. The C/S ratio of plant <strong>and</strong> animal residues govern whether there is net<br />
S mineralization or immobilization. Decomposing material with a wide C/S ratio<br />
will result in net S immobilization, <strong>and</strong> those with a narrow CIS ratio will result in a<br />
net S mineralization. M ost fresh plant residues have narrow C/S ratios <strong>and</strong> result in<br />
S mineralization.
Production<br />
p lil'<br />
llhi<br />
Under anaerobic conditions that exist in flooded rice soils, the SO4 present will<br />
normally be used as an electron acceptor by soil microorganisms <strong>and</strong> be reduced to<br />
sulfides such as hydrogen sulfide (H 2S) dissolved in the soil solution, insoluble metal<br />
sulfides (i.e„ Fe, Mn, Cu, or ZnS), or as H 2S gas, which forms under conditions of<br />
high sulfide <strong>production</strong>, low pH, <strong>and</strong> low mineral content o f soil (Patrick et al„ 1985).<br />
Hydrogen sulfide gas <strong>production</strong> is a loss mechanism for S, similar to denitrification<br />
loss o f N as N2 gas. Metals in the soil help to restrain H 2S <strong>production</strong> <strong>and</strong> keep it<br />
to a minimum. If the H 2S formed is not subsequently precipitated by iron (Fe) or<br />
other metals, it can build up to high enough concentrations to be toxic to the rice<br />
plant. Soils low in Fe, such as high organic or s<strong>and</strong>y soils, are more prone to H 2S<br />
<strong>production</strong>. M ost soils used for rice <strong>production</strong> in the United States are silt loam<br />
<strong>and</strong> clayey soils with low-to-m oderate organic matter levels <strong>and</strong> large amounts o f Fe,<br />
which reacts with the sulfide to form amorphous FeS <strong>and</strong> eventually, pyrite (FeS2).<br />
The <strong>production</strong> o f H 2S in a waterlogged soil is thus dependent on the am ount of<br />
Fe <strong>and</strong> organic matter present. Damage from H 2S toxicity in U.S. rice <strong>production</strong> is<br />
a minor problem, confined to areas or corners o f fields where large amounts o f the<br />
previous crop residue has collected <strong>and</strong> raised the organic content o f the soil <strong>and</strong><br />
lowered the redox potential to levels that result in H 2S <strong>production</strong>.<br />
The availability o f SO4 for uptalce by rice is governed by the processes mentioned<br />
previously; however, the m ineralization-im m obilization reactions, the S content of<br />
the soil organic fraction, <strong>and</strong> m ost important, the permeability o f the soil ordinarily<br />
have a greater im pact on S availability to rice. The primary source o f SO4 in flooded<br />
soil comes from mineralization o f organic matter <strong>and</strong> diffusion o f sulfide to the root<br />
surface, where it is oxidized to SO4 for uptake by the rice (Engler <strong>and</strong> Patrick, 1975).<br />
The silt loam <strong>and</strong> clay soils on whidi rice is grown in the United States have low to<br />
moderate levels o f organic matter <strong>and</strong> low permeability that limits leaching losses.<br />
Even though the silt loam soils have low amounts of organic matter, they appear to<br />
be adequate enough in organic matter content to mineralize sufificient amounts of<br />
inorganic S, along with S supplied in the irrigation <strong>and</strong> rainwater, to make S deficiency<br />
rare on these soils. Irrigation water can contain a range o f SO4 concentrations. Surface<br />
water sources in Arkansas contain an average o f 15.5 mg S0 4 -S/L (± 1 6 .0 mg S O 4-S/L)<br />
<strong>and</strong> groundwater sources averaged 50.3 mg SO 4-S/L (± 3 7 .9 mg SO4-S/V) (M oore et<br />
al., 1992a).<br />
Most o f the S deficiencies are found on s<strong>and</strong>y <strong>and</strong> s<strong>and</strong>y loam soils that possess<br />
very low amounts o f organic matter <strong>and</strong> have high permeability; precision-graded<br />
fields that have had their topsoil removed <strong>and</strong> consequently, have low organic matter;<br />
<strong>and</strong> fields that are flooded continuously for rice <strong>production</strong> <strong>and</strong> waterfowl habitat<br />
(Wilson et ah, 2001), The s<strong>and</strong>y <strong>and</strong> s<strong>and</strong>y loam soils mineralize low amounts of<br />
inorganic S, <strong>and</strong> tlie two principal forms o f inorganic S that exist in flooded rice soils,<br />
sulfide <strong>and</strong> tlie plant-available-form SO4" , are anions subject to significant leaching<br />
losses when soils with high permeability are flooded for rice <strong>production</strong>. Similarly,<br />
precision-graded fields that do not have their topsoil returned have low organic m atter<br />
<strong>and</strong> mineralize low amounts o f inorganic S. Sulfur deficiency observed in rice<br />
fields previously flooded for waterfowl habitat could be caused by two S-loss mechanisms.<br />
Fields flooded after harvest contain substantial amounts of decomposable crop<br />
residue that could possibly cause the soil to become sufficiently reduced during warm<br />
periods in the off-season to result in H jS volatilization, <strong>and</strong>/or if the soil is permeable<br />
enough, the flood could induce S leacliing losses. Typically, H 2S volatilization is not a
Soil Fertilization <strong>and</strong> Mineral Nutrition in U.S. Mechanized <strong>Rice</strong> Culture 375<br />
significant loss mechanism, because the rice soils in the United States do not become<br />
sufficiently reduced for H 2S formation.<br />
Sulfur Nutrition, Fertilization Practices, <strong>and</strong> Diagnosis of Deficiency<br />
In the United States, rice normally does not require S fertilizer, due to the low permeability<br />
o f the soils, coupled with adequate amounts o f S naturally provided from<br />
mineralization from soil organic matter <strong>and</strong> extraneous S sources, such as irrigation<br />
water <strong>and</strong> precipitation. Sulfur deficiencies normally occur after establishing the perm<br />
anent flood during active tillering <strong>and</strong> again during late reproductive growth when<br />
the plant is producing biom ass rapidly <strong>and</strong> the panicle is developing. Sulfur-deficiency<br />
symptoms during vegetative growth include chlorosis o f the entire rice plant, starting<br />
with the younger leaves, reduced tillering, <strong>and</strong> stunted growth. Although chlorosis<br />
may start with the younger leaves, this distinction may not be observed, as S-deficient<br />
rice can become uniform ly chlorotic quite rapidly. W hen S deficiency occurs during<br />
the rice reproductive growth stage or about 2 to 3 weeks before heading, deficiency<br />
symptoms are observed in the top two or three leaves. Leaves o f deficient rice plants<br />
have alternating vertical dark <strong>and</strong>/or yellow (chlorotic) streaks that began at the tip<br />
o f the leaf <strong>and</strong> extend toward the leaf base. The bottom two to three leaves almost<br />
always appear norm al. During flag leaf exsertion, the flag leaf may show less severe<br />
symptoms than the other top two to three leaves. But once fully exserted, the flag leaf<br />
eventually develops alternating dark <strong>and</strong> yellow strealcs. M aturity o f the rice will be<br />
delayed if S deficiency is not corrected in a timely manner.<br />
Sulfur-deficiency symptoms during the rice vegetative growth stage appear similar<br />
to those o f N. The difference is N-deficiency symptoms begin as a yellowing o f<br />
the older leaves. Since visual symptoms are difficult to distinguish from N deficiency,<br />
plant tissue analysis is often required for positive identification. M inim um concentrations<br />
o f S in the rice plant for optim um growth during active tillering <strong>and</strong> panicle<br />
initiation are 0.17 <strong>and</strong> 0.15% , respectively (Bell <strong>and</strong> Kovar, 2000). <strong>Rice</strong> crop uptake<br />
<strong>and</strong> removal o f S are approximately 26 <strong>and</strong> 9 kg S/ha, respectively, based on an average<br />
yield of 9000 kg/ha <strong>and</strong> total aboveground biomass (grain <strong>and</strong> straw) o f 20,000 kg/ha.<br />
Thus the rice plant does not require a large amount o f S for optim um growth.<br />
Sulfur fertilizer usually is applied in the plant-available SO4 form . Ammonium<br />
sulfate [(NH4)2S 0 4 ; 24% S] is most often used to alleviate or prevent a S deficiency<br />
in rice. Experience has shown that for m ost S-deficient soils a 112-kg/ha application<br />
o f (NH4)2S 0 4 , which supplies 27 kg S0 4 -S/ha, is sufficient for optim um rice growth<br />
<strong>and</strong> <strong>production</strong>. Although this appears to be a marginal rate, along with the S supplied<br />
in irrigation water <strong>and</strong> precipitation, this rate is ordinarily more than adequate. The<br />
best tim e to apply (NH4)2S 04 is early in die season with the N fertilizer at preflood<br />
application time, when the rice plant is beginning to tiller (De Datta, 1981). On s<strong>and</strong>y<br />
soils with high permeability, an additional application at midseason is often required,<br />
especially on fields with a <strong>history</strong> o f S deficiency occurring during late reproductive<br />
growth. Am m onium sulfate usually is recommended on s<strong>and</strong>y soils, because they may<br />
suffer from both S <strong>and</strong> N loss due to leaching. Precision-graded soils suffer from<br />
many nutrient abnormalities in addition to S, because o f organic matter removal<br />
<strong>and</strong> the exposure o f subsoils deficient in some elements <strong>and</strong> toxic in others. Poultry<br />
litter <strong>and</strong> at times gypsum (CaS0 4 , 18% S) are applied to these soils for reclamation.
376 Production<br />
i|!<br />
Ilih<br />
Soils that have had continuous waterlogging due to rice <strong>production</strong> <strong>and</strong> waterfowl<br />
habitat ordinarily require only a single application o f (NH4)2S0 4 . This is probably<br />
because the soils contain sufficient amounts o f organic matter <strong>and</strong> receive enough S<br />
from extraneous sources for optimum rice growth if it were not for the prolonged<br />
flooding. To prevent or minimize S deficiencies in fields used for waterfowl habitat,<br />
it is best to drain them several m onths prior to seeding rice, so they can aerate, to<br />
allow reduced <strong>and</strong> organic S to be transformed to SO 4. Other S fertilizers that have<br />
seen some commercial use are potassium sulfate (K 2SO4; 17% S) <strong>and</strong> elemental S (S®;<br />
90% S). Elemental S has proven to be effective at reducing soil pH <strong>and</strong> improving rice<br />
productivity on calcareous soils with a <strong>history</strong> o f high-pH-related problems (Slaton<br />
et al., 2001a). Elemental S is also an excellent source o f S, but it should be applied in<br />
the fall or winter to allow the product to be oxidized to the plant-available SO 4 form.<br />
MICRONUTRIENT AND OTHER ESSENTIAL ELEMENT BEHAVIOR,<br />
NUTRITION, AND FERTILIZATION<br />
Hi-<br />
The met^l micronutrients that have documented deficiencies in U.S. rice <strong>production</strong><br />
are zinc (Zn), iron (Fe), <strong>and</strong> manganese (M n). These three micronutrients are as<br />
important for plant growth <strong>and</strong> development as any nutrient; they are just needed<br />
in lesser amounts. This is fortunate since the quantity o f these micronutrients in<br />
soil that are in plant-available form are quite low compared with other nutrients.<br />
Flooding a soil has a marked effect on the availability o f the Zn, Fe, <strong>and</strong> M n. Several<br />
means by which flooding can affe ct the availability o f these three m etal micronutrients<br />
are ( 1) increased solubility of compounds via the dilution effect o f the excess water;<br />
(2) the pH changes associated with oxidation-reduction reactions, which can cause<br />
nutrients to be transformed to soluble or insoluble forms; (3) increased availability<br />
due to increased mobility o f nutrients in the saturated sod; <strong>and</strong> (4) changes in the<br />
oxidation-reduction status o f the nutrients, which influences their solubility (Patrick<br />
et al., 1985). Flooding also influences the temperature o f the soil. The availability of<br />
these three metal m icronutrients is rather temperature dependent, with availability<br />
<strong>and</strong> plant uptake decreasing as temperature decreases. See Chapter 3.3 for details concerning<br />
the influence o f flooding on the m oderation o f soil temperature. In the following<br />
sections we discuss the behavior, nutrition, <strong>and</strong> fertilization o f the aforementioned<br />
metal micronutrients as well as o f the few otlier essential nutrients required by rice<br />
with documented deficiencies in U.S. rice <strong>production</strong>.<br />
Zinc Forms <strong>and</strong> Behavior in Flooded <strong>Rice</strong> Soils<br />
I t -<br />
The conceptual forms o f Zn in soils are: solution Zn^+; adsorbed Zn on clay surfaces,<br />
organic matter, carbonates, <strong>and</strong> oxide minerals; organic complexed Zn; <strong>and</strong> Zn in<br />
primary <strong>and</strong> secondary minerals. AH o f these forms o f Zn are in equilibrium with<br />
solution Zn^+, which is the plant-available form of Zn. Soil characteristics <strong>and</strong> cultural<br />
■management practices that affect Zn availability <strong>and</strong> deficiency have been described<br />
by numerous researchers in the United States (Westfall et al., 1971; Wells et a l, 1973;<br />
Sedberry et a l, 1978). Although many soil chemical <strong>and</strong> physical characteristics have<br />
been linked to the occurrence of Zn deficiency, definitive criteria to predict rice yield
Soil Fertilization <strong>and</strong> Mineral Nutrition in U.S. Mechanized <strong>Rice</strong> Culture 377<br />
response to 2 n fertilization from routine soil testing is still lacking. Thus criteria<br />
for recommending Zn fertilizer application to rice differs among the rice-growing<br />
states. Zinc deficiencies are com m on to soils that have been disturbed from l<strong>and</strong>leveling<br />
procedures <strong>and</strong> on undisturbed soils with high soil pH (Westfall et ah, 1971),<br />
L<strong>and</strong> leveling removes topsoil that contains the bulk of soil nutrients <strong>and</strong> exposes<br />
subsoils that may have poor fertility or undesirable characteristics (e.g., low organic<br />
matter, textural changes, sodic subsoils, <strong>and</strong> pH changes). Organic matter is very<br />
im portant to Zn availability, as well as Fe <strong>and</strong> Mn availability, because the dynamics<br />
o f chelation with organic compounds facilitates the solubility <strong>and</strong> transport o f metal<br />
micronutrients in the soil solution. However, the m ost im portant soil characteristic<br />
recognized by all states as a factor that influences Zn deficiency is soil pH. Zinc<br />
deficiencies in rice are m ost com m on when the soil pH is near neutrality or above.<br />
This is underst<strong>and</strong>able since hydroxides <strong>and</strong> carbonates present in high-pH soil form<br />
metastable compounds with Zn. Hence Zn availability is quite pH dependent <strong>and</strong><br />
decreases in solubility 100-fold for every 1-unit increase in pH (Patrick et ah, 1985).<br />
Sedberry et al. (1980) found that soil pH was the m ost highly correlated single factor<br />
associated with rice yield response to Zn fertilization. Others have also shown that soil<br />
pH <strong>and</strong> exchangeable calcium (Ca) are typically greater in areas o f the field where Zn-<br />
deficiency symptoms are observed (Westfall et al., 1971; Slaton et al., 1996). Causes of<br />
Zn deficiency in commercial rice fields are ( 1) use o f irrigation water high in CaHCOa,<br />
(2) excessive lime rate, (3) nonuniform lime distribution, <strong>and</strong> (4) naturally occurring<br />
calcareous soils. Other factors that have been linked to the occurrence o f Zn deficiency<br />
include organic matter (Yoon et al., 1975); high HCOy concentrations in both soil <strong>and</strong><br />
irrigation water; rice cultivar (Giordano <strong>and</strong> Mortvedt, 1974; Wells 19.80); soil redox<br />
(Sajwan <strong>and</strong> Lindsey, 1986); irrigation method or soil moisture regime (Giordano <strong>and</strong><br />
Mortvedt, 1972; Bashir, 1999); air, soil, <strong>and</strong> water temperature (Place et al., 1971a;<br />
Sedberry et al., 1978); salinity (Bashir, 1999); <strong>and</strong> soil texture (Wells, 1980).<br />
Soil solution Zn^"*" concentration is influenced by many soil chemical properties<br />
<strong>and</strong> may either increase or decrease after flooding (Patrick et al., 1985). Yoon et al.<br />
(1975) showed that soil solution Zn^"*' concentration was not static during the growing<br />
season, was negatively correlated with soil solution pH <strong>and</strong> H CO 3 concentration, <strong>and</strong><br />
was positively correlated with Y-leaf Zn concentration as a function o f time. However,<br />
Gilmour (1977a) concluded that soil solution Zn concentration was not consistently<br />
correlated with plant Zn measurements. The role o f organic chelation in Zn solubility<br />
<strong>and</strong> availability is probably somewhat responsible for this lack o f correlation. But it<br />
does illustrate that the availability <strong>and</strong> subsequent uptake o f Zn by rice is governed by<br />
numerous soil chemical properties <strong>and</strong> interactions within the rhizosphere.<br />
Zinc Nutrition, Fertilization Practices, <strong>and</strong> Diagnosis of Deficiency<br />
Zinc is the most limiting m icronutrient in U.S. rice <strong>production</strong>. Although deficiencies<br />
o f M n <strong>and</strong> Fe have also been documented, Zn limits rice growth on significantly<br />
more cropl<strong>and</strong> than all other m icronutrients combined. Zinc deficiency o f rice was<br />
first recognized in the United States during the late 1960s at about the same time<br />
tliat it was diagnosed in other rice-producing areas of the world. Zinc deficiency<br />
had occurred before this time but previously was misdiagnosed as other nutrient<br />
problems. Unfortunately, the inconsistency o f obtaining Zn deficiencies in research
378 Production<br />
til<br />
plots, <strong>and</strong> subsequent rice growth <strong>and</strong> yield responses to Zn fertilization, has inhibited<br />
progress with the development of Zn fertilization recommendations. Following is a<br />
summary o f our current laiowledge o f fertilization practices, soil fertility, <strong>and</strong> rice<br />
plant micronutrient nutrition based on research conducted in the United States.<br />
Zinc-deficiency symptoms o f seedling rice have been described by researchers in<br />
Arkansas (Wells et ah, 1973), California (Mikkelsen <strong>and</strong> Br<strong>and</strong>on, 1975), Louisiana<br />
(Sedberry et al., 1978), <strong>and</strong> Texas (Westfall et al., 1971) <strong>and</strong> are relatively consistent<br />
across geographic areas <strong>and</strong> cultural management practices. The visual symptoms<br />
common to seedling Zn deficiency may include (1) basal chlorosis o f new (youngest)<br />
leaves, (2) midrib of lower (oldest) leaves becom ing yellow to white, (3) floating leaves<br />
(loss ofleafturgidity), (4) bronzing (reddish-brown colored blotches) o f older leaves,<br />
(5) inhibition o f tillering, (6) eventual st<strong>and</strong> loss under flooded conditions, (7) stacked<br />
leaf collars, <strong>and</strong> ( 8) delayed maturity. M ost descriptions o f Zn deficiency suggest<br />
that the first visual signs normally occur after flood establishment in dry-seeded,<br />
delayed-flood rice <strong>production</strong> (Sedberry et al., 1978). However, Zn nutrition is probably<br />
limiting prior to flood establishment, <strong>and</strong> symptoms can be found upon close<br />
examination o f seedlings at this time, especially under severe Zn-deficient conditions<br />
(Westfall et'al, 1971). <strong>Rice</strong> plants of any age may exhibit Zn-deficiency symptoms. At<br />
heading, panicles may remain upright <strong>and</strong> resemble straighthead if the Zn deficiency<br />
is not corrected (Sedberry et a l, 1978). The potential yield loss from Zn deficiency<br />
o f flooded rice can approach 100% , due to st<strong>and</strong> loss, if Zn deficiency is severe <strong>and</strong><br />
left uncorrected. Based on comparison of untreated checks to Zn fertilizer treatments<br />
in research studies where rice response to Zn fertilization has been observed, Zn<br />
deficiency normally accounts for 10 to 60% yield loss in U.S. rice. Zinc deficiency<br />
normally occurs early, during vegetative growth, <strong>and</strong> very little if any yield loss may<br />
be experienced if Zn deficiency o f seedling rice is quickly corrected <strong>and</strong> proper management<br />
is followed. Flooding Zn-deficient rice usually results in a rapid <strong>and</strong> dramatic<br />
expression o f the Zn-deficiency symptoms described. Complete removal o f the flood-<br />
water is required for plant recovery when Zn deficiency is severe. Recommendations<br />
for rescue situations o f Zn-deficient rice are to ( 1) drain the flood, (2) dry the soil,<br />
(3) watch for evidence o f new shoot (emerging green leaf) <strong>and</strong> root (white roots)<br />
growth, (4) apply a Zn fertilizer solution to rice foliage, (5) apply am m onium sulfate,<br />
<strong>and</strong> (6) reflood. Several days should separate foliar Zn application <strong>and</strong> reestablishm<br />
ent of the flood, to allow time for recovery <strong>and</strong> to prevent a reoccun*ence o f Zn<br />
deficiency. Application o f am m onium sulfate is for growth stimulation <strong>and</strong> to account<br />
for some N loss resulting from draining <strong>and</strong> drying the soil. Am monium sulfate is<br />
used instead o f urea because urea causes a b rief increase in soil pH from hydrolysis<br />
of the urea fertilizer, which may further aggravate the Zn deficiency. Additionally,<br />
research has shown that in the absence o f Zn fertilization, rice yields were higher<br />
when ammonium sulfate was the N source rather than urea (Wells et al., 1973). Foliar<br />
application o f Zn fertilizer without draining the flood may be practical only when Zn<br />
deficiency is mild <strong>and</strong>/or found quickly.<br />
The symptoms associated with Zn deficiency were described by numerous researchers<br />
prior to correct identification o f Zn as the m ost limiting nutrient (Place,<br />
1969). Originally, Zn deficiency was misdiagnosed as Fe deficiency, because soil application<br />
of large amounts o f iron sulfate tended to alleviate seedling chlorosis. However,<br />
application o f iron sulfate to the soil in large amounts can relieve Zn deficiency by<br />
reducing soil pH <strong>and</strong> in turn increasing plant-available solution Zn from dissolution
Soil Fortilization <strong>and</strong> Mineral Nutrition in U.S. Mechanized <strong>Rice</strong> Culture 379<br />
o f zinc hydroxides <strong>and</strong> carbonates. Also, trace amounts o f Zn may have been present<br />
in the iron sulfate <strong>and</strong> when applied at large rates could supply sufficient amounts o f<br />
Zn (B.R. Wells, personal com m unication).<br />
Routine plant analysis is appropriate <strong>and</strong> useful for aiding in the correct diagnosis<br />
o f Zn deficiency in the field. Confirmation o f the nutrient-deficiency diagnosis<br />
based on deficiency symptoms is encouraged because soil conditions conducive for<br />
Zn deficiency are also likely to result in limiting amounts o f other nutrients that<br />
may inhibit rice growth. Symptoms typically associated with Zn deficiency, such as<br />
bronzing, reduced tillering, <strong>and</strong> leaf chlorosis, are also com m on for rice stressed by<br />
other factors, such as Fe, P, <strong>and</strong> salinity. Correct interpretation o f tissue analysis results<br />
depends on correct sampling procedures <strong>and</strong> sample preparation. Since Zn is a m i<br />
cronutrient, sample contam ination is possible if samples are not cleaned thoroughly.<br />
Samples taken from grower fields m aybe contaminated by soil, Fe precipitation from<br />
irrigation water, or a recent fertilizer application. Error from sample contamination<br />
can be effectively reduced by cleaning tissue in mild detergent or by thorough rinsing<br />
with dilute acid <strong>and</strong> deionized water (Wells, 1980).<br />
The literature is very consistent on the Zn values considered sufficient for rice.<br />
Althougli the plant part sampled is extremely critical for correct interpretation o f<br />
plant nutritional status o f some elements, it is less im portant for the diagnosis o f<br />
Zn deficiency in rice. Since Zn deficiency normally affects only seedling rice, whole<br />
plants are much easier to sample <strong>and</strong> prepare for analysis than is the youngest mature<br />
leaf (Y-leaf) . Although Zn is a nonm obile element, Gilmour (1977a) showed that Zn<br />
concentration o f whole plants or individual leaves were not significantly different.<br />
Seedling rice with tissue Zn concentrations o f < 15, 15 to 20, <strong>and</strong> > 2 0 mg Zn/kg<br />
are considered deficient, low (possibly deficient), <strong>and</strong> sufficient, respectively, during<br />
vegetative growth. Sedberry et al. (1987) also suggested the same values as deficient,<br />
low, <strong>and</strong> sufficient for the Y-leaf at a 2'-mm panicle length (i.e., panicle differentiation).<br />
W hen comparing norm al plants to unhealthy plants in a field o f rice, tissue<br />
concentrations o f several other elements can be useful in diagnosing Zn deficiency.<br />
Zinc-deficient rice tends to have higher-than-norm al concentrations o f Ca, Cu, Mg,<br />
Fe, <strong>and</strong> N <strong>and</strong> lower concentrations o f M n, K, <strong>and</strong> Zn (Table 3.4.10). Calculation of<br />
a P/Zn ratio (with like units, such as mg/kg or % ) can also be useful in diagnosis. A<br />
P/Zn ratio o f whole plant or Y-leaf tissue < 1 5 0 suggests that another element m aybe<br />
limiting growth, <strong>and</strong> a P/Zn ratio > 1 5 0 suggests that Zn deficiency m aybe the cause<br />
o f poor growtli.<br />
Soil test Zn has also been associated with the occurrence o f Zn deficiency o f rice<br />
<strong>and</strong> other crops. However, few states have used soil test Zn as the criterion for Zn<br />
fertilizer recommendations, primarily because early research showed that soil pH was<br />
easier to measure <strong>and</strong> was more reliable than soil test Zn for predicting response<br />
to fertilization. The availability o f Zn decreases about 100 times for each 1.0-unit<br />
increase in soil pH between pH 6.0 <strong>and</strong> 8.0 (Patrick et al., 1985). Additionally, early<br />
research efforts were conducted on soils that were uniformly low in Zn, resultmg<br />
in poor correlations o f growth responses to soil test Zn. Use o f soil pH alone does<br />
not account for any residual benefit of recent Zn fertilizer application to future crop<br />
use. Use o f soil test Zn for Zn fertilizer recommendations is preferred since it should<br />
account for the residual benefits o f a single, previous Zn fertilizer application to future<br />
crops. In Arkansas, years o f applying Zn fertilizer from recommendations based on<br />
soil texture <strong>and</strong> pH, regardless o f soil test Zn level, has resulted in many alkaline
380 Production<br />
T A B LE 3.4 .1 0 .<br />
C o m p a riso n o f T iss u e A n a ly s is o f Z n -D e fic ie n t a n d Z n -S u ffic ie n t C o c o d rie <strong>Rice</strong> o t th e<br />
M id t iile r in g G ro w th S t a g e<br />
Plant<br />
Part<br />
Nutritional<br />
Status<br />
Analysis by Percent<br />
Analysis by Weight (mg/kg)<br />
N P K Ca liflg S Na Fe Mn Zn Cu<br />
P/2N<br />
Ratio<br />
Whole Sufficient 3.35 0.21 2.44 0.28 0.14 0.21 1573 433 764 18.1 6.3 116<br />
Deficient 3.98 0.18 1.81 0.34 0.16 0.22 1354 768 576 8.4 7.3 214<br />
Top leaf Sufficient 4.39 0.30 1.95 0.22 0.18 0.26 409 1978 660 25.8 5.9 121<br />
Deficient — 0.30 1.90 0.33 0.22 0.28 492 147 456 25.0 9.0 120<br />
Yleaf Sufficient 4.35 0.23 1.86 0.39 0.18 0.25 345 120 936 15.6 6.8 147<br />
Deficient 4.86 0,21 1.19 0.71 0.26 0.27 400 156 780 10.8 9.5 194<br />
Y-1 Sufficient 4.53 0.21 1.78 0,64 0.20 0.24 311 116 1254 11.1 7.2 '—<br />
Deficient 4.78 0.20 1.32 0.60 0.24 0.27 442 144 616 11.1 9.7 —<br />
Y-2 Sufficient 4.49 0.20 1.59 0,89 0.21 0.26 337 173 1472 13.9 8.2 —<br />
Deficient 4.84 0.14 0.66 0.90 0.28 0.28 438 237 915 14.2 9.9 —<br />
Stems Sufficient 2.02 0.21 3.23 0.10 0.11 0.13 2691 418 489 21.2 4.7 —<br />
Deficient 3.53 0.21 2.61 0.11 0.10 0.19 1448 499 265 39.0 5.9 —<br />
Source: Unpublished data of N. A. Slaton,<br />
iii: f:<br />
soils that test high in Mehlich 3-extractable Zn. Critical soil test values o f 0.7 mg<br />
o f DTPA-extractable Zn per kilogram (Sedberry et al., 1978) <strong>and</strong> 1.5 mg o f Mehlich<br />
3-extractable Zn per kilogram (Liscano et al., 2000) have been suggested for rk e use<br />
in the southern U.S. rice belt. California recommends Zn fertilization when DTPA-<br />
extractable Zn is < 0.5 mg Zn/kg (Hill et al., 1992). Arkansas uses soil texture (silt<br />
<strong>and</strong> s<strong>and</strong>y loam soils), soil pH (soil water pH > 6.0), <strong>and</strong> M ehlich 3-extractable Zn<br />
(< 3.5 mg Zn/kg) as criteria to recommend Zn fertilization (W ilson et al., 2001).<br />
Placement o f Zn fertilizer is critical for efficient crop use <strong>and</strong> may differ among<br />
cultural seeding methods, tillage systems, <strong>and</strong> chemical fertilizer properties. Giordano<br />
<strong>and</strong> Mortvedt (1972) showed that rk e dry matter <strong>production</strong> o f flood-irrigated rice<br />
was greatest when Zn fertilizer was applied either to the soil surface or thoroughly<br />
incorporated before planting. Zinc applied in the general chemical forms o f Zn oxide<br />
(20 to 36% Zn), Zn sulfate (31 to 36% Zn), <strong>and</strong> Zn lignosulfonate (8 to 12% Zn) will<br />
move very little after soil application, but Zn-EDTA (8 to 10% Zn) may move within<br />
the soil profile following application (Giordano <strong>and</strong> Mortvedt, 1972; Mikkelsen <strong>and</strong><br />
Br<strong>and</strong>on, 1975).<br />
Zinc fertilization recommendations vary among the rice-producing states. The<br />
two primary methods o f Zn fertilization o f rice are broadcast application o f granular-<br />
inorganic Zn fertilizers prior to seeding <strong>and</strong> foliar application o f liquid Zn sources<br />
after seedling emergence. Preplant broadcast application o f most granular Zn fertilizers<br />
requires 11.0 kg Zn/ha for adequate distribution o f Zn fertilizer granules.<br />
In Arkansas, granular Zn fertilizers are recommended based on their water-soluble<br />
Zn content (Liscano et ah, 2000). Granular Zn fertilizers with less than 40 to 50%<br />
water-soluble Zn are not recommended for use. Other fertilizer properties, such as<br />
the concentration o f Zn (guaranteed analysis), the particle size, <strong>and</strong> density o f the<br />
fertilizer granule, also influence the fertilizer distribution <strong>and</strong> efficiency o f rice uptake<br />
<strong>and</strong> should be considered in recommendations. Inform ation on the duration o f the<br />
residual benefits o f a single large application o f Zn fertilizer is not known but is<br />
thought to last for several years. The primary advantage of soil application o f 11 kg<br />
Zn/ha is that Zn deficiency is prevented, some residual benefit can be expected to
Soil Fertilizalion <strong>and</strong> Mineral Nutrition in U.S. Mechanized <strong>Rice</strong> Culture<br />
3B1<br />
future crops, <strong>and</strong> the costs associated witli Zn fertilization may not be required for<br />
several years. Application costs for soil application o f Zn are generally small because<br />
Zn is com m only blended with other fertilizers intended for preplant application.<br />
Application o f 1.0 to 2.0 kg Zn/ha as liquid Zn solutions to rice foliage also are<br />
recommended. Foliar application o f Zn is usually very effective when Zn is applied<br />
before Zn nutritional stress occurs in dry-seeded, delayed-flood rice <strong>production</strong>. B e<br />
cause o f the low rate o f Zn used for foliar applications, Zn may be required each time<br />
that rice is grown in the crop rotation. Use o f liquid forms o f Zn fertilizer for preplant<br />
or preemergence applications at Zn rates similar to those recommended for foliar<br />
application have also been used with some success. Despite the lower use rates, costs<br />
associated with foliar applications o f Zn fertilizers are generally equal to preplant soil<br />
application o f Zn. Costs for foliar application o f Zn may vary, however, depending<br />
on whether other products (i.e., crop protection products) are tank mixed with the<br />
Zn <strong>and</strong> the source o f Zn. Chelated (i.e., Zn-EDTA) Zn sources are generally the most<br />
expensive. Liquid ZnS04 or highly water-soluble dry ZnS04 sources may be applied<br />
in solutions at a fraction of the cost o f chelated Zn materials. The primary benefit o f<br />
liquid Zn solution application to soil or rice foliage is the uniform distribution of Zn<br />
at relatively low use rates.<br />
A third method o f Zn fertilization is the application o f Zn directly to the rice<br />
seed. Commercial seed treaters usually treat seed with ZnO sources of Zn. Other<br />
chemical forms o f Zn are normally not used because tliey are not available in concentrated<br />
forms suitable for low-volume seed treatment or may reduce germination <strong>and</strong><br />
seedling vigor. Zinc-treated seed should contain 2.5 to 5.0 g Zn/kg seed for optim um<br />
performance (Slaton et al., 2001b). The higher rate should be used when severe Zn<br />
deficiency is expected. Compared to other fertilization methods, Zn seed treatm ent is<br />
convenient for the grower <strong>and</strong> is a low-cost, low-use rate method o f Zn fertilization<br />
that has proved to be the equal o f soil <strong>and</strong> foliar Zn application.<br />
The availability o f soil <strong>and</strong> fertilizer Zn, <strong>and</strong> subsequent uptake by rice, are influenced<br />
by many factors, but only small quantities o f Zn are required for norm al<br />
plant growth <strong>and</strong> development. W hole-plant tissue Zn concentrations o f nutritionally<br />
healthy rice may range from 10 to 35 mg Zn/kg during the season (Wells, 1980),<br />
but whole-plant tissue Zn concentrations higher than 35 m g Zn/kg are com monly<br />
reported in the literature (M ikkelsen <strong>and</strong> Br<strong>and</strong>on, 1975; Yoon et al., 1975; Gilmour,<br />
1977a), Wells (1980) found that rice tissue Zn concentrations were greatest during<br />
seedling rice growth before flooding <strong>and</strong> declined rapidly after N fertilization <strong>and</strong><br />
flooding when rapid dry-matter <strong>production</strong> began at the onset o f tiUering. Tissue Zn<br />
concentration was lowest around the vegetative lag phase (or beginning o f reproductive<br />
plant growth— ^panicle initiation). During reproductive growth, Zn tissue concentrations<br />
increased gradually until heading <strong>and</strong> then reached a plateau or declined<br />
slightly until physiological m aturity was reached.<br />
Gilmour (1977b) found that the Zn uptake rate tended to increase between flooding<br />
(five-leaf stage) <strong>and</strong> midseason. The highest rate o f Zn uptake occurred around<br />
panicle initiation. This helps confirm Wells’s (1980) observation that tissue Zn concentration<br />
started to increase at the onset of reproductive growth. The gradual in <br />
crease in the rate o f Zn uptake by rice is probably due to the development o f the nodal<br />
root system after flooding.<br />
The Zn concentration in rough rice seed typically ranges from 20 to 35 mg Zn/kg<br />
seed (Rashid <strong>and</strong> Fox, 1992). Thus a rice crop with a rough rice yield o f 9000 kg/ha <strong>and</strong><br />
an average Zn concentration o f 27 g o f Zn per 1000 kg rough rice would remove 243 g
382 Production<br />
Zn/ha. <strong>Rice</strong> straw at m aturity com monly has a Zn concentration ranging from 20 to<br />
30 mgZn/kg (Giordano <strong>and</strong> Mortvedt, 1974; Wells, 1980). Consequently, 275 g Zn/ha<br />
would he contained in the rice straw based on a rice crop with a total aboveground<br />
biomass (grain <strong>and</strong> straw) o f 20 000 kg/ha, o f which 11000 kg/ha is rice straw with<br />
an average Zn concentration o f 25 mg Zn/kg straw. Therefore, the total aboveground<br />
rice uptake o f Zn typically ranges from 400 to 600 g Zn/ha. Zinc fertilizer recom m endations<br />
for preplant broadcast application o f granular Zn fertilizers normally suggest<br />
the use o f 11 kg Zn/ha, which is about 20 times the am ount o f total crop uptake <strong>and</strong> 40<br />
times crop removal. Application o f rates in excess o f crop use are required for adequate<br />
distribution o f Zn fertilizer granules <strong>and</strong> because Zn is immobile in the soil. Research<br />
using ^^Zn-labeled broadcast-applied Zn fertilizers has shown that flood-irrigated rice<br />
uptake o f fertilizer Zn is generally less than 5% (Giordano <strong>and</strong> Mortvedt, 1972; Bashir,<br />
1999). The plant uptake efficiency o f fertilizer Zn applied to rice seed or foliage is<br />
not known.<br />
Iron <strong>and</strong> Manganese Forms <strong>and</strong> Behavior in Flooded <strong>Rice</strong> Soils<br />
ii.:<br />
Iron <strong>and</strong> M n in the soil conceptually exist in four basic forms: solution Fe <strong>and</strong> Mn,<br />
adsorbed Fe <strong>and</strong> exchangeable M n, organic complexed Fe <strong>and</strong> M n, <strong>and</strong> Fe <strong>and</strong> M n in<br />
primary <strong>and</strong> secondary minerals. All o f these forms o f Fe <strong>and</strong> M n are in equilibrium<br />
with solution Fe <strong>and</strong> M n, <strong>and</strong> the organic complexed form s facilitate their transport<br />
in the soil solution <strong>and</strong> uptake by rice. Unlike Zn, these two metal micronutrients<br />
can be reduced in flooded soil <strong>and</strong> become m uch more soluble <strong>and</strong> plant available.<br />
The reduced form s o f these micronutrierits, ferrous iron (Fe^+) <strong>and</strong> manganous m anganese<br />
(Mn^ ' ), are much more soluble then their oxidized form s, ferric (Fe^'^) <strong>and</strong><br />
manganic (Mn^ ' ). The reduced species o f Fe <strong>and</strong> M n are the preferred form s taken<br />
up by plants (Moore, 1972). Consequently, the reducing conditions associated with<br />
flooding greatly facilitates the availability o f these two micronutrients to rice. The<br />
reduction of insoluble Fe <strong>and</strong> Mn compounds can solubilize appreciable quantities of<br />
solution Fe^'' <strong>and</strong> Mn^ '' (Patrick et al., 1985). Similar to Zn, however, solution Fe <strong>and</strong><br />
M n concentrations decrease appreciably as pH increases. Most deficiencies o f Fe <strong>and</strong><br />
M n in rice occur in the Florida Everglades agricultural area, where rice is grown on<br />
organic soils (i.e., Histosols; Snyder <strong>and</strong> Jones, 1988), or occasionally in other states on<br />
mineral soils that are alkaline <strong>and</strong>/or have been precision leveled. Deficiencies occur<br />
on organic soils due to minimal amounts of Fe <strong>and</strong> M n minerals, on precision-graded<br />
soils probably because o f low amounts o f organic complexing. compounds, <strong>and</strong> on<br />
high-pH soils due to form ation o f insoluble Fe <strong>and</strong> M n compounds.<br />
Iron <strong>and</strong> Manganese Nutrition, Fertilization Practices, <strong>and</strong> Diagnosis<br />
of Deficiency<br />
Both Fe <strong>and</strong> Mn deficiency symptoms in dry-seeded, delayed-flood rice tend to occur<br />
after seeding but before flooding. Iron-deficiency symptoms o f rice typically occur<br />
before flooding as a chlorosis o f the youngest leaf o f seedling rice since Fe is immobile<br />
in the plant (Wells et al., 1993). Iron deficiency left uncorrected can cause the entire<br />
leaf to turn white. Seedling chlorosis may disappear after flooding as Fe*+ is reduced
Soil Fertilization <strong>and</strong> Mineral Nutrition in U.S. Mechanized <strong>Rice</strong> Culture 383<br />
to more soluble Fe^+. However, soils can take days or even weeks to become reduced<br />
enough to transform Fe^+ to m ore soluble Fe^+ following flooding. Significant st<strong>and</strong><br />
loss can occur after flooding, especially in deep water, if the Fe deficiency in the young<br />
rice plants is not corrected before flooding. Tissue analysis for Fe deficiency has proved<br />
to be o f little value, because chlorotic Fe-deficient plants often have equal or higher<br />
tissue Fe concentrations tlian those of normal, healthy seedlings (Snyder <strong>and</strong> Jones,<br />
1988). The location of the Fe in the plant appears to be o f m ore importance than the<br />
concentration.<br />
• Manganese deficiency also occurs before flooding but appears as an interveinal<br />
chlorosis o f seedling leaves (Snyder, 1993). Manganese deficiency also reduces seedling<br />
height, weight, number o f leaves, <strong>and</strong> root length <strong>and</strong> weight. Seedling (whole-plant)<br />
tissue concentrations below 20 mg Mn/kg are considered deficient for rice in Florida.<br />
A critical value o f 40 mg Mn/kg for the rice Y-leaf is suggested during both the tillering<br />
<strong>and</strong> panicle differentiation growth stages by Bell <strong>and</strong> Kovar (2000). Similar to Fe, M n<br />
deficiency in seedling rice may disappear after flooding because o f tlie reduction of<br />
insoluble M n compounds to more soluble, plant-available Mn^ ' form.<br />
Snyder et al. (1990) concluded that M n deficiency typically occurs on organic<br />
soils with soil pH > 7.0. Fields that show Mn deficiency generally have limestone<br />
underlying tire organic topsoil or have had limestone deposited from dust by adjacent<br />
gravel roads. In contrast, Fe deficiency on organic soils has not been associated<br />
with soil pH but with low soil Fe content or Fe minerals. Iron-deficient soils can<br />
be identified either by examining the color o f the ash following ignition of the soil<br />
organic matter or by a chemical soil test metliod (Snyder <strong>and</strong> Jones, 1988; Snyder <strong>and</strong><br />
Elliott, 1994).<br />
Broadcast applications o f Fe or M n fertilizers are generally not recommended, because<br />
they require very high rates o f application to prevent deficiency symptoms. Iron<br />
<strong>and</strong> M n fertilizers are com m only applied directly under the seed by use o f fertilizer<br />
boxes on grain drills. Application o f 15 kg Mn/ha as manganese sulfate (i.e., MnSO^i;<br />
26 to 28% M n) at the tim e o f seeding is recommended for prevention o f M n deficiency<br />
(Snyder et al., 1990). Although flooding the soil generally alleviates interveinal<br />
chlorosis, grain yield reductions may occur in the absence o f proper fertilization.<br />
For the prevention o f Fe deficiency, application o f water-soluble Fe fertilizer<br />
granules or a liquid Fe solution are recommended at seeding. Depending on the<br />
degree o f Fe deficiency, fertilizer application rates range from 11 to 33 kg Fe/ha.<br />
The two m ost com m on sources o f Fe sulfate used are the monohydrate (FeS0 4 -H2 0 ,<br />
30% Fe) <strong>and</strong> heptahydrate (FeS0 4 *7 H 2 0 , 20% Fe) sources. Use o f less water soluble<br />
Fe sources require m uch higher application rates (Snyder <strong>and</strong> Jones, 1988). Foliar<br />
application o f Fe solutions applied shortly after rice emergence improves rice growdi<br />
<strong>and</strong> yield but are not as effective as Fe applied at seeding (Snyder <strong>and</strong> Jones, 1991).<br />
<strong>Rice</strong> cultivars may differ in response to Fe deficiency (Snyder <strong>and</strong> Jones, 1988). Iron<br />
<strong>and</strong> M n deficiency can also be prevented by flooding the soil several days before water<br />
seeding to allow for reduction o f these elements to occur.<br />
! f<br />
i:'i<br />
!<br />
Silicon Nutrition <strong>and</strong> Fertilization<br />
Silicon is the second m ost abundant mineral in the earth’s crust but is not considered<br />
an essential element for many plant species. Silica is considered a “beneficial” element
384 Production<br />
Hi-::<br />
i<br />
ífe:<br />
ip:’<br />
¡ p<br />
í i -<br />
I#-:-<br />
for rice growth, because it has not been shown that rice fails to complete its life cycle in<br />
the absence o f Si. Plant species are categorized as either Si accumulators or nonaccumulators<br />
(Marschner, 1995). <strong>Rice</strong> is considered a Si accumulator species. Application<br />
o f Si amendments have been shown to be beneficial to rice growth, yield, <strong>and</strong> pest<br />
reaction in some areas o f the United States. Research in Florida has demonstrated that<br />
Si-containing soil amendments have produced significant yield increases on organic<br />
soils (Snyder et a l, 1986). Limited efforts on mineral silt loam soils have demonstrated<br />
that supplemental Si amendments do not consistently increase rice grain yields, disease<br />
resistance, or insect resistance (Bollich et al., 1997; Lee et al., 2000). The following<br />
discussion concerning the role o f Si in rice nutrition <strong>and</strong> growth addresses research<br />
showing the benefits of this nutrient on rice growth <strong>and</strong> yield in the United States.<br />
Savant et al. (1997) provide a worldwide review o f silica nutrition o f rice.<br />
In the United States, application of Si-containing amendments has shown prom <br />
ise for increasing rice grain yields only for Histosols in the Florida Everglades agricultural<br />
area. Sugarcane {Saccharum spp.) is grown in rotation with rice in the Everglades<br />
agricultural area (EAÁ) <strong>and</strong> also responds favorably to Si fertilization (Anderson et al,<br />
1987). <strong>Rice</strong> grown in the EAA frequently suffered from low yields, high levels o f floret<br />
sterility, lodging, floret discoloration, <strong>and</strong> a high incidence o f fohar diseases such as<br />
brown spot {Bipolaris oryzae‘, Snyder et al., 1986), which are potential symptoms of<br />
Si deficiency in rice (Wells et a l, 1993). Plant height, panicles/m^, number o f grains<br />
per panicle, <strong>and</strong> grain weight have all been positively affected by Si application to<br />
organic soils in Florida (Deren et a l, 1994; Snyder et al., 1986). Grain yields have<br />
been increased by as much as 60% , above an untreated control, from Si application.<br />
Application o f Si amendments has reduced the incidence <strong>and</strong> severity o f several diseases,<br />
including brown spot (Deren et a l, 1994) <strong>and</strong> blast (Pyricularia grísea; D atnoff<br />
et a l, 1991)].<br />
Calcium silicate slag (Ca^^SiOs; '^20% Si) is the m ost com monly used Si source<br />
(Snyder, 1993). <strong>Rice</strong> yield response <strong>and</strong> disease reaction is affected significantly by<br />
the grade or particle size of Ca,¡Si0 3 amendments (D atnoff et a l, 1992). Smaller<br />
CaxSiOs particles produced higher yields <strong>and</strong> reduced disease severity to a greater<br />
extent then did larger particles, In Florida, Ca^SiO^ is typically applied at rates of<br />
4480 kg/ha (Snyder, 1993). Additional yield increases have been observed at higher<br />
rates o f application but are probably not econom ical Calcium silicate slag contains<br />
substantial amounts of other beneficial nutrients [i.e., Ca (^ 21 to 33.0% ), P (~ 0 .5 % ),<br />
Fe (^ 0 .5 to 1.0% ), Mg (0.3% ), <strong>and</strong> K (~ 0.1 to 0,40% )], <strong>and</strong> significant amounts of<br />
these nutrients are applied when the suggested rate o f 4480 kg CaxSi0 4 /ha is used<br />
(Snyder et al., 1986; Anderson et al., 1987). <strong>Rice</strong> hull ash (~ 6 1 to 93% amorphous<br />
Si), produced by burning rice hulls to generate power, is a potential Si source for<br />
rice (Sistani et a l, 1997; Lee et a l, 2000). The critical concentration o f acetic acid<br />
extractable (0.5 M ) Si in Florida soils is 19 mg Si/mL soil (Korndorffer et a l, 2001).<br />
Silica is absorbed b y rice roots from the soil solution as orthosilicic acid ( H 4 S Í O 4 ).<br />
Uptake o f Si by rice is considered active because a distinct transport mechanism,<br />
largely unaffected by transpiration rate, appears to function in uptake (Marschner,<br />
1995). The literature suggests that active Si uptake begins during the tillering phase,<br />
<strong>and</strong> most of the Si is absorbed during reproductive growth. Application of Si also<br />
increases the Si concentration o f rice seedlings (Sistani et a l, 1997). At maturity, rice<br />
straw contains between 2.0 <strong>and</strong> 6.0% Si (Deren et a l, 1994; Bollich et al., 1997). Thus<br />
the total seasonal uptake of Si exceeds that o f both K <strong>and</strong> N. Snyder et al. (1986)
Soil Fertilization <strong>and</strong> Mineral Nutrition in U.S. Mechanized <strong>Rice</strong> Culture 385<br />
proposed a critical straw Si concentration o f 3.0% at m atitrity for rice grown on<br />
Histosols. Wells et al. (1993) cited a critical straw Si concentration o f 5.0% for rice<br />
grown on mineral soils. Little inform ation is available concerning critical tissue Si<br />
concentrations for rice growth stages or seasonal uptake. <strong>Rice</strong> cultivars also differ in<br />
their ability to accumulate Si, especially when plant available Si is lim iting (Deren<br />
et al., 1992).<br />
Other Aflkronutrienf <strong>and</strong> Essential Element Requirements<br />
The rice plant requires m icronutrients <strong>and</strong> other essential elements besides Fe, M n,<br />
Zn, <strong>and</strong> Si. However, there has been no conclusive evidence that any other nutrients<br />
are in limited supply in soils where rice is grown in the United States. Boron (B ) fertilization<br />
o f rice has recently been evaluated by researchers in Louisiana <strong>and</strong> Missouri.<br />
Generally, little or no rice yield response to B has been measured. Inform ation on<br />
critical tissue nutrient ranges for rice or extractable soil levels o f other essential nutrients<br />
are lacking. This can be partially attributed to the following reasons: (1) other<br />
micronutrients, such as copper, molybdenum, <strong>and</strong> selenium, are required in very<br />
small quantities for optim um rice growth <strong>and</strong> must be in adequate supplies in our<br />
rice soils; (2) elements such as sodium <strong>and</strong> chloride are abundant in our sods, to the<br />
point o f being at toxic concentrations in some soils; (3) deficiencies occur very rarely;<br />
<strong>and</strong>/or (4) we have not yet identified the symptoms or the fields where these other<br />
nutrient deficiencies exist. Sufficiency ranges o f other essential plant nutrients can be<br />
found in Sedberry et al., (1987), Bell <strong>and</strong> Kovar (2000), <strong>and</strong> W ilson et al. (2001b).<br />
:i<br />
RICE MANAGEMENT ON SALINE AND ALKALINE SOILS<br />
Irrigation is vital for continued profitability o f rice <strong>production</strong> in the United States.<br />
However, throughout <strong>history</strong>, intensive irrigation has ultimately resulted in the development<br />
o f saline soils. Recent worldwide estimates suggest that nearly one-half o f<br />
all irrigated soils are affected by salinity or alkalinity, which amounts to 250 million<br />
hectares, <strong>and</strong> nearly 10 million hectares are ab<strong>and</strong>oned annually due to the low productivity<br />
associated with these soils (Szabolcs, 1985). Soil science as a discipline has<br />
evolved from the pursuit o f underst<strong>and</strong>ing soil problems directly or indirectly related<br />
to salinity, <strong>and</strong> this effort has resulted in many o f the advances made in this discipline<br />
(Letey, 1984). Although irrigation is necessary in the United States for profitable rice<br />
<strong>production</strong>, the effects o f salinity induced by irrigation water on soil sustainability<br />
make this as a significant problem.<br />
There is a perception that conflicts exist in term inology related to salt-affected<br />
soils. To prevent confusion here, definitions <strong>and</strong> characterizations o f soil conditions<br />
related to salt-affected soils are presented. Salinity is described as tliat condition related<br />
to the presence o f soluble salts in amounts sufficient to impair the productivity o f<br />
the soil. The salts m ost com m only encountered include those with cations, such as calcium<br />
(Ca^+), magnesium (Mg^+), sodium (Na+), <strong>and</strong> IC, <strong>and</strong> anions, such as bicarbonate<br />
(H CO^), chloride (C U ), NO7 , SO^” , <strong>and</strong> borate (BO^” ), although others m aybe<br />
present in some areas. Soils are classified as saline when the electrical conductivity o f<br />
a saturated paste extract (ECe) exceeds 4 dS/m (Table 3.4.11). Allcaline soils are those
386 Production<br />
TABLE 3.4.11.<br />
Classification of Salt-Affocted Soils<br />
Electrical C onductivity<br />
Soil Condition<br />
Soil pH<br />
EC.<br />
Sodiiim Characterization^<br />
dS/m S/cm mS/cm juS/cm<br />
EC„2<br />
(dS/m) ESP SAR<br />
Normal 4000 >0.9 >15 > 13<br />
Sodic >8.5
Soil Fertilization <strong>and</strong> Mineral Nutrition in U.S. Mechanized <strong>Rice</strong> Culture 387<br />
extract (Rhoades, 1996). Other extraction techniques have been utilized for rapid<br />
determinations, such as 1:1, 1:2, <strong>and</strong> 1:5 soil/water extracts. Although m ore water<br />
usually results in easier determinations, the data becom e less representative o f the soil<br />
solution to which the plant roots are exposed. The m ore dilute extracts are, however,<br />
useful for relative comparisons.<br />
The salt content o f the extract is usually performed by measuring the electrical<br />
conductance. The st<strong>and</strong>ard (SI) units for electrical conductivity measurements are<br />
decisiemens per meter (dS/m). However, other units are often encountered in older<br />
literature. These include m ho per centimeter (mho/cm), mdlimho per centimeter<br />
(mmho/cm), m icrom ho per centimeter (/imho/cm), <strong>and</strong> parts per million (ppm ).<br />
The relationships among these units are summarized in Table 3.4.1 1.<br />
Sources of Soluble Salts. The primary sources o f soluble salts in agricultural soils<br />
are from weathering o f primary minerals, seawater, m arine parent material deposits,<br />
atmospheric inputs, salt seeps, irrigation water, or excessive fertilizer applications. The<br />
m ost im portant source o f soluble salts is weathering o f primary minerals, because this<br />
process is responsible either directly or indirectly for nearly all the soluble salts found<br />
in soils. Although there are some regions where saline sods develop directly from<br />
weathering o f primary minerals, this is probably the least direct source o f soluble salts<br />
found in m ost regions o f the world (U.S. Salinity Laboratory Staff, 1954). The m ost<br />
com m on direct source o f salts results from irrigation water, from either groundwater<br />
or surface water (e.g., rivers, streams, reservoirs).<br />
All surface <strong>and</strong> groundwaters contain a certain am ount o f soluble salts, the degree<br />
depending on the soils <strong>and</strong> minerals with which the water has been in contact. W hen<br />
the salts added via irrigation water exceed the rate o f removal from the soil, salinity<br />
will develop. The m ajority o f saline soils found in the world are located in arid <strong>and</strong><br />
semiarid climates, due to insufficient rainfall to leach the salts deep into the soil<br />
profile. However, saline soil conditions do exist in certain regions with humid climates<br />
because the soil properties inhibit the leaching o f salts deep into the soil profile <strong>and</strong><br />
below the root zone.<br />
Characterization of Irrigation Water Quality. To characterize irrigation water quality,<br />
four criteria must be evaluated: ( 1) the total concentration o f soluble salts, (2) the<br />
relative proportion o f Na to other cations, (3) the concentration o f H CO 3 as related<br />
to Ca <strong>and</strong> Mg, <strong>and</strong> (4) in some cases, the concentration o f B or other elements<br />
that may be toxic. Total salt concentration is ordinarily determined using electrical<br />
conductivity (ECw). W hile the st<strong>and</strong>ard units are dS/m, as is the case for soil salinity,<br />
concentration o f total cations is sometimes reported in mEq/L or cmoles/L. The<br />
relationship between the two units is approximately given by<br />
C = lO E C (1)<br />
where C is the concentration expressed in mEq/L <strong>and</strong> EC« is the electrical conductivity<br />
expressed in dS/m. Similarly, salinity is often estimated by measuring the total<br />
dissolved solids (TD S) reported in parts per million (ppm ). The relationship between<br />
total dissolved solids <strong>and</strong> ECy, is approximately<br />
TDS = 640EC« (2)
388 Production<br />
The potential for developing sodic soils resulting from irrigation water is determined<br />
m ost commonly by measuring the sodium adsorption ratio (SAR), defined as<br />
SAR =<br />
Na-'<br />
y(Ca2-" + Ut^)H<br />
(3 )<br />
where Na+, Ca^"^, <strong>and</strong> Mg^ '' are concentrations in mm oh L.<br />
To describe the salinity <strong>and</strong> Na hazards of irrigation water, a characterization<br />
diagram has been developed by the U.S. Salinity Laboratory Staff (1954) (Figure<br />
3,4.10). The diagram outlines four classification ranges each for salinity <strong>and</strong> Na, based<br />
on ECw <strong>and</strong> the SAR o f the irrigation water. The salinity hazard is classed as low (EC^<br />
< 0,25 dS/m), medium (0,25 dS/m < ECw < 0.75 dS/m)> high (0,75 dS/m < EC„<br />
< 2.25 dS/m), <strong>and</strong> very high (ECw > 2.25 dS/m). Similarly, the Na hazard is classified<br />
as low, medium, high, or very high. However, note that the slopes o f the critical<br />
thresholds for SAR are negative with respect to increasing ECw (Figure 3.4.10). This<br />
illustrates that soil physical properties may be impaired at lower SAR levels as salt<br />
content increases.<br />
Behavior of Solubie Salts in <strong>Rice</strong> Soils<br />
Although irrigation water is the m ajor source o f soluble salts contributing to salinity<br />
problems in U.S, rice <strong>production</strong>, the phenom ena that occur vary somewhat due to<br />
f<br />
i<br />
Figure 3.4.10, Characterization of saline <strong>and</strong> sodic irrigation water.<br />
C, conductivity; S, sodium adsorption ratio; 1, low hazard; M, medium hazard; H, high<br />
hazard; VH, very high hazard, [Adapted from U.S, Saiinity Laboratory Staff, 1954,)
Soil Fertilization <strong>and</strong> Mineral Nutrition in U.S. Mechanized <strong>Rice</strong> Culture 389<br />
different cultural practices, soils, <strong>and</strong> locations. The salinity problems observed in<br />
California rice fields result, partially if not entirely, due to regulation o f tailwater<br />
release (Scardaci et al., 1999.). Tailwater release is restricted in this region during<br />
the rice growtli stages m ost sensitive to salinity. The m ost severe salinity is usually<br />
observed in the paddies farthest from the water inlet source. Water near the drainage<br />
outlet becomes increasingly saline due to evaporation <strong>and</strong> the inability to release the<br />
fioodwater. The extent is such that the soil <strong>and</strong> floodwater salinity can at times greatly<br />
exceed the thresholds for successful rice <strong>production</strong> (> 2 dS/m). More irrigation<br />
water is used in California rice <strong>production</strong> because (1) rice is water-seeded, (2) rains<br />
are infrequent, <strong>and</strong> (3) irrigation water is added continually during the season to<br />
compensate for évapotranspiration losses.<br />
In contrast to the problems associated with regulated water drainage in California,<br />
the salinity problems found in the southern United States are primarily a result<br />
o f either extremely saline irrigation water or inherent soil properties found in the<br />
region that enhance salt accumulation in these soils. In southern Louisiana, drought<br />
conditions during 1999 to 2000 brought about by La Nino led to the development o f<br />
saline irrigation water due to intrusion o f seawater from tlie G ulf o f Mexico. Although<br />
the region has generally had little <strong>history</strong> o f salinity problems, a significant amount<br />
o f rice hectarage in 2000 was affected by saline irrigation water.<br />
Salt intrusion into the aquifers typically utilized for irrigation in the southern<br />
United States has led to significant salinity problems in this region. One scenario tliat<br />
occurs is the use o f irrigation water that is inherently high in soluble salts. The ECw<br />
o f the irrigation water in some locations exceeds 3 dS/m (M oore et al., 1993; Wilson<br />
et a l, 2000b). The salt concentration o f this water is sufficient to cause injury to rice<br />
if used for irrigating seedling rice. Productivity has been negatively affected to such<br />
an extent that the water sources have been capped. Although this is the m ost direct<br />
effect o f irrigation water on development o f saline soils, other phenomena occur that<br />
contribute to the m ajority o f the salinity problems in the southern United States. The<br />
more com m only observed situations are mild-to-m oderate salinity injury to rice from<br />
the use o f irrigation water that is marginally saline (EC« < 1 .2 dS/m), coupled with<br />
inherent soil properties which contribute to saline conditions during sensitive growth<br />
stages o f the rice plant (W ilson et al., 2000a).<br />
The dry-seeded, delayed-flood system used in the southern U.S. rice belt results<br />
in a 4- to 6-week period after seeding during which the rice is grown in an upl<strong>and</strong><br />
environment before die permanent flood is established. Many o f the soils used for rice<br />
<strong>production</strong> in this region are underlain at some depth, usually less than 120 cm, with<br />
an essentially impermeable layer typically characterized as a fi:agipan, argillic horizon,<br />
or abrupt textural change. Additionally, a very dense plow pan is often present<br />
beginning at a depth o f 7 to 10 cm <strong>and</strong> extending downward to a depth o f 15 to 20 cm.<br />
Although this pan restricts downward water flow to a certain degree, which improves<br />
flood efficiency, it also restricts the movement o f salts out o f the rice root zone. The<br />
plow pan diat develops tends to be dense, but also contains holes such as root channels<br />
<strong>and</strong> zones o f weakness that have very high hydraulic conductivity at water contents<br />
close to saturation compared to the surrounding pan m atrix. W hen soluble salts are<br />
present at the soil surface, downward leaching through the plow pan via these zones<br />
o f weakness is possible (Figure 3.4.11 A). However, the underlying impermeable layer<br />
inhibits soluble salts from being leached completely from the soil profile at the same<br />
; j I<br />
■;i !<br />
if i<br />
. I<br />
i
Soil Fertilization <strong>and</strong> Mineral Nutrition in U.S. Mechanized <strong>Rice</strong> Culture 391<br />
rate. Subsequently, it is likely that salt will be added to these soils at rates that exceed<br />
rates o f removal.<br />
At the beginning o f infiltration into the layered soil (Ap, 0 to 7 cm ; plow pan<br />
7 to 20 cm; impermeable layer, > 20 cm ), the soluble salt moves near the wetted<br />
front (Figure 3.4. l l h ) . W hen the wetted front reaches the plow pan, water moves<br />
slowly into the plow pan. If the surface infiltration rate is less than or equal to the<br />
rate o f movement into the plow pan, the water <strong>and</strong> solutes pass through the plow pan<br />
simultaneously, the salts move in a manner similar to piston displacement, <strong>and</strong> the<br />
pealc soluble salt concentration is usually found deep in the soil profile (Wagenet,<br />
1984). However, if the surface infiltration rate exceeds the transmission o f water<br />
through the plow pan, the water content behind the front increases, preferential flow<br />
o f salt <strong>and</strong> water occurs, <strong>and</strong> the soluble salts are distributed exponentially with depth.<br />
The distribution with depth is established quite rapidly <strong>and</strong> may remain stable for a<br />
relatively long time (Figure 3.4.11C ) (Wagenet, 1984).<br />
W hen a surface infiltration <strong>and</strong> redistribution event such as that described above<br />
ceases, evaporation o f soil water occurs at the soil surface. Nonpreferential flow o f salt<br />
<strong>and</strong> water upward results in movement o f soluble salt from the entire depth toward<br />
the soil surface (Figure 3.4,IID ). W hen the water evaporates at the soil surface, the<br />
soluble salts are deposited near the soil surface (Figure 3.4.12). W hen these surface<br />
infiltration events are coupled with preferential downward flow followed by nonpreferential<br />
upward flow, the exponential salt distribution with depth is self-perpetuating<br />
(Wagenet, 1984). The result is tire accumulation o f salt in the rice root zone. If this<br />
sequence o f events occurs prior to flooding in dry-seeded, delayed-flood rice during<br />
Figure 3.4.12. Soluble salt distribution in soil profile prior to (May 29, 1998) <strong>and</strong> aftor (June 6, 1998) o drying<br />
event. Roinfall [2,5 cm) occurred or May 28,1998. (From Wilson et ol., 2000.)
392 Production<br />
the seedling growth stage, injury is likely to occur due to the excessive soluble salt<br />
in the root zone. Consequently, more severe salinity injury to seedling rice is often<br />
observed following periods of dry, windy weather in dry-seeded, delayed-flood rice.<br />
In a humid climate with an excess of 100 cm o f annual rainfall, the conditions<br />
necessary for soluble salts to be a problem include a source o f soluble salts, such as<br />
irrigation water, <strong>and</strong> a soil layer tliat is essentially impervious to downward leaching. If<br />
the salt causes injury primarily as a result of osm otic potential, there is usually a m echanism<br />
o f soluble salt concentration. This concentration mechanism has been thought<br />
o f only in terms of evaporation. However, in humid regions, other soil physical properties<br />
are apparently involved in salt accumulation near the soil surface in addition<br />
to evaporation, that is, the preferential flow that takes place during water infiltration.<br />
Under some conditions a coupling between infiltration <strong>and</strong> evaporation, responding<br />
similar to a salt pump, causes salt to concentrate near the soil surface. The result is a<br />
soil that maybe conducive to salt accumulations at injurious levels despite having relatively<br />
low concentrations of soluble salts throughout the entire soil profile. Because<br />
o f the dominance o f this mechanism in the southern United States, the salt concentration<br />
o f soil,/samples collected 1 to 6 m onths prior to seeding is often o f little value.<br />
Effects of Soluble Salts on <strong>Rice</strong> Plant Growth<br />
■!<br />
Stage of Growth. Much o f the early literature suggested that rice was relatively salt<br />
tolerant (U.S. Salinity Laboratory Staff, 1954). However, rice is highly sensitive at the<br />
seedling growth stage (Figure 3.4.13). Although rice is considered to be moderately<br />
susceptible to salinity, variations between cultivars <strong>and</strong> growth stages have been reported<br />
(Yoshida, 1981). Overall rice productivity is usually not significantly reduced<br />
until the EC^ exceeds 4 dS/m <strong>and</strong> may not reach 50% reduction in productivity until<br />
the ECe exceeds 6 dS/m (Figure 3.4.13). However, lower levels o f salinity (EC« < 2<br />
dS/m; E C ,;2 - 0.4 to 0.5 dS/m) can be detrimental to rice if it is exposed during the<br />
ii/ !<br />
Figure 3.4.13.<br />
etal,, 1982.)<br />
Relative tolerance of rice to salinity. (Adapted from Bresler
1<br />
Soil Fertilization ond Mineral Nutrition in U.S. Mechanized <strong>Rice</strong> Culture 393<br />
seedling growth stage (Baser <strong>and</strong> Gilmour, 1982; W ilson et al.> 2000a). <strong>Rice</strong> germination<br />
is usually unaffected by saline conditions when the EC is as high as 20 dS/m, but<br />
rapidly becomes sensitive as the seedling attempts to emerge from tlie soil. Seedling<br />
rice may be injured when the E C i;2 is as little as 0.5 dS/m. But, tolerance tends to<br />
increase after rice begins tillering. Rhoades <strong>and</strong> Loveday (1990) report a critical ECe<br />
o f 3dS/m for paddy rice, although some researchers have reported higher tolerance<br />
(ECe = 6 dS/m) during reproductive growth stages.<br />
Osmotic Effects. The effects o f salinity on rice growth as described above can be attributed<br />
primarily to osm otic pressure changes in the root zone (W ilson et ah, 2000a).<br />
The increased osm otic pressure o f the soil solution resulting from increased salt content<br />
impairs a plant’s ability to absorb water. Many o f the physiological responses if a<br />
plant increase the energy requirement for water intake <strong>and</strong> consume energy needed<br />
for other m etabolic functions. Because o f the effects o f osmotic pressure on water<br />
uptake, relationships have been developed between EC« <strong>and</strong> the osm otic pressure o f<br />
the soil solution. Reeve <strong>and</strong> Fireman (1.967) described this relationship as<br />
t r:<br />
OP -0.36EC, (4 )<br />
where O P is the osm otic pressure of the soil solution <strong>and</strong> ECe is the electrical conductivity<br />
o f the saturation extract expressed in dS/m.<br />
Specific Ion Effects. Salinity injury to rice as a result o f the specific types o f cations<br />
<strong>and</strong> anions present has also been reported. The presence o f specific anions is more<br />
im portant to salinity injury than the specific cations. The sensitivity o f seedling rice<br />
to anions generally decreases in the order Cl“ > N O j > SO 4“ (Baser <strong>and</strong> Gilmour,<br />
1982). Although tiller <strong>production</strong>, total dry matter <strong>production</strong>, <strong>and</strong> grain yield decrease<br />
with increasing salinity, the effect is not specific to the type o f cation used to<br />
induce salinity (Figure 3.4.14), Although overall salinity injury does not appear to be<br />
affected by the particular cation, nutrient uptake is significantly affected. Excessive<br />
Na applied as NaCl has been shown to depress uptake by rice much more severely<br />
Figure 3.4,14. Influence of four cation salts on total dry motter (4), ponicle-bearing tillers (81 <strong>and</strong> grain yield (f). (From<br />
unpublished data of C E. Wilson, Jr., <strong>and</strong> P. A. Moore, Jr.)
394 Production<br />
l i -<br />
m<br />
than CaCh (W ilson et al., 1995b), Accumulation o f anions, particularly Cl% appears to<br />
account for the m ajor damage to rice seedlings due to salinity, but nutrient imbalances<br />
may result, depending on the predominant cation.<br />
Salinity injury occurs to rice mainly during the seedling stage <strong>and</strong> to larger rice<br />
located on levees both prior to <strong>and</strong> after flooding. Injury results when soluble Cl“<br />
or N O J salts become concentrated within the root zone of the seedling rice plant<br />
This accumulation is often the result o f irrigation water containing moderately high<br />
quantities o f soluble salts. In addition, problems witli salinity are com monly associated<br />
with poor soil drainage, <strong>and</strong> some soils <strong>and</strong> subsoils have naturally high levels<br />
o f soluble salts. The poor drainage characteristics that are beneficial for flood maintenance<br />
in rice are the same characteristics that increase the likelihood o f salinity.<br />
Salinity injury occasionally occurs when a field is flush irrigated with groundwater<br />
containing extremely high levels o f salt. W hen this is the case, surface water sources<br />
should be utilized where possible.<br />
Plant symptoms o f salinity injury include leaf tip dieback, leaf rolling, stunting<br />
<strong>and</strong> rapid death, increased sensitivity to herbicides, <strong>and</strong> reduced st<strong>and</strong> densities.<br />
Plants are usually at the two- to five-leaf stage. <strong>Rice</strong> is tolerant to salinity during<br />
germination^ however, it becomes quite sensitive to damage during early seedling<br />
development. Plant analysis often indicates an excessive level o f Cl“ <strong>and</strong>/or NO3 in<br />
the tissue.<br />
Management of Saline Soils<br />
Literature detailing reclamation procedures are limited. M ost o f the efforts to reclaim<br />
saline soils have focused on leaching'the salts from the profile (Rhoades <strong>and</strong> Loveday,<br />
1990). The leaching requirement (LR) is calculated based on tolerable levels o f salinity<br />
for the crop to be produced. However, little success has been obtained with leaching<br />
as a means o f reclamation, per se, on the rice soils o f the southern United States. The<br />
low permeability o f many o f these soils, which makes them very suitable for effective<br />
paddy rice <strong>production</strong>, limits the effectiveness o f leaching as a means o f salt removal.<br />
Leaching Requirements. Removal o f excess salts from soils requires access to ample<br />
supplies o f good-quality irrigation water <strong>and</strong> good internal drainage in the soils. To<br />
determine the amount o f water required to leach the salts from the profile, the leaching<br />
requirement (LR) is determined. This is approximated by the ratios o f the salinity of<br />
the irrigation water (EC^) to the maximum permissible salinity o f the soil solution<br />
for the crop to be grown (ECdw)» which is measured as the EC o f the drainage water.<br />
i i :<br />
I<br />
EC ,<br />
LR<br />
(5)<br />
ECfi,<br />
This ratio is then multiplied by the am ount o f water needed to saturate the soil<br />
completely to determine the minim um amount o f water that must be leached through<br />
a water-saturated soil to m aintain a proper salt balance. Limitations on the use of<br />
the leaching fraction is that the limits (i.e., thresholds) are not easily determined. An<br />
empirical approach to leaching salts from tlie soil using irrigation water is often used<br />
because tlie parameters are more easily determined:<br />
LR =<br />
ECw<br />
5 (E Q ) - E C ,<br />
(6)
Soil Fertilization attd Mineral Nutrition in U.S. Mechanized <strong>Rice</strong> Culture 395<br />
where LR is the leaching fraction required to control salts within the tolerance o f the<br />
specific crop, ECw the electrical conductivity (dS/m) o f the irrigation water, <strong>and</strong> E Q<br />
the electrical conductivity (dS/m) tolerated by a specific crop as measured from a<br />
saturation extract. Next, the am ount o f water required is given by<br />
A W :^<br />
ET<br />
1 - LR<br />
(7)<br />
where AW is the depth o f water to be applied annually (mm/yr), ET the annual crop<br />
water dem<strong>and</strong> for évapotranspiration (mm/yr), <strong>and</strong> LR the leaching requirement<br />
calculated in equation (6).<br />
LR has been used almost exclusively for leaching salts in arid <strong>and</strong> semiarid climates.<br />
Theory would suggest that salinity should not occur in humid climates because<br />
the rainfall should be sufficient to keep the salts leached from the soil profile. However,<br />
as discussed previously, properties inherent to rice soils inhibit leaching o f salts.<br />
Although leaching does occur on these soils, the low hydraulic conductivity o f many<br />
rice soils used in the southern United States restricts the effective use o f leaching as a<br />
means o f salt removal. For instance, a substantial number o f rice fields in the southern<br />
region are flooded for 3 to 6 months during the winter, <strong>and</strong> some o f these fields still<br />
contain enough soluble salts to cause injury to rice by the salt pump described earlier.<br />
Other Management Considerations. Typical management practices used prior to<br />
flooding in dry-seeded, delayed-flood rice to alleviate salt injm*y to rice seedlings is<br />
based on the assumption that dilution of salinity by saturating the soil pores will<br />
result in an overall reduction in salt concentration o f the soil solution. This is accom <br />
plished by flushing the field frequently with good-quality, low-salt irrigation water.<br />
In addition to the dilution effect, salts are moved downward in the profile out o f<br />
the rice root zone, but not necessarily out o f the soil profile. The perm anent flood is<br />
established as soon as the rice can tolerate the flood. Once the flood is established, the<br />
management practice often used is to mix a poor-quality water source with a good<br />
source, where available. It is com m on in some parts o f the southern United States to<br />
use good-quality surface water early in the season when the rice is sensitive to salinity<br />
<strong>and</strong> to supplement this with poorer-quality groundwater later in the season, when the<br />
surface water supply may be limited.<br />
Research has shown that reduced tillage may enhance salt accumulation during<br />
the seedling growth stage on soils that have a <strong>history</strong> o f salinity injury. Yield reductions<br />
o f as much as 20% have been measured as the result o f reduced tillage on soils that have<br />
a <strong>history</strong> o f salinity damage (Table 3.4.12) (W ilson et al., 2000a). The salt pump effect<br />
described previously appears to be enhanced due to more continuous soil pores in<br />
reduced tillage operations. Thus it m aybe advantageous to avoid conservation tillage<br />
practices on soils that have a <strong>history</strong> o f salinity injury.<br />
Alkaline Soil Management for <strong>Rice</strong> Production<br />
As defined previously, alkaline soils include those that have excessive Na (sodic soils)<br />
<strong>and</strong> those that have had excessive lime or calcium carbonate (CaCOs) deposited<br />
or calcareous soils. Although the soil pH is above 7.0 for both soils, the chemical<br />
<strong>and</strong> physical characteristics differ for tliese groups o f soils, <strong>and</strong> subsequently, the<br />
management o f rice on these soils differs as well.
396 Production<br />
T A B LE 3 .4.12.<br />
In flu e n c e o f T illa g e P ractices o n G r a in Y ie ld s, Salin ity, a n d C h lo rid e (Cl~)<br />
C o n c e n tra tio n in th e Top 2.5 cm o f th e S o il P ro file<br />
Salinity in Root Zone''<br />
<strong>Rice</strong> G rain Yield EC|,i Soil[C|-]<br />
Tillage Operation“ (kg/ha) (dS/m) (ctnol/kg)<br />
Conventional 7338 0.585 415<br />
Chisel plow 796.8 0.500 460<br />
Para-tiil 8030 0.485 443<br />
No-till 6548 0.775 966<br />
Source: Data from Wilson et al. (2000a).<br />
"Conventional, disk in fall <strong>and</strong> shallow tillage in spring; chisel plow, deep tillage followed by disk in fell,<br />
shallow tillage in spring; para-till, deep tillage followed by disk in fall, shallow tillage in spring; no-till, no<br />
tillage operations.<br />
'’Measured at two- to three-leaf growth stage.<br />
<strong>Rice</strong> Production on Calcareous Soils<br />
Arguably, the m ost widespread soil problem in the southern U.S. rice belt is the increase<br />
in soil pH as a result of using irrigation water that contains high concentrations<br />
of calcium bicarbonate [Ca(H C 0 3 )2]. Some o f the irrigation water sources are supersaturated<br />
with Ca(H C 03)2 . As this water is pumped onto the field, the water temperature<br />
increases <strong>and</strong> causes the solubility o f Ca(H C 03)2 to decrease. Thus, precipitation<br />
occurs <strong>and</strong> Ca(H C 03)2 is deposited onto the soils (Gilm our et al., 1978). Subsequently,<br />
the Ca(H C 03)2 is converted to CaCOs according to the following reaction:<br />
Ca(H C 03)2 ^ CaCOj + H 2O -h CO 2 (8)<br />
As this reaction proceeds, the soils are effectively limed <strong>and</strong> the soil pH increases.<br />
Because this reaction occurs relatively quickly, the CaCOs deposited causes an increase<br />
in soil pH near the water inlets <strong>and</strong> the effect diminishes as the water progresses across<br />
the field, resulting in a pH gradient down the slope o f the field. The soil pH gradient<br />
that develops across the field m aybe as much as 2.0 to 2.5 pH units.<br />
The primary problem associated with the increase in soil pH is the effects on<br />
nutrient availability. The elements most severely affected include Zn <strong>and</strong> P, although<br />
Fe <strong>and</strong> M n may also be affected. It is com m on to see deficiencies o f one or more<br />
o f these nutrients in rice produced on soils with this condition (M iller et al,, 1994).<br />
Nutrient management strategies on calcareous soils include reducing groundwater<br />
use or changing irrigation water sources, use of fertilizers to increase short-term<br />
nutrient availability, <strong>and</strong> reducing soil pH using acidifying amendments to increase<br />
nutrient availability. The most effective long-term strategy is to change the irrigation<br />
water source to reduce CaC0 3 application <strong>and</strong> allow natural <strong>and</strong> farmiirg processes<br />
to acidify the soil. Changing water sources often involves large capital investments<br />
<strong>and</strong>/or changing the irrigation infrastructure (i.e., removal o f l<strong>and</strong> from <strong>production</strong>,<br />
underground pipe, or botli) <strong>and</strong> has not been embraced as a popular strategy by many<br />
growers or is not an option in some rice-producing areas. Fertilizer costs are normally<br />
higher on calcareous soils because some fertilizer nutrients, such as P <strong>and</strong> Zn, usually
Soil Fertilizotion <strong>and</strong> Mineral Nutrition in U.S. Mechanized <strong>Rice</strong> Culture 397<br />
are not required on acid soils. Higher fertilizer rates <strong>and</strong> different application timings<br />
may be necessary to optimize productivity on these fields. However, in some cases,<br />
rice growth <strong>and</strong> yield are poor <strong>and</strong> do not respond to extra fertilizer applications.<br />
Soil acidification has proved effective for increasing rice growth <strong>and</strong> yield in many<br />
such cases.<br />
Acidification o f soil is normally performed using elemental S (S°). Research on<br />
calcareous silt loam soils in Arkansas has shown dramatic increases, from S“ application,<br />
in rice tissue nutrient concentrations o f Fe, M n, P, <strong>and</strong> Zn; dry-matter <strong>production</strong>;<br />
<strong>and</strong> grain yield (Slaton, 1998). The rate o f S“ required to reduce soil pH depends<br />
primarily on the amount o f soil CaCOa, tlie soil texture, <strong>and</strong> the oxidation rate o f<br />
the S“ product used. M ost o f the calcareous rice-producing soils in Arkansas contain<br />
less than 0.5% free CaCOa which is relatively low considering that some areas o f the<br />
world have soils with 20 to 40% CaCOs. Application o f 500 to 2000 kg S“/ha is required<br />
to reduce soil pH o f the calcareous silt loams in Arkansas below 7.0 (Slaton, 1998).<br />
A year or more may be required before soil pH is significantly reduced, as m ost S®<br />
products are manufactured as granules or pastilles that oxidize rather slowly (Slaton<br />
et al., 2001a). In contrast, application o f fine wettable powder formulations o f S“ may<br />
completely oxidize within a few weeks or m onths <strong>and</strong> reduce soil pH immediately, but<br />
use o f these products is limited, due to their caustic properties. Regardless o f the S“<br />
source, continued use o f irrigation water high in Ca(H C 03)2 will eventually increase<br />
soil pH to above 7,0, <strong>and</strong> additional S“ will need to be applied to neutralize the CaCOi<br />
<strong>and</strong> reduce soil pH. Use o f S° has been limited due to its high cost, highly effective<br />
inorganic fertilizer recommendations, <strong>and</strong> the relatively small area that is plagued by<br />
problematic calcareous soils.<br />
<strong>Rice</strong> Producfion on Sodic Soils<br />
Sodic soils tend to have a high pH <strong>and</strong> very poor physical properties. High amounts o f<br />
exchangeable Na affect rice growtli indirectly by causing poor soil physical properties<br />
<strong>and</strong> reduced nutrient availability associated with the high soil pH. Poor physical<br />
properties, such as lack o f soil structure, may make st<strong>and</strong> establishment more difficult.<br />
Sodic soils may <strong>origin</strong>ate from one o f two processes. Sodic soils may result from the<br />
parent materials involved in soil development <strong>and</strong> be further enhanced by the factors<br />
o f soil form ation. This may cause soils to develop with sodic layers at varying depths in<br />
the profile. Those soils that develop sodic layers at or near the surface are not com m on<br />
but do exist in the United States. M ore commonly, the sodic layers are deep enough in<br />
the soil profile that they present few problems unless exposed by l<strong>and</strong> forming. The<br />
depth to those layers is often a m ajor characteristic used to distinguish these soils. The<br />
second process that may contribute to tlie development o f sodic soils is irrigation witli<br />
water containing high concentrations o f Na.<br />
The purpose o f reclaiming sodic soils is to improve soil structure, which subsequently<br />
improves water permeability, soil aeration, <strong>and</strong> water-holding capacity. This is<br />
usually accomplished by replacing Na on tlie cation-exchange complex with Ca. To be<br />
effective, this process requires an adequate source o f calcium <strong>and</strong> an adequate amount<br />
o f leaching. Although potentially, m ost Ca sources can serve the purpose o f providing<br />
Ca to the soil, the m ost com m on source is gypsum (CaS0 4 ). Gypsum is often used as<br />
the st<strong>and</strong>ard to which all other sources are compared. Other potential sources include<br />
CaCOs. CaCb, or irrigation water containing high concentrations o f Ca.
398 Production<br />
The conventional method for calculating the amount o f a particular amendment<br />
required is by determining the gypsum requirement, which is given by;<br />
kg CaS04 h a-i = 8.5 {dDhE,(SARi = SAR^) (9)<br />
llrii<br />
where d is the depth o f the soil to be reclaimed (expressed in meters), Db the bulk<br />
density of the soil in question (expressed in Mg/m“^),<br />
the cation-exchange capacity<br />
(expressed in mmol(c)/kg), SAR,- the initial sodium adsorption ratio, <strong>and</strong> SAR^-<br />
the final sodium adsorption ratio. This calculated rate of CaS04 must be adjusted<br />
stoichiometrically for other amendments. Also, the final rate must be adjusted for<br />
inefficiencies in the cation-exchange equilibria. A value o f 1.25 is often used. But<br />
variability in efficiency has been .seen between soils <strong>and</strong> between sources (Rhoades<br />
<strong>and</strong> Loveday, 1990).<br />
Although the m ost effective method for reclaiming sodic soils is by application of<br />
CaS04 to replace exchangeable Na followed by irrigation with good-quality irrigation<br />
water, other amendments have been shown to be beneficial. Additions o f poultry<br />
litter, either fresh or composted, to soils that have recently been precision-graded has<br />
increased productivity on these soils by as much as 300% (Miller et al., 1991). Exposed<br />
sodic horizons were present on some o f the soils where this research was conducted..<br />
Restoration o f productivity on these soils by applications o f poultry litter has not been<br />
understood completely; however, research suggests that alkaline soils are more likely<br />
to respond favorably to litter than are saline soils (Miller et al., 1994).<br />
RECLAIVIATION AND FE R T IL IZ A T IO N O F P R E C IS IO N G R A D ED S O IL S<br />
L<strong>and</strong> forming during the past 20 years has increased dramatically in many areas of the<br />
southern U.S. rice belt. The process has several benefits that are both agronomicaUy<br />
<strong>and</strong> environmentally sound. Precision grading results in the need for fewer levees;<br />
facilitates improved water, fertilizer, <strong>and</strong> herbicide efficiency; <strong>and</strong> reduces overall<br />
water use. However, a decrease in productivity often results from precision-grading<br />
o f sût <strong>and</strong> s<strong>and</strong>y loam soils. W hen soils are precision-graded, topsoil is removed<br />
from areas o f higher elevation <strong>and</strong> deposited in ai*eas o f lower elevation. The subsoil<br />
material that is exposed or moved may be undesirable, such as sodic horizons, or<br />
perhaps unproductive <strong>and</strong> difficult to manage for other reasons (Daniels et al., 1998).<br />
The degree o f lost productivity <strong>and</strong> potential need for reclamation on these fields are<br />
usually related to the depth o f soil disturbance. Routine soil testing is often unable to<br />
identify specific nutrient(s) that would lim it plant growtli in these fields. However,<br />
subsoil samples collected prior to leveling may often reveal potential problems that<br />
will be encountered (Daniels et al., 1998).<br />
Mthough crop productivity is reduced substantially following l<strong>and</strong> forming on<br />
many o f the soils in the region, some soils are not affected as adversely. For example,<br />
the alluvial Vertisols found in the Mississippi Delta typically do not exhibit substantial<br />
loss in productivity. Topsoil <strong>and</strong> subsoil characteristics are typically not drastically<br />
different. However, the variability among soils dictates the need to underst<strong>and</strong> as<br />
much as possible about the soils prior to removing topsoil. Management o f rice in<br />
fields where the soil characteristics have been altered by l<strong>and</strong> forming can be uncertain
Soil Fertilization <strong>and</strong> Mineral Nutrition in U.S. Mechanized <strong>Rice</strong> Culture 399<br />
during the first few years o f <strong>production</strong>, because o f the spatial variability within fields<br />
as well as within regions.<br />
Application o f poultry litter, either fresh or composted, has been shown to be<br />
the most effective means o f quickly restoring rice productivity to soils that have been<br />
altered by precision grading (M iller et al., 1990, 1991). Although poultry litter is a<br />
source o f P <strong>and</strong> K on undisturbed soils, the prim ary benefit o f litter is restoring lost<br />
productivity on precision-leveled soils. In m ost leveled fields, poultry litter rates o f<br />
1120 kg/ha (dry weight basis) or more are needed to restore productivity consistently<br />
to affected soils (M iller et a l, 1991). Fresh litter <strong>and</strong> composted litter produce equal<br />
yield responses, with no advantage in rates needed for either source (Table 3.4.13).<br />
In addition, spring applications o f litter tend to produce higher rice yields than do<br />
fall applications o f equal amounts. Since timing o f poultry litter influences yield response,<br />
the frequency o f litter applications is also im portant to maximize <strong>production</strong><br />
in future years.<br />
A single application o f litter after leveling produces higher yields for several years<br />
than do leveled areas that did not receive any litter. Although litter has a small residual<br />
effect <strong>and</strong> may increase <strong>production</strong> for several years, the best response occurs the first<br />
year after application <strong>and</strong> generally declines with time. The optimum approach is<br />
to apply sequential applications to maintain productivity in subsequent years after<br />
l<strong>and</strong> leveling. Soils that have been disturbed at significant depths ( > 15 cm) typically<br />
require more litter <strong>and</strong> more annual applications to restore productivity than do<br />
shallower soil alterations. Soils that have minimal disturbance may require two annual<br />
applications o f litter, while soils that have deeper alterations may require annual<br />
applications for as long as 5 years.<br />
Routine soil testing seldom identifies fertility problems on disturbed soils. However,<br />
soil testing is a critical step in identifying potential nutrient needs <strong>and</strong> potential<br />
salinity <strong>and</strong> sodicity hazards. Research suggests that the predominant nutrient deficiency<br />
on disturbed soils is P (Table 3.4.14). Furtherm ore, the data indicate that application<br />
of both litter <strong>and</strong> P is likely to produce yields in excess o f those obtained when<br />
either material is applied alone. Therefore, P is normally recommended in addition<br />
T A B L E 3 .4 .1 3 .<br />
In flu e n c e o f B r o ile r Litter S o u rc e a n d T im o o f A p p lic a tio n o n G ra in Y ie ld s o f<br />
L e m o n t <strong>Rice</strong> P ro d u c e d o n P r e c is io n -G r a d e d S o ils, 1 9 9 2<br />
Grain Y ie ld " (kg/ha)<br />
Litter Rale<br />
Litter Source<br />
Litter Application Time^<br />
(kg/ha)<br />
Fresh Coinposted Fall Spring<br />
0 1865<br />
1120 4344 4738 2923 4344<br />
2240 4990 5191 3982 4990<br />
4480 5594 5544 4032 5594<br />
6720 5141 5141 4435 5141<br />
Source: Unpublished data of D. M. Miller, B. R. Wells, <strong>and</strong> R. J. Norman.<br />
"Field seeded on June 16, 1992.<br />
^Fresh litter applied Oct. 1991 (fall) <strong>and</strong> June 1992 (spring).
400 Production<br />
T A B L E 3.4 .1 4 .<br />
Ríce Y ie ld R e s p o n s e o n P r e c is io n -G r a d e d S ih L o a m S o ils to P o u ltry Litter a n d<br />
P Fertilizer at T h re e L o catio n s, 1 9 8 9<br />
G rain Yield (kg/ha)<br />
Treatment"<br />
Lewis Farm C onnorl Farm Connor2 Farm<br />
Control 2016 5342 4435<br />
22kgP/ha 2621 6250 6098<br />
2240kgP.L./ha 5746 6502 7157<br />
22 kg P/ha + 2240 kg P.L./ha 5090 6804 8266<br />
Source: Data from Miller et al. (1990).<br />
"P.L., poultry litter.<br />
to poultry litter amendments. Other inorganic fertilizers (Le., CaS0 4 , K, or Zn) have<br />
in some cases increased the productivity o f disturbed soils (M iller et al„ 1990,1991).<br />
However, compared to poultry litter, yield responses to commercial fertilizers have<br />
been inconsistent <strong>and</strong> not always as great as those from poultry litter applications<br />
(M iller et al., 1991). Although poultry litter applications have been successful at reclaiming<br />
lost productivity to precision-leveled soils, all o f the factors involved have<br />
not been determined. The inconsistent results from specific inorganic amendments<br />
suggests that other factors, such as soil physical <strong>and</strong> biological properties, may be<br />
involved. More research is needed to underst<strong>and</strong> completely all the relationships between<br />
poultry litter <strong>and</strong> disturbed soil amelioration.<br />
Recommended N fertilizer rates for the various rice cultivars should be utilized<br />
despite the application o f recommended amounts o f poultry litter. The reasoning<br />
behind this is that (1) poultry litter averages only 40 g N/kg (Table 3.4.15) <strong>and</strong> with<br />
application rates of 1100 kg/ha, only about 45 kg N/ha is applied; (2) the poultry<br />
litter is applied preplant <strong>and</strong> the inorganic N contained in the litter as weU as the N<br />
mineralized from the litter is subject to loss mechanisms (i.e., N H 3 volatilization <strong>and</strong><br />
nitrification-denitrification) similar to fertilizer N applied preplant; (3) an appreciable<br />
amount of the N in poultry is organic N <strong>and</strong> will not all be mineralized during<br />
the growing season; <strong>and</strong> (4) graded soils have lower organic matter <strong>and</strong> thus lower<br />
amounts o f potentially mineralizable native soil N than do typical undisturbed soils.<br />
Consequently, N fertilizer rates for rice should be adjusted only when extremely high<br />
rates o f litter are applied immediately prior to planting.<br />
TA B LE 3.4.15.<br />
T ypical C o n c e n tra tio n s o f N, B K, a n d Z n in B ro ile r Litter<br />
R ange (g/kg)<br />
Element M e a n (g / k g ). Low H igh<br />
N 40.8 17,0 68.0<br />
P 14.3 8.0 26.0<br />
K 20.7 13,0 46.0<br />
Zn 0.2 0,1 0.25<br />
Source: Data from Edwards <strong>and</strong> Daniel (1992).
Soil Fertilization ond Mineral Nutrition in U.S, Mechanized <strong>Rice</strong> Culture 401<br />
references<br />
Anderson, D. L., D, B. Jones, <strong>and</strong> G. H, Snyder. 1987. Response o f rice-sugarcane<br />
rotation to calcium silicate slag on Everglades Histosols. Agron /. 79:531-535.<br />
Bartholomew, R. P. 1931. Changes in the availability o f phosphorus in irrigated rice<br />
soils. SoJ/Sci. 31:209-218.<br />
Baser, R. E., <strong>and</strong> J. T. Gilmour. 1982. Tolerance of <strong>Rice</strong> Seedlings to Potassium Salts.<br />
Univ. Ark. Agrie. Exp. Stn. Bull. 860.<br />
Bashir, R. 1999. Effect o f water management <strong>and</strong> soil salinity on the distribution of<br />
fertilizer ^®Zn in alkaline soils <strong>and</strong> uptake by rice. Ph.D. dissertation. University<br />
o f Arkansas, Fayetteville, AR.<br />
Beacher, R. L, 1952. <strong>Rice</strong> Fertilization: Results of Tests from 1946 through 1951. Univ.<br />
Ark. Agrie. Exp. Stn. Bull. 522.<br />
BeU, P. F., <strong>and</strong> J. L. Kovar. 2000. <strong>Rice</strong>. In C. R. Campbell (ed.), Reference Sufficiency<br />
Ranges for Plant Analysis in the Southern Region of the United States [Online].<br />
South. Coop. Serv. BuU.; 394, July. Available at http://www.agr.state.nc.us/<br />
agronomi/saaesd/s394/htm (verified Nov. 10, 2000).<br />
Beyrouty, C. A., B. R. Wells, R. J. Norman, J. N. Marvel, <strong>and</strong> J. A. Pillow. 1987. Characterization<br />
o f rice roots using a m inirhizotron technique. In N. M Taylor (ed.),<br />
Minirhizotron Observation Tubes: Methods <strong>and</strong> Applications for Measuring Rhizosphere<br />
Dynamics. ASA Spec. Publ. 50. American Society o f Agronomy, Madison,<br />
W I, pp. 99-108.<br />
Beyrouty, C. A., R .J. Norman, B. R. Wells, E. E. Gbur, B. C. Grigg; <strong>and</strong> Y. H. Teo. 1992.<br />
Water management <strong>and</strong> location effects on root <strong>and</strong> shoot growth o f irrigated<br />
lowl<strong>and</strong> rice. /. Plant Nutr. 15:737-752.<br />
Beyrouty, C. A., B. C. Grigg, R. J. Norman, <strong>and</strong> B. R. Wells. 1994. Nutrient uptake by<br />
rice in response to water management. /. Plant Nutr. 17:39-55.<br />
Bollich, P. K. 1995. Fertilizer nitrogen management in drill-seeded, stale seedbed rice.<br />
Proc. Southern Conserv. Tillage Conf. Sustain. Agrie. 1995:82-85.<br />
Bollich, P. K., W. J. Leonerds, Jr., <strong>and</strong> D. M. WaUcer. 1990. Nitrogen management in<br />
furrow irrigated Lem ont rice. In 82nd Annual Research Report. <strong>Rice</strong> Research Station,<br />
Louisiana State University Agricultural Experiment Station, Baton Rouge,<br />
LA, pp. 157-161.<br />
BoUich, P. K., C. W. Lindau, <strong>and</strong> R. J. Norman. 1994. Management o f fertiliser nitrogen<br />
in dry-seeded, delayed-flooded rice. Aust. J. Exp. Agrie. 34:1007-1012.<br />
Bollich, P. K., R. P. Regan, G. R. Romero, <strong>and</strong> D. M. Walker. 1997. <strong>Rice</strong> fertilization<br />
<strong>and</strong> cultural management. In 89th Annual Research Report. <strong>Rice</strong> Research Station,<br />
Louisiana State University Agricultural Experiment Station, Baton Rouge, LA,<br />
pp. 106-228.<br />
Bollich, P. K., R. P. Regan, G. R. Romero, <strong>and</strong> D. M'. Walker. 1998a. Influence o f tillage<br />
<strong>and</strong> nitrogen on rice variety performance. Proc. 27th <strong>Rice</strong> Tech. Work. Group<br />
1998:172-173.<br />
BoUich, P. K., R. P. Regan, G. R. Romero, <strong>and</strong> D. M. Walker. 1998b. Nitrogen m anagement<br />
in stale-seedbed, water-seeded rice. Proc. 27th <strong>Rice</strong> Tech. Work. Group<br />
1998:198-199.<br />
Bollich, P. K., R. P. Regan, G. R. Romero, <strong>and</strong> D. M . Walker. 1998c. <strong>Rice</strong> fertilization<br />
<strong>and</strong> cultural management. In 90th Annual Research Report. <strong>Rice</strong> Research Station,
402 Production<br />
Louisiana State University Agricultural Experiment Station, Baton Rouge, LA,<br />
pp. 90-190.<br />
BoUich, R K., R. R Regan, G. R. Romero, <strong>and</strong> D. M. Walker. 2000. Potential use of<br />
slow-release urea in water-seeded, stale seedbed rice. Proc. South. Conserv. Tillage<br />
Conf. Sustain. Agric. 2000:70-79.<br />
Br<strong>and</strong>on, D. M ., <strong>and</strong> D. S. Mikkelsen. 1979. Phosphorus transformations in alternately<br />
flooded California soils. I. Cause o f plant phosphorus deficiency in rice<br />
rotation crops <strong>and</strong> correctional methods. Soil Sei. Soc. Am. J. 43:989-994.<br />
Br<strong>and</strong>on, D. M ., <strong>and</strong> B. R. Wells. 1986. Improving nitrogen fertilization in mechanized<br />
rice culture. In S. K De Datta <strong>and</strong> W. H. Patrick (eds.). Nitrogen Economy of<br />
Flooded <strong>Rice</strong> Soils. M artinus Nijhoff, Dordrecht, The Netherl<strong>and</strong>s, pp. 161-170.<br />
Bray, R. H., <strong>and</strong> L. T. Kurtz. 1945. Determ ination o f total, organic, <strong>and</strong> available forms<br />
o f phosphate in soils. Soil Sei 59:39-45.<br />
Bresler, E., B. L. McNeal, <strong>and</strong> D. L. Carter. 1982. Saline <strong>and</strong> Sodic Soils: Principles-<br />
Dynamics-Modeling. Springer-Verlag, Berlin.<br />
Bufogle, A., Jr., P. K. BoUich, J. L. Kovar, C. W. Lindau, <strong>and</strong> R. E. Macchivelli. 1997a.<br />
<strong>Rice</strong> plant growth <strong>and</strong> nitrogen accumulation from midseason application. /.<br />
Plant N u tr.2 0 :im -m i.<br />
Bufogle, A., Jr., P. K. Bollich, J. L. Kovar, R. E. Macchivelli, <strong>and</strong> C. W. Lindau. 1997b.<br />
<strong>Rice</strong> variety differences in dry matter <strong>and</strong> nitrogen accumulations as related to<br />
plant stature <strong>and</strong> m aturity group. /. Plant Nutr. 20:1203-1224.<br />
Bufogle, A., Jr., P. K. Bollich, R. J. Norman, J. L. Kovar, C. W. Lindau, <strong>and</strong> R. E.<br />
Macchivelli. 1997c. <strong>Rice</strong> plant growth <strong>and</strong> nitrogen accumulation in drill-seeded<br />
<strong>and</strong> water-seeded culture. Soil Sfi Soe. Am. J. 61:832-839.<br />
Bufogle, A., Jr., P. K, Bollich, J. L. Kovar, C. W. Lindau, <strong>and</strong> R. E. Macchivelli. 1998.<br />
Comparisons of amm onium sulfate <strong>and</strong> urea as nitrogen sources in rice <strong>production</strong>.<br />
J. Plant Nutr. 21:1601-1614.<br />
Cartwright, R. D., N. A. Slaton, <strong>and</strong> R. J. Norman. 2000. Effect o f nitrogen rate <strong>and</strong><br />
application timing on sheath blight o f rice in Arkansas. Proc, 28th <strong>Rice</strong> Tech. Work,<br />
Group 2000:74.<br />
Chang, S, C., <strong>and</strong> M . L. Jackson. 1957. Fractionation of soil phosphorus. Soil Sei<br />
84:133-144.<br />
Chen, C. C., F. T, Turner, <strong>and</strong> J. B. Dixon. 1989. Ammonium fixation by high-charged<br />
smectite in selected Texas gulf coast soils. Soil Sei Soe. Am. J. 53:2035-1040.<br />
Counce, P. A., B, R. Wells, <strong>and</strong> K. A. Gravois. 1992. Yield <strong>and</strong> harvest-index responses<br />
to preflood nitrogen fertilization at low rice plant populations. J. Prod. Agric.<br />
5:492-497.<br />
Daniels, M. B., S. L. Chapman, R. Matlock, <strong>and</strong> A. Winfrey. 1998. Using grid soil<br />
sampling in the management o f problem soils. In W. E. Sabbe (ed.), Arkansas<br />
Soil Fertility Studies, 1997. Univ. Ark. Agric. Exp. Stn. Res. Sen 459, pp. 24-28.<br />
DatnofF, L. E., R. N. Raid, <strong>and</strong> G. H, Snyder. 1991. Effect o f calcium silicate on blast<br />
<strong>and</strong> brown spot intensities <strong>and</strong> yields o f rice. Plant Dis. 75:729-732.<br />
da Silva, P. R. F., <strong>and</strong> C. A. Stutte. 1981. Nitrogen loss in conjunction with transpiration<br />
from rice leaves as influenced by growth stage, leaf position, <strong>and</strong> nitrogen<br />
supply. Agron.}. 73:38-42.<br />
DatnolOi, L. E., G. H. Snyder, <strong>and</strong> C. W. Deren, 1992. Influence o f silicon fertilizer<br />
grades on blast <strong>and</strong> brown spot development <strong>and</strong> on rice yields. Plant Dis. 76:<br />
1182-1184.
FIGURE 3.5.1. Water mold. (Photo by Don Groth.)<br />
FIGURE 3.5,2. Root rot. (Photo by Don Groth.)<br />
FIGURES 3.5.3. Initiol sheath blight lesions. (Photo by Don Groth.)<br />
FIGURE 3.5.4. Sheath blight lesions on leaves, (Photo by Don Groth.)<br />
FIGURE 3.5.5. Sheath blight on head. (Photo by Don Groth.)
FiGURE 3.5.12, Node blast. (Photo by Don Grotb.)<br />
I !<br />
FIGURE 3.5.13. Brown spot. (Photo by Don FIG URE 3.5.14. Narrow brown leaf spot. FIGURE 3.5.15. Alternaria leaf spot. (Photo<br />
Grotb.) (Photo by Don Grotb.) by Don Grotb.)<br />
FI-j URE 3.5.16. Bacterial bligbt. (Photo by Don Groth.)
fig u r e 3,6.1. Fall annyw om larva (note inverted Y on head). (Photo by FIGURE 3.6.2, Chinch bug odufe on seedlinq rice (Photo bv M 0<br />
M.O.W ay.)<br />
Way.)
p i<br />
FIGURE 3.6.11. Mexican rice<br />
M. 0. Way.)<br />
SI<br />
FIGURE 3.6.13.AerioUiew of rice
Soil Fertilization <strong>and</strong> Mineral Nutrition in U.S. ft/iechanized Rke Cullure<br />
De Datta, S, K. 1981. Principles <strong>and</strong> Practices of <strong>Rice</strong> Production. Wiley^Interscience,<br />
New York.<br />
DeLong, R. E., S. D. CarroE, S. L. Chapman, W. E. Sabbe, <strong>and</strong> W. H. Baker. 1999. Soil<br />
testing <strong>and</strong> fertilizer sales data: summary for the growing season, 1998. In W. E.<br />
Sabbe (ed.), Arkansas Soil Fertility Studies, 1998. Univ. Ark. Agric. Exp. Stn. Res.<br />
Ser. 463, pp. 9 -24.<br />
Deren, C. W., L. E. Datnoff, <strong>and</strong> G. H. Snyder. 1992. Variable silicon content of rice<br />
cultivars grown on Everglades Histosols. /. Plant Nutr. 1 5 (ll):2 3 6 3 -2 3 6 8 .<br />
Deren, C. W., L. E. Datnoff, G. H. Snyder, <strong>and</strong> R G. Martin. 1994. Silicon concentration,<br />
disease response, <strong>and</strong> yield components o f rice genotypes grown on flooded<br />
organic Histosols. Crop Sci. 34:733-737.<br />
Eagle, A. J., J. A. Bird, W. R. Horwath, B. A. Linquist, S. M. Brouder, J. E. Hill,<br />
<strong>and</strong> C. van Kessel. 2000. <strong>Rice</strong> yield <strong>and</strong> nitrogen utilization efficiency under<br />
alternative straw management practices. Agron. J. 92:1096-1103.<br />
Edwards, D. R., <strong>and</strong> T. C, Daniel. 1992. Environmental impacts on on-farm poultry<br />
waste disposal: A review. Bioresource Technol 41:9 -3 3 .<br />
Engler, R. M ., <strong>and</strong> W. H. Patrick. 1975. Stability o f sulfides o f manganese, iron, zinc,<br />
copper <strong>and</strong> m ercury in flooded <strong>and</strong> nonflooded soil. Soil Sci 119:217-221.<br />
Foster, E. F., <strong>and</strong> C. A. Stutte. 1986, Glutamine synthetase activity <strong>and</strong> foliar nitrogen<br />
volatilization in response to temperature <strong>and</strong> inhibitor chemicals. Ann. Bot.<br />
(London) 57:305-307.<br />
Gilmour, J. T. 1977a. M icronutrient status o f the rice plant. I. Plant <strong>and</strong> soil concentrations<br />
as a fiinction o f tim e. Plant Soil 46:549-557.<br />
Gilmour, J. T. 1977b. M icronutrient status o f the rice plant. II. M icronutrient uptake<br />
rate as a function o f time. Plant Soil 46:559-564.<br />
Gilmour, J. T., K. S. Shirk, J. A. Ferguson, <strong>and</strong> C. L. Griffis. 1978. A kinetic study of<br />
the CaC03 precipitation reaction. Agric. Water Manag. 1:253-262.<br />
Gilmour, J. T., A. Mauromoustakos, P. M . Gale, <strong>and</strong> R. J. Norman. 1998. Kinetics<br />
o f crop decomposition: variability among crops <strong>and</strong> years. Soil Sci. Soc. Am. J.<br />
62:750-755.<br />
Giordano, P. M ., <strong>and</strong> J. J. Mortvedt. 1972. <strong>Rice</strong> response to Zn in flooded <strong>and</strong> nonflooded<br />
soil. Agron, J. 64:521-524.<br />
Giordano, P. M ., <strong>and</strong> J. J. Mortvedt. 1974. Response o f several rice cultivars to Zn.<br />
Agron.}. 66:220-223.<br />
Grigg, B. C., C. A. Beyrouty, R. J. Norman, E. E. Gbur, M . G. Hanson, <strong>and</strong> B. R. Wells.<br />
2000. <strong>Rice</strong> responses to changes in flood water <strong>and</strong> N timing in southern USA.<br />
Field Crops Res. 66:73-79.<br />
Guindo, D., R. J. Norm an, <strong>and</strong> B. R. Wells. 1994a. Accumulation of fertilizer nitrogen-<br />
15 by rice at different stages o f development. Soil Sci Soc. Am. J. 58:410-415.<br />
Guindo, D., B. R. WeUs, <strong>and</strong> R. J. Norman. 1994b. Cultivar <strong>and</strong> nitrogen rate influence<br />
on nitrogen uptake <strong>and</strong> partitioning in rice. Soil Sci Soc. Am. J. 58:840-845.<br />
Hefner, S. G., <strong>and</strong> P. W. Tracy. 1991a. Effects o f nitrogen source, application timing,<br />
<strong>and</strong> dicy<strong>and</strong>iamide on furrow irrigated rice. /. Prod. Agric. 4:536-540.<br />
Hefner, S, G., <strong>and</strong> P. W Tracy. 1991b, The effect o f nitrogen quantity <strong>and</strong> application<br />
timing on furrow irrigated rice. J. Prod. Agric. 4:541-546.<br />
Helms, R. S., T. J. Siebenmorgan, <strong>and</strong> R. J. Norman. 1987. The influence o f uneven<br />
preflood nitrogen distribution on grain yields o f rice. Univ. Ark. Farm Res.<br />
36(2) :9.
Production<br />
Hill, J. E„ S. R. Roberts, D. M . Braiidon, S. C. Scardad, J, E Williams, C, M . Wick,<br />
W. M. Canevai'i, <strong>and</strong> B. L. Weir. 1992. <strong>Rice</strong> Production in California. Univ. Calif.<br />
Div. Agrie. Nat. Resources Publ. 21498.<br />
JongkaevAvattana, S., S. Geng, D. M . Br<strong>and</strong>on, <strong>and</strong> J. E. Hill. 1993. Effect o f nitrogen<br />
<strong>and</strong> harvest grain moisture on head rice yield. Agron. J. 85:1143-1146.<br />
Kaboneka, S. 1998. Effect of previous crop on n mineralization <strong>and</strong> immobilization<br />
during decomposition o f plant materials in soil. Ph.D. dissertation. University o f<br />
Arkansas, FayettevEle, AR.<br />
Keerthisinghe, G„ K. Mengel, <strong>and</strong> S. K. DeDatta. 1984. The release o f nonexchangeable<br />
am m onium in wetl<strong>and</strong> rice soils. Soil Sei Soc. Am. J. 48:291-294.<br />
Korndörffer, G. H., G. H. Snyder, M. Ulloa, G. Powell, <strong>and</strong> L. E. Datnoff. 2001.<br />
Calibration o f soil <strong>and</strong> plant silicon analysis for rice <strong>production</strong>. /, Plant Nutr.<br />
24:1071-1084.<br />
Lee, E N., R. D, Cartwright, N. A. Slaton, S. Ntamatungiro, C. E. Parsons, B. L,<br />
C<strong>and</strong>óle, <strong>and</strong> E, Gbur. 2000. Silicon soil amendments do not increase rough rice<br />
yield or reduce rice sheath blight severity. In R. J. Norman <strong>and</strong> C. A. Beyrouty<br />
(eds.),;B. R. Wells <strong>Rice</strong>,Research Studies, 1999. Univ. Ark. Agrie. Exp. Stn. Res. Ser.<br />
476, pp. 469-474.<br />
Letey, J. 1984. Im pact o f salinity on the development o f soil science. In I. Shainberg<br />
<strong>and</strong> J. Shalhevet (eds.), Soil Salinity under Irrigation: Processes <strong>and</strong>.Management.<br />
Springer-Verlag, Berlin, pp. 1-11.<br />
Lindsay, W. L. 1979. Chemical Equilibria in Soils. Wiley, New York.<br />
Liscano, J. E, C, E. Wilson, Jr,, R. J. Norman, <strong>and</strong> N. A. Slaton. 2000. Zinc Availability<br />
to <strong>Rice</strong> from Seven Granular Fertilizers. Univ. Ark. Agrie. Exp. Stn. Res. Bui. 963.<br />
Long, D. H., D. O. TeBeest, <strong>and</strong> E N. Lee. 1997. The effect o f nitrogen fertilization on<br />
the epidemiology of rice blast disease in smaU plots in Arkansas. In R. J. Norman<br />
<strong>and</strong>T.H . Johnston (eds.), B.R. Wells <strong>Rice</strong> Research Studies, J995.U n iv Ark. Agrie.<br />
Exp. Stn. Res, Ser. 456, pp. 94-108.<br />
Marschner, H., 1995. Mineral Nutrition of Higher Plants, 2nd ed. Academic Press, San<br />
Diego, CA.<br />
McCauley, G. N. 1990. Sprinlder vs. flood irrigation in traditional rice <strong>production</strong><br />
regions o f south-east Texas. Agron. J. 82:677-683.<br />
McCauley, G. N., <strong>and</strong> E T. Turner. 1979. <strong>Rice</strong> <strong>production</strong> <strong>and</strong> water use efficiency in<br />
relation to flood period. Agron. Abstr. 1979:105.<br />
Mikkelsen, D. S. 1970. Recent advances in rice plant tissue analysis. <strong>Rice</strong> J. 73:2-5.<br />
Mückelsen, D. S. 1987. Nitrogen budgets in flooded soils used for rice <strong>production</strong>.<br />
Plant Soil 100\71-97.<br />
MÜdcelsen, D. S., <strong>and</strong> D. M. Br<strong>and</strong>on, 1975. Zinc deficiency in California rice. Calif.<br />
Agrie. (Sept.).<br />
Milikelsen, D. S., S. K. De Datta, <strong>and</strong> W. N. Ob cernea. 1978. Ammonia volatilization<br />
losses from flooded rice soüs. Soil Sei Soc. Am.}. 42:725-730.<br />
Miller, D, M ., B. R. Wells, R. J. Norman, <strong>and</strong> T. Alvisyahrin. 1990. Fertilization o f rice<br />
on leveled soils. In W. E. Sabbe (ed.), Arkansas Soil Fertility Studies, 1989. Univ.<br />
Arkansas Agrie. Exp. Stn. Res. Ser. 398, pp. 4 5 -48.<br />
Miller, D. M., B. R, Wells, <strong>and</strong> R. J. Norman. 1991. Fertilization of rice on graded soils<br />
using organic materials. In W. E. Sabbe (ed.), Arkansas Soil Fertility Studies, 1990.<br />
Univ. Ark. Agrie. Exp. Stn. Res. Ser. 411, pp. 55-58.<br />
Miller, D. M., C. A. Beyrouty, D. Stephens, R. J. Norman, M . A. Messis, B. R. Wells,
Soil Fertilization <strong>and</strong> Mineral Nutrition in U . l Mechanized Ríce Culture 405<br />
C. E. W ilson, <strong>and</strong> R. S. Helms. 1994. <strong>Rice</strong> <strong>production</strong> on salt-affected soils. In<br />
B. R. Wells (ed.), Arkansas <strong>Rice</strong> Research Studies, 1993. Univ. Arle. Agrie. Exp. Stn.<br />
Res. Ser. 439, pp. 158-164,<br />
Moore, R D. 1972. Mechanisms o f m icronutrient uptake by plants. In J. J. Mortvedt, P.<br />
M. Giordano, <strong>and</strong> W. L. Lindsay (eds.), Micronutrients in Agriculture. Soil Science<br />
Society o f America, Madison, W I, pp. 171-198.<br />
Moore, P. A., Jr., J. T. Gilmour, <strong>and</strong> B, R. Wells. 1981. Seasonal patterns o f growüi <strong>and</strong><br />
soil nitrogen uptake by rice. Soil Sci. Soc. Am. J. 45:875-879,<br />
M oore, P. A., K. K, Baugh, <strong>and</strong> B. R. Wells. 1992a. Effects o f salinity on rice growth <strong>and</strong><br />
processes that occur in flooded soils. In B. R Wells (ed.), Arkansas <strong>Rice</strong> Research<br />
Studies, 1991. Univ. Arkansas Agrie. Exp. Stn. Res. Ser. 422, pp. 134-141.<br />
Moore, P, A., Jr., R. J. Norman, B. R. Wells, K. K, Baugh, <strong>and</strong> R. S. Helms, 1992b.<br />
Changes in the nutrient content o f rice irrigation water with flow distance across<br />
the field <strong>and</strong> with the addition o f fertilizers to the crop. In B. R Wells (ed.),<br />
Arkansas <strong>Rice</strong> Research Studies, 1991. Univ. Arkansas Agrie, Exp. Stn. Res. Ser,<br />
422, pp. 83-88.<br />
Moore, P, A., K. K. Baugh, <strong>and</strong> B. R. Wells. 1993. Effects o f salinity on rice growth <strong>and</strong><br />
processes that occur in flooded soils. In B. R Wells (ed.), Arkansas <strong>Rice</strong> Research<br />
Studies, 1992. Univ, Arkansas Agrie, Exp. Stn. Res. Ser. 431, pp. 153-159.<br />
Nommik, H., <strong>and</strong> K. Vahtras. 1982. Retention <strong>and</strong> fixation o f ammonium <strong>and</strong> am <br />
monia in soils. In R J. Stevenson (ed.). Nitrogen in Agriculture Soils. A SA -C SSA -<br />
SSSA, Madison, W I, pp. 123-172.<br />
Norman, R. J., <strong>and</strong> J. T. Gilmour. 1987. Utilization o f anhydrous ammonia fixed by<br />
clay minerals <strong>and</strong> soil organic matter. Soil Sci. Soc. Am. J. 51:959-962.<br />
Norman, R. J., L. T. Kurtz, <strong>and</strong> P. J. Stevenson. 1987. D istribution <strong>and</strong> recovery o f<br />
nitrogen-15-labeled liquid anhydrous am m onia among various soil fractions.<br />
Soil Sci. Soc. Am. J. 51:235-241.<br />
Norman, R. J,, B. R, Wells, <strong>and</strong> R. S. Helms. 1988, Effect o f nitrogen source, application<br />
time <strong>and</strong> dicy<strong>and</strong>iamide on rice yields. /. Fert. Issues 5:78-82.<br />
Norman, R. J., B. R. Wells, <strong>and</strong> K. A. K. Moldenhauer. 1989. Effect o f application<br />
method <strong>and</strong> dicy<strong>and</strong>iamide on urea-nitrogen-15 recovery in rice. Soil Sci. Soc.<br />
Am. 7.53:1269-1274.<br />
Norman, R. J., J. T. Gilmour, <strong>and</strong> B. R. Wells. 1990. Mineralization o f nitrogen from<br />
nitrogen-15 labeled crop residues <strong>and</strong> utilization by rice. Soil Sci Soc. Am. J.<br />
54:1351-1356.<br />
Norman, R. J., D. Guindo, B. R. Wells, <strong>and</strong> C. E. Wilson, Jr. 1992a. Seasonal accumulation<br />
<strong>and</strong> partitioning o f nitrogen-15 in rice. Soil Sci. Soc. Am. J. 56:1521-1527.<br />
Norman, R. J., R. S. Helms, <strong>and</strong> B, R. Wells. 1992b. Influence o f delaying flood <strong>and</strong><br />
preflood nitrogen application on dry-seeded rice. Fert. Res. 32:55-59.<br />
Norman, R, 7 , D, C. Wolf, B. R, Wells, R. S. Helms, <strong>and</strong> N. A. Slaton. 1993. Influence<br />
o f application time <strong>and</strong> soil moisture condition on yield <strong>and</strong> recovery o f fertilizer<br />
*®N in dry-seeded rice. In W. E. Sabbe (ed.), Arkansas Soil Fertility Studies, 1992.<br />
Univ. Ark. Agrie, Exp. Stn. Res. Ser. 425, pp. 7-10.<br />
Norman, R. J., B. R. Wells, R. S. Helms, C. E. W ilson, Jr., N. A. Slaton, <strong>and</strong> C. A.<br />
Beyrouty. 1994a. Influence o f split applying the preflood nitrogen fertilizer on<br />
rice growth <strong>and</strong> accumulation <strong>and</strong> partitioning o f nitrogen by the rice plant. In<br />
B. R. Wells (ed.), Arkansas <strong>Rice</strong> Research Studies, 1993. Univ. Ark. Agrie. Exp. Stn.<br />
Res. Ser. 439, pp. 138-145.
406 Production<br />
i I'<br />
Norman, R. J., B. R. Wells, C. E. W ilson, Jr., R. S. Helms, N. A. Slaton, K. A. K.<br />
Moldenhauer, <strong>and</strong> K. A. Gravois. 1994b. Grain yield response of Adair’, ‘BengaE,<br />
‘Cypress’, XaGrue’, <strong>and</strong> several experimental rice lines to nitrogen fertilization.<br />
In B. R. Wells (ed.), Arkansas <strong>Rice</strong> Research Studies, 1993. Univ. Ark. Agrie. Exp.<br />
Stn. Res. Ser. 439, pp. 129-137.<br />
Norman, R. J., C. E. Wilson, Jr., P. IC. Bollich, K. A. Gravois, <strong>and</strong> B. R. Wells. 1996.<br />
Nitrogen uptake o f selected rice cultivars, Proc. 26th <strong>Rice</strong> Tech. Work. Group<br />
1996:173.<br />
Norman, R, J., P. K. BoUich, C. E. W ilson, Jr., <strong>and</strong> N. A. Slaton. 1998. Influence of<br />
nitrogen fertilizer rate, application timing <strong>and</strong> tillage on grain yields o f waterseeded<br />
rice. In R. J. Norman <strong>and</strong> T. H. Johnston (eds.), B. R, Wells <strong>Rice</strong> Research<br />
Studies, 1997. Univ. Ark. Agrie. Exp. Stn. Res. Ser, 460, pp. 299-302.<br />
Norman, R. J., C. E. Wilson, Jr., N. A. Slaton, K, A. K. Moldenhauer, <strong>and</strong> A. D. Cox.<br />
1999. Grain yield response of new rice cultivars to nitrogen fertilization. In R. J.<br />
Norman <strong>and</strong> T. H. Johnston (eds.), B. R, Wells <strong>Rice</strong> Research Studies, 1998. Univ.<br />
Ark. Agrie. Exp. Stn. Res. Ser. 468, pp. 257-267.<br />
Norman, R./ J., C. E. Wilson, Jr., K. A. K. Moldenhauer, P. K. Bollich, N. A. Slaton,<br />
S. Ntamatungiro, <strong>and</strong> C. A. BeyimUy. 2000. Influence o f nitrogen rate <strong>and</strong> timing<br />
on rice grain <strong>and</strong> milling yields. Proc. 28th <strong>Rice</strong> Tech. Work. Group. 2000:114.<br />
Ntamatungiro, S., R. J. Norman, R. W. McNew, <strong>and</strong> B, R. Wells. 1999. Comparison<br />
of plant measurements for estimating nitrogen accumulation <strong>and</strong> grain yield by<br />
flooded rice. Soil Set. Soc. Am. J. 91:676-685.<br />
Olsen, S. R., <strong>and</strong> R E. Khasawneh. 1980. Use <strong>and</strong> limitations o f physical-chemical<br />
criteria for assessing the status o f phosphorus in soils. In K E. Khasawneh et al.<br />
(eds.). The Role of Phosphorus in Agriculture. ASA-CSSA-SSSA, Madison, W I,<br />
pp. 361-410.<br />
Patrick, W. H., Jr. 1982. Nitrogen transformations in submerged soils. In F. J. Stevenson<br />
(ed.), Nitrogen in Agriculture Soils. ASA-CSSA-SSSA, Madison, W I, pp. 4 4 9 -<br />
466.<br />
Patrick, W. H., Jr., <strong>and</strong> I. C. Mahapatra. 1968. Transformation <strong>and</strong> availability to rice<br />
o f nitrogen <strong>and</strong> phosphorus in waterlogged soils. Adv. Agron. 20:323-359.<br />
Patrick, W. H., Jr., <strong>and</strong> K. R. Reddy. 1976a. Fate o f fertilizer nitrogen in flooded rice<br />
soü. Soil Sci. Soc. Am. J. 40:678-681.<br />
Patrick, W. H., Jr., <strong>and</strong> K. R. Reddy. 1976b. N itrification-denitrification reactions in<br />
flooded soils, <strong>and</strong> water bottom s: dependence on oxygen supply <strong>and</strong> ammonium<br />
diffusion. J. Environ. Qual. 5:469-472.<br />
Patrick, W. H., D. S. MUdcelsen, <strong>and</strong> B. R. Wells. 1985. Plant nutrient behavior in<br />
flooded soils. In O. P. Engelstad (ed.), Fertilizer Technology <strong>and</strong> Use, 3rd ed. Soil<br />
Science Society o f America, Madison W I, pp. 197-228.<br />
Place, G. A., 1969. Relationship of Iron, Manganese, <strong>and</strong> Bicarbonate to Chlorosis of <strong>Rice</strong><br />
Grown on Calcareous Soil Univ. Ark. Agrie. Exp. Stn. Rep. Ser. 175.<br />
Place, G. A., M. A. Siddique, <strong>and</strong> B. R. Wells. 1971a. Effects o f temperature <strong>and</strong><br />
flooding on rice growing in a saline <strong>and</strong> alkaline soil. Agron J. 63:62-66.<br />
Place, G. A., B. R. Wells, J. L. Sims, <strong>and</strong> V. L. Hall. 1971b. Phosphorus Fertilization of<br />
<strong>Rice</strong> on the Gr<strong>and</strong> Prairie of Arkansas. Univ. Ark. Agrie. Exp. Stn. Bull. 762.<br />
Ponnamperuma, E N. 1972. The chemistry o f submerged soils. Adv. Agron. 2 4 :4 5 2 -<br />
464.<br />
Pulley, H. J., C. A. Beyrouty, E. E. Gbur, <strong>and</strong> R. J. Norman. 1999. Factors influencing
Soil Fertilization <strong>and</strong> Mineral Nutrition in U.S. Mechanized <strong>Rice</strong> Culture 407<br />
potassium uptalce by rice. In R. J. Norman <strong>and</strong> T. H. Johnston (eds.), B. R. Wells<br />
<strong>Rice</strong> Research Studies, 1998. Univ. Ark. Agric. Exp. Stn. Res. Ser. 468, pp. 4 5 8 -<br />
462.<br />
Rashid, A., <strong>and</strong> R. L. Fox. 1992. Evaluating internal zinc requirements o f grain crops<br />
by seed analysis. Agron. J. 84:46-474.<br />
Reddy, K. R., <strong>and</strong> W. H. Patrick, Jr. 1977. Effect o f placement <strong>and</strong> concentration o f<br />
applied ^^NH4 -N on nitrogen loss from flooded soil. Soil Sei. 123:142-147.<br />
Reddy, K. R., W. H. Patrick, Jr., <strong>and</strong> R. E. Phillips. 1976. Am m onium diffusion as a<br />
factor in nitrogen loss from flooded soils. Soil Sei. Soc. Am. J. 40:528-533.<br />
Reeve, R. C., <strong>and</strong> M. Fireman. 1967. Salt problems in relation to irrigation. In R. M .<br />
Hagan et al. (eds.), Irrigation o f Agricultural L<strong>and</strong>s. Agron. Monogr. 11. American<br />
Society o f Agronomy, Madison, W I, pp. 988-1008.<br />
Reuter, D. J., <strong>and</strong> J. B. Robinson. 1986. Temperate <strong>and</strong> sub-tropical crops. In D. J.<br />
Reuter <strong>and</strong> J. B. Robinson (eds.), Plant Analysis: An Interpretation Manual. Inkata<br />
Press, M elbourne, Australia, pp. 38-99.<br />
Rhoades, J. D. 1996. Salinity: electrical conductivity <strong>and</strong> total dissolved solids. In D. L.<br />
Sparks et al. (eds.). Methods of Soil Analysis, P t 3, Chemical Methods. SSSA Book<br />
Ser. 5. ASA-SSSA, Madison, W I, pp. 417-436.<br />
Rhoades, J. D., <strong>and</strong> J. Loveday. 1990. Salinity in irrigated agriculture. In B. A. Stewart<br />
<strong>and</strong> D. R, Nielsen (eds.), Irrigation of Agricultural Crops. Monogr, 30. A SA -C SSA -<br />
SSSA, Madison, W I, pp. 1089-1142.<br />
<strong>Rice</strong>, C. W , <strong>and</strong> M. S. <strong>Smith</strong>. 1984. Short term immobilization o f fertilizer nitrogen<br />
at the surface o f no-till <strong>and</strong> plowed soils. Soil Sd. Soc. Am. /. 48:295-297.<br />
Roberts, S. R., J. E. HiU, D. M . Br<strong>and</strong>on, B. C. Miller, S. C. Scardaci, C. M. W ick, <strong>and</strong><br />
J. F. Williams. 1993. Biological yield <strong>and</strong> harvest index in rice: Nitrogen response<br />
o f tail <strong>and</strong> semidwarf cultivars. J. Prod. Agric. 6:585-588.<br />
Sah, R. N., <strong>and</strong> D. S. Mikkelsen. 1986. Transformation o f inorganic phosphorus during<br />
the flooding <strong>and</strong> draining cycles o f soil. Soil Sei. Soc. Am. J. 50:62-67.<br />
Sajwan, K. S., <strong>and</strong> W. L. Lindsey. 1986. Effects o f redox on zinc deficiency in paddy<br />
rice. Soil Sei. Soc. Am. J. 50:1264-1269.<br />
Savant, N. K., G, H. Synder, <strong>and</strong> L. E. Datnoff. 1997. Silicon management <strong>and</strong> sustainable<br />
rice <strong>production</strong>. Adv. Agron. 58:151-195.<br />
Scardaci, S. C., A. U. Eke, J. E. Hill, M. C. Shannon, <strong>and</strong> J. D. Rhoades. 1999. Water<br />
<strong>and</strong> soil salinity studies on California rice, http//agronomy.ucdavis.edu/uccerice/<br />
WATER/salinity.htm.<br />
Sedberry, J. E., Jr., P. G. Schilling, F. E. Wilson, <strong>and</strong> F. J. Peterson. 1978. Diagnosis <strong>and</strong><br />
Correction of Zinc Problems in <strong>Rice</strong> Production. La. State Univ, Agric, Exp. Stn.<br />
Bull. 708.<br />
Sedberry, J. E., Jr., F J. Peterson, E E. W ilson, D. B. Mengel, P. E. Schilling, <strong>and</strong> R. H.<br />
Brupbacher. 1980, Influence o f soil reaction <strong>and</strong> applications o f zinc on yields<br />
<strong>and</strong> zinc contents o f rice plants. Commun. SoUSd. Plant Anal. 11(3);283~295.<br />
Sedberry, J. E., Jr., M. C, Amacher, D. P. Bligh, <strong>and</strong> O. D. Curtis. 1987. Plant-Tissue<br />
Analysis as a Diagnostic Aid in Crop Production. La. State Univ. Agric, Exp. Stn.<br />
Bull, 783.<br />
Shah<strong>and</strong>eh, H., L. R. Hossner, <strong>and</strong> F. T. Turner. 1994, Phosphorus relationships in<br />
flooded rice soils with low extractable phosphorus. Soil Sd. Soc. Am. J. 58:1 1 8 4 -<br />
1189.<br />
Shah<strong>and</strong>eh, H., L. R. Hossner, <strong>and</strong> F. T, Turner. 1995. Evaluation o f soil phosphorus
408 Production<br />
K í :- i!<br />
■I! ;<br />
tests for flooded rice soils under oxidized <strong>and</strong> reduced soil conditions. Cotnmun.<br />
Soil Sci. Plant Anal 26:107-121.<br />
Sims, J. L,, <strong>and</strong> G. A. Place. 1968. Growth <strong>and</strong> nutrient uptake o f rice at different<br />
growth stages <strong>and</strong> nutrient levels. Agron.}. 60:692-696.<br />
Sistani, K. R., N. K. Savant, <strong>and</strong> K. C. Reddy. 1997. Effect o f rice hull ash silicon on<br />
rice seedling growth. /. Plant Nutr. 200(1): 195-201.<br />
Slaton, N. A. 1998. The influence o f elemental sulfur amendments on soil chemical<br />
properties <strong>and</strong> rice growth. Ph.D. dissertation. University o f Arkansas, Fayetteville.<br />
AR (diss. abstr. AA T-983-9310).<br />
Slaton, N. A., R. D. Cartwright, <strong>and</strong> C. E. W ilson, Jr. 1995. Potassium deficiency <strong>and</strong><br />
plant diseases observed in rice fields. Better Crops 79(4 ):1 2 -1 4 .<br />
Slaton, N. A., B. R. Wells, D. M. Miller, C. E. Wilson, Jr., <strong>and</strong> R. J. Norman. 1996.<br />
Definition o f rice <strong>production</strong> problems related to soil alkalinity <strong>and</strong> salinity. In<br />
R. J. Norman <strong>and</strong> B. R. Wells (eds.), Arkansas <strong>Rice</strong> Research Studies, 1995. Univ.<br />
Ark. Agrie. Exp. Stn. Res. Ser. 453, pp. 178-185.<br />
Slaton, N. A., S, Ntamatungiro, C, E. Wilson, Jr., R. J. Norman, <strong>and</strong> D, L. Boothe.<br />
2000..'Effects o f previous crop <strong>and</strong> phosphorus fertilization rate on rice. In R. J.<br />
Norman <strong>and</strong> C. A. Beyrouty (eds.), B. R. Wells <strong>Rice</strong> Research Studies, 1999. Univ.<br />
Ark. Agrie. Exp. Stn. Res. Ser. 476, pp. 294-303.<br />
Slaton, N. A., R. J. Norman, <strong>and</strong> J. T. GÜmour. 2001a. Oxidation rates o f commercial<br />
elemental sulfur products applied to an alkaline silt loam soil from Arkansas. Soil<br />
Sci. Soc. Am. J. 65:239-243.<br />
Slaton, N. A., C. E. Wilson, Jr., S. Ntamatungiro, R. J. Norman, <strong>and</strong> D. L. Boothe.<br />
2001b. Evaluation o f Zn seed treatments for rice. Agron.}. 93:152-157.<br />
Snyder, G. H. 1993. Soils <strong>and</strong> Fertilization for Florida <strong>Rice</strong> Production. Univ, Fla, Coop.<br />
Ext. Ser. Fact Sheet AGR-61.<br />
Snyder, G. H., <strong>and</strong> C. L. Elliott. 1994. Fe soil tests for predicting rice seedling chlorosis<br />
on Everglades Histosols, Proc. 25th <strong>Rice</strong> Tech. Work. Group 1994:150.<br />
Snyder, G. H., <strong>and</strong> D. B, Jones. 1988. Prediction <strong>and</strong> prevention o f iron-related rice<br />
seedling chlorosis on Everglades Histosols. Soil Sci. Soc. Am.}. 52:1043-1046.<br />
Snyder, G. H., <strong>and</strong> D. B. Jones. 1991. Post-emergence treatment o f iron-related riceseedling<br />
chlorosis. Plant Soil 138:313-317.<br />
Snyder, G. H„ D. B. Jones, <strong>and</strong> G. J. Gascho. 1986. Silicon fertilization o f rice on<br />
Everglades Histosols. Soil Sci. Soc. Am.}. 50:1259-1263.<br />
Snyder, G. H., D. B. Jones, <strong>and</strong> F. J. Coale, 1990. Occurrence <strong>and</strong> correction o f manganese<br />
deficiency in Histosol-grown rice. Soil Sci. Soc. Am. /. 54:1634-1638.<br />
Stansel, J. W. 1975. The rice plant: its development <strong>and</strong> yield, pp. 9 -2 1 . Six Decades of<br />
<strong>Rice</strong> Research in Texas. Tex. A&M Univ. Agrie. Exp. Stn. Res. Monogr. 4.<br />
Stutte, C. A., <strong>and</strong> P, R. F. da Silva. 1981. Nitrogen volatilization from rice leaves. I.<br />
Effect o f genotype <strong>and</strong> air temperature. Crop. Sci 21:596-600.<br />
Szabolcs, D. L. 1985. Salt affected soils as a world problem. The Reclamation of Salt-<br />
Affected Soils. Proceedings of the International Symposium Jinan, China. Beijing<br />
j^gricultural University, Beijing, pp. 30-47.<br />
Teo, Y, H., C. A. Beyrouty, <strong>and</strong> E. E. Gbur. 1992. Nitrogen, phosphorus, <strong>and</strong> potassium<br />
influx kinetic parameters o f three rice cultivars. ]. Plant Nutr. 15(4):435-444.<br />
Teo, Y. H., C. A. Beyrouty, R. J. Norman, <strong>and</strong> E. E. Gbur. 1994, Nutrient supplying<br />
capacity of a paddy rice soil. J. Plant Nutr. 17(11): 1983-2000.
Soil Fertilization <strong>and</strong> Mineral Nutrition in U.S. Mechanized Rite Culture 409<br />
Teo, Y. H,, C. A. Beyrouty, <strong>and</strong> E. E, Gbur. 1995a. Eyaluation o f a model to predict<br />
nutrient uptake by field-grown rice. Agron. J. 87:7-12.<br />
Teo, Y. H., C. A. Beyrouty, <strong>and</strong> E. E. Gbur. 1995b. Relating soü test P to P uptake by<br />
paddy rice. Soil Sei 159:409-414.<br />
Teo, Y. H., C. A. Beyrouty, R. J. Norman, <strong>and</strong> E. E. Gbur. 1995c. Nutrient uptake<br />
relationship to root characteristics o f rice. Plant Soil 171:297-302.<br />
Tisdale, S. L., W. L. Nelson, J. D. Beaton, <strong>and</strong> J. L. Havlin. 1993. Soil FerßUty <strong>and</strong><br />
Fertilizers. Macmillan, New York.<br />
Trostle, C. L., F. T. Turner, M . F. Jund, <strong>and</strong> K. M einnes. 1998. Soil amm onium diffusion<br />
constraints may explain large differences in N supply to Texas rice. Proc.<br />
27th <strong>Rice</strong> Tech. Work. Group 1998:188-189.<br />
Turner, F. X , <strong>and</strong> J. W. Gilliam. 1976a. Effect o f moisture <strong>and</strong> oxidation status o f<br />
alkaline rice soils on the absorption o f soil phosphorus by an anion resin. Plant<br />
Soil 45:353-363.<br />
Turner, F. X , <strong>and</strong> J. W. Gilliam. 1976b. Increased P diffusion as an explanation o f<br />
increased P availability in flooded rice soils. Plant Soil 45:365-377.<br />
Turner, E X , <strong>and</strong> M . F. Jund. 1991. Chlorophyll m eter to predict nitrogen topdress<br />
requirement for semidwarf rice. Agron. J. 83:926-928.<br />
Turner, F. X , <strong>and</strong> M. F. Jund. 1994. Assessing the nitrogen requirements o f rice crops<br />
with a chlorophyll meter. Aust. /. Exp. Agrie. 34:1001-1005.<br />
Turner, F. X , K. W. Brown, <strong>and</strong> L. E. Deuel. 1980, Nutrients <strong>and</strong> associated ion concentrations<br />
in irrigation return flow from flooded rice fields. /. Environ. Qual<br />
9:256-260.<br />
U.S. Salinity Laboratory Staff. 1954. Diagnosis <strong>and</strong> Improvement of Saline <strong>and</strong> Alkali<br />
Soils. H<strong>and</strong>book 60. U.S. Government Printing Office, Washington, DC.<br />
Vories, E, D., <strong>and</strong> P. A. Counce. 1992. A com parison o f furrow irrigated <strong>and</strong> flooded<br />
rice. In B. R Wells (ed.), Arkansas <strong>Rice</strong> Research Studies, 1991. Univ. Ark. Agrie.<br />
Exp. Stn. Res. Ser. 422, pp. 130-133.<br />
Wagenet, R. J. 1984. Salt <strong>and</strong> water movement in the soil profile. In I. Shainberg<br />
<strong>and</strong> J. Shalhevet (eds.), Soil Salinity under Irrigation: Processes <strong>and</strong> Management.<br />
Springer-Verlag, Berlin, pp. 100-114.<br />
Wells, B. R. 1980. Zinc Nutrition of <strong>Rice</strong> Growing on Arkansas Soils. Univ. Ark. Agrie.<br />
Exp, Stn. Res. Bull. 848,<br />
Wells, B, R., <strong>and</strong> W. F. Faw. 1978. Short-statured rice response to seeding <strong>and</strong> N rate.<br />
Agron. J. 70:477-480<br />
Wells, B. R., <strong>and</strong> R. J. Norman. 1993. Response o f rice to polyolefin-coated ureas as<br />
nitrogen sources. In B. R Wells (ed.), Arkansas <strong>Rice</strong> Research Studies, 1992. Univ.<br />
Ark. Agrie. Exp. Stn. Res. Ser. 425, pp, 22-2 4 .<br />
Wells, B. R., <strong>and</strong> P. A. Shockley. 1974. Conventional <strong>and</strong> controUed-release nitrogen<br />
sources for rice. Soil Sei. Soc. Am. J. 39:549-551.<br />
Wells, B. R., <strong>and</strong> F. X Turner. 1984. Nitrogen use in flooded rice. In R. D. Hauck (ed.),<br />
Nitrogen in Crop Production. ASA-CSSA-SSSA, Madison, W I, pp. 349-362.<br />
Wells, B. R., L Thom pson, G. A, Place, <strong>and</strong> P. A. Shockley. 1973. Effect of Zinc on<br />
Chlorosis <strong>and</strong> Yield of <strong>Rice</strong> Grown on Alkaline Soil. Univ. Ark. Agi'ic. Exp. Stn.<br />
Rep. Ser. 208.<br />
Wells, B. R., P. K. Bollich, P. K. W. Ebelhar, D. S. Mildcelson, R. J. Norman, D. M.<br />
Br<strong>and</strong>on, R. S. Hehns, F. X Turner, <strong>and</strong> M . P. Westcott. 1989. Dicy<strong>and</strong>iamide
1<br />
410 Production<br />
(DCD) as a nitrification inhibitor in rice culture in the United States. Comtnun.<br />
Soil Sei Plant Anal 20:2023-2047.<br />
Wells, B. R., D. Kamputa, R. J. Norman, E. D. Vories, <strong>and</strong> R. Baser. 1991. Fluid fertilizer<br />
management o f furrow irrigated rice. /. Pert. Issues 8:14-19. ’<br />
Wells, B. R,, R. f. Norman, <strong>and</strong> R. S. Helms. 1992. Use o f plant area measurements<br />
to estimate mid-season nitrogen rate for rice. pp. 89-94. In B. R Wells (ed.),<br />
Arkansas <strong>Rice</strong> Research Studies, 1991. Univ. Ai'k. Agrie. Exp. Stn. Res. Ser. 422.<br />
Wells, B, R,, B. A. Huey, R. J. Norman, <strong>and</strong> R. S. Helms. 1993. <strong>Rice</strong>. In W. F. Bennett<br />
(ed.). Nutrient Deficiencies <strong>and</strong> Toxicities in Crop Plants. APS Press, St. Paul, MN,<br />
pp. 15-19.<br />
Wescott, M. R, <strong>and</strong> D. S Mikkelsen, 1985. Comparative effects o f an organic <strong>and</strong><br />
inorganic nitrogen source in flooded soil. Soil Scl Soc. Am. J. 49:1470-1475.<br />
Wescott, M. R, <strong>and</strong> K. W. Vines. 1986. A com parison o f sprinker <strong>and</strong> flood irrigated<br />
rice. Agron. J. 78:637-640.<br />
Wescott, M. R, D. M. Br<strong>and</strong>on, C. W. Lindau, <strong>and</strong> W. H. Patrick. 1986. Effects o f<br />
seeding method <strong>and</strong> tim e o f fertilization on urea-nitrogen-15 recovery by rice.<br />
Agron. J. 78:474-478.<br />
Westfall, D. G., W. B. Anderson, <strong>and</strong> R. J. Hodges. 1971. Iron <strong>and</strong> zinc response of<br />
chlorotic rice grown on calcareous soils. Agron. J. 63:702-705.<br />
Wilson, C. E., Jr., R, J. Norman, <strong>and</strong> B. R. Wells. 1989. Seasonal uptake patterns<br />
of fertilizer nitrogen applied in split applications to rice. Soil Sei. Soc. Am. J.<br />
53:1884-1887.<br />
Wilson, C. E., Jr., B. R. Wells, <strong>and</strong> R. J. Norman. 1994. Fertilizer nitrogen uptake by<br />
rice from urea-am m onium nitrate solution vs. granular urea. Soil Sei Soc. Am.<br />
7.58:1825-1828.<br />
Wilson, C. E., Jr., N. A. Slaton, R. J. Norman, B. R. Wells, <strong>and</strong> P. A. Dickson. 1995a.<br />
Phosphorus <strong>and</strong> potassium fertilization improves rice growth <strong>and</strong> yield. Better<br />
Crops 7 9(3):13-15.<br />
Wilson, C. E., Jr., D. B, Stephens, C. A. Beyrouty, <strong>and</strong> D, M. Miller. 1995b. Salinity<br />
effects on soil chemistry, potassium uptake, <strong>and</strong> rice <strong>production</strong>. In B. R. Wells<br />
(ed.), Arkansas <strong>Rice</strong> Research Studies, 1994. Univ. Ark. Agrie. Exp. Stn. Res. Ser.<br />
446, pp. 156-163.<br />
Wilson, C. E., Jr., R. J, Norman, N. A. Slaton, <strong>and</strong> R. S. Helms. 1996, Nitrogen management<br />
for two tillage systems in rice. In R. J. Norman <strong>and</strong> B. R Wells (eds.),<br />
Arkansas <strong>Rice</strong> Research Studies, 1995. Univ. Ark. Agrie. Exp. Stn. Res. Ser. 453,<br />
pp. 275-280.<br />
Wilson, C. E., Jr., N. A. Slaton, S. Ntamatungiro, R. J. Norman, D. L. Frizzell, <strong>and</strong><br />
B. R, Wells. 1997. Phosphorus fertilizer management on alkaline soils. In R. J.<br />
Norman <strong>and</strong> T. H. Johnston (eds.), B. R. Wells <strong>Rice</strong> Research Studies, 1996. Univ.<br />
Ark. Agrie. Exp. Stn. Res. Ser. 456, pp. 142-146.<br />
Wilson, C. E., Jr., P. K. Bollich, <strong>and</strong> R. J. Norman. 1998. Nitrogen application timing<br />
effects on nitrogen efficiency o f dry-seeded rice. Soil Sei Soc. Am. J. 6 2 :9 5 9 -<br />
964.<br />
Wilson, C. E., Jr., N. A. Slaton, S. Ntamatungiro, <strong>and</strong> R. J. Norman. 1999. Phosphorus<br />
fertilizer management for rice produced on alkaline soils. In R, J. Norman <strong>and</strong><br />
T. H. Johnston (eds.), B. R. Wells <strong>Rice</strong> Research Studies, 1998. Univ. Ark. Agrie.<br />
Exp. Stn. Res. Ser. 468, pp. 310-316.
Soil Fertilization <strong>and</strong> Mineral Nutrition in U.S. Mechanized Rite Culture 411<br />
W ilson, C. E., Jr., T. C. Keisling, D. M . Miller, C. R. Dillon, A. D. Pearce, D. L. Erizzell,<br />
<strong>and</strong> P. A. Counce. 2000a. Tillage influence on salt movement in silt loam soils<br />
cropped to paddy rice. Soil Sei Soc. Am. J. 64;1771-1776.<br />
W ilson, C. E., N. A. Slaton, R. J. Norman, <strong>and</strong> D. M. Miller. 2001. Efficient use o f<br />
fertilizer. In N. A. Slaton (ed.)> <strong>Rice</strong> Production H<strong>and</strong>book. Univ. Ark. Coop. Ext.<br />
Serv. Publ. M P-192, pp. 51-74.<br />
Wilson, C. E., Jr., H. D, Scott, R. J. Norman, N. A. Slaton, <strong>and</strong> D. L. Erizzell. 2000b.<br />
Summary characterization <strong>and</strong> spatial distribution o f irrigation water quality<br />
parameters in Desha County Arkansas, pp. 7 -1 2 . K. F. Steele (ed.). Proceedings<br />
of the Arkansas Water Resources Center Conference^ 2000, Publication No. M SC-<br />
284.<br />
Yoon, S. K., J. T. Gilmour, <strong>and</strong> B, R. Wells. 1975. M icronutrient levels in the rice plant<br />
Y leaf as a function o f soil solution concentration. Soil Sei Soc. Am. J. 39:685-688.<br />
Yoshida, S. 19S1, Fundamentals o f <strong>Rice</strong> Crop Science. International <strong>Rice</strong> Research In <br />
stitute, M anila, The Philippines.
Chapter<br />
3 S<br />
<strong>Rice</strong> Diseases<br />
Don Groth<br />
<strong>Rice</strong> Reseorch Station<br />
LSU Ag Center<br />
Crowley, Louisiana<br />
Fleet Lee<br />
<strong>Rice</strong> Reseorch <strong>and</strong> Extension Center<br />
University of Arkansas<br />
Stuttgart, Arkansas<br />
EFFECTS OF RICE DISEASES ON YIELD AND QUALITY OF RICE<br />
DIAGNOSES, BIOLOGY, ECOLOGY, AND CONTROL OF RICE DISEASES<br />
Seed <strong>and</strong> Seedling Diseases<br />
Water Mold<br />
Minor Seed <strong>and</strong> Seedling Diseases<br />
Seedling Blight<br />
Root <strong>and</strong> Crown Diseases<br />
Root Rot<br />
Minor Root <strong>and</strong> Crown Diseases<br />
Bokonoe (or Foot Rot)<br />
Crown Rot<br />
Root Knot<br />
Stem <strong>and</strong> Culm Diseases<br />
Sheath Blight<br />
Stem Rot<br />
Crown Sheoth Rot ’<br />
Minor Stem Diseases<br />
Aggregate Sheath Spot<br />
Sheath Rot<br />
Sheath Spot<br />
Foliar Diseases<br />
Blast<br />
Brown Spot<br />
Narrow Brown Leaf Spot<br />
Minor Folior Diseases<br />
Alternaría Leaf Spot<br />
Bacterial Blight<br />
R ice: O rigin, H istory, Teclinology, <strong>and</strong> P rod uction, edited by C . W ayne Sm ith<br />
IS B N 0 -4 7 1 -3 4 5 1 6 -4 © 2 0 0 3 Jo h n W iley & Son s, In c.<br />
413
414 Production<br />
Bacterial Streak<br />
Eyespot<br />
Leaf Scald<br />
Leaf Smut<br />
White Tip Nematode<br />
White Leaf Streak<br />
Head <strong>and</strong> Grain Diseases<br />
Pecky <strong>Rice</strong><br />
False Smut<br />
Kernel Smut<br />
Panicle Blight<br />
Minor Head <strong>and</strong> Grain Diseases<br />
Black Kernel<br />
Downy Mildew<br />
Grain Discoloration<br />
Viral <strong>and</strong> Mycoplasma-iike Diseases<br />
Nematpdes<br />
Bacterial Diseases<br />
Miscellaneous Diseases or Physiological Disorders<br />
Alkalinity or Salt Damage<br />
Bronzing<br />
Cold Injury<br />
Hydrogen Sulfide Toxicity<br />
Straighthead<br />
INTEGRATED DISEASE MANAGEMENT<br />
Plant Quarantine<br />
Cultural Practices<br />
Host Resistance<br />
Chemical Control<br />
Biological Control<br />
CONCLUSIONS<br />
REFERENCES<br />
EFFECTS OF RICE DISEASES ON YIELD AND QUALITY OF RICE<br />
I t :<br />
<strong>Rice</strong> diseases pose a m ajor threat to rice <strong>production</strong> (Ou, 1985; Groth et al., 1991;<br />
Webster <strong>and</strong> Gunnell, 1992). Disease severity ranges from undetected damage to the<br />
complete destruction o f a crop. Extensive systematic yield <strong>and</strong> quality loss estimates<br />
caused by rice diseases have not been developed, but losses range from a trace to total<br />
crop loss, depending on the inoculum density, pathogen aggressiveness, environmental<br />
conditions, cultivar susceptibility, <strong>and</strong> interaction with other cultural parameters<br />
(Savary et al., 2000). Loss estimates are also difficult to estimate because o f lack o f data<br />
on the numerous diseases affecting rice, hidden underground damage associated with<br />
root diseases, <strong>and</strong> little qualitative inform ation on distribution <strong>and</strong> severity in com <br />
mercial fields. There is no doubt that rice diseases cause significant econom ic yield<br />
<strong>and</strong> quality reductions <strong>and</strong> cost farmers millions o f dollars eacli year from reduced
<strong>Rice</strong> Diseases 415<br />
productivity <strong>and</strong> costs o f control. Damage that can occur includes thin st<strong>and</strong>s, poor<br />
plant vigor, poor nutrient utilization, reduced yield, reduced quality, plant death,<br />
lodging, <strong>and</strong> harvest problems. Specific damages that can occur include necrosis o f<br />
tissues, chlorosis, wilting, <strong>and</strong> deformation o f plant parts. <strong>Rice</strong> diseases are caused<br />
by the interaction between a susceptible plant, a virulent pathogen, <strong>and</strong> a favorable<br />
environm ent Underst<strong>and</strong>ing this relationship allows the development <strong>and</strong> selection<br />
o f the best management program, which must be adjusted to current environmental<br />
conditions. Each disease has its own cycle, <strong>and</strong> control practices are effective only at<br />
certain stages when the pathogen is susceptible <strong>and</strong> before irrevocable damage occurs.<br />
Although <strong>production</strong> has not been eliminated from any areas because o f rice<br />
diseases, there have been shifts in hectarage from one area to another. An excellent<br />
example o f this was the shift of m ost o f the medium-grain rice from Louisiana to<br />
Arkansas because o f severe blast development on the cultivar Bengal in Louisiana<br />
that does not occur in the apparently less favorable environment o f Arkansas (D. E.<br />
Groth, personal com m unication). Seed <strong>and</strong> seedling diseases often cause poor st<strong>and</strong>s,<br />
<strong>and</strong> at times, replant situations. Toxins have not been a m ajor problem with rice grain<br />
quality, but fungal toxins have been detected in some rice grain.<br />
Diseases occur in all rice-growing regions o f the world. In die United States,<br />
disease pressure is higher in the midsouth growing region than in the arid California<br />
<strong>production</strong> area, although California has had significantly m ore disease pressure<br />
recently with the introduction o f blast in 1997 (Greer <strong>and</strong> Webster, 2000) <strong>and</strong> the<br />
introduction o f bakanae in 1999 (Boyd, 2000). The United States is fortunate that it<br />
does not have any o f the devastating viral diseases that occur in m ost other <strong>production</strong><br />
areas o f the world. Also, the United States has a limited number o f nematode <strong>and</strong><br />
bacterial diseases compared with m ost o f the world <strong>production</strong> areas. Unfortunately,<br />
there are enough fungal diseases that increase <strong>production</strong> costs <strong>and</strong> reduce yields <strong>and</strong><br />
quality to lim it the econom ic return that U.S. farmers receive for their crop.<br />
Coverage in this chapter o f the fungal diseases is thorough, but only the m ost<br />
im portant bacterial <strong>and</strong> nematode diseases are discussed. Several good review articles<br />
have been published recently on tliese pathogen groups (Hibino, 1996; Abo <strong>and</strong> Sy,<br />
1998; McGawley <strong>and</strong> Overstreet, 1998). Also, because o f the limited scope o f this<br />
chapter <strong>and</strong> specific regional characteristics o f rice diseases, the reader is encouraged<br />
to obtain additional inform ation from his or her local Extension Service. Several<br />
excellent publications are available that cover many o f these diseases in more detail.<br />
These include the Compendium o f <strong>Rice</strong> Diseases (Webster <strong>and</strong> Gunnell, 1992), <strong>Rice</strong><br />
Diseases (Ou, 1985), A Manual of <strong>Rice</strong> Seed Health Testing (Mew <strong>and</strong> Misra, 1994),<br />
<strong>and</strong> other regional publications (e.g., Groth et al., 1993; Cartwright <strong>and</strong> Lee, 2001).<br />
A number o f Web pages <strong>and</strong> newsletters have also been developed by various rice<br />
organizations that have current recommendations, color photographs, <strong>and</strong> up-to-<br />
date disease statuses.<br />
'!■ iil'<br />
DIAGNOSES, BIOLOGY, ECOLOGY, AND CONTROL OF RICE DISEASES<br />
I !■!<br />
Seed <strong>and</strong> Seedling Diseases<br />
Water Mold. Numerous fungi, including Achlya conspicua Coker, A. klehsiana Pieters,<br />
Pythium spinosum Sawada, P. dissotocum Drechs, Pusarium spp., <strong>and</strong> Pythium spp,
416 Production<br />
yi!:i<br />
ini<br />
. •-»<br />
cause water molds or seedling damping off. The disease is found everywhere that<br />
rice is grown. During seed germination <strong>and</strong> early growth, rice is very susceptible to<br />
these pathogens, which can kill or severely damage the young plant. Water molds<br />
are most severe in water-seeded systems or under wet environmental conditions<br />
in a drill-seeded or dry broadcast planting system under cool conditions (below<br />
13°C). Seedlings becom e resistant to these pathogens once the seedling develops its<br />
first true leaf or when the leaf grows above the water (Chun <strong>and</strong> Schneider, 1998).<br />
These pathogens are often tlie same group o f fungi that cause root rots. Som e o f the<br />
pathogens attack the embryo <strong>and</strong> young plant, while others use the carbohydrate in<br />
the endosperm. Both scenarios are identified by an area o f discoloration around the<br />
seed that is the fungal mycelium extending into the soil (Figure 3.5.1; see color insert).<br />
These signs are most noticeable when the water is removed <strong>and</strong> the soil starts to dry.<br />
Symptoms include yellow seedlings, dead <strong>and</strong> dying seedlings, <strong>and</strong> thin st<strong>and</strong>s. The<br />
pathogens that cause water molds are soUborne. Excessive soil organic matter allows<br />
the proliferation of the pathogen <strong>and</strong> an increase in disease incidence.<br />
Yield losses are not com m on because the rice plant has the ability to compensate<br />
for thin stapds by tillering if managed correctly. Although replanting is rare except in<br />
very early planted rice, several surveys have been conducted recently which indicate<br />
that significant st<strong>and</strong> losses do occur (Groth <strong>and</strong> HoUier, 1986). Losses have been<br />
reported as high as 100% , <strong>and</strong> replanting is required. Since less than 50% o f the seeds<br />
planted in a field produce viable plants, producers plant excessive rates to ensure an<br />
adequate st<strong>and</strong>. However, with the advent o f expensive hybrid seed <strong>and</strong> herbicideresistant<br />
cultivars, with their economically necessary lower seeding rates, seed <strong>and</strong><br />
seedling disease control will be even more important. Optimum st<strong>and</strong>s range from<br />
100 to 200 plants/m^ (Anonymous, 1999). St<strong>and</strong>s in the range o f 50 to 100 plants can<br />
be tolerated if the seedlings are well spaced <strong>and</strong> weeds can be controlled early. More<br />
than 200 plants are considered excessive.<br />
The best control measure is the use o f high-quality, vigorous seeds. Normally,<br />
seeds produced under good management practices (foliar fungicides, good fertility,<br />
timely harvest, <strong>and</strong> storage at the correct moisture <strong>and</strong> temperature) provide this type<br />
o f quality. Breeding for resistance to water molds usually is accomplished by selecting<br />
for seedling vigor tliat allows the rice plant to outgrow damage by these pathogens.<br />
Breeders have not developed phenotypes having high levels o f resistance to water<br />
molds <strong>and</strong> seedling diseases.<br />
Fungicide seed treatments are the main chemical control measure (Rush <strong>and</strong><br />
Schneider, 1990). Before planting, seeds are treated with various materials, including<br />
fungicides, growth regulators, insecticides, <strong>and</strong>/or zinc, to ensure a st<strong>and</strong>. Although<br />
seed treatments do not guarantee a good st<strong>and</strong>, they do increase seedling establishment<br />
<strong>and</strong> help avoid replanting under m ost conditions. Several university programs<br />
test seed treatments, <strong>and</strong> specific recommendations can be obtained from local cooperative<br />
extension services.<br />
The use of presprouted rice in a water-seeded system is also a m ajor control<br />
method that allows plants a head start against these patliogens. <strong>Rice</strong> seeds are placed<br />
in a large porous bag <strong>and</strong> immersed into water in soaking tanks. After 24 hours the<br />
seeds are removed from the water <strong>and</strong> allowed to drain for 24 hours, to remove excess<br />
water that would interfere with seed separation at planting <strong>and</strong> allow aeration to<br />
encourage sprouting or piping. At this point, the seeds are planted by airplane. These<br />
wet-sprouted seeds may be treated with a fungicide using specialized equipment.
Ríce Diseases 417<br />
<strong>Rice</strong> seed cannot be treated before soaking because some o f the fimgicide washes off<br />
the seed, causing environmental <strong>and</strong> disposal problems in the soalt <strong>and</strong> drain water.<br />
Dry-treated <strong>and</strong> untreated seed can be used in water-seeded <strong>and</strong> broadcast seeding<br />
systems, but the delay in germination with dry seed can enhance water molds <strong>and</strong><br />
allow seeds to drift, which causes uneven st<strong>and</strong>s. Gibberellic acid seed treatments also<br />
encourage seedling establishment by allowing the seedling to elongate <strong>and</strong> establish<br />
more quicldy.<br />
Soil-applied fungicides can be used to supplement seed treatments to control<br />
both seedling damping off <strong>and</strong> early feeder root necrosis. The fitngicide metalaxyl<br />
(trade name Ridomil) can be applied preplant onto the soil at the rate o f 0.28 kg active<br />
ingredient/ha. Significant st<strong>and</strong> <strong>and</strong> yield increases have been reported, but high costs<br />
<strong>and</strong> erratic results have limited commercial use (Rush <strong>and</strong> Schneider, 1990).<br />
Several cultural practices can be used to minimize seedling damage. Planting<br />
should be delayed until daytime temperatures are above 25°C (77“F) to encourage<br />
seedling development <strong>and</strong> shorten the time to seedling establishment. Planting into<br />
clear rather than muddy water usually encourages seedling establishment by avoiding<br />
silting that covers the seed <strong>and</strong> delays establishment. Planting presprouted seeds also<br />
reduces tim e to seedling establishment. Clean tillage appears to decrease seedling<br />
diseases by reducing decaying residue on which tlie pathogen can propagate.<br />
Minor Seed <strong>and</strong> Seedling Diseases<br />
Seedling Blight. Seedling blight or damping-off is a disease complex caused by several<br />
different seedborne <strong>and</strong> soilborne fungi, including Cochlioholus miyaheanus (Ito &<br />
Kuribayashi) Drechs. ex. Dastur, Curvularia spp., Fusarium spp., Rhizoctonia solani<br />
Kuhn, Sclerotium rolfsii Sacc. [Teleomorph: Athelia rolfsii (Curzi) Tu & Kimbrough],<br />
the bacterium Burkholderia glumae, <strong>and</strong> other pathogenic fungi (Webster <strong>and</strong> Gunnell,<br />
1992). Typically, rice seedlings are weakened or killed by these pathogens under<br />
cool environmental conditions.<br />
Seedling blight causes rice st<strong>and</strong>s to be irregular <strong>and</strong> thin early in the growing<br />
season. The inoculum is carried on the kernels or hulls o f seed rice or on soil particles.<br />
The pathogens enter the young seedlings <strong>and</strong> either Idll or injure them. Those that<br />
survive lack vigor <strong>and</strong> are yellowish.<br />
How widespread <strong>and</strong> severe seedling blight becomes depends chiefly on three<br />
things: (1) percent seed infected by blight fungi, (2) soil temperature, <strong>and</strong> (3) soil<br />
moisture content. Seedling blight is more severe on rice that has been planted early<br />
when the soil is cool <strong>and</strong> damp. This disadvantage o f early seeding can be partially<br />
overcome by seeding at a shallow depth <strong>and</strong> the use o f gibberellic acid seed treatment.<br />
Conditions that tend to delay the seedlings’ emergence fi*om the soil often favor<br />
seedling blight.<br />
Seeds that carry blight fungi frequently have spots or discoloration on the hulls;<br />
however, this is not always the case. C. miyaheanus is one o f the chief causes o f seedling<br />
blight <strong>and</strong> is seedborne. A seedling attacked by this fungus has dark areas on the basal<br />
parts o f the first leaf.<br />
The soilborne blight fungus, S. rolfsii, sometimes kills or severely injures large<br />
numbers of rice seedlings after emergence if the weather at emergence time is m oist<br />
<strong>and</strong> warm. A cottony white mold develops on the lower parts o f affected plants.<br />
Flooding the field immediately can reduce this type o f blight.<br />
■
418 Production<br />
Planting fungicide treated seeds is recommended to ensure adequate st<strong>and</strong>s. Protectant<br />
fungicides can control some blight fungi that affect rice seedlings at the tim e of<br />
germination. Systemic fungicides give longer control. If rice seeds are to be sown early<br />
in the season, seed treatm ent can mean the difference between getting a satisfactory<br />
st<strong>and</strong> or having to plant a second time. Treating rice seeds later in the season shows<br />
less benefit unless poor conditions for st<strong>and</strong> establishment prevail. Proper cultural<br />
methods for rice <strong>production</strong>, such as proper planting date <strong>and</strong> shallow seeding, help<br />
control the seedling blight fungi.<br />
Root <strong>and</strong> Crown Diseases<br />
* i;:" i ! '<br />
liHi: i'<br />
Root Rot A complex of fungi, including Fusarium spp., Pythium spp., P. dissotocum<br />
Drechs., <strong>and</strong> P. spinosum Sawada, causes root rots. Root rots are one o f the most com <br />
m on but m ost missed or undiagnosed rice diseases. Often, the same pathogens tliat<br />
cause seed <strong>and</strong> seedling damage continue to cause problems as root rots. Identification<br />
o f the caqsal organism is difficult because o f secondary infections, <strong>and</strong> culturing the<br />
pathogen on nonselective media is difficult.<br />
Root rots occur in all rice-growing regions o f the world. The rice plant may be ^<br />
predisposed to these disorders by a com bination o f factors, including physiological<br />
stress; insect feeding, especially feeding o f rice water weevil larvae; nematodes; ex-<br />
treriie environmental conditions, <strong>and</strong> various other pathogens that weaken the upper<br />
plant. Root rots are divided into two main divisions based on the size o f root infected.<br />
Normal root rot is when lapger prim ary roots develop obvious discoloration<br />
<strong>and</strong> necrosis, often caused by a com bination o f insect damage <strong>and</strong> root rotting fungi<br />
(Figure 3.5.2; see color insert). Feeder root necrosis occurs when the smaller feeder<br />
roots develop reddish-brown lesions. Symptoms are hard to detect <strong>and</strong> appear as<br />
aboveground stunting, unresponsiveness to fertilizers, uneven maturity, or nutrient-<br />
deficiency symptoms. Soilborne fungi infect plant roots, usually through wounds.<br />
Root rots are one o f the m ost underestimated yield constraints in rice because<br />
damage is not detected until nutrient deficiencies are noted on tlie aboveground<br />
plant parts. No yield loss estimates are available for this disease complex because<br />
of the hidden nature of this disease. Often, damage occurs without any symptoms<br />
apparent on the upper plant. Symptoms can appear as soon as seedlings emerge <strong>and</strong><br />
continue until maturity. Due to poor plant growth, weed com petition also reduces<br />
productivity. Typical symptoms appear as brow n-to-black discoloration, necrosis,<br />
<strong>and</strong> root decay. Under severe disease pressure, young seedlings can die, <strong>and</strong> mature<br />
plants lack support from the roots <strong>and</strong> lodge or even float, causing harvest problems.<br />
Under heavy root infections, plants often show severe brown leaf spot infection. The<br />
disease is favored by cool temperatures <strong>and</strong> is less severe in drill-seeded rice. Since<br />
most o f the root-rotting pathogens produce water mobile spores, the disease is worse<br />
under wet, waterlogged environmental conditions. Planting vigorous, healthy rice<br />
seed treated with a seed protectant fungicide helps the resulting plants to outgrow<br />
early season development. Soil fungicides have been suggested, but erratic results <strong>and</strong><br />
questionable econom ics do not justify their use.<br />
Fertilizer usually reduces the aboveground symptoms, altliough actual nutrient<br />
use is impaired. <strong>Rice</strong> water weevil control often reduces root rots. Draining fields
<strong>Rice</strong> Diseases 419<br />
stimulates root growth that reduces disease severity but can cause problems with blast,<br />
weeds, or nutrient efficiency.<br />
Minor Root <strong>and</strong> Crown Diseases<br />
Bakanae (or Foot Rot). Bakanae (Japanese for foolish seedling) disease, caused by the<br />
fungus Fusarium moniliforme Sheld. [Gibberellajujikuroi (Sawada) Ito], is distributed<br />
widely in Asia but was recently found in the United States in California (Boyd, 2000).<br />
Symptoms consist mainly o f elongated, thin, <strong>and</strong> yellowish seedlings. Seedlings also<br />
can be stunted <strong>and</strong> yellowed <strong>and</strong> have severe crown <strong>and</strong> root rot. W hen older plants<br />
are infected, they can exhibit elongation <strong>and</strong> produce adventitious roots at the lower<br />
nodes. Surviving plants are sterile, producing no grain. The fungal pathogens produce<br />
the growth horm ones gibberellin <strong>and</strong> fusaric acid, which produce elongation <strong>and</strong><br />
stunting, respectively in the rice plant. The type <strong>and</strong> severity o f symptoms depend on<br />
the fungal strain <strong>and</strong> inoculum level o f the pathogen. Lightly infected seeds normally<br />
produce the bakanae symptom in the seedlings, while more heavily infected seeds<br />
produce stunted seedlings that often die. Inoculum is present on seeds <strong>and</strong> can be<br />
windblown from early seedling infections to healthy seedlings. As infected plants<br />
mature, older leaves die <strong>and</strong> dry up, <strong>and</strong> a pink-to-white fungal mycelial m at may<br />
appear on the stem. Spores spread from this to infect seedheads <strong>and</strong> contaminate<br />
seeds during harvesting. H ot weather <strong>and</strong> high nitrogen levels favor the disease. Other<br />
grain-infecting Fusarium species can cause panicle discoloration. Some Oryzae weed<br />
species could be misidentified as balcanae. Over application or uneven application o f<br />
the gibberellic add seed treatments also could be confused with this disease.<br />
Crown Rot. The bacterium Erwinia dirysanthemi Burkholder et al. (Goto, 1979) or<br />
an unidentified fungus causes crown rot. Symptoms appear during tillering <strong>and</strong> can<br />
continue through maturity. Normally, the crown decays, forming an area o f dark<br />
brown to black soft rot with discolored streaks extending into the lower internodes<br />
<strong>and</strong> roots. A diagnostic characteristic is the distinctive soft rot smell o f the plant<br />
tissues. Tillers die one by one <strong>and</strong> the roots also die. Adventitious roots grow from<br />
above the crown. Similar discoloration <strong>and</strong> secondary rotting can be produced by<br />
misapplied herbicides, especially Phenoxy herbicides. Crown rot is a m inor disease<br />
<strong>and</strong> causes severe damage only under unique situations. The only control m ethod is<br />
to drain the field to aerate the soil to encourage rooting <strong>and</strong> tillering.<br />
Root Knot Species o f the nematode genus Meloidogyne cause root laiot. Symptoms<br />
include enlargement o f the root <strong>and</strong> the formation o f Imots or galls caused by hypertrophy<br />
<strong>and</strong> hyperplasia o f root tissues. The nematode survives as eggs in the soil or<br />
on alternative hosts. Second-stage mobile juveniles o f the nematode enter the roots<br />
before flooding <strong>and</strong> gl<strong>and</strong>ular secretions start gall formation. The swollen female<br />
nematode is found in the center o f tins tissue <strong>and</strong> lays her eggs inside the root. The<br />
eggs hatch <strong>and</strong> cause secondary infections. Aboveground symptoms are expressed as<br />
dwarfing, chlorosis, <strong>and</strong> poor vigor. The nematode becomes inactive after prolonged<br />
flooding. The nematode is favored by coarse-textured soils. R oot knot on rice is very<br />
rare, <strong>and</strong> yield losses have never been shown. No control methods are recommended<br />
in the United States.<br />
m
420 Production<br />
Stem <strong>and</strong> Culm Diseases<br />
Sheath Blight. Sheath blight occurs in all rice-growing areas. The causal organism is<br />
Thanatephorus cucumeris (A. B. Frank) D onk (anamorph: Rhizoctonia solani Kuhn),<br />
It is the m ost im portant rice disease in the southern United States <strong>and</strong> worldwide<br />
is second only to blast. Sheath blight is a product o f the Green Revolution, including<br />
the introduction o f shorter stature, higher tillering cultivars, increased fertilization,<br />
<strong>and</strong> higher plant st<strong>and</strong>s. Losses range from 1 to 50% , depending on inoculum<br />
pressure, plant growth stage when infection takes place, environmental conditions,<br />
host resistance, <strong>and</strong> cultural management (Gangopadhyay <strong>and</strong> Chakrabarti, 1982;<br />
Marchetti, 1983; Groth et al., 1991). High humidity <strong>and</strong> temperature favor the disease.<br />
Close transplanting, higli seeding rates, <strong>and</strong>/or high doses o f nitrogen increase canopy<br />
thickness <strong>and</strong> thus increase humidity, resulting in increased disease (Shahjahan <strong>and</strong><br />
Mew, 1989; Groth <strong>and</strong> Bollich, 2000).<br />
Most species o f plants are susceptible to the pathogen, <strong>and</strong> many alternative<br />
crops, including soybeans, are susceptible <strong>and</strong> add inoculum to the soil. The pathogen<br />
survives in the soil as sclerotia, in infected straw, or on alternative hosts <strong>and</strong> is endemic<br />
in m ost rice fields. Floodwater <strong>and</strong> soil movement during tillage may move the<br />
pathogen. Inoculum in the soil causes the primary infection. Severity is proportional<br />
to the number o f sclerotia <strong>and</strong> infected debris in the soil. Infection occurs at the point<br />
o f contact <strong>and</strong> mycelium penetrates the plant, usually at the tillering or internode<br />
elongation growth stages, around the waterline. The infection process starts with the<br />
formation on an infection cushion <strong>and</strong> penetration. Three types o f specialized hyphae<br />
are produced in <strong>and</strong> on the plant (Lee <strong>and</strong> Rush, 1983). Runner hyphae are produced<br />
on the leaf <strong>and</strong> sheath surface <strong>and</strong> have thick parallel walls. These hyphae give rise to<br />
swollen, lobate appressoria or clumps o f appressoria called infection cushions. From<br />
these hyphae, infection pegs form <strong>and</strong> fungus enters the plant through stomata or<br />
directly through the cuticle. The mycelium spreads in the plant tissues both inter-<br />
<strong>and</strong> intracellularly <strong>and</strong> on the surface o f the plant. Lesions, 1 to 3 cm in size, initially<br />
appear on the sheath, are oval or ellipsoidal, dark green to gray in color, <strong>and</strong> appear<br />
water soaked (Figure 3.5.3; see color insert). Lesions usually have a brown border<br />
around them , with resistant plants having a wider <strong>and</strong> darker border than susceptible<br />
cultivars. W hen the plant produces this resistant response, the mycelium grows out of<br />
the tissue <strong>and</strong> over the resistance reaction <strong>and</strong> causes a new secondary infection. This<br />
process gives the disease its characteristic appearance o f a snakeskin-b<strong>and</strong>ing pattern<br />
(Figure 3.5.4; see color insert). Lesions on the leaves are more irregular <strong>and</strong> have a<br />
b<strong>and</strong>ed coloration with dark green, brown, <strong>and</strong> yellow-orange coloration. Large oval<br />
spots on the sheath <strong>and</strong> irregular spots on the leaf blades characterize the disease. If<br />
the flag leaf becom es infected before heading, head exertion can be affected (Figure<br />
3.5.5; see color insert). Leaves that becom e infected usually die <strong>and</strong> turn tan. The<br />
third type o f mycelium is a thick-walled, short, dark-pigmented monilioid cell that<br />
produces chains o f cells tliat form sclerotia. Sclerotia are the survival structures o f<br />
the fungus, irregular bean-shaped 4 to 5 m m in size, <strong>and</strong> formed on the surface of<br />
the leaves <strong>and</strong> sheaths. W lien formed initially, they are white but turn dark brown<br />
to black <strong>and</strong> fall off easily. At first, they are dense <strong>and</strong> sink in the water, but as they<br />
mature, outer cells empty <strong>and</strong> the sclerotia can float. The sclerotia can survive several<br />
years in the soil. The perfect stage occurs on the rice plant, especially in very humid<br />
conditions <strong>and</strong> appears as a pink-to-salm on colored layer on the lesions. Basidio spore
<strong>Rice</strong> Diseases 421<br />
infections occur, but they are not considered epidemiologically important. Although<br />
a soilborne pathogen without a secondary wind-spread spore stage, sheath blight can<br />
develop rapidly under the favorable environmental conditions (Shahjahan <strong>and</strong> Mew,<br />
1989; Savary et al., 1997)<br />
Sheath blight can be controlled by a com bination o f practices. Some com mercial<br />
cultivars have partial resistance, but im m unity to the pathogen has not been found.<br />
Several lines <strong>and</strong> cultivars have been identified with high levels o f resistance (Pan et al.,<br />
1999). This resistance has been shown to be controlled by several m ajor genes, both<br />
dominant <strong>and</strong> recessive. Resistance is expressed as increased cuticulai' wax, reduced<br />
infection structure form ation, <strong>and</strong> <strong>production</strong> o f phenolic compounds in the tissue.<br />
Several negative traits are associated with this resistance, including tall plants, late m a<br />
turity, <strong>and</strong> poor grain quality. Early-maturing, short-stature, high-tillering cultivars<br />
appear to be m ore susceptible tlian later, taller, <strong>and</strong> reduced tiller cultivars. Avoiding<br />
excessive st<strong>and</strong>s <strong>and</strong> nitrogen fertilizer, without sacrificing yield potential, will reduce<br />
incidence o f this disease. Green manure, soil solarization, burning straw, <strong>and</strong> deep<br />
plowing to bury inoculum have been suggested but are not very effective. Applying<br />
fungicides is often necessary when advisable econom ically (Groth et al., 1993; Giesler<br />
et al., 1994). The rice must be scouted to determine if a treatment threshold has been<br />
exceeded. Specific fungicide treatment recommendations are based on either percent<br />
positive tillers infected or percent positive stops (Groth et al., 1992; Cartwright <strong>and</strong><br />
Lee, 2001). This threshold is adjusted for the susceptibility o f the cultivar. W ith a<br />
susceptible cultivar, 5 to 10% o f tlie tillers infected or 35% positive stops indicate that<br />
a fungicide is necessary. A moderately susceptible cultivar requires 10 to 15% infected<br />
tiUers or 50% positive stops to justify a fungicide treatment. In the past, two fungicide<br />
treatments were necessary to reduce sheath blight, but with the advent o f more<br />
effective fungicides <strong>and</strong> econom ic constraints that lim it the num ber o f applications,<br />
a single application approach is generally used (Groth, 1996). Som e fungicides have<br />
been shown to cause more sheath blight due to rapid development after they have lost<br />
their activity (Van Eeckhout et al., 1991). A shift o f the epiphytic population o f antagonist<br />
caused by the fungicide’s broad-spectrum activity was suggested as the cause.<br />
Stem Rot The fungus Magnaporthe salvinii (Cattaneo) R. Krause & Webster [synana-<br />
morphs: Sclerotium oryzae Cattaneo, Nakataea sigmoidae (Cavara) K. Hara] causes<br />
stem rot. Losses usually are not detected until late in the season, when control practices<br />
are too late. Damage appears as severe lodging, which makes harvesting difficult. Seed<br />
sterility also has been reported.<br />
The first symptom is irregular-shaped black angular lesions on leaf sheaths near<br />
the waterline at tillering or later growth stages (Figure 3.5.6; see color insert). Lesion<br />
edge form ation is limited by leaf cross veins <strong>and</strong> often appear angular at the margins.<br />
As lesions develop, the outer sheath may die <strong>and</strong> the fungus penetrates the inner<br />
sheaths <strong>and</strong> culm. These becom e discolored <strong>and</strong> have similar black or dark brown lesions.<br />
The dark brown or blade streaks may have raised areas o f dark fungal mycelium<br />
on the surface <strong>and</strong> gray mycelium inside the culm <strong>and</strong> rotted tissues. At maturity, the<br />
softened culm breaks over, plants lodge, <strong>and</strong> numerous small (180 pm to 280 /zm),<br />
round, black sclerotia develop in the dead tissues.<br />
The pathogen overwinters as sclerotia in the top 5 to 10 cm o f soil <strong>and</strong> in plant debris.<br />
W hen early floods are established, the hydrophobic sclerotia float on the surface<br />
o f the water <strong>and</strong> often accumulate along die edge o f the field <strong>and</strong> on levees because of
422 Production<br />
wind action. After a perm anent flood is established, the sclerotia float to the surface,<br />
com e in contact with the plant, germinate, <strong>and</strong> infect the tissues near the plant-water<br />
interface. The fungus then penetrates the inner sheaths <strong>and</strong> culm, often killing the<br />
tissues. The fungus can continue to develop in the stubble after harvest, <strong>and</strong> numerous<br />
sclerotia are produced.<br />
High levels o f resistance to stem rot are not available. High nitrogen <strong>and</strong> low<br />
potassium levels favor the disease. Generally, early-maturing cultivars are less affected<br />
by stem rot. Stem rot is more serious in fields that have been in rice <strong>production</strong> for<br />
several years.<br />
Suggested control measures include using early-maturing cultivars, avoiding very<br />
susceptible cultivars, burning or destroying crop residue by cultivation, using crop<br />
rotation when possible, avoiding excessive nitrogen rates, <strong>and</strong> using foliar fungicides.<br />
Potassium fertilizer may reduce disease severity in soils where potassium is deficient.<br />
..g-:<br />
m ■<br />
I<br />
Crown Sheath Rot The fungus Gaeumannomyces graminis (Sacc) Arx & D. Olivier<br />
causes crown sheath rot. Other names for this disease include brown sheath rot, foot<br />
rot, <strong>and</strong> black sheath rot. The disease normally is considered a m inor problem except<br />
under heavy nitrogen fertilization. The fungus infects the lower leaves <strong>and</strong> sheaths<br />
<strong>and</strong> penetrates the culm, often causing lodging. Symptoms normally appear after<br />
heading on the lower stems. The lesions are dark brown to black with a diffuse margin<br />
(Figure 3.5.7; see color insert). There is a reddish-brown myclial m at formed on the<br />
inside of the sheath. Dark perithecia, with beaks protruding through the epidermis,<br />
are produced in the tissue of the outside leaf sheath. Symptoms can easily be confused<br />
with stem rot, but crown sheath rot has a diffuse lesion border <strong>and</strong> stem rot has an<br />
angular lesion. The fungus survives as perithecia <strong>and</strong> mycelium in rice residues. The<br />
same fungus produces similar diseases on wheat <strong>and</strong> other grasses. The fungus has<br />
been reported to be seedborne. Specific control practices usually are not warranted.<br />
Avoid excessive nitrogen fertilization.<br />
Minor Stem Diseases<br />
Aggregate Sheath Spot The fungus Ceratobasidium oryzae-sativae Gunnell & Webster<br />
causes aggregate sheath spot (anamorph: Rhizoctonia oryzae-sativae (Sawada) Mor-<br />
due). The disease is found in Asia. In the United States, the disease was first reported in<br />
California but has now been identified in the southern <strong>production</strong> area. The disease is<br />
characterized by small circular to long oval lesions, which are at first water-soaked <strong>and</strong><br />
green, then turn tan with a narrow brown margin. The key diagnostic characteristic<br />
is a thin dark strip down the center o f the lesion best viewed when the leaf is held up<br />
against a light. Lesions spread up the plant to the upper leaf sheaths <strong>and</strong> to the base of<br />
the leaves. Affected leaves turn yellow <strong>and</strong> die. Occasionally, the fungus penetrates the<br />
stem or infects the head, causing lodging <strong>and</strong> sterility. The fungus survives as sclerotia<br />
<strong>and</strong> infected plant debris in the soil. Other grass species are infected <strong>and</strong> may act as a<br />
source of inoculum. Nitrogen does not appear to favor aggregate sheath spot as it does<br />
sheath blight <strong>and</strong> sheath spot. The disease is similar to sheath blight <strong>and</strong> sheath spot.<br />
Control measures are usually not warranted. Inoculum management by destroying<br />
organic matter that is associated witli fungal survival is the best control measure.<br />
Sheath Rot Sheath rot is caused by the fungal pathogen Sarodadium oryzae (Sawada)<br />
W, Gams & D. Hawksworth = Acrocylindrium oryzae Sawada <strong>and</strong> is fouffd in most
<strong>Rice</strong> Diseases 423<br />
rice-growing areas o f the world (Singh <strong>and</strong> Dodan, 1995). Symptoms are m ost severe<br />
on the uppermost leaf sheath that encloses the young panicle. Lesions may be oblong<br />
or irregularly oval spots with gray or light-brown centers <strong>and</strong> a dark reddish-brown<br />
diffuse margin (Figure 3,5.8; see color insert). It is com mon on United States rice<br />
cultivars for the lesion to consist o f general reddish-brown discoloration o f the flag<br />
leaf sheath. A powdery white growth, consisting o f spores <strong>and</strong> hyphae o f the pathogen,<br />
may be observed on the inside o f affected leaves. Early or severe infections may affect<br />
the panicle so that it emerges only partially. The unemerged portion o f the panicle<br />
rots, with florets turning red-brown to dark brown. Insect or m ite damage to the<br />
boot or leaf sheatlis increases tlie damage from this disease. Emerged panicles may be<br />
damaged with florets discolored reddish brown to dark brown <strong>and</strong> unfilled grain. The<br />
fungus is seedborne.<br />
Some cultivar resistance is available. The disease is usually minor, affecting scattered<br />
tiUers in a field <strong>and</strong> plants along the levee (Shahjahan et al., 1977; Groth <strong>and</strong><br />
Hollier, 1986). Occasionally, large areas o f a field may have significant damage. No<br />
control measures are recommended. Fungicidal sprays used in a general disease control<br />
program may reduce damage. Seed treatment with a fungicide can improve<br />
seedling establishment.<br />
Sheath Spot The fungus Rhizoctonia oryzae Ryker 8i Gooch causes sheath spot. The<br />
disease resembles sheath blight on resistant cultivars but is usually less severe <strong>and</strong> the<br />
spots are separate. Sheath spot lesions are found on sheaths or on leaf blades. Lesions<br />
are irregularly oval, 0.5 to 2 cm long <strong>and</strong> 0.5 to 1 cm wide. The center portion o f<br />
the lesion tends to be white to tan, with a broad dark reddish-brown margin (Figure<br />
3.5,9; see color insert). Lesions usually are separated on the sheath or blade. The<br />
pathogen may penetrate the stem <strong>and</strong> damage the culm, causing lodging. The disease<br />
develops under high-nitrogen fertilization. This disease is usually m inor <strong>and</strong> causes<br />
little damage. Avoid excessive nitrogen fertilization. Fungicides used to control sheath<br />
blight also may reduce sheath spot. No other control practices are recommended.<br />
Foliar Diseases<br />
Blast The fungus Pyriculuria grísea Sacc [= P. oryzae Cavara (teleomorph: Magnaporthe<br />
grísea (Hebert) Barr] causes blast. Blast is die m ost im portant disease o f rice in<br />
the world <strong>and</strong> is second only to sheath blight in the United States. Blast epidemics are<br />
dependent on favorable clim atic conditions <strong>and</strong> acreage distribution o f susceptible<br />
varieties but tend to be m ore sporadic than sheath blight. Long-grain varieties tend<br />
to have more partial or field resistance to blast than sheath blight, <strong>and</strong> high levels<br />
o f single gene resistance are available. The blast fungus overwinters in rice stubble<br />
<strong>and</strong> on seeds. Weeds have been implicated as a source o f inoculum, but these isolates<br />
appear not to infect rice readily. This disease stage spreads rapidly in <strong>and</strong> between<br />
fields by airborne spores. The epidemic is bimodal, having two periods o f maximum<br />
disease development. The first stage of rapid development begins during tillering <strong>and</strong><br />
decreases as the plants approach early reproductive stages (panicle initiation). This<br />
disease stage is characterized by elongated, spindle-shaped lesions with brown borders<br />
on the leaves (Figure 3.5.10; see color insert). Lesions can vary from brown specks<br />
on resistant cultivars to very elongated lesions on susceptible cultivars. A range o f
424 Production<br />
symptoms can occur on a single rice leaf because o f the occurrence of compatible<br />
<strong>and</strong> incompatible races infecting the plant. Severe infections can lead to large dead<br />
areas in the field. Severe leaf blast is usually associated with flood loss or prolonged<br />
flood delay. Warm days (25 to 28°G) <strong>and</strong> cool nights (17 to 23°C) favor infection. Leaf<br />
wetness is critical for spore germination, appressorium form ation, <strong>and</strong> penetration<br />
into the plant. Lesions form after 4 to 14 days, depending on temperature. Spore <strong>production</strong><br />
begins 2 to 3 days after lesion form ation <strong>and</strong> appears as a blue-gray covering<br />
over the lesion. Spore <strong>production</strong> requires 90% or higher relative humidity. Lesions<br />
can produce spore for many days. The second active period o f disease <strong>and</strong> the most<br />
damaging development begins at heading. Lesions develop on the node at the base of<br />
the head, causing empty or partially filled florets or blasting (Figure 3.5.11; see color<br />
insert) followed by breaking over o f the head to produce the “rotten-neck” symptom.<br />
Infection can also occur on branches o f the head, causing panicle blast (Figure 3.5.11;<br />
see color insert). Depending on the time of infection, grain sterility can range from<br />
100% with early infection to a trace with late infection. Infection also can occur at the<br />
flag leaf collar, sometimes causing leaf death (Figure 3.5.11; see color insert). Rarely,<br />
lower nodes within the sheath can also becom e infected with node blast (Figure 3.5.12;<br />
see color insert), causing lodging.<br />
Host resistance is the most effective control measure for blast. Cultivars differ<br />
greatly in their level o f resistance, <strong>and</strong> selection o f a resistant cultivar is one o f the<br />
most im portant decisions that a farmer makes. Resistance to blast is a m ajor objective<br />
of most rice-breeding programs. Single gene resistance has been used extensively, <strong>and</strong><br />
most U.S. germplasm also has a high level o f partial resistance to many races, called<br />
horizontal resistance. Unfortunately, the blast fungus population is very plastic <strong>and</strong><br />
can overcome resistance; resistance is incorporated into new cultivars <strong>and</strong> the cycle<br />
repeats itself ad infinitum.<br />
Establishing <strong>and</strong> maintaining a flood as soon as possible is the second most<br />
important management tool. Planting early avoids late-season blast pressure. Use the<br />
recommended N fertilizer rate <strong>and</strong> avoid excessive N rates on susceptible cultivars.<br />
Do not plant susceptible cultivars in s<strong>and</strong>y soils or in tree-lined fields that hold more<br />
moisture <strong>and</strong> are prone to blast. Scout fields for leaf blast starting around midtillering<br />
through heading. If leaf blast is present, a blast fungicide should be applied, at least at<br />
heading. Boot <strong>and</strong> heading applications are more effective, but econom ics limit the<br />
number o f applications. Heading applications should occur when 40 to 60% o f the<br />
heads are emerging from the boot. Applications 5 to 10 days after tliis time reduce<br />
fungicide efficacy (D. E. Groth, in press).<br />
i : : -<br />
Brown Spot Brown spot is one o f the m ost com m on rice diseases in the world. The<br />
pathogen is Cochltobolus miyabeanus (Ito & Kuribayashi) Drechs. ex. Dastur [anamorph:<br />
Bipolaris oryzae (Breda de Haan) Shoemaker, Helminthosporium oryzae].<br />
Losses in st<strong>and</strong> due to seedling blight, yield due to leaf spotting, <strong>and</strong> quality due<br />
to grain infection frequently are severe in low input cultural systems. The Bengal<br />
famine in the 1940s was attributed primarily to this disease (Ou, 1985). The disease<br />
can develop on seedling to heading growth stages. Seedling infections cause small<br />
circular brown lesions that can damage tire plant <strong>and</strong> result in sparse st<strong>and</strong>s <strong>and</strong> weak<br />
seedlings (see seedling blights). Infected seedlings may die, but older plants survive.<br />
Leaf spots start as small dark brown to reddish-brown lesions. As spots enlarge, they<br />
have dark brown margins <strong>and</strong> a light reddish-brown center <strong>and</strong> a yellowish border
<strong>Rice</strong> Diseases 425<br />
(Figure 3.5.13; see color insert). As spots mature, the centers turn gray with distinct<br />
dark brown borders. The num ber o f spots on a single leaf ranges from 1 to over 100.<br />
On susceptible cultivars, leaf spots are oval, 1.5 to 2 cm, <strong>and</strong> evenly distributed on the<br />
leaf. On resistant cultivars, they range from tiny brown pin spots to smaller, typical leaf<br />
lesions. Leaf spots can start developing from seedling growth stage on, but are more<br />
prevalent as the plant approaches maturity. Leaf symptoms are often confused with<br />
blast lesions, <strong>and</strong> careful inspection <strong>and</strong> examination o f spore types after incubation<br />
in a moist chamber may be necessary for proper identification. Spots on the sheath<br />
<strong>and</strong> grain are similar to those on the leaves except that they are smaller. The fungus<br />
can also attack the immature floret, resulting in no grain filling or light <strong>and</strong> chalky<br />
grain. Infection on the grain causes a glume blotch that can penetrate the grain <strong>and</strong><br />
cause significant quality loss (see the section “Pecky <strong>Rice</strong>”).<br />
The fungus is seedborne as mycelium or spores. Seed incubated in m oist cham <br />
bers have masses o f dark brown to almost black masses o f spores <strong>and</strong> mycelium. The<br />
fungus becomes active when the seed is planted <strong>and</strong> produces conidia <strong>and</strong> hyphal<br />
masses. These are spread by wind <strong>and</strong> rain, causing secondary infections. Stubble o f<br />
the previous crop <strong>and</strong> numerous weed hosts may play some role in the epidemiology<br />
o f the disease as sources o f inoculum. Damage to roots from water weevil <strong>and</strong> root<br />
rots can increase prevalence. Brown spot can show up under dry conditions that are<br />
n ot favorable to other diseases. This may be because spores require only a short wet<br />
period for germination <strong>and</strong> infection tube penetration.<br />
Brown spot is an indicator o f plant stress, especially a soil nutrient deficiency.<br />
These stresses include low nitrogen, potassium, silica, iron, <strong>and</strong> calcium fertility. M aintaining<br />
good growing conditions, including proper fertilization, crop rotation, pest<br />
control, water management, <strong>and</strong> soil preparation, will reduce damage from brown<br />
spot. Some seed-protectant fungicides reduce seedborne inoculum <strong>and</strong> protect seedlings<br />
from infection. Some varietal resistance is available. Silicon fertilization on<br />
low-silicon soils has shown good activity in reducing disease (D atnoff et al., 1997).<br />
Applications of foliar fungicides targeted at other diseases may reduce brown spot but<br />
would be uneconomical for brown spot control only (Groth et a l, 1993).<br />
Narrow Brown Leaf Spot The fungus Cercospora janseana (Racib) O. Const. = C,<br />
oryzae Miyake (teleomorph: Sphaerulina oryzina K. Hara) causes narrow brown leaf<br />
spot. Narrow brown occurs in most rice-growing areas o f the world. Its severity varies<br />
from year to year <strong>and</strong> is more severe as rice approaches maturity. Spots are linear in<br />
shape <strong>and</strong> reddish brown in color (Figure 3.5.14; see color insert). Narrow, brown<br />
elongated spots range from 2 to 12 m m in length <strong>and</strong> 1 to 2 ram in width. On<br />
susceptible cultivars, the lesions are wider, more numerous, <strong>and</strong> are lighter brown<br />
with gray necrotic centers. They tend to be narrower, shorter, <strong>and</strong> darker on resistant<br />
cultivars. Spots usually appear near heading <strong>and</strong> are slow to develop, talcing up to 30<br />
days from infection. Both young <strong>and</strong> old leaves are susceptible. Seedheads can become<br />
infected, causing premature ripening <strong>and</strong> unfilled grain. Symptoms can be confused<br />
with rotten neck <strong>and</strong> panicle blast lesions; narrow brown disease lesion symptoms<br />
usually are darker brown <strong>and</strong> develop in the iiiternodal area o f the neck. Sheaths <strong>and</strong><br />
glumes can be infected, causing significant discoloration <strong>and</strong> necrosis. On sheaths,<br />
the disease is referred to as net blotch, because o f the brown sheath cell walls <strong>and</strong> the<br />
tan-to-yellow intracellular areas that form a netlike pattern. Grain infection appears<br />
as a diffuse brown discoloration.
426 Produttíon<br />
<strong>Rice</strong> breeders have found resistance to narrow brown leaf spot (Groth et al,,<br />
1991), but new races o f the pathogen develop rapidly. Fimgicides used to reduce<br />
other diseases may reduce narrow brown leaf spot (Groth et al., 1993). Low nitrogen<br />
favors disease development. Resistance often bréalas down after several years, because<br />
o f genetic adaptation by the fungus.<br />
Minor Foliar Diseases<br />
■; Mi,<br />
Alternaría Leaf Spot. Alternaría leaf spot is caused by the ftmgal pathogen Alternaría<br />
padwickii (Ganguly) M. B, Ellis. It is com m on on rice around the world. The disease<br />
is present in m ost rice fields in the southern United States. Under normal conditions,<br />
only occasional spots are observed, but the disease may be more severe in restricted<br />
areas o f a field. The spots are typically large, 0,5 to 1 cm in diameter, oval or circular,<br />
with a dark brown margin or ring around the spot (Figure 3.5.15; see color insert). The<br />
center o f the spot is initially tan <strong>and</strong> eventually becomes white or nearly white. Mature<br />
spots have small dark or black dots in the center, which are sclerotia o f the fungus.<br />
Grain or seeds affected )Dy the disease have tan-to-white spots with a wide, dark brown<br />
border. The disease is often confused with herbicide spotting <strong>and</strong> leaf blast lesions.<br />
The disease may cause kernel discoloration or kernel may stop developing.<strong>and</strong> become<br />
shriveled. This seedborne fungus is one o f the m ost com m on pathogens detected on<br />
rice (Mew <strong>and</strong> Misra, 1994) <strong>and</strong> may cause blighted seedlings. The disease is more<br />
common on panicles <strong>and</strong> grain than on leaves. W hen grain is stored at high moisture<br />
levels. A, padwickii <strong>and</strong> other fungi can cause grain damage called stackhurn. Seed-<br />
protectant fungicides will help control the seedling blight caused by this pathogen <strong>and</strong><br />
will reduce the num ber o f spores present to cause leaf infections. No other control<br />
measures are warranted.<br />
:<br />
Bacterial Blight. Bacterial leaf blight is caused by the bacterium Xanihomonas oryzae<br />
pv, oryzae (Ishiyama) Swings et al. = X. campestris pv. oryzae (Ishiyama) Dye. The<br />
disease was first identified in the United States in Texas <strong>and</strong> Louisiana in 1987. No<br />
major losses have been associated with this disease in the United States, but major<br />
yield losses have occurred in other parts o f the world. The bacterium overwinters in<br />
rice debris, in soil, on weed hosts, <strong>and</strong> on seed. The pathogen spreads in windblown<br />
rain, irrigation water, plant contact, <strong>and</strong> plant debris. High relative humidity, storms,<br />
<strong>and</strong> rainfall favor tlie disease. Linear water-soaked lesions appear on the leaves near<br />
the margin <strong>and</strong> leaf tips. As lesions mature, they exp<strong>and</strong>, usually along the veins,<br />
turn yellow to white, <strong>and</strong> then gray, because o f growth o f saprophytic fungi (Figure<br />
3.5.16; see color insert). Lesions may exp<strong>and</strong> to several inches long <strong>and</strong> have wavy<br />
margins. W hen a young lesion is sectioned through with a razor or scalpel, placed in<br />
water on a microscope slide, <strong>and</strong> observed under a microscope, bacterial streaming<br />
can be detected. Older lesions may not show bacterial streaming. Yellow droplets of<br />
bacteria may develop on the plant under humid conditions. Saprophytic organisms<br />
often develop on old lesions <strong>and</strong> confuse identification. Symptoms may also appear<br />
on the seedling leaf sheaths <strong>and</strong> grains under very favorable conditions. Management<br />
practices are not recommended in the United States, but in Asian countries,<br />
resistant cultivars, rotation to nongrass crops, <strong>and</strong> tillage to destroy rice debris are<br />
recommended.<br />
I
ü<br />
Ríce Diseuses 427<br />
Bacterial Streak. Bacterial streak is caused by the bacterium Xanthomonas oryzae pv.<br />
oryzkola (Ishiyama) Swings. Bacterial streak is widespread in Asia <strong>and</strong> Africa but has<br />
not been found in the United States. This disease is included in this chapter because o f<br />
its high potential through seed transmissioUj to be introduced into the United States.<br />
Yield losses are variable, dependent on hot humid environmental conditions <strong>and</strong> host<br />
susceptibility. Interveinal streaks appear on the leaves under high temperature <strong>and</strong><br />
humidity conditions during all growth stages. Fresh lesions are translucent <strong>and</strong> may<br />
have a yellow halo around them , but older lesions turn brown (Figure 3.5.17; see<br />
color insert). W hen a lesion is sectioned <strong>and</strong> observed under a microscope, bacterial<br />
streaming can be detected. Severe infection Idlls the leaves. Yellow droplets of bacteria<br />
may develop on the plant under humid conditions. Saprophytic organisms often develop<br />
on old lesions <strong>and</strong> confuse identification. The pathogen is seed transmitted <strong>and</strong><br />
is carried in floodwater, then spread through splashing <strong>and</strong> plant contact. Resistant<br />
cultivars are the m ajor control method, but pathogen-free seed <strong>and</strong> seed treatments<br />
also reduce incidence.<br />
Eyespot. Eyespot is caused by the fungus Drechslera gigantea (Heald & K A. W olf)<br />
Ito. It is a very rare disease that does not cause m uch damage. Lesions are small<br />
ovals with a well-defined brown margin. Under favorable environmental conditions,<br />
lesions coalesce <strong>and</strong> produce characteristic zonate patterns. Control measures are not<br />
warranted.<br />
Leaf Scald. Leaf scald is caused by the fungus Micrododiium oryzae (Hashioka h<br />
Yokogi) Samuels 8i I. C. Hallett — Rhynchosporium oryzae Hashioka & Yokogi. This<br />
disease is com m on in m ost rice-growing regions around the world <strong>and</strong> severe in<br />
Central <strong>and</strong> South America (Shanmughon et al., 1973). Leaf scald is normally m inor<br />
on rice in the United States.<br />
The disease affects leaves, panicles, <strong>and</strong> seedlings. The pathogen is seedborne<br />
<strong>and</strong> survives between crops on infected seeds, dry infected plant tissues, <strong>and</strong>/or weed<br />
hosts. The disease usually occurs on maturing leaves. Lesions may start on leaf tips<br />
or from leaf margins. The lesions may have a chevron or semicircular pattern o f light<br />
(tan) <strong>and</strong> darker reddish-brown areas (Figure 3.5.18; see color insert). The leading<br />
edge o f the lesion usually is yellow or gold, giving affected fields a yellow or gold<br />
appearance. As the lesions mature <strong>and</strong> dry, the leaves appear scalded. Lesions from<br />
the edges o f leaf blades may have an indistinct mottled pattern. Affected leaves dry<br />
<strong>and</strong> turn straw-colored. The disease develops late in the season <strong>and</strong> is favored by high<br />
nitrogen fertilization.<br />
Panicle infestations cause a uniform light to dark, reddish-brown discoloration<br />
o f entire florets or the hulls o f developing grain. The disease can cause sterility or<br />
abortion o f developing kernels. T he disease has the potential to reduce yield <strong>and</strong> grain<br />
quality significantly, but lade o f epidemiological data <strong>and</strong> scouting methods limits<br />
control. Foliar applications o f fungicides are not recommended at this time.<br />
Leaf Smut. The fungus Entyloma oryzae Syd, & P. Syd causes leaf smut. Leaf smut<br />
is very com m on <strong>and</strong> is found in m ost rice-growing regions o f the world but causes<br />
little damage. The disease develops best under high nitrogen levels. The disease is<br />
characterized by slightly raised dark black rectangular to angular spots on both sides
428 Production<br />
o f the leaf blade <strong>and</strong> occasionally on leaf sheaths (Figure 3.5.19; see color insert). The<br />
spots are 0.5 to 5.0 m m long <strong>and</strong> 0.5 to 1.5 m m wide <strong>and</strong> are oriented parallel to the<br />
veins. Large numbers can be found on a single leaf, but they remain distinct from<br />
each other. The epidermis covers the lesion but ruptures when wet releasing the black<br />
spores. Severely infected leaves turn yellow, <strong>and</strong> the leaf tips, die <strong>and</strong> turn gray from<br />
desiccation. The fungus is spread by airborne spores <strong>and</strong> overwinters as teliospores in<br />
infected plant tissue.<br />
Leaf smut occurs late in the season <strong>and</strong> causes little damage. No control measures<br />
are recommended, but some cultivars have resistance. Broad-spectrum fungicides<br />
targeted at other diseases often reduce leaf smut (Groth et al., 1993).<br />
ii<br />
White Tip Nematode. The white tip nematode is com m on on rice in the United<br />
States but does not cause significant damage. This disease is caused by the nematode<br />
Aphelenchoides besseyi Christie. Characteristic symptoms include the yellowing o f leaf<br />
tips, white areas in portions o f the leaf blade, stunting o f affected plants, twisting or<br />
distortion o f the flag leaf, <strong>and</strong> distortion <strong>and</strong> discoloration of panicles <strong>and</strong> florets.<br />
The most com m on symptom is for leaf tips to become yellow, then white (Figure<br />
3.5.20; see color insert). The tip withers, becoming brown or tan, <strong>and</strong> tattered or<br />
twisted. Cultivars with more resistance may show few symptoms but still have reduced<br />
yield. The nematode infects the developing grain <strong>and</strong> is seedborne. Fumigation o f<br />
seeds in storage may reduce tlie nematode population. No specific control measure is<br />
recommended.<br />
White Leaf Streak. W hite leaf streak is caused by the fungus Mycouellosiella oryzae<br />
(Deighton & Shaw) Deighton. The disease is o f m inor importance. It is characterized<br />
by small, linear leaf lesions. As the name implies, lesions are white to light gray <strong>and</strong> are<br />
surrounded by a narrow brown margin. The disease is easily confused with narrow<br />
brown leaf spot. Little or no inform ation is available on its importance, epidemiology,<br />
or control measures.<br />
Head <strong>and</strong> Grain Diseases<br />
Peciiy <strong>Rice</strong>. Damage by many fungi, including Cochlioholus rniyabeanus (Ito & Kuribayashi)<br />
Drechs. ex. Dastur, Curvularia spp., Fusarium spp., M icrodochium oryzae<br />
(Hashioka & Yokogi) Samuels & I. C. Halett, Sarocladium oryzae (Sawada) W. Gams<br />
D. Hawlcsworth, <strong>and</strong> other fungi, causes spots <strong>and</strong> discoloration on the hulls or kernels.<br />
Damage by the rice stinkbug also causes discoloration o f the kernel. Kernels<br />
discolored by fungal infections or insect damage com m only are called peck. The grain<br />
has small to almost ah o f the endosperm rotted (Figure 3.5.21; see color insert). This<br />
is a complex disorder in rice with involvement o f many fungi, the white-tip nematode,<br />
<strong>and</strong> insect damage. High winds at the early heading stage may cause similar<br />
symptoms, Proper insect control <strong>and</strong> disease management will reduce this problem.<br />
False Smut. The fungus Ustilaginoidea virens (Cooke) Talcah causes false smut. The<br />
disease is characterized by large orange to brown-green spore balls on one or more<br />
grains in the panicle (Figure 3.5,22; see color insert). W hen the covering ruptures, a<br />
mass o f greenish-black spores is exposed. In the center o f the spore masses are one or
<strong>Rice</strong> Diseases 429<br />
more sclerotia. Several mycotoxins have been reported associated with the sclerotia,<br />
but recent studies on United States isolates were negative for toxin <strong>production</strong> (J. E.<br />
Street, personal com m unication). M ost cultivars appear to have good resistance to<br />
the disease. False smut is considered a m inor disease, <strong>and</strong> disease control measures<br />
are normally not required. Copper foliar sprays do have activity against the fungus.<br />
Kernel Smut. This fungal disease is caused by Tilletia harclayana (Bref.) Sacc. & Syd.<br />
in Sacc. = Neovossia hórrida (Takah.) Padw kk & A. Khan. Symptoms are observed<br />
at or shortly before maturity. A black mass o f smut spores replaces all or part o f the<br />
endosperm o f the grain. The disease is observed easily in the m orning as the smut<br />
spores absorb the dew. The spore mass exp<strong>and</strong>s <strong>and</strong> pushes out o f the hull, where it<br />
is visible as a black mass (Figure 3.5.23; see color insert). W hen this mass dries, it is<br />
powdery <strong>and</strong> is easily removed. Rain may wash the black spores over adjacent parts of<br />
the panicle. Compared with norm al grains, affected grains tend to have a lighter <strong>and</strong><br />
slightly grayish color.<br />
Usually, only a few florets may be affected in each panicle. However, fields have<br />
been observed with 20 to 40% o f the florets affected in 10% or more o f the panicles<br />
in a field. Smutted grains produce kernels with black strealcs or dark areas. Milled<br />
rice has a dull or grayish appearance when smutted grains are present in the sample.<br />
Because kernels becom e discolored when smutted rice is parboiled <strong>and</strong> milled, kernel<br />
smut can be a severe problem in processed rice. Growers may be docked in price for<br />
grain with a high incidence o f smut.<br />
This disease can become epidemic in local areas. Several cultivars are highly<br />
susceptible to this disease <strong>and</strong> should be avoided where smut is a problem. Spores<br />
o f the fungus are carried on affected seeds <strong>and</strong> also overwinter in the soil o f affected<br />
fields. The pathogen attacks immature developing grain <strong>and</strong> is m ore severe when<br />
rains are frequent during flowering. Cultivars vary in their susceptibility to kernel<br />
smut. Applications o f propaconzole at the boot growth stage has shown good control<br />
(Hornsby et al., 2000).<br />
Panicle Blight Panicle blight or grain blight was recently identified as being caused<br />
by the bacterium Burkholderia glumas {Pseudomonas glumas Kurita & Tabei) in the<br />
United States. The disease occurs worldwide <strong>and</strong> is referred to as bacterial grain rot in<br />
Japan. The bacterium is seedborne <strong>and</strong> can cause a seedling blight that thins st<strong>and</strong>s<br />
significantly. The bacteria appear to survive on the plant as an epiphytic population<br />
on the foliage <strong>and</strong> follow the canopy up. Initially, the pathogen was identified as a<br />
leaf epiphyte for use as a biocontrol agent for sheath blight. This population infects<br />
the grain at flowering <strong>and</strong> causes grain abortion <strong>and</strong> grain rotting soon after pollination.<br />
Sheath rotting also has been reported. Yield loss estimates vary from a trace to<br />
50% for both yield <strong>and</strong> quality. Initial symptoms of grain infection appear as a gray<br />
discoloration o f the glumes, which then turns tan (Figure 3.5.24; see color insert).<br />
Infected grains can be unevenly distributed on the panicle. In severe infections, all<br />
the seeds can be damaged. Diagnosis is difficult because other causes o f seed infection<br />
<strong>and</strong> sterility produce similar symptoms <strong>and</strong> mask panicle blight symptoms, especially<br />
after lesion maturity. Key diagnostic characteristics are that the stem stays green up<br />
to the seed <strong>and</strong> the presence o f a partially filled grain with an embryo that aborts<br />
after fertilization. A suberized layer develops between the stem <strong>and</strong> seed <strong>and</strong> reduces<br />
nutrient flow. Temperatures above 32°C (90®F) favor the disease. The disease usually
430 Production<br />
develops in a circular pattern in the field, with severely affected plants in the center <strong>and</strong><br />
less affected plants around the edge. Infected heads can be confused with straighthead<br />
because o f their upright stature. No parrot beaks are present.<br />
Seed treatments have shown some activity in reducing seedborne pathogen populations<br />
<strong>and</strong> subsequent head disease. Foliar sprays o f antibacterial compounds also<br />
show some promise. Some cultivars appear to be m ore susceptible than others.<br />
Minor Head <strong>and</strong> Grain Diseoses<br />
BlackKernel The fungus Curvularia lunata (Waldc.) Boedijn (teleomorph: Cochioholus<br />
lunatus R. R. Nelson & Haasis) <strong>and</strong> other species cause black kernel. These com <br />
m on seedborne fungi cause glume discoloration under severe infection <strong>and</strong> black<br />
discolored milled rice. The fungus can also cause seedling blights, weak seedlings, <strong>and</strong><br />
leaf spots. High humidity <strong>and</strong> warm weather favor disease development. This disease<br />
is rare, <strong>and</strong> management practices are not recommended. Seed treatments for st<strong>and</strong><br />
establishment may reduce seedling damage.<br />
Downy Mildew. The fungus Sclerophthora macrospora (Sacc.) Thirum alachar et al.<br />
causes downy mildew. The fungus has a wide host range <strong>and</strong> survives as oospores in<br />
soil <strong>and</strong> host debris. In early growth stages, infected seedlings are dwarfed <strong>and</strong> twisted<br />
with chlorotic yellow-to-whitish spots. Symptoms are more severe near heading. Because<br />
o f exertion problems, panicles are distorted, causing irregular, twisted heads<br />
that remain green longer than surrounding healthy heads. The disease is o f m inor<br />
importance <strong>and</strong> no control measures are warranted.<br />
lyUiil:.;:.<br />
Grain Discoloration. A large number o f weak fungal <strong>and</strong> bacterial pathogens cause<br />
grain discoloration. There are too many to list here, but symptoms include pale yellow,<br />
brown, gray, or black discoloration on glumes <strong>and</strong> kernels. Severity varies with location,<br />
environmental conditions, organism involved, <strong>and</strong> other factors. Grain quality<br />
can be reduced. Damage can occur in the field or in storage. In general, these are<br />
m inor problems of rice, causing little damage. Fungicidal sprays can reduce severity<br />
<strong>and</strong> incidence. Correct postharvest conditioning <strong>and</strong> storage will prevent grain discoloration.<br />
Viral <strong>and</strong> Mycoplasma-like Diseases<br />
There are several im portant viral <strong>and</strong> mycoplasma-like diseases o f rice. None of these<br />
diseases are present in the United States at the present time. Early in the 1960s, Hoja<br />
Blanca <strong>and</strong> its insect vector were present in the southern United States, but the disease<br />
has disappeared. These diseases have becom e more im portant since the start o f the<br />
Green Revolution, with its intensive management, especially in the tropics. None<br />
o f the rice viral diseases are seed transmitted. M ost viruses are insect vectored by<br />
leafhoppers <strong>and</strong> planthoppers. Other vectors include fungi <strong>and</strong> soil. Control o f these<br />
diseases is difficult <strong>and</strong> often involves control o f their vectors. Resistance to insecticides<br />
caused by overuse makes vector control even m ore difficult. In warm areas, these<br />
vectors can be active year round, <strong>and</strong> multiple continuous cropping in an area, in conjunction<br />
with weed reservoirs, can make control difficult. Identification can also be
^ice Diseases 431<br />
difficult because o f similar symptoms, multiple infections, <strong>and</strong> confusion with other<br />
diseases <strong>and</strong> physiological disorders. Damage is more severe if plants are infected<br />
early. Symptoms range from mosaics to dwarfing <strong>and</strong> from chlorosis to necrosis. A<br />
comprehensive coveraige o f these diseases is beyond the scope of this chapter, <strong>and</strong><br />
readers are encouraged to obtain additional inform ation from other sources if a viral<br />
disease is suspected. Several good references <strong>and</strong> overviews are available (Ou, 1985;<br />
Webster <strong>and</strong> Gunnell, 1992; Hibino, 1996; Abo <strong>and</strong> Sy, 1998).<br />
Nematodes<br />
Other than the white tip nematode, the United States does not have any significant nematode<br />
diseases. The m ost damaging nematode is the stem nematode disease, which<br />
is associated with or near deepwater rice in Asia. Symptoms usually include m alformation,<br />
scattered dark-stained areas on leaves <strong>and</strong> stem, <strong>and</strong> deformation o f the<br />
head. Control includes crop rotation, cultural control, <strong>and</strong> burning crop debris. Some<br />
cultivars show resistance, <strong>and</strong> nematicides can control the disease but are expensive.<br />
Other than the white tip nematode, none o f the rice nematodes are seed transmitted.<br />
An excellent review o f nematode diseases o f rice by McGawley <strong>and</strong> Overstreet (1998)<br />
is available.<br />
Bacterial Diseases<br />
There are several other bacterial diseases o f rice present in other parts o f the world.<br />
Many o f them affect flag leaf sheaths <strong>and</strong> grain. These are often seed-transmitted<br />
<strong>and</strong> represent a significant threat to U.S. rice <strong>production</strong> if introduced. Continued<br />
vigilance through effective plant quarantine procedures is necessary. Additional information<br />
is available on these diseases in the <strong>Rice</strong> Diseases book by Ou (1985) <strong>and</strong><br />
tlie Compendium of <strong>Rice</strong> Diseases edited by Webster <strong>and</strong> Gunnell (1992).<br />
Miscellaneous Diseases or Physiological Disorders<br />
Alkalinity or Salt Damage. Excessive salt concentration in soil or water can injure<br />
rice. Stunted yellow plants characterize the symptoms. Under severe conditions, leaves<br />
turn from yellow to white <strong>and</strong> plants die. Affected areas usually have dead or dying<br />
plants in the center or on high spots, witli stunted yellow or white plants surrounding<br />
them, <strong>and</strong> green, less affected plants in lower areas. Salt deposits may be seen on the<br />
edges o f leaves, on clods o f soU, <strong>and</strong> in other high areas o f the field. Flushing the field<br />
with fresh water is the only control method.<br />
Bronzing. Bronzing is caused by zinc deficiency <strong>and</strong> is normally associated with cooler<br />
weather. Purple-brown blotches made up o f small spots coalescing on leaf blades<br />
characterize this disorder. Leaves become yellow, orange, or bronze. W hite patches<br />
may form on leaves, lower leaves float on the surface o f floodwater, <strong>and</strong> seedlings die.<br />
O n older plants, the lower leaves die <strong>and</strong> disappear below the water surface, plants<br />
m aybe stunted, <strong>and</strong> florets m aybe discolored. Damage from foliar copper sprays can
432 Production<br />
resemble bronzing. This disorder is controlled by adding zinc to seeds, to soil preplant,<br />
or by spraying plants with chelated zinc. Draining the field also encourages recovery.<br />
If untreated, rice will continue to die until weather conditions warm.<br />
Cold Injuiy. Cold weather may affect rice development at the seedling or heading<br />
stages o f growth. Seedling damage is expressed as a general yellowing o f the plants<br />
or as yellow-to-white b<strong>and</strong>s across the leaves, where a com bination o f wind <strong>and</strong> low<br />
temperature damaged the plants at the soil line. Cold weather (
<strong>Rice</strong> Diseases 433<br />
The direct im portation o f rice seed for planting or rice plant parts for other reasons<br />
from other regions is illegal <strong>and</strong> should be avoided. Along with the im portation o f the<br />
pathogen, the introduction o f the vector o f viral diseases could pose a great risk.<br />
Cultural Practices<br />
Since most rice diseases are dependent on moisture in the canopy, cultural practices<br />
that increase canopy thiclmess encourage disease development. Plant st<strong>and</strong> <strong>and</strong> nitrogen<br />
fertilization are the two most im portant contributing factors to canopy thickness<br />
but also contribute to yield potential. In light o f this, many cultural management<br />
practices may be ineffective, impractical, or counterproductive to maximizing yield<br />
<strong>and</strong> quality. Crop rotation often reduces the inoculum survival rate. Inoculum from<br />
adjacent fields planted earlier or weedy areas can be avoided by selecting planting date<br />
<strong>and</strong> location carefully. Burning or bailing straw after harvest can reduce inoculum.<br />
Weeds also act as an overwintering site for pathogens <strong>and</strong> should be destroyed.<br />
W ith the advent o f new, m ore effective fungicides, many rice producers have been<br />
interested in increasing the N rate to increase yields without suffering the devastating<br />
effect o f increased diseases. In trials o f the N rate by fungicide use, increasing the<br />
N rate increased disease pressure, but fungicide efficiency was reduced (Groth <strong>and</strong><br />
Bollich, 2000), Yields maximized at recommended N rates <strong>and</strong> did not increase or<br />
decrease at excessive N rates even in the presence o f fungicides.<br />
Host Resistance<br />
Host resistance is the m ost im portant control m ethod available to rice producers. U n<br />
fortunately, resistance is not available to all diseases, <strong>and</strong> too often, available resistance<br />
breaks down, because o f the development o f new races o f the pathogen. This has been<br />
observed by the increase in blast <strong>and</strong> other foliar diseases as specific cultivars experience<br />
increased hectarage <strong>and</strong> also the longer that they are grown. New technologies<br />
offer new hope in developing resistance in rice. Incorporation o f antifungal genes<br />
into the rice genome through bio<strong>technology</strong> offers great promise. Pyramiding genes<br />
based on genetic makeup o f the pathogen population also offers new ways to deploy<br />
resistance genes.<br />
Chemical Control<br />
Often, rice producers must rely on chemical control to protect their crop. This is a<br />
last option, because o f the expense, environmental concerns, <strong>and</strong> limited effectiveness.<br />
Determining the need for fungicide sprays by scouting is an effective way to<br />
use fungicides when diey are needed <strong>and</strong> before the disease gets out o f control. In<br />
determining which fungicide to use, scouting is also extremely im portant in determining<br />
disease incidence <strong>and</strong> severity. Early season sheath blight severity is often a<br />
predictor o f late-season severity <strong>and</strong> yield loss. O ther diseases do not have prediction<br />
systems <strong>and</strong> scouting methods for spraying. The econom ics o f disease control are also<br />
im portant since yield <strong>and</strong> milling increases are im portant to receiving a significant<br />
t:i!-
434 Production<br />
:n<br />
il<br />
l i ,<br />
iliil<br />
return. The farmer must consider cost, projected increase yield, quality, <strong>and</strong> improved<br />
harvestablity. In some cases, fungicide applications are not justified. Salvage sprays<br />
after significant damage occurs usually do not produce the yield increases since tissue<br />
is already killed <strong>and</strong> yield potential reduced. Several factors affect fungicide efficacy,<br />
including application timing, weather, cultural management, spray volume, type of<br />
adjuvant added to the spray solution, <strong>and</strong> the application method used. Other factors<br />
that reduce efficiency are drift, volatility, <strong>and</strong> calibration errors. Seed treatments <strong>and</strong><br />
planter box applications of fungicides <strong>and</strong>/or antibiotics can reduce initial inoculum<br />
<strong>and</strong> postpone the onset o f disease in the field.<br />
Biological Control<br />
Biological control uses hyperparasites, competitive microorganisms, <strong>and</strong> antibioticproducing<br />
microorganisms to restrict or reduce populations o f a pathogen. Little<br />
information is available on biological control o f rice diseases, <strong>and</strong> few systems are<br />
developed. Systems using yeast as a biological control system have been evaluated <strong>and</strong><br />
initial results are encouraging (Shahjahan et al., 1998). Although underdeveloped, the<br />
techniques offer great promise to control both the pathogens <strong>and</strong> their vectors.<br />
CONCLUSIONS<br />
ijii ^<br />
<strong>Rice</strong> diseases can be managed if an integrated method o f control is used. Selection of<br />
the most resistant commercially acceptable cultivar is the first step. Keeping in contact<br />
with local specialists who are familiar with the diseases in the area is important.<br />
Scouting fields <strong>and</strong> correct identification of diseases are critical. Tim ely application of<br />
tlie correct control agent maximizes returns. Crop rotation usually reduces inoculum<br />
in the soil <strong>and</strong> disease development.<br />
¡M. ¡:<br />
ílí<br />
my:- ■<br />
iíí;l: !<br />
REFERENCES<br />
Abo, M. E., <strong>and</strong> A. A. Sy. 1998. <strong>Rice</strong> virus diseases: epidemiology <strong>and</strong> management<br />
strategies. /. Sustain. Agríe. 11:113-134.<br />
Anonymous, 1999. Louisiana <strong>Rice</strong> Production H<strong>and</strong>book. La. State Univ. Agrie. Center<br />
Publ. 2321, revised.<br />
Boyd, V. 2000. Use clean seed to avoid “foolish seedling” disease. <strong>Rice</strong> Farm. 35:28.<br />
Cartwright, R. D,, <strong>and</strong> F. N. Lee. 2001. Management of rice diseases. In N. S. Slaton<br />
(ed.). <strong>Rice</strong> Production H<strong>and</strong>book. M P192 Rev. Ark. Coop. Ext. Ser., pp. 87-120.<br />
Chun, S. C., <strong>and</strong> R. W. Schneider. 1998. Sites of infection by Pythium species in<br />
rice seedlings <strong>and</strong> effects of plant age <strong>and</strong> water depth on disease development.<br />
Phytopathology 88:1255-1261.<br />
Datnoff, L. E., C. W. Deren, <strong>and</strong> G, H. Snyder. 1997. Silicon fertilization for disease<br />
management o f rice in Florida. Crop Prot. 16:525-531.<br />
Gangopadhyay, S., <strong>and</strong> N. K. Chakrabarti. 1982. Sheath blight o f rice. Rev. Plant<br />
Pathol. 61:451-460.
Ríce Diseases 435<br />
Giesler, G. G., A. M . Heagler, <strong>and</strong> D. E. Groth. 1994. Econom ic analysis of fungicide<br />
use in rice <strong>production</strong>. La. Agrie. 37:20-22,<br />
Goto, M. 1979. Bacterial foot rot o f rice caused by a strain o f Erwinia chrysanthemi.<br />
Phytopathology 69:213-216.<br />
Greer, C. A., <strong>and</strong> R. K. Webster. 2000, Introduction <strong>and</strong> spread o f Pyricularia grísea<br />
<strong>and</strong> rice blast disease in California. Proc. Rke Tech. Work Group 28:86-87<br />
Grotli, D. E. 1996. Two new fungicides to control rice diseases. La. Agrie. 39:31-33.<br />
Groth, D. E. 2001, Tim ing <strong>and</strong> rate are keys to rice fungicide performance. La. Agri<br />
In press.<br />
Groth, D. E., <strong>and</strong> R K. Bollich. 2000. The effects o f nitrogen rate <strong>and</strong> fungicide application<br />
on disease development <strong>and</strong> yield o f rice. Proc. <strong>Rice</strong> Tech. Work Group<br />
28:81-82.<br />
Groth, D. E., <strong>and</strong> C. A. Hollier. 1986. A survey o f rice diseases in Louisiana. La. Agrie.<br />
29:10-12.<br />
Groth, D. E., M. C. Rush, <strong>and</strong> C. A, Hollier. 1991. <strong>Rice</strong> Diseases <strong>and</strong> Disorders In<br />
Louisiana. La. Agrie. Exp. Stn. Bull. 828, 37 pp.<br />
Groth, D. E., M , C. Rush, <strong>and</strong> C. A. Hollier. 1992. Prediction o f rice sheatli blight<br />
severity <strong>and</strong> yield loss based on early season infection. La. Agrie. 35:20-23,<br />
Groth, D. E., M . C. Rush, G. G. Giesler,'<strong>and</strong> C. A. Hollier. 1993. Foliar Fungicides for<br />
Use in the Management of <strong>Rice</strong> Diseases. La. Agrie. Exp. Stn. Bull. 8 4 0 ,4 4 pp.<br />
Hibino, H. 1996. Biology <strong>and</strong> epidemiology of rice vh'uses. Annu. Rev. Phytopathol<br />
34:249-274.<br />
Hornsby, Q., R. D. Cartwright, C, Hyden, S. Vann, E. A. Sutton, <strong>and</strong> K. Driggs. 2000,<br />
Management o f kernel smut o f rice with fungicides in Arkansas, Proc. <strong>Rice</strong> Tech.<br />
Work Group 28:84,<br />
Lee, F. N., <strong>and</strong> M. C. Rush. 1983, <strong>Rice</strong> sheath blight: a m ajor rice disease. Plant Dis.<br />
67:829-832.<br />
M archetti, M . A. 1983, Potential impact of sheath blight on rice yield <strong>and</strong> milling quality<br />
o f short statured rice lines in the southern United States. Plant Dis. 6 7 :1 6 2 -<br />
165.<br />
McGawley, E. C., <strong>and</strong> C. Overstreet. 1998. <strong>Rice</strong> <strong>and</strong> other cereals. In Plant <strong>and</strong> Nematode<br />
Interactions. Agron. Monogr. 36, pp. 455-486.<br />
Mew, T. W., <strong>and</strong> J. K. Misra. 1994. A Manual o f <strong>Rice</strong> Seed Health Testing. International<br />
<strong>Rice</strong> Research Institute, Manila, The Philippines, 113 pp.<br />
Ou, S. H. 1985, <strong>Rice</strong> Diseases, 2nd ed. Commonwealth Mycological Institute, Kew,<br />
Surrey, Engl<strong>and</strong>, 198 pp.<br />
Pan, X. B., M . C. Rush, X. Y. Sha, Q. J. Xie, S. D, Linscombe, S. R. Statina, <strong>and</strong> J. H.<br />
Oard. 1999. M ajor gene, nonallelic sheath blight resistance from the rice cultivars<br />
Jasmine 85 <strong>and</strong> Teqing. Crop Sei 39:338-346.<br />
Rush, M. C„ <strong>and</strong> R. W. Schneider. 1990. Chemical control o f seedling diseases o f<br />
rice in Louisiana. In B. T. Grayson, M. B. Green, <strong>and</strong> L. G. Copping (eds.). Pest<br />
Management in <strong>Rice</strong>. Elsevier Science, London, pp. 53-70.<br />
Savary, S., L. W illocquet, <strong>and</strong> P. S. Teng. 1997. Modeling sheath blight epidemics on<br />
rice tillers. Agrie. Syst. 55:359-384.<br />
Savary, S., L, W illocquet, F. A. Elazegui, N. P. Castilla, <strong>and</strong> P. S. Teng. 2000. <strong>Rice</strong> pest<br />
constraints in tropical Asia: quantification o f yield losses due to rice pests in a<br />
range o f <strong>production</strong> situations. Plant Dis. 84:357-369.
436 Production<br />
It',:; i<br />
Shahjahan, A. K. M ., <strong>and</strong> T. W, Mew. 1989. Analysis o f rice sheath blight (Rhizoctonia<br />
solani) development under tropical condition. Bangladesh J. Plant Pathol. 5 :4 7 -<br />
52.<br />
Shahjahan, A. K. M ., Z. Harahap, <strong>and</strong> M. C. Rush. 1977. Sheath rot o f rice caused by<br />
Acrocylindrium oryzae in Louisiana. Plant Dis. Rep, 61:307-310.<br />
Shahjahan, A. K. M ., M . C. Rush, J. P. Jones, <strong>and</strong> D. E. Groth. 2001, Phylloplane yeasts<br />
as potential biocontrol agents for rice sheath blight disease. In S. Sreenivasprasad<br />
<strong>and</strong> R. Johnson (eds,), Major Fungal Diseases of <strong>Rice</strong>, Kluwer Academic, D ordrecht,<br />
The Netherl<strong>and</strong>s.<br />
Shanmughon, S. N., N. Gopalar, K. M. George, <strong>and</strong> R. Gopaiakuishnan. 1973. Leaf<br />
scald o f rice. Curr. Sei. 42:582-563.<br />
Singh, R., <strong>and</strong> D. S. Dodan, 1995. Sheath rot o f rice. Int. J. Trop. Plant Dis. 13:139-152.<br />
Van Eeckhout, E., M. C. Rush, <strong>and</strong> M. Blackwell. 1991. Effects o f rate <strong>and</strong> tim ing o f<br />
fungicide applications on incidence <strong>and</strong> severity o f sheath blight <strong>and</strong> grain yield<br />
o f rice. Plant Dis. 75:1254-1261.<br />
Webster, R. K., <strong>and</strong>P, S. Gunnell (eds.). 1992. Compendium of <strong>Rice</strong> Diseases. APS Press,<br />
St. Paul, M N, 62 pp. ,
Chopter<br />
3.6<br />
Ríce Arthropod Pests <strong>and</strong> Their<br />
Management in the United States<br />
M . 0. W ay<br />
Texas Agricultural Experiment Station<br />
Beaumont, Texas<br />
INTRODUCTION<br />
RICE WATER WEEVIL<br />
RICE STINK BUG<br />
ARMYWORMS<br />
CHINCH BUG<br />
RICE SEED MIDGES<br />
RICE LEAF MINER<br />
RICE STEM BORERS<br />
LEAFHOPPERS<br />
GRAPE COLASPIS<br />
TADPOLE SHRIMP<br />
CRAYFISH<br />
ROLE OF RICE ENTOMOLOGISTS IN THE UNITED STATES<br />
ACKNOWLEDGMENTS<br />
REFERENCES<br />
INTRODUCTiON<br />
Arthropods damage rice from planting to harvest in the United States, where rice is<br />
produced on about 1.5 million hectares in Arkansas, California, Florida, Louisiana,<br />
Mississippi, M issouri, <strong>and</strong> Texas (Anonymous, 2000). Each state has a unique com <br />
plex o f arthropods associated witli rice <strong>production</strong>. The occurrence, abundance, <strong>and</strong><br />
damage of these pest complexes are driven largely by regional differences in climate,<br />
topography, soil, <strong>and</strong> <strong>production</strong> practices. Generally, rice pests <strong>and</strong> <strong>production</strong><br />
<strong>Rice</strong>: Origin, History, Technology, <strong>and</strong> Production, edited by C. Wayne <strong>Smith</strong><br />
ISBN 0-471-34516-4 © <strong>2003</strong> John Wiley & Sons, Inc.<br />
437
438 Production<br />
practices differ more between the southern states <strong>and</strong> California than within the<br />
southern states. For instance, in California, rice is water-planted <strong>and</strong> continuously<br />
flooded, whereas in the m ajority o f the southern states, rice is dry-planted <strong>and</strong> flush-<br />
irrigated periodically until a perm anent flood is applied during the tillering stage<br />
o f rice development (Rutger <strong>and</strong> Br<strong>and</strong>on, 1981; Helms, 1988; Klosterboer <strong>and</strong> M c<br />
Cauley, 2001). The exception in the south is southwestern Louisiana, where rice fields<br />
are water-planted, then drained for 3 to 5 days to encourage seedlings to take root in<br />
the mud, <strong>and</strong> reflooded (Linscombe et al., 1999). This is known as pinpoint flooding.<br />
Water management is probably the most im portant <strong>production</strong> practice in terras of<br />
influencing rice pest populations <strong>and</strong> damage. O ther <strong>production</strong> practices that also<br />
affect occurrence <strong>and</strong> severity o f rice arthropods are l<strong>and</strong> preparation, varietal selection,<br />
planting date, fertility, herbicide <strong>and</strong> fungicide programs, <strong>and</strong> ratoon cropping.<br />
The most com m on arthropod pests in the United States are listed in Table 3.6.1.<br />
O f these pests, the rice water weevil (RW W ) <strong>and</strong> rice stink bug (RSB) are the most<br />
ubiquitous <strong>and</strong> serious (Way, 1990). RWWs <strong>and</strong> RSBs can be found in virtually every<br />
rice field <strong>and</strong> year in the United States <strong>and</strong> the south, respectively (RSB occurs only<br />
in the south) ,(Grigarick, 1984). On average, U.S. rice farmers spend more to control<br />
these two pests than any other arthropod. Thus U.S. rice entomologists devote most<br />
o f their research <strong>and</strong> extension activities to these pests. The remaining pests in Table<br />
3.6.Lean be very serious in certain years, states, <strong>and</strong>/or counties within states. Reasons<br />
for the erratic severity o f these secondary pest problems can be due to differences in<br />
localized <strong>production</strong> practices, extension of the range o f a pest (see the discussion<br />
o f the Mexican rice borer in the rice stem borer section), deviations from norm al<br />
climatic conditions (e.g., warmer <strong>and</strong> drier than norm al winters <strong>and</strong> early springs),<br />
<strong>and</strong> poor management decisions based on failure to detect a pest before econom ic<br />
damage occurs. <strong>Rice</strong> farmers must scout fields carefully <strong>and</strong> frequently from planting<br />
to harvest to guard against econom ic damage by the complex o f pests unique to their<br />
specific agroecosystem. In addition, changes in governmental regulations can have<br />
a profound impact on pest problems <strong>and</strong> associated management practices. These<br />
issues will be examined in more detail as tliey relate to the following discussion o f<br />
arthropod pests of U.S. rice.<br />
RICE WATER WEEVIL<br />
The RWW occurs in all rice-produdng states <strong>and</strong> is endemic to the southeastern<br />
United States (Grigarick, 1984). The insect was introduced from the south into California<br />
in the 1950s <strong>and</strong> has since spread to Asia (Lange <strong>and</strong> Grigarick, 1959; Tsuzuki<br />
<strong>and</strong> Isogawa, 1976). Only females occur in California, so re<strong>production</strong> is by parthenogenesis<br />
in California (Grigarick <strong>and</strong> Beards, 1965). Both sexes occur in the south.<br />
RWWs overwinter as adults in perennial grasses <strong>and</strong> litter surrounding rice fields.<br />
The overwintering insect enters into diapause, whose specific environmental triggers<br />
are unknown (Knabke, 1973), During overwintering, adult indirect wing muscles<br />
degenerate <strong>and</strong> ovaries remain undeveloped (Muda et al., 1981; Morgan et al., 1984).<br />
In the early spring, adults begin feeding on the new foliage of overwintering hosts<br />
<strong>and</strong> other grasses. At this time, indirect wing muscles are regenerated <strong>and</strong> ovaries<br />
begin developing. Once wing muscles are developed, insects begin flying in search o f<br />
suitable ovipositional conditions <strong>and</strong> hosts. Adults feed on rice foliage <strong>and</strong> produce
<strong>Rice</strong> Arthropod Pests <strong>and</strong> Their M anagem ent in the United States 439<br />
TABLE 3.6.1.<br />
Common Arthropod Pests of <strong>Rice</strong> in the United States<br />
Scientific Name Common Name Damaging Stage Plant Part Attacked Occurrence<br />
Lissorhoptrus oryzophilus<br />
Kuschel<br />
<strong>Rice</strong> water<br />
weevil<br />
Larva Roots All rice-producing states<br />
Oehalus pugnax (F.) <strong>Rice</strong> stink bug Nymph/adult Grains on panicles Southern rice-producing<br />
states<br />
Spodoptera frugiperda<br />
(J. E. <strong>Smith</strong>)<br />
Pseudaletia unipuncta<br />
(Haworth)<br />
Blisstis leucopterus<br />
ieucopterus (Say)<br />
Genera<br />
CncofopMs<br />
Paratanytarsus<br />
Paralauterhornieila<br />
Tanytamis<br />
Chironomus<br />
Hydrellia griseola<br />
(Fallen)<br />
Diatraea saccharalis (P,)<br />
Chilo plejadellus<br />
Zincken<br />
Eoreuma loftini (Dyar)<br />
Macrostdes fascifrons<br />
(stai.)<br />
GramineUa nigrifrons<br />
(Forbes)<br />
Fall armyworm<br />
Larva Foliage Southern rice-produemg<br />
states<br />
Arniyworm Larva FoUage/panicles California<br />
Chinch bug Nymph/adult Stems, foliage,<br />
roots, <strong>and</strong><br />
panicles<br />
<strong>Rice</strong> seed<br />
midges<br />
<strong>Rice</strong> leaf<br />
miner<br />
Sugarcane<br />
borer<br />
<strong>Rice</strong> stalk<br />
borer<br />
Mexican rice<br />
borer<br />
Aster leafhopper<br />
Blackfaced<br />
leafhopper<br />
Larva<br />
Germinating<br />
seeds, young<br />
roots <strong>and</strong><br />
shoots<br />
Southern rice-producing<br />
states<br />
<strong>Rice</strong>-producing states<br />
where rice is<br />
water-planted <strong>and</strong><br />
continuously or<br />
pinpoint flooded<br />
Larva Foliage All rice produemg states<br />
Larva<br />
Larva<br />
Larva<br />
Stems, foliage, leaf<br />
sheadis, <strong>and</strong><br />
panicles<br />
Stems, foliage, leaf<br />
sheaths, <strong>and</strong><br />
panicles<br />
Stems, foliage, leaf<br />
sheaths, <strong>and</strong><br />
panicles<br />
Southern rtce-producing<br />
states<br />
Southern rice-producing<br />
states<br />
Texas<br />
Nymph/adult Foliage California<br />
Nymph/adult Foliage Southern rice-producing<br />
states<br />
Colaspts brunnea (F.) Grape colaspis Larva Roots Southern rice-producing<br />
states (particularly<br />
Arkansas)<br />
TFiops hngicaudatus<br />
(LeConte)<br />
Procambarus clarki<br />
(Girard)<br />
Tadpole<br />
shrimp<br />
Crayfish<br />
Larva/adult<br />
Immature/<br />
adult<br />
Germinating<br />
seeds, young<br />
roots <strong>and</strong><br />
shoots<br />
Germinating<br />
seeds, young<br />
roots <strong>and</strong><br />
shoots<br />
California<br />
California
440 Production<br />
longitudinal feeding scars. Once a flood is established, females lay eggs in culms<br />
underwater. Eggs hatch <strong>and</strong> larvae move down to the roots, where feeding causes root<br />
pruning, which leads to yield losses. Larvae pass through four instars before pupating<br />
in mud cocoons attached to rice roots (Cave <strong>and</strong> <strong>Smith</strong>, 1983). In California <strong>and</strong><br />
Arkansas, only a single generation is produced annually, whereas in the remaining<br />
states (which are located in more southern latitudes), two or three generations occur<br />
in a year. Flowever, the generation produced by overwintering females typicaEy causes<br />
the greatest damage.<br />
Damage caused by larval root pruning includes stunting <strong>and</strong> chlorosis. Fewer<br />
tillers are produced by damaged versus undamaged plants, In addition, damaged<br />
plants are less competitive, which allows for greater weed growth. In California, highest<br />
RW W populations <strong>and</strong> m ost severe damage occur near levee <strong>and</strong> field margins;<br />
thus California rice farmers frequently apply insecticides only to the margins <strong>and</strong><br />
adjacent to levees o f their rice fields (Grigarick, 1970). However, in the south, RW W<br />
populations <strong>and</strong> damage are distributed m ore uniformly throughout rice fields (Way<br />
<strong>and</strong> Wallace, 1984). Damage by RWWs can result in substantial yield reductions. The<br />
U.S. Department o f Agricplture (USDA) estimated that an average range in yield loss<br />
between 10 <strong>and</strong> 33% would occur across the United States if the RW W s were left<br />
uncontrolled (Way <strong>and</strong> Bowling, 1991). In some areas <strong>and</strong> years, yield reductions are<br />
much greater. Also, the econom ic injury level (EIL) varies across states. For instance,<br />
in Texas the EIL is only five larvae per plant, whereas in Arkansas the EIL is about<br />
10 per plant (Johnson <strong>and</strong> Bernhardt 1988; Way, 2001), Data from Texas show that<br />
an average o f one larva per plant reduces yield by 90 kg/ha (Sundarapather, 1994).<br />
This is a linear relation. In addition, given this same RW W density, a carryover effect<br />
o f 22 kg/ha occurs on the ratoon crop, which is a second crop produced from main<br />
crop stubble. Ratoon rice is produced in Texas, Louisiana, <strong>and</strong> Florida, where a longer<br />
growing season allows for both main <strong>and</strong> ratoon crops.<br />
Management options for RW W have changed dramatically over the last several<br />
years, mainly due to changes in governmental regulatory policies. In the late<br />
1980s, the U.S. Environmental Protection Agency began a gradual phase-out o f the<br />
only RWW-labeled insecticide granular carbofuran (U.S. Environmental Protection<br />
Agency, 1989), Withdrawal was due to avian ld.Il incidents attributed to use <strong>and</strong> misuse<br />
of granular carbofuran (Flickinger et al., 1980; Littrell, 1988). This insecticide was<br />
applied to control the larval stages of RW W s, so in dry-plan ted, delay-flooded rice<br />
in Texas, granular carbofuran was applied 7 to 14 days after the permanent flood to<br />
coincide with the occurrence o f early instar larvae (Drees <strong>and</strong> Way, 1998). Econom ic<br />
thresholds (ETs) were established <strong>and</strong> based on adult RW W feeding scar densities. In<br />
other words, farmers/consultants would inspect rice foliage for feeding scars about 1<br />
week after the permanent flood. If scar densities exceeded the ET, granular carbofuran<br />
would be applied aerially between 7 <strong>and</strong> 14 days after the permanent flood.<br />
During the phase-out o f granular carbofuran, U.S. rice entomologists, the U.S.<br />
rice industry, <strong>and</strong> various agrichemical companies worked cooperatively to develop<br />
<strong>and</strong> evaluate novel insecticides as replacements for granular carbofuran. So by the<br />
spring o f 1999, A.-cyhalothrin, fipronil, <strong>and</strong> diflubenzuron were labeled as replacements<br />
for granular carbofuran (Way, 2001). Stout et al. (2000) reported tirât all three<br />
alternatives were more effective tlian granular carbofuran at preventing early RW W<br />
larval infestation o f rice roots.<br />
À-Cyhalothrin is formulated as a liquid <strong>and</strong> applied aerially soon after application<br />
o f the permanent flood when female RWWs begin oviposition. In Texas, recent
'" 1<br />
<strong>Rice</strong> Arthropod Pests tind Their Mqnagemeni in the UnitGd States 441<br />
research has shown that A,-cyhalothrin is most effective when applied from about 5<br />
days before to 5 days after application o f the permanent flood (Way <strong>and</strong> Wallace,<br />
1995a, 1996a, 1997a, 1998a, 1999a; Way et al., 1998). In fact, many Texas rice farmers<br />
now tank-m ix A-cyhalothrin with herbicides <strong>and</strong> apply just prior to tlie permanent<br />
flood (Way <strong>and</strong> Wallace, 1999b), By doing this, farmers save on aerial application<br />
charges.<br />
Fipronil is labeled as a seed treatm ent <strong>and</strong> targets larval RWW; thus fipronil is<br />
a truly preventive treatment. However, prior to obtaining a fipronil label, studies in<br />
Arkansas <strong>and</strong> Texas showed that fipronil was also effective applied preplant incorporated<br />
<strong>and</strong> just before the perm anent flood (Bernhardt 1995a,b, 1996, 1997; Way<br />
<strong>and</strong> Wallace 1995b, 1996b, 1997b). Applications after the perm anent flood were not<br />
as effective (Way <strong>and</strong> Wallace, 1997c). Currently, fipronil can be applied to dry or<br />
pregerminated seed <strong>and</strong> planted in a delayed, continuous, or pinpoint flood culture<br />
(Anonymous, 2001).<br />
Diflubenzuron is applied aerially as a liquid soon after appUcation o f the permanent<br />
flood. Sm ith et al. (1985) in greenhouse studies in California applied diflubenzuron<br />
to rice foliage or water before or after RW W oviposition. They concluded that<br />
diflubenzuron controlled RW W by reducing the number o f viable eggs developing<br />
in females or in plants following oviposition. However, no effect was observed on<br />
eggs exposed to diflubenzuron 5 days or longer after oviposition. Thus diflubenzuron<br />
affected eggs only during early development. In addition, no larval stages were affected<br />
by the applications. S<strong>and</strong>berg et al. (2000) confirmed these results in water-planted<br />
fields in California. They applied diflubenzuron at various times after rice emergence<br />
through water <strong>and</strong> found that the best time was approximately 5 days after 50%<br />
emergence. Diflubenzuron application timing studies were conducted in the field in<br />
Texas (Way <strong>and</strong> Wallace, 1996c, 1998b; Way et al., 1997). Applications before perm<br />
anent flood were not as effective as applications 2 to 3 days after permanent flood.<br />
Applications 11 days after permanent flood were ineffective. Thus regardless o f water<br />
management or rice-producing state, diflubenzuron should be applied soon after the<br />
perm anent flood when female RW W s are ovipositing but before eggs hatch.<br />
Because current labeled insecticides are applied m uch earlier than the recom <br />
mended tim e for previously registered granular carbofuran, no ETs are established<br />
for these novel insecticides. However, research in Arkansas has shown promising<br />
preliminary results using an aquatic barrier trap for adult RWWs (Hix et al., 2000).<br />
This trap is deployed soon after the permanent flood. Adult densities in traps are<br />
correlated to subsequent larval densities.<br />
Cultural controls for RWWs exist, m ost o f which involve manipulation o f irrigation<br />
practices. Draining fields to kill larvae is still practiced on a limited scale in<br />
the south. Thom pson et al. (1994a) compared the costs/benefits o f draining flooded<br />
paddies versus application o f insecticide to control RW W s in Louisiana. They found<br />
that drainage for at least 2 weeks before reflooding significantly reduced RW W larval<br />
populations. However, nutrient loss, possible rainfall during the drying period, <strong>and</strong><br />
potential reinvasion o f reflooded rice by RW W precluded recommending this cultural<br />
control tactic. Morgan et al. (1989) generated similar results in Arkansas, where field<br />
drainage for 7 to 13 days, beginning 10 days after the permanent flood, reduced<br />
RW W larval densities comparable to the insecticide treatment. Yet the econom ic costs<br />
associated with drainage were more tlian the cost o f the insecticide. Hesler et al.<br />
(1992) also investigated the effects of draining on RWWs in California. <strong>Rice</strong> grown<br />
in the greenhouse was transplanted into flooded or subsequently drained field plots.
Ihii;<br />
442 Production<br />
i'i.i ■<br />
r - ' :<br />
Oviposition was greater in flooded conditions, but egg survival was similar in flooded<br />
or drained conditions (plots were drained for up to 10 days). Again, draining fields<br />
for RW W control was not feasible because o f increased water costs, prom otion o f<br />
weed growth, reduction in nutrient availability, governmental prohibition o f field<br />
drainage for at least 3 weeks after herbicide application, <strong>and</strong> delay o f introduction<br />
o f mosquito fish.<br />
Sparse rice st<strong>and</strong>s are usually associated with more RW W damage. Thom pson<br />
<strong>and</strong> Quisenberry ( 1995) detected more RW W eggs per plant at lower rice plant densities<br />
but more eggs per unit ar'ea at higher densities. They concluded that manipulating<br />
plant st<strong>and</strong>s did not ameliorate RW W damage. Farmers can help ensure an adequate<br />
st<strong>and</strong> o f rice by increasing seeding rate, drill-planting at the optim um time, <strong>and</strong><br />
treating seed witlr fungicides <strong>and</strong> gibberellic acid.<br />
Other potential cultural controls are manipulation o f planting date <strong>and</strong> management<br />
o f levee vegetation. Thom pson et al. ( 1994b) planted rice from early April to late<br />
May <strong>and</strong> observed damaging densities o f RWWs on rice planted on all dates. However,<br />
rice planted in early April tolerated RW W damage better than rice planted later. Also,<br />
late planting is frequently associated with other problems, such as low yields <strong>and</strong> grain<br />
quality <strong>and</strong> poor st<strong>and</strong> establishment due to high temperatures. In California, Palrang<br />
et al. ( 1994) tilled levees mechanically to remove vegetation before rice planting. They<br />
compared subsequent adult RW W feeding scar densities in paddies adjacent to levees<br />
with <strong>and</strong> without vegetation. In general, feeding scar densities were lower in paddies<br />
adjacent to levees without vegetation, which suggests that removing levee vegetation<br />
may help control RWW'' damage in California.<br />
Certain rice varieties <strong>and</strong> lines are more susceptible than others to RW W damage.<br />
In general, higher RW W populations are found on medium-grain than long-grain<br />
varieties. For instance. Stout et al. (2001) in Louisiana found that the long-grain variety<br />
Jefferson was m ost resistant to RW W s, while the medium-grain varieties Bengal,<br />
Earl, <strong>and</strong> Mars were least resistant. The long-grain variety Cocodrie was also relatively<br />
susceptible. However, when yields in untreated <strong>and</strong> treated plots were compared,<br />
Cocodrie, Lemont, <strong>and</strong> Jefferson were more tolerant o f RWTW damage than other<br />
varieties in the study.<br />
Many lines <strong>and</strong> varieties have been screened for resistance/tolerance to RWWs.<br />
W C1403 <strong>and</strong> W C1711 are tolerant but are poorly adapted to U.S. growing conditions<br />
<strong>and</strong> consumer preferences (Robinson <strong>and</strong> Smitli, 1986). Also, attempts to<br />
incorporate resistance/tolerance genes into adapted varieties have been unsuccess-<br />
fijl to date. In California, rice breeders have attempted to transfer tolerance from<br />
W C1403 into better-adapted lines (McKenzie, 1992). In 1987, they released a tolerant<br />
germplasm line, PI506230. However, in large plot tests, PJ506230 yields were significantly<br />
less than M -201, a California-adapted variety. In Louisiana, selected anther<br />
culture-derived <strong>and</strong> hybridizing lines were evaluated for RW W resistance/tolerance<br />
(<strong>Rice</strong> etal., 2000). These lines harbored m ore RW W larvae than com mercial varieties<br />
Jodon <strong>and</strong> Lemont. However, two lines (H B2 <strong>and</strong> H B5) produced high yields despite<br />
high densities o f RWWs.<br />
N ’Guessan et al. (1994a,b) also evaluated rice anther <strong>and</strong> tissue culture lines for<br />
resistance/tolerance to the RWWs. Anther culture lines 952836 <strong>and</strong> 953527 <strong>and</strong> tissue<br />
culture lines 112 <strong>and</strong> 4754 exhibited tolerance while tissue culture lines 244 <strong>and</strong> 2232<br />
exhibited antixenosis. <strong>Smith</strong> <strong>and</strong> Robinson (1982) screened 106 rice cultivars for<br />
RW W resistance <strong>and</strong> reported that Bontoc, Finindoc, Carangiang, Nira, <strong>and</strong> Dawn
<strong>Rice</strong> Arthropod Pests <strong>and</strong> Their Management in the United States 443<br />
harbored significantly fewer larvae than the susceptible cultivars. N ’Guessan <strong>and</strong><br />
Quisenberry (1994) found that TX 12685 <strong>and</strong> TX 13079 exhibited moderate levels o f<br />
resistance compared to the susceptible cultivar Mars. Louisiana rice breeding lines<br />
8720906 <strong>and</strong> 8721937 were classified as moderately tolerant by N’Guessan et al. (1994c).<br />
Wu <strong>and</strong> W ilson (1997) concluded that the stage o f crop growth when RW W injury<br />
occurs greatly affects tolerance for root injury.<br />
Natural biological control o f RW W s was reported by Puissegur (1976), who observed<br />
predation o f adults <strong>and</strong> larvae by long-horned grasshoppers <strong>and</strong> dragonfly<br />
naiads, respectively. Bernhardt (1990) also observed adult RW W predation by longhorned<br />
grasshoppers, Conocephalus fasciatus <strong>and</strong> Orchelium vulgare. They preferred<br />
to feed on insects, including RW W s, prior to flowering o f the rice crop. A m ermithid<br />
nematode parasitizes adult RW W s, but parasitization rates are relatively low (Bun-<br />
yarat et al> 1977).<br />
So far, biological control efforts have proven ineffectual. Experiments witli com <br />
mercial formulations o f parasitic nematodes have not proven successful. Commercial<br />
formulations o f the parasitic nematodes Steinernema carpocapsae <strong>and</strong> Heterorhabditis<br />
sp. were evaluated for RW W control (Way <strong>and</strong> Wallace, 1992; Way et al., 1992a,b). Best<br />
control (about 40% ) was achieved when plots were drained after the permanent flood<br />
<strong>and</strong> nematodes applied to moist soil. Farmers dem<strong>and</strong> better control <strong>and</strong> are reluctant<br />
to drain fields after the perm anent flood, so these results are not encouraging.<br />
In addition. Way <strong>and</strong> Walla(;e (2000) applied a com m ercial formulation o f Bacillus<br />
thuringiensis subspecies tenebrionis before <strong>and</strong> after the permanent flood. They reported<br />
control failures for all rates <strong>and</strong> timings tested. Way <strong>and</strong> Wallace (1995c) also<br />
evaluated a com mercial form ulation o f Beauverta bassiam applied at selected times<br />
after the permanent flood. None o f the treatments reduced RW W larval densities<br />
significantly<br />
RICE STINK BUG<br />
The RSB is a serious pest o f rice in the south (Grigarick, 1984). W hen the crop begins<br />
to head, RSB adults, which are tan, move into rice fields from surrounding grassy<br />
weeds or sorghum. Adults lay green, barrel-shaped eggs in a mass composed o f two<br />
parallel rows. Usually, tlie egg masses arc laid on developing kernels. Eggs hatch <strong>and</strong><br />
first instar nymphs, which are red <strong>and</strong> black, remain on or near the hatched eggs for<br />
a short time. The insect passes through five nymphal instars. Second through fifth<br />
instars are marked with various patterns o f red, tan, <strong>and</strong> black lines <strong>and</strong> spots. The<br />
fifth instar possesses easily observed wing pads. Feeding is achieved by insertion o f<br />
stylets into developing grains, enzymatic digestion o f the contents, <strong>and</strong> withdrawal<br />
o f the fluids. Probes are associated with cone-shaped salivary sheaths that remain<br />
on the hull (Bowling, 1979). This feeding activity allows for introduction o f various<br />
microorganisms; such as Bipolaris oryzae, Curvularia lunata, Cercospora oryzae, Tnchonis<br />
caudata, Fusariutn oxysporum, Alternaría alternata, Alternaría padwickii, <strong>and</strong><br />
Nematospora coryli; which in com bination with the actual piercing causes discoloration<br />
o f the kernel (M archetti, 1984; Lee et al., 1986). This quality imperfection<br />
is called peck, for which farmers are heavily penalized. In addition, feeding activity<br />
results in a small fracture in the grain which causes breakage during milling. This<br />
reduction in head rice or percent o f whole grains is also justification for reducing the
444 Production<br />
iiáí'f<br />
i •’I-<br />
»i;-::<br />
price that farmers receive for their crop. Grant et al. (1986) found average discounts<br />
for direct <strong>and</strong> indirect peck damage ranged from about $14 to $150 per hectare in bid<br />
acceptance markets in Texas from 1981 to 1984.<br />
Research in Texas showed that RSB damage was greater when populations were<br />
not controlled during heading <strong>and</strong> milk versus dough (Harper et al., 1993). These<br />
results may be due to the longer time grains in the heading <strong>and</strong> m ilk stages were<br />
exposed to RSBs <strong>and</strong> associated microorganisms than in the dough stage. Also, ETs<br />
were developed which take into account the stage o f maturity o f the crop (i.e., heading,<br />
milk, or dough), date o f planting, projected yield <strong>and</strong> price o f rice, cost o f control,<br />
<strong>and</strong> sampled populations o f adult RSB (Harper et al., 1990, 1994). The sample<br />
unit is 10 consecutive sweeps o f a 38-cm -diam eter net. Thus the average number<br />
o f adult RSBs per 10 sweeps is compared to the ET. Only adults are counted since<br />
nymphs are not associated with damage. In Texas, the ET is approximately five adults<br />
per 10 sweeps during heading <strong>and</strong> m ilk <strong>and</strong> 10 adults per 10 sweeps during dough<br />
(Way, 2001).<br />
After release o f semidwarf varieties in the south, millers began complaining of<br />
an imperfection in milled rice called speck back, which is a small, site-specific lesion<br />
found on the dorsal surface o f the kernel (Bernhardt et al., 1987). Feeding by insects,<br />
including RSBs, was implicated as a possible cause. However, experiments revealed<br />
that an array o f insects caged on panicles was not associated with speck back (Cogburn<br />
<strong>and</strong> Way, 1991). Rather, late plantings o f susceptible semidwarf varieties, such as<br />
Lemont <strong>and</strong> Gulfmont, produced high levels o f the imperfection. Thus the disorder<br />
was not linked to insects but to certain varieties planted late <strong>and</strong> grown in given areas<br />
under specific environmental conditions. Concerned millers simply do not accept<br />
late-planted, susceptible varieties grown in speck back-prone areas.<br />
Experiments in Arkansas have sho^vn that RSB damage is most, intermediate, <strong>and</strong><br />
least prevalent in long-, medium-, <strong>and</strong> short-grain varieties, respectively (Bernhardt,<br />
2000). These studies were conducted in the field, where plots were exposed to natural<br />
infestations o f RSBs. The amount o f RSB damage was associated with the length of<br />
time to complete flowering <strong>and</strong> kernel maturity. Also, fields with abundant grassy<br />
weeds, such as Echinochloa crus~gali, usually harbor high popirlations o f RSBs.<br />
Because heading to m aturity is relatively short <strong>and</strong> RSBs are highly m obile, insecticides<br />
are relied on heavily to achieve control. Certain labeled insecticides, such as<br />
methyl parathion, have little residual activity, while labeled formulations o f carbaryl<br />
<strong>and</strong> A.-cyhalothrin have longer residual activity (Way <strong>and</strong> Wallace, 1990). Thus, in<br />
Texas, insecticides with residual activity are recommended when ETs are exceeded<br />
early (during heading <strong>and</strong> m ilk), when rice is m ost susceptible to RSB damage. If ETs<br />
are exceeded later, the m ore inexpensive methyl parathion is recommended. Acephate<br />
has demonstrated excellent residual activity hut is not yet registered on rice.<br />
The fall armyworm (FAW) <strong>and</strong> armyworm (AW) are sporadic pests o f rice in the south<br />
<strong>and</strong> California, respectively (Bowling, 1978; <strong>Rice</strong> et al., 1982). The larval stages o f both<br />
pests defoliate rice with occasional feeding damage to panicles. FAWs can attack rice<br />
from emergence to harvest but usually are observed damaging rice before application<br />
o f the permanent flood (Figure 3.6.1; see color insert). Bowling (1978) simulated
IT<br />
<strong>Rice</strong> Arthropod Pests <strong>and</strong> Their Management in the United States 445<br />
FAW damage by mowing rice <strong>and</strong> found that 50% leaf removal during the seedling<br />
<strong>and</strong> tillering stages reduced yields 8 <strong>and</strong> 12% , respectively. Southern farmers often<br />
control FAW populations by timely flooding o f fields, which drowns larvae. However,<br />
if fields are not in need o f flooding, or sufficient irrigation water is unavailable at the<br />
tim e o f a damaging infestation, farmers rely on insecticides for control. However, the<br />
choice o f insecticide can be critical since organophosphate <strong>and</strong> carbamate insecticides<br />
interact negatively with propanil (a com m on rice herbicide in the south) if herbicide<br />
<strong>and</strong> insecticide are applied close in time (Sm ith et al., 1977). Many soutliern rice<br />
farmers are alerted to damaging FAW populations by scouting fields for birds, such as<br />
cattle egrets, which prey on FAW larvae. In California, AWs usually attack rice close<br />
to heading. <strong>Rice</strong> et al. (1982) found that rice in the boot stage tolerated between 25<br />
<strong>and</strong> 50% simulated defoliation before significant yield reductions occurred.<br />
CHINCH BUG<br />
Chinch bugs (CBs), which have piercing-sucking mouthparts, are sporadic pests o f<br />
seedling rice in the south (M ejia-Ford, 1997). Adults are black with white markings<br />
on their dorsum (Figure 3.6.2; see color insert). First instar nymphs are orange, while<br />
second through fourth instars are progressively darker. Fifth instar nymphs are black<br />
with wing pads. Adults lay orange eggs on seedling rice culms <strong>and</strong> in soil surrounding<br />
culms. Recent data from environmental chamber studies mimicking spring conditions<br />
showed that generation time for CBs was about 60 days on rice or sorghum<br />
(M ejia-Ford, 1997).<br />
Farmers previously attributed poor st<strong>and</strong>s (particularly on levees, but also in<br />
paddies) to seedling diseases, excessive salts in soil, blackbird sprout pulling, lack<br />
o f sufficient soil moisture, <strong>and</strong> so on. However, recent research in Texas also identified<br />
CB damage as an im portant constraint to adequate st<strong>and</strong>s. M ejia-Ford (1997)<br />
conducted greenhouse cage studies to identify <strong>and</strong> quantify CB damage to seedling<br />
rice. She found that damage symptoms to foliage included yellow stippling; white<br />
b<strong>and</strong>ing parallel to the long axis o f leaves; circular, white lesions across the width o f<br />
leaves; <strong>and</strong> blunt tips (Figures 3,6.3 to 3.6.5; see color insert). The latter two symptoms<br />
were caused by feeding before leaves unfurled. Thus, after unfurling, feeding<br />
lesions across the width o f a leaf coalesce. This causes the portion of the leaf distal<br />
to the damage to die <strong>and</strong> drop off, which results in a blunt-tipped leaf. More severe<br />
symptoms include dying <strong>and</strong> dead leaves <strong>and</strong> seedling m ortality (Figure 3.6.6; see<br />
color insert). Damaged plants are also stunted <strong>and</strong> can produce m ore tillers than can<br />
undamaged plants. As few as one adult per two plants can cause seedling mortality<br />
(Figure 3.6.7). In fact, the current Texas E T for CBs is an average o f one adult per<br />
seedling (Way, 2001).<br />
CBs are often controlled by tim ely flooding which drowns insects or forces them<br />
to move from the lower culm up to the foliage. M ejia-Ford (1997) found that feeding<br />
on lower culms <strong>and</strong> roots o f rice seedlings causes m uch more damage than feeding on<br />
foliage. Farmers often observed more CB damage to levee than to paddy rice (Figure<br />
3.6.8; see color insert). They believed that flooding fields forced CBs to move to levees<br />
where rice remained unflooded. However, M ejia-Ford (1997) found that flooding<br />
paddies simply forces CBs from the lower culms to the foliage, where, as mentioned<br />
above, resulting damage is less severe.
446<br />
Production<br />
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Ríce Arthropod Pests <strong>and</strong> Their Management in the United States 447<br />
rice seeds. Damage can result in rice st<strong>and</strong> loss, which can force fanners to replant,<br />
which is expensive <strong>and</strong> frequently occurs after the optim al planting time.<br />
Management is based on modifying certain cultural practices. Obviously, substituting<br />
dry planting for water planting will eliminate midge problems. However, in<br />
water-planted rice, increasing seeding rate <strong>and</strong> planting pregerminated seed (rather<br />
than dry seed) as soon as possible after flooding minimizes the likelihood o f the<br />
simultaneous occurrence o f damaging populations o f late instar rice seed midges<br />
<strong>and</strong> germinating rice seeds which are m ost vulnerable to damage (Clem ent et al.,<br />
1977a). Recently, fipronil seed treatment was labeled for rice seed midge control in<br />
the United States (Way, 2001). Although very few data are available regarding the<br />
efficacy o f fipronil for rice seed midge control in the United States, fipronil is effective<br />
<strong>and</strong> labeled for rice seed midges in Australia, where these insects are key pests o f<br />
rice (Stevens et a l, 1998; Clampett <strong>and</strong> Stevens, 2000). Also, in 2002, imazethapyr<br />
herbicide-resistant rice varieties are planned for commercial <strong>production</strong> in the south<br />
(Rood, 2001). Farmers who plant these varieties can apply imazethapyr to control red<br />
rice, which is a weed pest o f rice. Red rice <strong>and</strong> rice are the same species but different<br />
strains (Sm ith et al., 1977). In southwestern Louisiana, water planting is practiced<br />
to manage red rice. Thus, when imazethapyr-resistant varieties are available, many<br />
farmers in southwestern Louisiana may switch from water to dry planting, which will<br />
reduce rice seed midge problems.<br />
RICE LEAF MINER<br />
The rice leaf m iner (RLM ) is an occasional pest, prim arily in water-planted rice, in<br />
the United States (M an<strong>and</strong>har <strong>and</strong> Grigarick, 1983; Grigarick, 1984; Way et a l, 1985,<br />
1991). Adult females lay single, white, spindle-shaped eggs on the dorsal side o f leaves<br />
lying on the water surface. After eggs hatch, larvae burrow into the leaf <strong>and</strong> feed on<br />
mesophyll tissue, which results in irregular, elongate mines. Pupation also takes place<br />
within the mines.<br />
Generally, RLM damage is m ore severe in deeper water (e.g., paddies nearest the<br />
field drain <strong>and</strong> borrow ditches adjacent to levees), which causes rice to elongate <strong>and</strong><br />
weaken before emergence tlirough water (Grigarick 1959). Under these conditions,<br />
rice foliage will eventually emerge through water, then lie on the water surface for<br />
a period o f time before lifting off the surface to continue development. Thus, dryplanting,<br />
precision-leveling fields (which frequently reduces tire number o f levees in<br />
fields), <strong>and</strong> m aintaining a shallow flood are cultural practices that will minimize or<br />
eliminate RLM problems.<br />
RICE STEM BORERS<br />
The sugarcane borer <strong>and</strong> rice stalk borer occur throughout the south, while the M exican<br />
rice borer (M RB) occurs only in the southern rice-producing counties o f Texas<br />
(Sm ith et a l, 1986; Browning et a l, 1989). (Figures 3.6.9 to 3.6.11; see color insert).<br />
No documented stem borer problems have been reported from California. These stem<br />
borer species damage rice in a similar manner. Adults lay eggs on rice foliage. Upon
448 Production<br />
hatching, larvae move from the foliage to the space between leaf sheaths <strong>and</strong> culms.<br />
Here they are somewhat protected from abiotic <strong>and</strong> biotic dangers. Larvae m ine the<br />
inside o f sheaths before boring into the culms, where they complete the larval <strong>and</strong><br />
pupal stages (Figure 3.6.12; see color insert). Feeding damage causes deadhearts (dead<br />
leaves <strong>and</strong> tillers) <strong>and</strong> whiteheads (panicles with unfilled grains).<br />
The M RB is becoming an increasing problem in rice grown in Texas, where this<br />
borer was introduced from Mexico into the lower Rio Gr<strong>and</strong>e VaUey in 1980 (K. Johnson,<br />
1984). It gradually moved north <strong>and</strong> was detected for the first tim e in Texas rice-<br />
producing counties in 1987. Since 1987, the M RB has gradually extended its range.<br />
Studies in Texas in 1999 show that natural infestations o f M RBs <strong>and</strong> sugarcane borer<br />
can reduce yield substantially (Table 3.6.2). Timing o f application oftebufenozide <strong>and</strong><br />
methoxyfenozide was critical— ^application at 24 days after perm anent flood (close to<br />
panicle differentiation) was more effective tlian application 16 days earlier. In fact,<br />
regardless o f rate, later applications produced an average increase in yield o f more<br />
than 4000 kg/ha over untreated crops. The fipronil treatm ent outyielded the untreated<br />
by approximately 4800 kg/ha, which was due to a com bination o f stem borer <strong>and</strong><br />
RWW control.<br />
ETs are not established for stem borers in the United States but research is being<br />
conducted in Texas, where M RB <strong>and</strong> sugarcane borer are becoming more problematic,<br />
to develop ETs <strong>and</strong> management guidelines. Currently, the only insecticide labeled for<br />
stem borers is fipronil formulated as a seed treatm ent (Way, 2001),<br />
LEAFHOPPERS<br />
The aster leafhopper (ALH) <strong>and</strong> blackfaced leafhopper (BFL) are sporadic pests o f rice<br />
in California <strong>and</strong> Texas, respectively. Leafhoppers have piercing-sucking mouthparts,<br />
TABLE 3.6.2. M e x ic a n R ice B o re r a n d S u g a r c a n e B o r e r C o n tro l at G a n a d o , T e xas, 1 9 9 9<br />
Tim ing of<br />
M e a n<br />
M e a n<br />
Rate<br />
Application<br />
Number^’<br />
Yield*'<br />
Treatment<br />
[kgtAll/ha]<br />
(dapt)“*<br />
(whiteheads/m^)<br />
(kg/ha)<br />
pinii<br />
Tebufenozide 0.14 8 17.1a 5771cd<br />
■ 24 2.7d 9130ab<br />
0.28 8 15.3a 6018cd<br />
24 5.7cd 9065ab<br />
Methoxyfenozide 0.034 8 14.8a 6206cd<br />
24 7,7bcd 8385b<br />
0.067 8 13.5ab 6863c<br />
24 5. led 8954ab<br />
0.14 8 16.5a 6489c<br />
24 5.9cd 8944ab<br />
Fipronil 0.056 Seed 2.5d 9938a<br />
treatment<br />
Untreated — 10.3abc 5123d<br />
“dapf, days after permanent flood.<br />
“Means in a column followed by the same or no letter are not significantly different at the 5% level (anova,<br />
DMRT).
<strong>Rice</strong> Arthropod Pests <strong>and</strong> Their Management in the United States 449<br />
which enable them to remove fluids from the foliage o f rice plants. Way et al. (1983)<br />
found that high populations o f ALHs were associated with high densities o f aquatic<br />
weeds, such as Monochoria vaginalis, Sagittaria montevidensis, Bacopa rotundifolia,<br />
Rotala indica, <strong>and</strong> Alisma trivale. Way et al. (1984) also found that ALHs preferred<br />
senescent to green rice foliage. Yield reductions o f approximately 12% were associated<br />
with peak populations o f about 40 to 70 ALHs per plant. Way et al. (1986) evaluated<br />
drop traps for sampling ALHs <strong>and</strong> found that the most useful trap was made<br />
o f a transparent, plastic cylinder coated with petroleum jelly which trapped ALHs<br />
dislodged from rice during agitation. To manage ALHs, farmers are encouraged to<br />
produce a good st<strong>and</strong> o f rice (to compete with aquatic weeds) <strong>and</strong> apply herbicides<br />
early to control aquatic weeds before ALH buildup to damaging levels. I f aquatic<br />
weeds are not controlled early, high densities o f ALH can move from dead <strong>and</strong> dying<br />
weeds to rice. Graze <strong>and</strong> Grigarick (1989) reported predation o f ALH by the lycosid<br />
spider, Pardosa ramulosa. Cages with spiders were placed over patches o f aquatic weeds<br />
where ALHs were abundant. ALH populations were reduced approximately 90% by<br />
the addition o f no more than 22 P. ramulosa per square meter.<br />
Presence o f sooty mold fungus <strong>and</strong> nymphal cast skins on foliage are indicative<br />
o f high populations o f BPLs. Bronzing o f foliage can also be observed under high<br />
population pressure (Figure 3,6.13; see color insert). Acephate <strong>and</strong> carbaryl provided<br />
better control o f BBL than methyl parathion in an aerial application experiment in<br />
Texas (Way et al., 1989). Pretreatment populations o f more than 1000 BFLs per 20<br />
sweeps o f a 3S-cm -diam eter net were recorded.<br />
GRAPE COUSPIS<br />
The grape colaspis is a m inor pest o f delayed flooded rice in the south (Sm ith et al.,<br />
1986). Adults are rusty yellow or brown with rows o f evenly spaced punctures on their<br />
elytra. Overwintering larvae feed on germinating seeds <strong>and</strong> roots o f rice seedlings<br />
following establishment on legumes, such as soybeans, tlie preceding year. Damage<br />
can be eliminated or minimized by flooding paddies or not planting rice in fields<br />
planted with legumes the preceding year. However, levee rice will remain vulnerable<br />
to damage. Fipronil seed treatm ent is registered for control (Anonymous, 2001).<br />
TADPOLE SHRIMP<br />
Tadpole shrimp are crustaceans that feed on germinating seeds <strong>and</strong> seedlings in waterplanted<br />
rice in California (Grigarick et al., 1985), These pests are adapted to natural<br />
<strong>and</strong> artificial vernal pools, such as rice fields. Orange eggs are laid in the mud, where<br />
they can remain dorm ant, viable, <strong>and</strong> resistant to desiccation for long periods o f time.<br />
Cultivation brings eggs to the surface, where they hatch when rice paddies are flooded.<br />
Feeding activity also dislodges rice; thus tadpole shrimp are st<strong>and</strong> reducers. In addition,<br />
these pests disturb tlie mud surface, which creates turbid floodwater, resulting in<br />
reduced photosyntlietic activity o f young submerged rice. As with rice seed midges,<br />
tadpole shrimp problems can be eliminated by dry-planting rice. In water-planted<br />
rice, seeding as soon as possible after flooding to avoid high densities o f older, more<br />
voracious tadpole shrimp is recommended in California. Copper sulfate provides
450 Production<br />
effective control o f tadpole shrimp. Grigarick et al. (1985) reported evidence for the<br />
development o f resistance to etliyl parathion in certain rice-producing counties in<br />
California.<br />
CRAYFISH<br />
ytir<br />
Crayfish are m inor pests o f water-planted rice in California, where they feed on young<br />
seedlings. Like tadpole shrimp, crayfish are st<strong>and</strong> reducers. Their grazing activities<br />
are nocturnal, so they can easily be overlooked (Penn, 1943). Feeding is generally<br />
nonselective, with damaged areas devoid of both weeds <strong>and</strong> rice. All aboveground<br />
vegetation is consumed, which creates barren areas, clearly evident when paddies<br />
are drained. Crayfish also burrow into levees <strong>and</strong> adjacent to irrigation gates, which<br />
causes unwanted drainage o f floodwater (Chang <strong>and</strong> Lange, 1967). Grigarick <strong>and</strong> Way<br />
(1982) reported that natural infestations o f crayfish reduced rice st<strong>and</strong> from 70 to<br />
100% in a 2-year experiment. Fenthion <strong>and</strong> methyl parathion gave better control of<br />
crayfish than carbaryl, copper sulfate, or ethyl parathion.<br />
ROLE OF RICE ENTOMOLOGISTS IN THE UNITED STATES<br />
Changes in rice <strong>production</strong> practices catalyze changes in rice pest management. When<br />
rice farmers implement new technologies (e.g., conservation tillage, precision planting<br />
<strong>and</strong> irrigating, <strong>and</strong> improved varieties), pest diversity <strong>and</strong> abundance are often<br />
greatly affected, which forces alterations in management strategies <strong>and</strong> tactics. Adoption<br />
o f novel pest management tools (e,g„ genetically modified rice with pest resistance<br />
<strong>and</strong> new generation pesticides) calls for identifying <strong>and</strong> developing the most<br />
effective, safe, <strong>and</strong> affordable applications o f these tools. Entomologists must work<br />
closely with farmers <strong>and</strong> other scientists to develop control programs that mesh with<br />
current <strong>production</strong> practices.<br />
Changes in government regulations trigger changes in rice pest management,<br />
Regulatory policies are becom ing increasingly stringent, particularly for the rice agroecosystem,<br />
with its fragile, aquatic environment. Withdrawal o f pest management<br />
tools by federal <strong>and</strong> state agencies can create crises in the U S . rice industry. Agrichemical<br />
companies, the U.S. rice industry, entomologists, <strong>and</strong> regulatory agencies<br />
must work cooperatively to bring new management tools on line rapidly.<br />
Changes in pests <strong>and</strong> pest status create changes in rice pest management. Pests<br />
can develop resistance to management tools, <strong>and</strong> new pests can be introduced (e.g.,<br />
MRBs in Texas <strong>and</strong> RWWs in California). In specific years <strong>and</strong> locations, minor pests<br />
become key pests, due to climatic changes, adoption o f <strong>production</strong> practices conducive<br />
to pest population increase (e.g., widespread planting o f a susceptible variety),<br />
genetic mutation in a pest, <strong>and</strong> destruction o f natural control agents. Entomologists<br />
must closely m onitor pest status <strong>and</strong> the introduction of new pests so that control<br />
programs can be developed in a. timely, proactive manner.<br />
Changes in rice pest management leads to changes in outreach programs. Once<br />
effective control programs are in place, entomologists must bring these programs to<br />
fruition by educating end users to their proper application. The vehicles for education<br />
can be publications (printed <strong>and</strong> electronic), meetings, videos, <strong>and</strong> one-on-one
<strong>Rice</strong> Arthropod Pests <strong>and</strong> Their Management in the United States 451<br />
discussions. Feedback from outreach efforts are crucial to improving pest managem<br />
ent programs <strong>and</strong> alerting entomologists to potential problems.<br />
The key word is change. The biotic, abiotic, regulatory, market, <strong>and</strong> political<br />
environments are dynamic <strong>and</strong> unstable. All affect U.S. rice pest management. E n<br />
tomologists must anticipate <strong>and</strong> adapt to these changes to continue to serve the U.S.<br />
rice industry effectively. Close cooperation among entomologists <strong>and</strong> other scientists,<br />
the U.S. rice industry, the private sector, <strong>and</strong> state <strong>and</strong> federal government agencies is<br />
the cornerstone to developing effective pest management programs.<br />
ACKNOWLEDGMENTS<br />
I greatly appreciate Cynthia Tribble, Tammy Tindel, <strong>and</strong> Robin Clements for clerical<br />
support. I thank my entomology colleagues in the United States for their cooperation<br />
<strong>and</strong> help. I acknowledge <strong>and</strong> appreciate the financial support provided by Texas rice<br />
farmers, other private industries, USDA, <strong>and</strong> the Texas Agricultural Experiment Station.<br />
Finally, I thank m y wife, Jeanie, for encouragement during preparation o f this<br />
chapter.<br />
REFERENCES<br />
Anonymous. 2000. <strong>Rice</strong> variety acreage tables. Proc. <strong>Rice</strong> Tech. Work. Group 28:15-28.<br />
Anonymous. 2001. Icon 6.2FS. Crop Protection Reference. C ^ P Press, New York, p. 118.<br />
Bernhardt, J. L. 1990. Diet o f grasshoppers in rice fields. Proc. <strong>Rice</strong> Tech. Work. Group<br />
23:65-66.<br />
Bernhardt, J. L. 1995a. Control o f rice water weevil with fipronil applied preplant<br />
incorporated, 1994. Arthropod Manag. Tests 20:225.<br />
Bernhardt, J. L. 1995b. Control o f rice water weevil with fipronil as a seed treatment,<br />
1994. Arthropod Manag. Tests 20:226.<br />
Bernhardt, J. L. 1996. Control o f rice water weevil with fipronil, 1995. Arthropod<br />
Manag. Tests 2 1:280-281.<br />
Bernhardt, J. L. 1997. Control o f rice water weevil with fipronil, 1996A. Arthropod<br />
Manag. Tests 22:286-287.<br />
Bernhardt, J. L. 2000. W hy do some rice varieties have more rice stink bug damage<br />
than others? Proc. <strong>Rice</strong> Tech. Work, Group 28:78.<br />
Bernhardt, J. L., N. P. Tugwell, R. N. Sharp, <strong>and</strong> W. H. Dodgen. 1987. Speck back: a<br />
new rice kernel imperfection. Ark. Farm Res. 36(5): 10.<br />
Bowling, C. C. 1978. Simulated insect damage to rice: effects o f leaf removal. /. Econ.<br />
Entomol.7l{2):377-37S.<br />
Bowling, C. C. 1979. The stylet sheath as an indicator o f feeding activity o f the rice<br />
stink bug. /. Econ. Entomol. 72:259-260.<br />
Browning, H. W., M . O. Way, <strong>and</strong> B. M . Drees. 1989. Managing the Mexican <strong>Rice</strong> Borer<br />
in Texas. Tex. Agric. Ext. Serv./Exp. Stn. B-1620, 8 pp.<br />
Bunyarat, M ., N. P. Tugwell, <strong>and</strong> R. D. Riggs. 1977. Seasonal incidence <strong>and</strong> effect o f<br />
a mermithid nematode parasite on the m ortality <strong>and</strong> egg <strong>production</strong> o f the rice<br />
water weevil, Lissorhoptrus oryzophilus. Environ. Entomol. 6:712-714.<br />
m<br />
il
wm<br />
452 Production<br />
Cave, G. L., <strong>and</strong> C. M. <strong>Smith</strong>. 1983. Number of instars o f the rice water weevil,<br />
Lissorhoptrus oryzophilus. Ann. Entomol Soc. Am. 76:293“ 294.<br />
Chang, V, S. C., <strong>and</strong> W. H. Lange, 1967. Laboratory <strong>and</strong> field evaluation of selected<br />
pesticides for control of the red crayfish in California rice fields. J. Econ. Entomol.<br />
60:473-477.<br />
Clampett, W. S., <strong>and</strong> M . M. Stevens. 2000. <strong>Rice</strong> Crop Protection Guide, 2000. New<br />
South Wales Agriculture. 12 pp.<br />
Clement, S. L., A. A. Grigariclc, <strong>and</strong> M. O. Way. 1977a. Conditions associated with rice<br />
plant injury by chironomid midges in California. Environ. Entomol 6:91-96.<br />
Clement, S. L., A. A. Grigarick, <strong>and</strong> M. O. Way. 1977b. The colonization o f California<br />
rice paddies by chironomid midges. /. Appl Ecol 14:379-389.<br />
Cogburn, R. R., <strong>and</strong> M . O. Way. 1991. Relationship o f insect damage <strong>and</strong> other factors<br />
to the incidence of speck back, a site-specific lesion on kernels o f milled rice.<br />
J. Econ. Entomol 84(3):987-995,<br />
Drees, B. M ., <strong>and</strong> M. O. Way. 1998. Insect management alternatives. <strong>Rice</strong> Production<br />
Guidelines, Tex. Agric. Ext, Serv, D -1253, pp. 30-43.<br />
Flickinger, E, L., K. A. King, W. F. Stout, <strong>and</strong> M. M. M ohn. 1980. Wildlife hazards<br />
from Furadan 3G applications to rice in Texas. /. WUdl Manage. 44(1): 190-197.<br />
Grant, W. R., M . E. Rister, <strong>and</strong> B, W. Brorsen. 1986. <strong>Rice</strong> Quality Factors: Implications,<br />
for Management Decisions. Tex. Agric. Exp. Stn. B-1541.<br />
Grigarick, A. A. 1959. Bionom ics o f the rice leaf miner, Hydrellia griseola (Fallen), in<br />
California. Hilgardia 29:1-80.<br />
Grigarick, A. A. 1970. Econom ic injury by the rice water weevil in California <strong>and</strong> the<br />
relationship o f injury to the field margins. Proc. <strong>Rice</strong> Tech, Work. Group 13:26.<br />
Grigarick, A. A. 1984. General problems with rice invertebrate pests <strong>and</strong> their control<br />
in the United States. Prof. Ecol 7:105-114.<br />
Grigarick, A, A., <strong>and</strong> G. W, Beards. 1965. Ovipositional habits of rice water weevil<br />
in California as related to a greenhouse evaluation o f seed treatments. J. Econ.<br />
Entomol 58:1053-1056,<br />
Grigarick, A. A., <strong>and</strong> M. O. Way, 1982, Role o f crayfish (Decapoda; Astacidae) as pests<br />
of rice in California <strong>and</strong> their control. /. Econ. Entomol 75(4):633-636,<br />
Grigariclc, A. A., J. H. Lynch, <strong>and</strong> M . O. Way. 1985. Controlling tadpole shrimp. Calif<br />
Agric. 39:12-13.<br />
Harper, J. K., M. E. Rister, J. W. Mjelde, B. M . Drees, <strong>and</strong> M. O. Way. 1990. Factors<br />
influencing the adoption o f insect management <strong>technology</strong>. Am, J. Agric. Econ.<br />
72(4):997-1005.<br />
Harper, J. K., M. O. Way, B. M. Drees, M . E. Rister, <strong>and</strong> J. W. Mjelde. 1993. Damage<br />
function analysis for the rice stink bug. /. Econ. Entomol 86(4): 1250-1258.<br />
Harper, J. K.> J. W. Mjelde, M . E. Rister, M . O. Way, <strong>and</strong> B. M . Drees. 1994. Developing<br />
flexible thresholds for pest management using dynamic programming. J. Agric.<br />
Appl Econ. 26(1): 134-147.<br />
Helms, R. 1988. Establishing a uniform st<strong>and</strong>. In <strong>Rice</strong> Production H<strong>and</strong>book. Coop.<br />
Ext. Serv. Univ. Ark. M P192, pp. 14-17.<br />
Hesler, L. S., A. A. Grigarick, M. J. Craze, <strong>and</strong> A. T. Palrang. 1992. Effects o f temporary<br />
drainage on selected life <strong>history</strong> stages o f the rice water weevil in California. }.<br />
Econ. Entomol 85(3):950-956,<br />
Hix, R., J. L, Bernhardt, <strong>and</strong> D. T. Johnson. 2000. M onitoring adult rice water weevils<br />
with an aquatic barrier trap. Proc. Rke Tech. Work. Group 28:87.
<strong>Rice</strong> Arthropod Pests <strong>and</strong> Their Management in the United States 453<br />
Johnson, D,, <strong>and</strong> J. Bernhardt. 1988. Controlling insects. In <strong>Rice</strong> Production H<strong>and</strong>book.<br />
Coop. Ext. Serv. Univ. Ark. M P 192, pp. 46-48.<br />
Johnson, K. J .R. 1984.. Identification o f Eoreuma loftini (Dyar) in Texas, 1980: forerunner<br />
for other sugarcane boring pest immigrants from Mexico? Bull Entomol<br />
Soc. Am. 30:47-52,<br />
Klosterboer, A. D., <strong>and</strong> G. N. McCauley. 2001. Irrigation <strong>and</strong> water management. In<br />
<strong>Rice</strong> Production Guidelines. Tex. Agric. Ext. Serv. D -1253, pp. 12-13.<br />
Knabke, J. J. 1973. Diapause in the rice water weevil Lissorhoptrus oryzophilus Kuschel<br />
in California. Ph.D. dissertation. Department o f Entomology, University of<br />
California-Davis, 134 pp.<br />
Lange, W. H., <strong>and</strong> A. A. Grigariclc. 1959. <strong>Rice</strong> water weevil: beetle pest in rice growing<br />
areas o f southern states discovered in California. Calif. Agric. 13:10-11.<br />
Lee, F. N., N. P. Tugwell, G. J. Weidemann, <strong>and</strong> W. C. <strong>Smith</strong>. 1986. M icroorganisms<br />
associated with pecky rice. Proc. <strong>Rice</strong> Tech. Work. Group 21:90.<br />
Linscombe, S. D., J. K. Saichuk, K. P. Seilhan, P. K. Bollich, <strong>and</strong> E. R. Funderburg, 1999.<br />
General agronomic guidelines. In Louisiana <strong>Rice</strong> Production H<strong>and</strong>book. Louisiana<br />
State University Agricultural Center, Baton Rouge, LA, pp. 5 -1 2 .<br />
Littrell, E. E. 1988. Waterfowl m ortality in rice fields treated with the carbamate,<br />
carbofuran. Calif Pish Game 74(4):226-231.<br />
Man<strong>and</strong>har, D. N., <strong>and</strong> A. A. Grigaricfc. 1983. Effect o f rice leaf m iner feeding on early<br />
growth o f the rice plant. J. Econ. Entomol 76:1022-1027.<br />
Marchetti, M . A. 1984. The role o f Bipolaris oryzae in floral abortion <strong>and</strong> kernel<br />
discoloration in rice. PlantDis. 68(4):288-291.<br />
McKenzie, K. S. 1992. Breeding for tolerance to rice water weevil. Proc. <strong>Rice</strong> Tech.<br />
Work. Group 24:59.<br />
M ejia-Pord, O. 1997. Studies o f chinch bug. BUssus leucopterus leucopterus (Say), in<br />
rice, Oryza sativa L.: an integrated pest management approach. Ph.D. dissertation.<br />
Department o f Entomology, Texas A&M University, College Station, TX ,<br />
130 pp.<br />
Morgan, D. R., P. H, Slaymaker, J. F. Robinson, <strong>and</strong> N. P. Tugwell. 1984. <strong>Rice</strong> water<br />
weevil indirect flight muscle development <strong>and</strong> emergence in response to temperature.<br />
Environ. Entomol 13:26-28.<br />
Morgan, D. R., N. P Tugwell, <strong>and</strong> J. L. Bernhardt. 1989. Early rice field drainage for<br />
control o f rice water weevil <strong>and</strong> evaluation o f an action threshold based upon<br />
leaf-feeding scars o f adults, J. Econ, Entomol 82(6}:1757-1759.<br />
Muda, A. R. B., N. P Tugwell, <strong>and</strong> M. B. Haizlip. 1981. Seasonal <strong>history</strong> <strong>and</strong> indirect<br />
flight muscle degeneration <strong>and</strong> regeneration. Environ. Entomol 10:685-690,<br />
N ’Guessan, F,. K., <strong>and</strong> S. S. Quisenberry. 1994. Screening selected rice lines for resistance<br />
to the rice water weevil. Environ. Entomol 23{3);665-675.<br />
N’Guessan, F. K., S. S. Quisenberry, <strong>and</strong> T. P Croughan. 1994a. Evaluation o f rice<br />
anther culture lines for tolerance to the rice water weevil. Environ, Entomol<br />
23(2):331-336.<br />
N’Guessan, F. K., S. S. Quisenberry, <strong>and</strong> T, P Croughan. 1994b. Evaluation o f rice<br />
tissue culture lines for resistance to rice water, weevil. /. Econ. Entomol 87(2);<br />
504-513.<br />
N’Guessan, F. K., S. S. Quisenberry, R. A. Thom pson, <strong>and</strong> S. D. Linscombe. 1994c.<br />
Assessment o f Louisiana rice breeding lines for tolerance to the rice water weevil.<br />
J, Econ. Entomol 87(2):476-481.
lili<br />
lili i<br />
l l i i<br />
IEÍÍiÍM';<br />
lijili'í<br />
■ II<br />
454 Production<br />
Oraze, M. J., <strong>and</strong> A. A. Grigarick. 1989. Biological control of aster leafhopper <strong>and</strong><br />
midges by Pardosa ramuhsa in California rice fields. J. Econ, Entomol 8 2 (3 );7 4 5 -<br />
749.<br />
Palrang, A. X , A, A. Grigarick, M . J. Graze, <strong>and</strong> L. S. Hesler. 1994. Association o f levee<br />
vegetation to rice water weevil infestation in California rice. /. Econ, Entomol.<br />
87(6); 1701-1706.<br />
Penn, G. H., Jr, 1943. A study o f the life <strong>history</strong> o f the Louisiana red-crawfish, Camharus<br />
darkii Girard. Ecology 24:1-18.<br />
Puissegur, W, J. 1976. Predators o f the rice water weevil, Lissorhoptrus oryzophilus<br />
Kuschel, <strong>and</strong> the effects o f bufencarb, carbofuran <strong>and</strong> a D im ilin-propanil m ixture<br />
on these <strong>and</strong> other nontarget aquatic species. M.S. thesis. Louisiana State<br />
University, Baton Rouge, LA, 70 pp.<br />
<strong>Rice</strong>, S. E., A, A. Grigarick, <strong>and</strong> M . O. Way, 1982. Effect o f leaf <strong>and</strong> panicle feeding by<br />
armyworm larvae on rice grain yield. /. Econ. Entomol 75(4):593-595.<br />
<strong>Rice</strong>, W. C., Q. R. Chu, <strong>and</strong> M. J. Stout. 2000. Evaluation o f selected lines for rice water<br />
weevil resistance. Proc. <strong>Rice</strong> Tech. Work, Group 28:73.<br />
Robinson, J. R, <strong>and</strong> C. M. <strong>Smith</strong>. 1986. <strong>Rice</strong> water weevil: plant resistance evaluations.<br />
Proc, <strong>Rice</strong> Tech. Work. Group 21:91-92.<br />
Rood, M. 2001. New products. <strong>Rice</strong> /. 104(4): 10.<br />
Rutger, J. N., <strong>and</strong> D. M. Br<strong>and</strong>on. 1981. California rice culture. Sei Am. (Feb.):42-51.<br />
S<strong>and</strong>berg, C. L,, C. E. Crittendon, <strong>and</strong> R. X Weil<strong>and</strong>. 2000. Application timing o f<br />
Dimilin 2L for rice water weevil control in California rice. Proc. <strong>Rice</strong> Tech. Work.<br />
Group 28:68,<br />
<strong>Smith</strong>, C. M ., <strong>and</strong> J. E Robinson. 1982. Evaluation o f rice cultivars grown in North<br />
America for resistance to the rice water weevil. Environ. Entomol 11:334-336.<br />
<strong>Smith</strong>, C. M ., J. L. Bagent, S. D. Linscombe, <strong>and</strong> J. E Robinson. 1986. Insect Pests of<br />
<strong>Rice</strong> in Louisiana. La, Agric. Exp, Stn. Bull. 774, 24 pp.<br />
<strong>Smith</strong>, K. A., A. A, Grigarick, J. H. Lynch, <strong>and</strong> M. J. Graze. 1985. Effect o f alsystin <strong>and</strong><br />
diflubenzuron on the rice water weevil. /. Econ. Entomol 78:185-189.<br />
<strong>Smith</strong>, R. J., Jr., W. T. Flinchum, <strong>and</strong> D. E. Seaman. 1977. Weed Control in U.S. <strong>Rice</strong><br />
Production. Agriculture H<strong>and</strong>book 497. U.S. Departm ent o f Agriculture, Washington,<br />
D C, 78 pp.<br />
Stevens, M. M.,. S. Helliwell, <strong>and</strong> G. N. Warren. 1998. Fipronil seed treatments for the<br />
control o f chironomid larvae in aerially-sown rice crops. Field Crops Res. 5 7 :195-<br />
207.<br />
Stout, M. J., W. C. <strong>Rice</strong>, R. M. Riggio, <strong>and</strong> D. R. Ring. 2000. T he effects o f four<br />
insecticides on the population dynamics o f the rice water weevil, Lissorhoptrus<br />
oryzophilus Kuschel. /. Entomol Sei 35(1);4 8 -6 1 .<br />
Stout, M. J., W. C. <strong>Rice</strong>, S. D. Linscombe, <strong>and</strong> R K. Bollich. 2001. Identification of<br />
rice cultivars resistant to Lissorhoptrus oryzophilus, <strong>and</strong> their use in an integrated<br />
management program. /. Econ, Entomol 94(4):963-970.<br />
Sundarapather, V. D. 1994. Analysis of preventive treatments for control o f rice water<br />
weevil in Texas. Ph.D. dissertation. Departm ent of Agricultural Econom ics, Texas<br />
A&M University, College Station, T X , 202 pp.<br />
Thompson, R. A., <strong>and</strong> S. S. Quisenberry, 1995. <strong>Rice</strong> plant density effect on rice water<br />
weevil infestation. Environ. Entomol 24(1): 19-23.<br />
Thom pson, R, A., S. S. Quisenberry, G. B. Trahan, A. M . Heagler, <strong>and</strong> G. Giesler.
Ríce Arthropod Pests <strong>and</strong> Their Management in the United States 455<br />
1994a. Water management as a cultural control tactic for the rice water weevil in<br />
southwest Louisiana. J. Bcon. Entomol 8 7 (l):2 2 3 -2 3 0 .<br />
Thom pson, R. A., S. S, Quisenberry, F. K. N’Guessan, A. M. Heagler, <strong>and</strong> G. Giesler.<br />
1994b. Planting date as a potential cultural method for managing the rice water<br />
weevil in water-seeded rice in southwest Louisiana. /. Econ, Entomol 8 7 (5 );1 3 1 8 -<br />
1324.<br />
Tsuzuki, H., <strong>and</strong> Y. Isogawa. 1976. The occurrence o f a new insect pest, the rice water<br />
weevil in Aichi prefecture. Plant Prot. 30:341.<br />
U S , Environmental Protection Agency. 1989. Notice of Preliminary Determination to<br />
Cancel Registration o f Carhofuran Products. Office of Pesticides <strong>and</strong> Toxic Substances.<br />
OPP-30000/48A; ERL. Special Review Position D ocum ent 2/3,48 pp.<br />
Way, M. 0 . 1990. Insect pest management in rice in the United States. In B. X Grayson,<br />
M. B. Green, <strong>and</strong> L. G. Copping (eds,), Pest Management in <strong>Rice</strong>. Elsevier Applied<br />
Science, London, pp. 181-189.<br />
Way, M. 0 . 2001. Insect management alternatives. In <strong>Rice</strong> Production Guidelines, Tex.<br />
Agrie. Ext. Serv. D -1253, pp, 31-43.<br />
Way, M . 0 „ <strong>and</strong> C, C. Bowling. 1991, Insect pests o f rice. In B. S. Luh (ed.). <strong>Rice</strong><br />
Production. Van Nostr<strong>and</strong> Reinhold, New York, pp. 237-268.<br />
Way, M. O., <strong>and</strong> R. G. Wallace. 1984, Spatial distribution o f adult rice water weevil<br />
feeding scars in Texas. Proc. <strong>Rice</strong> Tech. Wbrfc. Group 20:70.<br />
Way, M. 0 „ <strong>and</strong> R. G. Wallace. 1989. First record o f midge damage to rice in Texas,<br />
Southwest. Entomol 1 4 (l):2 7 -3 3 .<br />
Way, M. O., <strong>and</strong> R. G. Wallace. 1990. Residual activity o f selected insecticides for<br />
control o f rice stink bug. /. Econ. Entomol 83(2):591-595.<br />
Way, M. O., <strong>and</strong> R. G. Wallace. 1992. Evaluation o f control o f the RW W with the<br />
nematode Steinernema carpocapsae, 1989. Insectic. Acaric. Tests 17:256-257.<br />
Way, M . O., <strong>and</strong> R. G. Wallace. 1995a. Control o f rice water weevil with Karate, 1994,<br />
Arthropod Manag. Tests 20:229.<br />
Way, M. O., <strong>and</strong> R. G. Wallace. 1995b. Control o f ric§ water weevil with fipronil <strong>and</strong><br />
acephate, 1994. Arthropod Manag. Tests 20:228,<br />
Way, M . O., <strong>and</strong> R. G. Wallace, 1995c. Control o f rice water weevil with Naturalis-L,<br />
1994. Arthropod Manag. Tests 20:229-230.<br />
Way, M, O., <strong>and</strong> R. G. Wallace. 1996a. Control o f rice water weevil with Karate lEC ,<br />
1995. Arthropod Manag. Tests 21:282-283.<br />
Way, M. O., <strong>and</strong> R. G. Wallace. 1996b. Control o f rice water weevil with fipronil, 1995.<br />
Arthropod Manag. Tests 21:281-282.<br />
Way, M. O., <strong>and</strong> R. G. Wallace. 1996c. Control o f rice water weevil with Diniilin 25 W,<br />
1995. Arthropod Mamg. Tests 21:283-284.<br />
Way, M. O., <strong>and</strong> R. G. Wallace. 1997a. Control o f rice water weevil witli Karate in a<br />
dry-seeded, delayed flood culture, 1996. Arthropod Manag. Tests 22:302-303.<br />
Way, M. O., <strong>and</strong> R. G, Wallace. 1997b. Control o f rice water weevil with fipronil in a<br />
dry-seeded, delayed flood culture, 1996. Arthropod Manag. Tests 22:298.<br />
Way, M . 0 „ <strong>and</strong> R. G. Wallace, 1997c. Control o f rice water weevil with fipronil applied<br />
post-flood in a dry-seeded, delayed flood culture, 1996. Arthropod Manag. Tests<br />
22:299.<br />
Way, M. O., <strong>and</strong> R. G. Wallace. 1998a. Control o f rice water weevil with Karate <strong>and</strong><br />
ICIA0321 in a dry-seeded, delayed flood culture, 1997. Arthropod Manag. Tests<br />
23:265.
456 Produüion<br />
K^'<br />
Way, M. O., <strong>and</strong> R. G. Wallace, 1998b. Control of rice water weevil with Dim ilin 2L in<br />
a drill“seeded, delayed flood culture at Eagle Lake, 1997. Arthropod Manag. Tests<br />
23:266-267.<br />
Way, M. O., <strong>and</strong> R. G. Wallace. 1999a. Control o f rice water weevil witli Fury 1.5EC,<br />
Dimilin 2 L , Icon 6.2FS <strong>and</strong> Karate Z in a dry-planted, delayed flood culture, 1998.<br />
Arthropod Manag. Tests 24:277-278.<br />
Way, M . O., <strong>and</strong> R. G. Wallace. 1999b. Control o f rice water weevil with Karate<br />
Z tank-mixed with selected herbicides, 1998. Arthropod Manag. Tests 2 4 :2 7 5 -<br />
276.<br />
Way, M. O., <strong>and</strong> R. G. Wallace. 2000. Control o f rice water weevil with Novodor 3,<br />
1999. Arthropod Manag. Tests 25:296-297.<br />
Way, M. O., A. A. Grigarick, <strong>and</strong> S. E. Mahr. 1983. Effects o f rice plant density, rice water<br />
weevil damage to rice, <strong>and</strong> aquatic weeds on aster leafhopper density. Environ.<br />
Entomol. 12(3):949-952.<br />
Way, M. O., A. A. Grigarick, <strong>and</strong> S. E. Mahr. 1984. The aster leafliopper in California<br />
rice; herbicide treatm ent affects population density <strong>and</strong> iriduced infestations<br />
reduce grain yield. J . Econ. Entomol 77(4):936-942.<br />
Way, M . O., F. T, Turner, <strong>and</strong> J. K. Clark. 1985. The rice leaf miner, Hydrellia griseola<br />
(Fallen), a potential pest o f rice in Texas. Southwest. Entomol 8:186-189.<br />
Way,M. O., A. A. Grigarick, S, E. Mahr, M. J. Graze, <strong>and</strong> K. A. <strong>Smith</strong>. 1986. Evaluation<br />
of three drop traps for sampling aster leafhoppers in rice. J Econ. Entomol 79(6):<br />
1711-1713.<br />
Way, M . O., R. G. Wallace, <strong>and</strong> C. W. Bordelon. 1989. Aerial Application of Insecticides<br />
for Leafhopper Control in Ric^. Tex. Agric. Exp. Stn. P R -4682,6 pp.<br />
Way, M. O., A. A. Grigarick, J. A. Litsinger, F. Palis, <strong>and</strong> P. L. Pingali. 1991. Econom ic<br />
thresholds <strong>and</strong> injury levels for insect pests o f rice. In E. A. Heinrichs <strong>and</strong> T. A,<br />
Miller (eds.), <strong>Rice</strong> Insects: Management Strategies. Springer-Verlag, New York,<br />
pp. 67-105.<br />
Way, M. O., R, G. Wallace, K. Smitli, <strong>and</strong> R. M artin. 1992a. Control o f rice water weevil<br />
with nematodes, 1990. Insectic. Acarie. Tests 17:254-256.<br />
Way, M. O., R. G. Wallace, <strong>and</strong> K. <strong>Smith</strong>. 1992b. Evaluation o f two species o f nematodes<br />
for rice water weevil control, 1989. Insectic. Acaric. Tests 17:257-258.<br />
Way, M . O., R. G. Wallace, <strong>and</strong> J. Vawter. 1997. Control o f rice water weevil on<br />
drill-seeded rice with diflubenzuron at Eagle Lake, 1996. Arthropod Manag. Tests<br />
22:300-301.<br />
Way, M. O., R. G. Wallace, <strong>and</strong> J. Vawter. 1998. Control o f rice water weevil with Karate<br />
Z in a drill-seeded, delayed flood culture at Eagle Lake, 1997. Arthropod Manag.<br />
Tests 23:263-264.<br />
Wu, G. W., <strong>and</strong> L. T. Wilson. 1997. Growth <strong>and</strong> yield response o f rice to rice water<br />
weevil injury. Environ, Entomol 26(6):1191-1201.
Chopter<br />
3.7<br />
Ríce Weed Control<br />
A n d y K e n d ig<br />
University ofMissouri<br />
Portogeville, Missouri<br />
B ill W illia m s<br />
Louisiana State University<br />
St. Joseph, Louisianö<br />
C. W a y n e S m ith<br />
Texas A&M University<br />
College Station, Texas<br />
INTRODUCTION<br />
RICE WEEDS<br />
FLOODING<br />
Common Weed Control Strategies in Delayed-Flood <strong>Rice</strong><br />
Sequential Propanil Program<br />
Propanil Plus Residual Herbicides<br />
Delayed Preemergence Strategies<br />
Preemergence Strategies<br />
Common Weed Control Strategies in Continuously Flooded Ríce<br />
GENERAL AND AQUATIC WEED CONTROL IN ALL PRODUCTION SYSTEMS<br />
Salvage Weed Control<br />
Conservation Tillage <strong>and</strong> Preplant Burndown<br />
Red <strong>Rice</strong><br />
Future Red <strong>Rice</strong> Control<br />
Delayed Phyfotoxicity Syndrome<br />
OVERVIEW OF INDIVIDUAL RICE HERBICIDES<br />
Aciflurofen<br />
Bensulfuron<br />
Sentazón<br />
Bispyribac<br />
Carfentrazone<br />
Clefoxydim<br />
Clomazone<br />
Cyholofop<br />
Fenoxoprop<br />
Glufosinate<br />
Glyphosate<br />
Halosulfuron<br />
<strong>Rice</strong>: Origin, History, Technology, <strong>and</strong> Production, edited by C. Wayne <strong>Smith</strong><br />
ISBN 0-471-34516-4 © <strong>2003</strong> John Wiley & Sons, Inc.<br />
457
458 Production<br />
■‘1 '' Imazetliapyr<br />
B Í Molinete<br />
p ', ' Pendlmathalin<br />
Propanil<br />
pB.Ü ■<br />
1 '<br />
Quinclorac<br />
Thiobencarb<br />
P<br />
Triclopyr<br />
W. . 2,4-D<br />
I;-. ! ' REFERENCES<br />
INTRODUCTION<br />
<strong>Rice</strong> weed control can be complicated compared to weed control in other crops.<br />
There are numerous rules» which appear to conflict whenever one tries to generalize<br />
recommendations. The wide variety o f rice cultural methods also complicates weed<br />
control. However, for purposes o f weed control, cultural methods o f rice <strong>production</strong><br />
can be grouped into delayed flood (usually in association with drill seeding) <strong>and</strong><br />
continuous flood (including the variations of true permanent flood as well as pinpoint<br />
methods, where the soil remains anaerobic).<br />
Herbicide use patterns also are complex. The same herbicide may be used in<br />
distinctly different ways in the various cultures. For example, molinate (Ordram ) has<br />
four separate use patterns, which are listed in Table 3.7.1. Another example is triclopyr<br />
(Gr<strong>and</strong>st<strong>and</strong>), which is a relatively safe, broadleaf-controlling herbicide that can be<br />
used from the two-leaf stage through two or more weeks after flooding; however,<br />
applications within 36 hours of the flood can cause crop injury. Flushing (a temporary<br />
flood) improves the activity o f some herbicides <strong>and</strong> reduces the activity o f others.<br />
T A B LE 3.7.1.<br />
E x a m p le of C o m p le x H e rb ic id e U se P a tte rn s w ith th e H e rb ic id e M o lin a t e<br />
(O rd ra m a n d A rro so lo ]<br />
U se Pattern<br />
Preplant incorporated in continuously<br />
flooded rice<br />
Early postemergenee in continuously<br />
flooded rice<br />
Early postemergence in delayed flood<br />
rice, with propanil<br />
Postflood in delayed flood rice<br />
Description<br />
Molinate functions as a soil-active, preemergence<br />
residual herbicide.<br />
Molinate functions as a postemergence herbicide<br />
which is absorbed into weeds via the<br />
floodwater.<br />
Molinate functions as a postemergence contact<br />
herbicide; residual activity is limited unless a<br />
significant rain occurs within hours of<br />
application,<br />
MoUnate functions as a postemergence herbicide<br />
which is absorbed into weeds via tlie<br />
floodwater.
<strong>Rice</strong> Weed Control 459<br />
RICE WEEDS<br />
Barnyardgrass {Echinochloa crus-galli) <strong>and</strong> related species in California (early water-<br />
grass, E, oryzoides, <strong>and</strong> late watergrass or rice m im ic E. phyllopogoh) are the most<br />
com m on weeds in rice, with barnyardgrass being listed among the world’s 10 worst<br />
weeds. Barnyardgrass can be difficult to control; however, numerous herbicides are<br />
available.<br />
Several other rice weeds are the same dryl<strong>and</strong> weeds that normally infest cotton<br />
' <strong>and</strong> soybean fields, including broadleaf signalgrass {Brachiariaplatyphylla), nutsedge<br />
{Cyperus spp.), hemp sesbannia (often nicknamed coffeebean; Seshania exaltata),<br />
morningglories {Ipomoea spp.), com m on cocklebur {Xanthium strumarium), <strong>and</strong><br />
eclipta (Eclipta prostrata). These weeds are well adapted to wet <strong>and</strong> flooded conditions,<br />
but they do not require these conditions. Consequently, they can infest both<br />
rice <strong>and</strong> dryl<strong>and</strong> field crops.<br />
There are also aquatic <strong>and</strong> semiaquatic weeds that are unique to rice. These<br />
include Amazon <strong>and</strong> bearded sprangletop (Leptochloa panicoides <strong>and</strong> L faskularis,<br />
respectively), purple ammannia (often nicknamed redstem; Ammanma coccínea),<br />
ducksalad {Heteranthera limosa), roundleaf mudplantain {Heteranthera reniformis),<br />
<strong>and</strong> arrowhead species (Saggitaria spp.).<br />
It should be noted that m ost broadleaf <strong>and</strong> aquatic weed problems can be attributed<br />
to a lack o f com petition from the crop. In water-seeded, continuous-flood<br />
cultures, there is a 2- to 3 -week period with a flood but very little rice biomass to<br />
compete with weeds. For this reason, early infestations o f aquatic weeds are typically<br />
a problem in water-seeded rice. In delayed-flood rice, aquatic <strong>and</strong> broadleaf weeds<br />
typically infest areas where there were problems with the establishment o f the rice<br />
st<strong>and</strong>. These thin areas are similar to the early environment in continuous-flood<br />
systems: Aquatic weeds have the opportunity to grow in a flooded area with little<br />
interference from the rice crop.<br />
<strong>Rice</strong> has one particularly unique weed problem, red rice, which is the same genus<br />
<strong>and</strong> species as rice. Because it is the same species, tliere are no biochemical or other<br />
growth mechanism to provide for selective herbicidal control. Red rice would be less<br />
o f a weed problem if it did not have an off-color seed coat. The off color is undesirable<br />
to consumers. The milling process can remove the red color; however, its removal is<br />
expensive <strong>and</strong> time consuming. Producers face significant price penalties when selling<br />
red rice-contam inated rice.<br />
Although the primary problem is the unwanted color, red rice is competitive <strong>and</strong><br />
can cause direct yield reductions. It also has several weedy characteristics, including<br />
aggressive growth, seed shattering, reseeding potential, <strong>and</strong> seed dormancy.<br />
Although red rice <strong>and</strong> com mercial rice cultivars are classified as the same species,<br />
there are im portant com m on differences: Commercial rice cultivars have been bred<br />
for short stature, whereas red rice is 15 to 30 cm taller than white rice. Red rice plants<br />
also tend to be a lighter green color, as compared to white cultivars, <strong>and</strong> it also tends<br />
to have a very rough leaf edge that will “grab” your fingers if you rub downward.<br />
However, red rice <strong>and</strong> com mercial rice can cross-breed to produce intermediate types<br />
that are exceptions to the typical morphology.<br />
Currently, the best red rice control is rotation to other crops, where herbicides<br />
from those crops provide can selectively destroy red or volunteer rice. However, water-<br />
seeded, contiguously flooded rice offers some control, due to the fact that neither red
460 Production<br />
nor white rice will germinate through an anaerobic soil. In tliis system, a thin layer<br />
o f oxygen exists at the soil-water interface. This oxygen allows aerially seeded rice<br />
to germinate while red rice seed below the surface cannot germinate in the anaerobic<br />
environment, Unfortimately, a few red rice seeds are usually located on tlie soil surface<br />
<strong>and</strong> will germinate <strong>and</strong> contaminate the field.<br />
At this time, three herbicide-resistant rice systems are under development: imidazolinone-resistant,<br />
glufosinate-resistant, <strong>and</strong> glyphosate-resistant. These systems will<br />
control many rice weeds, but the key benefit is that a herbicide-resistant rice offers<br />
the potential for selective control of red rice growing with a commercial white<br />
cultivar.<br />
FLOODING<br />
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It is often stated that although rice has a high water requirement, flooding is not<br />
required for optimal crop growth. Instead, tlie flood is said to provide we6d control. In<br />
the United States, the flood is estimated to supply between 40 <strong>and</strong> 60% o f a crop’s weed<br />
control; more so with water-seeded, continuous-flood systems <strong>and</strong> less with dryseeded,<br />
delayed-flood systems. The importance o f the flood for weed control is further<br />
evidenced by the fact that in delayed-flood systems, most herbicide applications are<br />
made during the unflooded period.<br />
Although the flood is a key aspect o f weed control, it also provides im portant<br />
benefits for management of nitrogen <strong>and</strong> phosphorus fertility as well as providing a<br />
convenient way to satisfy the high water requirement.<br />
While the flood provides weed control, it should be understood that the floods<br />
primary action is to stop germination of weed seed. Although the flood will control<br />
some actively growing weeds, m ost weeds (even weeds that are not truly aquatic) will<br />
survive if they have grown taller than the depth o f the flood.<br />
Common Weed Control Strategies in Delayed-Flood <strong>Rice</strong><br />
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In the delayed-flood <strong>production</strong> system, most weeds must be controlled during the<br />
dry period. After rice is flooded, the flood works with interference from the rice<br />
crop combine to suppress weeds, In fact, overly-late flooding is a m ajor source o f<br />
weed control problems in delayed-flood rice. There are a wide range o f weed control<br />
programs in rice, especially with the recent availability o f the herbicide clomazone<br />
(Comm<strong>and</strong>). However, some programs can be generalized <strong>and</strong> are listed below.<br />
Sequential Propanil Program<br />
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Propanil selectively controls a wider variety o f rice weeds than does any other rice<br />
herbicide, Propanil is a postemergence, contact-type herbicide that, unfortunately,<br />
has no residual activity. Because it is a nontranslocated, contact-type herbicide, it can<br />
control only small weeds. Larger weeds, where meristems are protected <strong>and</strong> which<br />
may have some carbohydrate storage reserve, can survive propanil applications. Because<br />
propanil has no residual activity, new weeds can germinate, <strong>and</strong> consequently,<br />
repeated applications or additional residual herbicides are usually needed.
<strong>Rice</strong> Weed Control 461<br />
For numerous years, Stam 3 + 3 was a st<strong>and</strong>ard weed control program. Siam is<br />
the most com m on trade name for propanil <strong>and</strong> “3 + 3” referred to two sequential applications<br />
o f 3 qt/acre o f the 480-g/L liquid formulation (2.8 L/ha o f formulated product<br />
<strong>and</strong> 3.36 kg/ha o f active ingredient) o f propanil. In an ideal situation, rice would be<br />
planted into a weed-free seedbed, followed by rice <strong>and</strong> weed emergence <strong>and</strong> growth to<br />
a two- to three-leaf stage. Propanil would be applied at that time (roughly 2 weeks after<br />
planting), <strong>and</strong> weeds would be controlled. In roughly 2 m ore weeks, new weeds would<br />
have emerged (<strong>and</strong> would again be at tlie two- to three-leaf stage) <strong>and</strong> rice would be<br />
ready for a permanent flood. Propanil would be applied a second time <strong>and</strong> the flood<br />
would then be established as soon as practical to stop further weed emergence.<br />
The primary lim itation in this program was the interaction o f timely application<br />
<strong>and</strong> adverse weather. Propanil activity can also be limited by the cool temperatures<br />
that often occur early in the growing season. In addition, the requirement for two<br />
applications is somewhat inconvenient. Additionally, if the permanent flood was delayed,<br />
the grower was faced with the possibility o f additional weed emergence or<br />
additional, expensive herbicide applications.<br />
In the early 1990s, prop anil-resistant barnyardgrass became widespread throughout<br />
the mid-south. Surveys indicated that occurrence o f resistant grass was correlated<br />
with fields that grew rice, with little or no crop or herbicide rotation. The herbicide<br />
quinclorac was added to many programs (as described below) to control resistant<br />
grass, <strong>and</strong> more recently, cldmazone has been used for control.<br />
It should be noted that several insecticides interact with the enzyme aryl acyl<br />
amidase. This enzyme, which occurs in rice but not in weeds, detoxifies propanil <strong>and</strong><br />
therefore malces rice tolerant, Carbomate, organophosphate or methomyl insecticides<br />
block the function o f this enzyme <strong>and</strong> make rice extremely sensitive to propanil.<br />
Numerous precautions must be followed if rice is to be treated with these insecticides<br />
<strong>and</strong> propanil within the same 10-day period.<br />
Propanil Plus Residual Herbicides<br />
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The herbicides thiobencarb (Bolero), pendimethalin (Prowl), quinclorac (Facet), <strong>and</strong><br />
clomazone (Com m <strong>and</strong>) provide residual control o f unemerged rice weeds; however,<br />
they have limited postemergence activity (or no posteraergence activity in the case<br />
o f pendimethalin). Consequently, these herbicides are often mixed with propanil <strong>and</strong><br />
applied so that propanil controls the weeds that are present <strong>and</strong> the residual herbicide<br />
continues to control weeds until the flood can be established. This system has<br />
the advantage o f usually supplying a one-pass weed control program. Additionally,<br />
pendimethalin <strong>and</strong> thiobencarb injure rice when applied in a true, immediate-postplant,<br />
preemergence application. However, when applied later, rice is not injured;<br />
consequently, this application scheme improves the crop safety o f these herbicides.<br />
Delayed Preemergence Strategies<br />
As stated above, pendimethalin <strong>and</strong> thiobencarb can injure rice when applied in a<br />
true preemergence application. W hen rice seed first imbibes water, it can be injured<br />
if pendimethalin or thiobencarb has been applied <strong>and</strong> is present in the water. However,<br />
if the herbicide application is delayed until after rice seed imbibes water <strong>and</strong><br />
the germination process is initiated, little additional herbicide is imbibed <strong>and</strong> rice
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seed is not injured. For this reason, it is recommended that these two herbicides<br />
be applied after a significant rainfall or flush. Conversely, it is im portant that they<br />
be applied promptly since their postemergence activity is minimal. An application<br />
prior to weed emergence but soon after planting, followed by a significant rainfall<br />
or flush, is termed a delayed preemergence application. The herbicide quinclorac can<br />
be applied immediately after planting; however, its activity is somewhat better when<br />
applied using the delayed preemergence strategy.<br />
The advantages o f delayed preemergence programs with these herbicides are<br />
specific to the individual herbicides <strong>and</strong> weed problems. Pendimethalin offers very<br />
economical grass control <strong>and</strong> sprangletop control, thiobencarb offers control o f sprangletop<br />
<strong>and</strong> aquatic weeds, <strong>and</strong> quinclorac offers excellent grass <strong>and</strong> broadleaf control.<br />
Preemergence Strategies<br />
The recent registration o f the herbicide clomazone has caused a widespread change in<br />
rice weed control programs. Clomazone offers reliable, low-cost grass control along<br />
with the convenience o f a true immediate postplant preemergence application to dry<br />
soil. A significant lim itation to a delayed preemergence program is that tim ing is<br />
critical <strong>and</strong> often requires the use o f aerial application, as it is difficult to dry the soil<br />
enough after flushing so that ground application equipment can be used. Although<br />
quindorac is also available as a relatively broad-spectrum , preemergence program, its<br />
use remains largely as a propanil tank m ix or delayed preemregence application.<br />
Clomazone controls grasses primarily <strong>and</strong> is exceptionally weak for nutsedge<br />
control. Consequently, clomazone-based programs usually include a preflood application<br />
o f a broadleaf <strong>and</strong> nutsedge controlling treatm ent. In some instances, grass<br />
control may be incomplete in these cases; propanil-based products are often part o f<br />
the preflood application.<br />
Common Weed Control Strategies in Continuously Flooded <strong>Rice</strong><br />
In continuously flooded culture, the flood provides a high level o f control o f non-<br />
aquatic weeds. As with drill-seeded rice, numerous herbicides <strong>and</strong> weed control strategies<br />
may be used; however, preemergence thiobencarb <strong>and</strong> early postemergence use<br />
o f molinate <strong>and</strong> bensulfuron are especially com m on. As stated above, aquatic weeds<br />
can develop soon after flood but before rice is established <strong>and</strong> competitive.<br />
True continuously flooded rice is widespread in California. The California Environmental<br />
Protection Agency has not allowed the use o f several rice herbicides that are<br />
available in the mid-south. For these reasons, California rice producers relied heavUy<br />
on molinate <strong>and</strong> bensulfuron for weed control. In recent years, numerous instances of<br />
bensulfuron- <strong>and</strong> m olinate-resistant weeds have been discovered. Recently, propanil<br />
has become available in California.<br />
GENERAL AND AQUATIC WEED CONTROL IN ALL PRODUCTION SYSTEMS<br />
Traditional weed control programs that include propanil, quinclorac, thiobencarb,<br />
or bensulfuron control m ost com m on broadleaf weeds problems. However, as stated<br />
earlier, areas where rice st<strong>and</strong>s are poor can develop weed problems. There are several
<strong>Rice</strong> Weed Control 463<br />
popular programs (especially clomazone-based ones) which have little inherent broadleaf<br />
activity. Also, the use o f grass-only herbicides such as safened fenoxaprop <strong>and</strong><br />
cyhalofop may increase as these herbicides become available. Fortunately numerous,<br />
econom ical broadleaf herbicides are available. Broadleaf control usually involves the<br />
selection o f a herbicide treatm ent to m atch the particular weeds present. In many<br />
cases, Propanil is now being used more for the control o f broadleaf weeds while still<br />
controlling escaped grass. Preliminary research with the grass-only compounds has<br />
indicated that grass-control antagonism is possible when these herbicides are mixed<br />
with broadleaf herbicides.<br />
Jointvetch (Aeschynomene) species are somewhat troublesome <strong>and</strong> must be very<br />
small to be controlled by com m only used rice herbicides. However, triclopyr (Gr<strong>and</strong>st<strong>and</strong>)<br />
provides good control of jointvetch species. Collego (a product that is com <br />
prised of spores o f the fungus CoUetotnchum gloeosporioides f. sp. Aeschynomene)<br />
provides good control of N orthern Jointvetch (Aeschynomene virginica). The use o f<br />
Collego is limited because it does not control the closely related Indian jointvetch<br />
[Aeschynomene indica) <strong>and</strong> because it controls no other weeds. In m ost cases, jo in t<br />
vetch will be accompanied by several other weed species. The herbicide bispyribac<br />
(Regiment) is being developed <strong>and</strong> controls jointvetch along with a num ber of other<br />
weeds.<br />
Nutsedge species are a com m on rice weed problem <strong>and</strong> are adapted to wet <strong>and</strong><br />
aquatic environments. Although propanil, bentazon, <strong>and</strong> bensulfuron provide nutsedge<br />
control, their activity was somewhat limited <strong>and</strong> nutsedge was often difficult to<br />
control. The recent registration o f halosulfuron, which has excellent nutsedge activity,<br />
has simplified the control of nutsedge. However, the recent widespread use o f cloma-<br />
zone, which has essentially no nutsedge activity, has kept this weed as an im portant<br />
issue to rice producers,<br />
Sprangletop is a weedy grass that is troublesome in rice but which is not com <br />
mon to other crops. Sprangletop is well adapted to the aquatic environment. It has<br />
slight tolerance to propanil, some tolerance to molinate, bispyribac, <strong>and</strong> imazethapry<br />
<strong>and</strong> almost complete tolerance to quinclorac, A few sprangletop escapes are com <br />
mon following propanil treatments. Programs that include the herbicides clomazone<br />
pendimethalin, thiobencarb, or fenoxaprop usually provide adequate control.<br />
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Salvage Weed Control<br />
For numerous reasons (often, weather-related problems), com m on rice weed control<br />
programs can fail <strong>and</strong> allow a num ber o f weeds, especially grasses, to escape. Fortunately,<br />
several herbicide alternatives are available that provide acceptable control o f<br />
large, escaped grass. The herbicide fenoxaprop is often used to control larger, escaped<br />
barnyardgrass <strong>and</strong> sprangletop. A new version o f fenoxaprop, which contains a com <br />
pound that increases crop safety, provides good sprangletop control; however, control<br />
of large barnyardgrass is usually not adequate with the safened fenoxaprop.<br />
M olinate (typically as a granular formulation applied into floodwater) is another<br />
traditional salvage treatment. Activity is very slow; however, barnyardgrass growth is<br />
usually stopped, which allows a competitive advantage to rice. M olinate has limited<br />
sprangletop <strong>and</strong> broadleaf activity.<br />
Full rates of quinclorac plus propanil or quinclorac plus propanil-m olinate products<br />
are often used for salvage control o f weeds. These mixtures control many larger
464 Producíion<br />
grass <strong>and</strong> broadleaf weeds (sprangletop is an exception). Flooding within a week<br />
after application, or making the application into fioodwater, is im portant to assure<br />
adequate activity.<br />
The experimental herbicide bispryibac (Regiment) has shown potential for controlling<br />
large, escaped grass <strong>and</strong> broadleaf weeds, <strong>and</strong> the experimental herbicide<br />
cyhalofop (Clincher) has shown potential for postflood control o f large escaped grass.<br />
Conservation Tillage <strong>and</strong> Preplant Burndown<br />
M ost nonselective, nonresidual burndown herbicides are registered for use in conservation<br />
tillage rice. These herbicides function similarly in rice as in other crops.<br />
However, there are several unique use patterns in rice. Glyphosate (Roundup) is often<br />
used in a postplant burndown scenario <strong>and</strong> there is some rice tolerance up to the<br />
spiking stage. The spiking stage is when the coleoptile has emerged from the soil;<br />
however, the first true leaf is not exposed. However, spiking-stage applications are<br />
extremely risky <strong>and</strong> are not recommended. Glyphosate or paraquat (Gramoxone) are<br />
also used routinely in a tank mixture with delayed preemergence herbicides; however,<br />
again, it is critical that rice has not emerged. There is some potential for preplant<br />
use o f clomazone plus a burndown herbicide; however, to date, research has not<br />
determined if this earlier application will cause the residual weed control to fail before<br />
flooding.<br />
In red rice-infested areas, where growers are using a continuously flooded culture,<br />
paraquat is often used just ahead o f flooding to kill a final flush o f red rice.<br />
Although glyphosate usually provides acceptable red rice control, it can sometimes<br />
be hard to kill, especially when in the spiking stage,<br />
Triclopyr (Gr<strong>and</strong>st<strong>and</strong>) <strong>and</strong> 2,4-D are sometimes used in burndown treatments;<br />
however, it should be noted that rice is extremely sensitive to any 2,4-D residues in<br />
the soil. Consequently, the preplant intervals on the labels o f the particular 2,4-D<br />
products must be followed.<br />
Red <strong>Rice</strong><br />
As stated earlier, red rice is an especially d iffiailt weed problem in that it is taxonomically<br />
<strong>and</strong> biochemically the same as commercial rice cultivars. Therefore, rice<br />
herbicides cannot control red rice selectively without injuring the desirable cultivars.<br />
Currently, the best red rice control is rotation to soybean. Rotation to corn <strong>and</strong> cotton<br />
are also good choices; however, soybean herbicides provide growers witli the best <strong>and</strong><br />
widest range o f red rice control options. Chloroacetamide-type herbicides generally<br />
provide excellent control o f red rice. M etolachlor (Dual) or dimethenamid (Frontier)<br />
generally provide the best weed control. Flufenacet-based herbicides (Axiom <strong>and</strong><br />
D om ain) provide limited red rice control. Dinitroanaline herbicides (trifluralin <strong>and</strong><br />
pendimethalin), which are commonly used in soybean <strong>and</strong> cotton, suppress red rice<br />
but rarely provide adequate control In fact, pendimethalin is used routinely for weed<br />
control in rice.<br />
Even though chloroacetamide herbicides provide excellent preemergence control,<br />
they do not provide season-long control, <strong>and</strong> enough red rice typically germinates<br />
to reinfest the rest o f the field. Typically, red rice control in soybean also
<strong>Rice</strong> Weed Control 465<br />
involves application o f a selective grass herbicide. The best red rice herbicide from this<br />
group is quizolofop (Assure II). Clethodim (Select) is another good choice; however<br />
fluazifop (Fusilado <strong>and</strong> Fusion) <strong>and</strong> sethoxy^dim (Poast) are somewhat weaker <strong>and</strong><br />
sethoxydim has even been investigated for its potential use for barnyardgrass control<br />
in rice. Glyphosate-resistant soybeans are another good option for red rice control.<br />
Glyphosate is slightly weaker than quizalofop <strong>and</strong> clethodim; however» two glyphosate<br />
applications (which is the st<strong>and</strong>ard practice in m id-south soybeans) compensate for<br />
that weakness.<br />
One final herbicide option is available for red rice control, A special late-season<br />
label exists for the use o f a half-rate o f clethodim. This low rate does not kill red rice<br />
completely, but causes floral sterility in the heads o f tlie red rice.<br />
At least two consecutive years o f soybean herbicides are required to improve<br />
severe red rice infestations significantly. Rotation <strong>and</strong> sanitation are im portant in<br />
preventing the establishment or increase in slight infestations. The use o f high-quality<br />
seed will prevent the establishment o f red rice seed. Also, it is worthwhile to h<strong>and</strong>-<br />
rogue any small red rice infestations that are found in an otherwise clean field.<br />
In rice, red rice is controlled by the use o f the water-seeded, continuous-flood<br />
methods, as described earlier. <strong>Rice</strong> (whether red rice or a commercial cultivar) will not<br />
emerge through an anaerobic soil. This gives rise to the com m on phrase; “<strong>Rice</strong> will<br />
emerge through soil or water but not both.” A thin layer o f oxygen at the soil-w ater<br />
interface allows rice seed to germinate from the soil surface. W ith continuous-flood<br />
systems, red rice seeds that are in the soil cannot germinate, while commercial rice is<br />
left on the soil surface, where it can germinate. Continuous-flood systems provide<br />
good suppression o f light to moderate red rice infestations. However, control will<br />
not be complete, as there are always a few red rice seeds on top o f the soil that can<br />
germinate along with the regular cultivar. Consequently, permanent-flood systems<br />
will provide good but not complete red ríce control. W ith pinpoint flood methods it<br />
is essential that the flood be removed <strong>and</strong> replaced quickly (at least within 3 days).<br />
W ith longer pinpoint drains, m ore oxygen diffuses into the soil <strong>and</strong> m ore red rice<br />
can germinate. At-planting applications o f thiobencarb <strong>and</strong> molmate are often recommended,<br />
as these herbicides provide additional red rice control. Pregermination<br />
protects the commercial cultivar from the herbicides.<br />
It also has been determined that not tilling the field (which would bury red rice<br />
seed) <strong>and</strong> flooding it for the winter will allow waterfowl to eat significant quantities<br />
of red rice seed. It is im portant to use a roller-type implement to make occasional<br />
30-m -long "l<strong>and</strong>ing zones” for waterfowl.<br />
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Future Red <strong>Rice</strong> Control<br />
Through genetic engineering <strong>and</strong> conventional breeding, three herbicide-resistant<br />
weed control systems are currently under development. <strong>Rice</strong> lines have been developed<br />
which are resistant to glufosinate, imazethapyr, <strong>and</strong> glyphosate. Although all<br />
o f these systems have the potential to control many com m on rice weeds, tliey are<br />
especially useful because the herbicide tolerance offers the opportunity to control<br />
red rice selectively in com mercial rice. At the time o f writing, commercial use o f the<br />
imazethapyr system was anticipated for 2002, <strong>and</strong> com m ercial use o f the glufosinate<br />
system was anticipated for approximately 2004. A possible date for com mercial use o f<br />
the glyphosate system is unknown.<br />
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A key concern with all of these systems is that since red <strong>and</strong> com mercial rice can<br />
interbreed, herbicide resistance could be transferred into red rice. In the unfortunate<br />
event o f glufosinate or imazethapyr resistance spreading to red rice via outcrossing,<br />
those technologies would no longer be available for red rice control in rice. Fortunately,<br />
glufosinate <strong>and</strong> imazethapyr are not used for the purpose o f red rice control<br />
in rotational crops. However, glyphosate is a valuable red rice control in rotational<br />
crops. Consequently, if outcrossing were to convey glyphosate resistance to red rice,<br />
control options would be lost in both the rice crop <strong>and</strong> in rotational crops. For this<br />
reason the future o f the glyphosate system is uncertain, due to outcrossing concerns. It<br />
has been suggested tliat glyphosate-resistant rice would be used only for general weed<br />
control in California, which has virtually no red rice. The possibility o f inserting the<br />
glyphosate-resistance gene into cytoplasmic DNA has also been discussed as a way to<br />
prevent outcrossing of resistance; however, it is unclear if the red rice traits would be<br />
carried into glyphosate-resistant rice in the event o f a cross.<br />
To date, research has shown that outcrossing is very limited <strong>and</strong> may be further<br />
limited in the case where red rice somehow survives herbicide treatm ent but is significantly<br />
injured <strong>and</strong> delayed in its pollination period. However, only a few outcrossing<br />
events could quicldy result in a large population of resistant types if there were no<br />
crop or herbicide rotation. There are preliminary indications that herbicide-resistance<br />
outcrossing has occurred in some controlled, worst-case experiments.<br />
Delayed Phyfotoxicity Syndrome<br />
In the m id-1990s, there was an outbreak o f rice that showed damage from growthregulating<br />
types o f herbicides (abnorm al growth, twisting o f the whorl, <strong>and</strong> the splitting<br />
o f sheaths with the stem looping outward). However, these symptoms were not<br />
associated with any recent herbicide application. However, the symptoms were associated<br />
with certain herbicides that had been applied several weeks earlier. This delay has<br />
given rise to the current, unofficial term delayed phytotoxicity syndrome. Research has<br />
determined that under extended anaerobic conditions, areas with significant decaying<br />
biomass (such as low spots in continuous, no-till rice with crop stubble), a fungus can<br />
develop which metabolizes m ost rice herbicides <strong>and</strong> creates a new compound that is<br />
injurious to rice. The herbicides must have a chlorinated ring structure. This includes<br />
all currently registered rice herbicides with the exception o f bensulfuron, bentazon,<br />
<strong>and</strong>halosulfuron. Should the problem occur in large areas o f the field, the only current<br />
solution is to drain the field <strong>and</strong> allow it to dry until cracks appear in the soil; This<br />
will result in the loss o f nitrogen fertility <strong>and</strong> possible new germination o f weeds. If<br />
the problem exists only in a small area (such as a depression), it is unlikely to spread,<br />
<strong>and</strong> econom ics would suggest that the grower accept the yield loss in the small area<br />
as opposed to risking fertility or weed control losses in the entire field.<br />
OVERVIEW OF INDIVIDUAL RICE HERBICIDES<br />
Adflurofen<br />
Aciflurofen is sold as Blazer or as a package m ix with bentazon which is named Storm.<br />
It is used primarily for pre- or postflood control o f broadleaf weeds <strong>and</strong> is notably<br />
good on Hemp sesbania.
<strong>Rice</strong> Weed Control 467<br />
Bensulfuron<br />
Bensulfuron is sold as Londax <strong>and</strong> is also sold in package mixes with propanil. It<br />
has three distinct use patterns. In continuously flooded rice, it is frequently used for<br />
control o f aquatic weeds shortly after rice is established. In delayed flood rice it may<br />
be used postflood for aquatic weeds. In both situations, the herbicide usually enters<br />
weed tissue via the floodwater. Consequently, it is im portant to have a deep flood<br />
established <strong>and</strong> avoid pumping water for approximately 7 days after application. In<br />
delayed-flood rice, bensulfuron has also been used shortly ahead o f flooding in tank<br />
mixtures with propanil-type products, primarily for control o f nutsedge.<br />
Sentazón<br />
Bentazon is sold as Basagran or as a package m ix with aciflurofen named Storm.<br />
Historically, it was used for control o f smartweed (Polygonum species) <strong>and</strong> nutsedge<br />
species as well as other broadleaves, such as cocldebur. Presently, nutsedge <strong>and</strong> sm artweed<br />
are typically controlled witli products o f other chemical content, including<br />
bensulfuron, halosulfuron, <strong>and</strong> carfentrazone.<br />
Bispyribac<br />
At the present time, bispyribac is an experimental herbicide with the proposed name<br />
Regiment, A key feature of bispyribac is that it controls relatively large barnyardgrass<br />
as well as other com m on grass <strong>and</strong> broadleaf weeds. It is anticipated that bispyribac<br />
will become an option for pre- or postflood control o f weeds that escaped earlier<br />
applications.<br />
Carfentrazone<br />
Carfentrazone is sold as Aim in the mid-south <strong>and</strong> as Shark in California. In the<br />
mid-south, carfentrazone is used primarily in pre- <strong>and</strong> postflood applications for<br />
control of com m on broadleaf weeds, Carfentrazone provides fairly good control o f<br />
smartweed, which can be difficult to control with other herbicides. In California, carfentrazone<br />
is applied at significantly higher rates <strong>and</strong> affects weeds by acting through<br />
the floodwater.<br />
Clefoxydim<br />
clefoxydim is an experimental herbicide witli the proposed name Aura. At the time<br />
o f writing, it was unknown if this herbicide would be further developed <strong>and</strong> sold. It is<br />
a postemergence herbicide that controls only grass species. A possible use for clefoxydim<br />
is in a tank m ixture or a program with quinclorac. Quinclorac <strong>and</strong> clefoxydim<br />
are both made by BASF. Quinclorac has poor sprangletop activity, whereas clefoxydim<br />
has good activity. Combining the two herbicides would control most com m on grass<br />
<strong>and</strong> broadleaf weeds.
468 Production<br />
Clomazone<br />
Clomazone is currently sold as Comm<strong>and</strong>. Clomazone was registered recently for rice<br />
weed control <strong>and</strong> at the tim e of this writing had significantly altered traditional rice<br />
weed control programs, Clomazone provides preemergence control o f grass weeds<br />
but controls very few broadleaf weeds <strong>and</strong> sedges. However, its residual activity is<br />
above average, it is convenient to use, <strong>and</strong> it is currently among the lowest-cost rice<br />
herbicides. If the residual herbicides used in rice were ranked, clomazone would probably<br />
be the second-most-effective <strong>and</strong> reliable herbicide o f the four that are presently<br />
available. The other three herbicides need to be (or are required to be) applied delayed<br />
preemergence or in a tank mixture with propanil, whereas clomazone can be applied<br />
conveniently in an immediate-post-plant, true-preemergence application. The current<br />
price of clomazone is less than 50% o f that o f quinclorac <strong>and</strong> thiobencarb.<br />
For the three reasons cited above, clomazone has been widely adopted by rice<br />
producers, <strong>and</strong> weed control strategies have shifted largely to preemergence clomazone<br />
followed by an appropriate broadleaf-controlling herbicide. Clomazone’s weakness<br />
on nutsedges has increased the use o f halosulfuron <strong>and</strong> bensulfuron as preflood<br />
cleanup treatments, On occasion, clomazone will provide incomplete grass control,<br />
<strong>and</strong> for that reason, propanil is often applied <strong>and</strong> is retaining its status as a key rice<br />
herbicide.<br />
Cyhalofop<br />
Cyhalofop is an experiential herbicide with the proposed name o f Clincher. It is a<br />
postemergence herbicide that only controls grass species. A possible use of cyhalofop<br />
is grass control in rice fields that are adjacent to broadleaf crops such as cotton. Cotton<br />
<strong>and</strong> soybeans are sensitive to a number o f rice herbicides, most notably propanil <strong>and</strong><br />
quinclorac. Research has also shown promise for cyhalofop to be used for postflood<br />
salvage o f large barnyardgrass.<br />
Fenoxaprop<br />
Fenoxaprop is sold as W hip 360 <strong>and</strong> is also com bined with a safening compound<br />
(isoxadifen) as the product <strong>Rice</strong>star. The Whip formulation is used for pre- <strong>and</strong><br />
postflood salvage o f large barnyardgrass as well as sprangletop control. The Whip<br />
formulation can cause severe rice injury if growing conditions are less than optiinal<br />
(recent flooding from rain, or permanent flood, cool temperatures, cloudy weather,<br />
etc.). The safening com pound greatly improves tlie crop safety o f the <strong>Rice</strong>star formulation;<br />
however, <strong>Rice</strong>star is not as strong on large grass weeds as is W hip 360. The<br />
<strong>Rice</strong>star product may be used for grass control next to broadleaf crops such as cotton<br />
<strong>and</strong> for sprangletop control.<br />
Glufosinate<br />
Glufosinate (Liberty) is currently being developed along with genetically engineered<br />
glufosinate resistant rice. Glufosinate is a nonselective herbicide that is often described<br />
as having activity intermediate to that o f paraquat <strong>and</strong> glyphosate (Glufosinate is
<strong>Rice</strong> Weed Control 469<br />
moderately fast— causing symptoms within a day— <strong>and</strong> will control weeds larger than<br />
can be controlled with paraquat but will not translocate extensively so that perennial<br />
weeds can be controlled as they are with glyphosate.)<br />
Although glufosinate appears to provide good control o f m ost grass <strong>and</strong> broadleaf<br />
weeds, the m ost notable attribute is drat this herbicide system could provide<br />
selective control o f red rice. Postemergence grass control is adequate but not strong.<br />
A key concern with herbicide-tolerant crops is the potential for herbicide-resistant<br />
crops to cross-breed with red rice, thus conferring the herbicide resistance into the<br />
weedy species.<br />
Glyphosate<br />
Glyphosate is currendy sold as a number o f products but is well known by its <strong>origin</strong>al<br />
trade name, Roundup. Glyphosate-resistant rice lines have been developed <strong>and</strong> have<br />
undergone a limited amount of testing. Red rice <strong>and</strong> general weed control were good.<br />
As stated above, the issue o f outcrossing is especially im portant with this system, as<br />
the herbicide is a valuable red rice control option in rotational crops.<br />
The future o f this system is uncertain. It has been proposed that die system<br />
win only be available in California, as there is very little red rice there. It has also<br />
been proposed that the glyphosate-resistance gene be inserted into cytoplasmic DNA<br />
or that a sterility gene be linked <strong>and</strong> inserted with the glyphosate resistance gene.<br />
However, at this tim e, all o f these possibilities are speculation.<br />
Halosulfuron<br />
Halosulfuron is a newer broadleaf <strong>and</strong> nutsedge herbicide that is typically applied<br />
shordy before flood flooding in delayed-flood, drill-seeded rice. Nutsedge activity has<br />
been excellent, <strong>and</strong> general broadleaf weed control has also been good.<br />
Imazethapyr<br />
Imazethapyr is currently being developed along with an imazethapyr-resistant rice<br />
that was produced via m utation breeding techniques, Imazethapyr is best loiown<br />
as the soybean herbicide Pursuit; however, Newpath is the currently planned name<br />
for this herbicide in imazethapyr-resistant (or Clearfield) rice. As with glufosinate-<br />
<strong>and</strong> glufosinate-resistant rice, selective red rice control is a highlight. Current results<br />
indicate that on silt-loam soils, an incorporated or preemergnece application followed<br />
by a postemergence application will be needed for acceptable red rice <strong>and</strong> grass control.<br />
On some clay soils, soil applications may provide poor results, <strong>and</strong> sequential<br />
postemergence applications may be needed. Imazethapyr provides poor control o f<br />
hemp sesbania <strong>and</strong> jointvetch species, <strong>and</strong> consequently, an additional herbicide will<br />
be added to the overall weed control program for control o f those weeds.<br />
Molinnfe<br />
Molinate is sold as both Ordram <strong>and</strong> as a package mixture with propanil called Ar-<br />
rosolo. As indicated in the introduction, molinate is used in a wide variety o f use
470 Prodiiction<br />
patterns, including preplant incorporated early postemergence into a flood, early<br />
postemergence in delayed-flood rice <strong>and</strong> postflood in delayed-flood rice. The herbicide<br />
functions as a preemergence (preemergence strictly defined as before weed<br />
emergence), a postemergence contact herbicide, <strong>and</strong> a floodwater-active herbicide in<br />
these various use patterns.<br />
Pendimethalin<br />
Pendimethalin (Prowl) can be used in two possible methods. Pendimethalin can be<br />
used delayed preemergence to provide low-cost preemergence grass control. Timing<br />
is extremely critical, as an immediate-post-plant, true-preemergence application to<br />
dry soil is lUcely to cause severe rice injury. If the rice seed initially imbibes water containing<br />
a significant amount o f pendimethalin, injury can be severe. However, if rice<br />
seed are allowed to imbibe herbicide-free water, before pendimethalin is applied, the<br />
uptalte of pendimethalin into the seed is reduced greatly <strong>and</strong> the injuj;y risk is reduced.<br />
If the application is delayed too much <strong>and</strong> grasses have emerged, pendimethalin<br />
has essentially no postemergence activity for control. W hen pendimethalin is used<br />
successfully in a delayed preemergence program, broadleaf herbicides are typically<br />
applied close to the time o f permanent flood. Although this use o f pendimethalin can<br />
provide low-cost grass control, it is also one o f the less reliable grass control methods.<br />
Pendimethalin is also frequently used in tank mixture with propanil, where propanil<br />
provides postemergence control o f existing weeds <strong>and</strong> then the pendimethalin<br />
provides residual control o f further grass emergence. In many cases, further germination<br />
o f broadleaf weeds wrU be limited, <strong>and</strong> a single application o f pendimethalin<br />
<strong>and</strong> propanil will provide complete weed control. However, further applications of<br />
low-cost broadleaf-controlling herbicides are sometimes needed.<br />
Propanil<br />
Propanil is currently sold via a number of different product names. It is m ost com <br />
monly known as Stam, which is its <strong>origin</strong>al trade name. This herbicide was thoroughly<br />
described earlier, as it remains a mainstay of weed control rice <strong>production</strong> by providing<br />
selective control o f most rice weeds. Propanil is a fast-acting, postemergence<br />
contact herbicide that translocates little <strong>and</strong> has no residual activity. Thus it will<br />
control only small, actively growing weeds. Propanil-based weed strategies are based<br />
on either repeated sequential applications followed by flooding, or tank mixtures of<br />
propanil with residual herbicides.<br />
Quinclorac<br />
Q uindorac is sold as the product Facet. Quinclorac has the typical complicated use<br />
patterns of most rice herbicides. It can be used preemergence, delayed preemergence,<br />
postemergence alone, postemergence in tank mixtures, <strong>and</strong> postflood. Q uinclorac<br />
controls many com m on grass <strong>and</strong> broadleaf weeds in rice but can be weak on<br />
smartweed <strong>and</strong> nutsedge species <strong>and</strong> has virtually no effect on sprangletop.<br />
Its most com m on use pattern is in an early postemergence tank mixture with<br />
propanil-based products. Quinclorac probably provides the best residual grass <strong>and</strong>
<strong>Rice</strong> Weed Control 471<br />
broadleaf activity o f any rice herbicide; however, because o f this attribute, it is among<br />
the more expensive rice herbicides. Its second-m ost-com m on use pattern is probably<br />
pre- <strong>and</strong> postflood salvage o f large, escaped grass <strong>and</strong> broadleaf weed control.<br />
During most o f the 1990s, quinclorac was used extensively in areas that had propanil-<br />
resistant barnyardgrass. Unfortunately, there are now a few isolated areas that contain<br />
barnyardgrass that is resistant to both propanil <strong>and</strong> quinclorac.<br />
True im mediate-post-plant preemergence use is effective but is used on a very<br />
limited scale. Delayed preemergence treatments, especially tank mixtures with pen-<br />
dunethalin or thiobencai'b (for added sprangletop control), are also com m on. Q uinclorac<br />
wiU provide postemergence control o f very small grass <strong>and</strong> broadleaf weeds<br />
<strong>and</strong> can also provide weed control when applied postflood. Quinclorac drift has been<br />
implicated as causing widespread drift damage to com mercial tomato <strong>production</strong> in<br />
Arkansas.<br />
Thiobencarb<br />
Thiobencarb is sold as Bolero in the mid-south <strong>and</strong> Abolish in California. It has<br />
several complex use patterns, a trait typical to rice herbicides. In continuously flooded<br />
rice, thiobencarb can be applied preflood, preplant, preemergence to weeds. The label<br />
states that the flood should be delayed by 24 hours after application. Then seed must<br />
be pregerminated, as the thiobencarb can be very injurious to dry rice that is seeded<br />
into water. Thiobencarb can also be applied to the soil at the tim e o f a pinpoint drain.<br />
In delayed flood rice, thiobencarb can be applied delayed preemergence. W ith preemergence<br />
applications to dry soil, rice seed absorbs an injurious quantity o f thiobencarb<br />
when it first imbibes water. However, in the delayed preemergence scenario, the<br />
seed has already imbibed a significant quantity o f water <strong>and</strong> imbibes relatively little<br />
thiobencarb when it is applied later, Thiobencarb is also applied postemergence in<br />
tank mixtures with propanil. The primary benefits to thiobencarb are sprangletop<br />
activity <strong>and</strong> residual control o f several broadleaf <strong>and</strong> aquatic weeds. Weaknesses in <br />
clude broadleaf signalgrass <strong>and</strong> the requirement that the soil be mainlined in a state<br />
o f optimal moisture, without cracking.<br />
Triclopyr<br />
Triclopyr is sold as the herbicide Gr<strong>and</strong>st<strong>and</strong>. It is a broadleaf-controlling herbicide<br />
that is most often applied shortly before flood, although it can be applied early postemergence<br />
as well as postflood. The herbicide has good crop safety except when rice<br />
is flooded within approximately 36 hours of application. W hen applied within 36<br />
hours o f flooding, crop injury can occur. Triclopyr controls m ost broadleaf weeds<br />
but is notably effective on alligatorweed <strong>and</strong> jointvetch species. Triclopyr can be wealc<br />
on hemp sesbania; however, a tank mixture with propanil is often used to improve<br />
sesbania control.<br />
2,4-D<br />
The herbicide 2,4-D is sold under numerous trade names. In the 1970s <strong>and</strong> 1980s<br />
it was com m only used for broadleaf weed control. The herbicide is effective but
i i î i :<br />
lliir<br />
Il i! i:<br />
II-<br />
472 Production<br />
has a very narrow window o f safe application. The herbicide may be applied from<br />
the time of internode differentiation until the first internode is 1.25 cm long. This<br />
translates to an approximate 7~day period. These growth stages are not outwardly<br />
visible <strong>and</strong> require careful scouting to identify. This herbicide is one’o f several reasons<br />
for the development o f D D -50 predictive growth models> as these growth models<br />
provide reasonably accurate estimates o f when the grower should check for internode<br />
differentiation <strong>and</strong> consider 2,4-D applications.<br />
Relatively little 2j4~D is now used on rice since triclopyr is now available <strong>and</strong><br />
triclopyr offers both improved crop safety <strong>and</strong> a greatly reduced risk to adjacent crops,<br />
especially cotton. Cotton is extremely sensitive to 2,4-D, some formulations tend to<br />
be volatile, <strong>and</strong> aerial application can increase the drift potential. Many states prohibit<br />
the use of 2,4-D within a mile of cotton fields.<br />
REFERENCES<br />
HiUiler, C. A. (editor). 1999. Louisiana <strong>Rice</strong> Production H<strong>and</strong>book, Louisiana State<br />
Univefsity Agriculturdl Center publication 2321,1 1 6 pp.<br />
Klosterboer, A. (editor). 2001.2001 Texas <strong>Rice</strong> Production Guidelines. Texas Agricultural<br />
Extension Service publication D -1253. 62 pp.<br />
Slayton, A. A. (editor). 2001. Arkansas <strong>Rice</strong> Production H<strong>and</strong>book. University o f<br />
Arkansas Cooperative Extension Service publication M P -1 9 2 .126 pp.<br />
Street, J. E. <strong>and</strong> T. C. Miller. 2000. Mississippi <strong>Rice</strong> Growers Guide. Mississippi State<br />
University Extension Service publication 2255. 99 pp.
C h a p t e r<br />
3.8<br />
<strong>Rice</strong> Marketing<br />
G a il L C ra m e r<br />
Agricultural Economics<br />
Louisiana State University<br />
Baton Rouge, Louisiana<br />
K e n n e th B. Y o u n g a n d Eric J. W n ile s<br />
Agricultural Economics<br />
University of Arkansas<br />
Fayetteville^ Arkansas<br />
INTRODUCTION<br />
U.S. <strong>Rice</strong> Supply <strong>and</strong> Dem<strong>and</strong> Conditions<br />
<strong>Rice</strong> Policy Background<br />
ROUGH RICE MARKETING SYSTEM<br />
Channels<br />
<strong>Rice</strong> Futures <strong>and</strong> Options Markets<br />
<strong>Rice</strong> Price Relationships<br />
PROCESSED RiCEMARKETiNG SYSTEM<br />
Channeis<br />
<strong>Rice</strong> By-Product Marketing<br />
<strong>Rice</strong> Marketing Margins<br />
Competitiveness of U.S. <strong>Rice</strong><br />
INTERNATIONAL RICE MARKET<br />
Characteristics of the World <strong>Rice</strong> Market<br />
U.S. <strong>Rice</strong> Sector Projections<br />
SUMMARY AND CONCLUSIONS<br />
REFERENCES<br />
INTRODUCTION<br />
U.S. <strong>Rice</strong> Supply <strong>and</strong> Dem<strong>and</strong> Conditions<br />
U.S. rice <strong>production</strong> <strong>and</strong> milling activity are concentrated in four regions: (1) Arkansas<br />
Gr<strong>and</strong> Prairie, (2) Mississippi River Delta (including part o f Arkansas, Mississippi,<br />
Missouri, <strong>and</strong> northeastern Louisiana), (3) the Coastal Plains o f Texas <strong>and</strong> Louisiana,<br />
<strong>and</strong> (4) the Sacramento Valley of California (Figure 3.8.1). Total U.S. <strong>production</strong><br />
<strong>Rice</strong>; Origin, History, Technology, <strong>and</strong> Production, edited by C, Wayne <strong>Smith</strong><br />
ISBN 0-471-34516-4 © <strong>2003</strong> John Wiley & Sons, Inc.<br />
473
474 Production<br />
Farm<br />
<strong>production</strong><br />
(8.5)<br />
Carry-out<br />
rough rice<br />
stocks<br />
(1.0)<br />
T T<br />
Milled rice __ ^^ Food<br />
imports<br />
use<br />
(0.5) (3.2)<br />
Processed<br />
food use<br />
(1.2)<br />
Rough ríce<br />
supply<br />
(9.8)<br />
Domestic<br />
milled rice<br />
supply<br />
(8.6)<br />
Domestic<br />
milled rice<br />
use<br />
(4.8)<br />
Brewer's<br />
use<br />
(0.7)<br />
Carry in<br />
stocks<br />
(1.3)<br />
Seed use<br />
(0.2)<br />
Milled rice<br />
exports<br />
(2 .6 )<br />
Residua!<br />
use/losses<br />
(0.2)<br />
Figure 3.8.1. U.S. rice market chon neis with estimoted 1997-1998 flows {million metric tons<br />
rough rice equivalent).<br />
increased from 24 to 210 million hundredweight (cwt) from 1938 to 1999 (Table<br />
3.8.1). Arkansas <strong>and</strong> California are tlie two dominant rice states, accounting for 46 <strong>and</strong><br />
19% o f 1999 <strong>production</strong>, respectively. The five southern U.S. states produce mostly<br />
long-grain rice (about 84% o f total U.S. rice <strong>production</strong> in 1999). The remaining state<br />
of California produces mostly medium-grain rice. Although rice is a m ajor crop in a<br />
few states, such as Arkansas, it comprised less than 1% of the total cropl<strong>and</strong> harvested<br />
in the United States in 1999.<br />
The U.S. domestic market for rice has been a growing market in recent years.<br />
Increased U.S. rice consumption is attributed to Asian <strong>and</strong> Hispanic immigrants <strong>and</strong><br />
development of new rice products <strong>and</strong> marketing (Wailes et al., 2000). Until 1990,<br />
over half of U.S. <strong>production</strong> was exported, but the domestic market utilized 52% o f the<br />
T A B U 3.8.1.<br />
R o u g h R ice P ro d u c tio n b y S to le [M illio n H u n d re d w e ig h t ( % o f Total)]<br />
State 1938 1963 1988 1999<br />
Arkansas 4.4 (19) 18.3 (26) 64.7 (41) 97.0 (46)<br />
California 3.8 (16) 14.0 (20) 29.5 (18) 39.0 (19)<br />
Louisiana 9.3 (39) 16.9 (24) 24.1 (15) 30.8 (15)<br />
Texas 6.2 (26) 18.9 (27) 23.3 (15) 15.6 (7)<br />
Mississippi 1.9 (3) 13.8 (9) 18.2 (9)<br />
Missouri 0.2 (0) 4.2 (3) 9.9 (5)<br />
U.S. total 23.6 (100) 70.3 (100) 159.5 (100) 210.5 (100)<br />
Source: Data from Econom ic Research Service, various issues.
<strong>Rice</strong> Marketing 475<br />
total U.S. <strong>production</strong> between 1996 <strong>and</strong> 1998. <strong>Rice</strong> im ports to the United States have<br />
been increasing to compete in the growing domestic market, supplying 9% o f domestic<br />
dem<strong>and</strong> in 1999. Im ports have been mostly specialty rice, especially aromatic highquality<br />
jasm ine or basm ati types that are not produced competitively in die United<br />
States. Total U.S. rice supply in the 1997-1998 marketing year in rough rice equivalent<br />
was 215.5 million hundredweight, including 27.2 million hundredweight beginning<br />
stocks, 178.9 million hundredweight <strong>production</strong>, <strong>and</strong> 9.4 million hundredweight im <br />
ports (USDA-ERS, 1998). A stock-to-use ratio below 15% generally is considered a<br />
tight stock situation, contributing to a relatively strong market price.<br />
<strong>Rice</strong> Policy Background<br />
The U.S, rice industry has been a m ajor beneficiary of government programs in the<br />
past, beginning with the first farm program, the Agricultural Adjustment Act (AAA),<br />
in 1933. The objective o f the 1933 AAA was to m aintain the purchasing power o f farm<br />
commodities at the 1910-1914 level through a m ix o f supply controls <strong>and</strong> processing<br />
taxes, a concept referred to as parity. Although tlie 1933 AAA program was not implemented<br />
at that time, this price support concept was retained as a goal in subsequent<br />
farm programs.<br />
The Agricultural Adjustment Act o f 1938 provided nonrecourse loans for rice,<br />
referendums for marketing quotas, acreage allotments, <strong>and</strong> direct payments to bring<br />
producer prices up to parity if funds were appropriated. <strong>Rice</strong> acreage allotments<br />
subsequently were suspended because o f World War II until 1950. Use o f marketing<br />
quotas <strong>and</strong> acreage allotments did not becom e im portant until 1955-1973 to control<br />
surplus stoclcs. A national acreage allotment o f 1.65 million acres was imposed from<br />
1956 to 1961, then increased gradually to 2.8 million acres from 1962 to 1968.<br />
The <strong>Rice</strong> Production Act o f 1975 shifted rice <strong>production</strong> control from quotas<br />
<strong>and</strong> allotments to greater market orientation. Farmers had the choice o f planting<br />
above tlieir allotments if they were wiUing to give up program benefits. A target price<br />
was established for the 1976 crop, providing direct deficiency payments as an incentive<br />
for producers to control their rice acreage. The deficiency payments were based<br />
on the difference between the August-December average farm price <strong>and</strong> the target<br />
price. The 1975 farm bill provided for annual set-asides <strong>and</strong> payment limitations.<br />
The Food Security Act (FSA) o f 1985 added a marketing loan program provision for<br />
rice producers. This legislation, along with deficiency payments, provided additional<br />
income to rice producers. Government rice program payments reached a peak in<br />
1986, comprising 64% o f rice producers’ net income.<br />
Government assistance also supported rice exports, particularly over the period<br />
1983-1994 (Table 3.8,2). Export credit guarantees to assure repayment o f loans to<br />
finance the exports were m ost im portant from 1983 to 1991. The Export Enhancem<br />
ent Program (EEP) became especially im portant in 1992 <strong>and</strong> 1993 when the United<br />
States competed against subsidized exports from the European Union. Over half o f<br />
the rice exports in 1985 <strong>and</strong> 1989 were dependent on government assistance. The<br />
PL480 programs also have been im portant, comprising from 5 to 25% o f annual total<br />
rice exports (Table 3.8.2). Other government assistance programs, such as Food for<br />
Progress <strong>and</strong> CCC African Relief, have been relatively m inor in contributing to rice<br />
exports.<br />
I
476 Production<br />
T A B LE 3.8.2.<br />
B a sts)<br />
Im p o rta n c e o f G o v e r n m e n t P r o g r a m s in A s s is t in g R ice E xp o rts (1 0 0 0 m t. M ille d<br />
Program<br />
Fistol<br />
Year<br />
PL480<br />
Credit<br />
Guarantee<br />
EEP<br />
Other<br />
Program s<br />
Total<br />
Exports<br />
Share<br />
{%)<br />
1983 429 328 0 0 2209 34<br />
1984 366 571 0 49 2212 45<br />
1985 500 359 0 180 1908 54<br />
1986 411 476 23 0 2237 41<br />
1987 370 636 28 60 2412 45<br />
1988 338 443 120 29 2125 44<br />
1989 355 826 20 0 2250 53<br />
1990 276 663 0 0 2501 38<br />
1991 210 183 76 4 . 2416 20<br />
1992 229 220 358 16 2279 36<br />
1993 199 235 278 137 2710 31<br />
1994 222 155 46 10 2434 18<br />
1995 196 32^ 113 14 3767 17<br />
1996 182 215 23 0 2831 15<br />
1997 116 89 0 0 2564 8<br />
1998 183 80 0 0 3100 8<br />
Source; USDA-ERS, <strong>Rice</strong> Situation <strong>and</strong> O utlook Yearbook¡ September 1998.<br />
V- ! *<br />
Government-assisted exports (except for PL480) have declined in importance<br />
since 1996. The 1996 Federal Agricultural Improvement <strong>and</strong> Reform ( FAIR) Act<br />
significantly changed the price <strong>and</strong> income support mechanisms for most grain crops,<br />
including rice. Supply control mechanisms <strong>and</strong> guaranteed target prices provided<br />
in previous farm programs were discontinued. Target prices were replaced with 7-<br />
year <strong>production</strong> flexibility contract payments for producers who had participated in<br />
previous commodity programs. These annual contract payments are scheduled to run<br />
only from 1996 through 2002, when the current 1996 farm bill will expire. Under<br />
the 1996-2002 contract payment system, rice producers have complete flexibility<br />
in planting decisions <strong>and</strong> may receive the contract payments whether or not they<br />
produce rice. The nonrecourse loan safety net is continued in the 1996 farm bill. The<br />
maximum rice loan rate is $6.50 per hundredweight.<br />
Along with most other grain producers, rice producers fared exceptionally well<br />
during the first few years of the 1996 FAIR Act, as they received guaranteed contract<br />
payments in addition to very favorable market prices. In 1998, the market price for rice<br />
began dropping dramatically, which caused a financial burden for rice producers. The<br />
producers received emergency supplemental contract payments in 1998, 1999, <strong>and</strong><br />
2000 to offset the adverse market conditions as a special appropriation to supplement<br />
the contract payments provided in the 1996 FAIR Act. W ith the loss o f deficiency payments<br />
<strong>and</strong> supply control over rice planting, the safety net for rice producers is now<br />
m uch lower than prior to 1996, causing pressure to change the current farm program.<br />
The recent General Agreement on Tariffs <strong>and</strong> Trade (GATT) accord <strong>and</strong> requirements<br />
o f the new World Trade Organization (W TO ) will add further uncertainty for U.S. rice<br />
producers, potentially opening new export markets but also allowing m ore foreign
Ríce Morketíng 477<br />
rice imports to penetrate the U.S, domestic market. Thus we luapbe at a new crossroad<br />
in 2002 to again shift the direction o f U.S. rice policy.<br />
To help offset the reduced safety net in the 1996 Farm Act, there has been increased<br />
government emphasis on the use o f subsidized crop insurance. A m<strong>and</strong>ated<br />
pilot revenue insurance program was started in 1996 for corn <strong>and</strong> soybeans. During<br />
1995-1998, the U.S. Department o f Agriculture s (USDA’s) Risk M anagement Agency<br />
(RM A), which administers Federal Crop Insurance (FCI) programs, spent about $1.2<br />
billion per year, on average, for insurance premium subsidies <strong>and</strong> other support costs.<br />
These agencies also oversee crop insurance <strong>and</strong> premium costs, ensuririg that private<br />
companies delivering crop insurance recover potential underwriting losses. As a further<br />
incentive to purchase crop insurance, the Secretary o f Agriculture authorized<br />
up to an additional $400 m illion in premium subsidies for 1999 buy-up coverage to<br />
further reduce the producer-paid premiums by about 30% .<br />
The choice o f insurance products has exp<strong>and</strong>ed since 1997 from individual-farm<br />
actual <strong>production</strong> <strong>history</strong>-m ultiple peril crop insurance (APH -M PCI) to area-yield<br />
<strong>and</strong> crop revenue insurance. Crop revenue insurance policies available to farmers provide<br />
protection from sharp drops in prices within each growing season, but provide<br />
little protection against price declines over different seasons. Thus the effectiveness o f<br />
crop insurance as a safety net to m aintain farm income is still being questioned. Use<br />
of crop insurance also has been restricted because many farmers expect that Congress<br />
will continue to provide disaster relief even if they don’t buy crop insurance.<br />
ROUGH RICE MARKETING SYSTEM<br />
Marketing Channels<br />
Once rice is harvested, there are two m ajor channels into which tire rougli rice flows:<br />
(1) on-farm drying <strong>and</strong> storage, <strong>and</strong> (2) commercial drying <strong>and</strong> storage (Sm ith et al.,<br />
1990). The com mercial drying <strong>and</strong> storage channel includes both independent <strong>and</strong><br />
cooperative facilities. M arketing channel flows for 1997-1998 in rough rice equivalents<br />
are shown in Figure 3.8.1. December 1, 1998 rough rice storage immediately<br />
following harvest was 35,6 m illion hundredweight on farms, compared with 86.0<br />
million hundredweight in com mercial warehouses. Total milled rice storage generally<br />
averages less than 0.2 million m etric tons for working stoclcs at mills <strong>and</strong> commercial<br />
warehouses. December 1,1998 farm stocks were distributed 52% in Arkansas, 13% in<br />
Louisiana, 7% in Texas, <strong>and</strong> 28% in other states (NASS, 1999). Arkansas accounted<br />
for 51% o f December 1998 storage in com mercial warehouses.<br />
The number o f Com m odity Credit Corporation (CCC)-approved warehouses<br />
<strong>and</strong> com mercial storage capacity for rice on July9,1 9 9 9 was Arkansas (32 warehouses,<br />
114 million hundredweight), California (30 warehouses, 92 m illion hundredweight),<br />
Louisiana (14 warehouses, 17 million hundredweight), Mississippi (4 warehouses, 7<br />
m illion hundredweight), <strong>and</strong> Texas (12 warehouses, 18 m illion hundredweight).<br />
Commercial storage warehouses for rice have increased in num ber <strong>and</strong> average<br />
size since the 1960s. Larger-capacity <strong>and</strong> more efficient commercial dryers also have<br />
been installed in recent years. Commercial dryers levy charges from $0.25 to $0.50 per<br />
bushel for rough rice, depending on the moisture content. <strong>Rice</strong> is harvested at 17 to<br />
J
478 Production<br />
^ jiiii<br />
22% moisture but must be dried to 13% p rior to storage. Commercial storage charges<br />
for rough rice are priced about $0.03 per bushel per m onth in Arkansas.<br />
On-farm rice drying <strong>and</strong> storage has been increasing in recent years. Benefits<br />
include increased convenience at harvest time by eliminating waiting time; reducing<br />
travel time to unload at commercial facilities, improved milling yield, <strong>and</strong> more<br />
control over marketing. <strong>Rice</strong> marketing cooperatives typically market from 70 to .<br />
90% of the rice produced in Arkansas <strong>and</strong> California. Louisiana, Texas, <strong>and</strong> Mississippi<br />
rice producers use primarily the direct sales or bidding process. The Louisiana<br />
Farm Bureau Marketing Association has a rice sales desk for marketing their members’<br />
rice.<br />
The marketing agencies can be either independent firms or cooperative marketing<br />
associations. The independent marketing agency firms do not generally h<strong>and</strong>le<br />
the commodity but simply oversee the marketing process. Rough rice samples are<br />
delivered to the trading center by either the producers or the com mercial storage<br />
facility, Samples are shelled <strong>and</strong> milled with a small huller/miller <strong>and</strong> graded by the<br />
selling agency. Interested mill buyers arrive on designated sales days <strong>and</strong> inspect the<br />
samples physically. A sealed-bid method is used to sell each lot offered by the seller.<br />
After receiving a bid, the seller usually has 24 hours to respond. W ith acceptance of<br />
a bid, ownership is transferred by the selling agency, with the buyer paying transport<br />
costs to move the rice from the storage facility. The marketing agencies generally<br />
charge a flat-rate fee per unit sold for the sales completed. These agencies provide<br />
an important price discovery mechanism for rice producers to com plement the rice<br />
futures market.<br />
Private rice mills in aU rice-producing states also buy rice directly from producers<br />
<strong>and</strong> use alternative pricing method^ The U.S. rice industry includes about 37 private<br />
rice mills <strong>and</strong> four cooperative rice mills listed as members o f the <strong>Rice</strong> M iller’s Association<br />
<strong>and</strong>/or USA <strong>Rice</strong> Council in 1999 (USA <strong>Rice</strong> Federation . . . , 2000). Cooperatives<br />
in the rice industry include two in Arkansas <strong>and</strong> two in California. All are highly<br />
vertically integrated. Cooperative functions include the provision o f machinery, fertilizers,<br />
<strong>and</strong> credit as well as drying, storage, milling, <strong>and</strong> transporting the crop into<br />
various distribution channels, including packaging for retail sale. Profits realized from<br />
rice cooperative drying <strong>and</strong> storage, milling, <strong>and</strong> marketing are returned to producers.<br />
Cooperatives generally contract for the delivery of rice from their members by about<br />
July each year for participation in the regular members’ seasonal pool. Participants<br />
receive an advance payment prior to harvest <strong>and</strong> are entitled to further settlements<br />
from the seasonal pool when the rice is marketed by the cooperative.<br />
Alternative pricing methods for producers to market their rough rice include<br />
pooling, bidding, direct contracting, <strong>and</strong> hedging. W ith tlie reduced guaranteed price<br />
safety net in the 1996 farm program, rice producers have become more market-<br />
oriented in seeking the best price for their rice. M ost rice cooperatives, such as the<br />
<strong>Rice</strong>l<strong>and</strong> Foods <strong>and</strong> Producers Cooperative in Arkansas, offer alternative pricing options<br />
for producers as well as the seasonal pool price. O ther pricing options can be<br />
based directly on the Chicago Board o f Trade futures price, adjusted for the local<br />
delivery point basis. <strong>Rice</strong> may also be priced later, after contracted delivery. Hedge-<br />
to-arrive contracts, basis contracts, <strong>and</strong> direct cash purchases are additional pricing<br />
options used by rice cooperatives. M ost rice contracts are based on a st<strong>and</strong>ard grade 2<br />
<strong>and</strong> 55/70 milling yield with premiums or discounts for variations in milling yield or<br />
quality. Cooperatives typically operated separate pools for long- <strong>and</strong> medium-grain
<strong>Rice</strong> Marketing 479<br />
rice. <strong>Rice</strong> may be delivered either green or dry with a cost assessment to dry green rice<br />
coming from the field. Farm-stored dry rice must be dried to a specific level, usually<br />
below 13.0% to be accepted without a drying charge. Each of the four rice cooperatives<br />
in the United States operates several mills <strong>and</strong> numerous drying <strong>and</strong> storage facilities,<br />
which exp<strong>and</strong>s their range o f operation. For example, <strong>Rice</strong>l<strong>and</strong> Poods operates several<br />
buying stations for rough rice in neighboring states as well as in Arkansas.<br />
U.S. rough rice grades run from U.S. No. 1 to U.S. No. 6 plus a sample grade<br />
for rough rice not meeting the quality requirements o f the other six grades (e.g., if<br />
the sample contains more than 14% moisture or if the sample is in generally poor<br />
condition) (USDA, 1983). The six numbered rice grades are distinguished by tlie<br />
amount o f extraneous or damaged seeds, red rice, <strong>and</strong> chaUcy kernels. For example,<br />
U.S. No. 2 cannot contain more than seven undesirable seeds per 500 g or more than<br />
1.5% red rice. Rough rice intended for parboiling is graded on color with the highest<br />
quality grade requiring that kernels should have a white or creamy color.<br />
<strong>Rice</strong> breeders in the United States work primarily in publicly supported state-<br />
federal breeding programs in collaboration with state seed foundation programs <strong>and</strong><br />
the rice industry to produce cultivars with desirable agronomic <strong>and</strong> end-use properties.<br />
All new cultivars are screened for cooking <strong>and</strong> processing qualities by the USDA<br />
National <strong>Rice</strong> Quality Laboratory at Beaumont, Texas. M ajor quality distinctions<br />
between medium- <strong>and</strong> long-grain rice are that the long-grain types have higher amy-<br />
lose <strong>and</strong> lower alkali-spreading values, resulting in dryer, fluffier, <strong>and</strong> less sticky rice.<br />
M edium- <strong>and</strong> short-grain cultivars have lower amylose <strong>and</strong> higher alkai-spreading<br />
values, resulting in moist, sticky rice.<br />
The U.S. rice industry has developed a worldwide reputation for quality by using<br />
effective breeding programs, improved cultural practices, <strong>and</strong> modern, sophisticated<br />
rice drying, storage, <strong>and</strong> milling facilities. The premium paid for U.S. rice over other<br />
similar types offered in the world market is due largely to this quality reputation.<br />
<strong>Rice</strong> quality control occurs at all stages o f processing <strong>and</strong> marketing. Incom ing<br />
dried rough rice samples are sent to mill quality control labs to measure the milling<br />
yield <strong>and</strong> grade. Exported rice is graded by the Federal Grain Inspection Service<br />
(FG IS). Federal inspection by the FGIS is available, but not m<strong>and</strong>atory, at other stages<br />
prior to export.<br />
The Commodity Credit Corporation (CCC) is another market channel provided<br />
by the government for producers’ rough rice if the market price is less than the<br />
prevailing loan rate. Under the nonrecourse loan program, producers may forfeit the<br />
rice delivered to designated CCC warehouses as collateral for the loan (USDA, 1994).<br />
Since the marketing loan mechanism was introduced, producers can sell rice at a price<br />
below the loan rate <strong>and</strong> receive a loan deficiency payment (LDP) without delivery to<br />
the CCC market channels.<br />
Rough rice also may be traded <strong>and</strong> delivered by producers in fulfillment o f futures<br />
contracts on the Chicago Board o f Trade as a further market channel. This channel<br />
develops from farmers hedging their crop to take advantage o f futures price relationships.<br />
Also some producers delay selling after rice harvest to take advantage o f possible<br />
storage returns. Past cash price relationships show that producers should track the<br />
postharvest prices because cash price increases may be enough to pay for storage.<br />
Producers in three o f the marketing years from 1992 to 1998 could have increased<br />
returns by storing at harvest <strong>and</strong> pricing their rice after December o f the marketing<br />
year (Table 3.8.3).
480 Production<br />
TABLE 3.8.3.<br />
Average Rough <strong>Rice</strong> Prices Received by U.S. Formers ($/cwt)<br />
M onth 1 9 9 2 -1 9 9 3 1 9 9 3 -1 9 9 4 1 9 9 4 -1 9 9 5 1 9 9 5 -1 9 9 6 1 9 9 6 -1 9 9 7 1 9 9 7 -1 9 9 8 1 9 9 8 -1 9 9 9 1 9 9 9 -2 0 0 0<br />
p i<br />
l|;;<br />
m<br />
August 6.60 5.14 6.87 7.77 10.10 9.94 9,01 7.62<br />
September 6.41 5.16 6.82 8.01 10.00 9.92 9.42 6.88<br />
October 6.40 6.01 6.52 8,84 9.66 10.00 9.31 6.23<br />
November 6.40 7.94 6.63 9,21 9.41 9.82 9.02 6.11<br />
December 6.38 8.78 6.60 9.45 9,82 9.77 9.10 6.19<br />
January 6.35 8.92 6.83 9.36 9.95 9.57 9.09 6.03<br />
February 6.06 9.99 6,74 9.19 10.10 9.75 9.02 5.98<br />
March 5.63 10.10 6.67 9.20 10.20 9.67 8.93 5.82<br />
April 5,50 9.80 6.75 9.35 10.30 9,40 8.49 5.86<br />
May 5.23 9.90 6.87 9.73 10.20 9.38 8.21 5.56<br />
June 5.02 8.76 7.06 9.77 9.90 9.58 8.25 5.59<br />
July 4.90 7.69 7.19 9.81 10.00 9.58 8.26 5.47<br />
Source: USDA-ERS, <strong>Rice</strong> Situation <strong>and</strong> Outlook Yearbook, RCS-2000.<br />
<strong>Rice</strong> Futures <strong>and</strong> Options Markets<br />
Since rice futures trading started in 1986, the unit of trading for rough rice contracts<br />
is 2000 cwt, witli a deliverable grade of U.S, No. 2 or better long-grain rough rice. The<br />
milling yield must be at least 65% , including a head rice yield o f at least 48% . Months<br />
traded on the Chicago Board o f Trade are January, March, May, July, September, <strong>and</strong><br />
November, Delivery points for physical delivery include several designated counties<br />
in eastern Arkansas. The delivery instruments for rice contracts are registered warehouse<br />
receipts issued by exchange-approved warehouses, mcluding several in eastern<br />
Arkansas. Other rice states do not have approved delivery points.<br />
The futures market is an important hedging tool for farmers that has become<br />
more popular since the loss o f government price protection in the 1996 Farm Program,<br />
However, the volume traded on the rice futures market has been persistently<br />
much lower, as a percent o f current year <strong>production</strong>, than the volume traded on the<br />
futures market for other commodities, such as soybeans. Daily open interest in early<br />
1998 averaged between 4000 <strong>and</strong> 5000 contracts, with about 1000 contracts traded per<br />
day, which is marginal for a successful futures contract. The reduced trading volume<br />
makes the rice futures market potentially less useful as a pricing mechanism because of<br />
increased volatility in price. In contrast to other grains in the United States, a large volume<br />
o f U.S. rice <strong>production</strong> is marketed through cooperative pools <strong>and</strong> is not hedged<br />
in the futures market. <strong>Rice</strong> cooperatives have recently begun to utilize the futures<br />
market to a greater extent to help improve participation in the rice futures market.<br />
In response to the concern about low volume in the rice futures market, a study o f the<br />
long-grain rough rice futures market was conducted in Arkansas from 1986 to 1998.<br />
Results indicated that tlie market is efficient <strong>and</strong> that rice market participants can use<br />
this market as a price-risk management tool (Cram er et al., 1999).<br />
<strong>Rice</strong> producers can trade in put or call options, since 1994, on the Chicago Board<br />
o f Trade. A put option enables producers to establish a floor or m inim um selling<br />
price with a one-tim e premium cost purchase, m uch like buying an insurance policy.<br />
For the premium, the put option buyer has the right to sell a futures contract at<br />
a predetermined price, known as the strike price. Unlike trading in futures, option
<strong>Rice</strong> Marketing 481<br />
buyers are not subject to margin calls to maintain their position in the market. Thus<br />
there is considerably less risk in evaluating the cash requirements to trade in options<br />
versus trading in futures. A further advantage o f options is that a producer can lock<br />
in a m inim um price with a put option <strong>and</strong> not be limited in gaining a better price if<br />
the market price continues to increase.<br />
A call option provides the buyer with the right to buy a futures contract at a<br />
predetermined price with payment o f a one-tim e premium. Options gain market<br />
value after purchase if the position taken is profitable. The option purchaser can resell<br />
the option in lieu o f exchanging it for a futures contract with a minim al transaction<br />
cost if the option has subsequent market value.<br />
The only negative factor in buying options as a hedging tool is the premium<br />
cost. Premiums are not involved in purchasing futures contracts, only commissions.<br />
Premium costs for buying rice options will vary with different strike prices offered.<br />
The cost range typically is about $0.20 to 0.40 per hundredweight for strike prices<br />
that are comparable to the corresponding futures market price. In addition to the<br />
commission charge to purchase or sell futures contracts <strong>and</strong> options, futures contracts<br />
involve the expense <strong>and</strong> uncertainty o f putting up margin call m oney from tim e to<br />
time that is deposited with a broker if the market price moves against your position.<br />
These margin requirements can be troublesome for both producers <strong>and</strong> their bankers.<br />
<strong>Rice</strong> Price Relationships<br />
Average U.S. farm prices for long-grain rice in milled rice value equivalent have ranged<br />
from a low o f $48 per m etric ton in 1986 marketing year to a high o f $133 per m etric<br />
ton in 1996-1997 (Table 3.8.4). The margin per m etric ton between the Houston FO B<br />
long-grain mill price <strong>and</strong> tlie U.S. farm price expressed in milled equivalent value has<br />
ranged from $207 in 1986-1987 to $356 in 1993-1994, indicating that the margin<br />
tended to increase with higher market prices. The margin exceeded $300 per m etric<br />
ton when the FOB mill price was above $400 per m etric ton (Table 3.8.4).<br />
Since 1986-1987, the Houston FOB mill price generally has been above the R otterdam<br />
price for U.S. milled rice (Table 3.8.4). The reduced price in Rotterdam com <br />
pared with FO B Houston may be explained by the shift over time in U.S. rice export<br />
markets. For example, Saudi Arabia, Japan, <strong>and</strong> Turkey were the top rice export markets<br />
in 1992-1993 through 1994-1995, but Mexico has been tlie top market from<br />
1995-1996 through 1997-1998. The U.S. domestic market also has become the m ost<br />
im portant overall market for U.S. rice.<br />
U.S. rice generally has sold at a premium over Thai rice; however, tliis premium<br />
basis on the Rotterdam market has fallen sharply since the 1983-1984 through 1 9 8 5 -<br />
1986 period (Table 3.8.4), U.S. exports to Europe, Africa, <strong>and</strong> tlie Middle East have<br />
declined over the past decade, while Western Europe imports dropped from 22% in<br />
1988-1989 to only 11% in 1997-1998.<br />
PROCESSED RICE MARKETING SYSTEM<br />
Marbling Channels<br />
The three m ajor domestic outlets for rice produced in the United States are direct<br />
food use, processed food use, <strong>and</strong> beer (Table 3.8.5). Nearly 59% o f domestic use o f
«fîT<br />
482 Production<br />
TABLE 3.8,4.<br />
L o n g - G r a in R ico P rise s<br />
U.S, R ice<br />
T h a ila n d <strong>Rice</strong><br />
Farm FOB M ill" R o tte rda m '' Rotterdam"<br />
M o rk e tin g<br />
Y ear"<br />
R ough<br />
($/ewt)<br />
M ille d<br />
(S/mi)<br />
P rice<br />
(S/mt)<br />
M a rg in<br />
(S/mf)<br />
P rice<br />
(S/mt)<br />
M a rg in<br />
(S/mt)<br />
P rice<br />
(S/mt)<br />
M a rg in<br />
(S/mt)<br />
:|î;<br />
1983-1984 9.36 118 438 320 .527 89 329 198<br />
1984-1985 8.66 109 414 305 495 81 268 227<br />
1985-1986 6.75 85 370 285 417 47 236 181<br />
1986-1987 3.82 48 255 207 261 6 232 29<br />
1987-1988 7.77 98 439 341 369 (70) 317 52<br />
1988-1989 6.96 88 342 254 313 (29) 339 26<br />
1989-1990 7.59 95 355 260 338 (17) 336 (2)<br />
1990-1991 6.94 87 342 255 340 (2) 338 2<br />
1991-1992 7.83 98 377 279 359 (18) 328 31<br />
1992-1993 5,87 74 336 262 287 (49) 290 (3)<br />
1993-1994 7.93 100 456 356 413 (43) 335 78<br />
1994-1995 . 6.87 86, 323 237 325 2 331 (6)<br />
1995-1996 9.37 118 421 303 404 (17) 407 (3)<br />
1996-1997 10.60 133 461 328 428 (33) 380 48<br />
1997-1998 10.10 127 431 304 417 (14) 345 72<br />
Source: D ata from NASS (1 9 9 9 ),<br />
"August 1 to July 31.<br />
'’R ough rice price per hundredw eight is converted to a price p er m etric ton o f m illed rice equivalent. This is<br />
calculated w ith an assum ed 55/70 m illing yield requiring 1.75 m t rough rice p er m etric to n o f m illed rice.<br />
'P O B m ill in H ou ston , Texas.<br />
''FAS, container for U .S. No. 2 ,4 % at R otterdam port. M argin betw een H ou ston FO B <strong>and</strong> Rotterdam price.<br />
'FAS bulk after M ay 15, 1985 fo r T h ai 100% grade B (in bags p rio r to M ay 15, 1985) at Rotterdam port.<br />
M argin between U S . <strong>and</strong> T h ai price at R otterdam o f to tal d om estic use. Per capita food use o f all rice<br />
products increased by 9 % fro m 1 9 9 4 -1 9 9 5 to 1 9 9 7 -1 9 9 8 ( F oo d Research Associates, 1999).<br />
U.S. rice was for direct food use in 1998-1999, an increase from 54% in 1994-1995.<br />
Processed use <strong>and</strong> beer use declined in terms o f the share o f total domestic use. Per<br />
capita food use o f all rice products increased by 9% from 1994-1995 to 1997-1998<br />
(Food Research Associates, 1999).<br />
O f the 37.6 million hundredweight o f domestic U.S. rice used for direct food use<br />
in 1997-1998 (Table 3.8.5) shipments to grocery stores comprised 56.8% ; warehouse<br />
clubs 4.9% ; food service, such as restaurant chains, 37.5% ; <strong>and</strong> other outlets, such<br />
as domestic USDA feeding programs, about 1%, Domestic shipments o f specialty<br />
rices include parboiled, precooked, brown, <strong>and</strong> aromatic rice. Milled rice used for<br />
processed foods declined from 16.1 million hundredweight in 1994-1995 to 15.6<br />
million metric ton in 1997-1998. Changes in tlie types o f processed foods from rice<br />
from 1994-1995 to 1997-1998 were cereal ( —4% ), pet food (+ 2 5 % ), package mixes<br />
(—60% ), rice cakes (—18% ), baby food (+ 2 9 2 % ), <strong>and</strong> frozen dinners (+ 1 1 9 % ). The<br />
composition o f processed foods in 1997-1998 was cereal (36% ), pet food (36% ),<br />
package mixes (8% ), baby food (7% ), frozen dinners (4% ), <strong>and</strong> otlier items, such<br />
as snacks, soup, <strong>and</strong> desserts (9% ). M edium-grain rice is used mainly in beer <strong>and</strong><br />
breakfast cereal. Broken rice is used in pet food, cereal, <strong>and</strong> beer. Long-grain rice is
Ríce Marketing 483<br />
T A B L E 3.8.5. D o m e s tic O u tle ts fo r U.S. R ice ( M illio n H u n d re d w e ig h t , M ille d B a s is )<br />
Outlet 1 9 9 4 -1 99S 1 9 9 5 -1 9 9 6 1 9 9 6 -1 9 9 7 1 9 9 7 -1 9 9 8 1 9 9 8 -1 9 9 9<br />
Direct food use 31.5 36.3 35.8 37.6 38.1<br />
Processed food use 16.1 14.9 14.1 15.6 16.2<br />
Beer 10.7 11.2 10.8 11.1 10.7<br />
U.S, rice domestic use 58.3 62,4 60.7 64.2 65.0<br />
<strong>Rice</strong> imports" 5.1 ' 5,3 7.0 6.6 7.1<br />
Total rice domestic use 63,4 67.7 67.7 70.8 72.1<br />
Population 262.3 264.4 266.8 269.3 271.7<br />
Per capita rice use (lb) 24.2 25.6 25.4 26.3 26.1<br />
Source: Food Research Associates (1999).<br />
“Mosdy for direct food use.<br />
used in beer <strong>and</strong> cereals. Specialty rices are used in packaged mixes <strong>and</strong> frozen dinners.<br />
<strong>Rice</strong> flour is used in baby food, cereals, crackers, snacks, <strong>and</strong> crispies. Short-grain<br />
rice is used in pet food <strong>and</strong> cereals. Milled rice use in processed food in 1997-1998<br />
was medium-grain rice (9.9 million hundredweight), rice flour (1.4 million hundredweight),<br />
<strong>and</strong> others not specified (1.0 million hundredweight) (Food Research<br />
Associates, 1999).<br />
There are three m ajor market channels for white <strong>and</strong> specialty rices produced in<br />
the United States (Table 3.8.6). These channels vary for different <strong>production</strong> regions.<br />
M ost shipments from Arkansas <strong>and</strong> M issouri <strong>and</strong> California go to domestic outlets.<br />
Shipments from Louisiana <strong>and</strong> Florida <strong>and</strong> Texas <strong>and</strong> Mississippi went mainly to export<br />
markets (Food Research Associates, 1999). Exports in 1997-1998 comprised 18.3<br />
million hundredweight o f white rice <strong>and</strong> 13.3 million hundredweight o f specialty rices<br />
(Table 3.8.6). About 90% o f the 1997-1998 milled rice shipments to export markets<br />
were long-grain rice. Long-grain rice comprised 69% o f domestic rice shipments for<br />
retail, wholesale, <strong>and</strong> food service outlets. However, 84% o f all shipments to U S .<br />
territories were medium-grain rice. U.S, rough rice exports have increased rapidly<br />
since 1990-1991, fro m 4% prior to 1991 to 30% in the 1997-1998 period. This growth<br />
T A B L E 3.8.6.<br />
R ice D istrib u t io n to D o m e stic , U S . Territo rie s, a n d E xport M a r k e t s fro m D iffe re n t<br />
U S . P ro d u c tio n R e g io n s , 1 9 9 7 - 1 9 9 8 [ M illio n H u n d re d w e ig h t , M ille d B a s is )<br />
D estination<br />
Dom estic U S . Territories Export<br />
Source of Production W h ile Speciolty W hite Speciolty W hite Speciolty<br />
Arkansas <strong>and</strong> Missouri 18.8 2.9 2.4
484 Produtfion<br />
is due to increased Latin American dem<strong>and</strong> to better utilize their mill capacity, lower<br />
tariffs for U.S. rough rice imports, <strong>and</strong> also the effects o f El Niño.<br />
Ríce By-Product Marketing<br />
Millmg by-products include rice huUs, rice bran, broken rice, <strong>and</strong> rice bran oil. Broken<br />
rice is used for some food preparations <strong>and</strong> in the brewing industry, fn the 1997-<br />
1998 marketing year, rice millers produced a total o f 12.4 million hundredweight of<br />
rice bran, 20.6 m illion hundredweight o f rice hulls, 0.5 million hundredweight of rice<br />
bran oil, <strong>and</strong> 2.7 million hundredweight o f other rice products (Table 3.8.7). Part of<br />
the rice bran was extracted to produce rice bran oil. M ost o f the bran <strong>and</strong> hulls are<br />
used for livestock feed. Some hulls are used for fuel. The rice bran oil can be refined<br />
for edible use as cooking or salad oil, cosmetics, animal nutrition, <strong>and</strong> the <strong>production</strong><br />
o f some nutraceuticals (e.g., for cholestei'ol control) (Young et al., 1994).<br />
<strong>Rice</strong> Marketing Margins<br />
<strong>Rice</strong> milling costs were estimated in 1998 to range from a low o f $1.29 per hundredweight<br />
for rough rice in California to a high o f $ 1.81 per, hundredweight in Louisiana<br />
(Wailes <strong>and</strong> Gauthier, 1998). The estimated 1998 U.S. average milling cost was $1,52<br />
per hundredweight o f rough rice or $2.58 per hundredweight o f milled rice. California<br />
<strong>and</strong> Arkansas had lower milling costs because o f the larger mill capacity in these states.<br />
<strong>Rice</strong> mill marketing margins per hundredweight o f rough rice were estimated to average<br />
$6.02 fo’* Arkansas mills <strong>and</strong> $5.92 for Houston mills for the period 1970-1992<br />
(Wailes <strong>and</strong> Gauthier, 1998). This is equivalent to about $241 per m etric ton o f milled<br />
rice (see Table 3.8.4). California milling margins averaged $7.61 per hundredweight<br />
o f rough rice. This higher margin in California is explained by the use o f unionized<br />
labor. The real marketing price margin for rice was estimated to decline from 1970 to<br />
1991 in a study o f average U.S. rice mills by Chavez (1994). These findings by Chavez<br />
indicated that pricing efficiency was increasing over time in the U.S. rice market.<br />
Although the U.S. rice industry is a heavily concentrated industry compared with<br />
other grains, such as soybeans <strong>and</strong> corn, the largest rice milling companies have had<br />
a declining share o f shipments since 1986-1987 (Childs, 1992h The declining share<br />
T A B LE 3 . 8 7 . R ice B y -p ro d u c t S h ip m e n ts fro m M ills , 1 9 9 7 - 1 9 9 8 (M illio n H u n d re d w e ig h t )<br />
O rigin <strong>Rice</strong> Bran <strong>Rice</strong> Hulls <strong>Rice</strong> Bran Oil Other Total<br />
Arltansas <strong>and</strong> Missouri 5.4 7.0 0.5" 1.5 13.9<br />
Louisiana <strong>and</strong> Florida 0,7 1.3 0.0 0.9 2.9<br />
Texas <strong>and</strong> Mississippi 3,7 6.2 0.0 0.3 10.1<br />
South total 9.8 14.5 0.0 2.7 26.9<br />
California 2.6 6.2 0.0 0.0 8.8<br />
U.S. total 12.4 20.6 0.0 2.7 35.7<br />
Source: Food Research Associates (1999).<br />
"Estimate of rice bran oil obtained from rice mill operators.
<strong>Rice</strong> Marketing 485<br />
since 1986-1987 is attributed to a drop in exports from the largest mills <strong>and</strong> to in <br />
creased domestic shipments from medium-sized mills that have established their own<br />
rice markets. The number o f U.S. rice mills decreased from 66 in 1985 to 41 in 1999.<br />
Competitiveness of U.S. <strong>Rice</strong><br />
The western hemisphere is the m ajor U.S. rice market, accounting for over 60% of<br />
the 2.8 million m etric tons o f rice exported in 1999-2000. M ajor U.S. importers in<br />
1997-1998 were (in million m etric tons): Mexico 0.37, European Union 0.3, Japan<br />
0.28, Turkey 0.21, Haiti 0.2, Canada 0.18, Salidi Arabia 0.15, Ghana 0,08, South Africa<br />
0.07, <strong>and</strong> the Philippines 0.07.<br />
Canada <strong>and</strong> M exico are members o f the North American Free Trade Agreement<br />
(NAFTA), providing a preferential im port duty for U.S. rice. U.S. exports to Central<br />
America have increased nearly fivefold since 1988-1989 because o f NAFTA with<br />
M exico <strong>and</strong> because Mexico, Costa Rica, Guatemala, Honduras, El Salvador, <strong>and</strong><br />
Nicaragua agreed to ban all Asian rice imports for phyosanitary reasons. M ost U.S. exports<br />
to Latin America have been rough rice, which have lower tariffs than milled rice.<br />
M ajor competitors in U.S. export markets include China <strong>and</strong> other Asian exporters,<br />
plus a few small exporters in Latin America. China is a m ajor com petitor<br />
with the United States to supply the newly opened Japan im port market, <strong>and</strong> China<br />
is currently the only exporter to the South Korean market for high-quality japónica<br />
rice. Guyana has Caricom (Caribbean Community) m em ber preference to supply<br />
the Caribbean market <strong>and</strong> also preference to supply the European Union (EU) m arket.<br />
Guyana also has taken steps to join the M ercosur (M ercosur Customs Union,<br />
whose member nations are Argentina, Brazil, Paraguay, <strong>and</strong> Uruguay). Argentina <strong>and</strong><br />
Uruguay are currently the main com petitors with the United States to supply the<br />
rice im port market in Brazil. Thail<strong>and</strong> <strong>and</strong> India have displaced the United States<br />
in the Soutli Africa parboiled market. Asian exports also have displaced other U.S.<br />
rice exports in the Africa market.<br />
The top rice exporters in 2000 were estimated to be (in million m etric tons):<br />
Thail<strong>and</strong> 6.0, Vietnam 3.4, China 3.2, United States 2.75, Paldstan 1.85, India 1.3,<br />
Uruguay 0,65, Australia 0.55, Argentina 0.5, <strong>and</strong> Egypt 0,42 (USDA <strong>Rice</strong> Situation<br />
<strong>and</strong> Outloolc Report, 2001).<br />
U.S. rice exports to most other regions have declined since 1998-1999 due to increased<br />
com petition from Thail<strong>and</strong> for high-quality markets, Vietnam for the lower-<br />
<strong>and</strong> medium-quality markets in Asia <strong>and</strong> Africa, <strong>and</strong> more recently, India for the<br />
parboiled markets in the Middle East <strong>and</strong> South Africa. Japan is the only other market<br />
in which U.S. exports have increased since 1995-1996, when this market was opened<br />
under the GATT-W TO.<br />
The United States is strongly competitive in some high-quality rice export m arkets<br />
but has difficulty competing on price in lower-quality markets with Asian exporters<br />
such as Thail<strong>and</strong> <strong>and</strong> Vietnam. Thail<strong>and</strong> is the dominant world rice exporter<br />
<strong>and</strong> is the primary price setter in the world market. Vietnam is a strong export<br />
competitor since it produces up to three rice crops per year <strong>and</strong> has very low labor<br />
costs associated with <strong>production</strong> o f rough rice. However, as noted earlier, U.S. rice<br />
generally sells at a substantial price premium over Asian rice because o f the higher<br />
quality, strong export prom otion, <strong>and</strong> reliability o f supply. The U.S. rice exported to
486 Production<br />
Central <strong>and</strong> South America only has to compete with other regional exporters, such as<br />
Guyana, Argentina, <strong>and</strong> Uruguay. The United States does not currently compete with<br />
Asian rice in South America, due to phytosanitary im port restrictions on Asian rice.<br />
The 1996 FAIR Act helps to support the international competitiveness o f U.S.<br />
rice exports, as in form er farm bills. Continued export assistance programs for rice in<br />
1996 include the Export Credit Guarantee Programs (GSM ), the Export Enhancement<br />
Programs (EEP), tlie M arket Access Programs (M AP), <strong>and</strong> PL480 programs. Under<br />
PL480 <strong>and</strong> other food grain programs, the United States sells rice on concessional<br />
credit terms <strong>and</strong> donates rice to needy countries either bilaterally or through the<br />
World Food Program. The Export Credit Guarantee Program (G SM -102) <strong>and</strong> Intermediate<br />
Export Credit Guarantee Program (G SM -103) help importers with foreign<br />
currency constraints to buy rice. Commercial sales with G SM -102 assistance have<br />
guaranteed loans o f 3 years or less, <strong>and</strong> G SM -103 guarantees loans o f 3 to 7 years.<br />
Export Enhancement Programs facilitate U.S. rice markets overseas where the United<br />
States must compete with subsidized exports, primarily from the EU. Total program<br />
exports were relatively small in 1998, including 80000 m t in credit guarantees <strong>and</strong><br />
183 000 m t in PL480 shipjnents. They comprised only about 8% o f total U.S. rice<br />
exports, compared to 55% in 1985. Export Enhancement Program rice sales wUl be<br />
capped at 39 000 m t in 2001 to comply with the G A TT-W TO agreement.<br />
INTERNATIONAL RICE MARKET<br />
Competitiveness in the rice export market is affected by various factors, including<br />
shifts in foreign exchange rates. The Thai 100% , grade B, FOB Bangkok price has<br />
fallen from $335 per m etric ton in July 1997 to $190 by December 2000, due to<br />
oversupply globally <strong>and</strong> devaluation o f the Thai baht. Other im portant factors that<br />
affect competitiveness include comparative supply costs o f different exporters, rice<br />
quality differences, freight cost differences, <strong>and</strong> degree o f export promotion.<br />
Characteristics of the World <strong>Rice</strong> Market<br />
World rice trade accounts for less than 6% o f world <strong>production</strong>. Trade volume is<br />
determined by changes in the price relationships o f different types o f rice, <strong>production</strong><br />
shortfalls, self-sufficiency policies o f im portant rice-consum ing countries, <strong>and</strong> trade<br />
policy liberalization such as in the current W TO. The thin trade volume is further<br />
differentiated by type o f rice, such as aromatic, long or short grain, <strong>and</strong> so on, <strong>and</strong><br />
by rice quality. Quality in international rice trade is based largely on the content o f<br />
broken kernels. High-quality rice has 5% or less brokens, whereas low-quality rice<br />
may have up to 35% brokens.<br />
The United States recently has increased exports in Latin America because o f<br />
phytosanitary regulations to ban Asian rice im ports, NAFTA, <strong>and</strong> the capability to<br />
export rough rice, preferential duties, <strong>and</strong> freight cost advantages over more distant<br />
rice exporters such as tire EU <strong>and</strong> Asian exporters.<br />
Countries that compete with the United States in South <strong>and</strong> Central America<br />
are (in miUion m etric tons in 2000): Argentina 0.5, Uruguay 0.65, <strong>and</strong> Guyana 0.3.
<strong>Rice</strong> Marketing 487<br />
Argentina <strong>and</strong> Uruguay currently export mostly to Brazil. Because o f special arrangem<br />
ents under the M ERCO SU R trade agreement, Argentina <strong>and</strong> Uruguay dominate<br />
the Brazilian im port market, about 0.7 million m etric tons in 2000. The M ERCO SU R<br />
operates similarly to NAFTA, the trade agreement among the United States, Canada,<br />
<strong>and</strong> Mexico. Trade agreement members provide a reduced tariff rate for imports from<br />
other members.<br />
M ajor world rice importers are Brazil, Bangladesh, the EU, Japan, Indonesia, the<br />
Philippines, Iran, Iraq, <strong>and</strong> Saudi Arabia. World rice prices are highly volatile, due<br />
to the low volume traded <strong>and</strong> the inelasticity o f supply <strong>and</strong> dem<strong>and</strong> with respect to<br />
price. Price shocks often result from <strong>production</strong> short falls. Much o f the Asian rice<br />
<strong>production</strong>, which accounts for 90% of the world output, is produced under rainfed<br />
conditions that are subject to m onsoon cycles.<br />
World rice <strong>production</strong> in 2010 is projected to increase by nearly 11% over 2000<br />
to a record level o f 444 m illion m etric tons (Wailes et al., 2000). Total rice utilization<br />
in 2010 is projected to increase to 443 m illion m etric tons, about 11% over 2000<br />
(Wailes et al., 2000). As many of the higher-incom e developing countries have negative<br />
income elasticities for rice, the AGRM projects a lower per capita consumption in<br />
2000 for China, Egypt, India, Indonesia, Japan, South Korea, Pakistan, Taiwan, <strong>and</strong><br />
Vietnam. Average U.S. rice export prices are projected to increase nom inally from<br />
$270 in 2000 to $390 per m etric ton by 2010.<br />
U.S. <strong>Rice</strong> Sector Projections<br />
The AGRM projected that the U.S. rice area would increase 1.25 million hectares in<br />
2000 to 1.36 m illion hectares in 2010. Milled rice <strong>production</strong> is projected to increase<br />
from 6.1 million m etric tons in 2000 to 7.2 million m etric tons in 2010. Consumption<br />
is projected to increase from 3.9 m illion m etric tons in 2000 to 4.9 million m etric tons<br />
in 2010. <strong>Rice</strong> exports are projected to increase slightly from 2.7 million m etric tons<br />
to 2.8 million m etric tons. U.S. rice stoclcs are projected to remain at the 2000 level at<br />
0.7 million m etric tons (Wailes et al., 2000).<br />
SUMMARY AND CONCLUSIONS<br />
The U.S. rice economy includes the states o f Arkansas, California, Louisiana, Texas,<br />
Mississippi, <strong>and</strong> Missouri. Arkansas <strong>and</strong> California account for 45 <strong>and</strong> 24% o f rice<br />
<strong>production</strong>, respectively; CalifiDrnia specializes in medium-grain rice, while the southern<br />
states produce mostly long-grain rice. Over half o f the U.S. rice is sold in the<br />
domestic market. Im ports comprise about 10% of U.S. domestic use.<br />
Government programs figured prominently in rice <strong>production</strong> up until 1996<br />
with a m ajor part o f crop income derived from direct government payments. The<br />
government also supported exports with credit assistance, export subsides, <strong>and</strong> PL480<br />
concessional sales. Under the 1996 farm bill, the government price support was designed<br />
to decline, although producers still benefit from export assistance programs.<br />
Requirements to control rice also have ceased since the 1996 farm biU. The current<br />
farm program emphasis is on producing for the market with a reduced safety net,<br />
limited only to loan prices <strong>and</strong> annual contract payments. Increased use o f crop
Production<br />
insurance has been encouraged with additional subsidies to help defray the insurance<br />
cost for producers. The present 1996 farm bill will expire in 2002.<br />
Rough rice is dried <strong>and</strong> stored after harvest in either on-farm or commercial<br />
facilities. The marketing system for rough rice includes sale to cooperative pools for 70<br />
to 90% o f the rice in Arkansas <strong>and</strong> California. Rough rice in other states is marketed<br />
primarily through tlie direct sales or bidding process. Private mills also buy directly<br />
from producers. The U.S. rice industry includes 37 private <strong>and</strong> four cooperative mills.<br />
Producers can deliver rough rice to CCC warehouses if the market price is less than<br />
the loan rate. Long-grain rice can be hedged on the futures market <strong>and</strong> delivered in<br />
fulfillment o f futures contracts.<br />
M ajor domestic outlets for milled rice are for direct food use, processed food<br />
use, <strong>and</strong> the brewing industry. <strong>Rice</strong> for direct food use is distributed to groceries,<br />
warehouse clubs, food service, <strong>and</strong> USDA feeding programs. Processed food outlets<br />
include cereals, pet food, package mixes, rice cakes, baby food, <strong>and</strong> frozen dinners.<br />
Medium-grain rice, mostly brokens, is used for brewing. Milled rice shipments from<br />
mills go to domestic outlets, U.S. territories, <strong>and</strong> for export.<br />
REFERENCES<br />
Chavez, E. C. 1994. An analysis o f pricing efficiency <strong>and</strong> competitiveness in the U.S.<br />
rice market. M,S. thesis, University o f Arkansas, Fayetteville, AR.<br />
Cramer, G. L., E. J. Wailes, B. Jiang, <strong>and</strong> L. Hoffman. 1999. Market efficiency tests o f<br />
U.S. rough rice futures market. In R. J. Norman <strong>and</strong> T. H, Johnston (eds.), <strong>Rice</strong> Research<br />
Studies, 1998. Arkansas Agricultural Experiment Station, Fayetteville, AR.<br />
Food Research Associates. 1999. U.S. <strong>Rice</strong> Distribution Patterns 1997-98 Report. USA<br />
<strong>Rice</strong> Federation, 321 East Hillside Avenue, Barrington, Illinois.<br />
NASS. 1999. Agricultural Statistics. National Agricultural Statistics Service, Washington,<br />
DC.<br />
<strong>Smith</strong>, R. K., E. J. Wailes, <strong>and</strong> G. L. Cramer. 1990. The Market Structure of the U.S.<br />
<strong>Rice</strong> Industry, Univ, Ark. Agric. Exp. Stn. Bull. 921.<br />
USA <strong>Rice</strong> Federation-USA <strong>Rice</strong> Mill Members o f <strong>Rice</strong> M iller’s Association-USA <strong>Rice</strong><br />
Council. 2000, 4301 Nortli Fairfax Drive, Arlington, Virginia.<br />
USDA. 1983. United States St<strong>and</strong>ards for Grains. Federal Grain Inspection Service, U.S.<br />
Department of Agriculture, Washington, DC.<br />
USDA. 1994. The U.S. <strong>Rice</strong> Industry, Agric. Econ. Rep. 700. U S . Department o f Agriculture,<br />
Washington, DC.<br />
USDA. 2001. <strong>Rice</strong> Situation <strong>and</strong> Outlook Report, R CS-0301, September. U.S. Department<br />
o f Agriculture, Washington, DC.<br />
Wailes, E. J., <strong>and</strong> W. M. Gautliier. 1998. U.S. <strong>Rice</strong> Milling Industry: Structure <strong>and</strong><br />
Ownership Changes. In D. W. Larson, P, W. Gallagher, <strong>and</strong> R, P. Dahl (eds.),<br />
Structural Change <strong>and</strong> Performance of the U.S. Grain Marketing System, Scherer<br />
Communications, Urbana, IL.<br />
Wailes, E. J., G. L. Cramer, E. C. Chavez, <strong>and</strong> J. M. Hansen. 2000. Arkansas global rice<br />
model: international baseline projection for 2000-2010.<br />
WWW. uark. edu/campusresources/ricersch.<br />
Young, K. B., E. J. Wailes, <strong>and</strong> G, L. Cramer, 1994, Economic Analysis ofR ke Bran Oil<br />
Processing <strong>and</strong> Potential Use in the United States. Ark. Agric. Exp. Stn. Bull. 943.
d i o p t e r<br />
Ríce Harvesting<br />
G ra e m e R. Q u ic k<br />
Deportment of Agricultural <strong>and</strong> Biosystems Engineering<br />
Iowa State University<br />
Ames, Iowa<br />
INTRODUCTION<br />
TIMING OF THE RICE HARVEST<br />
RICE COMBINE HARVESTERS<br />
Need for <strong>Rice</strong>-Special Combines<br />
Custom-Made Rite Combines<br />
CATEGORIES OF RICE COMBINE HARVESTERS<br />
COMBINE FUNCTIONS<br />
Coordinated Functions<br />
Fundamental Rules about Harvester Performance<br />
Adjustments for Optimal Performance<br />
RICE FRONTS, HEADERS, OR PLATFORMS<br />
Conventional Grain Head; Pickup Reel, Cutterbar, <strong>and</strong> Auger<br />
Pickup Reel<br />
Reel Height Setting<br />
Reel Speed<br />
Reel Tine Pitch Setting: Feathering<br />
Reel Fore/Aft Position<br />
Cutterbar<br />
Cutterbar Cutting Height<br />
Cutterbar Register<br />
Cutterbar Speed<br />
Platform Auger<br />
Auger Adjustment<br />
Auger Retractable Finger Pitch<br />
Auger Speed<br />
Stripperheads<br />
<strong>Rice</strong>; Origin, History, Technology, find Production, edited by C. Wayne <strong>Smith</strong><br />
ISBN 0-471-34S16-4 © <strong>2003</strong> John Wiley & Sons, Inc.<br />
491
492 Products <strong>and</strong> Product Processing<br />
How the Stripper Works<br />
Stripper Power Dem<strong>and</strong> <strong>and</strong> Fuel<br />
Stripperheod Weight<br />
Dust Accumulation<br />
Combine Modifications with a Stripperheod Fitted<br />
Australian Tests on Stripperheads<br />
Operating a Stripperheod in <strong>Rice</strong><br />
Combine Adjustments<br />
Vibromat, Draper Front, Windrow Pickup, <strong>and</strong> Lifters<br />
CROP FEEDING AND THRESHING<br />
A Question of Teeth<br />
Threshing Setting<br />
Tailings or Return System<br />
Gauging the Threshing Action<br />
SEPARATION PROCESS: WALKER MACHINES VERSUS ROTARIES (CENTRIFUGAL SEPARATION)<br />
CLEANING SYSTEM<br />
Cleaning System Fan<br />
Cleaning Shoe Sieves<br />
TRASH IN THE BIN<br />
Key Points Affecting Trash<br />
Reducing Trash<br />
MATERIALS TRANSPORT<br />
Grain Bulk Transport<br />
Spreading MOG<br />
Unplugging <strong>and</strong> Quick-Killing a Combine<br />
Quick-killing<br />
Unplugging<br />
RICE COMBINES IN ASIA<br />
POWER THRESHERS<br />
Chinese Threshers<br />
Other Asian Threshers<br />
IRRI Axial-Flow Thresher Developments<br />
Throw-in Threshers That Chop the Straw for Stockfeed<br />
Quantitative Assessment of Power Threshers<br />
TRACTION AND FLOTATION ASSISTANCE FOR EQUIPMENT IN RICE FIELDS<br />
MEASURING AND REDUCING RICE HARVEST LOSSES<br />
Spot-Checking <strong>and</strong> Sampling Losses<br />
Acceptable Loss Level<br />
Combine Loss Monitors<br />
Harvest Delays<br />
HARVESTAND GRAIN QUALITY<br />
St<strong>and</strong>ards for <strong>Rice</strong> Quality<br />
Grain Breakage in Postharvest Operations<br />
Effect of Harvest Delays<br />
MANAGING FIELD OPERATIONS<br />
Assessing Field Efficiencies<br />
Keeping Records<br />
Machine Systems
<strong>Rice</strong> Horvesting 493<br />
Opening the Field <strong>and</strong> Turning<br />
Unloading<br />
Cleaning the Equipment<br />
Summary<br />
PRIVATE OWNERSHIP VERSUS CONTRAaiNG<br />
Managing versus Just Driving Machinery<br />
Contract versus Private Ownership for the Australian Study<br />
Machine Leasing versus Purchasing<br />
Cost Records<br />
Private Ownership versus the Option<br />
Summary<br />
CONTROL AND INFORMATION SYSTEMS<br />
Management Data<br />
CONCLUSIONS<br />
REFERENCES<br />
SUGGESTED READINGS<br />
I i:<br />
INTRODUCTION<br />
Self-propelled combines harvest all die rice grown in industrialized nations. But m ost<br />
o f the world's rice is still h<strong>and</strong>-harvested. In fact, two-thirds o f the global rice crop is<br />
hai'vested by sickles, then threshed by foot or by portable h<strong>and</strong>-fed power threshers<br />
(Figures 4.1.1 to 4.1.3). From the broadacre rice fields o f Australia, Arkansas,<br />
or California to tiny terraces in the Himalayan foothills o f Bhutan, the timing <strong>and</strong><br />
s .<br />
X .<br />
!- -.¿In<br />
Figure 4.1.1. Foot threshing poddy on or elevoted platform mode of bamboo in the Philippines, [Courtesy of the<br />
International <strong>Rice</strong> Research Institute.)
^ :<br />
494 Products <strong>and</strong> Product Processing<br />
Figure 4.1.2. Foot-tfeadie-operated wire loop thresher which <strong>origin</strong>ated<br />
in Japan decades ago <strong>and</strong> is still made in small workshops in many Asian<br />
countries.<br />
costs of tlie harvest are critically im portant. Harvesting <strong>and</strong> h<strong>and</strong>ling the crop can<br />
account for up to 40% o f field costs in the industrialized world (Quick et ah, 1996),<br />
In developing countries, harvest is the single most labor-intensive rice farming activity<br />
(Figure 4.1.4).<br />
TIMING OF THE RICE HARVEST<br />
Ri'i<br />
The timing, duration, <strong>and</strong> mode o f conduct o f die harvest have a direct bearing on<br />
rice quality, efficiency, <strong>and</strong> the rice growers’ income. Delayed or protracted harvest<br />
usually downgrades whole-grain millout at appraisal. <strong>Rice</strong> has its greatest value as<br />
intact kernels or whole grain, unlike many other crops tliat are ground or processed<br />
before sale. Maximum whole grain is affected by season <strong>and</strong> timing o f harvest (Figure<br />
4.1.5). Whether fully mechanized or a h<strong>and</strong> operation, a successful harvest depends on<br />
preharvest management: cultivar selection, tim ing o f establishment, crop care, water<br />
<strong>and</strong> nutrient management, <strong>and</strong> drain-off, as well as the harvest operation itself.The<br />
harvest is a bottleneck, particularly in tlie developing world. Mature paddy is highly<br />
susceptible to losses <strong>and</strong> serious quality downgrading if the harvest is drawn out too<br />
long. On the other h<strong>and</strong>, the higher the grain moisture at harvest (up to a lim it), the
<strong>Rice</strong> Harvesting 495<br />
Figure 4.1.3. Portable power thresher light enough to be h<strong>and</strong>led on shoulder poles across levees into paddy fields,<br />
This photo shows a TC 800 oxiol-flow thresher, the '/2-mi/h groin throughput unit is used in coniunction with a stripper<br />
horvester (see Figure 4.1.23). (Courtesy of the International <strong>Rice</strong> Research Institute.)<br />
H A R V E S TA N D<br />
THRESH<br />
CROP C ARE<br />
C ROP<br />
ESTABLtSHMENT<br />
LAND<br />
PREPARATIO N<br />
3<br />
I<br />
I !<br />
5 10 15<br />
IVIAN.DAYS PER HECTARE PER DAY<br />
20<br />
Figure 4.1.4. Labor dem<strong>and</strong> intensity for semi mechanized paddy field operations in<br />
the Philippines. The labor measure is total person-days required divided by the number<br />
of days available to complete the tosk on 1 ha. Since the denominator (time) is small at<br />
harvest, the relative intensity of labor dem<strong>and</strong> is accordingly much higher at harvest.<br />
(From Douthwoite et oh, 1993,}<br />
higher the whole-grain yield when the rice is milled. Ideal paddy moisture at harvest<br />
is around 20% . W hen grain moisture drops below 18%, crop shattering increases<br />
<strong>and</strong> thresher speeds must be dropped accordingly (Dilday, 1989). Harvest delays also<br />
risk having the grain reabsorb moisture. Rewetted paddy rapidly loses whole grain<br />
mill yield. In labor-scarce regions, mechanized harvest is an imperative. The relative<br />
amounts o f labor for different parts o f the rice world are compared in Table 4.1.1.<br />
Note that there is over 600-fold difference in labor dem<strong>and</strong> between the extremes<br />
in this table. Labor expense as a proportion o f total harvest cost in industrialized
496 Products <strong>and</strong> Product Processing<br />
c<br />
60<br />
2 D1<br />
©<br />
O<br />
£<br />
40<br />
© o><br />
Í2 c©u<br />
20<br />
\ day evaporation<br />
B h arsh ollrnatn<br />
P h y s io lo g ic a l<br />
m at urity<br />
Time of harvest-weeks from maturity<br />
Figure 4.1.5. Grain moisturo vs. whole grain for a rice crop drained on tíme <strong>and</strong><br />
drying down in mild weather, compared with crop drying too fast. Note the resulting<br />
severe fall in whole grain at millout with this vulnerable grain. (From A fSf<br />
AgricuiPjre / 995 <strong>Rice</strong>check Recomenéations; see also Willionis et al., 1995.)<br />
T A B LE 4.1.1.<br />
L a b o r R e q u ire m e n ts fo r th e H a rv e st<br />
Harvest <strong>and</strong> H auling System<br />
No. W orkers<br />
Involved<br />
W orker-Doys/ha<br />
Completely manual harvest: crew with h<strong>and</strong> sickles ■<br />
6 48 (8 days)<br />
<strong>and</strong> h<strong>and</strong> threshing or foot treading<br />
Crew with h<strong>and</strong> sickles, carting to feed power thresher 6 16 (16 h)<br />
<strong>and</strong> winnower<br />
1-m (four-row) Japanese-style combine in good<br />
2 0.6 (2.5 hr)<br />
condition<br />
3-m Thai combine, bagging on board, then to trailer, 5 0.6 (1 h)<br />
transferring bags on the move<br />
8-m combine, bulking with self-propelled chaser bin 2 0.07 (16 min)<br />
countries is 8 to 14%, whereas in Asian countries, where h<strong>and</strong>-cutting followed by<br />
power threshing prevails, it is 60%.<br />
Combine harvesting is considered first in this chapter, followed by the more<br />
widely used but labor-intensive harvesting methods. Combines built for rice differ<br />
from the combines used for m ost other grains (Figure 4.1.6).<br />
RICE COMBINE HARVESTERS<br />
Need for <strong>Rice</strong>-Special Combines<br />
There are several reasons for dedicated rice-special combines (Figure 4.1.7).<br />
1. Crop/field conditions. W liile the grain may be ready at harvest time, the<br />
straw is at a much higher moisture content than tire grain. Paddy at harvest might
Ríes Harvesting 497<br />
mm&mrniiiiiia iaiiiiii<br />
Figure 4.16. John Deere's CTS combine, designed specifically for rice harvesting. This walkerless rice-special<br />
mochine is shown equipped with a stripperfront setting a world record atColuso, in the California rice region. The launch<br />
of the CTS in 1991 represented a significant departure for Deere & Co., which had previously eschewed rotary separotion<br />
in favor of straw walkers. Note the self-propelled grain haul-out wagon olengside the combine. (Photo provided by <strong>Rice</strong><br />
Farimg)<br />
typically have a straw moisture level o f 50 to 70% wet basis, whereas the mature<br />
rough rice moisture level might be 12 to 27% . The fibrous straw is rank <strong>and</strong> tough,<br />
tough enough that in some regions, rice straw is used for making ropes, matting, <strong>and</strong><br />
even shoes.<br />
2. MOG/G ratio. The volume o f straw, or m aterial-other-than-grain (M O G ),<br />
taken in by a cutterbar-equipped com bine is higher for paddy than for other cereals.<br />
For example, the weight ratio for paddy is 1.5 m t o f M O G per m etric ton o f paddy,<br />
compared with 0.8 M O G per m etric ton of wheat. If the paddy is lodged, as it often is<br />
in patches, the MOG/G ratio taken into the combine goes up to 3 or even 4:1. Under<br />
good harvesting conditions, a com bine equipped with a stripperhead will take in far<br />
less straw.<br />
3. Specialty threshing elements. A special cylinder or rotor is usually a necessity<br />
for rice harvesting. Tangential flow harvesters are equipped with a spike-tooth
498 Products <strong>and</strong> Product Processing<br />
'tfij<br />
-r-<br />
J.<br />
P fli'!<br />
, ‘ J -■ - ’S<br />
f ' ‘ ' it' ‘<br />
■’ ': • )• S ‘ ® ''<br />
. r i f ' . ' ■■ i.<br />
m m ’}<br />
-i--<br />
Figure 4.1.7. Squadron of rice combines in the field in southern New South Wales, Australia. Five of the 11<br />
combines tested by the author in the 1996 season are shown. Two of these combines are fitted with stripperheads,<br />
[Kondinir Group photo, used by permission.)<br />
cylinder <strong>and</strong> concave in place o f the rasp-bar type o f drum. The spike-tooth<br />
thresher may be used for other crops but has limitations in more difficult seasons<br />
or conditions, such as removing whiteheads in wheat. On axial-flow combines, a<br />
specialty rotor may be fitted for rice {see Figure 4.1.14).
Rite Harvesting 499<br />
4. Component wear. <strong>Rice</strong> straw <strong>and</strong> paddy are highly abrasive. Rough rice<br />
is tightly encased within the floret bracts or husk that are protective <strong>and</strong> high<br />
in silicaceous material, compounds similar to the key ingredient o f s<strong>and</strong>paper.<br />
The straw is also high in silica. Combines have to be modified for rice fields.<br />
Selected components are made from stainless steel, other alloys, or given hardfacing<br />
treatments to better resist abrasion. The most-affected components include auger<br />
troughs <strong>and</strong> fittings, elevator housings, thresher bars, auger troughs, <strong>and</strong> even<br />
special knife sections for cutterbars. Manufacturers acknowledge that rice is the m ost<br />
abrasive crop h<strong>and</strong>led by their combines.<br />
5. Machine flotation. Heavy ground conditions <strong>and</strong> soft fields require that rice<br />
com bines be built with high underframe clearances. Rear-wheel-assist pusher axles<br />
are st<strong>and</strong>ard on rice combines. Traction <strong>and</strong> flotation aids such as “rice” tires, halftracks,<br />
or even full crawler ground drives are options. Frequently, grain-transporting<br />
equipment has to be parked on firm ground outside paddocks or bays in soft ground.<br />
6. Lodging. <strong>Rice</strong> plants are susceptible to lodging. Prior to the adoption of<br />
high-yielding cultivars <strong>and</strong> laser-leveled rice fields, rice was a long-strawed crop, bred<br />
to grow in st<strong>and</strong>ing water o f variable depths <strong>and</strong> it lodged readily. But even modern<br />
cultivars (M Cs), which mature faster with shorter straw lengths, tend to he green at<br />
hai'vest time, <strong>and</strong> patches or even whole fields may lodge. The machine needs to be<br />
designed accordingly to pick up <strong>and</strong> process this lodged material to avoid massive<br />
grain losses.<br />
7. Threshability. There are over 60,000 cultivars o f rice worldwide. Some<br />
types are tough to thresh, <strong>and</strong> all are vulnerable to m echanical damage by harvest<br />
machinery. The harvesting process needs to beat, com b, rub, or otherwise ease the<br />
grains o ff the panicle <strong>and</strong> out o f the straw, yet not exacerbate grain breakage. Hidden<br />
cracks, <strong>and</strong> skinning or pearling from overthreshing, show up as brokens later at the<br />
rice mill, with subsequent price penalties for the producer.<br />
Less than one-third o f the world’s rice is combine-harvested, but over 90% o f the<br />
rice that is traded across international borders is combine-harvested. On the other<br />
h<strong>and</strong>, only 4% o f the world’s rice crop is traded across national boundaries. M ost rice<br />
is used in the country where it is grown.<br />
Custom-Made <strong>Rice</strong> Combines<br />
The mechanization o f rice harvest in tlie industrialized world has been complete,<br />
rapid, <strong>and</strong> comparatively recent. In the United States <strong>and</strong> Australia, for example,<br />
where the world’s highest-yielding rice crops are grown (8 to 14 tons/ha) tliere practically<br />
never was a stage where commercial rice crops were manually transplanted or cut<br />
by h<strong>and</strong> siclde. Combine-harvesters were adopted contemporaneously in the United<br />
States, Australia, <strong>and</strong> Europe in the 1930s, initially as tractor-drawn machines (Quick<br />
<strong>and</strong> Buchele, 1978). There was a brief phase o f mechanical reaping <strong>and</strong> binding on<br />
rice fields. Combine harvesters built for other cereals would not long withst<strong>and</strong> the<br />
adverse field conditions <strong>and</strong> the wiry <strong>and</strong> abrasive nature o f the rice plant. As a result,<br />
in the 1950s, indigenous manufacturers o f combines, often farmers themselves, were<br />
the mainspring for the emergence of the first self-propelled combines on U.S. rice
500 Products <strong>and</strong> Product Processing<br />
fields. These were made by local entrepreneurs to meet the peculiar dem<strong>and</strong>s of rice.<br />
As a market emerged, the full-line manufacturers turned their attention to rice-special<br />
combines.<br />
CATEGORIES OF RICE COMBINE HARVESTERS<br />
1. Walker types or conventional combines (Figure 4.1.8)<br />
2. Rotaries (see, e.g., Figure 4.1.9)<br />
3. Tangential feed .<br />
4. End feed<br />
The author’s study o f the power <strong>and</strong> weight characteristics o f all types of rice<br />
combines across the rice world, from Russia through Asia to South America, indicates<br />
that combines require 36 kW o f engine power per meter o f gathering width. This is a<br />
power-to-weight ratio o f around 14 kW •m t at typically 1.7 m tp er meter o f gathering<br />
width. Specific power ranged frorn 8 to 16 kW •mt/h grain throughput, depending on<br />
crop yield. These figures are tlie slopes o f linear regression lines based on data from<br />
manufacturer’s specifications. The power parameters for rice are 33% higher than for<br />
other small grains, reflecting the heavier workload <strong>and</strong> the smaller gathering fronts<br />
on rice combines. A class 6 combine, for example, might be fitted with a 20- or 24-ft<br />
cutterbar in rice, compared with a 30-ft cutting width for wheat, on the same model<br />
combine.<br />
Figure 4.1.8. Waiker-type combines vs. rotaries: key crop-processing components inside a European-styie walker or<br />
conventional.combine combine design with tangential feed to the threshing cylinder <strong>and</strong> agitators over the walkers.<br />
Claas/Caterpillar <strong>and</strong> Deer offer hybrid processor versions for rice, by incorporating conventional threshing with rotory<br />
seporation. (From Claas/Caterpillar Lexion combine literature.)
<strong>Rice</strong> Harvesting 501<br />
5 M ATERIALS TRANSPORT<br />
4 CLEANING<br />
3 SEPARATING<br />
sv<br />
2 THRESHING<br />
Figure 4.1.9.<br />
Combine processing functions. (FromCose axial-flowcombine literature.)<br />
The U.S. <strong>and</strong> Australian rice harvest is dominated at present by two combine<br />
br<strong>and</strong>s: Case-IH <strong>and</strong> Deere & Co. But there are other br<strong>and</strong>s, such as Claas/Caterpillar,<br />
New Holl<strong>and</strong> (rice com bines sourced primarily from Belgium ), AGCO (marketing<br />
Gleaner <strong>and</strong> Massey Ferguson), Laverda, <strong>and</strong> Lova et al., marketed for rice.<br />
The new price o f U.S. rice combines on half-tracks in year 2000 was between $210,000<br />
<strong>and</strong> $330,000. Inform ation on lower-cost Asian-built combines will be provided later.<br />
In 1993, a Deere CTS (cylinder tine separation) combine equipped with an 18-ft<br />
Shelbourne Reynolds stripper-header set a new world record haiwest rate o f 45.66<br />
m t o f grain per hour, sustained over 8 hours on a California rice field (Figure 4.1.6).<br />
COM BIN E FUNCTIONS<br />
Irrespective o f the type o f machinery or h<strong>and</strong> operation, the basic harvest processes<br />
<strong>and</strong> die sequence are the same. A com bine is like a factory on wheels. It performs the<br />
following basic functions in a rice field (Figure 4.1.9).<br />
1. Gathering. The gathering head, also known as the platform, header, or front,<br />
divides the crop, <strong>and</strong> concentrates <strong>and</strong> delivers the crop material to the feederhouse<br />
for presentation to the direshing zone elements. Conventional grain<br />
heads use a cutterbar <strong>and</strong> reel to cut <strong>and</strong> pull the crop into the threshing<br />
element. A stripperhead, on the other h<strong>and</strong>, removes the heads <strong>and</strong> threshes<br />
with very little o f the M O G — it slings the harvested material back to the crossconveyor<br />
on the gathering head. Figure 4,1,10 shows the two main models,<br />
<strong>and</strong> Figure 4.1.11 shows the stripping teeth.
502 Products <strong>and</strong> Product Processing<br />
(a)<br />
Figure 4.1.10. <strong>Rice</strong> stripperhead designs of the two licensees of the keyhole slotted-tooth stripping rotor<br />
principle: (o} Shelbourne Reynolds (UK); (¿) AGCO. Inset shows the actual stripping teeth profile <strong>origin</strong>ally<br />
developed in Englond by Silsoe's Wilf Winner.<br />
2. Threshing. The threshing elements accelerate by impact <strong>and</strong> com bing the crop<br />
to detach the grain from the panicles or ears. The two main types of processors<br />
are tangential-flow cylinder threshers <strong>and</strong> axial or rotary thresher-separators.<br />
3. Separating. Straw walkers or rotor elements practically complete the threshing<br />
<strong>and</strong>/or separation o f the grain from the straw or M OG. There is usually a<br />
returns system on board to cope with maladjusted settings or difficult threshing<br />
conditions so that unthreshed heads are recirculated back for rethreshing.<br />
That section is known as the tailings or returns system.<br />
4. Cleaning. The cleaning section does the final separation o f grain from the<br />
chaff, broken straw pieces, <strong>and</strong> trash that comes down from the threshing <strong>and</strong><br />
separation zones. Clean grain is conveyed to the grain tank or bin. Untlireshed<br />
heads are returned to the threshing zone or are threshed by an onboard rethresher.<br />
5. Materials transport. There are materials transport systems throughout the<br />
combine, from header auger to feeder house to bin unloader.<br />
Coordinated Functions<br />
Coordination of the respective components inside a combine is essential if the machine<br />
is to be operated at its most efficient level. W ith the biggest machines costing up<br />
to $400 an hour to operate, efficiency, defined as the highest possible grain tliroughput<br />
at an acceptable loss level, becomes important. The combine cannot process any more
1<br />
<strong>Rice</strong> Harvesting 503<br />
Figure 4.1.11. Teeth <strong>and</strong> weor plates on the Shelbourne Reynolds stripperfront. As the teeth weor,<br />
their horvesting characteristics change; new teeth bring in more trash, worn teeth cause losses. A set of<br />
teeth can harvest 10,000 mt of rice in good conditions, but much less in lodged crop. [Photo by G. R.<br />
Quick.)<br />
crop than the gathering system can "digest,” <strong>and</strong> the overall harvest operation cannot<br />
exceed tlie grain transport or haul-out capabilities. The grain has to be moved away<br />
from the harvester as soon as the com bine bin is full, <strong>and</strong> the ability to do that may<br />
depend on the capacity o f the rice receival depot or elevator to take in the truck or<br />
trailer loads in a tim ely manner.<br />
Fundamental Rules about Harvester Performance<br />
For top performance, harvest equipment must be maintained in good mechanical<br />
condition. No am ount o f adjustment can make up for defective or missing parts; the<br />
m achine needs to be "shinied up” at the beginning o f the season, since paint <strong>and</strong><br />
rust greatly affect cropflow <strong>and</strong> performance. Harvest equipment must be operated<br />
correctly at the right speed settings for tlie particular crop <strong>and</strong> conditions. Correct settings<br />
are a compromise among many parameters: more crop through the processors<br />
(throughput) versus grain losses, clean grain in the bin at the sacrifice o f some grain<br />
out the back, seconds or returns to the thresher <strong>and</strong> machine-broken grain, extra fan<br />
blast <strong>and</strong> a dirty sample in the bin (more trash = dockage), <strong>and</strong> so on (Figure 4.1.12).<br />
Adjustments for Optimal Performance<br />
An adjustment in one area affects performance in another area. Any setting that<br />
increases the amount o f straw or M O G taken in at the front (e.g., cutterbar closer to<br />
ground to gather m ore o f a lodged crop) may overload the straw walkers or separator.
504 Products <strong>and</strong> Product Processing<br />
Figure 4.1.12. Response surface showing the effects of combine<br />
grain throughput <strong>and</strong> WIOG/G ratio on iossesfor an axiai-flow combine in<br />
Arkansas. (From Andrews etoi., 1993.)<br />
Driving the combine too fast or excessive cylinder speed may overload the sieves.<br />
Overloading the engine causes the threshing rotor to slow, inadequate M O G intake<br />
under low-crop-moisture conditions can lead to uneven flow across the platform or<br />
grain damage from the threshing cylinder. Recutting stubbles at corners <strong>and</strong> headl<strong>and</strong>s<br />
can put short stubble pieces in the bin. Producers should consider the following:<br />
1. Each cultivar <strong>and</strong> condition may need a different series of adjustments.<br />
2. Adjustments should be planned <strong>and</strong> made in sequence.<br />
3. Adjustments should be made one at a time.<br />
4. Performance must be checked under normal steady load, because any change<br />
in load can greatly affect performance.<br />
; - I RICE FRONTS, HEADERS, OR PLATFORMS<br />
The principal t>’pes of rice-gathering systems are described below. The purposes of the<br />
gathering head are (1) to gather the grain-bearing portion o f the crop from the field;<br />
(2) to avoid gathering excess material, which greatly affects the processing functions;<br />
<strong>and</strong> (3) to provide enough material to the thresher for the crop to serve as a cushion<br />
<strong>and</strong> minimize grain damage during threshing. Heads-first feeding is highly desirable.<br />
The aim in harvester operation is to keep the crop flowing evenly into the com <br />
bine. The speed <strong>and</strong> capacity o f the entire harvester are determined right at the front.<br />
Forward speed is controlled not by throttle but by the variable-speed ground-drive<br />
control <strong>and</strong> geai’box. Engine speed must be maintained constant to keep the processor<br />
elements running steadily at their predetermined settings. This is essential for best<br />
performance.
<strong>Rice</strong> Harvesting 505<br />
Crop dividers help lift <strong>and</strong> divide the crop ahead o f the platform to improve crop<br />
flow o f gathered material <strong>and</strong> to guide the crop outside the platform to slide gently<br />
past the ends o f the header with m inim al grain loss.<br />
Conventional Grain Head: Pickup Reel, Cutterbar, <strong>and</strong> Auger<br />
Pickup Reel<br />
Reel performance is im portant in providing smooth crop flow into the header <strong>and</strong> tlie<br />
rest o f the combine, <strong>and</strong> there are reel settings for minim um grain shatter. Adjusted<br />
correctly, the pickup reel lifts <strong>and</strong> pushes the crop carefully over the cutterbar. Bat<br />
reels are inappropriate in rice. As the material is cut, the reel fingers sweep the cut<br />
material across the cutterbar <strong>and</strong> apron, or platform, into the path o f the auger. The<br />
auger grabs the material <strong>and</strong> moves it toward the center, where the feeder fingers drive<br />
it under the front elevator or conveyor in the feeder house.<br />
Reel Height Setting. Reel tines need to clear the cutterbar by at least 1 in. (25.4 mm )<br />
under all conditions. The reel bats should be just below the lowest heads; if the reel<br />
is too low, some heads will hang up on the bats <strong>and</strong> be carried around on the reel. If<br />
the reel is too high, the reel bats will shatter grain. In down crops, the reel should be<br />
low enough <strong>and</strong> pitched forward to lift the crop <strong>and</strong> sweep it across the cutterbar. The<br />
reel must be the same height across the width o f tlie header.<br />
Reel Speed. A norm al setting is a reel index setting o f 1.25; for a typical 1.1-m -<br />
diameter reel size, this works out as a rule o f thumb in reel rpm at 10 times the forward<br />
speed in mph. The reel index is the ratio o f reel peripheral speed to forward speed,<br />
in the same units. Combines with automatic reel speed controllers have a typical<br />
range o f 1.1 to 2.0 for the reel index <strong>and</strong>, once a setting is chosen, reel speed changes<br />
automatically when the com bine forward speed changes. The auto reel controller<br />
needs to be calibrated for different tire sizes or header/reel types. The reel index should<br />
be reduced in a down <strong>and</strong> tangled crop.<br />
Reel Tine Pitch Setting: Feathering. Careful adjustment o f the tine pitch is needed to<br />
ensure smooth crop flow into the cutterbar <strong>and</strong> auger. For average conditions, tine<br />
pitch is rearward. In down rice, the tines are set to maxim um pitch to lift the crop<br />
as m uch as possible without carrying material around the reel or dropping it on top<br />
o f the auger. This will allow the cutterbar to be operated several inches clear o f the<br />
ground, avoiding soil pickup <strong>and</strong> leaving any dead or rotting straw behind.<br />
Reel Fore/Aft Position. In general, the reel is set more forward, the faster the travel<br />
speed; but teeth must not hit tlie cutterbar or auger in its lowest position. Exact<br />
position depends on crop height <strong>and</strong> condition.<br />
Cutterbar<br />
There are some cutterbar variants available for rice, other than the st<strong>and</strong>ard 3-in. knife<br />
<strong>and</strong> guard com bination; tliese include the 1.5 Kwik-Cut (3-in.-stroke double cut),
Products <strong>and</strong> Product Processing<br />
twin laiife (Busatis balanced countercut), <strong>and</strong> the 3X 2 com bination (Herscliers <strong>Rice</strong><br />
Bar with 3"in. sections moving overstroke across fixed 2-in. sections. There are also<br />
3-in. knife sections available for rice with a slotted profile for trash or green material<br />
clearance, <strong>and</strong> special metal-plating treatments on knife sections to extend life. In<br />
every design, sections with serrated cutting edges are essential for rice.<br />
Cutterhar Cutting Height. The cutter bar is normally set just low enough to gather the<br />
m ajority of tlie heads without gathering an excess amount of M O G. In weedy conditions<br />
the cutterbar m aybe set higher to reduce the am ount o f green material entering<br />
the processor, to improve the separating <strong>and</strong> cleaning functions. A loss o f some grain<br />
may be better than overloading the processor with excessive green material, which<br />
may lead to time lost unplugging the combine.<br />
Cutterhar Register. This is very critical in rice because rice has tough-strawed crop<br />
that is difficult to cut. Knife sections must center exactly under the guards at the endof-stroke<br />
position, or for an overstroking knife (e.g., 3,5-in. stroke in 3-in. guards,<br />
Herschefs 3-in. Iqiife over 2-in. guards, or 3-in. stroke in Kwik-Cut 1.5-in. knife) the<br />
knife sections must register, move an exactly equal distance each side of the guards<br />
or counter-edges. Failure to check tlie register results in poor cutting, material clogging<br />
the Imife, uneven feeding over the platform, or in extremely heavy conditions,<br />
premature knife drive or knifeback failure.<br />
Cutterbar Speed. Some conditions make it desirable to change cutterbar speed outside<br />
the manufacturer’s set drive speed, by means o f a pulley change. A higher cutterbar<br />
speed enables faster forward speeds or better performance in tough wet-cutting<br />
paddyfield conditions if those conditions are likely to be sustained for m uch o f the<br />
season.<br />
Platform Auger<br />
Auger Adjustment. The auger should be positioned as high as possible but sufficient<br />
to be able to move the crop uniformly without slugging, bunching, or delaying crop<br />
movement. The auger flights should just clear the stripperbar so that the crop is<br />
not carried over <strong>and</strong> around the auger. A norm al clearance (factory setting) would<br />
be 3 m m (| in.) between stripperbar <strong>and</strong> auger flights. Normally, auger clearance<br />
above the header bottom should be about 12 m m (| in.). For heavy crop conditions,<br />
clearance can be lifted to 1 in. for greater header capacity <strong>and</strong> less carryover by the<br />
auger. For tough green straw the auger may need to be adjusted closer to the header<br />
bottom , but the auger must not scrape or there will be excessive com ponent wear.<br />
Auger Retractable Finger Pitch. The factory setting has the auger retractable fingers in<br />
the raised or "early extended” position to cope with maximum rice yields; in less than<br />
maximum-yielding crops, the adjuster may be used to extend the fingers <strong>and</strong> pitch<br />
them toward the feeder, to facilitate crop feeding.<br />
Auger Speed, In high-yield conditions, increasing auger speed will increase header<br />
capacity <strong>and</strong> improve crop flow. In low-yielding crops, slowing the auger may be<br />
desirable to reduce grain shatter at the auger <strong>and</strong> reduce platform grain losses.
<strong>Rice</strong> Harvesting 507<br />
Stripperheads<br />
Stripper fronts harvest up to 40% o f U.S., Australian, <strong>and</strong> South American rice. The<br />
stripperhead suits the rice cultivars grown in those countries, with their dense crop<br />
canopy <strong>and</strong> relative ease o f threshability. Spot-harvest rates exceeding 1 mt/min have<br />
been recorded in rice from combines with stripper harvesters (Q uick <strong>and</strong> Hamilton,<br />
1997). Grain loss at the front is m uch higher than for a cutterbar but is stiU at<br />
a generally acceptable level in rice at norm al to high grain moistures. Contractors<br />
appreciate the increased throughput, reduced fuel consumption, <strong>and</strong> lower processor<br />
com ponent wear with stripperheads on combines. Harvesting lodged crops is<br />
easier <strong>and</strong> much faster with a stripperfront (at least later in the rice season) than<br />
for a cutterbar under some conditions. The amount o f trash in tlie bin sample can<br />
be higher than with a cutterbar-equipped com bine. Recent research on rice trash<br />
showed that trash could be reduced with higher fan speed <strong>and</strong> faster travel but is<br />
aggravated at slow forward speeds, <strong>and</strong> in lodged crop conditions. One form o f trash<br />
is tails (pedicels) on good grain. These are variety-specific <strong>and</strong> are m ore likely to show<br />
up on paddy harvested by combines with stripperfronts. The entire paddy h<strong>and</strong>ling<br />
system is affected by tails on good grain. A high proportion o f grain with tails is<br />
discharged as trash at storage by the scalper screens (preseparators), <strong>and</strong> valuable<br />
good grain is lost accordingly. The stripper can increase grain throughput, primarily<br />
by permitting higher forward speeds. It does this by reducing M O G intake by a factor<br />
o f 3 or more <strong>and</strong>, as a consequence, improves grain separation efficiency <strong>and</strong> com bine<br />
performance.<br />
»[•<br />
Howthe Stripper Works<br />
The British-designed keyhole slotted-rotor type o f stripperhead has been rapidly<br />
adopted for rice harvest in the United States, Australia, <strong>and</strong> Soutli America since it<br />
was first tested in rice in 1989 in Australia. Rows o f flexible stripping teeth on the<br />
rotor pass upward through the crop, removing grain <strong>and</strong> a small proportion of the<br />
M O G (Figure 4.1.10). Depending on crop conditions, M O G intake is reduced <strong>and</strong><br />
the rotor threshes 50 to 95% o f the grain. This capability means that forward speed<br />
<strong>and</strong> grain throughput can even be doubled over that o f a cutterbar head in good rice<br />
field conditions. Trash levels need to be constantly m onitored however. The stripper<br />
rotor has an unusual characteristic: Its gathering efficiency improves with forward<br />
speed. Losses are higher at very low speed, <strong>and</strong> the am ount o f straw taken in at low<br />
speed is much higher as well. The stripper rotor performs best witli a crop curtain<br />
or wall to prevent grain flying out the front or sides. Thus a stripperhead should be<br />
slightly narrower (say 90% ) than a conventional grainhead (e.g., an 18-ft stripper<br />
compared with a 2 0 -ft cutterbar on a 180-hp class 5 com bine, or a 20- to 22.5-ft<br />
stripper compared with a 25-ft cutterbar on a 260-hp class 6 com bine).<br />
Stripper Power Dem<strong>and</strong> <strong>and</strong> Fuel The stripper rotor itself has a higher power dem<strong>and</strong><br />
than that o f a cutterbar (e.g., 12 kW/m), so the com bine must have the shaft drive<br />
power takeoff to the front to cope with the power requirement. A compensation is<br />
that the rest o f the com bine is less loaded, <strong>and</strong> there are some data to show that<br />
under equivalent conditions fuel consumption is reduced by more than 20% with a<br />
stripperhead fitted in rice compared with the same machine fitted witli a conventional
508 Products <strong>and</strong> Product Processing<br />
cutterbar head. Older combines may need extensive modification to be able to support<br />
<strong>and</strong> drive a stripperhead.<br />
Stripperhead Weight. The stripperhead is more than 30% heavier than conventional<br />
cutterbar heads, <strong>and</strong> this requires adjustment to the combine gathering head hydraulic<br />
settings to reduce drop rate. Damage can result if the head lowers too fast.<br />
Greater care must also be exercised when driving, to avoid the combine nosing over.<br />
If the rear wheels o f a combine lift, steering control is lost.<br />
Dust Accumulation. The nature of the stripping process means that there is more dust<br />
at the front. Also, the airflow entrained by the rotor has to be allowed to escape before<br />
the feeder or trash can be higher.<br />
Combine Modifications with a Stripperhead Fitted. The position o f the front roller o f<br />
the feed elevator must be modified to enable even feed; other changes involve closing<br />
the clearance to account for the reduced M O G input to the processing elements.<br />
Concave blanking plates or, in the case o f rotary combines, a number of rotor/concave<br />
modifications are desirable with a stripperhead fitted, <strong>and</strong> these are specific to each<br />
combine model.<br />
if:?<br />
Australian Tests on Stripperheads. Tests in Australia (Q uick et al., 1995; Quick <strong>and</strong><br />
Hamilton, 1997) showed that stripper fronts consistently increased capacity on suitably<br />
adapted combines. Strippers had higher gathering losses than a cutterbar, but<br />
the losses were within acceptable limits in high-yielding rice. There was no significant<br />
difference in grain quality between strippers versus cutterbar fronts in Australian tests<br />
or between rotaries <strong>and</strong> walker-type combines. Lodged rice changed the gathering<br />
performance greatly <strong>and</strong> increased stripper tooth wear. The stripperhead was superior<br />
in gathering lodged plants <strong>and</strong> under windy conditions. Performance in low-moisture<br />
wheat was less than acceptable in terms o f grain losses.<br />
Operating a Stripperhead in <strong>Rice</strong><br />
The m ain settings for tlie stripperhead are rotor speed, rotor hood position, <strong>and</strong><br />
rotor height. In good crop conditions, stripper rotor speed is best at 500 to 600 rpm,<br />
depending on crop moisture. Higher rotor speed helps gatliering but increases straw<br />
intake, <strong>and</strong> the stripper teeth wore out faster. The aim is to position the rotor <strong>and</strong><br />
stripperhead as high as possible to keep straw intake down but low enough to lift <strong>and</strong><br />
remove panicles, including those that are bent over. The com bine grain loss m onitor<br />
can be used as a guide to gauge the best forward speed. In lodged plants the rotor<br />
must be lower <strong>and</strong> forward speed reduced. Rotor power increases markedly in lodged<br />
conditions because straw intake is higher. Thus the rotor rpm will tend to fall <strong>and</strong><br />
the slip clutch may engage (a rotor speed m onitor provides a warning o f im m inent<br />
overload). Combining into the direction o f lay rather than with or perpendicular to<br />
the direction o f lodged crop will improve efficiency. Despite the stripper’s potential to<br />
double combine capacity, lower the fuel consumption, <strong>and</strong> reduce wear o f processor<br />
components under the right conditions, some farmers leave their stripperhead in the<br />
shed for the wheat crop, preferring the cutterbar header, in order to minimize grain<br />
losses.
Rke Harvesting 509<br />
Combine Adjustments. The threshing system’s concave clearances need to be closer<br />
with a stripperhead, to account for the m uch smaller M O G throughput (unless the<br />
crop is lodged). In some combines (e.g., Case axial flow), different concave grates<br />
are needed. Also on the Case 1688 through 2388 models, extra “elephant ears” (four<br />
instead o f two) should be fitted on the specialty rice rotor cone. Fan speed needs<br />
to be faster <strong>and</strong> the sieves opened to cope with the extra grain tliroughput. The<br />
straw left st<strong>and</strong>ing behind a stripper poses fresh challenges in field management.<br />
A cutterbar attachment behind the stripper front might be a desirable option for<br />
stubble- retention farming. In wheat, stripper fronts were not economically feasible<br />
because o f grain losses at the front under low-moisture conditions (say, below 15%<br />
grain moisture). A stripperhead can cost over $40,000 depending on width, <strong>and</strong> there<br />
are expenses of up to $5000 to modify the concaves <strong>and</strong> other com ponents for certain<br />
combines. The wear o f stripper teeth is another factor that needs to be included in the<br />
overall costing because the teeth can be worn out in a season under heavy contractwork<br />
conditions (Figure 4.1.11). Stainless steel stripper teeth are a recent adaptation.<br />
Additional area will need to be harvested to amortize the extra capital; otherwise, the<br />
unit costs to harvest with a stripperhead will be higher than for a cutterbar on smaller<br />
areas, despite increased capacity.<br />
Vibramcit, Draper Front, Windrow Pickup, <strong>and</strong> Lifters<br />
If a cutterbar is used, a Vibram at is a highly cost-effective attachment that will reduce<br />
gathering losses stdl further <strong>and</strong> improve crop flow. Windrow pickups <strong>and</strong> lifters will<br />
work in severely lodged crops, but are rarely used these days for rice. The draper<br />
front is an expensive option, but it st<strong>and</strong>s out exceptionally well in aU conditions.<br />
Advantages o f the draper are the ability to fit a wider head, smoother flow into the feed<br />
elevator, <strong>and</strong> a higher level o f heads-first feeding that improves overall performance<br />
o f the processor.<br />
CROP FEEDING AND THRESHING<br />
After culling, the crop is conveyed up the feederhouse to the threshing zone. As for the<br />
gathering front, the aim for top performance in a well-coordinated com bine is to have<br />
smooth crop flow, without unevenness, slugs, or bunches o f material. Slugs o f crop<br />
impede threshing, change cylinder momentum , <strong>and</strong> increase losses. A good operator<br />
fine-tunes threshing settings to the conditions at the tim e; sudden deviations in crop<br />
flow rate upset those settings <strong>and</strong> cause losses. W ith the conventional tangential-flow<br />
thresher, both cylinder <strong>and</strong> concave are usually fitted with spike teeth for rice (Figure<br />
4.1.13). Raspbars used for cereals generally do not have enough traction to cope<br />
smoothly with the greater volume o f the tough <strong>and</strong> m ore-m oist rice straw, although<br />
they still do a good jo b of dislodging the grain. A raspbar drum can, however, be<br />
used with a stripper front installed. The spilce-tooth cylinder can be used for other<br />
small grains. On the other h<strong>and</strong>, the thresher should be set to leave the straw as nearly<br />
whole as possible, to make it easier for the kernels to fall tlirough die straw mat moving<br />
over the wallcers. Using fewer rows o f teeth on the concave reduces straw smashing.<br />
Only sufficient concave teeth should be installed to delay the straw long enough on its
510 Products <strong>and</strong> Produrf Processing<br />
Figure 4.1.13. Conventional spike tooth cylinder <strong>and</strong> concave<br />
adjusters. (From Laverda SPoltaly literature.}<br />
passage through the threshing zone to allow the grains to be loosened the impact<br />
<strong>and</strong> combing action o f the thresher. Excessively broken straw overloads the cleaning<br />
system <strong>and</strong> puts trash in the bin.<br />
A Question of Teeth<br />
M ost rice combines with tangential-feed cylinders use spike-tooth threshing cylinders<br />
with peg-type concaves. Some use several cylinders in series. Claas/Caterpillar, for<br />
example, uses a three-cylinder tangential feed threshing configuration with an accelerated<br />
preseparation cylinder at the front running at 80% o f main cylinder speed (650<br />
rpm in rice). The spikes or peg teeth pull the straw bulk through the machine to comb<br />
out the grain as gently as possible <strong>and</strong> to maximize the opportunities to thresh all the<br />
gram out o f the heads as it passes through the com bine body. Even the Case axialflow<br />
com bine needs a specialty rotor for rice (Figure 4.1.14), All the combines have a<br />
returns system which brings any untlireshed heads back from the cleaner for a second<br />
threshing operation. The aim is to keep processor grain losses below 3% at maximum<br />
throughput (see ASAE St<strong>and</strong>ard S 343.3 <strong>and</strong> Figure 4.1.31).<br />
Peg teeth have a long ancestry, <strong>and</strong> despite over 200 years o f development, they<br />
may look surprisingly similar to the earliest patented designs, which were <strong>origin</strong>ally<br />
intended for wheat. Nowadays, however, pegs or splice teeth are seldom used in wheat<br />
fields. This is because modern wheats mature faster <strong>and</strong> at harvest have stiff <strong>and</strong> brittle<br />
straw easily broken or chopped up by peg teeth, thus causing very high grain losses,<br />
a factor also deterring adoption o f stripper fronts for wheat. The peg-tooth cylinder<br />
is more aggressive <strong>and</strong> the greater num ber o f contacts witli the pegs is needed for the<br />
fine, tough, <strong>and</strong> wiry pedicels <strong>and</strong> fibrous stems o f Oryza sativa spp.<br />
Straw pieces put an excessive load on the com bine cleaning system. This is reduced<br />
if the smoother raspbar thresher system is used. Rasp bars can be used for a<br />
rice crop if the crop is dry enough, but very few seasons are that dry. The adoption of
Ríce Harvesting 511<br />
Figure 4.1.14.<br />
Ctise-IH axial-flow specialty rotor for rice. (Photo by G. R. Quick.)<br />
stripperheads makes it possible to use the raspbar drum successfully, which facilitates<br />
changeover to hai-vest other crops if conditions are favorable for stripping.<br />
Threshing Setting<br />
The cylinder/rotor <strong>and</strong> concave should be adjusted to detach practically all the grain<br />
from the panicles <strong>and</strong> separate as much grain as possible from the M O G at the threshing<br />
zone while causing minimal straw breakup <strong>and</strong> damage to the grain. Generally a<br />
higher cylinder speed <strong>and</strong> wide concave clearance will provide the greatest capacity<br />
<strong>and</strong> the fewest problems in separating <strong>and</strong> cleaning. One argument in favor o f rotary<br />
combines is that the rotor can run with wide clearances, thereby ensuring a gentle<br />
thresh. Claas/Caterpillar argue for their 20% slower preseparating cylinder (the first<br />
of three in a series o f drums), <strong>and</strong> Deere runs its CTS prim ary threshing cylinder<br />
slower to leave the remaining threshing task to their twin axially aligned separating<br />
cylinders behind the prim ary cylinder so that they can get grain out o f the threshing<br />
zone early, to keep down grain damage levels.<br />
This is how the best settings are arrived at in rice;<br />
1. Prim ary threshing cylinder or rotor speed should be adjusted so that it operates<br />
as fast as practicable without causing serious grain damage <strong>and</strong> skinning<br />
or pearling in the bin sample. For rice, cylinder/rotor tip or top speed should<br />
typically be around 25 to 32 m/s. The spike cylinder on Deere’s CTS, on the<br />
other h<strong>and</strong>, is recommended at 14 to 19 m/s tip speed (400 to 550 rpm on that<br />
machine). The slower-moving cylinder on the CTS has 12 rows o f teeth (three
512 Products <strong>and</strong> Product Processing<br />
rows on the concave). A significant proportion o f the threshing is meant to be<br />
completed by tlie CTS counterrotating separator cylinders running at a fixed<br />
700 rpm.<br />
2. Set cylinder-concave clearance by steps, starting with wide setting <strong>and</strong> narrowing<br />
until close enough to just thresh out the grain without too much<br />
pearling. Five percent pearled rice grains is a suggested maximum. There is<br />
an inverse relationship between threshability <strong>and</strong> grain damage: As cylinder<br />
speed is increased, the am ount o f unthreshed heads is reduced, but the damage<br />
is greater.<br />
Tailings or Return System<br />
Unthreshed heads that make it past the thresher can be collected over the chaffer sieves<br />
<strong>and</strong> recycled, to be returned by the tailings return system to face the threshing action<br />
a second time.<br />
Gauging the Threshing Action<br />
|: ,<br />
1. Visually inspect the grain in the tank. Receiving station operators should also<br />
check samples to assess dockage <strong>and</strong> grower returns.<br />
2. Check the tailings return flow through the inspection port. Excessive tailings<br />
will lead to grain damage. Hidden damage is more difficult to detect since<br />
it shows only after milling. Som e operators trade off between pearling <strong>and</strong><br />
tads (pedicels) on rice grains o f certain cultivars. W hole-grain m illout declines<br />
with higher pearling. M onitor the' sample regularly for trash levels <strong>and</strong> degree<br />
of pearling,<br />
3. Examine the straw discharged out the rear o f the com bine. It should contain<br />
only the occasional low-quality grain in the otherwise empty panicles or<br />
heads.<br />
4. Do a combine "quick-kill” (see the section "Unplugging <strong>and</strong> Quick-KiUing a<br />
Combine”).<br />
SEPARATION PROCESS: WALKER MACHINES VERSUS ROTARIES<br />
(CENTRIFUGAL SEPARATION)<br />
The traditional walker type of separation system relies on gravity to sort the grain out<br />
of the MOG. Nowadays, walkers are as long as 5 m <strong>and</strong> are driven at around 200<br />
rpm. Higher M O G throughputs overload a walker to the point that the grain cannot<br />
penetrate the straw in time <strong>and</strong> grains “walk” out the rear o f the combine. Walker<br />
loss has been known to be a problem for some models o f walker-type combines,<br />
especially in rice. To get around this, machine designers have relied on increasing<br />
body width to thin out the straw m at <strong>and</strong> increase crop-processing capacity while<br />
trying to get below the elusive 3% machine loss criterion. This design has a limit,<br />
set by body envelope <strong>and</strong> roadable width Agitators over the top o f the wallcers are<br />
offered by European manufacturers to improve, separation performance. Deere came
<strong>Rice</strong> Harvesting 513<br />
halfway with their CTS rice special, a machine with regular tangential-flow threshing<br />
(spike-tooth 12-row cylinder) combine, then axially aligned twin cylinder separation;<br />
but the full distance with their single-tine separator (STS) combine models. Models<br />
o f the Claas/CaterpiUar Lexion combine series have twin rotor separation, as does the<br />
T R series from New Holl<strong>and</strong>. The extreme example of the approach o f using multiple<br />
rotors are the claas CS combines, which use eight cylinders in series for separation.<br />
The crop travels full circle around the rotor in rotary thresher/separators. The<br />
Case, Deere STS, Gleaner, W hite, <strong>and</strong> AGCO/MF rice combines fall into this category.<br />
Centrifugal force drives the grain through the straw <strong>and</strong> out o f the concaves/grates.<br />
The principal advantage over gravity-dependent walkers is that separating forces o f<br />
up to 200 g ’s are generated to propel the grain through the straw mat; this is 10 times<br />
higher than is possible with walkers. The crop material might pass around the rotor<br />
from four to as many as a 12 times in the process o f being Üireshed <strong>and</strong> separated.<br />
Straw breakage is m uch higher than with walker separation, but that is o f little<br />
concern with rice. Transport or guide vanes in the rotor cover control the rearward<br />
m otion o f the crop around the rotor as it progresses over the concave <strong>and</strong> separator<br />
grates. Transport vane angle settings can be adjusted on several models. A high-niertia<br />
rice specialty rotor with multiple wear-resistant elements is needed for processing<br />
tough-stemmed <strong>and</strong> abrasive crops. The Case rotor is shown in Figure 4.1.14.<br />
The following advantages are claimed for rotary separators over walker separators:<br />
1. Smaller m achine envelope<br />
2. Reduced number o f moving components<br />
3. Less drives <strong>and</strong> drive assemblies<br />
4. Lower machine vibration levels<br />
5. Less sensitivity to rotor speed/clearance<br />
6. Higher rotor inertia<br />
7. Lower grain damage<br />
8. Lower com bine weight<br />
Regardless o f the system used, correct walker or rotor speed is critical to the<br />
separation process. Too-high rotor speeds damage grain <strong>and</strong> tend to bounce or propel<br />
grain over or out o f the separator; slow speeds allow excessive straw <strong>and</strong> chaff to<br />
reach the cleaning area. Generally, a walker speed change from the factory setting is<br />
not recommended. W ith rotary combines, there is less sensitivity to rotor speed <strong>and</strong><br />
concave clearance changes, <strong>and</strong> concave clearances are usually larger (e.g., 12.7 m m<br />
for the front o f the cylinder versus say 25.4 m m for the Case rotor-concave clearance<br />
in rice).<br />
Drawbacks to rotary separators are that they can be m ore sensitive to changing<br />
crop moisture levels, require m ore specific power than do walker separators break up<br />
tlie straw more, <strong>and</strong> can take longer to unplug if overloaded.<br />
CLEANING SYSTEM<br />
The cleaning fan, adjustable chaffer, <strong>and</strong> sieves function together to fluidize material<br />
<strong>and</strong> remove the fine straw pieces, chaff, <strong>and</strong> dust mechanically from the grain. As
514 Produtfs <strong>and</strong> Product Processing<br />
much air should be used as possible. Many modern combine models use twin outlet<br />
winnowing systems» the first airstream being used to prewinnow the grain stream<br />
before it reaches tlie cleaning shoe area. The second airstream floats the shoe load<br />
coming off the grain pan to markedly assist cleaning performance. Adjustable sieves<br />
are usually set manually from the rear, the sieve openings being measured from the<br />
tip o f one vane to the tip o f the next forward vane.<br />
Cleaning System Fan<br />
W ind should be adjusted for maximum usable air volume without blowing clean grain<br />
into the tailings or out the rear o f the combine. Airflow across the width o f the shoe<br />
(typically 6 to 8 m/s at the fan) must be as uniform as possible <strong>and</strong> should decrease<br />
from front to rear of the shoe. W ith larger crop flows (e.g., when the combine carries<br />
a stripperhead) or in a very dense crop, even more air is directed to the front of the<br />
chaffer (a three-section upper sieve) using the adjustable windboard, to compensate<br />
<strong>and</strong> improve cleaning. After setting the airflow, the chaffer sieve is set incrementally<br />
until further closing would cause excessive tailings return. The (lower) sieve is set in<br />
the same way.<br />
Cleaning Shoe Sieves<br />
M ost combines can be fitted with different types o f sieves according to crop type.<br />
For rice <strong>and</strong> small-grain cereals, the l| -m . adjustable Closz slat-type chaffer sieve is<br />
suitable, initially set at a - -in. opening. The shoe sieve is set at -¡I-in. initially. The<br />
rear section o f the chaffer sieve (chaffer extension) may be raised to retard material<br />
movement for better cleaning <strong>and</strong> less loss in light-crop conditions.<br />
TRASH IN THE BIN<br />
Trash, extraneous matter com ing from the harvest fields, is a direct cost to the ricegrower.<br />
<strong>Rice</strong> trash occupies five to 10 times the volume of an equivalent weight o f<br />
paddy. Trash adds to transporting, storing, <strong>and</strong> drying costs; affects stored paddy<br />
quality; takes up costly storage space; <strong>and</strong> reduces milling capacity. A detailed study<br />
o f the rice trash problem in Australian rice fields (Quick, 1998a; Q uick et al., 1999)<br />
produced the following conclusions: Australian rice growers are docked for trash<br />
levels above 1.5%; samples from truck deliveries had trash levels ranging from 0.01 to<br />
35% , with an average o f 1,42% in 1996, a year with low levels o f lodging. A level of<br />
2% trash becomes visibly apparent in a truckload of rice.<br />
Key Points Affecting Trash<br />
1. Crop <strong>and</strong> environment factors. These factors significantly affected trash levels<br />
collected by the harvesters. First, <strong>and</strong> forem ost was the degree o f lodging, then grain<br />
moisture content, rice cultivar, <strong>and</strong> finally, location. Harvest delays exacerbated trash
<strong>Rice</strong> Karvesfíng 515<br />
Figure 4.1.15. Graie moisture <strong>and</strong> trash levels plotted against time in<br />
the season over the period March through April 1997, cultivar Amoroo, in<br />
New South Wales, Australia. Exponential regression lire plotted to data.<br />
(from Quick et al., 1999.)<br />
problems. Trash levels increased later in the season as the grain moisture content<br />
declined in tlie field (Figure 4.1.15). HaiTest delays also exacerbate crop lodging.<br />
2. Type of harvester. Older combine designs were found to produce significantly<br />
lower trash levels than later models. Perhaps higher processor loss levels <strong>and</strong><br />
proportionately larger cleaning shoes <strong>and</strong> restrictions on higher throughputs (such<br />
as engine power <strong>and</strong> operator care) may explain why earlier models produced<br />
a cleaner sample than late models. On the other h<strong>and</strong>, one o f the best overall<br />
performances in terms o f low trash, high capacity, <strong>and</strong> low processor grain losses<br />
was a highly skilled owner with his 22-year-old W hite 9720/stripper front harvesting<br />
com bination. Perhaps the veteran machines are managed m ore skillfully with an<br />
experienced operator,<br />
3. Stripper fronts. Combines with stripper fronts averaged 0.5% higher trash<br />
than did cutterbar-equipped combines across all br<strong>and</strong>s <strong>and</strong> models (Figure 4.1.16).<br />
Operators reported that stripper fronts facilitated operation in lodged crops, boosted<br />
Figure 4.1.16. The higher the comhine for speed, the lower the trash in the sample in a<br />
rice field. Regression lines fitted to dota from walker <strong>and</strong> rotary separators compared from<br />
several combines of each type. (From Quick et al., 1999.)
516 Producís <strong>and</strong> Product Processing<br />
throughput performance of walker machines, <strong>and</strong> performed better than a cutterbar<br />
in windy conditions. But gathering losses were always m uch higher with a stripper<br />
front than with a cutterbar. For example, an upright crop was 1.5 to 3.5% with a<br />
stripper front compared with 0.5 to 1% for cutterbars <strong>and</strong> trash levels o f 2.6% vs.<br />
2.03% in the 1997 harvest, a year with substantial lodging. Losses at the in-crop<br />
edges o f the two br<strong>and</strong>s o f strippers were severe in lodged conditions if dividers were<br />
damaged or missing.<br />
4. Machine settings. Generally, higher forward speeds reduced trash. If the<br />
machine can be kept loaded <strong>and</strong> running steadily with less tim e maneuvering in <strong>and</strong><br />
out o f crop, the processor <strong>and</strong> cleaning system will perform better. O f all machine<br />
adjustments, the fan speed setting was the m ost sensitive factor affecting trash<br />
(Figure 4.1.17). The higher the fan speed, the lower the trash, but at the cost o f an<br />
increase in losses out the back. A change in fan speed o f only 300 rpm could lead to a<br />
doubling in trash level with some combines. Sieve settings had little impact on trash.<br />
Cylinder speed <strong>and</strong> concave settings greatly affected the degree o f pearling (paddy<br />
dehusking) but were not closely linked to trash level. Pearling increased sharply with<br />
higher cylinder or rotor speed, <strong>and</strong> whole-grain m illout declined accordingly.<br />
Reducing Tmsh<br />
A level of 2.5% trash in loads from a 1-m illion m t rice crop would am ount to enough<br />
trash to interfere with drying <strong>and</strong> take up the space o f over 100,000 m t o f paddy.<br />
Trash can be reduced by selection o f cultivars, crop management to avoid lodging,<br />
harvesting early or minimizing delay, by attention to details in machine operation,<br />
<strong>and</strong> keeping up fan <strong>and</strong> forward speeds consistent with acceptable loss level. Cleaning<br />
system loading must be monitored for effects on trash in the sample. Feedback at the<br />
depot at the time o f delivery o f each load will increase the lilcelihood that an operator<br />
will set the harvester to minimize trash. Organic trash <strong>origin</strong>ates on the farm. That’s<br />
the best place to leave trash.
<strong>Rice</strong> Harvesting 517<br />
MATERIALS TRANSPORT<br />
The combine has many conveying functions. These include conveying cleaned grain<br />
to the grain bin (clean grain conveyor <strong>and</strong> bubble-up); returning tailings to the<br />
thresher (takings elevator or conveyors); discharging threshed material residues, usually<br />
by a beater onto straw <strong>and</strong> chaff spreaders, or straw chopper/spreader (where<br />
fitted); <strong>and</strong> the grainbin unloading system. The returns <strong>and</strong> clean grain elevators <strong>and</strong><br />
all the augers are areas prone to high wear in rice <strong>and</strong> should be fitted with special<br />
' rice components, such as stainless steel sheet metal inserts <strong>and</strong> steel or wear-resistant<br />
plastic elevator paddles <strong>and</strong> auger flighting.<br />
Grain Bulk Transport<br />
Clean paddy from the cleaning system should be gently conveyed to the grain bin.<br />
Unloading from the combine grainbin on-the-move saves precious field time, but<br />
the combine must have the power to harvest <strong>and</strong> unload simultaneously. Grain is<br />
unloaded into a m other bin or a truck driving alongside if field conditions are firm<br />
enough, or into a tractor-drawn grain cart or self-propelled chaser bin (Figure 4.1.6),<br />
The unloader spout should be retracted when not in use to avoid the risk of running<br />
it into obstacles such as trees or power poles.<br />
Spreading MOG<br />
The body o f the com bine concentrates crop material into a narrow swath or header<br />
trail by a factor o f 3 to 6. This factor is the ratio o f header or front width to processing<br />
body width. Unless M O G is baled, the resulting header trails present problems<br />
in tillage <strong>and</strong> l<strong>and</strong> preparation, as well as seeding a volunteer crop or providing<br />
harborage for pests <strong>and</strong> diseases. An increasing num ber o f farmers are practicing<br />
some method o f reduced tillage, so a M O G-distribution system or spreading attachm<br />
ent is essential. Straw choppers, while power-dem<strong>and</strong>ing on the combine, can save<br />
field operations by breaking up <strong>and</strong> shredding the crop residues for more even field<br />
distribution by tlie straw spreaders. Tests have shown that spread-<strong>and</strong>-incorporated<br />
straw increases the yield o f subsequent crops as well as providing a useful habitat for<br />
beneficial species. On Californian rice fields, which are on the flight path of migratory<br />
bird species, straw management without burning is m<strong>and</strong>atory. Some rice growers<br />
elsewhere take the less environmentally friendly route <strong>and</strong> burn their header trails or<br />
windrows when that practice is not forbidden.<br />
Unplugging <strong>and</strong> Quick-Killing a Combine<br />
Quick-Killing<br />
Quick-killing or a key-stop is a diagnostic tool for perceptive com bine operators.<br />
The procedure involves a stepwise sequence under the right conditions to stall the<br />
processing elements deliberately while the machine is fully loaded with crop.
518 Products <strong>and</strong> Product Processing<br />
W arning: Consult the operator’s manual; if the correct sequence is not used,<br />
turbocharged engines may be damaged <strong>and</strong> there are operator safety hazards if done<br />
improperly. W ith the engine stopped <strong>and</strong> key removed, the processing areas can be<br />
studied to assess machine performance when the covers are lifted. If there are loose<br />
grains in the agitated material inside the rotor near the rear o f the grates in a rotary<br />
com bine, for example, this may suggest excess rotor loss; relatively few grains near the<br />
front o f die grate area suggests a reserve o f separating capacity. This diagnosis can be<br />
used to check proper flow or evenness across walkers, grain pan, chaffer sieve, grain<br />
front, feeder house, <strong>and</strong> elevators. If the rotor is choked on restarting, appropriate<br />
unplugging procedures are needed to clear the machine.<br />
Unplugging<br />
If a heavy slug o f crop cannot be cleared from the cylinder/rotor under norm al operation<br />
(e.g., by slowing forward m otion), a stepwise procedure is needed to unplug the<br />
processing elements. If the cylinder/rotor is already plugged, first open the concave or<br />
lower the grates fully <strong>and</strong> run the separator to clear the cylinder/rotor. If that does riot<br />
work, the following procedure is needed. Caution; Raise the feeder, lower the safety<br />
stop, shut the engine off, <strong>and</strong> remove the key.<br />
1. Leaving the concave firily open, remove all straw <strong>and</strong> other material from the<br />
front o f the concave via the access opening.<br />
2. Remove the cylinder/rotor drive cover shield.<br />
3. Insert a breaker bar or rotor rocking wrench to move the cylinder/rotor back<br />
<strong>and</strong> forth.<br />
4. If this does not provide enough clearance, in the extreme case some o f the<br />
concaves/grates may have to be taken out to remove the plugged material<br />
5. After clearing the material, remove the breaker bar, replace the shields, readjust<br />
the concave to the <strong>origin</strong>al position, <strong>and</strong> reset the rotor gearbox <strong>and</strong> speed<br />
setting. Combines with a reversible feeder <strong>and</strong> rotor drive are far easier to<br />
unplug.<br />
RICE COMBINES IN ASIA<br />
In Japan, compact combines have proliferated, even though average farm size is under<br />
2 ha. They may he compact combines, but there is one on almost every farm. The<br />
trend is being followed by Taiwan <strong>and</strong> South Korea, each countries where industrial<br />
growth has taken labor away from agriculture <strong>and</strong> rice prices are kept high by government<br />
support. Combines have supplanted threshers <strong>and</strong> reapers (Figure 4.1.18).<br />
M ost compact combines are head-feeding self-propelled units developed specifically<br />
for rice (Figure 4.1.19). They are unsuited to other crops. Several Japanese makers are<br />
now producing a few rotary combines with multicrop capability. The world’s cheapest<br />
combine (relative to machine weight) is probably the Beijing Combine Harvester<br />
General Works’ combine. In 1995, the 90-hp diesel-powered Model 4L 2-3 with a<br />
3-m front, could be procured from the factory for just $8700. The m ost popular<br />
Chinese combines are tractor wraparounds, rice-w heat machines mounted onto lo <br />
cally available tractors (Figure 4.1.20). There are several Chinese manufacturers o f<br />
L
Ríce Harvesting 519<br />
6 0 54 5 8 62 66 70 74 78 82 86 90 94 98<br />
YEAR<br />
Figure 4.1.18. Japanese harvest machinery market. Note the decline in thresher <strong>and</strong><br />
reaper sales <strong>and</strong> the emergence of the Japanese combine business. (Data plotted by the<br />
author from FMIRC data tables, Tokyo,)<br />
li<strong>and</strong>-tractor-raounted combines (which have no equivalent in the Western world).<br />
These are usually o f the head-feed type (Figure 4.1.21), Some European combine<br />
models are produced in China in joint-venture operations, <strong>and</strong> there are some other<br />
modified “Western-style” machines. In Malaysia, harvest contractors <strong>and</strong> repair shops<br />
have been acquiring secondh<strong>and</strong> European-built combines, then repairing them for<br />
a second life on local rice fields. A roadside com bine restorer in Malaysia could fully<br />
recondition a machine <strong>and</strong> sell it for one-third o f the new price. In Thail<strong>and</strong>, on the<br />
otlier h<strong>and</strong>, a score o f manufacturers have been building <strong>and</strong> selling 3-m com bines<br />
with Western-style headers <strong>and</strong> an axial-flow thresher on top o f a crawler-tracked<br />
undercarriage (Figure 4,1.22). These are equipped with 120- to 175-hp engines driven<br />
through mechanical or hydrostatic transmission options. Some contractors built their<br />
own <strong>and</strong> charge between 8 <strong>and</strong> 14% o f paddy value, depending on the proximity of<br />
the field <strong>and</strong> crop conditions. Flotation is aided by 3.7-ra-wide wooden grousers fitted<br />
to the track plates o f D2 Caterpillar tracks in the undercarriage. There are problems<br />
with tlie first crop in central Thail<strong>and</strong>, with its very long straw. Fields that are small<br />
or beyond road access becom e inaccessible to this com bine. The machines are slow<br />
<strong>and</strong> cumbersome, but the labor shortage became so acute in the last decade that the<br />
Thai rice industry in central Thail<strong>and</strong> has become dependent on the combines. A crew<br />
o f four accompanies the machine <strong>and</strong> the paddy is unloaded by sack. Unless small-<br />
area farmers can reduce their harvest costs, they will be unable to compete <strong>and</strong> may<br />
be forced out o f farming, which increases the m igration o f rural workers. Contract<br />
harvestmg is a solution. The small-scale, 0.8-m -w ide stripper-gatherer developed at<br />
the International <strong>Rice</strong> Research Institute was designed as a machine that can be h<strong>and</strong>-<br />
carried into small fields. This design is being manufactured in several Asian countries,<br />
but it needs a separate power thresher (Quick <strong>and</strong> Douthwaite, 1994). Figure 4.1.23<br />
from IRRI literature shows the concept, while Figure 4.1.24 shows an S G 8 0 0 in use<br />
in China.
520 Products <strong>and</strong> Product Protessing<br />
Figure 4.1.19. In 1998, Yanmar Japan had as many as 19 different models in their rice combine harvesting lineup. The model<br />
shown is a two-row head-feed type; the straw is kept largely intact, inset shows the crop feed path <strong>and</strong> wire-loop threshing cylinders.<br />
{From Yanmar trade literature.)<br />
POWER THRESHERS<br />
Power threshers plg.yed an im portant role as the forerunners o f farm mechanization<br />
in the Western world. The same was true o f Japan (Figure 4.1.18) <strong>and</strong> is proving to<br />
be the case yet again in nations o f the developing world. Elsewhere in Asia, Westernstyle<br />
<strong>and</strong> even modern small Japanese combine harvesters have been shunned by lowincome<br />
farmers because of cost, often those with fields that are inaccessible for selfdriven<br />
equipment. H<strong>and</strong> threshing is arguably the m ost tedious <strong>and</strong> least attractive<br />
field activity. Rising labor costs <strong>and</strong> labor scarcities for harvesting have hastened the<br />
development of a wide range o f power thresher designs across the rice world in the<br />
last 40 years.<br />
Threshing machines or power threshers have enjoyed an illustrious <strong>history</strong>. In<br />
the industrialized world they are completely outdated, but in their heyday they were<br />
as im portant as they were large. Antique threshers can still be seen at shows. They are
<strong>Rice</strong> Harvesting 521<br />
.......■<br />
Figure 4.1.20. Chinese tracior-mounied combine operating near Hangzhou, with axial-flow threshing rotor on rear<br />
linkage. (Photo by G. I Quick.)<br />
Figure 4.1.2]. Two-wheel walk-behind tractor-mounted minlcombine with Fufian Province, China, The vertical<br />
reaper/4iead thresher combination is mounted on a Dong Fang two-wheel tractor, (From trade literature.)<br />
an impressive sight, especially when connected by an enormous belt drive to a steam<br />
traction engine. But they are no more than nostalgic museum or showtime pieces<br />
today. By contrast, in developing countries, there are places where threshing is still<br />
done using muscle power. H<strong>and</strong> or foot treading, either human or animal, or manual<br />
bundle-beating still goes on. That type o f work necessitates weeks, even months, to get<br />
through the harvest. Big Western-style threshers were tried in some developing countries,<br />
but they were just too costly, too heavy, <strong>and</strong> ill-suited for small or inaccessible<br />
fields. It was only after the 1950s that Tapan, South Korea, Taiwan, China, <strong>and</strong> other
522 Products <strong>and</strong> Product Processing<br />
Figure 4.1.22. Thai combine produced by Kaset Patana: 3-m gathering head, machine built on top of a<br />
Caterpillor D2 undercarrioge. (From trade literature.)<br />
Asian countries began to adopt small power threshers. This came about with rising<br />
labor costs <strong>and</strong> harvest labor shortfalls that intensified with rapid industrial growth<br />
during reconstruction after World War II. In Japan, threshers progressed from h<strong>and</strong>feed<br />
to mechanical head-feed, <strong>and</strong> from stationary to self-mobile machines.<br />
Chinese Threshers<br />
China, with two-thirds rural population, is the world^s largest rice producer, making<br />
up a third o f the world’s total. Foot-treadle-operated threshers are still to be found in<br />
China, but electric m otor-driven models of the same type (i.e., hold-on thresher with<br />
wire loop cylinder) are widely used. The Chinese have introduced rural electrification<br />
to an extent unprecedented in <strong>history</strong>. In remote fields far from any buildings, it is<br />
not uncom m on to see a thresher brigade man-h<strong>and</strong>ling their sled-mounted thresher<br />
with its electric motor over to a power pole socket connected to an overhead power<br />
line (Figure 4.1.25). M any thresher designs have been manufactured in China, such as<br />
conical throw-in threshers, twin-drum through-flow types, <strong>and</strong> vertical-shaft as well<br />
as horizontal axial-flow <strong>and</strong> fan-type power threshers. The main factor holding back<br />
axial-flow designs has probably been the Chinese farmers’ diligence in making use o f<br />
the whole crop, in which case they did not want to bréale up the rice sfiaw. The more<br />
recently developed axial-flow <strong>and</strong> rotary thresher designs do not leave the straw intact.<br />
Other Asian Threshers<br />
In some low-income parts o f Asian nations, labor costs are cheap enough that the use<br />
o f the sickle <strong>and</strong> manual threshing still predominates. However, the expectations o f
<strong>Rice</strong> Harvesting 523<br />
Figure 4.1.23. SG800 slripper-gafherer developed by IRRI in the Philippines for smell-area rice forms. The<br />
walk-behind self-propelling horvester weighs just 240 kg <strong>and</strong> is propelled with 11 -hp air-cooled engine. It can<br />
harvest ] ha/day with a team of seven <strong>and</strong>o thresher. Inset shows the rig set up to tow the thresher on a trailer,<br />
(Courtesy of the International <strong>Rice</strong> Research Institute.)<br />
young people are such that they do not want to follow the the family tradition <strong>and</strong><br />
there can often be a shortage o f willing h<strong>and</strong>s to harvest manually. The power thresher<br />
is the necessary first step to enhance labor productivity <strong>and</strong> reduce drudgery; this<br />
might be called labor-intensive mechanization. In the Philippines, for example, 57%<br />
o f the people are involved in farm ing <strong>and</strong> rice is the m ajor commodity. Ninety percent<br />
o f the rice crop is threshed mechanically in that country using power threshers.<br />
There are only a h<strong>and</strong>ful o f com bine harvesters. The recent development at IR R I of<br />
small, pedestrian-controlled stripper harvesters has raised the level o f interest in this<br />
approach to the rice harvest, with six manufacturers each turning out a small number<br />
o f these stripper-gatherers to test the market (Figure 4.1.23). However, IR R fs SG800<br />
stripper still requires a stationary power thresher.<br />
IRRI Axial-Flow Thresher Developments<br />
A comprehensive USAID research project funded between 1965 <strong>and</strong> 1973 precipitated<br />
the successful redevelopment <strong>and</strong> commercialization o f axial-flow threshers at IRRI<br />
witli designs that were com pact, elegantly simple, <strong>and</strong> intended for small-area farming<br />
in Asia (Figure 4.1.26). The project placed emphasis on the need for equipment<br />
designs that could be manufactured in-country. Outreach engineers on the project<br />
sought to popularize the design <strong>and</strong> had some impact in Indonesia <strong>and</strong> India. But in<br />
the Philippines <strong>and</strong> Thail<strong>and</strong>, particularly, the adoption rate o f the axial-flow thresher<br />
was rapid <strong>and</strong> extensive. In 1975, Thai manufacturers took the concept from trailerm<br />
ounted models through to power-hungry truck-m ounted models, with engines up
524 Products <strong>and</strong> Product Processing<br />
Figure 4.1.24. SG800 stripper harvester in operation near the China National <strong>Rice</strong> Research Institute, Hangzhou.<br />
(Photo by G. R, Quick.)<br />
Figure 4.1,25. Electric thresher; q sled-mounted power thresher driven by an electric motor, It was towed into the rice<br />
field by buffalo. Rural electrification is extensive in Chino, with power poles often in rice fields. (Photo by G. R. Quick.)<br />
to 100 kW, complete with power feeders <strong>and</strong> sacking elevators. In the Philippines,<br />
numerous manufacturers fabricated smaller models that could be manh<strong>and</strong>led into<br />
remote fields on bam boo poles, <strong>and</strong> they also made compact trailer-mounted models<br />
with full cleaning systems.<br />
IRRI engineers continued research <strong>and</strong> prom otional efforts on axial-flow thresher<br />
developments. A German GTZ project studied crop movement around the thresher
<strong>Rice</strong> Harvesting 525<br />
■Í<br />
Figure 4.1.26. Axial-flow <strong>and</strong> rotary thresfiers have been around for over two centuries, but what the IRRI team was<br />
able to achieve in some developing countries was to popularize an axial design that was well matched to small-area<br />
farming conditions <strong>and</strong> that could be fabricated locally at modest cost. This is a portable unit at work in a Sri Lankan<br />
rice field. (Photo by G. R. Quick.)<br />
rotor by means of magnets <strong>and</strong> induction sensors. The straw may trayel from 4 to 11<br />
times around the rotor (Gum m ert et al., 1992). Considerations o f straw flow led to<br />
a Vietnamese design which utilizes fewer teeth <strong>and</strong> can thresh rice bundles that are<br />
dripping wet from flooded fields. By 1990, government people estimated that there<br />
were 1000 thresher manufacturers in the Mekong Delta o f Vietnam alone <strong>and</strong> that<br />
they had built over 50,000 units. Following the popularization o f power threshers<br />
in the Mekong, Vietnam joined the top three rice-exporting nations, with m ost o f<br />
Vietnam’s export grain com ing from the Mekong Delta (Hien, 1991) (Figure 4.1.27).<br />
Ú<br />
Throw-in Threshers That Chop the Straw for Stockfeed<br />
M any farmers in South Asia want cereal straw— wheat straw in particular— ^to be<br />
chopped up fine for use as animal feed. In some seasons, chopped wheat straw has<br />
almost as much value as the grain. Indian threshers achieve a simultaneous threshing<br />
<strong>and</strong> straw-chopping action: All o f the crop material is forced through the concave<br />
<strong>and</strong> the rotor is equipped with chopping blades similar to those on a hamm er mill.<br />
Often, a fan is mounted integrally on the rotor axle to provide the air blast for the<br />
cleaning system underneath the concave, along with heavy flywheels to maintain the<br />
m om entum required for chopping.<br />
Where wheat <strong>and</strong> paddy are grown in rotation, such as in Egypt, parts o f China,<br />
<strong>and</strong> in India, farmers need threshers capable o f use in either crop with a minim um<br />
o f modification (Figure 4.1.28). An adapted thresher with a set o f adjustable louvers<br />
inside the cover o f the thresher drum can be fixed at 90“ to the rotor axis <strong>and</strong> the<br />
straw outlet blanked out for tlireshing wheat in the beater mode. W ith this A.U. Khan<br />
design, for threshing paddy the louvers are set at 75° to the rotor axis <strong>and</strong> the straw<br />
outlet door opened for separated straw discharge (Quick, 1998b).
526 Products <strong>and</strong> Product Processinn<br />
(ft)<br />
m<br />
i*<br />
(6)<br />
Figure 4.1.27. ‘irailer-mounted power threshers ore the most popular style of thresher in Vietnam. Some are<br />
mounted on a self-driven chassis <strong>and</strong> powered by o locally made 15-hp water-cooled diesel. These units have a capacity<br />
of up to 2 m1/h of cleaned paddy, (o) Author with a thresher on a barge in a canal on the Mekong Delta near Cantho.<br />
(6) On l<strong>and</strong>, the thresher is driven down the road to each of the individual farmer's piles of rice bundles stacked there<br />
wet <strong>and</strong> ready for threshing, The road is also used as a poddy-drying surface.when the sun shines. (Photo by G. R.<br />
Quick.)
¡<br />
<strong>Rice</strong> Harvesting 527<br />
Figure 4,1.28. Threshing in Egypt with a locally made troiler-mounted tractor belt-driven axial-flow thresher<br />
with adjustable guide vanes; the angles are set appropriately for paddy or for wheat. Wheat straw is smashed by<br />
the thresher for stock feed. (Photo by A. U. Khan; courtesy of the International <strong>Rice</strong> Research Institute.)<br />
Quantitative Assessment of Power Threshers<br />
Inform ation from commercial sources in 11 countries across the rice world was an-<br />
alyzed to calculate power versus throughput <strong>and</strong> in the case o f axial-flow threshers,<br />
throughput versus rotor width. Least-squares regressions on the data indicated that<br />
for this group o f machines as a whole, specific power (i.e., power requirement per<br />
unit o f throughput, measured by slope o f the regression line for the data set) was<br />
6.125 kWh/mt of rough rice grain throughput. For the axial-flow thresher data subset<br />
only, tlie slope coefficient o f the trendline for throughput versus rotor size was 4.79<br />
mt/h per meter o f rotor length. Head-feed threshers were found to require only half<br />
the power o f the other types as a whole. This type o f compact power thresher was not<br />
intended for capacities much above 1 mt/h because the feed tray is usually loaded by<br />
h<strong>and</strong>, which restricts the feed rate.<br />
Capacities above 2 mt/h o f grain throughput for throw-in or whole-crop power<br />
threshers are possible in rice with a power-feed mechanism. Power feeders enhance<br />
safety. Unless the feed apron is of sufficient length, there is always a risk o f the operator<br />
getting a h<strong>and</strong> or arm pulled into the drum or rotor o f manually fed power threshers.<br />
Indian milling-type threshers, which malee Bhusa, are the m ost hazardous in that<br />
regard <strong>and</strong> Indian st<strong>and</strong>ards have been established recently to try to minimize injuries<br />
to operators feeding the thresher.<br />
There are stiU huge numbers o f power threshers made in Asia. In China, for<br />
example, a 1992 estimate was that there were 5.9 million threshers on farms <strong>and</strong><br />
200,000 were produced that year (over 16 times the annual combine <strong>production</strong>).<br />
In India the estimate was 2.2 million on farms <strong>and</strong> an annual <strong>production</strong> o f around
528 Products <strong>and</strong> Product Processing<br />
60,000; while for Japan the peale number of power threshers was 3.3 million in 1967<br />
<strong>and</strong> <strong>production</strong> peaked the year after at 372,263 units. In 1996, annual <strong>production</strong><br />
of Japanese power threshers was 12,400, or less than one-fifth o f the shipment of<br />
combines that year. The average contract charge rate for use o f a power thresher has<br />
been about 4 or 5% o f paddy value on-farm for the Asian countries surveyed.<br />
TRACTION AND FLOTATION ASSISTANCE FOR EQUIPMENT IN RICE FIELDS<br />
I<br />
A power thresher might be manh<strong>and</strong>led into a paddy field; by contrast, the heaviest<br />
class 7 Western-style combine can weigh 28 m t with a full grain bin, A fuUy loaded<br />
<strong>and</strong> bogged combine harvester in a paddy field is neither an elegant sight nor easy<br />
to extricate. Expensive combines have been pulled in half under these conditions, or<br />
at least the rear axle torn away from the frame. Then there is the task o f tidying up<br />
the deep furrows left by the harvest machines <strong>and</strong> grain transporters, A level ground<br />
surface is essential to minimize water loss from flooded paddy fields.<br />
Forestry logger tires are an option on combines for rice fields to reduce rutting;<br />
these are tires With generous vridth <strong>and</strong> low inflation pressures (e.g., 35,5 to 32 tires<br />
on the drive axle of class 6 or 7 combines to reduce ground pressure). Steel full-track<br />
undercarriages <strong>and</strong> half-tracks with rear-steering axle have been options for com <br />
bines for years. More recently, prospective combine buyers have the choice o f rubber<br />
tracks, such as Caterpillar’s M obilTrac full rubber track/friction-driven system, Deere<br />
Sc Co. was the first fuU-liner to offer auxiliary rear wheel assist on combines, with a<br />
hydrostatic system patented in 1973. Deere’s auxiliary com bine drive was plumbed in<br />
such a way that the torque applied to the individual hydraulic wheel m otors in the<br />
rear wheels was proportionate to the torque applied to the m ain drivewheels, yet if<br />
spin-out occurred at the rear, the mainwheels would not lose power. Most contract<br />
harvesters purchase their combines with rear-wheel assist as st<strong>and</strong>ard, <strong>and</strong> several<br />
systems are available on the aftermarket.<br />
Each o f these <strong>and</strong> other traction alternates are options for reducing the soil<br />
damage caused by heavy combines in wet fields, <strong>and</strong> reducing the high costs o f l<strong>and</strong><br />
preparation <strong>and</strong> leveling after fields have been compacted by the combine undercarriage.<br />
The small-area com bine harvesters made in Japan, Korea, <strong>and</strong> Taiwan are<br />
usually full-track equipped, but those tracks are flexible <strong>and</strong> best suited to relatively<br />
firm or well-managed rice field conditions at harvest tim e in those countries.<br />
There is management skill in choosing the right time to drain the fields: Too<br />
early <strong>and</strong> tlie grain will be more prone to sun-checking in hot weather; too late,<br />
<strong>and</strong> combine traction/floatation or field bin transport <strong>and</strong> traffic problems wiU be<br />
exacerbated.<br />
MEASURING AND REDUCING RICE HARVEST LOSSES<br />
Taking the trouble to measure harvest losses may be worth $50 per hectare extra<br />
in the rice grower’s pocket. That’s the value o f grain losses if they are detected <strong>and</strong><br />
minimized. Modern com bine harvesters are equipped with loss monitors, but even<br />
the m ost sophisticated electronic loss monitors need to be calibrated periodically. To<br />
do that there is a need to get out <strong>and</strong> physically count grains on the ground. The
Ríce Harvesting 529<br />
operator has to decide what loss level to accept under given field conditions <strong>and</strong> the<br />
tim e available for harvest He or she then adjusts the com bine settings <strong>and</strong> travel speed<br />
accordingly.<br />
The three m ain categories o f losses are preharvest, harvest, <strong>and</strong> postharvest.<br />
Postharvest loss criteria relate to how safe the crop is to store <strong>and</strong> is independent o f<br />
field losses. Total field loss is the sum o f preharvest loss plus machine loss. Preharvest<br />
loss is present before the crop is harvested <strong>and</strong> is due to norm al m aturation processes,<br />
or weather, disease, <strong>and</strong> pest attacks. This loss is generally nonrecoverable by machine<br />
<strong>and</strong> may also be labeled as nonmachine loss or simply, crop field loss.<br />
Spot-Checking <strong>and</strong> Sampling Losses<br />
Crop loss due to the com bine can be assessed with a loss-measuring fi"ame (Table 4.1.2<br />
<strong>and</strong> Figure 4.1.29). For sampling, a frame o f dimensions 31.6 cm square or 35.7 cm<br />
inside diameter (both equal to ^ m^) is placed r<strong>and</strong>omly on the ground within the<br />
crop. Seventeen to 24 rice grains on the ground in the frame size is equal to a 50-kg/ha<br />
loss (or 1 bushel per acre within a 1-ft^ fram e). The precise figure for the num ber o f<br />
grains depends upon seed weight; a notional example would be 24 g per 1000 grains<br />
o f paddy. At least five <strong>and</strong> preferably 10 samples should be taken to average out field<br />
<strong>and</strong> otlier variability with this small frame size.<br />
W hen measuring machine loss o f a com bine or self-propelling harvester, first<br />
note that it is im portant to locate exact loss causes before any adjustments are made<br />
to the machine. Machine losses are made up o f the sura o f gathering or header front<br />
loss <strong>and</strong> body or processing separator loss. The com bine should be driven at regular<br />
speed with the straw or chaff spreaders disengaged, then stopped in an area o f tlie<br />
field that represents average field conditions. This excludes the edges o f the field or<br />
the end o f a run. W lien tlie com bine has cleared after stopping, it should be backed<br />
up a distance equal to one com bine length. All losses can be checked there without<br />
starting <strong>and</strong> stopping again in tliat area, as in Figure 4.1.29. For safety, the machine<br />
must be shut down completely before starting loss evaluations.<br />
Gathering loss is caused by cutting too high, reel shatter, excess stripping rotor<br />
speed, <strong>and</strong> so on. To calculate gathering loss, loss in area 1 (preharvest) is subtracted<br />
from loss measured in area 2. Processing loss is made up o f threshing plus separator<br />
plus cleaning shoe plus body leakage loss, <strong>and</strong> is measured in area 3, in <strong>and</strong> under<br />
the swath directly behind the separator. Note that grains are concentrated into this<br />
area by the com bine, <strong>and</strong> a multiplier must be applied to these figures to account<br />
for the concentration o f the crop being brought in from the full gathering widtli to<br />
TABLE 4.K2.<br />
Grain Weight <strong>and</strong> Seeds in a Loss-Measuring Frame: Rough <strong>Rice</strong><br />
Seeds in ^<br />
100 0-G rain<br />
Seeds/kg<br />
Pounds/Bushel<br />
M e asu rin g<br />
G rain Type<br />
W eight (g)<br />
(M e d ia n )<br />
(U.S.)<br />
kg/m='<br />
Fram e (50 kg/ha)<br />
Long grain 2 1 -2 4 4 4 6 4 3 4 2 -4 5 5 4 0 -5 8 0 2 1 -2 4<br />
M edium grain 2 3 -2 7 4 1 7 4 0 44^47 5 7 0 -6 0 0 2 0 -2 2<br />
Short grain 2 6 -3 0 35 898 4 5 -4 8 5 8 0 -6 2 0 1 7 -1 9
530 Products <strong>and</strong> Product Processing<br />
Figure 4.1.29. Combin3 loss measuremant. When checking losses in the crop, the machine is backed up by one<br />
combine length. PrehorvesT loss is counted in frames dropped in area 1; gathering loss is measured in orea 2 <strong>and</strong><br />
calculated by subtraction. Processing loss Is measured In area 3, in <strong>and</strong> under the swath directly behind the separator.<br />
It is made up of threshing plus separator plus cleaning shoe, plus body leakoge loss, after losses 1 <strong>and</strong> 2 have been<br />
subtracted.<br />
body width. Preharvest loss (area 1) <strong>and</strong> gathering losses (area 2) m ust be subtracted<br />
from loss in area 3 to calculate separating loss. Alternatively, a suitably made halfwidth<br />
gathering loss frame may be used in area 3. Take the material concentration<br />
factor into account. Best com bine operation is a compromise between forward speed,<br />
gathering height, <strong>and</strong> threshing settings under the prevailing conditions to get the<br />
crop in with a minimum o f delay, yet at an acceptable level o f losses (i,e., a balance<br />
between processing losses <strong>and</strong> delay losses). To be meaningful, any statement about<br />
combine grain throughput needs to be accompanied by the relevant loss level.<br />
Acceptable Loss Level<br />
ANSI/ASAE St<strong>and</strong>ard S343.3 states that a machine loss level o f 3% is acceptable in<br />
rice under good, crop <strong>and</strong> machine conditions at the maxim um sustained feed rate for<br />
combine (ASAE, 2000). This figure does not include gathering head losses. Notionally,<br />
these should be practically nil for a cutterbar <strong>and</strong>, say, 1% for a stripperhead in good<br />
upright crop conditions.<br />
Combine Loss Monitors<br />
Loss monitors do not measure actual loss quantitatively but provide a guideline or<br />
indicator to the driver based on measured electronic signals from devices in the body<br />
that provide a relative number (such as number o f seeds striking sounding boards in<br />
a given time) or an analog needle position, Periodic field checks are necessary for the<br />
readouts to have any bearing on machine performance under given conditions. This<br />
field check is a form o f calibration so tliat losses are rougMy proportional to the signal<br />
on the readout in the cab. Forward speed <strong>and</strong> thresher settings can be fine-tuned to<br />
local conditions using the m onitor to avoid excessive losses. W lien the operator has<br />
adjusted the combine <strong>and</strong> header to an acceptable loss level, the m onitor can be set to
Rite HarvGsting 531<br />
this level, thereafter indicating whether to increase or decrease ground speed. Another<br />
im portant use for grain loss monitors is to indicate if some processing component<br />
has stalled (e.g., thrown drivebelt) or is slowing or becoming plugged, as in the case<br />
of overloaded straw walkers, plugged sieves, or a stalled tailings return elevator.<br />
Loss monitors perform best in uniform conditions <strong>and</strong> when the combine is<br />
being operated somewhere near its maxim um throughput. Losses occur either side o f<br />
the optim um throughput. In damp, difficult, or changeable conditions, the readings<br />
can be erratic <strong>and</strong> misleading; under those circumstances it is best to switch off the<br />
monitor. Economics o f losses can be calculated from actual loss numbers (estimated<br />
average kg/ha) multiplied by area harvested (ha) times the crop value (dollars per kilogram<br />
farmgate price). A good manager would balance off econom ic losses incurred<br />
by pushing the machine harder compared with the productivity gains from getting<br />
the jo b done faster or before inclement weather reduces crop returns.<br />
Harvest Delays<br />
Timely harvest minimizes losses. The world’s highest-elevation rice crops are grown<br />
in Bhutan. <strong>Rice</strong> is grown at over 3000 m altitude. Harvest delays at those altitudes<br />
can result in shattering levels up to 50% before the crop is gathered. Harvest delays<br />
will reduce grain yield, exacerbate harvest losses, lower grain weight, raise trash levels,<br />
reduced whole grain, adversely affect quality <strong>and</strong> lower premiums, <strong>and</strong> increase<br />
shattering <strong>and</strong> lodging; see, for example, the Arkansas rice data in Figure 4.1.30.<br />
HARVEST AND GRAIN QUALITY<br />
Holding freshly harvested paddy in bulk quantities for m ore than a day in highhumidity<br />
conditions, such as in the humid tropics, greatly reduces its value. Paddy<br />
matures at a high moisture level (20 to 27% ). It will dry down if left st<strong>and</strong>ing, but then<br />
head shatter, pests, <strong>and</strong> weathering take their toll. High-moisture paddy is vulnerable<br />
Figure 4.1.30. Timeliness effecls in Arkansos rice: field yield reduction with<br />
time for the cultivars Lebonnet <strong>and</strong> Lobelie. Overall average slope is 0.66% loss of<br />
paddy yield per day. {From Lu et al., 1992.)
532 Products <strong>and</strong> Product Processing<br />
to rapid deterioration, <strong>and</strong> if quality is to be maintained, it needs immediate action to<br />
control grain moisture <strong>and</strong> temperature. The safe moisture level for storage depends<br />
on grain condition <strong>and</strong> cultivar, the storage environment, <strong>and</strong> climate. Paddy can be<br />
stored safely up to 2 or 3 m onths at 12 to 13% moisture content (M C ). For very longterm<br />
storage, die grain should be dried below 12.5% . Whatever the case, paddy must<br />
be dried; it can’t be left long in the field <strong>and</strong> it can’t be kept wet. This hygroscopic<br />
com modity must be managed carefully if it is to retain value. <strong>Rice</strong> grains are hygroscopic<br />
<strong>and</strong> will gain or lose moisture to equilibrate with ambient air. Atmospheric<br />
humidity <strong>and</strong> temperature govern the equilibrium moisture level o f paddy. Under<br />
the conditions found in the humid tropics; for example at 85% relative humidity <strong>and</strong><br />
30°C, the equilibrium M C o f paddy is around 16% (refer to ASAE St<strong>and</strong>ard D 245.5;<br />
see also Wimberly, 1993).<br />
St<strong>and</strong>ards for <strong>Rice</strong> Quality<br />
Because rice is required as whole grain (unlike some other cereals) <strong>and</strong> the harvest<br />
has a m ajor effect on whole-grain quality when rice is dried <strong>and</strong> milled, the impact<br />
o f harvest on postliarvest processes needs to be examined. Underscoring this is the<br />
need for quantifiable methods o f measuring rice quality. Quality criteria for price<br />
<strong>and</strong> market quality of milled rice are not related to criteria for cooking <strong>and</strong> eating<br />
quality or for nutritional quality of the cooked rice. The issue is complicated by the fact<br />
that freshly harvested rice undergoes textural changes during the first tliree months<br />
after harvest; thus milling tests <strong>and</strong> tests for cooked rice are preferably done on aged<br />
rice. <strong>Rice</strong> is in the first place categorized <strong>and</strong> marketed according to grain size <strong>and</strong><br />
shape (e.g., long, medium, <strong>and</strong> short). <strong>Rice</strong> grades are measured by proportion o f<br />
whole grains in the sample; freedom from foreign material (stones, dirt, plant parts,<br />
or trash <strong>and</strong> animal droppings), weed seeds, stackburn, <strong>and</strong> so on, <strong>and</strong> grain color.<br />
Grades are assigned to delivered rice according to how well the sample matches the<br />
st<strong>and</strong>ards.<br />
Grain Breakage in Postharvest Operations<br />
AU rice is predisposed to varying degrees o f cryptic damage (i.e., grain breakage<br />
that shows up after the crop comes in from the field). Harvest delays, generating<br />
wetting <strong>and</strong> drying cycles, exacerbate the problem. During drying, h<strong>and</strong>ling, <strong>and</strong> in<br />
the milling process, incipient failures occur due to hidden cracks in the rice kernels.<br />
Add to this the rough treatm ent in threshing or conveying, <strong>and</strong> the result is broken<br />
grain, dockage, <strong>and</strong> reduced premiums. Indicas, which have longer grains, are more<br />
inclined to harvest <strong>and</strong> milling brealcage than tlie more spherical japónicas.<br />
Effect of Harvest Delays<br />
Paddy deteriorates under the influence of diseases <strong>and</strong> microorganisms. <strong>Rice</strong> quality<br />
st<strong>and</strong>ards define the limits on the amount o f grain tliat is discolored, musty or sour.
<strong>Rice</strong> Harvesting 533<br />
<strong>and</strong> otherwise is of distinctly low quality. As the season draws on there is increased<br />
risk o f rain <strong>and</strong> a lower m illout (Figure 4.1.30). <strong>Rice</strong>-processing organizations assess<br />
dockage from laboratory sample analysis based on local criteria <strong>and</strong> recognized national<br />
st<strong>and</strong>ards. These include trash, stackburn, <strong>and</strong> foreign material. Paddy left too<br />
long in the field will be rewetted by rain, dew, or fog. Instore discoloration occurs due<br />
to heat damage from being held too long in unaerated containers, field bins, or bags.<br />
MANAGING FIELD OPERATIONS<br />
Two harvester performance criteria are combined to arrive at a specific haiwest cost<br />
(i.e., cost per tonne o f paddy). These are material processing performance <strong>and</strong> econom<br />
ic performance. There are used to calculate harvester performance in econom ic<br />
terms:<br />
unit harvest cost ($/mt) =<br />
econom ic performance ($/h)<br />
material processing performance (mt/h)<br />
Alternatively,<br />
total harvest cost, ($/yr)<br />
dollai‘s/mt —<br />
metric tons harvested/yr<br />
Material performance is measured by mt/h o f grain or crop throughput at an acceptable<br />
loss rate. For rice, ASAE's recognized st<strong>and</strong>ard is 3% total machine loss. See Figure<br />
4.1.31 for the typical shape o f a harvester performance curve. The point on the curve<br />
where the aggregate m achine losses exceed 3% is the cutoff for establishing the performance<br />
rating. The com bine m aybe operated at higher losses, but a good manager<br />
will clamp down on an operator to set the machine to get those losses down below<br />
the critical 3% line. That may require slowing down, readjusting m achine settings, or<br />
looking for a malfunction. In a rice field the m ost crucial factor governing processing<br />
losses is usually the am ount o f straw or M O G intake.<br />
Figure 4.1.31. Typical shape of a harvester performance curve. Three<br />
percent total mochine loss is the internationally recognized cutoff point<br />
for estahlishing the performance rating of qcombine in rice.
i<br />
534 Products <strong>and</strong> Product Processing<br />
Assessing Field Efficiencies<br />
Field efficiency Ef is the ratio o f the effective capacity o f a machine or machine system<br />
to its theoretical capacity. The field capacity o f a harvester is measured on an area basis<br />
in hectares per hour of productive time or on a throughput basis in mt/h, usually<br />
referring to m etric tons o f grain, but in some cases total material throughput may<br />
be o f interest. Throughput in m etric tons per hour o f the harvester also is equal to<br />
the field yield (mt/ha) x harvesting rate (ha/h). Effective field capacity is a measure<br />
o f actual sustained performance over a day or a season. By com paring that with the<br />
theoretical field capacity, the field efficiency reveals how far the operation falls from<br />
the ideal. Inefficiencies include the difficulty of continuous operation at spot rates<br />
or top performance, or o f keeping the gathering front full all the time or o f getting<br />
the grain out o f the field at a rate matching the harvester. It also focuses on timeconsuming<br />
<strong>and</strong> unproductive activities due to machine <strong>and</strong> management problems,<br />
weather, crop, operator tim e-out, <strong>and</strong> other factors (see Table 4.1.3). The following<br />
equations define the relationship among effective area capacity (C„), effective material<br />
capacity (C,„), <strong>and</strong> field efficiency (jE/):<br />
SwEf<br />
effective area capacity C„ (ha/h) ==<br />
where 5 is the forward speed (km/h), w is the machine working width (m ), <strong>and</strong> Ef is<br />
the field efficiency (decimal); <strong>and</strong><br />
effective material capacity C,„ (mt/h) = SwyEf .<br />
10<br />
where y is the field yield (mt/ha). Ef, the field, efficiency, is the ratio between the<br />
machine’s productivity under actual working conditions <strong>and</strong> the theoretical m aximum<br />
possible productivity. For a large modern self-propelled combine,<br />
is typically<br />
around 70% (Ef — 0.7 ), or for less-efficient equipment or worn-out combines, <strong>and</strong><br />
for threshers, ai'ound 60% (£/ = 0.6).<br />
Operating area per day A (ha/day) =<br />
CM<br />
where C„ is the area capacity (ha/h), h is the hours worked/day, <strong>and</strong> k is the time<br />
efficiency (% ).<br />
(D-R)<br />
Area per year A (ha) —<br />
N<br />
where D —R is days available per season minus days when operation is not possible<br />
(typically, 25) <strong>and</strong> N is the num ber o f repeated operations (usually 1.0 for combine<br />
harvesting).<br />
To select the machine capacity for a given area:<br />
required machine capacity C (ha/h) ==<br />
£G (p w d )<br />
where A is the area to be harvested (ha), B is the number o f days within which<br />
the harvest should be accomplished, G is the anticipated time in hour&>.available for
<strong>Rice</strong> Harvesting 535<br />
field work each day, <strong>and</strong> pwd is the decimal probability o f a full working day (Hunt,<br />
1995).<br />
A num ber o f if actors affect field efficiency <strong>and</strong> result in lost machine work time.<br />
These include:<br />
1. Travel to or between paddocks<br />
2. Servicing <strong>and</strong> fueling the harvester<br />
3. Type <strong>and</strong> condition o f com bine<br />
4. Field conditions, field shape, access, <strong>and</strong> size<br />
5. Crop yield <strong>and</strong> condition<br />
6. Operator skill, experience, <strong>and</strong> acuity<br />
7. M achine maneuverability<br />
8. Turning <strong>and</strong> field patterns<br />
9. Unused capacity<br />
10. Number o f combines in use<br />
11. Unloading procedures<br />
12. Unplugging the harvester<br />
13. Making adjustments<br />
14. Repairing breakdowns<br />
15. Rest breaks<br />
16. Changing operators<br />
17. Checking machine performance<br />
18. System limitations (e.g., unmatched machines, long haulage distances, receival<br />
depot delays, etc.)<br />
M ost lost-tim e factors can be reduced with advanced planning <strong>and</strong> management.<br />
The more expensive the harvester, the more expensive are any management errors <strong>and</strong><br />
the greater the savings by attention to detail. In rice fields, time lost out o f crop time<br />
in turning <strong>and</strong> maneuvering can be more than half o f total field time. This can be<br />
modified by planning field layout to shape the bays to better suit the harvester; for<br />
example, bay width should perm it a full com bine each run, <strong>and</strong> the bay length should<br />
allow the truck or bin to be placed at a location where the com bine bin wiU have been<br />
filled. Stopping to unload a class 6 com bine can am ount to m ore than 15% o f field<br />
time. Chaser bins eliminate the costs o f stopping to unload, but their costs need to be<br />
factored into the overall system.<br />
K e e p in g R ecord s<br />
Good managers keep a careful record o f a machine’s performance correlated with m a<br />
chine hours. There are considerable savings to be made by weighing each o f the factors<br />
listed above to obtain the highest possible field efficiency <strong>and</strong> system performance.<br />
M a c h in e S y stem s<br />
The harvest operation typically involves a system o f machines in which the field<br />
efficiency o f any one o f the machines may be the limiting factor on the capacity
536 Products <strong>and</strong> Produit Processing<br />
T A B LE 4.1.3.<br />
S o m e A c tu a l H a rv e ste r P e rfo rm a n c e D a t a in R ice '’<br />
System Performance Rating<br />
Parameter {Units]<br />
Low Average High<br />
Forward speed (km/h) 4 4 7<br />
Header width (m) 3.2 6 7.6<br />
Field efficiency (%) 30 60 80<br />
Material capacity (mt/h) 3.6 13.6 40<br />
Area capacity<br />
ha/h 0.38 1.44 4,26<br />
acres/h 0.95 3.6 10,65<br />
Notional unit costs ($/mt) 22 13 8<br />
"From tests in a 9,6-mt/h rice area; unit costs converted to U.S. doEars. Contract harvester<br />
rate in NSW was around $15/rat in 1998.<br />
o f the overall system. Suppose that tlie rice mill or receiving station has a h<strong>and</strong>ling<br />
capacity limited by the elevator pit at 80 rat o f wet grain an hour. Grain delivery<br />
trucks bringing in more than this wiU be delayed, <strong>and</strong> this has repercussions back to<br />
the transport wagons or chasers <strong>and</strong> even to combine operations in the field. That<br />
becomes highly relevant with combines capable of over 40 mt/h. A cycle diagram<br />
or flowchart helps to clarify a system’s performance evaluation. The longest cycle<br />
time in the system (be it the combines, transporters, or receiving station) governs<br />
the overall system cycle. Computer simulation models can be o f value in helping highcost<br />
practitioners to lower their unit costs compared with the more efficient operators<br />
(Staton et al., 1994).<br />
O p e n in g t h e F ield a n d Turning<br />
Turning time can be 50% or more o f total field time in rice bays, because rice bays are<br />
by definition smaller parcels o f l<strong>and</strong>. W hen bays are less than 1 ha, more than half the<br />
time can be absorbed in turns. Even on an extensive rice farm, the maxim um size o f<br />
a bay may be restricted to around 10 ha, due to the effects o f wind on the irrigation<br />
water in the bays. There are at least eight patterns to cut out a harvest field. Each<br />
has advantages <strong>and</strong> drawbacks. Field pattern efficiency (actual time taken to cover an<br />
area compared with theoretical field capacity) is a measure o f out-of-crop time <strong>and</strong> is<br />
affected by the driving pattern chosen <strong>and</strong> field size.<br />
U n lo a d in g<br />
Stopping to unload a class 6 com bine can consume up to 15% o f field time. Unloading<br />
on the run into the follow-up transporter (Icnown variously as chasers, grain wagons,<br />
carts, bankouts, or haulouts; some are self-propelled) eliminates that time wastage<br />
but requires coordination <strong>and</strong> preferably radio contact with the driver o f the chaser<br />
bin. If chaser bins are unavailable, there is a need to balance field size against yield so<br />
that, ideally, the harvester makes a whole number of rounds just as the b in js full when
<strong>Rice</strong> Harvesting 537<br />
arriving back at the starting or collection point. Irregularly shaped fields <strong>and</strong> small rice<br />
bays each pose their own challenges. Field efficiency in odd-shaped bays <strong>and</strong> around<br />
obstructions is considerably less than for clear rectangular parcels. As the com bine is<br />
not operated at optim um load all the time, losses increase, second-cutting o f stubble<br />
occurs, <strong>and</strong> trash levels in the bin increase if the header is not full. Operators usually<br />
figure out a strategy on the spot. The aim is to minimize out-of-crop tim e, maintain<br />
a fuU cut, <strong>and</strong> maximize uninterrupted length o f run.<br />
Cleaning the Equipment<br />
Combines <strong>and</strong> field equipment are vectors o f insects <strong>and</strong> weed seeds <strong>and</strong> cause cross-<br />
varietal contam ination if no attention is paid to this aspect o f crop management.<br />
Residues that build up in strategic places on the com bine, especially the engine com <br />
partment, are a cause o f fires as well. Combines are difficult to clean out between<br />
cultivars <strong>and</strong> crops. The Case <strong>and</strong> Deere machines are said to be the hardest to clean;<br />
Agco <strong>and</strong> New Holl<strong>and</strong> scored somewhat better in that regard (Kondinin, 1998). A<br />
superficial cleanout can be accomplished in around an hour by an operator with a<br />
compressed air lance, but it can take an entire day to get com bines almost totally free<br />
of residues <strong>and</strong> grain.<br />
Summary<br />
The harvest <strong>and</strong> transport com ponent can make up 40% o f a rice growers" field costs.<br />
There is considerable scope for making meaningful reductions in unit costs. On rice<br />
fields with bays small <strong>and</strong> maneuvering time large, harvest management <strong>and</strong> selection<br />
o f suitable field patterns assumes greater significance than with other cereals. Planning<br />
ahead <strong>and</strong> modeling the system are valuable to help lower costs.<br />
P R IV A T E O W N E R S H I P V E R S U S C O N T R A C T IN G<br />
Informed decisions on whether to buy new or used, to hire or lease harvest equipment,<br />
bring in a contractor, repair or replace, <strong>and</strong> indeed make any capital changes in<br />
the farm enterprise can only be made if good records or advice are available. Total<br />
machine costs are the sum o f two categories o f costs: ownership or fixed costs, which<br />
are largely independent o f hours on the machine, <strong>and</strong> operating or variable costs,<br />
which are directly related to hours o f use. The sum o f the two are collectively referred<br />
to as O&O costs.<br />
The effect o f the am ount o f use on costs is shown in Figure 4.1.32. For a fixed<br />
crop area, machmes with higher grain throughput performance will operate at a lower<br />
cost per m etric ton <strong>and</strong> per hectare, <strong>and</strong> the harvest will be completed in a shorter<br />
time. W ith a fixed area to haiwest, costs per hour o f operation can actually increase<br />
in some circumstances. That’s the situation if a combine is subsequently equipped<br />
with a capacity-enhancing stripperhead. The key to exploit such an attachment fully<br />
is to find more area to harvest, in order to spread the cost over a larger number o f<br />
hours <strong>and</strong> then capitalize on the extra performance. As an example, a $200,000 rice
538 Produtfs <strong>and</strong> Product Processing<br />
Figure 4.1.32. Calculated combine owing <strong>and</strong> operating costs compared with two contracting rates on<br />
Australian rice fields for a class 6 combine. M any formers prefer gouging performance in metric tons of<br />
grain per day or per season rather than on machine hours. (From'Quick et al., 1996.)<br />
:l<br />
com bine that is used for 400 hours o f harvest for a year will cost $125 to own <strong>and</strong><br />
operate, whereas if it is operated for only 150 hours a year, it will cost about $352 an<br />
hour to own <strong>and</strong> operate.<br />
A simplification for repair <strong>and</strong> maintenance costs is to assign a fixed percentage<br />
over the life of the machine. In actuality, .these costs change with time. Initial repairs<br />
may be done under warranty. A notional figure o f 40% o f list price to cover total repairs<br />
<strong>and</strong> maintenance m aybe close to the mark for combines. Accounting procedures<br />
for depreciation <strong>and</strong> interest charges will be dictated by prevailing taxation rules. A<br />
basic rating is<br />
<strong>origin</strong>al machine cost — resale value<br />
average annual depreciation —<br />
working life (years)<br />
The resale or remaining value for North American combines is calculable as a percentage<br />
of <strong>origin</strong>al list price at the end o f year n, as follows: RV = 64(0,885)" (ASAE,<br />
2000D 497.2).<br />
W hat is a working life? ASAE D 497.2 st<strong>and</strong>ard suggests 3000 hours as a typical<br />
working life for a self-propelled combine. Annual hours o f use will determine the<br />
econom ic working life. On the rice fields a privately owned com bine may run about<br />
300 engine hours a yeai*, less than half that o f a contractor. Separator hour meters,<br />
where used, will usually be lower than engine hours incidentally, due to time spent<br />
driving to the fields, <strong>and</strong> so on. There are vintage machinery shows or field days<br />
where some harvesters are 50 to 100 years old, still in a good state o f preservation <strong>and</strong><br />
operable. Combines will more often be phased out more because they are considered<br />
outdated <strong>technology</strong> rather than entirely due to wearout. There are successful businesses<br />
dealing in or restoring secondh<strong>and</strong> combines. In Malaysia, a high proportion<br />
o f that countries’ rice crop is harvested with old combines purchased from European<br />
dealerships <strong>and</strong> reconditioned by small roadside repair businesses. Some o f these<br />
machines are still useful after 30 years.<br />
-■‘i'
<strong>Rice</strong> Harvesting 539<br />
M a n a g in g v e rsu s Ju s t D rivin g M a c h in e ry<br />
ultimately, farm equipm ent purchase decisions are based on a farm’s cashflow situation<br />
<strong>and</strong> then on which br<strong>and</strong> o f machine will provide the most timely operation <strong>and</strong><br />
has tlie dealer service backup. A machine log on the number o f hours o f productive<br />
work in a given period o f operation is essential not only for m onitoring service work<br />
<strong>and</strong> costs, but it also adds value when produced at resale. A report on performance<br />
evaluations <strong>and</strong> surveys o f combine operators (Q uick et al, 1996) covered 20 different<br />
combinations o f harvesters <strong>and</strong> fronts tested at five sites. This revealed that while class<br />
6 <strong>and</strong> 7 combines were capable o f performances o f more than 35 m t o f grain an hour<br />
<strong>and</strong> spot rates o f more than 60 mt of grain an hour, seasonal usage by some com bine<br />
owners were as low as 6 m t an hour. Often, overall efficiency was barely 20% for the<br />
combine for the season (i.e., 80 % o f the time the machine was not in tlie crop <strong>and</strong> not<br />
being used productively). The same study showed that harvest costs ranged from over<br />
$70 per m etric ton o f grain harvested to below $7 per metric ton of grain. Farmers’<br />
unit harvest costs escalated when (1) the number of hours o f m achine use were low,<br />
(2) machine performance was inadequate, <strong>and</strong> (3) the operator did not utilize the<br />
full potential of m achine hours in actually harvesting the crop (e.g., not keeping the<br />
header full).<br />
C o n tra ct v e rsu s P riv a te O w n ersh ip fo r th e A u stra lia n Study<br />
Figure 4.1.32 shows how calculated ownership costs compare with contracting on rice<br />
fields. W ith tlie parameters chosen here for a class 6 com bine, a manager would need<br />
to have a harvest season o f around 2000 or 2700 m t, respectively, to be operating<br />
cheaper than the two contract rates quoted. M etric tons instead o f hours are used<br />
here for the lower axis, although some operators preferred to record the m etric tons<br />
o f grain through the machine in a day or a season rather than figure from the machine<br />
hour meter (engine or separator).<br />
M a c h in e L e a s in g v ersu s P u rch a sin g<br />
Leasing or renting equipment may be a way to reduce operating costs. Payments for<br />
renting or leasing may be fully deductible as a business expense. Renting is different<br />
from leasing, in that it may involve short periods o f tim e, whereas leasing is reserved<br />
for contracts that might be up to several years’ duration. A lease contract cannot be<br />
breached by either party without recovery o f damages but is more attractive to farmers<br />
who are claiming investment credit or considering machine purchase for a nom inal<br />
sum at the end o f the lease period.<br />
C o st R eco rd s<br />
Systematic managers m aintain machinery operational cost records to provide legitimate<br />
income tax deduction expenses, <strong>production</strong> cost data, <strong>and</strong> inform ation on<br />
which to base equipment replacement decisions. A rational basis for choice is needed
540 Products <strong>and</strong> Product ProcBssing<br />
when it comes to an investment in or replacement o f an item as enduring <strong>and</strong> expensive<br />
as a combine. There are five formal methods to compare among alternatives:<br />
payback period (PBP) <strong>and</strong> break-even point (BEP), which are undiscounted procedures,<br />
<strong>and</strong> the discounted procedures: benefit/cost ratio (BC R ), net present worth<br />
(N PW ), <strong>and</strong> return on investment (RO I) or internal rate o f return (IR R ). The choice<br />
among methods is a matter o f personal preference, corporate policy, or the individual<br />
tax situation.<br />
P riv a te O w n ersh ip v e rsu s th e O p tio n<br />
A fully equipped rice combme that costs $230,000 when financed over 5 years will<br />
require a total capital outlay o f $305,000, with a $60,000 deposit <strong>and</strong> five yearly payments<br />
o f $49,000. If the harvester does 1200 ha each year, <strong>and</strong> adding the variable costs<br />
o f around $19.50 per hectare, combine ownership would cost $70.30 per hectare, or<br />
if over tlie years the crops average 7.5 rat/ha, the harvest cost is $9.37 per tonne o f<br />
paddy. The official contract rate to Australian rice growers in the 1998 season was $15<br />
per m etric ton wet weight. The decision whether to hire a custom operator, buy, rent,<br />
or lease a harvester, or even to jo in a machinery ring or syndicate comes down to the<br />
individual situation <strong>and</strong> practical considerations, some o f which are not driven by<br />
econom ics. A complex o f factors are involved. Some o f these include:<br />
1. The costs of finance, which involve taxation considerations<br />
2. The timing <strong>and</strong> level o f cash payments in relation to the cashflow o f the<br />
farming enterprise<br />
3. The security dem<strong>and</strong>s o f the lender or lessor<br />
4. Availablity of contract harvesters when needed<br />
Summary<br />
The rice grower who decides to buy his or her own combine or transporters has to live<br />
with that decision for the next 5 to 15 years or even more. That is a much weightier<br />
matter than what seed or fertilizer to buy for the season. W hen seen in this light,<br />
the matter of advising farmers on machinery operation <strong>and</strong> purchasing is worthy of<br />
more consideration for research by institutions <strong>and</strong> extension agencies. Individual<br />
ownership or leasing requires the local sldlls to operate, service, <strong>and</strong> maintain the<br />
harvester. Machine leasing may be a good option for an exp<strong>and</strong>ing business short on<br />
capital but with good prospects <strong>and</strong> management skills. Leasing involves making a<br />
large initial payment, then a yearly rental for the use o f the machine. Leasing enables<br />
working capital to be put to other uses <strong>and</strong> usually involves a 3- to 5-year term. A<br />
secondary consideration in individual ownership or leasing is the availability o f secure<br />
storage <strong>and</strong> the availability of local dealership <strong>and</strong> parts services. M ost important,<br />
however, is the availability of enough work on the farm or in the district to extend<br />
machine hours for an economically feasible harvest business operation. Alternatively,<br />
if contracting is the consideration, are a contract operator <strong>and</strong> machine available<br />
on time? Is tlie custom operator available where needed <strong>and</strong> at a reasonable price?<br />
Tables 4.1.4 <strong>and</strong> 4.1.5 provide a cost comparison between Western <strong>and</strong> Asian rice<br />
harvesting equipment.
<strong>Rice</strong> Harvesting 541<br />
TABLE 4.1.4.<br />
W e ste rn vs. A s ia n C o m b in e C o p ifa l In v e stm e n t<br />
(C o m b in e C o st p e r M e t e r o f G a t h e r in g W id t h fo r S P R ice M a c h in e s )<br />
U.S. rice combines (typically) $20 000<br />
Japanese rice combines $40 000<br />
Thai 3-m rice combine $13 000<br />
Claas crop tiger $22000<br />
Chinese rice combine $4000<br />
Vietnamese tracked combine $2000<br />
T A B LE 4.1.5.<br />
T ypical B re a k -E v e n P o in t fo r C o m b in e O p e ra tio n<br />
(5 -Y e a r A m o rtiz a tio n ) v e r s u s A s ia n H a rv e st M e t h o d s (m t)<br />
U.S. rice combine<br />
Japanese rice combine<br />
Thai 3-m rice combine<br />
Power thresher in the Philippines<br />
2000<br />
1600<br />
425<br />
250<br />
C O N T R O L A N D I N F O R M A T IO N S Y S T E M S<br />
M odern combines are becom ing increasingly sophisticated field vehicles. Operator<br />
expectations may be forcing the trend. Combines can be fitted with control <strong>and</strong> information<br />
systems to reduce operator stress; acquire field data on crop yield, protein,<br />
<strong>and</strong> moisture; <strong>and</strong> improve harvest efficiency. The cabs on Western-style machines are<br />
designed ergonomically to facilitate the operator’s task o f managing the 40-1- signals<br />
that come in during the harvesting process. Joystick control levers, for example, are<br />
offered that integrate electrical over hydraulic or mechanical functions at a touch.<br />
Power steering, multilighting, <strong>and</strong> wraparound windows without corner posts all<br />
facilitate the driver’s task. M onitors <strong>and</strong> touch screens enable predetermined machine<br />
settings to be managed automatically on the go. Stored setting values can be upgraded<br />
by operator experience <strong>and</strong> data downloaded for analysis <strong>and</strong> mapping later. Warning<br />
devices signal tire operator when malfunctions occur, such as adverse engine conditions,<br />
processor slowing or overload, shaft stalls, bin full, <strong>and</strong> excess losses.<br />
M a n a g e m e n t D a ta<br />
W ith enhanced satellite GPS <strong>and</strong> an onboard yield monitor, field yield data can be<br />
continuously displayed, recorded, <strong>and</strong> subsequently plotted. Grain throughput, area<br />
covered, amount harvested per day, <strong>and</strong> yield in each bay are valuable management<br />
data provided by a yield m onitor on a combine. The data are available to the operator<br />
on the screen in the cab as well as accessible later through stored files for subsequent<br />
printout <strong>and</strong> diagnosis.<br />
C O N C L U S IO N S<br />
In industrialized nations, rice is com bine harvested. M ost o f the rice traded interna-<br />
tionally is harvested by com bine harvesters. These are machines modified or designed
542 Products <strong>and</strong> Product Processing<br />
specifically for paddy field conditions. The market is shared between walker <strong>and</strong> rotary<br />
designs, the walker machines usually being equipped with spilce-tooth cylinders<br />
for paddy. Stripperheads are an emerging force for gathering rice but are maldng little<br />
impact on other crops. The custom charge rate for com bining rice is 4 to 15% o f paddy<br />
price. Increasingly sophisticated inform ation systems on combines have reached tire<br />
stage in some areas where a contractor m ust provide the grower-customer with yield<br />
data as part o f the harvest contract. The world m arket for combines has diminished to<br />
one-fifth the number sold 20 years ago. The num ber o f farms has declined steadily <strong>and</strong><br />
combines are bigger, with far higher capacity than even a decade ago. <strong>Rice</strong> combine<br />
sales constitute around 4% o f the global combine market. Deere <strong>and</strong> Case have the<br />
m ajor slice o f the market for rice combines in North America, with both companies<br />
now offering walkerless designs equipped specifically for the rice crop.<br />
In many developing countries, local dem<strong>and</strong> for threshing equipm ent has encouraged<br />
unprecedented <strong>production</strong> of power threshers. The thresher has proven to<br />
be a precursor to mechanization <strong>and</strong> a much-needed machine that can launch indigenous<br />
manufacturing capabilities in low-income countries. Power threshers, bulk<br />
h<strong>and</strong>ling, mechanical drying, <strong>and</strong> aeration still have a long way to go, however, to<br />
reduce the significant loss o f paddy that occurs every season in the humid tropics.<br />
Whatever the <strong>technology</strong> or region, the harvest is either the most expensive field<br />
operation or the most labor-intensive rice <strong>production</strong> activity. W hether small-scale<br />
or broadacre, the individual ricegrowers’ final product quality <strong>and</strong> profitability are<br />
largely controlled by the timeliness, method, <strong>and</strong> management o f the harvest.<br />
REFERENCES<br />
Andrews, S. B., T. J. Siebenmorgen, E. D. Vofries, D. H. Loewer, <strong>and</strong> A. Mauromous-<br />
takos. 1993. Effects o f com bine operating parameters on harvest loss <strong>and</strong> quality<br />
in rice. Trans. ASAE 36(6):1599-1607.<br />
ASAE. 2000. ASAE Yearbook o f St<strong>and</strong>ards. 47th ed. St<strong>and</strong>ards, Engineering Practices,<br />
Data. American Society o f Agricultural Engineers, St Josep h, M I. For combines,<br />
see especially S343.3 <strong>and</strong> S396.2.<br />
Dilday, R. H. 1989. Milling quality o f rice: cylinder speed vs. grain moisture content<br />
at harvest. Crop Sei. 29(6): 1532-1535.<br />
Douthwaite, B,, G. R. Quick, <strong>and</strong> C. J. M . Tado. 1993. The stripper gatherer system<br />
for small-area rice harvesting. Agric. Eng. J. 2(4): 183-194.<br />
Gummert, M. et al. 1992. Performance evaluation o f an IR R I axial-flow paddy thresher.<br />
AMA 23(3):47-54,58.<br />
Hien, P. H. 1991. Development o f axial-flow thresher in Southern Vietnam. Agric.<br />
Mech. AsiaAfr, Latin Am. 22(4):4 2 -4 6 .<br />
Hunt, D. R. 1995. Farm Power <strong>and</strong> Machinery Management, 9th ed. Iowa State University<br />
Press, Ames, lA.<br />
Kondinm. 1998. Harvesters research report: survey reveals all on harvester hiccups.<br />
Farming Ahead with the Kondinin Group 7 8:24-39 (June).<br />
Lu, R., T. J. Siebenmorgen, R. H. Dilday, <strong>and</strong> T. A. Costello. 1992. Modefling long-<br />
grain rice milling quality <strong>and</strong> yield during the harvest season. Trans. ASAE 35(6):<br />
1905-1913.<br />
Quick, G. R. 1998a. Trash: a heavy cost to bear. Farmers' News!. 150(Jan,):12-17.'*
<strong>Rice</strong> Harvesting 543<br />
Quick, G. R. 1998b. Global assessment o f power threshers for rice. Agric. Mech. Asia<br />
Afr.S. Am. 2 9(3):47-54.<br />
Quick, G. R., <strong>and</strong> W. E Buchele. 1978. The Grain Harvesters, American Society o f<br />
Agricultural Engineers, St. Joseph, M I, 269 pp.<br />
Quick, G. R., <strong>and</strong> B. Douthwaite. 1994. A bright spot on the farm equipm ent scene:<br />
development o f stripper harvesting on small farms in Asia reveals unforeseen<br />
advantages. Resource 1(2): 1 4 -17 (June).<br />
Quick, G, R., <strong>and</strong> G. R.Hamüton. 1997. Recent evaluations o f grain harvester com binations<br />
in Australia. Paper 97-1066. ASAE Meeting, Minneapolis, M N, Aug.<br />
Quick, G. R., et al. 1996. <strong>Rice</strong> harvesters research report: tests show harvest managem<br />
ent is crucial. Farming Ahead with the Kondinin Group 57:32—45 (Sept.).<br />
Quick, G. R., et al. 1999. The <strong>Rice</strong> Harvesters Reference. RIRDC, Barton, ACT, 36 pp.<br />
Staton, B. C., T. A. Costello, X J. Siebenmorgen, <strong>and</strong> G. Huitink. 1994. An econom ic<br />
model o f rice harvesting. Paper 943524. Presented at the ASAE winter meeting at<br />
Atlanta, GA, Dec.<br />
Williams, R. et al, 1995. Improving % whole grain mülout. Farmers’Newsl. 145(June).<br />
Wimberly, J. E. 1983, Paddy <strong>Rice</strong> Postharvest Industry in Developing Countries. International<br />
<strong>Rice</strong> Research Institute, Manüa, The Philippines, 188 pp.<br />
SUGGESTED READINGS<br />
IRRI. 1995. World <strong>Rice</strong> Statistics, 1993-1994. International <strong>Rice</strong> Research Institute,<br />
Manila, The Philippines.<br />
Klinner, W. E., et al. 1987. A new concept in com bine harvester headers. /. Agric. Eng.<br />
Res. 38:37-45.<br />
Kutzbach, H. D., <strong>and</strong> G. R. Quick. 1999, In Harvesters <strong>and</strong> threshers, CÍGR H<strong>and</strong>book<br />
of Agricultural Engineering, Vol. 3, American Society o f Agricultural Engineers,<br />
St Joseph, M I, pp. 311-347.
d i o p t e r<br />
4.2<br />
Ríce Storage<br />
Terry A . H o w e ll, Jr.<br />
Deportmenfof Food Science<br />
University of Arkansos<br />
Foyettevilie, Arkansas<br />
INTRODUCTION<br />
EFFECTS OF RICE PRODUCTION ON STORAGE<br />
STORAGE FACILITIES AND PRACTICES<br />
Facilities<br />
Farm-Scale Bins<br />
Grain Elevators<br />
Practices<br />
IMPACT OF ENVIRONMENTAL CONDITIONS ON RICE QUALITY<br />
STORAGE INSECTS<br />
Internal Feeders<br />
<strong>Rice</strong> Weevil<br />
Lesser Grain Borer<br />
Angoumois Grain Moth<br />
External Feeders<br />
Red Flour Beetle<br />
Insect Damage to <strong>Rice</strong><br />
PROTECTION OF RICE FROM INSECTS<br />
Fumigants<br />
Protectants<br />
Aerosols<br />
Alternative Strategies<br />
Controlled Atmospheres<br />
Irradiation<br />
<strong>Rice</strong>: Origin, History, Technology, <strong>and</strong> Production, edited by C. Wayne <strong>Smith</strong><br />
ISBN 0-471-34516-4 © <strong>2003</strong> John Wiley & Sons, Inc.<br />
545
546 Produits <strong>and</strong> Product Processing<br />
Controlled Aeration, Grain Cooling, <strong>and</strong> Heating<br />
Organic Methods<br />
Integrated Pest Management<br />
MOLD AND FUNGAL PROBLEMS IN RICE<br />
RODENT PROBLEMS IN RICE<br />
RICE QUALITY DURING STORAGE AND AGING<br />
SUMMARY<br />
REFERENCES<br />
INTRODUCTION<br />
ii:;:<br />
iiii' ■<br />
I<br />
In this chapter we provide a basis for why <strong>and</strong> how rice is stored in tlie United<br />
States. Emphasis will be placed on current methods <strong>and</strong> practices <strong>and</strong> their impact<br />
on tlie U.S. rice industry. |i.ough rice is stored in its dried state prior to milling in<br />
farm-scale storage facilities <strong>and</strong> larger, rice milling cooperatives. Milled rice may be<br />
stored in warehouses or similar facilities prior to final marketing arid distribution.<br />
The h<strong>and</strong>ling conditions <strong>and</strong> facilities are critical to maintaining a stable, high-quality<br />
supply of rice.<br />
Rough rice is stored primarily to provide a year-round supply for end-use processing,<br />
whether it is consumed as whole rice or used in other products. Since rice<br />
is harvested at one tim e, the rice must be treated (dried) <strong>and</strong> preserved (stored) for<br />
processing. The methods used in storage vary widely based on how the rice will finally<br />
be utilized, but the methods may all be condensed to this fundamental concept; Protect<br />
rice from the environment, insects, mold <strong>and</strong> fungal growth, <strong>and</strong> rodents while<br />
preserving its milling <strong>and</strong> functional quality. Therefore, this chapter is organized to<br />
explain current facilities <strong>and</strong> practices, how the rice m aybe “attacked” by these factors,<br />
how storage strategies are designed to defend against these factors, <strong>and</strong> finally, how<br />
rice storage strategies may be used as a tool to improve rice quality.<br />
4<br />
EFFECTS OF RICE PRODUCTION ON STORAGE<br />
! -i: In harvest year 2000, 19 billion pounds o f rice were produced in the United States<br />
(USDA, 2000). These figures continue to increase each year, with some seasonal fluctuations<br />
due to crop rotations, weather adversity, <strong>and</strong> so on. The rice <strong>production</strong><br />
regions of the country are limited to the agricultural valleys o f California <strong>and</strong> the<br />
Mississippi Delta/Gulf coast o f Arkansas, Texas, Louisiana, Mississippi, <strong>and</strong> Missouri.<br />
Although the harvest does not take place simultaneously in all these areas, it is com <br />
pleted in about a tw o-m onth period each fall, Drying, milling, <strong>and</strong> further processing<br />
o f this rice must be spread out over the year to have an efficient, econom ical final<br />
product. Drying occurs as soon after harvest as possible, but remaining operations<br />
are executed closer to the time o f use. For instance, rice used in beer-m aking is milled<br />
<strong>and</strong> consumed within a 48-hour period, although it may be stored dry for up to a<br />
year. Therefore, safe rice storage operations can become vital to the delivery o f goodquality<br />
products throughout the year.<br />
4:4
<strong>Rice</strong> Storage 547<br />
STORAGE FACILITIES AND PRACTICES<br />
Facilities<br />
<strong>Rice</strong> is stored in two m ajor types o f facilities: farm-scale bins managed by producers<br />
<strong>and</strong> largCj grain elevators (usually concrete) managed by cooperatives or end-use<br />
processors. W ithin these two broad categories, there exists a wide range o f options <strong>and</strong><br />
techniques for proper rice storage. Facilities for large-<strong>production</strong> farms <strong>and</strong> export<br />
facilities may resemble grain elevators in size.<br />
Farm-Scale Bins<br />
Producers seeking to m aintain control o f their rice after harvest, may elect to construct<br />
storage facilities on-site in which rice may be dried <strong>and</strong> stored. The facilities<br />
typically, consist o f cylindrical steel bins with individual capacities varying between<br />
a few thous<strong>and</strong> <strong>and</strong> 50,000 bushels each (or m ore). The bins may then be arranged<br />
in rows or semicircles to facilitate the h<strong>and</strong>ling o f the rice (from loading the bins to<br />
drying the rice to unloading the bins). Figure 4.2.1 shows a semicircular set o f bins,<br />
<strong>and</strong> Figure 4.2.2 shows a set o f bins aligned in two rows. In each system tlie bins are<br />
equipped with com m on features: a fan for drying <strong>and</strong> aerating the rice, false floors<br />
for allowing airflow to the rice during fan operation, <strong>and</strong> a loading <strong>and</strong> unloading<br />
system. Optional features include spreading devices to distribute rice evenly in bins<br />
during loading <strong>and</strong> stirring devices to “turn” the rice within a bin. Figure 4.2.3 shows<br />
a cutaway o f a bin showing how a fan <strong>and</strong> false floor may be configured.<br />
Figure 4.2.1. Farm-scale bins arranged in a semicircular pottern. (Courtesy of Dennis<br />
Gardisser, University of Arkansas Cooperative Extension Service).
548 Products <strong>and</strong> Product Processing<br />
Figure 4.2.2, Faiim-scale bins arranged in two rows. (Courtesy of Dennis Gardisser, University of Arkansas<br />
Cooperative Extension Service.)<br />
Grain Elevators<br />
Grain elevators are able to store massive quantities o f rice, from a few hundred thous<strong>and</strong><br />
bushels to millions o f bushels. This is typically done in concrete silos (Figure<br />
4.2.4), but large steel bins may be used as well. Cooperatives or millers will begin<br />
receiving new-crop rice immediately after harvest <strong>and</strong> use large driers to reduce the<br />
moisture content below 13% . Once dried, the rough rice m aybe stored until milling.<br />
Plat storages may also be used for large quantities o f rice, although they are not<br />
very com m on in the United States. In this system, the rice is stored in long, flat bunkers<br />
which are equipped with fans <strong>and</strong> aeration systems (Figure 4.2.5). These types o f<br />
storage facilities are quite popular in Australia.<br />
Grain elevators receive their rice in truckloads. At harvest it is not uncom m on for<br />
these trucks to wait for days in queue to be unloaded, all the while holding wet rice at<br />
temperatures at or above 90°F, ideal conditions for mold growth <strong>and</strong> grain respiration.<br />
In essence, these trucks become storage ecosystems which should be m onitored carefully.<br />
Later discussions about mold <strong>and</strong> fungal growth relate to this issue in particular.<br />
Practices<br />
<strong>Rice</strong> is dried immediately before or after binning, depending on the equipment available<br />
<strong>and</strong> management practices o f the postharvest manager. W lien spreading devices<br />
are used to load rice evenly into a bin, a cross section o f the rice bulk will show mature
<strong>Rice</strong> Storage 549<br />
FILL HATCH & MECHANICAL<br />
GRAIN SPREADER<br />
GRAIN STIRRER<br />
n<br />
GRAIN SURFACE-<br />
FAN<br />
i<br />
BIN UNLOADING AUGER<br />
BIN PLENUM<br />
CONCRETE FOUNDATION<br />
FLOOR SUPPORTS<br />
Figure 4.2.3. Cufawoy of a bin showing fan ond folse floor plocement (Heprinted with permission from Storoffe<br />
of CemI Sm s ofíé Jheir Fioducis, 4th ed., 1992, American Association of Cereol Chemists, St. Paul, Minnesota.)<br />
Figure 4.2.4.<br />
Industria! storage bins.<br />
grain in the center <strong>and</strong> immature grain, grass, <strong>and</strong> dust at the edges o f the bin. Conversely,<br />
when rice is simply top-loaded without a spreader, the fines <strong>and</strong> immatures<br />
will congregate in the center o f the bin. Stirring devices are often used to alleviate this<br />
problem, but the profile of the bulk rice will never be completely homogeneous.
55D<br />
Produds <strong>and</strong> Product Processing<br />
Figure 4.2.5.<br />
Fiat storage system.<br />
After drying, the rice is not left alone in its facility for the duration o f storage.<br />
Often, rice is aerated by pushing (or pulling) ambient air through the bin for short<br />
periods o f time. This practice is used initially'to reduce temperature <strong>and</strong> moisture<br />
content gradients in the rice which develop during drying <strong>and</strong>/or during loading.<br />
Subsequent aeration is used to reduce the grain temperature <strong>and</strong> eliminate hot spots<br />
(see mold/fungus section). Aeration practices are as numerous as there are facilities.<br />
Each manager uses aeration in a unique pattern, although almost all o f them are trying<br />
to accomplish the same goals.<br />
The am ount o f aeration necessary to reduce rice temperature during storage may<br />
be calculated using the fan curves supplied by fan manufacturers. Table 4.2.1 contains<br />
fan performance information for 1750-rpm centrifugal fans manufactured by GSI,<br />
Inc. When the static pressure is read from the air plenum, a flow rate m aybe calculated<br />
T A B LE 4.2.1 Fa n F lo w R a te s (d m ) vs. Static P r e s su re ( 1 7 5 0 -r p m C e n trifu g a l G S I F a n s)<br />
Stalls Pres;sure{in.)<br />
Model<br />
hp<br />
0 2 4 6 8 10<br />
C F - 3 3 6 ,0 0 0 5 ,0 0 0 4 ,0 0 0<br />
C F - 5 5 8 ,7 5 0 7 ,3 0 0 6 ,1 0 0<br />
C F - 7 . 5 7 .5 1 2 ,2 0 0 1 0 ,8 0 0 9 ,1 0 0<br />
C F - 1 0 10 1 3 ,4 5 0 1 2 ,0 5 0 1 0 ,7 0 0 9 ,0 0 0<br />
C P - 1 5 1 5 1 7 , 0 0 0 1 5 ,2 0 0 1 3 ,4 0 0 1 0 ,8 0 0<br />
C F - 2 0 2 0 2 0 ,5 0 0 1 9 ,0 0 0 1 7 ,0 0 0 1 5 ,7 5 0 1 3 ,3 0 0<br />
C F - 2 5 2 5 2 4 ,0 0 0 2 2 ,7 5 0 2 1 ,0 0 0 1 9 ,0 0 0 1 6 ,0 0 0<br />
C F - 3 0 3 0 2 8 ,1 0 0 2 5 ,6 0 0 2 3 ,6 0 0 2 1 ,0 0 0 1 9 ,7 0 0 1 6 ,0 0 0<br />
C F - 4 0 4 0 3 2 , 7 5 0 3 0 ,7 5 0 2 8 ,7 5 0 2 6 , 7 5 0 2 4 ,2 5 0 2 0 ,2 5 0
<strong>Rice</strong> Storage 551<br />
based on the amount o f rice in the bin. For instanccj if a static pressure gauge gives a<br />
reading o f 2 in. for a 20-hp fan, the flow rate is 19,000 ftVmin (cfm ). If the bin capacity<br />
is known, a flow rate per bushel may be calculated. If the bin contains 25,000 bu o f<br />
rice, the flow rate would be 0.76 cfm/bu. This flow rate would be considered very high<br />
in many commodities (e.g., wheat <strong>and</strong> corn) but is a moderate flow rate in rice.<br />
Fans on farm-scale bins are sized for drying, primarily at flow rates o f 0.5 to 1.0<br />
cfm/bu. In other com modities, aeration is conducted near 0.1 cfm/bu. Also, fans in<br />
commercial-scale storage are sized for aeration, closer to 0.1 cfm/bu. The higher flow<br />
rates in farm-scale rice storage may provide many advantages to m aintaining rice<br />
quality during the storage spason. Intuitively, the higher the flow rate, the quicker<br />
a cool front may be passed through a bin. Table 4,2,2 shows how different flow rates<br />
affect the time to pass a cold front through a bin. The flow rate is directly proportional<br />
to the am ount o f time necessary for the passage. To do a quick calculation to determine<br />
the range o f tim es necessary to pass a cool front through a bin, the following<br />
equation may be used:<br />
time =<br />
12<br />
flow rate<br />
(1)<br />
where time is in hours <strong>and</strong> flow rate is in cfm/bu. So, in farm -stored rice, where<br />
flow rates are high, the total tim e needed for aeration can be reduced significantly<br />
compared to commercial storage <strong>and</strong> other grains. From our previous example, the<br />
time required to pass a cool front through this bin would be 16 to 20 hours. The use<br />
o f aeration as a cooling tool is discussed in more detail in the section “Protection o f<br />
<strong>Rice</strong> from Insects.”<br />
The use o f aeration in rice has one m ore condition that differentiates it from<br />
other grains: The effects o f rewetting rice are very significant <strong>and</strong> must be monitored<br />
closely. As stated in Chapter 4.3, rice is consumed as a whole kernel in most instances<br />
<strong>and</strong> the prevention o f brealcage <strong>and</strong> Assuring is critical. A prim ary cause o f fissure formation<br />
is moisture adsorption-rewetting. During the storage season, aeration should<br />
be conducted only when the relative hum idity-tem perature com bination o f the air is<br />
below the equilibrium moisture content (EM C) conditions o f the rice. In essence, rice<br />
at 13% moisture content should not be aerated with m oist air. Table 4.2.3 contains the<br />
EMC o f rice at different temperature-relative humidity combinations. Rewetting will<br />
be slow when tlie airflow is high <strong>and</strong> used in short segments, but it may be significant<br />
if moist air is blown continually through the rice.<br />
TABLE 4.2.2.<br />
T im e R e q u ire d fo P a ss a C o o l Front<br />
t h r o u g h a B in at Sele cted F lo w R a te s<br />
Flow Rate<br />
{cini/bu)<br />
Time<br />
{hours}<br />
0 .1 1 2 0 - 1 5 0<br />
0 ,2 5 4 8 - 6 0<br />
0 .5 2 4 - 3 0<br />
0 ,7 5 1 6 - 2 0<br />
1 1 2 - 1 5
552 Products <strong>and</strong> Produtt Processing<br />
T A B L E 4.2.3.<br />
E q u ilib r iu m M o is t u r e C o n te n t (E M C ) o f R o u g h R ice a s a Fu n c tio n of<br />
T e m p e ra tu re a n d M C “<br />
Temperolure<br />
(°f)<br />
Relafive H um idity ( % )<br />
45 60 75 90<br />
3 5 1 2 .0 1 3 .9 16 .1 19 .1<br />
4 5 1 1 .5 1 3 .4 1 5 .5 1 8 .5<br />
6 0 1 1 ,0 1 2 .8 1 4 .8 1 7 . 7<br />
7 5 1 0 .5 1 2 .3 1 4 .2 1 7 .0<br />
9 0 1 0 .1 1 1 .8 1 3 . 7 1 6 .4<br />
“B ased o n the m o d ified H e n d e rso n e q u a tio n {A S A E , 19 9 7),<br />
The type o f ductwork <strong>and</strong> flooring used in aeration are critical to the overall<br />
performance o f the aeration system. Figure 4.2.6 depicts five types o f duct systems<br />
for the false floors of grain bins. The goal o f any aeration ducting is to have an even<br />
distribution o f air moving through the bin. The single tube has obvious limitations,<br />
the Y-system is moré efficient, but the complete false floor is best. Figure 4.2.7 is a<br />
representation o f the errors that can occur when the rice in a bin has not been leveled<br />
properly. The air will seek to travel the path o f least resistance, <strong>and</strong> when the rice is<br />
uneven at its surface, airflow can become “channeled” around some areas in the bin.<br />
Stirring devices are extremely useful in leveling the rice surface to prevent uneven<br />
airflow patterns within the bin.<br />
IMPACT OF ENVIRONMENTAL CONDITIONS ON RICE QUALITY<br />
The primary function o f any storage facility is to protect rice fi:om deterioration<br />
caused by extreme conditions o f temperature <strong>and</strong> relative humidity. The ambient<br />
conditions at harvest typically are a high temperature {m id-80s to 100°F) with variable<br />
relative humidity (depending on the area). Table 4.2.3 m aybe consulted to underst<strong>and</strong><br />
the impact o f these conditions on the EM C o f rice. <strong>Rice</strong> drying occurs at temperatures<br />
o f 90°F or better. Thus, at the time o f storage, the rice will have a high temperature <strong>and</strong><br />
low EMC, corresponding to a relative humidity near 50% . The bulk rice will act as an<br />
excellent insulator <strong>and</strong> will have little temperature movement <strong>and</strong> moisture content<br />
change (other than some equilibration), given a sound bin <strong>and</strong> constant conditions.<br />
As mentioned previously, however, rice is aerated to reduce the grain temperature<br />
<strong>and</strong> to reduce the variation in moisture content o f the rice. Thus the environmental<br />
conditions are not held constant.<br />
To underst<strong>and</strong> the rationale behind lowering the grain temperature quicldy, respiration<br />
must be examined. <strong>Rice</strong> is a living seed <strong>and</strong> thereby respires, even in the<br />
harvested, stored state. Respiration involves tlie consum ption o f oxygen <strong>and</strong> carbohydrates<br />
(usually in tlie form o f sugar) to produce carbon dioxide <strong>and</strong> water <strong>and</strong> energy<br />
(usually in the form o f heat):<br />
CûHiaOfi + 6O 2 6CO2 + 6H 2O + energy (2)<br />
This reaction behaves m uch like any reaction in nature— it proceeds more quickly at<br />
higher temperatures. In respiration, not only is rice being consumed (in the form of
<strong>Rice</strong> Storage 553<br />
Figure 4,2.6. Top view of five cotrunoo duct systems for aeration. (Reprinted with permission from Storage of Cereal<br />
Cram <strong>and</strong> Urn Products, 4th ed., 1992, American Association of Cereal Chemists, St. Poul, Minnesota.)<br />
sugars), but heat is also being generated. So, at higher temperatures, respiration can<br />
become quite detrimental to rice quality. The respiration creates heat that increases<br />
the rate o f the reaction, <strong>and</strong> the cycle continues. Conversely, when the rice is cooled<br />
(by aeration or other means), respiration slows <strong>and</strong> its im pact is not as severe.<br />
The moisture content o f rice can play a m ajor role in the rate of the respiration<br />
reaction. DiUahunty et al. (2001) showed that at moisture contents below 14%, respiration<br />
rates were negligible, but the rates increased exponentially as moisture content<br />
increased (Figure 4.2.8).<br />
The direct result o f temperature <strong>and</strong>/or moisture content abuse o f stored rice will<br />
be the increased likelihood o f the presence o f mold <strong>and</strong> other contaminating bacteria.<br />
It is well established that the presence o f yeast <strong>and</strong> molds in foods is related directly<br />
to the moisture content in a food, its water activity. M ost aerobic bacteria, on the<br />
other h<strong>and</strong>, grow better in high-temperature environments; in fact, when testing for<br />
the presence o f bacteria, m ost analytical tests incubate samples at the norm al body<br />
temperature for human beings (98.6'’F).<br />
M ost extension service guides in rice storage call for the reduction o f rice tem <br />
perature in accordance with the climatic seasons by keeping the rice within 10 to<br />
20“F o f the am bient-air conditions. This recommendation carries through the fall,<br />
winter, <strong>and</strong> spring. The merits o f this system are obvious in the fall <strong>and</strong> winter— to
554 Products <strong>and</strong> Product Processing<br />
Grain surface<br />
Fan<br />
Figure 4.27.<br />
Effects of uneven groin surfaces on oirflow patterns within a bin,<br />
60-<br />
— Predicted Cypress<br />
— Predicted Bengai<br />
•— Baiiey's Data ■<br />
■è IQ -<br />
15 20<br />
Moisture content (%)<br />
25<br />
Figure 4.2.8. Effect of moisture content on respiration of rice. (Reprinted with<br />
permission from Dillahunty et al, 2001.)<br />
reduce the grain temperature. In the spring <strong>and</strong> summer, voluntary heating o f the rice<br />
may be ill advised. The heating will encourage respiration o f the rice, growth o f any<br />
bacteria present, <strong>and</strong> m obility <strong>and</strong> propagation o f any storage insects that are present.<br />
A research project to evaluate the extension recommendations on rice storage would<br />
be very beneficial to rice millers, who would prefer to keep their rice cooled.<br />
Alluded to earlier, rice is an excellent insulator, <strong>and</strong> unless it is directly acted upon<br />
by aeration or otlier external operation, it will retain its temperature. Figure 4.2.9 is<br />
a schematic showing how stored rice within a bin responds to seasonal temperature<br />
fluctuations. A core area will remain virtually unchanged, <strong>and</strong> only those areas near<br />
the walls o f the bin or the top surface will have temperature fluctuations.
<strong>Rice</strong> Storage 555<br />
. 7 ^<br />
False floor<br />
Figure 4,2.9.<br />
Locotion of bulk rice within a<br />
One last phenom enon, associated particularly with rice in steel bins, is the influence<br />
o f solar radiation on rice properties. This theory asserts that rice in the southern<br />
<strong>and</strong> western sections o f a bin will receive a greater im pact from solar radiation<br />
than rice in the northern <strong>and</strong> eastern sections. <strong>Rice</strong> in the north <strong>and</strong> east receives<br />
m orning sunlight at cooler temperatures than do the other locations. This can cause<br />
moisture migration <strong>and</strong> temperature gradients within a bin. In unaerated bins, this<br />
phenom enon can be significant (Howell et al., 2000); however, in aerated bins, there<br />
does not appear to be a difference in rice properties based on spatial location (Ranalli<br />
et a l, 2001).<br />
STORAGE INSECTS<br />
Perhaps the greatest issue in maintaining a consistent, stable supply o f rice is its<br />
protection against the deterioration caused by storage insects. LUce any grain, rice<br />
becomes a target for these msects quicldy after binning (Figure 4.2.10). The <strong>origin</strong> o f<br />
infestations is often a mystery; some insects may begin attack on the rice in the field<br />
prior to harvest, others may migrate to storage bins after rice is loaded, but overall,<br />
questions o f their <strong>origin</strong> still persist. Other sources o f contam ination include crevices<br />
<strong>and</strong> cracks in storage <strong>and</strong> milling equipm ent <strong>and</strong> contam ination from other grain in<br />
the case o f storage cooperatives (USDA, 1986). In this section we describe the com <br />
m on types o f storage insects <strong>and</strong> their damage <strong>and</strong> treatments against insect damage.<br />
Insects that affect stored rice are commonly classified into two categories: internal<br />
feeders <strong>and</strong> external feeders. Internal feeders are so named because their lai'vae<br />
consume kernels internally <strong>and</strong> emerge from kernels as adults. Weevils <strong>and</strong> borers are<br />
two types o f internal feeders. Weevils deposit their eggs in a small hole in the kernel,<br />
cover it with a mucus filling, <strong>and</strong> then the hatched larva feeds on the kernel as it<br />
matures to adulthood, eventually emerging from the kernel. Borers lay tlieir eggs on<br />
kernels; their larvae then bore into the kernel, feed on the kernel to maturity, <strong>and</strong> then<br />
emerge. External feeders typically feed on “compromised” kernels— those that have<br />
been damaged, broken, fed upon by internal feeders, or are otherwise unwholesome.<br />
In some instances, external feeders will feed on whole kernels.
556 Produits <strong>and</strong> Produtt Processing<br />
868.212 Special grades <strong>and</strong> requirements.<br />
A special grade, when applicable, is supplemental to the grade assigned under 868.210. SUch special<br />
grades for rough rice are established <strong>and</strong> determined as follows:<br />
[a) Infested rough rice. Tolerances for live insects for infested rough rice are defined according to<br />
sarnpliiig designations as follows:<br />
(1) Representative sample. The representative sample consists of the work portion, <strong>and</strong> the file sample if<br />
needed <strong>and</strong> when available. The rough rice (except when examined according to paragraph (a)(3) of this<br />
section will be considered infested if the representative sample contains two or more live weevils, or one<br />
live weevil <strong>and</strong> one or more other live insects injurious to stored rice or five or more other live insects<br />
injurious to stored rice.<br />
(2) Lot as a whole (stationary). The lot as a whole is considered infested when two or more live weevils,<br />
or one live rveevil <strong>and</strong> one or more other live insects injurious to stored rice, or five or more other live<br />
insects injurious to stored rice, or 15 or more live Aiigoumois moths or oUier live moths mjnrious to stored<br />
rice are found in, on, or about the lot. ><br />
(3) Sample as a whole during continuous loading/unloading, The minimum sample size for rice being<br />
sampled during continuous loading/unloading is 5Q0 grams per each 100,000 pounds of rice. The sample<br />
as a whole is considered infested when a component (as defined in FGIS instructions) contains two or<br />
mote live weevils, or one live weevil <strong>and</strong> one or more other live insects injurious to stored rice, or five or<br />
more other live insects injurious to stored rice.<br />
Figure 4.2.10.<br />
USDAGrainInspecHon, Packers, <strong>and</strong> StockyardAdministrationSt<strong>and</strong>ards for Infested<strong>Rice</strong>.<br />
Internal Feeders<br />
<strong>Rice</strong> Weevil<br />
'0\\•'<br />
As the rice weevil [Sitophilus oryzae (L.)] is discussed, note that almost all o f its<br />
characteristics may be applied to others in the weevil family (Sitophilus spp.). The<br />
rice weevil is the m ost destructive insect to stored rice (Grist, 1986). Adult weevils<br />
have a long snout with chewing m<strong>and</strong>ibles. <strong>Rice</strong> weevil adults grow to about 3 m m in<br />
length (Pedersen, 1992). The egg, larval, <strong>and</strong> pupal stages are spent inside a kernel, so<br />
the actual size o f the weevil depends on the kernel size. In addition, the development<br />
within the kernel protects weevils from predators <strong>and</strong> other threats. The development<br />
cycle takes 4 weeks <strong>and</strong> rice weevils can live up to 8 months (Pedersen, 1992). The<br />
ability o f the weevil to fly is debated, although rice weevils do have small wings<br />
(Kiritani, 1965; Taylor, 1971). Figure 4.2,11A contains an image o f an adult rice weevil.<br />
Lesser Grain Borer<br />
Grain borers behave in a manner similar to weevils, with the exception that their<br />
eggs are laid outside the rice kernel. Their damage can be extensive, as they consume
<strong>Rice</strong> Storage 557<br />
Figure 4.2.11. Fredoininani storage insects of rice: (4) rice weevil; (B) lesser grain<br />
borer; (C) ongouinofs grain moth; (B) red flour beetle. (From iiSDA-GMPRC Web site.)<br />
kernels during development <strong>and</strong> adulthood. O f the pests in the borer family, the lesser<br />
grain borer [Rhyzopertha dominkus (R)] is the main pest in rice. One of its unique<br />
characteristics is that it leaves dust <strong>and</strong> frass behind which can pack into the rice,<br />
thus restricting airflow during aeration (Pedersen, 1992). An adult lesser grain borer<br />
may be seen in Figure 4.2.1 IR. Like other insects mentioned here, the developmental<br />
period lasts for about 1 month <strong>and</strong> the adult lifespan can reach 8 montlis under ideal<br />
conditions,<br />
Angoumois Grain Moth<br />
The Angoumois grain moth [Sitotroga cerealella (O.)], another internal feeder, causes<br />
less damage than either weevils or borers, but must be discussed nonetheless. In<br />
infested grain, the adult moths may be found on the headspace of a bin, as they cannot<br />
penetrate a packed grain mass (Pedersen, 1992). Like borers, eggs are laid outside rice
55B<br />
Products ond Product Processing<br />
kernels, <strong>and</strong> the first larva chews its way into kernels. As the larval stages progress, an<br />
escape hole is made in the grain, the larva pupates, <strong>and</strong> then the mature moth forces<br />
itself out of the hole (Pedersen, 1992). The moth’s presence may often be detected by a<br />
characteristic webbing on the grain surface. An adult moth is shown in Figure 4.2.11C.<br />
E xtern a l F e e d e rs<br />
Red Flour Beetle<br />
The red flour beetle [sometimes called the rust-red flour beetle; Tribolium castaneum<br />
(O.)] is used here as a representative of all external feeders, realizing that others will<br />
have their own particular habits <strong>and</strong> characteristics. The red flour beetle (Figure<br />
4.2.11D) is almost indistinguishable from the confused flour beetle {T. confusum)^<br />
<strong>and</strong> they have similar habits. The beetle feeds on dust <strong>and</strong> damaged kernels primarily.<br />
When present in significant numbers, the beetle will release a pungent odor (USDA,<br />
1986). These beetles can become a large problem in mills <strong>and</strong> other processing facilities<br />
where dust collects.<br />
In se c t D a m a g e to R ice<br />
Insect damage to rice is very difficult to measure accurately as a whole. The impact<br />
of insects on rice manifests itself in several direct <strong>and</strong> indirect ways. Direct damage<br />
may be caused by the consumption of rice, contamination of the rice, <strong>and</strong> damage<br />
to storage structures; indirect damage may occur due to heating of the grain mass<br />
(leading to other problems), distribution of microorganisms among the rice, <strong>and</strong><br />
consumer resistance to contaminated products (Pedersen, 1992).<br />
Internal feeders cause the most damage to kernels, with one study showing that<br />
rice weevils consume 30% of the kernel when developing in wheat (White, 1953). Loss<br />
may also be absorbed as rice is downgraded due to the presence of insect-damaged<br />
kernels or excessive insect parts. Figure 4.2.10 contains a small portion of the federal<br />
grade st<strong>and</strong>ards for rice, explaining the specific guidelines for infested rice. It is important<br />
to point out that these are the minimum st<strong>and</strong>ards of insect detection, <strong>and</strong><br />
many processors <strong>and</strong> millers have higher st<strong>and</strong>ards.<br />
The combined respiratory activity of many insects is often large enough to cause<br />
heating to occur in rice. These “hot spots” can then become a major source of deterioration,<br />
raising the moisture content of the rice (another respiration product), leading<br />
to increased mold growth <strong>and</strong> rice quality degradation. Hot spots are one of the first<br />
signs that immediate action is necessary. As insects migrate through the rice, seeking<br />
optimum conditions of food <strong>and</strong> environment, they bring microflora along <strong>and</strong> are<br />
capable of transmitting tliem to uncontaminated rice (Pedersen, 1992). The heat <strong>and</strong><br />
moisture increases that accompany insects also aid in the growth of mold <strong>and</strong> fungi.<br />
Finally, the effects of insect damage in rice reaches its peak with the final consumer,<br />
who dem<strong>and</strong>s a defect-free product. The impact of live insects or insect fragments in<br />
processed products is profound, with consumers likely to seek a competitor’s product<br />
<strong>and</strong>/or register their complaint with the food company. Our society has a very low<br />
tolerance for contaminated food.
<strong>Rice</strong> Storage 559<br />
P R O T E C T IO N O F R IC E F R O M I N S E C T S<br />
When discussing the inhibition o f growth <strong>and</strong> re<strong>production</strong> of insects in stored rice,<br />
one must consider how the constraints of the storage ecosystem can be altered to<br />
minimize insect activity. Insects require an adequate food supply <strong>and</strong> a suitable environment<br />
in which to live. Obviously, the food supply is available, but one might notice<br />
that for many insects, the grain must be damaged or contain dust <strong>and</strong> other frass in<br />
order to provide an optimum condition for growth. Efficient harvesting <strong>and</strong> h<strong>and</strong>ling<br />
to minimize the breakage <strong>and</strong> other problems is the first line o f defense against insect<br />
attack. In addition, storage facilities should be cleaned thoroughly from year to year.<br />
Then environmental conditions (including temperature, moisture content, <strong>and</strong> air<br />
composition) can be altered, if necessary, to further inhibit insect propagation. Insects<br />
must respire, like any other aerobic organism, <strong>and</strong> manipulating the reactants<br />
of the respiration equation [equation (1)] can cause the reaction to be slowed or<br />
stopped.<br />
Reduced temperature will reduce the rate of tlie respiration reaction, slowing<br />
locomotory activity <strong>and</strong> the re<strong>production</strong> ability of most insects. Gray (1948) showed<br />
that reduced temperatures yielded a reduction in the number of eggs laid <strong>and</strong> hatch<br />
rate <strong>and</strong> an increase in the length of the developmental stages of flour beetles (Tri~<br />
bolium spp.). The optimal growth <strong>and</strong> development temperatures have been proposed<br />
to be between 25 <strong>and</strong> 33°C, while 13 to 25°C <strong>and</strong> 33 to 35°C would be considered<br />
suboptimal, <strong>and</strong> finally, at temperatures below 13“C <strong>and</strong> above 35“C> most insects will<br />
eventually die (Fields, 1992). In addition, the moisture content of the rice can play a<br />
major role in the survival of insects. Cotton et al. (1960) showed that at moisture<br />
contents below 10% in wheat, adult rice weevils were unable to survive as well as at<br />
12%. Similar findings were found for the confused flour beetle. <strong>Rice</strong> is stored between<br />
12 <strong>and</strong> 13% moisture content, slightly lower than the optimum conditions for most<br />
insects. Finally, reducing the oxygen available for respiration is a common defense<br />
against insects. In the next sections we detail the more established techniques for<br />
combating insects.<br />
F u m ig a n ts<br />
Fumigants are deadly gases used to kill insects. These gases are also harmful to humans<br />
<strong>and</strong> animals, <strong>and</strong> their application must be done by trained operators. Fumigants are<br />
typically applied by aerating the gas through a bin or warehouse that has been sealed to<br />
prevent leaks. Once the environment is sufficiently saturated, the insects will inhale<br />
the chemical <strong>and</strong> die. The exposure periods have a wide range, depending on the<br />
size of the bin <strong>and</strong> the species of insects. Phosphine (commonly called phostoxin)<br />
<strong>and</strong> methyl bromide are the only two fumigants that are labeled safe for stored grain<br />
in the United States, Chloropicrin is labeled safe for the area below a false floor of<br />
a bin. In addition, the use of methyl bromide is being phased out as a result of<br />
the 1991 Clean Air Act. Fumigants can be very effective, but insects may develop<br />
a tolerance that limits their future effectiveness. In addition, once a fumigation is<br />
complete, insects may be able to come back, especially if all were not killed during<br />
the treatment.
560 Produits <strong>and</strong> Product Protassing<br />
P ro te c ta n ts<br />
Protectants are liquids <strong>and</strong> solids that are used in a variety of situations to reduce insect<br />
activity. Liquid protectants may be applied in empty bins as a pretreatment prior<br />
to loading with rice. Others may be sprayed onto or mixed with rice as it enters a bin,<br />
<strong>and</strong> others may still be applied to the top layers of the rice, where insect activity is most<br />
likely to occur. Malathion, pyrethrins, <strong>and</strong> chlorpyriphos-methyl are the most common<br />
liquid protectants, while malathion, chlorpyriphos-methyl, pirimiphos- methyl,<br />
<strong>and</strong> diatomaceous earth are commonly used in granular form. The diatomaceous<br />
earth formulations are abrasive <strong>and</strong> cut the cuticle of insects, leading to desiccation.<br />
However, their abrasiveness can also damage processing equipment <strong>and</strong> mills. These<br />
chemicals are often combined to magnify their potency. Like fumigants, insects may<br />
develop I'esistances to these chemicals.<br />
A e ro s o ls<br />
Aerosols are mixtures of insecticides <strong>and</strong> solvents that have been atomized <strong>and</strong> are<br />
used as treatments in open spaces (Cogburn, 1985). These are commonly used to<br />
treat for moths <strong>and</strong> can be effective in strips placed in bin head spaces or as mists,<br />
smokes, or vapors.<br />
A lte rn a tiv e S tr a te g ie s<br />
The growth in environmental concerns about insecticides has led to a reduction in<br />
the number that are allowable for use in the United States. Thus research efforts<br />
have focused on developing new <strong>technology</strong> that will be both effective against insects<br />
<strong>and</strong> harmless to the environment. In most cases, effective controls are available, but<br />
tlie costs become prohibitive. In the following sections we describe the most recent<br />
advances in insect control utilizing inert metliods.<br />
Controlled Atmospheres<br />
Controlled atmospheres or modified atmospheres have been studied as an alternative<br />
to traditional fumigants for at least 20 years (Cogburn, 1985). The technique requires<br />
modification of the storage environment to reduce the respiration abilities of the<br />
insects. This maybe accomplished by increasing the carbon dioxide concentration, reducing<br />
the oxygen concentration, or adding another gas (typically, nitrogen). Oxygen<br />
reduction is an expensive process <strong>and</strong> is not very practical, <strong>and</strong> nitrogen atmospheres<br />
require airtight storage environments that are rare. Carbon dioxide, on the other<br />
h<strong>and</strong>, is an inexpensive commodity. Treatments can be continuous by circulating the<br />
gas continually through the storage bin, or they can he done in a “batch” mode, like<br />
a fumigant treatment. In the batch style, the exposure periods can be long, reducing<br />
their viability in commercial operations, where shutdowns are costly.<br />
Irradiation is the exposure of foods (rice in this case) to radiation at levels high enough<br />
to destroy insects <strong>and</strong> other microorganisms. Harein <strong>and</strong> Davis (1992) state that
<strong>Rice</strong> Storage 561<br />
there are two primary methods for accomplishing this: direct exposure of the grain<br />
to destroy insects or by releasing sterilized males into a population to compete with<br />
fertile males. Irradiation has been met with much consumer resistance, <strong>and</strong> there are<br />
virtually no facilities available for its sustained use, but its potential is very good. If<br />
the U.S. Food <strong>and</strong> Drug Administration fully endorses the method <strong>and</strong> encourages its<br />
use, irradiation could become a common treatment for rice coming out of the field.<br />
Controlled Aeration, Grain Cooling, <strong>and</strong> Heating<br />
Controlled ambient aeration is a storage technique, generally using a thermostatically<br />
activated controller, to reduce the rice temperature as quickly as possible after drying.<br />
The technique maybe configured in a variety of ways, from cooling in one temperature<br />
cycle, three temperature cycles, or any other variation. The concepts discussed in<br />
the section “Storage Facilities <strong>and</strong> Practices” still apply to this technique. In the threecycle<br />
program, the controller is set to aerate the rice when ambient-air conditions are<br />
at 75”F <strong>and</strong> below (with appropriate relative humidity values as well). Once the rice<br />
is below that temperature, the controller is reset to 60°F <strong>and</strong> the process is repeated;<br />
similarly at the third cycle, 45°F. The time necessary for each cycle will depend on the<br />
yearly weather, fan speed, <strong>and</strong> bin size. Ranalli et al. (2001) had good success against<br />
insects <strong>and</strong> their eggs using this program. The controllers are inexpensive, <strong>and</strong> there<br />
are some commercial manufacturers of similar systems.<br />
Grain coolers (sometimes called rice conditioners) are refrigeration units equipped<br />
with a strong fan. These machines can be connected to bins <strong>and</strong> used to aerate<br />
the bins with low-temperature, low-humidity air. Manufacturer claims indicate that<br />
rice temperatures can be lowered to 60°F in a few days <strong>and</strong> that rice quality improves<br />
during storage. This technique, followed by controlled aeration, maybe very attractive<br />
in the near future.<br />
Heating has been receiving attention from rice millers <strong>and</strong> processors who are<br />
looking to kill insects during shutdown periods. The technique has been very effective<br />
in mills <strong>and</strong> warehouses. Portable heaters are brought into the facility <strong>and</strong> used as<br />
either st<strong>and</strong>-alone units or connected to vent systems. Temperature-sensitive equipment<br />
is removed or protected, <strong>and</strong> then the facility is heated to 120°F for 3 to 5 days.<br />
Temperature probes are used to verify that hard-to-reach spots are receiving adequate<br />
temperatures.<br />
Organic Methods<br />
All of the alternative methods discussed here, with the exception of irradiation, maybe<br />
considered organic. The organic foods movement in the United States has increased<br />
tremendously over the last 10 years <strong>and</strong> has reached the rice industry in many forms.<br />
Lundberg Family Farms in Richvale, California has pioneered organic rice farming,<br />
often struggling with storage methods that do not use chemicals. Considering the<br />
current situation regarding chemicals used in preservation, traditional producers will<br />
be reduced to using methods very similar to these.<br />
In te g r a te d P e st M a n a g e m e n t<br />
Insect problems in stored rice should be attacked with a proactive approach centered<br />
on accurate sampling of rice for quality <strong>and</strong> insect presence, trapping in top surfaces
562 Products <strong>and</strong> Produit Processing<br />
to monitor insect activity, <strong>and</strong> monitoring grain temperature for irregularities that<br />
may be the result of insect activity. Any of these tools alone will not give an accurate<br />
picture of the bin. All three togetlier, though, will allow a storage manager to assess<br />
the conditions of the rice <strong>and</strong> take appropriate action.<br />
M O L D A N D F U N G A L P R O B L E M S IN R IC E<br />
I<br />
There are over 100,000 strains of fungi populating the eartli, each having unique<br />
characteristics (Christensen <strong>and</strong> Meronuck, 1986). But all must have a food source; all<br />
grow by the use of small, branched cells called mycelium which decay their food source<br />
prior to consumption; all reproduce by spores, <strong>and</strong> aU require water <strong>and</strong> a favorable<br />
environment to grow (Christensen <strong>and</strong> Meronuck, 1986). In addition, varieties of<br />
spores can exist in the most extreme conditions, <strong>and</strong> many spores are entrapped in<br />
the air around storage facilities. From this description it is easy to see how fungi can<br />
grow <strong>and</strong> reproduce in improperly stored rice; their presence in stored rice is not<br />
debated, but their growth must be inhibited.<br />
The first defense against microflora is to have a low moisture content in stored<br />
rice. At moisture contents below 14% (corresponding to relative humidities below 60<br />
to 70% depending on the temperature; see Table 4.2.3), most fungi wUl not grow.<br />
Many managers accept this, practice it, <strong>and</strong> yet still have problems. Usually, their<br />
mistake is to take a small sample for moisture content testing <strong>and</strong> assuming that the<br />
rice is all at that condition. With the advent of single-kernel moisture testers, managers<br />
can rapidly know not only the moisture co^ntent, but also the spread associated with<br />
the average value. For example, rice harvested at 20% moisture will have some kernels<br />
with 14% <strong>and</strong> some with 25%, even in a small subsample. Drying processes will reduce<br />
the spread to some degree, but it will exist even after drying. Storage managers must<br />
take extra precautions to ensure that the moisture content of the rice has a small<br />
spread <strong>and</strong>/or is evenly distributed; otherwise, kernels with high moisture content<br />
will provide a perfect place for mold <strong>and</strong> fungi growth.<br />
The results of mold growth are widely reported in other works (Christensen <strong>and</strong><br />
Meronuck, 1986; Sauer et ah, 1992), <strong>and</strong> only those problems common to rice are<br />
discussed here. Perhaps, the most common problem associated with mold <strong>and</strong> fungal<br />
growth in rice is stackburn, or yellowing of tlie kernel. Stackburn is the result of<br />
a variety of factors, all seemingly related to mold <strong>and</strong> fungal growth. These factors<br />
include high temperatures, high moisture content, <strong>and</strong> mold growth, Dillahunty et<br />
ah (2001) discussed these common causes <strong>and</strong> theories <strong>and</strong> also showed the effect of<br />
high-temperature storage on the color of rice. Their results indicate that temperature<br />
was the dominant factor in causing yellowing, but mold <strong>and</strong> fungal tests were not<br />
conducted. Bason et ah (1990) investigated the combination of all three of these<br />
conditions <strong>and</strong> found that nonfungal conditions may be the dominant source of the<br />
damage. However, one of the effects of many molds is increased temperature, with<br />
Aspergillus flavus <strong>and</strong> A. c<strong>and</strong>idus producing temperatures of 55®C (131°F) as a result<br />
of growth. <strong>Rice</strong> held at these temperatures for extended periods (2 to 3 days) will<br />
experience some degree of yellowing. Thus hot spots must be addressed immediately.<br />
The remaining results of mold <strong>and</strong> fungi growth in rice are reduced seed germination,<br />
mustiness, <strong>and</strong> caldng (Sauer et ah, 1992). A result of ahnost every variety
i<br />
Ric6 Storage 563<br />
of storage fungi is reduced seed germination. As they consume the kernel, some<br />
species target the embryo specifically, leaving the seed barren. Mustiness <strong>and</strong> calcing<br />
are a partnered process. Mustiness will develop even when other tests make the grain<br />
appear sound, but the rice will eventually be characterized by discoloration <strong>and</strong> a foul<br />
odor (Sauer et al., 1992). Mustiness, in turn, gives way to webbing or caking, in which<br />
kernels stick to one another in a mass. The caked areas aid in hot-spot development<br />
as air flows around the dense areas.<br />
R O D E N T P R O B L E M S IN R IC E<br />
Like any stored product, stored rice is plagued by rodents seeking food. These animals<br />
will infest any facility, bin, mill, or otherwise. Rats <strong>and</strong> mice will cause significant<br />
damage to wooden structures, sacks, pallets, <strong>and</strong> stored rice. In addition to the loss<br />
of product, the rodents bring disease, <strong>and</strong> the remnants o f their feeding provide a<br />
breeding ground for storage insects. Rodents are divided into three major categories:<br />
Norway rats {Rattus norvegkus), roof rats [R. rattus), <strong>and</strong> mice ( M ms musculus).<br />
The first line of defense against rodents is to rodent-proof buildings associated<br />
with rice storage. Steel <strong>and</strong> concrete bins are perhaps the easiest structures to rodentproof;<br />
however, preventive measures must be taken in each situation. Extreme care<br />
should be taken to minimize openings, wooden materials, <strong>and</strong> other means of access<br />
to a building.<br />
A second line of defense is poisoning. Poisons typically consist of blood thinners,<br />
which cause the rodent to hemorrhage internally. Rodenticides are not recommended<br />
for use against single rodents, as the risks of contamination of the rice outweigh the<br />
outcome (Harris <strong>and</strong> Baur, 1992). Additionally, rodents that ingest the poisons rarely<br />
will die at the poison site, <strong>and</strong> finding them unexpectedly can cause problems for<br />
inspectors, customers, <strong>and</strong> employees.<br />
A last line of defense is trapping. Traps work in a similar manner to poisons,<br />
except that the rodent is stopped at the trap site. Traps seem to be acceptable to both<br />
regulatory <strong>and</strong> management personnel in the food industry (Harris <strong>and</strong> Baur, 1992).<br />
R IC E Q U A L IT Y D U R IN G S T O R A G E A N D A G IN G<br />
There has been an increase in research, in recent years, examining the effects of storage<br />
conditions <strong>and</strong> duration on the physicochemical properties of rice. <strong>Rice</strong>, typically<br />
consumed whole, is unique compared to other grains, which are typically ground.<br />
Although the properties of wheat <strong>and</strong> corn change during storage, the effect o f these<br />
changes in those grains is not nearly as important as changes in rice, particularly in<br />
head rice yield (HRY). The combined effects of storage on rice quality are commonly<br />
called aging. For most properties, aging produces positive changes; however, it can<br />
induce negative results as well. In this section we explore the effects of aging on HRY,<br />
cooking properties of whole rice, <strong>and</strong> pasting properties of rice flours.<br />
Head rice yield is the single most important measure of rice quality. The percentage<br />
reveals how much of a sample of rough rice remains whole after milling. Because<br />
head rice sells for about twice the price of broken rice, high HRY values translate
564 Product <strong>and</strong> Product Processing<br />
directly to profits for producers. For years, producers have stated that storage duration<br />
affects HRY of their rice positively. Recent experimental results appear to substantiate<br />
these claims, Daniels et al. (1998) investigated the effects of drying conditions <strong>and</strong><br />
storage conditions on HRY <strong>and</strong> other properties. Regardless of drying technique, HRY<br />
of the rice cultivar. Cypress increased at least 10 percentage points within 2 months.<br />
Farm-scale tests in 1999-2000 <strong>and</strong> 2000-2001 showed similar results, although the<br />
magnitude of the increase was much lower (Howell et al„ 2000; Ranalli et al., 2001).<br />
The positive effects of aging on HRY cannot be understated <strong>and</strong> undoubtedly result<br />
in higher profits for many producers who are able to store rice on-site.<br />
Several studies have investigated the effects of storage on the coolcing <strong>and</strong> eating<br />
quality of rice. These properties are closely linked to consumer acceptability <strong>and</strong><br />
preference. Cooking quality is typically measured by cooking rice in a fixed volume of<br />
water <strong>and</strong> measuring both weight gains <strong>and</strong> volume expansion. Both properties are<br />
then used to describe cooking quality. Perdón et al. (1997) examined the effects of<br />
storage conditions (time, temperature, <strong>and</strong> moisture content) on cooking properties<br />
<strong>and</strong> found little correlation between water absorption ratio <strong>and</strong> any of the variables.<br />
The same held true for volume expansion. High-temperature storage did yield an<br />
increase in water absorption over the first 2 to 3 months, but eventually the value decreased<br />
back to its <strong>origin</strong>al level. Daniels et al. (1998) showed similar results, with both<br />
properties increasing only slightly during storage, with no definable trend. Indudhara<br />
Swamy et al. (1978) showed increases in water absorption with storage duration over<br />
a 1-year period. The absorption then leveled off. In summary, cooldng properties of<br />
rice are slightly improved with aging, although the mechanisms for these changes are<br />
not well understood.<br />
Pasting properties of rice flours are evaluated to determine how well rice flour<br />
will respond in baking <strong>and</strong> slurry applications. Pasting properties are obtained by<br />
heating a slurry of known rice flour concentration in a mixer <strong>and</strong> recording the<br />
torque response of the mixer paddle. During the initial heating period, the torque<br />
increases as the slurry thickens to gelatinization. Then, at a constant temperature, the<br />
viscosity breaks down. Eventually, as the slurry is cooled, the viscosity again rises.<br />
From these experiments, several features may be extracted, but the peak viscosity<br />
<strong>and</strong> final viscosity are the most widely reported. Perdón et al. (1997) showed initial<br />
increases in peak viscosity after 2 months (more pronounced for higher storage<br />
temperatures) <strong>and</strong> a leveling off to 6 months. The final viscosity only appeared to<br />
increase at the highest storage temperature. Daniels et al. (1998) did not have any<br />
significant trends of pasting properties with storage duration. Similar to the work<br />
by Perdón et al. (1997), Hamaker et al. (1993) showed an increase in peak viscosity<br />
over the first 3 months of storage; then tiie viscosity leveled off. Others (Villareal et<br />
a l, 1976; Indudhara Swamy et a l, 1978) have shown similar results. Again, for these<br />
properties, the effects of storage are not well understood, though it is accepted that<br />
pasting viscosity increases with storage duration.<br />
Overall, the effects of aging on rice quality are still being discovered <strong>and</strong> refined.<br />
Research investigating the mechanisms for these property changes (changes in starch<br />
content, changes in protein content, etc.) is under way. Millers <strong>and</strong> processors must<br />
be aware of these effects so that they may make appropriate decisions while processing<br />
rice <strong>and</strong> so that they can underst<strong>and</strong> why rice received at different times in the year<br />
behaves differently during processing.
Ríce Storage 565<br />
S U M M A R Y<br />
Overall, the storage o f rice is a straightforward operation. The successful storage manager'must<br />
maintain quality rice by considering how its quality is attacked by insects,<br />
microflora, <strong>and</strong> rodents <strong>and</strong> by seeking to minimize the effects of these enemies. In<br />
addition, an underst<strong>and</strong>ing o f the effects of aging on rice quality is crucial to successful<br />
storage.<br />
R E F E R E N C E S<br />
ASAE. 1997. ASAE St<strong>and</strong>ards. St<strong>and</strong>ard D245.5. American Society of Agricultural<br />
Engineers, St. Joseph, MI, pp. 500-516..<br />
Bason, M. L., P. W. Gras, H. J. Banks, <strong>and</strong> L. A. Esteves. 1990. A quantitative study<br />
of the influence of temperature, water activity, <strong>and</strong> storage atmosphere on the<br />
yellowing of paddy endosperm. /. Cereal Sei 12:193-201.<br />
Christensen, C. M., <strong>and</strong> R. A. Meronuck. 1986. Quality Maintenance in Stored Grains<br />
<strong>and</strong> Oilseeds. University of Minnesota Press, Minneapolis, MN.<br />
Cogburn, R. R. 1985. Rough rice storage. In B. O. Juliano (ed.), <strong>Rice</strong>: Chemistry <strong>and</strong><br />
Technology. American Association of Cereal Chemists, St. Paul, MN.<br />
Cotton, R. X , H. H. Walkden, G. D. Wliite, <strong>and</strong> D. A. Wilbur. 1960. Causes o f Outbreaks<br />
ofStored-Grain Insects. Kans. Agric. Exp, Stn. Bull. 416.<br />
Daniels, M. J., B, P. Marks, X J. Siebenmorgen, R. W. McNew, <strong>and</strong> J. P. Meullenet.<br />
il998. Effects of long-grain rough rice storage <strong>history</strong> on end-use quality. /. Food<br />
Sei .63:832-835.<br />
Dillahunty, A. L., X J. Siebenmorgen, R. W. Buescher, D. E. <strong>Smith</strong>, <strong>and</strong> A. Mauromoustakos.<br />
2001, Effect of moisture content <strong>and</strong> temperature on respiration rate<br />
o f rice. Cereal Chem. 77(5);541-543.<br />
Dillahunty, A. L., X J. Siebenmorgen, <strong>and</strong> A. Mauromoustalcos. 2001. Effect of temperature,<br />
exposure duration <strong>and</strong> moisture content on color <strong>and</strong> viscosity of rice.<br />
Cereal Chem. 78(5)\559~563.<br />
Fields, P. G. 1992. The control of stored product beetles <strong>and</strong> mites with extreme<br />
temperatures. /. Stored Prod. Res. 28:89-118.<br />
Gray, H. E. 1948. The biology of flour beetles. Milling Production, 13:7,18-22.<br />
Grist, D, H. 1986. <strong>Rice</strong>, 6th ed. Longman, London.<br />
Hamaker, B. R., X J. Siebenmorgen, <strong>and</strong> R. H. Dilday. 1993. Aging o f rice in the first<br />
six months after harvest. Ark. Farm Res. 42(1): 8-9.<br />
Harein, P. K„ <strong>and</strong> R. Davis. 1992. Control of stored grain insects. In D. B. Sauer (ed.),<br />
Storage o f Cereal Grains <strong>and</strong> Their Products. American Assoc. Cereal Chem, St.<br />
PaukMN.<br />
Harris, K. L., F, J. <strong>and</strong> Baur. 1992. Rodents. In D. B. Sauer (ed.), Storage o f Cereal Grains<br />
<strong>and</strong> Their Products. American Association of Cereal Chemists, St. Paul, MN.<br />
Howell, X. A., M. S. Slape, X Bellman-Horner, <strong>and</strong> J.-F. Meullenet. 2000. Effects of<br />
storage conditions (temperature, relative humidity, <strong>and</strong> duration) on rice quality<br />
in laboratory <strong>and</strong> farm-scale tests. Paper 006038 presented at the 2000 ASAE<br />
Annual International Meeting. American Society o f Agricultural Engineers, St.<br />
Joseph, ML
566 Products <strong>and</strong> Product Processing<br />
Indudhara Swamy, Y. M,, C. M. Sowbhagya, <strong>and</strong> K. R. Bhattycharya. 1978. Changes<br />
in physicochemical properties of rice with aging. /. Sei Food Agrie. 29:627-639.<br />
Kiritani, K. 1965. Biological studies on the SHophilus complex (Coleóptera: Curculionidae)<br />
in Japan. /, Stored Prod. Res. 1:169-176.<br />
Pedersen, J. R. 1992. Insects: identification, damage, <strong>and</strong> detection. In D. B. Sauer<br />
(ed.), Storage of Cereal Grains <strong>and</strong> Their Products. American Association of Cereal<br />
Chemists, St. Paul, MN.<br />
Perdón, A. A., B. P. Marks, T. J. Siebenmorgen, <strong>and</strong> N. B. Reid. 1997. Effects of rough<br />
rice storage conditions on the amylograph <strong>and</strong> cooking properties of medium-<br />
grain rice cv. Bengal. Cereal Chem. 74(6):864-867.<br />
Ranalli, R. P., T. A. Howell, <strong>and</strong> D. R. Gardisser. 2001. Controlled ambient aeration<br />
during rice storage. II. Effects on rice quality. Paper 016115 presented at the<br />
2001ASAE Annual International Meeting. American Society o f Agricultural Engineers,<br />
St. Joseph, ML<br />
Sauer, D. B., R. A. Meronuck, <strong>and</strong> C. M. Christensen. 1992. Microflora. In D. B. Sauer<br />
(ed.), Storage o f Cereal Grains <strong>and</strong> Their Products. American Association of Cereal<br />
Chemists, St. Paul, MN.<br />
Taylor, T. A. 1971. On the flight activity of Sitophilus zeamais Motsch. (Coleóptera,<br />
Curculionidae) <strong>and</strong> some other grain-infesting beetles in the field <strong>and</strong> store, J,<br />
Stored Prod. Res. 6:295-306.<br />
USDA. 1986. Stored Grain Insects. Agriculture H<strong>and</strong>book 500. U.S. Department of<br />
Agriculture, Agriculture Research Service, Washington, DC,<br />
USDA. 1995. United States St<strong>and</strong>ards for Rough <strong>Rice</strong>. U.S. Department of Agriculture,<br />
Grain Inspection, Packers <strong>and</strong> Stockyards Administration, Washington, DC. Effective<br />
September 11, 1995.<br />
USDA. 2000. <strong>Rice</strong> situation <strong>and</strong> outlook. In <strong>Rice</strong> Yearbook. U.S. Department of Agriculture,<br />
Economic Research Service, Washington, DC.<br />
White, G. D. 1953. Weight loss in stored wheat caused by insect feeding. Journal of<br />
Econ. Ento, 46:609-610.<br />
Villareal, R. M., A. P. Resurrección, L. B. Suzuki, <strong>and</strong> B. O. Juliano. 1976. Changes in<br />
physicochemical properties of rice during storage. Staerke 28(3):88-94.
Clio p te r<br />
4.3<br />
Rough <strong>Rice</strong> Drying <strong>and</strong> M illing Quality<br />
A u k e C n o s s e n<br />
Unilever Research<br />
The Netherl<strong>and</strong>s<br />
T e riy JL S ie b e n m o rg e n ,<br />
W a d e Y a n g r a n d<br />
Ru$}jco B a u tista<br />
Food Science Department<br />
University of Arkonsas<br />
Fayetteville, Arkansas<br />
INTRODUCTION<br />
MILLING QUALITY DEFINITIONS AND TERMS<br />
QUALITY ISSUES AT HARVEST<br />
Property Characterization<br />
Respiration Effects<br />
Factors Affecting Respiration<br />
DRYING ROUGH RICE<br />
Equilibrium Moisture Content<br />
Relating Drying Conditions to Head <strong>Rice</strong> Yield<br />
Relating Moisture Content Reduction to Head <strong>Rice</strong> Yield<br />
Drying Systems<br />
SUMMARY AND ONGOING RESEARCH<br />
REFERENCES<br />
I N T R O D U C T IO N<br />
<strong>Rice</strong> is unique as a cereal grain in that it is used almost exclusively as direct human<br />
food. As such, kernel quality is o f utmost concern. During rice milling, both head<br />
rice (milled kernels that are three-fourths or more of the <strong>origin</strong>al kernel length)<br />
<strong>and</strong> broken kernels are produced. The manner in which rice is dried can affect the<br />
relative weight of head rice to brokens. Despite the fact that there has recently been<br />
<strong>Rice</strong>; Origin, History, Technology, <strong>and</strong> Production, edited by C. Wayne <strong>Smith</strong><br />
ISBN 0-471-34516-4 © <strong>2003</strong> John Wiley & Sons, Inc.<br />
567
568 Products <strong>and</strong> Product Processing<br />
an increased dem<strong>and</strong> for broken kernels, particularly by the pet food industry, the<br />
goal o f the rice industry remains that of producing the maximum amount of head<br />
rice per unit weight of rough or paddy rice. Due to the economic emphasis placed on<br />
head rice, any mention of rice drying should therefore include the effects On milling<br />
quality. This is especially true since the success of a rice drying operation is largely<br />
gauged in terms of minimizing head rice yield reduction, Thus it is appropriate that<br />
drying <strong>and</strong> milling quality be discussed jointly in this chapter.<br />
Although the primary focus of this chapter is the unit operation of postharvest<br />
drying, factors in the field prior to harvest that affect kernel quality are also presented.<br />
Due to the immense importance of overall kernel quality to the rice drying <strong>and</strong> milling<br />
industry, <strong>and</strong> subsequent companies that further process rice, a truly systemic view<br />
of rice “drying’’ <strong>and</strong> kernel quality should be taken. In keeping with the nature of<br />
this book in addressing the practical aspects of rice as a cereal grain, more emphasis<br />
will be placed on quality aspects of drying than on drying theory. The latter subject<br />
is addressed more fully in otlier books. In particular, Kunze <strong>and</strong> Calderwood (1980)<br />
<strong>and</strong> Wang <strong>and</strong> Luh (1991) are excellent sources of information for more theoretical<br />
<strong>and</strong> in-depth treatments of drying per se. Additionally, Siebenmorgen (1994) reports<br />
findings pertaining directly to the importance of moisture content (MC) in affecting<br />
milling quality of rice from preharvest through the assessment o f milling quality in<br />
laboratory mills.<br />
The bulk o f this chapter builds on the material in these previous books <strong>and</strong> chapters<br />
<strong>and</strong> describes recent research in the general areas of drying <strong>and</strong> property characterization<br />
relevant to kernel quality. Preharvest <strong>and</strong> harvest factors that can affect<br />
drying <strong>and</strong> milling quality, specifically kernel property distributions <strong>and</strong> respiration<br />
rates, are discussed. Subsequently, studies relating the rate of moisture removal during<br />
drying to milling quality reduction will be summarized. Finally, ongoing research <strong>and</strong><br />
thoughts on relating kernel material properties <strong>and</strong> changes in these properties during<br />
the drying process to drying behavior are presented.<br />
M IL L IN G Q U A L IT Y D E F I N I T I O N S A N D T E R M S<br />
<strong>Rice</strong>, in its unprocessed state, is typically referred to as rough rice but is often also called<br />
paddy, particularly in international locations. These terms are often used interchangeably<br />
in tlie rice industry, even in the titles given to processing equipment (e.g., rough<br />
rice graders or paddy separators). In this initial stage a protective outer hull or husk<br />
surrounds the rice caryopsis. Hulls are relatively easy to detach from the caryopsis.<br />
This process is accomplished commercially <strong>and</strong> in labs by machines consisting of a<br />
pair of rollers that rotate in opposite directions <strong>and</strong> at different peripheral speeds to<br />
create a shearing action. The hulls represent approximately 20% of the <strong>origin</strong>al rough<br />
rice mass.<br />
Brown rice remains after the hulls have been removed from rough rice. Brown<br />
rice, unless packaged <strong>and</strong> marketed for consumption as a brown rice product, is<br />
typically milled immediately after hulling to remove tlie bran layers <strong>and</strong> germ. The<br />
bran <strong>and</strong> germ are simultaneously removed during milling <strong>and</strong> remain mingled as<br />
a single “bran stream” in practically all rice mills in the U.S. Various systems are<br />
used for both commercial <strong>and</strong> laboratory milling applications. The current trend<br />
commercially is to mill brown rice in stages or brakes, with each bralce consisting
Rough <strong>Rice</strong> Drying <strong>and</strong> Milling Quolify 569<br />
of a specific type of milling machine performing a specific milling function. There<br />
are typically three to four brakes that perform the entire mfiling operation for most<br />
milled rice products.<br />
The mass of bran removed in the composite milling process represents approximately<br />
10% of the rough rice mass, but this value varies depending on the degree of<br />
bran removal. The index describing the extent to which bran has been removed from<br />
brown rice, referred to as the degree o f millings is extremely important since the greater<br />
the degree to which rice is milled, the more kernel mass is removed <strong>and</strong> transferred to<br />
' the bran stream. Also, there is some thought that suggests that longer milling durations<br />
required to attain greater degrees of milling are more likely to impart mechanical<br />
damage resulting in broken kernels.<br />
In terms of sensory <strong>and</strong> functional quality, degree ofmilling plays a tremendously<br />
important role. Since the bran remaining on the kernel surface has a far different<br />
composition than that of the kernel endosperm, varying the amount of bran remaining<br />
on kernels can change overall processing performance dramatically. For example,<br />
Perdón et al. (2001) showed that increasing the degree of milling (decreasing the<br />
amount of bran remaining on kernels) increased the rice s peak viscosity, an indicator<br />
ofiunctional performance in cooking <strong>and</strong> other end-use operations. The importance<br />
of degree ofmilling as a quality index will be discussed once other indices of milling<br />
quality are defined.<br />
Once the milling operation is complete, milled whole kernels, broken kernels,<br />
<strong>and</strong> fragments of kernels remain. The U.S. Department of Agriculture (USDA, 1995)<br />
defines head rice as those milled kernels that are at least three-fourths the length of<br />
whole kernels. Brokens are categorized as second heads, brewers, or screenings, depending<br />
on the overall particle size.<br />
The summed mass of head rice <strong>and</strong> brokens is referred to as the milled rice mass or<br />
total mass. Wlieii this mass is expressed as a percentage of the <strong>origin</strong>al rough rice mass,<br />
the familiar terms milled rice yield or total yield are defined. Values of milled rice yield<br />
can range from 68 to 74% <strong>and</strong> are highly dependent on the degree of milling (Andrews<br />
et al., 1992; Bennett et al., 1993). Once the brokens are separated from the head rice,<br />
the head rice yield (HRY) can be calculated as die mass of head rice expressed as<br />
a percentage of tlie <strong>origin</strong>al rough rice mass. Although dependent on the degree of<br />
milling (Bennett et al., 1993; Sun <strong>and</strong> Siebenmorgen, 1993; Reid et al., 1998), HRY is<br />
extremely subject to the physical condition <strong>and</strong> integrity of the kernels. This physical<br />
condition can be affected by a myriad of factors occurring during physiologic development<br />
<strong>and</strong> during postharvest operations. Production variables, including chalkiness,<br />
insect damage (Fryar et al., 1986), <strong>and</strong> ftingal diseases (C<strong>and</strong>óle et a l, 2000), can cause<br />
the overall strength <strong>and</strong> integrity of the kernel to be reduced with consequent lower<br />
HRYs, Postharvest factors causing fissure formation in the kernel, which drastically<br />
weaken the kernel <strong>and</strong> lower HRYs, are presented in detail in a subsequent section, In<br />
summary, the milled rice yield is to a large extent determined by the compositional<br />
structure of rice kernels <strong>and</strong> the degree of milling achieved. However, HRY, while<br />
inherently determined by tlie strength <strong>and</strong> integrity of the kernel as achieved during<br />
development, is also extremely sensitive to many post<strong>production</strong> factors; it thus has<br />
been <strong>and</strong> continues to be the subject of much research.<br />
From a practitioner's st<strong>and</strong>point, milling quality is often reported as a ratio, with<br />
the HRY expressed over the milled rice yield. Thus a typical milling quality for a lot<br />
may be reported as 58/70, which would imply a HRY of 58% <strong>and</strong> a milled rice yield of
570 Products qnd Product Processina<br />
70%. These numbers have considerable economic significance. Although both indices<br />
are important, the HRY is certainly critical since the value of a unit o f head rice has<br />
historically been worth approximately twice that of a unit of brokens.<br />
Q U A L IT Y I S S U E S AT H A R V E S T<br />
<strong>Rice</strong> is typically harvested at moisture contents (MCs) higher than those acceptable for<br />
long-term “safe” storage. There are several reasons for this, including that rice will fissure<br />
while on the panicle if allowed to dry below certain levels <strong>and</strong> subsequently incur<br />
rapid moisture adsorption (Kunze <strong>and</strong> Hall, 1967; Kunze, 1977; Siebenmorgen <strong>and</strong><br />
Jindal, 1986; Kunze <strong>and</strong> Sarwar, 1987; Siebenmorgen et al., 1992). Rain or exposure to<br />
high relative humidity could cause such adsorption. Other reasons for early harvest<br />
include prevention of loss due to lodging of stalks, bird infestation, <strong>and</strong> shattering<br />
(kernels naturally dislodging from the panicle prior to harvest). The latter losses are<br />
difficult to quantify; little work has been published that quantifies these losses. As<br />
discussed below, harvesting at high MC values certainly has limits, as HRY values of<br />
rice harvested at high MC values can be lower than those from rice that is allowed to<br />
mature more fuUy. This occurrence is believed to be due to the structural wealcness of<br />
immature kernels (Siebenmorgen et al., 1992; Sun <strong>and</strong> Siebenmorgen, 1993). These<br />
observations, along with simultaneous research in drying that has identified the need<br />
for better underst<strong>and</strong>ing of incoming rice properties, prompted a series of studies<br />
quantifying individual kernel property distributions at harvest.<br />
P ro p e rty C h a ra c te riz a tio n<br />
Recent work in drying <strong>and</strong> milling rice has shown that rice should not be viewed as<br />
a bulk commodity at a single MC, but rather as a composite of individual kernels<br />
comprising the bulk (Siebenmorgen, 1998). Visual observation of rice kernels on a<br />
panicle at harvest, especially at high MC, clearly indicates that there is a range in<br />
size <strong>and</strong> maturity of kernels. Because kernel properties, particularly MC, have such<br />
a profound effect on kernel behavior in postharvest processes, it is critical to quantify<br />
individual kernel property distributions of rice at various stages of harvest.<br />
Advances in kernel property measurement <strong>technology</strong> have allowed more accurate<br />
quantification of kernel property distributions. More specifically, the Shizouka<br />
Seiki individual kernel moisture meter, introduced to the United States in the late<br />
1980s, is capable of singulating kernels from a bulk sample <strong>and</strong> introducing the kernels<br />
to a pair of rotating metal rollers. As the kernel is crushed between the rollers, the<br />
electrical resistance across the rollers is measured <strong>and</strong> a MC value is obtained from a<br />
predetermined calibration. The meter has been found to be as or even more precise<br />
than measuring individual kernel MC values by an oven-drying method (Siebenmorgen<br />
et al., 1990). The meter can be used to measure individual kernel MC distributions<br />
in a bulk of kernels. Examples of such distributions are given in Figure 4.3.1. This<br />
information can in turn be related to HRY reduction of rice, particularly at various<br />
stages of maturity, A series of studies centered on the use of this instrument (Kocher<br />
et ah, 1990; Siebenmorgen et al„ 1997; Bautista <strong>and</strong> Siebenmorgen, 1999) has addressed<br />
this issue, with the goal of estimating kernel quality changes as harvest MC<br />
changes.
Rough <strong>Rice</strong> Drying <strong>and</strong> Milling Quality 571<br />
Figure 4,3,1. Individual kernel moisture content distribution profiles for Bengol medium-grain rice at two<br />
harvest moisture contents (HMC), Stuttgart, Arkansas, 1999.<br />
Kocher et al, (1990) first used the meter in rice to measure the individual kernel<br />
MC distributions in long-grain rice. They determined that MC distributions (frequency<br />
distributions o f number of kernels vs. kernel MC) were multimodal in shape,<br />
particularly at high harvest MCs, <strong>and</strong> were not evenly distributed about tlie mean.<br />
The variance in individual kernel MCs was a linear function of the average MC.<br />
The correlation coefficient was positive, so a decrease in average harvest MC was<br />
accompanied by a decrease in the variance of the individual kernel MCs. Kocher et al.<br />
also determined that the percentage of kernels with MC values below an assumed safe<br />
rewetting threshold of 14% MC increased significantly as the average MC decreased<br />
below approximately 18%,<br />
Based on this work, subsequent research was conducted to determine whether<br />
these distributions could be attributed to the location where the seed was born with<br />
respect to the main stem or tillers. Results of a greenhouse study (Holloway et a l,<br />
1995) revealed that the main stem <strong>and</strong> primary <strong>and</strong> secondary tillers exhibited very<br />
similar, multimodal distribution patterns. Therefore, the different MC peaks or modes<br />
could not be explained by the main stem or tiUer influence. However, Holloway et al.<br />
speculated that the modes could have been caused by individual ker*nel MC plateaus<br />
observed during kernel development by Yoshida (1981). At a given harvest MC, a<br />
greater number of kernels would exist at the plateau MC values than at other MC<br />
levels. Thus, when the MCs of all individual kernels are tallied to obtain the MC<br />
frequency distribution, modes would tend to form around the plateau MC values.<br />
The SataJce image analyzer has also been used to characterize kernel properties<br />
at harvest more completely. This instrument is capable of singulating kernels from<br />
a bulk <strong>and</strong>, by the use of two cameras, measures the length, width, <strong>and</strong> thickness of<br />
individual kernels. Bautista <strong>and</strong> Siebenmorgen (1999) found that individual kernel<br />
dimensional distributions at harvest were not statistically normal. Variations in the<br />
distributions were dependent on the harvest MC in that higher harvest MCs were<br />
accompanied by more variation in kernel dimensions. Bautista <strong>and</strong> Siebenmorgen<br />
showed that kernels harvested over a range of MCs had similar dimensions once dried.<br />
This is illustrated in Figure 4.3.2, which shows that once dried to 12% MC, kernel<br />
thicknesses of rice harvested over a range of 22.9 to 14.7% MC came to approximately<br />
the same thicloiess distribution. Bautista <strong>and</strong> Siebenmorgen also showed that kernel
572 Products <strong>and</strong> Product Processing<br />
1.7 1.8 1.9 2 2.1 2.2 2<br />
Kernel Thickness, mm<br />
Figure 4.3.2. Individua! kernel thickness distributions from ponicles harvested at the indicated<br />
harvest moisture contents (HMC) <strong>and</strong> dried to about 1 2 % moisture content.<br />
shrinkage was not the same in each dimension as the kernel dried. Kernel thickness<br />
had the highest percentage shrinkage, followed by length <strong>and</strong> then width.<br />
As indicated by Kocher et al. (1990), one of the practical reasons for quantifying<br />
kernel MC distributions was to determine if an appreciable percentage of kernels during<br />
the harvest season were drying to MCs below levels which, upon rewetting, would<br />
cause moisture adsorption fissures. The detrimental effects of moisture adsorption<br />
were observed as early as the raid-1930s (Stahel, 1935). Chau <strong>and</strong> Kunze (1982), who<br />
documented tremendous differences in kernel MG values from the top to the bottom<br />
of panicles <strong>and</strong> from panicle to panicle, concluded that the longer rice is left in the<br />
field, the greater the probability that the lower MC rice will fissure before these kernels<br />
are harvested.<br />
Chau <strong>and</strong> Kunze’s hypotliesis regarding rice Assuring in the field is supported by<br />
work conducted by Bautista <strong>and</strong> Siebenmorgen (2000). In this study the number of<br />
kernels with MC values below 14%, as determined with a Shizoulca Seiki moisture<br />
meter, was plotted for samples of Bengal medium-grain rice from Stuttgart, Arkansas<br />
ranging in harvest MC from 14 to 26%. The number of fissured kernels was also<br />
determined by h<strong>and</strong> counting <strong>and</strong> is plotted in Figure 4.3.3, which indicates that the<br />
number of kernels below 14% increased in the same manner as the number of fissured<br />
kernels. It is speculated that the fissured kernels are the result of rapid moisture<br />
adsorption by the dried kernels. Figure 4.3.3 also shows that the number of kernels<br />
above 22% MC, which is an indication of the number of immature kernels, increased<br />
steadily as the harvestMC increased above 16%. As indicated below, immature kernels<br />
typically break during milling, resulting in lowered HRY values. Thus the number of<br />
immature kernels as well as the number of fissured kernels from moisture adsorption<br />
should be minimized on the basis of optimizing milling quality. Based on this premise,<br />
Figure 4.3.3 indicates that the optimal MC to harvest Bengal rice at Stuttgart, Arkansas<br />
would be approximately 19% from strictly a milling quality st<strong>and</strong>point. It is stressed<br />
that this MC level could change for different varieties <strong>and</strong> growing locations.<br />
Siebenmorgen et al. (1992) investigated HRY values of field samples of rice harvested<br />
over a range of MC values. Samples of Newbonnet, Tebonnet, <strong>and</strong> Lemont<br />
long-grain varieties grown in northeastern Arkansas were harvested at bulk MC values
Rough Ríce Drying ond Millinfl Quality 573<br />
Figuro 4.3.3, Optimal harvBSt moisture content (MQ for Bengal medium-grain rice based on the percentage of<br />
individual kernels with MC > 2 2 % <strong>and</strong> individual kernels with MC < 1 4 % <strong>and</strong> the number of fissured kernels<br />
across o range of harvest MC values. Onto collected in Stuttgort, Arkansas, 1999. (From Bautista <strong>and</strong><br />
Siebenmorgen, 2000.)<br />
g,<br />
?<br />
Ë<br />
3<br />
Figure 4.3,4. Head rice yield (HRY) <strong>and</strong> overage moisture content (MQ for<br />
Newbonnet variety rice on each indicated harvest date, <strong>and</strong> the incidence of rain during<br />
the 1989 harvest season, (From Siebenmorgen etal., 1992.)<br />
ranging from 12 to 25%. The individual kernel MC distributions of these samples<br />
were measured <strong>and</strong> then the samples were dried <strong>and</strong> milled. Figures 4.3.4 through<br />
4.3.6 indicate the milling quality trends throughout the harvest seasons. For Newbonnet,<br />
little HRY reduction occurred even though rain was experienced after bulk<br />
MCs dropped to below 12%, However, for Tehonnet <strong>and</strong> Leniont, the HRY dropped<br />
drastically after a rain occurred on rice that had field-dried to below 12% MC. This<br />
clearly indicated the practical economic effects of rapid moisture adsorption by dried<br />
kernels.<br />
Figures 4.3.4 to 4.3.6 also show that HRY values were reduced by harvesting<br />
above 21 to 22% MC, suggesting that if long-grain varieties are harvested above<br />
approximately 21% MC under Arkansas conditions, the presence of immature kernels
574 Products <strong>and</strong> Product Processing<br />
80<br />
g 60-<br />
0)<br />
8 ^0<br />
i f<br />
(P ft«<br />
X 20<br />
H RY..MC - — EMC 1 rain<br />
-------------------------<br />
\ “ T<br />
\ \ •<br />
— / V \<br />
i\ / \ \<br />
1 \ \h y V<br />
....<br />
30<br />
'26<br />
20 -g<br />
Ô<br />
£<br />
his I<br />
' i i l 1 1 . 1 .<br />
260 270 280 290 300 310<br />
Harvest Tim e (Day of Year)<br />
320 10<br />
Figure 4.3.5. Head rice yield (HRY) <strong>and</strong> average moisture content (WQ on each<br />
harvest dote for Lemont variety rice, calculated equilibrium MC (EMQ based on the daily<br />
average ambient air conditions, <strong>and</strong> the incidence of rain during the 1990 harvest<br />
season. (From Siebenmorgen etal., 1992.)<br />
270 260 290 300 310<br />
Harvest Time (Day of Year)<br />
320<br />
Figure 4.3.6. Head rice yield (HRY) <strong>and</strong> overage moisture content (MC) on each<br />
harvest date for Tebonnef voriety rice, EMC based on the doily average ambient air<br />
conditions, <strong>and</strong> the incidence of rain during the 1990 horvest season, (from<br />
Siebenmorgen et al., 1992.)<br />
can reduce milling quality. On the other end of the MC scale, allowing rice to dry<br />
in fields below approximately 14 to 15% greatly increased the risk of milling quality<br />
reduction due to fissures caused by moisture adsorption during periods of rain.<br />
Environmental conditions <strong>and</strong> rice types different from those observed in the<br />
study by Siebenmorgen et al. (1992), could very likely have different HRY responses<br />
to air <strong>and</strong> rain conditions (e.g., air conditions in California often include relative<br />
humidities that are low during the day but high at night, possibly causing conditions<br />
for fissuring due to moisture adsorption to occur). It has also been shown that<br />
varieties vary in their susceptibility to fissuring (Lan <strong>and</strong> Kunze, 1996; Bautista <strong>and</strong><br />
Bekki, 1997). This would suggest that various rice varieties could have different HRY<br />
responses to given environments tliroughout a harvest season.
Rough Ríce Drying <strong>and</strong> Milling Quality 575<br />
R e sp ira tio n E ffects<br />
Like any living organism, rice iespires in the presence of oxygen, The equation describing<br />
this process is (Brooker et al., 1974)<br />
CfiHiaOg + 6O2 ^ 6CO2 + 6H2O + 677.2 Kcal/mole (1)<br />
As equation (1) indicates, carbon dioxide, water, <strong>and</strong> energy are produced by the<br />
oxidiation of carbohydrates. Along with the rice kernel itself, microbes associated with<br />
tlie rice also respire <strong>and</strong> contribute greatly to the overall respiratory activity in a rice<br />
bulk, particularly under high MC, relative humidity, <strong>and</strong> temperature conditions that<br />
promote microbial growth.<br />
There are several deleterious effects of high respiration rates, especially if respiration<br />
is allowed to proceed over extended durations. Kernel discoloration, sometimes<br />
referred to as yellowing or stackburn, is the most commonly recognized negative effect<br />
of advanced respiration in rice <strong>and</strong> typically results from storage at high MC.<br />
Dry matter losses from grain are also incurred, as indicated by equation (1). Drymatter<br />
losses are sometimes reported as a function of storage MC <strong>and</strong> temperature<br />
for grains; an example is that for barley <strong>and</strong> wheat by Burrell (1982). Alternatively, the<br />
allowable storage duration under various grain MCs <strong>and</strong> storage temperatures can be<br />
estimated for maintaining dry-matter losses less than given levels by knowledge of the<br />
respiration rate; such durations are presented for corn in Brooker at al. (1974).<br />
The results of respiration can be observed in several ways. Experimentally, respiration<br />
is often measured by the rate of carbon dioxide <strong>production</strong>. In commercial<br />
practice, high respiration rates are often indicated by high-temperature zones, or<br />
hot spots, in a grain mass. These elevated-temperature regions are typically due to<br />
localized high-MC areas, since the rate of respiration is related exponentially to MC<br />
(see below). Foreign material, such as leaf <strong>and</strong> stalk sections, or weed seed or other<br />
weed plant material, will also respire at high rates due to the typically high MC of<br />
this material. Siebenmorgen et al. (1994) measured the MC of rough rice, as well as<br />
accompanying stalk <strong>and</strong> leaf material, throughout a harvest season. As an example,<br />
Siebenmorgen et al. reported a rice stalk/leaf MC of 66.1% when the rice grain MC<br />
was 19.8%. Certainly, there is considerable merit in adjusting combines properly to<br />
minimize levels of material other than grain <strong>and</strong> in scalping/cleaning rough rice prior<br />
to drying <strong>and</strong> storage to avoid respiration from this undesired material.<br />
F a cto rs A ffectin g R e sp ira tio n<br />
Both the MC <strong>and</strong> temperature o f rice dictate tlie rate at which respiration occurs.<br />
Bailey (1940) reported the rate o f respiration of rough rice over a limited MC range<br />
of 12 to 17%. Dillahunty et al. (2000) measured the respiration rate of rough rice<br />
for both medium-grain (Bengal) <strong>and</strong> long-grain (Cypress) rough rice varieties over a<br />
range of temperatures <strong>and</strong> MCs. Figure 4.3.7 presents Dillahunty et al.’s results as well<br />
as those of Bailey; the respiration rates of both studies were in close agreement. Figure<br />
4.3.7 shows the exponential response of respiration rate to MC. The rate increases<br />
dramatically above a MC of 14%, which indicates why rough rice must be dried to<br />
approximately this MC level quickly after harvest. The figure indicates further that to
576 Produits <strong>and</strong> Product Protossing<br />
Figure 4.3.7. Predicted respiration rale curves as reported by Bailey (1940) <strong>and</strong> for rice<br />
cultivars Cypress <strong>and</strong> Bengal generated from experiments where conditioned moisture<br />
content was varied <strong>and</strong> temperature was maintained at 30°C, (From Dillahunty et al.,<br />
: respixation rates with resultant dry-matter loss over long storage durations»<br />
the MC is typically lowered to 12 to 13%.<br />
Figure 4.3.8 is an indication of the effect that temperature has on respiration rates.<br />
As the temperature at which rough rice is stored increases, respiration rate increases<br />
to a certain point, after which it decreases. The decrease is believed to be due to a<br />
thermal retardation of respiration of the kernel <strong>and</strong> microbes present on the kernels.<br />
Figure 4.3.8 shows that the temperature at which respiration peaks decreases as the<br />
MC increases. These trends were similar in both long- <strong>and</strong> medium-grain varieties.<br />
While beyond the scope of this chapter, the reader is referred to a companion study<br />
(Dillahunty etal., 2001) tliat quantifies tlie effect of exposing rice to high temperatures<br />
for various durations in terms of color change <strong>and</strong> paste viscosity effects.<br />
D R Y IN G R O U G H R IC E<br />
E q u ilib riu m M o istu re C o n ten t<br />
As a hygroscopic material, rice can either gain or lose moisture, depending on the MC<br />
o f the kernel <strong>and</strong> the environment in which it is placed. The MC to which a kernel<br />
will equilibrate in an environment is referred to as the equilibrium moisture content<br />
(EMC). Under this special condition, there is no moisture transfer to or from the<br />
kernel. Although from a practical viewpoint EMC is extremely useful <strong>and</strong> realistic,<br />
true equilibrium is almost unattainable. Siebenmorgen et al. (1990) showed that even<br />
after extended periods of a week under constant conditions, the MC of rough rice was<br />
still changing slightly.<br />
The EMC of a material is determined by the chemical composition of the material.<br />
For a material such as a rice kernel, the kernel EMC is a composite of the EMCs for
Rough <strong>Rice</strong> Drying <strong>and</strong> Milling Quality 577<br />
Figure 4.3.8. Respirationrates for rice cultivars (i/) Bengal <strong>and</strong> (6) Cypress<br />
at different temperatures <strong>and</strong> moisture contents. Eachdata point is the mean of<br />
the measurement of three separate replicates. (FromDillahunty et al., 2000.)<br />
the various components of the kernel: the hull, bran, <strong>and</strong> endosperm. For example,<br />
the endosperm or milled kernel is approximately 80% starch, 6 to 7% protein, 12%<br />
water, <strong>and</strong> 1% fat <strong>and</strong> ash (Luh, 1980); each constituent proportionately determines<br />
the overall EMC of the kernel.<br />
Karon <strong>and</strong> Adams (1949) <strong>and</strong> Fan et al. (2000a) reported the EMCs of various rice<br />
components. Hulls have a lower EMC tlian the bran <strong>and</strong> endosperm comprising tlie<br />
brown rice kernel. Thus for a given environment, rough rice has a lower overall EMC<br />
than brown rice (Lu <strong>and</strong> Siebenmorgen, 1992). In a similar fashion, Kaimn <strong>and</strong> Adams<br />
(1949) reported that bran exhibited a lower EMC than milled rice at 25°C. However,<br />
Lu <strong>and</strong> Siebenmorgen (1992) reported little difference in the EMCs of brown <strong>and</strong><br />
milled rice over a wide range of air conditions. Fan et al. (2000a) also reported that<br />
the average EMC of milled rice was 0.7 to 1.1 percentage points greater than that of<br />
the rough rice from which it was milled.<br />
As illustrated above in the section “Property Characterization,” a rice bulk comprises<br />
kernels of varying MCs <strong>and</strong> sizes. Each kernel will have a composite EMC<br />
determined by its chemical constituency <strong>and</strong> the surrounding environment. Just as<br />
an individual kernel EMC is determined by a composite of its component EMCs,<br />
the overall EMC for a bulk sample is determined by the composite of the kernel<br />
EMCs. For a given environment, each individual kernel will gain or lose moisture<br />
until each kernel’s EMC is reached <strong>and</strong> a buUc average EMC is attained accordingly.<br />
At this condition, the interkernel relative humidity (RH) o f the air is referred to as the
578 Products <strong>and</strong> Product Processing<br />
equilibrium relative humidity (ERH). This term, expressed in decimal form, is also<br />
referred to in some technical fields as the water activity.<br />
EMC data for grains are given in ASAE St<strong>and</strong>ard D245.5 (ASAE, 1997a). Equations<br />
relating tlie ERH <strong>and</strong> temperature to the EMC for rice are also given in this st<strong>and</strong>ard;<br />
two of the more common equations used for rice are the Modified Henderson<br />
<strong>and</strong> Modified Chung-Pfost equations. Each equation consists of statistical parameters<br />
specific for a given grain. Table 4.3.1 provides a tabulation of EMCs for various air<br />
conditions using the modified Chung-Pfost equation. Fan et al. (2000a) measured<br />
EMCs of long- <strong>and</strong> medium-grain varieties <strong>and</strong> found that the EMCs measured were<br />
0.2 to 0.8 percentage points higher than those predicted by the Chung-Pfost equation.<br />
Fan et al. also showed that for RHs below 40% there was little-to-no varietal difference<br />
in EMC values. However, for RHs over 40%, EMCs of medium-grain Bengal were 0.3<br />
to 1.3 percentage points higher than those for long-grain Kaybonnet <strong>and</strong> 0.1 to 1.0<br />
percentage points higher than long-grain Cypress. Fan speculated that these varietal<br />
differences could be due to a lower weight percentage of hull with the Bengal variety.<br />
Another aspect should be noted in regard to potential differences in MC between<br />
that predicted by either EMC equation mentioned above <strong>and</strong> that actually measured.<br />
The equations may have been developed based on grain attaining equilibrium<br />
through either drying or adsorption, whereas the grain in question may have attained<br />
equilibrium in the opposite fashion. The EMC value reached if a grain attains equilibrium<br />
by drying is typically higher than if equilibrated in the same air conditions, but<br />
reaching EMC through adsorption of water. The difference in these two EMC levels<br />
is referred to as the hysteresis effect Breese (1955) showed that the hysteresis effect in<br />
rice was greater than 1 percentage point in MC across the RH range of 20 to 80%,<br />
but exceeded 1.5 percentage points when RHs were between 50 <strong>and</strong> 70%. Kachru <strong>and</strong><br />
Mathes (1976) also confirmed the existence of the hysteresis effect in rough rice. They<br />
showed that the hysteresis effect tended to disappear after rice samples were subjected<br />
to three or four sorption cycles.<br />
Banaszek <strong>and</strong> Siebenmorgen (1990) reported an extension of the hysteresis effect.<br />
They found that when rewetting rough rice with initial MCs ranging from 9 to 15%<br />
in high RH air, the lower the initial MC, the lower the adsorption EMC (i.e., the EMC<br />
attained through adsorption varied directly with initial MC). Thus the amount of<br />
hysteresis that could be experienced would be determined by the extent of rewetting<br />
or MC change that the rice incurred in reaching the adsorption EMC.<br />
Although EMC is important in determining whether rice will gain or lose moisture<br />
under given conditions, it is also an important parameter in predicting the drying<br />
rate of rice. EMC is a parameter in the Page equation (ASAE, 1997b) that is used to<br />
describe the drying behavior of grains:<br />
M C (i) - EMC<br />
IMC - EMC = exp(—/ci") (2)<br />
where M C {i) is the MC at any drying duration t, EMC is the equilibrium MC of the<br />
drying air, IMC is the initial MC of the rice, t is the drying duration, <strong>and</strong> k <strong>and</strong> n are<br />
constants. The ratio representing the left side of equation (2) is often referred to as the<br />
moisture ratio. The moisture ratio varies from 1 at the initiation of drying to zero at the<br />
end of drying when the rice has reached EMC. The moisture ratio can be interpreted as
580 Products <strong>and</strong> Product Processing<br />
the amount of drying left to do divided by the total amount of drying; or alternatively,<br />
the percentage of drying remaining to be done after a given duration.<br />
As can be seen by equation (2) <strong>and</strong> Figure 4.3.9, rice drying proceeds m an<br />
exponential fashion (i.e,, the rate of drying is great at first but becomes slower <strong>and</strong><br />
slower as drying proceeds <strong>and</strong> the MC of the rice approaches EMC). Drying rates<br />
are typically measured using small samples that are spread into thin layers, which,<br />
according to ASAE St<strong>and</strong>ard S448 (ASAE, 1997b) is “a layer of material exposecpully<br />
to an airstream during drying. The depth (thickness) of the layer should by uniform<br />
<strong>and</strong> should not exceed three layers of particles.”*This is done to prevent gradients in<br />
MC from the bottom of the layer to the top at any given time during drying. Several<br />
researchers have quantified drying rates for rice (Agrawal <strong>and</strong> Singh, 1977; Banaszek<br />
<strong>and</strong> Siebenmorgen, 1993) by statistically determining the constants k <strong>and</strong> n from<br />
equation (2) for MC versus drying duration data, such as that shown in Figure 4.3.9.<br />
The drying rate is very important since it allows quantifying the durations needed<br />
for drying rice under various air conditions. However, with rice, the ultimate success<br />
of drying is judged by maintaining high HRYs. Extreme drying rates for extended<br />
durations can lead to kernel fissures, which in turn will lower HRYs. Thus rice drying<br />
systems <strong>and</strong> protocols for drying rice must account for this fact <strong>and</strong> dry rice slowly if<br />
in a continuous drying mode, or in multiple high-drying-rate passes with sufficient<br />
tempering durations between passes, if drying in an intermittent procedure. Further<br />
discussion relating drying rate to HRY reduction is given below.<br />
R e la tin g D rying C o n d itio n s to H e a d R ice Y ield<br />
Drier operators generally know that to maintain high milling quality, more “points of<br />
MC” can be removed from high-MC rice than low-MC rice in a given pass through a<br />
drier. The drying protocol specifying the number of points of MC to be removed per<br />
pass for various inlet MCs varies with the company <strong>and</strong> the drier design. However, a<br />
general procedure might include removing no more than three to four points of MC<br />
4 0 60 80<br />
Drying Duration (min)<br />
120<br />
Figure 4.3.9.<br />
variety Cypress.<br />
Thin layer dfying curt/es for three drying oir conditions for rice
Rough <strong>Rice</strong> Drying <strong>and</strong> Milling Quality 581<br />
per pass for high-MC rice (e.g., above 18% MC) <strong>and</strong> two to three percentage points of<br />
MC per pass for lower-MC rice (
582 Products <strong>and</strong> Product Processing<br />
condition with high air temperature <strong>and</strong> low RH, the HRY decreased rapidly e'/en in<br />
the early stages of drying. For example, drying for 30 min under condition C resulted<br />
in approximately 10 percentage points of HRY reduction. It is to be noted that the<br />
experimental procedure for tliis study consisted of cooling the samples immediately<br />
after removing from the drier <strong>and</strong> thus represents a severe treatment (i.e., no tempering<br />
of the rice was provided before cooling). This is addressed in more detail at the<br />
end of this section.<br />
Since FIRY did not change significantly with drying duration under air condition<br />
A, the following discussion focuses on the HRY reductions associated with drying<br />
air conditions B <strong>and</strong> C. Figure 4.3.11 illustrates HRY data of the three varieties, each<br />
harvested at a midrange MC (Bengal: 22.5%, Cypress: 19.8%,Kaybonnet: 19.1%), <strong>and</strong><br />
dried under air conditions B <strong>and</strong> C. Drying under air condition B had little effect on<br />
the HRY of the two long-grains. Cypress <strong>and</strong> Kaybonnet (Figure 4.3.11«). However,<br />
medium-grain Bengal showed a pronounced decrease in HRY when it was dried under<br />
the same condition for more than 40 min. Under condition C, Cypress <strong>and</strong> Kaybonnet<br />
exhibited no HRY reduction for drying durations of less than 30 <strong>and</strong> 10 min, respectively<br />
(Figure 4.3.11 b)’, after that, a significant HRY reduction was observed. However,<br />
Bengal“showed HRY reduction after a very short drying duration. In general, Bengal<br />
showed more HRY reduction than did Cypress or Kaybonnet for a given drying duration<br />
(Figure 4.3.11 fe). The HRY responses of the three varieties shown in Figure 4.3.11<br />
are thought to be due primarily to different rice types (Bengal as a medium-grain <strong>and</strong><br />
Cypress <strong>and</strong> Kaybonnet as long-grains). Different rice varieties are usually associated<br />
with different kernel lengths, widths, <strong>and</strong> thicknesses. Medium-grain Bengal, with<br />
a thick <strong>and</strong> wide kernel shape, is more vulnerable to fissure formation than slender<br />
kernels from long-grains Cypress <strong>and</strong> Kaybonnet.<br />
Figure 4.3.12 shows the effect of haiwest MC on HRY of three Bengal rice lots<br />
(harvest MCs of 17.4%, 22.5%, <strong>and</strong> 25.9%) dried under conditions B <strong>and</strong> C. The<br />
three rice lots showed a similar decrease in HRY after being dried for over 45 min<br />
under drying air condition B, even though they were different in harvest MC (Figure<br />
4.3.12«). Unlike under drying air condition B, harvest MC had a great effect on HRY<br />
with drying air condition C (Figure 4.3.12Î?). For rice lots with harvest MCs of 17,4%<br />
<strong>and</strong> 22.5%, HRY decreased significantly after drying for 10 min (Figure 4,3.12Î?). The<br />
rice with higli harvest MC (25.9%) could be dried for a longer duration (up to 20<br />
min) at condition C without affecting the HRY. For a given drying duration, a lower<br />
harvest MC resulted in more HRY reduction (e.g., for Bengal with harvest MCs of<br />
25.9%, 22.5%, <strong>and</strong> 17.4%, the resulting HRY after 30 min of drying under condition<br />
C was 55.6%, 52.3%, <strong>and</strong> 38.5%, respectively) (Figure 4.3,12fo).<br />
Analogous to Figure 4,3.12, Figure 4.3.13 shows the HRY values of three Cypress<br />
rice lots harvested at different MC values <strong>and</strong> dried under condition B (a) <strong>and</strong> condition<br />
C (h). An observation from the Cypress samples was tliat the higher the harvest<br />
MC, the lower the overall level of HRY, as can be seen in both Figures 4.3.13a <strong>and</strong><br />
k The decreased HRY as harvest MC increased may be attributed to the increased<br />
number of weak, immature kernels often present with higher harvest MCs. When<br />
Cypress was dried under condition B, the HRY for a given rice lot showed little effect<br />
due to drying duration (Figure 4.3.13a). Under drying condition C, the Cypress rice<br />
exhibited a significant FIRY reduction after a certain period of drying (Figure 4.3.131?),
Rough <strong>Rice</strong> Drying <strong>and</strong> Milling Quality 583<br />
0 20 40 60 80 100 120<br />
Drying duration, min<br />
Figure 4.3.11. Head rice yield of three rice varieties harvested at<br />
the moisture contents (HMQ indicated vs. drying duration when dried<br />
under air conditions B (51,7“C, 2 5 % RH) (fl) <strong>and</strong> C [60,0% 17%<br />
RH) [b]. Data points represent the means of two drying replicates,<br />
(From Fan etaL, 2000b.) ■<br />
(b)<br />
It appeared that the drying duration within which HRY was not affected increased as<br />
harvest MC increased.<br />
R e la tin g M o istu re C o n te n t R ed u ctio n to H e a d R ice Y ield<br />
Figure 4.3.14 shows the HRY of Bengal with indicated harvest MCs in relation to<br />
the MC of rough rice achieved after drying for different durations. Drying of Bengal
584 Products gnd Product Processing<br />
Drying duration, min<br />
Figuro 4.3.12. Effect of harvest moisture content (HWQ on heod<br />
rice yield of Bengal when dried under air conditions B (51.7% 25%<br />
RH) (a) <strong>and</strong> C (6 0.0 X 17% RH} (6). Data points represent the<br />
meons of two drying replicates. (From Fan et al., 2000b'.)<br />
{&)<br />
rice under condition B from its harvest MC of 25.9% to a MC of around 22% did<br />
not influence the resulting HRY (Figure 4.3.14a); howevecj further drying to a lower<br />
MC caused marked reduction in HRY. Similar trends were observed when drying<br />
Bengal rice lots harvested at MC values of 22,5% <strong>and</strong> 17.4% under drying condition<br />
B (Figure 4.3.14«). For Bengal at drying condition C (Figure 4.3.14&), the amount<br />
of moisture removed without affecting HRY was much less than at drying condition<br />
B (Figure-4.3.14a), In general, it appears that a certain duration exists at the early<br />
drying stages during which the MC of the rough rice decreased, but the HRY was not<br />
reduced substantially. Figure,4.3.14 indicates that the amount of moisture that could<br />
be removed before a HRY reduction occurred increased as the harvest MC of the rice<br />
increased.
Rough <strong>Rice</strong> Drying <strong>and</strong> Milling Quality 585<br />
(a)<br />
Figure 4.3.13. Effect of harvest moisture content (HMC) on head<br />
rice yield of Cypress when dried under oir conditions B (51,7“C,<br />
2 5 % RH) (flf) <strong>and</strong> C (60.0“C, 17% RH} (¿). Data points represent<br />
the means of two drying replicates. (From Fan et ol., 2000b.)<br />
Figure 4.3.15 shows trends analogous to Figure 4.3.14 between HRY <strong>and</strong> MC of<br />
long-grain Cypress rough rice achieved by drying the indicated harvest MC lots for<br />
various drying durations under drying air conditions B <strong>and</strong> C. Drying tlie Cypress<br />
rice lots under condition B resulted in little change in HRY, although the rice MC<br />
was gradually decreased from the harvest MC as drying duration increased (Figure<br />
4.3.15ii). Similar to Bengal, Cypress dried at condition C showed a marked HRY<br />
reduction after the early stages of drying (Figure 4.3.15fo). The results in Figure 4.3.15<br />
for Cypress were similar to those for Bengal in Figure 4.3.14, in that the MC levels<br />
achieved in a drying duration had a considerable effect on HRY. Additionally, the<br />
number o f points of MC that could be removed without HRY reduction increased as<br />
harvest MC increased, particularly under condition C.<br />
Figure 4.3.16 shows the percentage points of MC removed before HRY reduction<br />
occurred as a function of harvest MC. Figure 4.3.16 summarizes the data above in
586 Products <strong>and</strong> Product Processing<br />
17.4% HMC<br />
70<br />
25.9% HMC<br />
22.5% HMC<br />
-- 60<br />
-■ 50<br />
40<br />
■■30<br />
30 25 20 15 10<br />
Moisture content, % w.b.<br />
20<br />
25 20 15 10 5<br />
Moisture content, % w.b.<br />
(&)<br />
Figure 4.3.14. Head rice yield of Bengal vs. the moisture content<br />
Qchieved by drying the indicated harvest moisture content (HWC) lots for<br />
various durations under air conditions B (51.7°Q 2 5 % RH) (o) <strong>and</strong> C<br />
(60.0% 17% RH) (/)). Data points represent the means of two drying<br />
replicates. (From Fan et al., 2000b.)<br />
tlie previous figures, indicating that the amount of MC that could be removed prior<br />
to HRY reduction increased as the harvest MC of the rice increased. It should be<br />
noted the percentage points of MC were taken qualitatively from the above-discussed<br />
figures by visually identifying the turning points in the HRY reduction curves, <strong>and</strong><br />
no quantitative statistical tests were performed to identify tlie percentage points of<br />
MC removed before HRY reduction occurred. Wlren the drying air condition was<br />
severe (e.g., condition C), tlie amount of moisture that could be removed before HRY<br />
reduction occurred decreased relative to the less severe condition (condition B). For<br />
a given drying air condition, long-grain Cypress, a longer <strong>and</strong> more slender kernel
Rough Ríce Drying <strong>and</strong> Milling Qualify 587<br />
(a)<br />
2<br />
0)<br />
_o<br />
'C<br />
■o (0<br />
(6)<br />
Figure 4.3.15. Head rice yield of Cypress vs. the moisture content<br />
achieved by drying the indicated harvest moisture content (HMC) lots<br />
for various durations under air conditions B (51.7°C, 2 5 % RH) (o) ord<br />
C (60.0% 17% RH) [b). Data points represent the means of two<br />
drying replicates. {From Fan et al., 2000b.)<br />
variety, tolerated more percentage points of MC removal than medium-grain Bengal,<br />
a shorter <strong>and</strong> thicker kernel variety, without HRY reduction.<br />
It is to be noted that the drying procedure used in Fan et al.’s study did not utilize<br />
tempering prior to cooling the rice. Subsequent research by Cnossen <strong>and</strong> Siebenmorgen<br />
(2000) has shown that tempering at the drying air temperature after a drying duration<br />
<strong>and</strong> before cooling substantially prevents HRY reduction. Cnossen <strong>and</strong> Siebenmorgen<br />
postulate the reason for this through a hypothesis involving material property
588 Products <strong>and</strong> Product Processing<br />
Harvest moisture content, %<br />
Figure 4.3.16, Percentage points of moisture content (MC) removed before<br />
head rice yield reduction occurred in relation to harvest moisture content. (From<br />
Fan et al., 2000b.}<br />
behavior; tliis ongoing work is beyond the scope of this book, but is addressed in<br />
summary at the end of this chapter.<br />
D rying S y stem s<br />
Rough rice drying systems in the United States can be broadly categorized into either<br />
commercial or on-farm systems. In both, rice is dried by passing either ambient or<br />
heated air through tlie rice bulk. The sensible heat of the air evaporates water from<br />
the rice; the evaporated water is carried out of the grain bulk by the airstream as<br />
water vapor. Prior to entering the grain, air is typically heated <strong>and</strong> the RH is lowered<br />
correspondingly. This increases the drying capacity of the air (i.e., the amount of water<br />
vapor tlaat can be transferred to a unit of air before being saturated). This is why most<br />
drying systems have some form of burner system as part of the fan <strong>and</strong> ducting system.<br />
A more complete treatise of the psychrometric processes involved in grain drying is<br />
given in Brooker et al. (1974) <strong>and</strong> Henderson <strong>and</strong> Perry (1976),<br />
As discussed above, there are limits to the air temperature levels <strong>and</strong> drying<br />
durations that grain driers can use without incurring kernel quality reduction, particularly<br />
with rice. Excessively high temperatures can result in stress cracking of kernels,<br />
which typically results in lowered HRYs. This situation can exist in either on-farm or<br />
commercial systems, but due to the throughput speed with which commercial driers<br />
are often required to operate, the potential for damage in commercial driers can be<br />
greater.<br />
Commercial systems are inherently larger than on-farm systems <strong>and</strong> have far<br />
greater drying capacity. Most rice in the United States is dried in commercial facilities.
Rough Ríce Drying <strong>and</strong> Milling Quality 589<br />
Figure 4.3.17.<br />
Cross-flow drier illustrotion.<br />
There are many different kinds <strong>and</strong> configurations o f commercial rice driers. The predominant<br />
rough rice drier currently in use consists o f a cross-flow design, as illustrated<br />
in Figure 4.3.17 <strong>and</strong> diagrammed in Figure 4.3.18. In this design, rice is continuously<br />
top-loaded into a column that is typically 30.5 to 38 cm (12 to 15 in.) thick; the height<br />
<strong>and</strong> width o f the colum n depends on the manufacturer, but heights o f 18 to 24 m (60<br />
to 80 ft) <strong>and</strong> widths o f 6 to 9 m (20 to 30 ft) are not uncom m on. Feed rolls at the<br />
bottom o f the drier are used to establish tlie flow rate <strong>and</strong> thus the residence time o f<br />
the rice in the drying column. The flow rate o f the rice is often adjusted to maintain<br />
average grain temperatures exiting the bottom o f the drier below targeted levels, often<br />
in the range o f 35 to 38°C (95 to 100"F). The rice temperature in the colum n is also<br />
determined by the plenum air temperature <strong>and</strong>, to a certain extent, the incom ing M C<br />
o f the rice. Thus the feed rate, as dictated by the outlet rice temperature, accounts in<br />
a general sense, for drying air <strong>and</strong> inlet rice conditions.
590 Products <strong>and</strong> Product Processing<br />
38 cm (15”)<br />
¿u m<br />
Tlow<br />
Exhaust<br />
Air ^<br />
j;urn<br />
F low<br />
Screens<br />
[T,urn<br />
^low<br />
Figure 4.3.18.<br />
Cross-flow drier schenratic.<br />
O ther types <strong>and</strong> configurations o f com mercial driers are in use to dry rough<br />
rice <strong>and</strong> are described by Kunze <strong>and</strong> Calderwood (1980). In most commercial drier<br />
protocols, rice is dried in multiple passes or traverses o f the drier. This is done to<br />
prevent excessively large MG gradients from forming in kernels that lead to kernel<br />
Assuring. As an aid to help prevent high rice temperatures from forming along the<br />
inlet air plenum side o f drying columns, turn flows or grain exchanges are often<br />
installed. These are mechanical devices used to transfer rice from one side o f the<br />
drying column thickness to the other. Turn flows, when used, are spaced along tlie<br />
drier column height approximately every 3 to 6 m (10 to 20 ft).<br />
Between drying passes, the rice is held in bins for a certain period o f time to<br />
allow M C gradients within kernels created during the drying process to subside.<br />
This holding process, referred to as tempering, decreases M C gradients by allowing<br />
moisture to migrate from the core to the outer layers o f the kernel. Moisture migration<br />
toward the kernel surface during tempering also allows moisture to be more readily<br />
removed, thus improving energy utilization in subsequent drying passes.<br />
There are also various configurations o f on-farm drying systems. The predominant<br />
configuration is the in-hin, batch system; a typical system is shown in Figure<br />
4.3.19. In these systems, rice is dried in deep beds, typically greater than 0.6 to 1 m<br />
(2 to 3 ft) in depth. The M C o f tlie rice <strong>and</strong> the airflow capacity o f the fan dictate the<br />
allowable bed depth. Gardisser (2000) presents practical considerations for operating<br />
such systems. Variations o f the batch design include systems in which rice is augured<br />
continuously into the bin from the top <strong>and</strong> out o f the bin by a sweep auger on the<br />
bottom o f tlie bin.<br />
In such bin systems, passing air through the bed in a manner similar to that<br />
described with commercial systems dries the rice. In on-farm systems, the airflow<br />
rate, expressed in terms o f mVhr (cfm ) o f airflow per<br />
(ft^) of bed area, is much less
Rough Rite Drying <strong>and</strong> Milling Quality 591<br />
STIRRING<br />
DEVICE<br />
Figure 4.3.19.<br />
In-bin, on-farm drying system.<br />
than com mercial systems due to smaller fan capacities <strong>and</strong> greater airflow resistance<br />
resulting from the deeper beds. Drying fronts are created at the inlet air side o f the bed<br />
(typically, the bottom of the bin) <strong>and</strong> progress through the bed as drying proceeds.<br />
Caution must be taken not to fill the bin with too great a depth o f high-M C rice for<br />
a given fan capacity. I f this is done, possible heating due to respiration <strong>and</strong> resultant<br />
discoloration o f the rice in the upper layers o f the bed can occur. Once the drying<br />
front has moved through the bed depth <strong>and</strong> the rice has been dried to approximately<br />
13 to 15% M C, the rice is typically transferred to a storage bin, where it is slowly dried<br />
further to 12 to 13% M C <strong>and</strong> aerated periodically to cool the rice.<br />
SUMMARY AND ONGOING RESEARCH<br />
The intended purpose o f tliis chapter was to present an overview o f rice drymg <strong>and</strong><br />
the closely associated subject o f milling quality. The fundamental science o f drying,<br />
involving both the psychrometrics o f drying air <strong>and</strong> the phenom ena o f moisture<br />
migration in the rice kernel, are only summarized; more in-depth treatm ent o f these<br />
subjects is cited in other books, covering the more general area o f grain drying.<br />
Specific factors that affect rice kernel quality, during both maturation <strong>and</strong> drying,<br />
are discussed in greater detail. Systems currently used in the industry for drying lice<br />
are described briefly.<br />
Ongoing research at the time o f this writing is focusing on kernel material properties<br />
that ultimately affect the drying rate o f rice kernels <strong>and</strong>, as important, the initiation<br />
<strong>and</strong> propagation o f fissures. More specifically, the glass transition temperature o f<br />
rice kernels has been shown (Perdón et al„ 2000) to exist at levels that could be reached<br />
during com mercial drying. W hen materials exist at temperatures <strong>and</strong> MCs below the<br />
glass transition temperature, they are said to be in the glassy state, <strong>and</strong> above this<br />
temperature, in the rubbery state (Slade <strong>and</strong> Levine, 1995). Therm al <strong>and</strong> hygroscopic<br />
material properties in the glassy state are tremendously different in magnitude from<br />
those in the rubbery state. Work by Cnossen <strong>and</strong> Siebenmorgen (2000) illustrated that<br />
if kernels were forced to undergo a rapid change from the rubbery to the glassy region<br />
while M C gradients existed within the kernels, drastic Assuring <strong>and</strong> HRY reductions
592 Products <strong>and</strong> Product Processing<br />
would be incurred. This work supports a hypothesis that has been generated to explain<br />
the form ation o f fissures during drying based on glass transition property changes.<br />
Further work in quantifying material properties, drying rates, <strong>and</strong> fissure behavior is<br />
ongoing in an effort to validate this hypothesis more fully.<br />
Additional current work in underst<strong>and</strong>ing the effects o f environmental factors<br />
during rice kernel physiologic development, specifically grain filling, is also proceeding.<br />
There are preliminary indications that high nighttime air temperatures during<br />
certain stages o f rice kernel development can produce rice with reduced HRY values.<br />
This particular phenomenon is being focused on to elucidate not only an explanation<br />
o f reduced milling quality, but also an explanation for variability in end-use<br />
processing performance, that is sometimes experienced in supposedly similar rice.<br />
All o f tills research is aimed at better underst<strong>and</strong>ing <strong>and</strong> ultimately controlling the<br />
quality o f rice.<br />
REFERENCES<br />
Agrawal, Y. C., <strong>and</strong> R. D, Singh. 1977. Thin Layer Drying Studies for Short Grain <strong>Rice</strong>,<br />
ASAE Paper 77-3531. American Society of Agricultural Engineers, St. Joseph, MI.<br />
Andrews, S. B., X J. Siebenmorgen, <strong>and</strong> A. Mauroraoustakos. 1992. Evaluation o f the<br />
McGill No. 2 rice miller. Cereal Chem. 6 9 (l):3 5 -4 3 .<br />
ASAE. 1997a. Moisture Relationships of Plant-Based Agricultual Products. ASAE St<strong>and</strong>ard<br />
D 245.5. American Society o f Agricultural Engineers, St. Joseph, ML<br />
ASAE. 1997b. Thin-Layer Drying of Grains <strong>and</strong> Crops. ASAE St<strong>and</strong>ard S448. American<br />
Society of Agricultural Enginneers, St, Joseph, MI.<br />
Bailey, C. G, 1940. The h<strong>and</strong>ling <strong>and</strong> storage o f cereal grains <strong>and</strong> flaxseed. Plant<br />
Physiol 15:257-274.<br />
Banaszek, M. M ., <strong>and</strong> T. J. Siebenmorgen. 1990, Adsorption equilibrium moisture<br />
contents o f long-grain rough rice. Trans. ASAE 3 3 (l):2 4 7 -2 5 2 .<br />
Banaszek, M. M ., <strong>and</strong> X J. Siebenmorgen. 1993. Individual rice kernel drying curves.<br />
Trans. ASAE 36(2):521~528.<br />
Bautista, R. C., <strong>and</strong> E. Bekld, 1997. Grain fissures in rough rice drying: differences in<br />
Assuring behavior o f selected japónica <strong>and</strong> indica varieties. Jpn. Soc. Agrie, Mach.<br />
5O (4):97-108.<br />
Bautista, R. C., <strong>and</strong> X J. Siebenmorgen. 1999. Characteristics of <strong>Rice</strong> Individual Kernel<br />
Moisture Content <strong>and</strong> Size Distributions at Harvest <strong>and</strong> during Drying. ASAE<br />
Paper 996053. American Society o f Agricultural Engineers, St. Joseph, MI,<br />
Bautista, R. C., <strong>and</strong> X J. Siebenmorgen. 2000, <strong>Rice</strong> Icernel properties affecting milling<br />
quality at harvest. In R. Norman <strong>and</strong> J. F. Meullenet (eds.), B. R. Wells Research<br />
Studies. University o f Arkansas Agricultural Experiment Station, Fayetteville, AR.<br />
Bennett, K. E., X J. Siebenmorgen, <strong>and</strong> A. Mauromoustakos. 1993. Effects o f McGill<br />
No. 2 miller settings on surface fat concentration o f head rice. Cereal Chem.<br />
70(6):734-739.<br />
Breese, M. H. 1955. Hysteresis in the hygroscopic equilibria o f rough rice at 25“C.<br />
Cereal Chem. 32(6):481-487.<br />
Brooker, D. B., F. W. Bakker-Arkema, <strong>and</strong> C. W. Hall. 1974. Drying Cereal Grains. AVI,<br />
Westport, CT.
Rough Ríce Drying <strong>and</strong> Milling Quality 593<br />
Burrell, N, J. 1982. Refrigeration. In C. M. Christensen (ed.), Storage of Cereal Grains<br />
<strong>and</strong> Their Products. American Association o f Cereal Chemists, S t Paul, M N, pp.<br />
407-435.<br />
C<strong>and</strong>óle, B., T. J. Siebenmorgen, K Lee, <strong>and</strong> R. Cartwright. 2000. Effect o f rice blast<br />
<strong>and</strong> sheath blight on the physical properties o f selected rice cultivars. Cereal<br />
Chem. 77{5);535-540.<br />
Chau, N. N„ <strong>and</strong> O. R. Kunze. 1982. Moisture content variation among harvested rice<br />
■grains. Trans. ASAE 25 (4): 1037-1040.<br />
Cnossen, A. G., <strong>and</strong> T. J. Siebenmorgen. 2000. The glass transition temperature concept<br />
in rice drying <strong>and</strong> tempering: effect on milling quality. Trans. ASAE 43(6):<br />
1661-1667.<br />
Dillahunty, A. L„ T. J. Siebenmorgen, R. W. Buescher, D. E. <strong>Smith</strong>, <strong>and</strong> A. Mauro-<br />
moustakos. 2000. Effect o f moisture content <strong>and</strong> temperature on the respiration<br />
rate of rice. Cereal Chem. 77(5) :5 4 1-543,<br />
Dillahunty, A. L., T. J. Siebenmorgen, <strong>and</strong> A. Mauromoustakos. (2001). Effect o f<br />
temperature, exposure duration, <strong>and</strong> moisture content on color <strong>and</strong> viscosity of<br />
rice. Cereal Chem. 78(5):559-563.<br />
Fan, )., T. J. Siebenmorgen, <strong>and</strong> B. P. Marks. 2000a, Effects o f variety <strong>and</strong> harvest<br />
moisture content on the equilibrium moisture contents o f rice, Appl. Eng. Agrie.<br />
16(3):245-251.<br />
Fan, J., T. J. Siebenmorgen, <strong>and</strong> W. Yang. 2000b. A study o f head rice yield reduction o f<br />
long- <strong>and</strong> medium-grain rice varieties in relation to various harvest <strong>and</strong> drying<br />
conditions. Trans. ASAE 43(6); 1709-1714.<br />
Fryar, E. O,, L. O. Parsch, S. H. Holder, <strong>and</strong> N. P. Tugwell. 1986. The econom ics o f<br />
controlling peck in Arkansas rice. Ark. Farm Res. 3 5 (3 ):7.<br />
Gardisser, D. 2000. <strong>Rice</strong> drying on the farm. In <strong>Rice</strong> Production H<strong>and</strong>book. M P192.<br />
Cooperative Extension Service, University o f Arkansas, Little Rock, AR.<br />
Henderson, S. M., <strong>and</strong> R. L. Perry. 1976. Agricultural Process Engineering, 3rd ed. AVI,<br />
Westport, CT.<br />
Holloway, G. E., T. J. Siebenmorgen, P. A. Counce, <strong>and</strong> R. Lu. 1995. Causes o f m ultimodal<br />
moisture content frequency distributions among rice kernels. Appl. Eng.<br />
Agrie. 11(4);561-565.<br />
Kachru, R. P., <strong>and</strong> R, K. Mathes. 1976. The behavior o f rough rice in sorption. /. Agrie.<br />
Eng. Res. 21(4):405-416.<br />
Karon, M . L., <strong>and</strong> M. E. Adams. 1949. Hygroscopic equilibrium o f rice <strong>and</strong> rice<br />
fractions. Cereal Chem. 26(1):1~12,<br />
Kocher, M, F., T, J. Siebenmorgen, R. J. Norm an, <strong>and</strong> B, R. Wells. 1990. <strong>Rice</strong> kernel<br />
moisture content variation at harvest. Trans. ASAE 33(2):541-548.<br />
Kunze, 0 . R. 1977. Moisture adsorption influence on rice. J. FoodProc. Eng. 1(1977);<br />
167-181,<br />
Kunze, O. R., <strong>and</strong> D. L. Calderwood. 1980. Systems for drying o f rice. In C, W. Hall<br />
(ed.), Drying <strong>and</strong> Storage of Agricultural Crops, pp. 209-233. AVI, Westport, CT.<br />
Kunze, O. R., <strong>and</strong> C, W. Hall. 1967. Moisture adsorption characteristics o f brown rice.<br />
TYans. ASAE 7 (6 ):717-723.<br />
Kunze, O. R., <strong>and</strong> B. Sarwar. 1987. Fissure Response from Moisture Adsorption in <strong>Rice</strong><br />
Varieties. ASAE Paper 87-6561. American Society o f Agricultural Engineers, St.<br />
Joseph, ML
594 Products <strong>and</strong> Product Procossing<br />
Lan, Y., <strong>and</strong> O. R. Kunze. 1996. Fissure resistance of rice varieties. Appl Eng. Agrie.<br />
12(3):365-368.<br />
Lu, R., <strong>and</strong> T. J. Siebenmorgen. 1992. Moisture diffusivity o f long-grain rice components.<br />
Trans. ASAE 35(6); 1955-1961.<br />
Luh, B. S. 1980. <strong>Rice</strong>: Production <strong>and</strong> Utilization. AVI, Westport, CT.<br />
Perdón, A. A., T, J. Siebenmorgen, <strong>and</strong> A. Mauromoustalcos. 2000. Glassy state transition<br />
<strong>and</strong> rice drying: development o f a brown rice state diagram. Cereal Chem.<br />
77(6):708-713.<br />
Perdón, A. A ., T. J. Siebenmorgen, A. Mauromoustakos, V. K. Griffin, <strong>and</strong> E. R. Johnson.<br />
2001. Degree o f milling effects on rice pasting properties. Cereal Chem.<br />
78(2):205~209.<br />
Reid, J. D., T. J. Siebenmorgen, <strong>and</strong> A. Mauromoustakos. 1998. Factors affecting the<br />
head rice yield versus degree o f milling relationship. Cereal Chem. 75(5):738-741.<br />
Siebenmorgen, T. J. 1994. Role o f moisture content in affecting head rice yield. In<br />
W. E. Marshall <strong>and</strong> J. I, Wadsworth (eds.), <strong>Rice</strong> Science <strong>and</strong> Technology. Marcel<br />
Delcker, New York, pp. 341-380.<br />
Siebenmorgen, T. J, 1998. Influence .of postharvest processing on rice quality. Cereal<br />
Foods World 43(4):200-202.<br />
Siebenmorgen, T. J., <strong>and</strong> V. K. Jindal. 1986. Effects o f moisture adsorption on the head<br />
rice yields o f long-grain rough rice. Trans. ASAE 29(6):1767-1771.<br />
Siebenmorgen, T. J., M. M. Banaszek, <strong>and</strong>M . F. Kocher. 1990, Kernel moisture content<br />
variation in equilibrated rice samples. Trans. ASAE 33(6): 1979-1983.<br />
Siebenmorgen, T. J., P. A. Counce, R. Lu, <strong>and</strong> M. F. Kocher. 1992. Correlation o f head<br />
rice yield with individual kernel moisture content distribution at harvest. Trans.<br />
A SA £35(6):1879-1884.<br />
Siebenmorgen, T. J., S. B. Andrews, <strong>and</strong> P. A. Counce. 1994. Relationship o f the height<br />
rice is cut to harvesting test parameters. Trans. ASAE 3 7 (l):6 7 -6 9 .<br />
Siebenmorgen, T. J., A. A. Perdón, X. Chen, <strong>and</strong> A. Mauromoustakos. 1997. Relating<br />
rice milling quality changes during adsorption to individual kernel moisture<br />
content distribution. Cereal Chem. 75(1):129-136.<br />
Slade, L , <strong>and</strong> H. Levine. 1995. Glass transitions <strong>and</strong> w ater-food structure interactions.<br />
Adv. Pood Nutr. Res. 38:103-269.<br />
Stahel, G. 1935. Brealdng of rice in milling in relation to the condition o f the paddy.<br />
Trop, Agrie. 12:225-261.<br />
Sun, H., <strong>and</strong> T. J. Siebenmorgen. 1993, Milling characteristics of various rough rice<br />
kernel thickness fractions. Cereal Chem. 70(6):727-733,<br />
USDA. 1995. United States St<strong>and</strong>ards for Milled <strong>Rice</strong>, Agricultural Marketing Service,<br />
U.S. Department o f Agriculture. Washington, DC.<br />
Wang, C. Y., <strong>and</strong> B. S. Luh. 1991. Harvest, drying, <strong>and</strong> storage of rough rice. In B. S.<br />
Luh (ed.), <strong>Rice</strong>, Vol. 1, Production, 2nd ed. Van Nostr<strong>and</strong> Reinhold, New York,<br />
pp. 311-346.<br />
Yoshida, S. 1981. Fundamentals of <strong>Rice</strong> Crop Science, International <strong>Rice</strong> Research Institute,<br />
Manila, The Philippines,<br />
^
Harold E. Bockelmon <strong>and</strong><br />
Darrell (!A. Wesonberg<br />
USDA-ARS<br />
Aberdeen, Idaho<br />
INTRODUCTION<br />
U.S. NATIONAL PLANT GERMPLASM SYSTEM<br />
National Small Grains Collection<br />
History<br />
Present Collection<br />
Core Subset<br />
<strong>Rice</strong> Crop Germpiasm Committee<br />
Dale Bumpers National <strong>Rice</strong> Research Center<br />
Germpiasm Resources Information Network<br />
National Center for Genetic Resources Conservation<br />
Plant Germpiasm Quarantine Office<br />
INTERNATIONAL RICE GERMPLASM RESOURCES<br />
Africa<br />
China<br />
India<br />
Japan<br />
Malaysia<br />
Philippines<br />
Thail<strong>and</strong><br />
Vietnam<br />
USE OF GERMPLASM IN RICE IMPROVEMENT<br />
REFERENCES<br />
<strong>Rice</strong>: Origin, History, Technology, <strong>and</strong> Production, edited by C. Wayne <strong>Smith</strong><br />
ISBN 0-471-34516-4 © <strong>2003</strong> John Wiley & Sons, Inc.
598 Germpiasm Resources<br />
INTRODUCTION<br />
Maintenance o f the critical genetic diversity that crop germpiasm represents is the<br />
basic factor that motivates the establishment o f germpiasm collections. Maintenance,<br />
coupled with acquisition, documentation, <strong>and</strong> distribution, are the primary functions<br />
o f all crop germpiasm collections. Constant vigilance is required to preserve the<br />
genetic diversity represented by tlie rice (Oryza spp.) seed stored in germpiasm collections<br />
in the United States <strong>and</strong> other countries. <strong>Rice</strong> seed will maintain satisfactory<br />
viability for only 1 to 5 years in warm, humid regions when stored under ambient<br />
conditions with no control over temperature <strong>and</strong> humidity. In contrast, rice seed will<br />
remain viable for 20 years <strong>and</strong> longer if maintained under controlled conditions with<br />
low relative humidity <strong>and</strong> cool temperatures.<br />
The h<strong>and</strong> of humans has been im portant in maintaining genetic diversity in<br />
rice <strong>and</strong> other crops, but humans have also contributed to a loss in genetic diversity<br />
through breeding <strong>and</strong> selection o f improved cultivars. Breeding adapted rice cultivars<br />
suited for commercial <strong>production</strong> invariably leads to a narrowing o f the deployed<br />
germpiasm resource base since relatively few cultivars will be in <strong>production</strong> at any<br />
given time. In a study o f the development o f United States rice cultivars, Dilday (1990)<br />
found that the prominent long-grain cultivars Lebonnet <strong>and</strong> Lem ont have more that<br />
72% o f their genes in com mon, <strong>and</strong> the medium-grain cultivars Calrose <strong>and</strong> Caloro<br />
have almost 90% of their genes in com mon.<br />
The rice component o f the U.S. Departm ent o f Agriculture-Agricultural Research<br />
Service (USDA-ARS) National Small Grains Collection (NSGC) includes over<br />
17,000 accessions over 110 countries <strong>and</strong> regions, representing nine Oryza species, but<br />
with most accessions being Oryza sativa, the com m on cultivated rice. Chang (1985)<br />
estimated that 100,000 rice cultivars exist in Asia alone <strong>and</strong> taxonomists include from<br />
20 to 24 species in the genus Oryza. Obviously, gaps are present in the NSGC rice<br />
collection <strong>and</strong> acquisition o f rice germpiasm must be a continuous effort. Naturally<br />
occurring st<strong>and</strong>s of wild Oryza spp. in various parts of the world with potentially useful<br />
genes are also at risk. Adoption o f new, high-yielding rice cultivars by farmers, particularly<br />
in major rice-growing regions, poses a threat o f losing valuable germpiasm<br />
in the form o f disappearing old cultivars or laiidraces. It is imperative that germpiasm<br />
from as many o f these threatened areas as possible is preserved to prevent further loss<br />
of genetic diversity.<br />
Changing environmental conditions, particularly with regard to pathogens,<br />
weeds, <strong>and</strong> insect pests, require the maintenance o f genetically diverse germpiasm<br />
collections so as to permit breeders, geneticists, plant pathologists, entomologists,<br />
<strong>and</strong> others to cope with new pests <strong>and</strong> other challenges. Perhaps the m ost valuable<br />
single contribution o f the NSGC is to provide these researchers with a readily available<br />
source of sufficiently diverse rice germpiasm that is free o f the severe impediments<br />
imposed by necessary plant quarantine requirements.<br />
U.S. NATIONAL PLANT GERMPLASM SYSTEM<br />
The U.S, National Plant Germpiasm System (NPGS) consists o f a coordinated group<br />
o f scientists from federal, state, <strong>and</strong> private sectors o f the U.S. agricultural research<br />
community. Responsibilities include (1) the acquisition, maintenance, evaluation,
Germplasm Collection, PreservaHon, <strong>and</strong> Utilization 599<br />
enhancement, <strong>and</strong> distribution o f a broad array o f germplasm; (2) research on the<br />
preservation o f genetic diversity <strong>and</strong> metliods o f preserving viability through im <br />
proved storage procedures; <strong>and</strong> (3) m onitoring o f genetic vulnerability (Otto, 1985).<br />
Following is a description o f the key components of the NPGS related to rice germplasm.<br />
National Small Grains Collection<br />
Histor/<br />
Early plant explorers <strong>and</strong> collectors made im portant contributions to the genetic diversity<br />
in the NSGC. The importance o f exp<strong>and</strong>ing the diversity o f Oryza germplasm<br />
in the NSGC is widely recognized, with exploration <strong>and</strong> especially collection <strong>and</strong><br />
exchange o f rice germplasm continuing to be a high priority among rice researchers.<br />
The establishment o f the USDA Seed <strong>and</strong> Plant Introduction Office in 1897 in <br />
cluded provisions to acquire <strong>and</strong> m aintain plant material that may contribute either<br />
directly or indirectly to crop improvement <strong>and</strong> to distribute useful introductions<br />
to plant breeding <strong>and</strong> other research programs. These activities were accomplished<br />
within the USDA by agents o f the Office o f Cereal Investigations <strong>and</strong> later by Investigation<br />
Leaders or other researchers in the Cereal Crops Research Branch. A special<br />
appropriation o f the Research <strong>and</strong> Marketing Act of 1946 provided the funds for<br />
grouping the small grains into one collection under the management o f a USD A -<br />
ARS curator. Appropriations arising from tire Research <strong>and</strong> Marketing Act o f 1946<br />
were intended to be used to (1) grow introductions in special quarantine nurseries,<br />
(2) ensure the maintenance o f viable seed, (3) accumulate data on adaptation <strong>and</strong> reaction<br />
to pests, (4) catalog other inform ation o f use in improving the crop, <strong>and</strong> (5) fill<br />
requests for seed from researchers. In 1948, the NSGC was organized as an official<br />
USDA project at the Beltsville Agricultural Research Center in Beltsville, Maryl<strong>and</strong><br />
(Wesenberg et al., 1992).<br />
Prior to 1948, various individuals collected germplasm accessions <strong>and</strong> researchers<br />
or scientists maintained their own germplasm collections. Although a num ber o f<br />
researchers or other individuals held small germplasm collections or single cultivars<br />
or accessions, no central, organized program existed. For the m ost part, the program<br />
was in cooperation with Arkansas, California, Louisiana, <strong>and</strong> Texas Agricultural E x<br />
periment Stations (AESs). Some rice research was also conducted in cooperation with<br />
the Florida, Mississippi, Missouri, <strong>and</strong> South Carolina AESs. Examples o f germplasm<br />
collections held by scientists include collections at Stuttgart, Arkansas; Biggs, California;<br />
Crowley, Louisiana; <strong>and</strong> Beaum ont, Texas. C. Roy Adair, the first USDA scientist<br />
stationed at the <strong>Rice</strong> Branch Experiment Station, now known as the <strong>Rice</strong> Research<br />
<strong>and</strong> Extension Center in Stuttgart, Arkansas (1931-1952), maintained the collection<br />
held at Stuttgart (Figure 5.1.1). The rice collection at Stuttgart officially began in 1932<br />
when a local farmer, H. D. Dilday, presented the first rice accession to Adair at the rice<br />
field day,<br />
USDA archives include one record o f an early effort where four cultivars o f rice<br />
were sown but failed to germinate at Washington, D C in 1866. The formal investigations<br />
o f rice in the USDA began with the appointment on September 1, 1898,<br />
o f Seaman A. Knapp as agricultural explorer in the Division o f Botany. He made a
600 Germplasm Resources<br />
m m m m ^rnrnrnrnrnrnrnri:-^<br />
> 1 , ^ 1 .r -.<br />
- ö i . i ' - i . ' - ’ ''.'■ i - , .: ,, „ V<br />
Figure 5.1.1. USDA-ARS Dale Bumpers Motional <strong>Rice</strong> Research Center, Stuttgort, Arkansas, on important Ü.S.<br />
rice reseorcfi center <strong>and</strong> a key location for field evaluations of USDA-ARS Motional Small Grains Collection <strong>Rice</strong><br />
Germplasm. (Courtesy of USDA-ARS Dale Bumpers Hational <strong>Rice</strong> Research Center.)<br />
trip to Japan <strong>and</strong> returned in the spring o f 1899 with 10 tons o f Kiushu rice. This<br />
was distributed in southwestern Louisiana <strong>and</strong> probably eastern Texas. In the fall of<br />
1901, Knapp made a second trip to the Orient to study the gro'tvth habit <strong>and</strong> cultural<br />
practices o f growing rice in Japan, China, India, <strong>and</strong> the Philippines. He returned in<br />
April 1902 after having arranged for the introduction o f numerous cultivai's of rice<br />
from the countries visited.<br />
Cl 1 (C l = Cereal Investigation number) <strong>and</strong> C l 2 o f rice are listed as Japan<br />
Upl<strong>and</strong> <strong>and</strong> Carolina, respectively. They were received March 12, 1903 from T. W.<br />
Wood <strong>and</strong> Sons, Richmond, Virginia. C l 3 is listed as Wild <strong>Rice</strong> <strong>and</strong> was received<br />
March 16,1903 from Leonard Seed Co., Chicago, Illinois. Cl 4 <strong>and</strong> C l 5 are listed as<br />
Japanese <strong>and</strong> Upl<strong>and</strong>, respectively, <strong>and</strong> they were received March 30,1903 from M.W.<br />
Johnson Seed Co. Atlanta, Georgia. Cl 6 is listed as M anchuria <strong>and</strong> was received from<br />
Viim orin Audrieux Co. in France. Cl 7 is listed as wild rice {Zizania aquatica). Cl 8<br />
through C l 13 were received March 1904 from Haage <strong>and</strong> Schmidt, Erfurt, Germany.<br />
Cl 8, Ostiglia, is the earliest rice germplasm accession that remains today in the rice<br />
working collection at Aberdeen, Idaho, C l 14 through Cl 34 were part o f the Ceylon<br />
exhibit, <strong>and</strong> Cl 35 through G I 37 were part of the Chinese exhibit that were obtained<br />
at the Louisiana Purchase Exhibit at St. Louis, Missouri in 1904. C l 38 through Cl<br />
777 were part o f tlie Philippines exhibit at the Louisiana Purchase Exhibit at St Louis,<br />
Missouri, in 1904. These were the first recorded exploration trips <strong>and</strong>/or exchange of<br />
rice germplasm in the United States.<br />
In 1987, a collaborative trip to collect indigenous rice in the Amazon Basin<br />
involved scientists D. Groth <strong>and</strong> E. Nowick from Louisiana State University <strong>and</strong><br />
EMBRAPA in Brazil. They collected 29 samples of O. alta, O, gr<strong>and</strong>iglumis, <strong>and</strong><br />
O. rufipogon. The exploration trip by Groth <strong>and</strong> Nowick in 1987 is the last recorded<br />
exploration trip for rice in the United States. From 1988 to 2000, R. H. Dilday <strong>and</strong>
GeriTiplasm ColiecHon, Preservation, <strong>and</strong> Utilization 601<br />
colleagues obtained 5601 rice accessions from Bangladesh (1052), Brazil (22), China<br />
(204 ), Colom bia (1543), Hungary (105), Indonesia (1847), Ivory Coast (201), Japan<br />
(551), <strong>and</strong> Korea (76). These rice accessions were entered into the NPGS.<br />
The Stuttgart collection was eventually transferred to Beltsville, Maryl<strong>and</strong>, where<br />
it <strong>and</strong> collections referred to above <strong>and</strong> other similar collections became the basis for<br />
the rice com ponent o f the NSGC. C, Roy Adair served as Investigations Leader for<br />
<strong>Rice</strong> Research in the USDA-ARS Cereal Crops Research Branch at Beltsville from<br />
1952 until an administrative reorganization in 1972, Adair continued to play a key<br />
role in the maintenance o f the rice com ponent o f the NSGC after 1972 <strong>and</strong> until<br />
his retirem ent in 1973. Prior to the move o f the NSGC from Beltsville, Maryl<strong>and</strong> to<br />
Aberdeen, Idaho (Figures 5.1.2 <strong>and</strong> 5.1.3) in 1988, thé rice com ponent o f the NSGC<br />
operated somewhat independent o f other NSGC components, but it is now fully<br />
integrated into the NSGC. The NSGC staff at Aberdeen cooperates closely with ARS<br />
<strong>and</strong> state colleagues at Stuttgart. Four individuals have served as NSGC curator since<br />
1948: D. J. Ward (1948-1959), J. C. Craddock (1959-1979), D. H. <strong>Smith</strong>, Jr. (1 9 8 0 -<br />
1988), <strong>and</strong> H. E. Bockelm an (1989 to present).<br />
Present Collection<br />
The USDA-ARS rice collection, within the NSGC, includes a wide variety o f germplasm.<br />
Nine Oryza species are represented in the NSGC (Table 5.1.1). M ore than<br />
110 countries <strong>and</strong> regions are represented in the <strong>origin</strong>s o f the Oryza accessions<br />
in the NSGC (Table 5.1,2). A tentative brealcdown o f accessions by improvement<br />
status is shown in Table 5.1.3. All passport <strong>and</strong> evaluation data are found on the<br />
..Câ-v<br />
Figure 5.1.2. USDA-ARS Nationol Small Grains Germplasm Researcli Facility, Aberdeen, Idaho. Home of the<br />
USDA-ARS Notional Small Grains Collection, o working collection that maintains over 117,000 small groins<br />
accessions <strong>and</strong> distributes rice <strong>and</strong> other small groins germplasm worldwide. (Courtesy of H. E. Bockelman.)
602 Germplasm Resources<br />
Figure 5.1.3, Storage area of the USDA-ARS Hationol Small Grains Collection, Aberdeen, Idaho. <strong>Rice</strong> <strong>and</strong> other<br />
small grains germplasm accessions ore held in these storages at about 40°F <strong>and</strong> 2 5 % relative humidity. (Courtesy<br />
of H. E. Bockelman.)<br />
TABLE 5.1.1.<br />
March 2001<br />
<strong>Rice</strong> Accessions in NSGC by Taxonomy<br />
0. aha 3<br />
0. barthii 4<br />
0. glaherrima 174<br />
0, glumaepatula 1<br />
0 , hybrid 5<br />
O. latifolia 3<br />
0 . nivara 10<br />
0 , officinalis 1<br />
O. rufipogon 30<br />
0, sativa 17118<br />
Oryza sp. 5<br />
Total 17353<br />
USDA-ARS Germplasm Resources Inform ation Network (GRIN) online at www.arsgrin.gov/npgs.<br />
Core Subset<br />
A core subset o f the Oryza accessions has been established <strong>and</strong> marked on GRIN. It<br />
consists o f 994 accessions (approximately 5.7% o f all Oryza accessions) from every
Gsrmplosm Collection, Preservation, ond UHlization 603<br />
TABLE 5.1.2.<br />
Marcli 2001<br />
Origin of <strong>Rice</strong> Accessions in the USDA-ARS National Small Grains Collection,<br />
Country Count Country Count<br />
Afghanistan 60 Laos 39<br />
Africa 1 Liberia 90<br />
Argentina 107 Macedonia 5<br />
Australia 84 Madagascar 42<br />
Austria 4 Malawi 1<br />
Azerbaijan 37 Malaysia 66<br />
Bangladesh 782 Mali 37<br />
Belize 1 Mexico 115<br />
Bhutan 3 Micronesia 3<br />
Bolivia 17 Mongolia 3<br />
Brazil 315 Morocco 5<br />
Brunei 1 Mozambique 5<br />
Bulgaria 12 Myanmar 61<br />
Burkina Faso 7 Nepal 89<br />
Burundi 1 Netherl<strong>and</strong>s 5<br />
Cambodia 22 Niger 1<br />
Cameroon 14 Nigeria 62<br />
Chad 18 Pakistan 929<br />
Chile 28 Panama 5<br />
China 1942 Papua New Guinea 6<br />
Colombia 328 Paraguay 2<br />
Costa Rica 17 Peru 46<br />
Cote D’Ivoire 27 Philippines 3 081<br />
Cuba 15 Pol<strong>and</strong> 10<br />
Dominican Republic 35 Portugal 66<br />
Ecuador 4 Puerto Rico 49<br />
Egypt 57 Romania 14<br />
El Salvador 57 Russian Federation 103<br />
Fiji 14 Rw<strong>and</strong>a 2<br />
Former Soviet Union 26 Saudi Arabia I<br />
Former Yugoslavia 1 Senegal 49<br />
France 20 Sierra Leone 40<br />
Gabon 1 South Africa 2<br />
Gambia 1 Spain 48<br />
Germany 2 Sri Lanka 186<br />
Ghana 19 St. Lucia 1<br />
Guatemala 16 Sudan 1<br />
Guinea 9 Suriname 64<br />
Guinea-Bissau 7 Swazil<strong>and</strong> 1<br />
Guyana 28 Sweden 1<br />
Haiti 7 Switzerl<strong>and</strong> 1<br />
Honduras 11 Taiwan 834<br />
Hong Kong 18 Tajikistan 3<br />
Hungary 162 ’ Tanzania 6<br />
India 1358 Thail<strong>and</strong> 133<br />
Indochina 1 TVirkey 164<br />
continued
f<br />
604 Germplasm Resources<br />
TABLE S.1.2.<br />
March 2001 ( C o n tin u e d )<br />
Origin of <strong>Rice</strong> Accessions in the USDA-ARS N ational Small Grains Collection,<br />
Country Count Country Count<br />
Indonesia 300 Ukraine 1<br />
Iran 65 United States 1474<br />
Iraq 17 Uruguay 11<br />
Italy 284 Uzbeldstan 52<br />
Jamaica 5 Venezuela 31<br />
Japan 1074 Vietnam 176<br />
Kazakhstan 14 West Africa 3<br />
Kenya 6 Zaire 87<br />
Korea 15 Zimbabwe 1<br />
Korea, North 1 Unluiown/uncertain 1195<br />
Korea, South 366 Total 17 353<br />
Kyrgyzstan 1<br />
TABU 5.1.3. Improvement Status of <strong>Rice</strong> Accessions in the<br />
NSGC, March 2001<br />
Cultivars<br />
Breeding<br />
Genetic<br />
L<strong>and</strong>race<br />
Cultivated (other)<br />
Wild<br />
Uiilaiown<br />
Total<br />
3 264<br />
4408<br />
51<br />
2602<br />
6911<br />
54<br />
63<br />
17 353<br />
country o f <strong>origin</strong>, It was chosen using the following steps: (1) the number of accessions<br />
for each country o f <strong>origin</strong> were counted; (2) the log o f the number o f accessions<br />
for each country of <strong>origin</strong> was calculated; (3) accessions were chosen r<strong>and</strong>omly within<br />
each country of <strong>origin</strong> based on the relative log numbers, with a minim um of one per<br />
country; <strong>and</strong> (4) obvious duplications were removed. Theoretically, the core subset<br />
should represent the m ajority of the diversity in the rice collection <strong>and</strong> will be useful<br />
for preliminary screening for new traits. The core subset will be refined as further<br />
evaluation data are gathered to better characterize the genetic diversity o f the core<br />
accessions.<br />
<strong>Rice</strong> Crop Germplasm Committee<br />
Crop Germplasm Committees are an essential link between the user community<br />
<strong>and</strong> other working <strong>and</strong> advisory components of the NPGS. A 1981 report on the<br />
NPGS (Murphy, 1981) called for Crop Advisory Committees to provide guidelines<br />
for various phases o f germplasm management for a specific crop, including such<br />
activities as germplasm exploration <strong>and</strong> acquisition, germplasm storage, germplasm<br />
regeneration <strong>and</strong> distribution, <strong>and</strong> st<strong>and</strong>ards for germplasm evaluation. The Crop
á<br />
Germplasm Collection, Preservation, <strong>and</strong> Utilízntíon 605<br />
Advisory Committees evolved over time into die present Crop Germplasm Com m ittees.<br />
The concept of Crop Advisory Committees (now, Crop Germplasm Committees)<br />
was developed by the Germplasm Resources Inform ation Project o f the Laboratory<br />
for Inform ation Science in Agriculture at Colorado State University (Murphy, 1981).<br />
The <strong>Rice</strong> Technical W orking Group (RTW G) Germplasm Com m ittee was established<br />
in 1982. The USDA-ARS <strong>Rice</strong> Crop Advisory Committee, subsequently the USD A -<br />
ARS <strong>Rice</strong> Crop Germplasm Committee (RCGC), evolved in 1983 from the RTWG<br />
Germplasm Committee.<br />
The RCGC is composed o f federal, state, <strong>and</strong> private-sector research scientists,<br />
including the NSGC curator. The RCGC developed a descriptor list, that is, a priority<br />
listing o f agronomic, pathological, <strong>and</strong> morphological characters, to aid in the rice<br />
germplasm evaluation process (Table 5.1.4). These descriptors are utilized to characterize<br />
the rice accessions for an array o f traits, greatly enhancing the value o f the<br />
germplasm collection. The RCGC also assists in the development of Oryza exploration<br />
proposals.<br />
Dale Bumpers National <strong>Rice</strong> Research Center<br />
The Dale Bumpers National <strong>Rice</strong> Research Center (D BN RRC), located at Stuttgart,<br />
Arkansas, has coordinated the systematic evaluation o f the NSGC rice collection since<br />
1988. Im portant characters such as weed suppression (allelopathy), herbicide tolerance,<br />
stress tolerance, earliness, <strong>and</strong> high yield have been identified. A thorough<br />
<strong>and</strong> systematic evaluation <strong>and</strong> characterization o f the collection is ongoing <strong>and</strong> the<br />
promising germplasm is being enhanced so that it can be used in cultivar development<br />
TABLE 5.1.4.<br />
NSGC <strong>Rice</strong> Descriptors<br />
Quality<br />
Alkali/spreading value<br />
Ainylose<br />
Aromatic<br />
Endosperm type<br />
Gelatinization temperature<br />
Kernel weight, milled<br />
Parboil loss<br />
Protein<br />
Agronomic<br />
Days to anthesis<br />
Days to flowering<br />
Lodging<br />
Plant height 1 (coded)<br />
Plant height 2 (actual)<br />
Plant type<br />
Ratooning<br />
Upl<strong>and</strong><br />
Disease<br />
Blast<br />
Sheath blight<br />
Morphological<br />
Awn type<br />
Bran color<br />
Grain type<br />
Hull color<br />
Hull cover<br />
Kernel length<br />
Kernel length/width ratio<br />
Kernel weight<br />
Kernel width<br />
Panicle type<br />
Sterile lemma color<br />
Physiological<br />
Allelopathy<br />
Roundup/glyphosate tolerance<br />
Salt tolerance<br />
Straight head
606 Germplosin Resources<br />
programs. Additionally, m ost new rice accessions released from postentry quarantine<br />
<strong>and</strong> existing accessions are regenerated at Stuttgart on a yearly basis.<br />
Germplasm Resources Information Network<br />
The Germplasm Resources Inform ation Network (GRIN ) is the online database to<br />
facilitate the management <strong>and</strong> operation o f the NPGS. Passport <strong>and</strong> evaluation for<br />
the NSGC <strong>and</strong> all other germplasm sites are maintained on GRIN <strong>and</strong> made available<br />
to the world user com munity via the Internet: www.ars-grin.gov/npgs.<br />
National Center for Genetic Resources Conservation<br />
The National Center for Genetic Resources Conservation (NCGRC), located on the<br />
campus o f Colorado State University, Ft. Collins, established in 1958 as the National<br />
Seed Storage Laboratory, is the only long-term storage facility in the United States<br />
for crop germplasm (Figure 5.1.4), The NCGRC is a base collection where all seed<br />
samples are intended for safe long-term storage to prevent loss o f germplasm <strong>and</strong><br />
genetic diversity as opposed to m edium -term storage <strong>and</strong> general distribution from<br />
a working collection such as NSGC. Seed samples are m onitored for viability <strong>and</strong><br />
grown as necessary to prevent seed deterioration or viability loss (Murphy, 1981). The<br />
NCGRC staff also conducts research on basic seed physiology, improved seed storage<br />
methods, <strong>and</strong> procedures to m onitor viability <strong>and</strong> possible genetic change over time.<br />
Plant Germplasm Quarantine Office<br />
All rice imported into the United States is subject to postentry quarantine procedures.<br />
The Plant Germplasm Quarantine Office (PG Q O ), located at Beltsville, Maryl<strong>and</strong>, in<br />
Figure 5.1.4. USDA-ARS tlational Center for Genetic Resources Conservation, Fort Collins, Colorado, a base<br />
collection site anti the only long-term storage facility in the United Stotes for crop germplasm. (Courtesy of<br />
USDA-ARS Notionol Center for Genetic Resources Conservation.)
Germplflsm Collection, Preservation, <strong>and</strong> Utilization 607<br />
cooperation with the USDA Animal <strong>and</strong> Health Inspection Service (A PH IS), conducts<br />
the quarantine procedures for most rice germplasm destined for the NSGC.<br />
INTERNATIONAL RICE GERMPLASM RESOURCES<br />
'<br />
Several scientists have reviewed the rice germplasm exploration <strong>and</strong> collection activi-<br />
ties in other rice-growing areas o f the world. A review o f some o f these countries <strong>and</strong><br />
institutions <strong>and</strong> the scientists involved in preparing the review follows;<br />
Airica (N. Q. Ng)<br />
Africa is rich in rice genetic resources. It contains representatives o f four o f the six<br />
known genomes in the genus Oryza: AA (O. longistaminata, O. barthi, O. ghberrima,<br />
<strong>and</strong> O. sativa), BB <strong>and</strong> CC (O. punctata <strong>and</strong> O. eichingeri), <strong>and</strong> FF (O. bra-chyantha).<br />
When collecting <strong>and</strong> conserving plant genetic resources gained worldwide attention<br />
during the 1970s, the International Board for Plant Genetic Resources (IBPG R),<br />
Rome, Italy <strong>and</strong> the International Institute o f Tropical Agriculture (IITA), Ibadan,<br />
Nigeria recognized the urgency for exploration <strong>and</strong> collecting o f rice genetic resources<br />
in Africa. The Institut de Recherches Agronoiniques Tropicales et des Cultures<br />
(IRAT), Viviers, France <strong>and</strong> the French Office de la Recherche Scientifique et<br />
Technique Outre-Mer (O RSTO M ) located in the Ivory Coast started exploration<br />
<strong>and</strong> collecting of African rice in 1974. IITA began an intensive search throughout<br />
Africa in 1976. IBPG R provided some financial <strong>and</strong> logistic support to strengthen<br />
IITA, IRAT, <strong>and</strong> ORSTOM collection activities. The West Africa <strong>Rice</strong> Development<br />
Association (WARDA), Boualcé, Ivory Coast also became involved. The International<br />
<strong>Rice</strong> Research Institute (IR R I), Los Baños, the Philippines participated in some o f the<br />
preliminary planning at WARDA in 1976 <strong>and</strong> through its liaison role in the IB P G R -<br />
IRRI <strong>Rice</strong> Advisory Committee 1976-1985.<br />
A review by Ng et al. (1983) called for further exploration <strong>and</strong> collection o f<br />
rice in Africa, First-priority areas were Angola, Burkina Faso, Niger, Madagascar,<br />
Mozambique, southern Sudan, Comoro Isl<strong>and</strong>s, the isl<strong>and</strong>s o f Tanzania, <strong>and</strong> Zaire.<br />
Second-priority areas were the Central Republic o f Africa, Mali, Togo, Mauritania,<br />
Gabon, Gambia, Chad, Senegal, Guinea, Republic o f Benin, <strong>and</strong> Sierra Leone.<br />
One o f the m ost active periods o f rice germplasm exploration <strong>and</strong> collection in<br />
Africa was from 1983 to 1989. A plan o f action for field collecting in Africa by IBPGR,<br />
IITA, IRAT, ORSTOM , <strong>and</strong> WARDA was recommended in 1983. Between 1985 <strong>and</strong><br />
1989, IITA fielded 14 plant exploration missions to 14 African countries, <strong>and</strong> a large<br />
number o f new rice germplasm accessions were collected (Goii <strong>and</strong> Ng, 1985; Goli,<br />
1986, 1987a-d; Osimmakinwa, 1986; Padulosi 1987a-c, 1988; Vodouhe et al., 1990).<br />
These explorations netted a total o f 679 new germplasm accessions, consisting o f<br />
418 O. sativa, 115 O. glaberrima, 35 O. barthii, 93 O, longistaminata, 18 O. punctata,<br />
<strong>and</strong> 1 O. hrachyantha^ In addition, IITA supported the national programs in Ghana<br />
<strong>and</strong> the Republic o f Benin in collecting Oryza germplasm in 1988-1989 <strong>and</strong> 1989,<br />
respectively.<br />
IBPG R supported the national programs o f Burkina Faso (1983 <strong>and</strong> 1984), M adagascar<br />
(1984 <strong>and</strong> 1987), <strong>and</strong> Kenya (1984) in in-country explorations (IBPGR, 1984,
608 Germpiasm Resources<br />
1 9 8 5 ,1 9 8 6 ,1 9 8 7 ,1 9 8 8 ). IRRI was involved in the exploration o f Madagascar during<br />
1984-1985. In addition, IBPG R collaborated with IITA in an exploration in Mali during<br />
1986. These explorations netted more than 1463 samples o f new rice germpiasm.<br />
Except for the materials from Kenya, m ost o f the germpiasm collected were received<br />
at IITA <strong>and</strong> shared with IRRI (IRRI, 1991).<br />
Another active period o f rice germpiasm exploration <strong>and</strong> collection in Africa was<br />
coordinated by IRRI from 1995 to 2000. More than 350 rice samples were collected<br />
in at least nine African countries. Additional details are given later in the section<br />
“Philippines (IRRI).”<br />
China (Cunshan Ying]<br />
<strong>Rice</strong> is the most im portant crop in China. The area planted to rice is about 33 million<br />
ha <strong>and</strong> it is 28% o f the country’s total crop area <strong>and</strong> 23% of the world’s rice area. <strong>Rice</strong><br />
<strong>production</strong> is about 44% o f China’s total grain <strong>production</strong> <strong>and</strong> 37% o f the world’s<br />
rice <strong>production</strong> (IRRI, 1988). The <strong>history</strong> of rice cultivation in China dates back at<br />
least 7000 years. Natural <strong>and</strong> human selection o f rices adapted to varying ecological<br />
conditions <strong>and</strong> cropping systems have resulted in a broad array o f cultivars. The<br />
diversity o f indigenous cultivars <strong>and</strong> wild rices is very rich (CAAS^ 1986).<br />
Field survey <strong>and</strong> collecting o f rice germpiasm have been the focus o f conservation<br />
efforts in China for m ost o f the twentieth century. However, three periods o f exploration<br />
to assemble the nationwide diversity of rice germpiasm occurred in the 1930s,<br />
the m id-1950s, <strong>and</strong> 1978 to the present. From 1978 to 1983, an extensive exploration<br />
for wild relatives of rice in Yunnan, Guangxi, Guangdong, Fujian, Hunan, <strong>and</strong> Jiangsi<br />
Provinces yielded 3200 seed or plant samples. Consequently, much rice germpiasm,<br />
including traditional cultivars <strong>and</strong> wild rices, has been collected <strong>and</strong> is conserved<br />
(CAAS, 1986; Chang et al., 1987).<br />
Since 1983 additional collecting has been undertalcen by the Institute o f Crop<br />
Germpiasm Resources o f the Chinese Academy o f Sciences in collaboration with the<br />
Hubei <strong>and</strong> Guangdong Academies o f Agricultural Sciences. The areas explored were<br />
Tibet, Shen-nong-jia, the three gorges on the upper reaches of the Yangtze River<br />
bordering the western part o f Hubei Province (19 counties) <strong>and</strong> the eastern part of<br />
Sichuan Province (3 counties), <strong>and</strong> Hainan Isl<strong>and</strong> (19 counties). China did not have<br />
a modern gene bank until 1980. Seed stocks were scattered over different provinces,<br />
with some rice germpiasm kept at cool <strong>and</strong> semiarid sites (IRRI, 1991).<br />
India (R. S. Rnna <strong>and</strong> $. D. Sharma)<br />
Collecting the variability observed in indigenous rice cultivars began in India around<br />
1900. The work received special attention following the establishment o f the Agricultural<br />
Research Station at Dacca in 1911 <strong>and</strong> the Paddy Breeding Station at Coimbatore<br />
in 1912. Setting up the Indian Council o f Agricultural Research (ICAR) at New Delhi<br />
in 1929 <strong>and</strong> the Central <strong>Rice</strong> Research Institute (C RRI) at Cuttack in 1946 further<br />
strengtliened these efforts. The establishment o f these stations <strong>and</strong> institutes led to the<br />
cultivation o f 394 cultivars developed from pureline selections among the collected<br />
germpiasm.
Germplasm Collection, Preservation, <strong>and</strong> Utilization 609<br />
During the second phase o f systematic explorations, the Jeypore Botanical Survey<br />
explored South Orissa <strong>and</strong> adjoining areas o f Madhya Pradesh during 1955-1960,<br />
which led to the collection o f 1745 cultiváis. During 1965-1967, 900 traditional cultiváis<br />
o f Manipur in far eastern India were collected. The Assam <strong>Rice</strong> Collection of<br />
6630 cultiváis was made by the staff o f the Indian Agricultural Research Institute<br />
during 1967-1972. The Raipur collection o f 19,116 rice cultiváis grown locally in<br />
Madhya Pradesh region was made from 1971-1976. An additional collection o f 1938<br />
cultiváis was made through a special drive for upl<strong>and</strong> cultivars under cultivation in<br />
Andhra Pradesh, Karnataka, Maharashtra, Madhya Pradesh, Uttar Pradesh, Orissa,<br />
<strong>and</strong> West Bengal. Collaborative explorations by NBPGR <strong>and</strong> state agricultural universities<br />
added another 7000 cultivars during 1978-1980. The Vigyan Parishad Kendra<br />
Agricultural Station at Almora collected 1247 cultivars from hilly regions o f Uttar<br />
Pradesh. The National Bureau o f Plant Genetic Resources (N BPGR), New Delhi,<br />
India <strong>and</strong> the Central <strong>Rice</strong> Research Institute (C RRI), Cuttack, India jointly explored<br />
Silddm, South Bihar, <strong>and</strong> parts of Orissa in 1985 <strong>and</strong> collected 447 local types. Explorations<br />
by N BPG R during 1983-1989 led to further additions o f 4862 cultivars to the<br />
national germplasm collection.<br />
In addition to spectacular variability in its traditional cultivars, India is also rich<br />
in genetic diversity o f wñd Oryza species, particularly O. nivara, O. rufipogon> O.<br />
ojficinaliS) <strong>and</strong> O. granulata. Collecting these materials began with the pioneering<br />
work o f S. Sampath at CRRI during 1948-1955. He focused attention on O. perennis.<br />
Subsequently, S. V. S. Shastry <strong>and</strong> his associates at lA RI made extensive collections<br />
of wild species o f Oryza from western, northern, central, <strong>and</strong> eastern India <strong>and</strong> assembled<br />
a considerable amount o f genetic variability, including O. nivara <strong>and</strong> O.<br />
officinalis.<br />
The national gene bank at N BPGR has almost 7000 o f these indigenous collections<br />
in long-term storage. Active collections maintained by CRRI in Cuttack <strong>and</strong> by<br />
Indira G<strong>and</strong>hi Vishva Vidyalaya in Raipur each contain about 20,000 rice germplasm<br />
accessions. A large number o f collections are scattered over nearly 30 rice research<br />
centers across the country.<br />
Several countries have joined the effort to collect wild rices in India. Japanese<br />
exploration teams led by H. Kihara in the early 1960s <strong>and</strong> T. Watabe in the late 1960s<br />
<strong>and</strong> early 1970s made systematic collections in western UUar Pradesh, Bihar, Andhra<br />
Pradesh, <strong>and</strong> parts o f Maharashtra. H. I. Oka traveled extensively on collecting trips<br />
in different parts o f India. French scientists from IRAT <strong>and</strong> O RSTO M collaborated<br />
with ICAR teams in collecting O. officinalis, O. nivara, <strong>and</strong> O. rufipogon from Goa,<br />
Karnataka, Maharashtra, <strong>and</strong> Gujarat in 1986. During 1987-1989, ICAR <strong>and</strong> IRRI<br />
scientists undertook more intensive collecting for wild rices in southern India <strong>and</strong><br />
western Bengal (IRRI, 1991).<br />
Japan (K. Hayashi)<br />
Except for a few crop species, Japan is deficient in plant genetic resources. The importance<br />
o f collecting <strong>and</strong> conserving plant genetic resources is now widely recognized.<br />
The M inistry o f Agriculture, Foresty, <strong>and</strong> Fisheries has been promoting genetic resources<br />
projects for many years. Since 1975, it has regularly sent missions to various<br />
countries to collect plant genetic resources. Four or five collecting teams have been
610 Gefmplasm Resources<br />
organized annually. The activities are based on a long-term plan for coEecting plant<br />
genetic resources outside Japan.<br />
During the 1980s, three rice collecting missions were undertaken in tropical<br />
Asia in cooperation with the national governments concerned. In 1983, two Japanese<br />
researchers explored Bangladesh <strong>and</strong> coUected 152 cultivars. In 1986, two Japanese<br />
scientists were sent to northern <strong>and</strong> northeastern Thail<strong>and</strong>, where they collected 99<br />
cultivars <strong>and</strong> 17 populations o f Oryza sp. In 1989, three Japanese scientists visited<br />
Sumatra Isl<strong>and</strong> of Indonesia <strong>and</strong> collected 363 cultivars, including deepwater rice.<br />
Japanese researchers joined IBPG R collecting missions for many crop species<br />
in Nepal in 1984, 1985, <strong>and</strong> 1986, During those missions, the teams collected 273,<br />
295, <strong>and</strong> 263 cultivated rice samples, respectively. In 1989, three Japanese researchers<br />
organized a collecting mission in Pakistan with funds from IBPGR. They collected 191<br />
rice cultivars in cooperation with the Plant Genetic Resources Program o f Palcistan.<br />
In 1983-1989, teams from the national Institute o f Genetics visited Thail<strong>and</strong>,<br />
Indonesia, Bhutan, <strong>and</strong> Bangladesh <strong>and</strong> collected samples o f 432 cultivars <strong>and</strong> 142<br />
wild rices. Details o f the trips have been published (M orishim a et al., 1984; National<br />
Institute o f Genetics, 1987; IRRI, 1991).<br />
Malaysia (A. Md. Zain, Hj. A. Boerhannoedin, <strong>and</strong> 0. Omar)<br />
The 1980s were a very active period o f rice germplasm exploration <strong>and</strong> collection<br />
in Malaysia. Eight collecting trips to different parts o f Malaysia from 1983 to 1990<br />
involved staff o f the Malaysian Agricultural Research <strong>and</strong> Development Institute<br />
(M ARDI). A total of 628 l<strong>and</strong>races <strong>and</strong> 43 populations o f wild rices were collected<br />
<strong>and</strong> complete passport data recorded. Collecting trips by the staff o f the Departm<br />
ent o f Agriculture in Sabah <strong>and</strong> Sarawak States also took place during this period<br />
(IRRI, 1991).<br />
Philippines (IRRI)<br />
From 1995 to 2000, IRRI coordinated 165 collecting missions that were carried out in<br />
22 countries over three continents. The Swiss Agency for Development <strong>and</strong> Cooperation<br />
(SD C) supplied m ost o f the funding support for the missions. The country where<br />
the collection trip was conducted <strong>and</strong> the number o f collecting trips, in parentheses,<br />
that were conducted in each country from 1995 to 2000 are Bangladesh (12), Bhutan<br />
(3), Cambodia (28), Costa Rico (5), Indonesia (8), Kenya (3), Lao PD R (15), Malaysia<br />
(13), Madagascar (5), Malawi (1), Myanmar (3), Mozambique (2), Namibia (2), Na-<br />
pal (3), Philippines (12), Swazil<strong>and</strong> (3), Tanzania (including Zanzibar) (2), Thail<strong>and</strong><br />
(10), Ug<strong>and</strong>a (1), Vietnam (31) Zambia (2), <strong>and</strong> Zimbabwe (1).<br />
A total o f 24,718 O. sativa samples were collected. Another 2416 samples o f 16<br />
Oryza species, weedy types <strong>and</strong> putative hybrids, <strong>and</strong> some unclassified samples were<br />
collected. There were also samples o f at least four species from three related genera<br />
that were collected from 1995 to 2000. Over 80% o f the cultivated rice samples <strong>and</strong><br />
68% o f the wild rice samples have been sent to the International <strong>Rice</strong> Genebanlc (IRG)<br />
at IRRI for long-term storage. The total number o f samples sent to IRRI includes
Gertnplasm Collection, Preservation, <strong>and</strong> Utilization 611<br />
30 samples from seven species (O. officinalisy O. rufipogon, Oryza sp., weedy forms,<br />
Hygroryza aristate, <strong>and</strong> Leersia hex<strong>and</strong>ra) from Bangladesh; 29 weedy forms from<br />
Bhutan; 1102 samples including six species from Cambodia; 312 samples including<br />
four species from Costa Rica; 31 samples including five species from Indonesia; 110<br />
samples including three species from Kenya; 228 samples including eight species from<br />
Lao PDR; 18 samples including two species from Madagascar; 54 samples including<br />
tliree species from Malawi; 34 samples including four species from Malaysia; 32 samples<br />
including four species from Mozambique; 54 samples including five species from<br />
Myanmar; 17 samples including two species from Namibia; 124 samples including<br />
four species from Nepal; 13 samples including four species from the Philippines;<br />
25 samples including two species from Swazil<strong>and</strong>; 69 samples including five species<br />
<strong>and</strong> 10 unknowns from Tanzania; 84 samples including three species from Thail<strong>and</strong>;<br />
15 samples including three species from Ug<strong>and</strong>a; four samples o f O. rufipogon from<br />
Vietnam; 18 samples including four species from Zambia; <strong>and</strong> 12 samples including<br />
four species from Zimbabwe. Cambodia <strong>and</strong> the Lao PD R also took the opportunity<br />
to send some previously collected rice germplasm samples that were not already duplicated<br />
in the IRG. The collecting effort in the Lao PD R included 13,000 samples of<br />
cultivated <strong>and</strong> wild rice that is now safely conserved in the local gene bank <strong>and</strong> in the<br />
IRG. The collecting activities in sub-Saharan Africa focused almost entirely on wild<br />
species.<br />
Thail<strong>and</strong> (S. Chitrakon <strong>and</strong> C. Vutiyano)<br />
About 90% o f the Thai traditional cultivars, mostly lowl<strong>and</strong> rices, have been collected.<br />
The remainder consists o f hill rices (upl<strong>and</strong> type), rainfed lowl<strong>and</strong> rices in remote<br />
areas, <strong>and</strong> wild rices. Thai researchers in regional centers are trying to collect these<br />
genetic resources before they disappear from their natural habitats.<br />
Between 1983 <strong>and</strong> 1989, comprehensive collecting o f cultivated (12,232 samples)<br />
<strong>and</strong> wild rices (733 samples) was undertaken in all parts o f Thail<strong>and</strong>, sometimes with<br />
participation from Japanese <strong>and</strong> IR R I scientists. Complete passport data have been<br />
recorded.<br />
The National <strong>Rice</strong> Seed Storage Laboratory for Genetic Resources at Pathum<br />
Thani supplies approximately 2000 to 3000 seed samples to scientists annually. Some<br />
Oryza sp. seeds often cannot be supplied because seed stock is limited, although<br />
accessions are regenerated each year (IRRI, 1991). IRRI coordinated 10 collecting trips<br />
in Thail<strong>and</strong> from 1995 to 1999. The teams collected 2202 cultivated rice samples <strong>and</strong><br />
84 wild rices.<br />
Vietnam (N. Dang Khoi, B. Chi Buu, <strong>and</strong> L. Ngoc Trinh)<br />
<strong>Rice</strong> germplasm conservation activities in Vietnam began in the early 1930s. The<br />
resulting rice collection was incomplete <strong>and</strong> many of the accessions were lost during<br />
the wai‘ years. In the early 1980s the Vietnam rice collection contained about<br />
2500 accessions. They represented all rice groups o f the country, but were predominantly<br />
from irrigated areas. During the 1980s, the Cuulong <strong>Rice</strong> Research Institute in<br />
I"!
612 Germplasm Resources<br />
Haugiang <strong>and</strong> the National Institute for Agricultural Sciences (INSA), Hanoi, Vietnam<br />
conducted exploration activities. The Cuulong Institute collected traditional<br />
cultivars from the Mekong Delta region. Exploration activities concentrated on collecting<br />
cultivars adapted to deepwater conditions <strong>and</strong> tolerance to acid <strong>and</strong> saline<br />
soils, including wild species. About 500 cultivars <strong>and</strong> four samples o f wild rice species<br />
O. rufipogariy O. nivaruy O. sativa f. spontanea, <strong>and</strong> O. offtcinalis were gathered during<br />
this period.<br />
Between 1984 <strong>and</strong> 1988, INSA collaborated with the Vavilov Institute o f Research<br />
o f the Soviet Union to collect about 300 cultivars in Lai Chau, Son La, Quang Ninh,<br />
Ha Son Binh, <strong>and</strong> Binh Tri Thien Provinces. Vietnam’s rice germplasm collection<br />
currently consists o f m ore than 4000 traditional rice accessions <strong>and</strong> six wild species.<br />
In the 1990s, field collections were directed toward replacement o f nonviable accessions<br />
<strong>and</strong> collecting in the m ore remote areas o f the central highl<strong>and</strong>s, northwestern<br />
region, Mekong Delta, <strong>and</strong> the m ountain regions o f central Vietnam. A national<br />
survey estimated that about 600 to 800 traditional rice cultivars are still in cultivation,<br />
but genetic erosion is accelerating. High priority has been given to collecting wild<br />
species <strong>and</strong> traditional cultivars adapted to adverse environmental conditions (IRRI,<br />
1991). IR R I coordinated 31 collecting trips in Vietnam from 1995 to 1999. During<br />
the 31 trips, IRRI <strong>and</strong> Vietnamese scientists collected 1719 cultivated rice samples<br />
<strong>and</strong> four wild rices.<br />
Mi i<br />
USE OF GERMPLASM IN RICE IMPROVEMENT<br />
J': I<br />
Genetic uniformity, or the lack o f genetic diversity, becam e a m ajor concern to U.S.<br />
breeders, geneticists, <strong>and</strong> the agricultural com m unity in general after the outbreak<br />
o f southern leaf blight on corn in 1970. The leaf blight outbreak on hybrid corn was<br />
due primarily to the ubiquitous use of Texas male-sterile cytoplasm in hybrid seed<br />
<strong>production</strong> (NAS, 1972). In many crops the genetic improvement for yield generally<br />
has been accompanied by a loss in genetic diversity among the cultivars (NAS, 1972;<br />
Walsh, 1981). Therefore, the m ajor question asked by the NAS (1972) committee on<br />
genetic vulnerability o f m ajor crops was: How uniform genetically are other crops<br />
upon which tlie nation depends <strong>and</strong> how vulnerable are they to epidemics? Their<br />
answer was that most crops in the United States are genetically uniform <strong>and</strong> consequently<br />
very vulnerable. Since the 1970 corn leaf blight epidemic, studies have been<br />
conducted to estimate the genetic base o f our major crop species <strong>and</strong> their potential<br />
vulnerability to a disaster caused by disease, insects, drought, physiological disorders,<br />
salinity, alkalinity, <strong>and</strong> numerous environmental causes (St. M artin, 1982; Specht <strong>and</strong><br />
Williams, 1984; Cox et ah, 1985; Darrah <strong>and</strong> Zuber, 1986; <strong>Smith</strong>, 1988).<br />
One hundred <strong>and</strong> forty rice germplasm accessions or cultivars o f rice were evaluated<br />
by Dilday (1990) for their relative genetic contributions o f the different rice<br />
ancestral lines in cultivar development. Fifty-six genotypes were identified in the<br />
Arkansas pedigree, <strong>and</strong> these genotypes could be traced to 13 introductions; 49 genotypes<br />
were identified in the Texas pedigree <strong>and</strong> traced to 12 introductions; 48 genotypes<br />
were identified in the Louisiana pedigree <strong>and</strong> traced to 16 introductions. These<br />
accessions constitute the gene pool o f the southern rice belt. Fifty-seven genotypes<br />
were identified in the western or California pedigree; these genotypes could be traced<br />
to 23 introductions that constitute the gene pool o f the western rice belt.
Germplflsm Collection, Preservotion, <strong>and</strong> Utilization 613<br />
Furthermore, an examination o f the pedigrees o f the 140 rice accessions showed<br />
that all o f the germplasm can be traced to 22 plant introductions in the southern<br />
rice belt (Arkansas, Louisiana, Mississippi, Missouri, <strong>and</strong> Texas) <strong>and</strong> 23 plant introductions<br />
in the western or California rice belt. For example, the genetic base o f the<br />
breeding program in Arkansas in 1990 could be traced to 13 accessions (Sinawpagh,<br />
Marong-Paroc, Guinosgar, PaChain, unknown from Japan, unloiown from Philippines,<br />
unknown from China, Carolina Gold, T 487, Badkalamkati, Hill selection,<br />
CI5309, <strong>and</strong> Early W ataribune), The genetic base o f the breeding program in Texas<br />
was traced to 12 accessions; the first 10 listed above for Arkansas, plus two more,<br />
Jojutla <strong>and</strong> Bruinmissie. The genetic base o f the rice breeding program in Louisiana<br />
was traced to 16 accessions; the first eight listed for Arkansas, plus C l 5309 (which also<br />
is part o f the ancestry o f the Arkansas cultivars), plus Delitus, Honduras, Taichung<br />
Native 1, Sri-Lanka H -4, 13-D, <strong>and</strong> two unknowns. In California, the genetic base<br />
o f the rice breeding program in 1990 was traced to 23 accessions. Seven of the accessions<br />
(Chinese, M arong-Paroc, Sinawpash, Carolina Gold, unknown from Japan,<br />
Early Wateribune, <strong>and</strong> C l 5309) are com m on to ancestry o f Arkansas cultivars. This<br />
type o f genetic base in rice has led to higli coefficients o f parentage not only among<br />
new cultivars developed at individual locations but between cultivars developed at<br />
different locations, especially in the southern rice breeding programs. In other words,<br />
many old genes in rice have been used to produce new cultivars.<br />
The coefficients o f parentage between long-grain cultivars showed, in paired<br />
comparisons, that Lebonnet vs. Lem ont have more than 72% o f their genes in com <br />
mon, <strong>and</strong> more than 60% o f the genes are com m on between Lebonnet vs. Skybonnet,<br />
Toro vs. Rexoro, Tebonnet vs. Bonnet 72. More than 50% o f the genes are com mon<br />
between Newbonnet vs. Dawn, L201 vs. L202, <strong>and</strong> Tebonnet vs. Newbonnet. More<br />
than 40% o f tire genes are com m on between Starbonnet vs. Bluebonnet 50, Newbonnet<br />
vs. Labelle, <strong>and</strong> Bond vs. Starbonnet. Finally, Tebonnet vs. Dawn, Newbonnet vs.<br />
Lemont, Tebonnet vs, Lebonnet, <strong>and</strong> Tebonnet vs. Lemont have between 20 <strong>and</strong> 40%<br />
of their genes in com m on. The gene pool o f the medium-grain cultivars appears to<br />
have even less genetic diversity than the long-grain gene pool. For example, almost<br />
90% o f the genes are com m on in tire cultivars Calrose <strong>and</strong> Caloro. M ore than 70%<br />
o f the genes are com m on between M 7 vs. M 301, M 5, vs, M 301, Nova vs. Nova 66,<br />
<strong>and</strong> M 6 vs. Calrose 76. M ore than 60% o f the genes are com m on between Mars vs.<br />
Saturn, Nova 66 vs. Nova 76, <strong>and</strong> Saturn vs. LaCrosse. M ore than 50% o f the genes<br />
are com m on between Nova vs. LaCrosse, <strong>and</strong> Nova vs. Brazos. Furthermore, more<br />
than 40% o f the genes are com m on between Mars vs. Nova 76, <strong>and</strong> Mars vs. Zenith,<br />
<strong>and</strong> between 20 <strong>and</strong> 40% o f the genes are com m on for Brazos vs. Pecos, <strong>and</strong> Mars<br />
vs, Brazos.<br />
The coefficients o f parentage o f cultivars released at tlie four locations showed<br />
that about 50% o f the genes were com m on within all long-grain cultivars released<br />
in California, 38% in Texas, 25% in Arkansas, <strong>and</strong> 13% in Louisiana. Furthermore,<br />
the coefficients o f parentage between locations for long-grain cultivars showed that<br />
24 <strong>and</strong> 21% o f the genes were com m on in the Arkansas <strong>and</strong> Texas, <strong>and</strong> Texas <strong>and</strong><br />
Louisiana cultivars, respectively. Also, 19% o f the genes were com m on in all the<br />
Arkansas <strong>and</strong> Louisiana long-grain cultivars that have been released. The same trend<br />
was shown for the medium-grain cultivars. For example, between 30 <strong>and</strong> 40% o f<br />
the genes are the same in all the medium-grain cultivars released in Arkansas <strong>and</strong><br />
California, <strong>and</strong> 20 to 30% o f the genes are the same among the cultivars released in
614<br />
Gsrmplasm Resources<br />
Texas <strong>and</strong> Louisiana. These data demonstrated how closely related the rice cultivars<br />
were in 1990 that have been released in the United States.<br />
The total rice germplasm base in the United States in 1990 was traced to 140<br />
accessions. GRIN in 2001 lists over 17,000 accessions in the rice portion of the NSGC,<br />
comprising nine Oryza species, <strong>and</strong> these accessions <strong>origin</strong>ated in more than 110<br />
countries <strong>and</strong> regions. However, the m ajor portion (17,118) of the collection is O.<br />
sativa, the genus <strong>and</strong> species of cultivated rice in the United States. The rice portion<br />
o f the NSGC demonstrates the vast genetic diversity that exists in rice. The coefficient<br />
o f parentage is a promising tool for selecting diverse germplasm in breeding <strong>and</strong><br />
enhancement programs to increase the genetic base o f a species. Also, coefficient of<br />
parentage, along with pedigree schematics, can be useful for germplasm selection in<br />
evaluation programs, or simply as a tool to trace genetically related phenomena from<br />
ancestor to ancestor.<br />
Pedigree schematics o f rice cultivars released in Arkansas, Texas, Louisiana, <strong>and</strong><br />
California through 2000 are shown in Figures 5.1.5 to 5.1.8, respectively. The <strong>origin</strong>s<br />
of rice cultivars <strong>and</strong> ancestral lines <strong>and</strong> their Cl or PI numbers are listed in Table 5.1.5.<br />
y:'<br />
I<br />
f !■<br />
Figure 5.1.5.<br />
Pedigree schematic of rice cultivars released in Arkansas.
k<br />
Germplasm Collecfion, Preservation, <strong>and</strong> Utilization 615<br />
CRGD<br />
CHNA<br />
PACM<br />
JFSN<br />
DXBL<br />
Figure 5.1.6.<br />
Pedigree schematic of rice cultivars released in Texas.
Germplasm Collection, Preservafíon, <strong>and</strong> Utilization 617<br />
EYWB<br />
CHNA<br />
CALO<br />
LDYW<br />
COLU<br />
70-65-26<br />
Figure 5,1.8.<br />
Pedigree schemotic of rice cultivors releosed in California.
618 Germplasm Resources<br />
MAPA<br />
RXOR<br />
RED<br />
UNIC2<br />
CIÑA<br />
LTSL<br />
PETA<br />
DGWG<br />
IR-8<br />
ivl<br />
ÍR l-7 K65 RRÜN<br />
PI275543<br />
JR-22 R48-257<br />
CI9901 R134-1<br />
5915C35-8 DERLA
Garinplosm Collection, Preservation, <strong>and</strong> Utilization<br />
619<br />
TABLE 5.1.5.<br />
Selected <strong>Rice</strong> CuItivars <strong>and</strong> Ancestral Lines U sed to Develop U,S. <strong>Rice</strong> Pedigrees<br />
No. Abbrev Designation Origin Cl or PI<br />
1 ADAH Adair Arkansas PI 568890<br />
2 ALAN Alan Arkansas PI 538253<br />
3 AROS Arkrose Arkansas Cl 8310<br />
4 A002 Cl 9187 RXORyCI Arkansas Cl 9187<br />
7689/3/TXPT//RXOR/SBLR<br />
5 A008 Cl 9556 Cl 9453/CI 9187 Arkansas Cl 9556<br />
6 AGIO Cl 9580 Northrose/ZNTH Arkansas Cl 9580<br />
7 A020 Cl 9841 VGLD/CI 9556//Dawn Arkansas Cl 9841<br />
8 A201 A~201 California PI 592740<br />
9 BBLE Bluebelle Texas Cl 9544<br />
10 BBNT Bluebonnet Texas Cl 8322<br />
11 BB50 Bluebonnet 50 Texas Cl 8990<br />
12 BDKK Badlcalamkati Bangladesh Cl 7689<br />
13 BLMT Bellemont Texas Cl 9978<br />
14 BLPT Belle Patna Texas Cl 9433<br />
15 BNGL Bengal Louisiana PI 561735<br />
16 BNSL Bruininissie sel. United States<br />
17 BN73 Bonnet 73 Arkansas Cl 9654<br />
18 BOND Bond Arkansas PI 474579<br />
19 BRAZ Brazos Texas Cl 9875<br />
20 BROS Blue Rose Louisiana Cl 1962<br />
21 BRUN Bruininissie<br />
22 B82-761 B82-761<br />
23 CALO Caloro California Cl 1561-1<br />
24 CALY Calady United States Cl 7786<br />
25 CAMS M-5 California Cl 9964<br />
26 CAM7 M-7 California Cl 9967<br />
27 CAM9 M--9 California Cl 9968<br />
28 CAS6 S6 California Cl 9965<br />
29 CA40 Calady 40 United States Cl 9202<br />
30 CB692 CB692<br />
31 CHNA Chinese China<br />
32 CINA Cina<br />
33 CI19701 Cl 9701 Belle Patna/CI 9187 United States Cl 9701<br />
34 CLPL Calpearl United States NSL 169611<br />
35 CODR Cocodrie Louisiana PI 606331<br />
36 COLU Colusa California Cl 1600<br />
37 CP31 Century Patna 231 Texas Cl 8993<br />
38 CPRS Cypress Louisiana PI 561734<br />
39 CRGD Carolina Gold Madagascar Cl 8993 or<br />
Cr1645<br />
40 GROS Calrose California Cl 8988<br />
41 CR76 Calrose 76 California Cl 9966<br />
42 CSM3 CS-M3 California Cl 9675<br />
43 CSS4 CS-S4 California Cl 9835<br />
44 CU1-U2<br />
45 CI9722 Short-Strawed Starbonnet Arkansas Cl 9722<br />
46 C6SM C6 Smooth<br />
continued
620 Germplasm Resources<br />
1<br />
TABLE 5,1.5, Selected <strong>Rice</strong> CuHivars <strong>and</strong> Ancestral Lines Used to Develop U.S. <strong>Rice</strong> Pedigrees (C on tin u ed )<br />
No. Abbrev Designation Origin Cl or PI<br />
47 ClOl Calinochi-101 California PI 494104<br />
ii; 48 C201 Calmochi-201 California Cl 9972<br />
49 C202 Calmochi“202 California Cl 9977<br />
p 50 DAWN Dawn Texas Cl 9534<br />
{:<br />
■Í! 51 DGWG Dee-Geo~Woo-Gen Taiwan PI 279131<br />
52 DLLA Della Louisiana Cl 9483<br />
I<br />
.ii 53 DLMT Dellmont Texas PI 546364<br />
54 DLRS Deliróse Louisiatra PI 593241<br />
: 1<br />
55 DLRX Deires Louisiana Cl 8320<br />
56 DLTS Delitus Louisiana Cl 1206<br />
57 D-31 D-31 IRRI9507 Unknown PI 460004 or<br />
PI 461225<br />
58 DREW Drew Arkansas PI 596758<br />
1<br />
' 59 DXBL Dixiebelle Texas PI 595900<br />
: 60 EDTH Edith United States Cl 2127<br />
■ r . 61 ERLS Earlirose, California Cl 9672 or<br />
PI 399947<br />
w .<br />
62 ESD7 ESD7-3 California<br />
;■<br />
63 EYWB Early Wataribune Unlmown Cl 9738<br />
îÎi;-<br />
64 FRTA Fortuna Louisiana Cl 1344<br />
65 GFMT Gulfmont Texas PI 502967<br />
66 GROS Gulfrose Texas Cl 9416<br />
67 GUGR Guinosgar<br />
£| 68 HLSL Hill sel. United States Cl 9052<br />
|K<br />
69 HNDS Flonduras Unknown PI 461322<br />
70 H012 H012-1-I United States<br />
71 IMBB Bluebonnet Improved Texas Cl 8992<br />
I; ' 72 IMBR Improved Bluerose Cl 2128<br />
I 73 IR-8 IR-8 Philippines PI 312627<br />
74 JFSN Jefferson Texas PI 593892<br />
1 -<br />
75 IJLA Jojutla Mexico PI 276884<br />
76 JKSN Jackson Texas PI 572412<br />
i<br />
77 JODN Jodon Louisiana PI 583831<br />
|; 78 KATY Katy Arkansas PI 527707<br />
79 KBNT Kaybonnet Arkansas PI 583278<br />
80 KKRS Kokaho/Rose United States Cl 9673<br />
: 81 KSHK Koshihikari Japan PI 514661<br />
^ 82 K65 K-65 Surinam PI 276884<br />
83 LACR LaCrosse Louisiana Cl 8985<br />
P--'<br />
1 ! ' 1 84 LAGU LaGrue Arkansas PI 568891<br />
'<br />
’ 85 LBLE Labelle Texas Cl 9708<br />
1- ' 86 LENT Lebonnet Texas Cl 9882<br />
■ 87 LDYW Lady Wright United States Cl 5451<br />
fi' 88 LEAH Leah Louisiana Cl 9979<br />
Ï'- ■ i 89 LFTE Lafitte Louisiana PI 593690<br />
i 90 LMNT Lemont Texas PI 475833<br />
! 91 LTSL Latisañ Pakistan PI 283684<br />
i 92 L003 Cl 9453 LACR//ZNTFI/Nira Louisiana Cl 9453<br />
pi<br />
continued
Germplasm Collection, Preservation, <strong>and</strong> Utilization 621<br />
TABLE 5.1.5.<br />
Sele cted R ice C u ltiv a rs a n d A n c e stra l L in e s U se d to D e v e lo p U.S. R ice P e d ig r e e s (ConHnued)<br />
No. Abbrev D esignation O rigin Cl or PI<br />
93 LO 10 Dawn/245717/3/13-D/RRUN Louisiana Cl 9902<br />
94 LllO LAllO Louisiana Cl 9962<br />
95 L201 L-201 California Cl 9971<br />
96 L202 L-202 California PI 483097<br />
97 L203 L-203 California PI 547249<br />
98 L204 L-204 California PI 592739<br />
99 MAPA Maro ng“ Faroe Phillippines<br />
100 MARS Mars Arkansas Cl 9945<br />
101 MBLE Maybelle Texas PI 538248<br />
102 MDSN Madison Texas PI 603010<br />
103 MECY Mercury Louisiana PI 506428<br />
104 MILE Millie Arkansas PI 538254<br />
105 M7 California Cl 9967<br />
106 M7P-1 M7P-1 California<br />
107 M7P-5 M7P 5 California<br />
108 MlOl M-101 California Cl 9970<br />
109 M103 M-103 California PI 527566<br />
110 M201 M-201 California Cl 9980<br />
111 M203 M-203 California PI 514276<br />
112 M204 M-204 California PI 559472<br />
113 M301 M-301 California Cl 9973<br />
114 M302 M-302 California GI9976 or<br />
PI 406068<br />
115 M401 M-401 California Cl 9975<br />
116 MECY Mercury Louisiana PI 506428<br />
117 NATO Nato Louisiana Cl 8998<br />
118 NIRA Nira Louisiana Cl 2702<br />
119 NOVA Nova Arkansas Cl 9459<br />
120 NROS Northrose Arkansas Cl 9407<br />
121 NTAI Nortai Arkansas Cl 9836<br />
122 NV66 Nova 66 Arkansas Cl 9481<br />
123 NV76 Nova 76 Arkansas Cl 9948<br />
124 NWBT Newbonnet Arkansas PI 474580<br />
125 NWRX Newrex Texas Cl 9969<br />
126 ORIN Orion Arkansas PI 549114<br />
127 PACM Pa Chain<br />
128 PCOS Pecos Texas PI 476818<br />
129 ■ PETA Peta Indonesia PI 233289 or<br />
PI 281804<br />
PI 275543 PI 275543<br />
130<br />
131 PI 321161 (IR 456-3-2-1) Philippines PI 321161<br />
132 PI 457920 DM-2 Paliistan PI 457920<br />
133 PLMR Palmyra Missouri Cl 9463<br />
134 PRLD Prelude United States Cl 8311<br />
135 R-D Rexoro/Delitus Texas<br />
136 REMI Reimei California PI 318644<br />
137 RRUN Cl 9425-2 RXRE/Unknown United States<br />
138 RSMT Rosemont Texas PI 546365<br />
continued
622 Gorniplasm Rosources<br />
TABLE 5.1^.<br />
Selected <strong>Rice</strong> Cultivars <strong>and</strong> Ancestral Lines Used to Develop U.S. <strong>Rice</strong> Pedigrees (Continued)<br />
No. Abbrev Designation Origin Cl or PI<br />
139 RU7402 RU 740<strong>2003</strong><br />
140 RU83 RU 8303116<br />
141 RXAR Rexark<br />
142 RXMT Rexmont<br />
143 RXOR Rexoro<br />
144 RXPL Rexoro Purple Leaf<br />
145 RXRG Rexark Rogue<br />
146 R26 R26<br />
147 R50-11 R50-11<br />
148 R48-257 R48-257<br />
149 R134-1 R134-1<br />
150 SBLR Supreme Bluerose<br />
151 SD7 SD7<br />
152 SHMD Shoemed<br />
153 SKBT Skybonnet<br />
154 SL017 SL017<br />
155 SMN3 Smooth No.3<br />
156 SMN4 Smooth No,4<br />
157 SNBT Suuboimet<br />
158 SNPG Sinawpagh<br />
159 SRLA Sri-Lanka H-4<br />
160 STBN Stabonnet<br />
161 STRN Saturn<br />
162 SlOl S-101<br />
163 S102 S-102<br />
164 S201 S-201<br />
165 S301 S-301<br />
166 TBNT Tebonnet<br />
167 TDCN Taducan<br />
168 TETP Tetep<br />
169 TN-1 Taichung Native 1<br />
170 TORO Toro<br />
171 TP49 TP-49<br />
172 TRSO Terso<br />
173 TXPT Texas Patna<br />
174 TYHK Toyohikari<br />
175 TXMT Texmont<br />
176 Tool Cl 5309 UNMD Glut var.<br />
177 T002 CI9122HLSL/BBNT<br />
178 T004 Cl 9515 CRGD/5309/SHMD<br />
179 T005 Cl 9545 T487/RXRG<br />
180 T007 Cl 9881 BBLE/BLPT/Dawn<br />
181 T018 PI 331581 BBLE/6XT-1<br />
182 T2414 Tainung-sen-yu 2414<br />
183 T487 T487<br />
184 UNPRC Unknown (China)<br />
Arkansas<br />
Texas<br />
Arkansas<br />
Texas<br />
Louisiana<br />
Louisiana<br />
Louisiana<br />
California<br />
United States<br />
Philippines<br />
Texas<br />
Unknown<br />
Louisiana<br />
Unknown<br />
Sri Lanka<br />
Arkansas<br />
Louisiana<br />
California<br />
California<br />
California<br />
California<br />
Arkansas<br />
Japan<br />
Pakistan<br />
Taiwan<br />
Louisiana<br />
Texas<br />
United States<br />
Texas<br />
Texas<br />
China<br />
Texas<br />
Texas<br />
Texas<br />
Texas<br />
Philippines<br />
Taiwan<br />
China<br />
Cl 8644<br />
PI 502968<br />
Cl 1779<br />
Cl 9217<br />
Cl 9166<br />
Cl 5793<br />
PI 392539<br />
PI 476819<br />
PI 433774<br />
Cl 8989<br />
Cl 12168, CI12170,<br />
orCH2169<br />
Cl 9584<br />
Cl 9540<br />
PI 514277<br />
PI 592738<br />
Cl 9974<br />
PI 536645<br />
PI 487195<br />
PI 431324<br />
PI 271672<br />
Cl 9013 or<br />
PI 483070<br />
NSL 92341<br />
Cl 8321<br />
PI 224656<br />
PI 538249<br />
continued
Germplasm CoHetlion, Preservation, <strong>and</strong> Utilization 623<br />
TABLE 5.1.5. Selected <strong>Rice</strong> Cultivars <strong>and</strong> Ancestral Lines Used to Develop U.S. <strong>Rice</strong> Pedigrees (C on tin u ed )<br />
No. A bbrev Designerfion O rigin Cl or PI<br />
185 UNPJ Unknown (Japan) Japan<br />
186 UNK-X Unknown X<br />
187 UNK2 Unknown-2<br />
188 UNPH Unknown (Philippines) Philippines<br />
189 UNRD Unknown red rice<br />
190 VGLD Vegold Arkansas Cl 9386<br />
191 VSTA Vista Louisiana Cl 12346<br />
192 ZNTH Zenith Arkansas Cl 7787<br />
193 10-7 10-7 California<br />
194 70-6526 70-6526 California<br />
195 723761 723761 California<br />
196 7232278 7232278 California<br />
197 73221 73221 California<br />
198 74-Y-89 74-Y-89 California<br />
199 83-Y-45 83-Y-45 California<br />
200 487A1-12 487A1-12 California<br />
201 13-D 2457-13D Louisiana<br />
R E FEREN C ES<br />
CAAS (Chinese Academy o f Agricultural Science), 1986. Chinese <strong>Rice</strong> Science (in<br />
Chinese). Agricultural Publishing House, Beijing, 746 pp,<br />
Chang, T. T. 1985. Preservation of crop germplasm. Iowa State J. Res. 59:365-378.<br />
Chang T. T., Y. S. Dong, R. S. Paroda, <strong>and</strong> C. S. Ying. 1987, International collaboration<br />
on conservation, sharing <strong>and</strong> use o f rice germplasm. In Irrigated <strong>Rice</strong> Research.<br />
International <strong>Rice</strong> Research Institute, Manila, The Philippines, pp. 325-337.<br />
Cox, T. S., Y. T. Kiang, M . B. Gorm an, <strong>and</strong> D. M . Rodgers. 1985. Relationship between<br />
coefficient o f parentage <strong>and</strong> genetic similarity indices in the soybean. Crop Sei<br />
24:529-532.<br />
Darrah, L. L., <strong>and</strong> M. S. Zuber. 1986.1985 United States farm maize germplasm base<br />
<strong>and</strong> commercial breeding strategies. Crop Sei 26:1109-1113.<br />
Delannay, X., D. M. Rodgers, <strong>and</strong> R. G, Palmer. 1983. Relative genetic contributions<br />
among ancestral lines to North American soybean cultivars. Crop Sei 2 3 :9 4 4 -<br />
949.<br />
Dilday, R. H. 1990. Contribution o f ancestral lines in the development of new cultivars<br />
o f rice. Crop Sei 30(4):905-911.<br />
Dilday, R. H., K. A. Moldenhauer, J. D. Mattice, F. N. Lee, R L. Baldwin, J. L. Bernhardt,<br />
D. R. Gealy, A. M . McClung, S. D. Linscombe, <strong>and</strong> D. M. Wesenberg. 1999. <strong>Rice</strong><br />
germplasm evaluation <strong>and</strong> enhancement at the Dale Bumpers National <strong>Rice</strong> Research<br />
Center, In Proceedings o f the International Symposium on <strong>Rice</strong> Germplasm<br />
Evaluation <strong>and</strong> Enhancement. Ark. Agric. Exp. Stn. Spec. Rep. 195, pp. 16-21,<br />
Goli, A. E. 1986. Plant Exploration in Cameroon. International Institute o f Tropical<br />
Agriculture, Ibadan, Nigeria, 23 pp.<br />
Goli, A. E. 1987a. Plant Exploration in Congo. International Institute o f Tropical Agriculture,<br />
Ibadan, Nigeria, 29 pp.
624 Germplasm Resources<br />
llit:<br />
ti<br />
iili<br />
i?-iiili<br />
Goli, A. E. 1987b. Plant Exploration in Malawi. International Institute o f Tropical<br />
Agriculture, Ibadan, Nigeria, 18 pp.<br />
Goli, A. E. 1987c. Plant Exploration in Senegal. International Institute of Tropical<br />
Agriculture, Ibadan, Nigeria, 27 pp.<br />
Goli, A. E. 1987d. Plant Exploration in Zambia. International Institute o f Tropical<br />
Agriculture, Ibadan, Nigeria, 16 pp.<br />
Goli, A. E., <strong>and</strong>N. Q, Ng. 1985. Plant Exploration in Central African Republic, October-<br />
December 1985, International Institute o f Tropical Agriculture. Ibadan, Nigeria,<br />
26 pp.<br />
IBPGR. 1984. Annual Report for 1983. International Board for Plant Genetic Resources.<br />
Rome.<br />
IBPGR. 1985. Annual Report for 1984. International Board for Plant Genetic Resources.<br />
Rome.<br />
IBPGR, 1986. Annual Report for 1985. International Board for Plant Genetic Resources,<br />
Rome.<br />
IBPGR. 1987, Annual Report for 1986. International Board for Plant Genetic Resources.<br />
Rome.<br />
■<br />
IBPGR. 1988. Annual Report for 1987. International Board for Plant Genetic Resources.<br />
Rome.<br />
IRRI. 1988. <strong>Rice</strong> Facts, 1988. International <strong>Rice</strong> Research Institute, Manila, The Philippines.<br />
IRRI. 1991. <strong>Rice</strong> Germplasm Collecting, Preservation, Use. International <strong>Rice</strong> Research<br />
Institute. Manila, The Philippines.<br />
Morishima, H., Y, Shinamoto, Y. Sano, <strong>and</strong> Y. I. Sato. 1984. Observations on Wild <strong>and</strong><br />
Cultivated <strong>Rice</strong>s in Thail<strong>and</strong> for Ecologial-Genetic Study: Report of Study Tour in<br />
1983. Contribution 1621. National Institute o f Genetics, M ishima, Japan, 86 pp.<br />
Murphy, C. R 1981. The National Plant Germplasm System. Special unnumbered SEA-<br />
USDA Report. U.S. Department o f Agriculture, Washington, DC.<br />
NAS. 1972. Genetic Vulnerability of Major Crops, National Academy o f Sciences, Com <br />
mittee on Genetic Vulnerability of M ajor Crops, Washington, DC.<br />
National Institute of Genetics. 1987. Trip to Indonesia <strong>and</strong> Thail<strong>and</strong> for the Ecological<br />
Genetic Study in <strong>Rice</strong>: Report of Study-Tour in 1985/86. Contribution 1729.<br />
National Institute of Genetics, M ishima, Japan, 75 pp.<br />
Ng, N. Q., M , Jacquot, A. Abifarin, K. Goli, A. Ghesquiere, <strong>and</strong> K. Miezan. 1983. <strong>Rice</strong><br />
germplasm collection <strong>and</strong> conservation in Africa <strong>and</strong> Latin America. In 1983<br />
<strong>Rice</strong> Germplasm Conservation Workshop. International <strong>Rice</strong> Research Institute,<br />
Manila, The Philippines, pp. 45-52.<br />
Osunmaldnwa, A. A. 1986. Report on Plant Exploration in the Republic of Mali. International<br />
Institute of Tropical Agriculture, Ibadan, Nigeria, 18 pp.<br />
Otto, H. J. 1985. Plant Germplasm Preservation <strong>and</strong> Utilization in U.S. Agriculture.<br />
Counc. Agric. Sei. Technol. Rep. 106.<br />
Padulosi, S. 1987a. Plant Exploration <strong>and</strong> Germplasm Collection in Chad. International<br />
Institute o f Tropical Agriculture, Ibadan, Nigeria, 46 pp.<br />
Padulosi, S. 1987b. Plant Exploration <strong>and</strong> Germplasm Collection in Tanzania.. International<br />
Institute o f Tropical Agriculture, Ibadan, Nigeria, 32 pp.<br />
Padulosi, S. 1987c. Plant Exploration <strong>and</strong> Germplasm Collection in Zimbabwe. International<br />
Institute o f Tropical Agriculture. Ibadan, Nigeria, 32 pp.
Germplasm Coilecfion, Preservolion, <strong>and</strong> Ulilization 625<br />
Padulosi, S. 1988. Plant Exploration <strong>and</strong> Germplasm Collection in Somalia. International<br />
Institute o f Tropical Agriculture. Ibadan, Nigeria.<br />
Rodgers, D. M ., J. P. Murphy, <strong>and</strong> K. J. Frey. 1983. Im pact o f plant breeding on the<br />
grain yield <strong>and</strong> genetic diversity o f spring oats. Crop Sei 23;737~740.<br />
Sm ith ,}. S. C. 1988. Diversity o f United States hybrid maize germplasm: isozymic <strong>and</strong><br />
chromatographic evidence. Crop Sei 28:63-69.<br />
Specht, J. E., <strong>and</strong> J. E. Williams. 1984. Contribution o f genetic <strong>technology</strong> to soybean<br />
productivity: retrospect <strong>and</strong> prospect. In W. R. Fehr (ed.), Genetic Contributions<br />
to Yield Gains of Five Major Crop Plants. CSSA Spec. Publ. 7. ASA-CSSA, M adison,<br />
W I, pp. 49-74.<br />
St. M artin, S. K. 1982. Effective population size for the soybean improvement program<br />
in m aturity groups 00 to IV. Crop Sei 22:151-152.<br />
Vodouhe, S. R., C. H. G. YaHou, G. N. Maroya, <strong>and</strong> N. Q. Ng. 1990. Germplasm Exploration<br />
in the Republic of Benin, International Institute o f Tropical Agriculture,<br />
Ibadan, Nigeria, 40 pp.<br />
Walsh, J. 1981. Genetic vulnerability down on the farm. Science (Washington, D.C.)<br />
214:161-164.<br />
Wesenberg, D. M ., L. W. Briggle, <strong>and</strong> D. H. <strong>Smith</strong>. 1992. Germplasm collection,<br />
preservation, <strong>and</strong> utilization. In H. G. Marshall <strong>and</strong> M. E. Sorrells (eds.). Oat<br />
Science <strong>and</strong> Technology. ASA-CSSA, Madison, W I, pp. 793-820.
Index<br />
AAA, see Agricultural Adjustment<br />
Act of 1933; Agricultural<br />
Adjustment Administration<br />
Abscisic add, 143<br />
Acephate, 449<br />
Acid soils, 361<br />
Acifluorfeu, 466<br />
Active tillering, 119<br />
Adair, C. Roy, 601<br />
ADP-glucose pjTophosphorylase<br />
(AGP), 142-143<br />
Adventitious roots, 109<br />
Aeration;<br />
controlled ambient, 561<br />
of soils, 115,116,120, 309-312<br />
of stored rice, 550—553<br />
Aerencltyma, 138<br />
Aerobic conditions:<br />
for germination, 115,116<br />
for seedling development, 117<br />
Aerosols (insect control), 560<br />
AESs, see Agiicultural Experiment<br />
Stations<br />
AFLP, see Amplified fragment<br />
length polymorphism<br />
Africa. See also specific countries<br />
germplasm resources in, 607-608<br />
O. seitiva complex in, 50-52<br />
rice producing hectares in, 4<br />
African rice fO. g la b e n im a j, 4,12<br />
diversification of Asian rice vs.,<br />
17-18<br />
as part of O. sativa complex, 88<br />
AGCO-MF combines, 513,537<br />
Aggregate sheath spot, 422<br />
AGP, see ADP-glucose<br />
pyrophosphorylase<br />
Agriailtiiral Adjustment Act (AAA)<br />
of 1933,81,475<br />
Agricultural Adjustment Act of<br />
1938, 475<br />
Agricultural Adjustment<br />
Administration (AAA), 81,<br />
82<br />
Agricultural Experiment Stations<br />
(AESs), 80, 599. S ee a/so<br />
specific stations<br />
Agricultural Marketing Act of 1929,<br />
81<br />
Agricultural Research Service,<br />
USDA, see U.S. Department<br />
of Agriculture-<br />
Agricultural Research<br />
Service<br />
Agriculture, inception of, 68<br />
A g ro b a cterh m -ta ed iiitsd transfer,<br />
209<br />
Agroeoosystems of rice <strong>production</strong>,<br />
14,15<br />
Agronomic traits, 96-97,179-182<br />
Akagare disease, 147<br />
A kiochi, 432<br />
Aleurone layer, 112,113<br />
Alfisols, 298,319<br />
ALH, see Aster leafhopper<br />
Alkaline soils, 385-386<br />
Alkaline soil management, 395-398<br />
on calcareous soils, 396-397<br />
on sodic soils, 397-398<br />
Allialinity damage, 431<br />
Alkali spreading value (ASV), 189,<br />
191<br />
AUelodiemicals, 221-239<br />
bioassays, 231-233<br />
mechanisms of action, 236-238<br />
rice allelopathy research, 222-236<br />
secondary metabolites<br />
identification, 222,<br />
224-231<br />
systematic isolation of, 233-236<br />
A h ern aria leaf spot, 426<br />
Amazon weed, 459<br />
American <strong>Rice</strong>, Inc., 82<br />
American <strong>Rice</strong> Growers<br />
Cooperative Association, 81<br />
American rice industry, 67-84<br />
<strong>and</strong> British Navigation Acts,<br />
69-70<br />
in early colonial times, 69-70<br />
<strong>and</strong> piracy, 70<br />
post-World War II, 81-84<br />
<strong>and</strong> tidal flow water cultivation<br />
system, 70-71<br />
<strong>and</strong> tidal-powered rice mill,<br />
71-72<br />
from 1750 to 1850,70-72<br />
from 1850 to 1880,73,74<br />
from 1880 to 1900,73,75-78<br />
from 1900 to 1945,78-81<br />
AmericiUi wild rice, vii<br />
Amino acids, 146<br />
Ammonia volatilization, 333,<br />
335-337,341<br />
Ammonium, 333<br />
Ammonium fixation, 339-340<br />
Aminoiihim sulfate, 341-342,375,<br />
378<br />
Amplified fragment length<br />
polymorphism (APLP), 162,<br />
206<br />
Amylose content, 189<br />
Anaerobic conditions:<br />
for germination, 116<br />
for seedling development, 117<br />
Angle:<br />
culm, 109<br />
leaf, 106<br />
Angoumois grain moth, 557-558<br />
Anhydrous ammonia, 341-343<br />
Annual rices;<br />
Asian, 49<br />
weedy rices a.s, 55<br />
Anoxic soils, 316<br />
Antlier culture, 192-193,208-209,<br />
442-443<br />
Antlier deliiscence (pollen shed),<br />
124<br />
Anthesis (flowering), 120,123-124<br />
Antifungal genes, 433<br />
Apical meristem, 112<br />
Apomixis, 169<br />
Aqua ammonia, 341-343<br />
Aquatic weeds, 459,462<br />
Arborio rice, 192<br />
Argentina, 485-487<br />
Argillic soil horizon (t), 302-303<br />
Arkansas, vii<br />
delivery points in, 480<br />
early rice <strong>production</strong> in, 78-79<br />
grain types grown in, 289<br />
growers <strong>and</strong> millers associations<br />
in, 31<br />
rice <strong>production</strong> in, viii<br />
627
628<br />
Index<br />
W ‘i<br />
Arkansas {con tín u ed}<br />
soils in, 299<br />
USDA-ARS in, 178<br />
Arkansas Agricultural Experiment<br />
Station, 79<br />
Armywonn (AW), 444—445<br />
Aromatic rice cultivars, 191<br />
Arrosolo, 469<br />
Arrowhead weeds, 459<br />
Arsenic induced straiglithead, 432<br />
Arthropod pests, 437-451. See also<br />
Insects<br />
armyworms, 444-445<br />
chinch bugs, 445—446<br />
crayfish, 450<br />
grape colaspis, 449<br />
leafhoppers, 448,449<br />
<strong>and</strong> rice entomologists, 450-451<br />
rice leaf miners, 447<br />
rice seed midges, 446-447<br />
rice stem borers, 447-448<br />
rice stink bug, 443-444<br />
rice water weevil, 438,440-443<br />
tadpole shrimp, 449-450<br />
Aryl acyl anúdase, 461<br />
Asia. S ee also specific countries<br />
O. srtiiV« complex in, 35-40<br />
rice combine harvesters in,<br />
518-524<br />
rice producing hectares in, 4<br />
weedy rices in, 56<br />
Asian rice (0 . sativa)) 4,12-13<br />
different species names of, 48<br />
diversification of African rice vi,,<br />
17-18<br />
historic writings about, 7<br />
indica subspecies of, 88-89<br />
japónica subspecies of, 88-89<br />
as part of O, sativa complex, 88<br />
phytosanitary import restrictions<br />
on, 485, 496<br />
subspecies of, 88-89<br />
Aster leafliopper (ALH), 448,449<br />
ASV, see Alkali spreading value<br />
Atmospheres, controlled, 560<br />
Auricles, 107<br />
Australia, 485,499<br />
Calrose cultivar as basis for, 98<br />
O. sativa complex in, 52-53<br />
rice trash problems in, 514<br />
strippeiiiead test in, 508<br />
Auxins, 143<br />
AW, see Armyworm<br />
Tlxial-flow combines, 498<br />
Bacterial artificial chromosome<br />
(BAG) library, 206<br />
Bacterial blight, 426<br />
Bacterial diseases, 419,431<br />
Bacterial streak, 427<br />
Bakanae (foot rot), 419<br />
Bambusoideae subfamily, 29<br />
Bangladesh, vii, 247, 487<br />
Bamjaudgrass, 227-229,232,459,<br />
461<br />
Basmati rice, 88,191<br />
Bays, 274<br />
Bearded sprangietop, 459<br />
Beer making, rice used in, 481,482,<br />
546<br />
Beijing Combine Harvester General<br />
Works; combine. 518<br />
Bensiilfuron, 462, 463, 466, 467<br />
Bciitazon, 285,463, 466, 467<br />
EFL, see Blackfaced leafliopper<br />
Bioassays, 231-233<br />
Biogeography of rice, 7-8<br />
Biological control:<br />
of diseases, 434<br />
of rice water weevils, 443<br />
Bio<strong>technology</strong>, rice, 204r-213<br />
conventional, 207-208<br />
ñiture prospects in, 212-213<br />
<strong>and</strong> genetic engineering, 207,<br />
209-212<br />
genome analysis, 205-207<br />
<strong>and</strong> rice as model system, 205<br />
Rockefeller Foundation program<br />
on, 204<br />
tissue culture/transformation,<br />
208-209<br />
Bispyribac, 463,464,467<br />
Blackfaced leafliopper (BFL), 448,<br />
449<br />
Blade kernel, 372,430<br />
Black sheath rot, 422<br />
Blade, leaf, see Leaf blade<br />
Blast, 423-424<br />
Blast resistance, 182-184<br />
Bluebonnet cultivar, 91,94,179<br />
Blue Rose cultivar, 95<br />
Bockelman, H. E., 601<br />
Bonnet cultivars, 94, 97<br />
Booting stage, 123, 347-348<br />
Bordages, Louis, 76<br />
Brakes, 568<br />
Bran, rice, 113,568,569<br />
Brassi no steroids, 143<br />
Brazil, 485, 487<br />
Brazos cultivar, 95<br />
Breeding, 87. See also specific<br />
cultivars<br />
for agronomic traits, 96,179-182<br />
in California, 96-98<br />
for disease resistance, 182-187<br />
for environmental stress<br />
tolerance, 187-188<br />
field testing methods, 194-195<br />
future trends in, 98-99,195-195<br />
for genetic variability, 192<br />
for insect resistance, 187<br />
raetltods of, 192-194<br />
for milling quality, 190<br />
mutation in, 208<br />
objectives of, 178-192,196<br />
of post-1971 released cultivars,<br />
92-95<br />
ofpre-1971 released cultivars,<br />
89-91<br />
for quality components, 188-192<br />
selection in, 104,178-192<br />
state-federal programs for, 479<br />
for threshability, 181<br />
of tropical japónica cultivars,<br />
96-97<br />
U.S. programs for, 178<br />
Brewers, 569<br />
Bridging parents, 193<br />
Brien, Maurice, 75<br />
British Navigation Acts, 69-70<br />
Broadleaf signalgrass, 459<br />
Broadleaf weeds, 233,463<br />
Brokens, 569<br />
Bronzing, 431-432<br />
Brookhaven National Laboratory, 7<br />
Broussard, Joe E., 76<br />
Brown leaf spot, 372<br />
Brown rice. 111, 568-569<br />
Brown sheath rot, 422<br />
Brown spot, 424-425<br />
Bulu cultivars, see Javanica race<br />
Biirndown treatments (weed<br />
control), 464<br />
By-product marketing, 484<br />
Calcareous soils, 396-397<br />
Calcic horizon (k), 303<br />
California, vii<br />
breeding program in, 96<br />
crop rotation in, 290<br />
early rice <strong>production</strong> in, 80-81<br />
grain types grown in, 289<br />
herbicides used in, 462<br />
long-grain cultivars developed<br />
for, 94-95, 97-98<br />
medium-grain cultivars in, 95, 98<br />
mutant cultivars in, 164-t 65<br />
rice <strong>production</strong> in, viii<br />
salinity problems in, 389<br />
short-grain cultivars in, 98<br />
soils in, 301<br />
USDA-ARS in, 178<br />
California Agricultural Experiment<br />
Station, 80<br />
Call options, 480, 481<br />
Callotvay soils, 319,320-322<br />
Caloro cultivar, 95, 98<br />
Calrose cultivar, 98<br />
Calrose 76 mutant, 164-165,168<br />
Canada, 485, 487<br />
Canals, 78, 274<br />
Canopy architecture, 121<br />
Carbamate, 445<br />
Carbaiyl, 444,446,449,450<br />
Carbomate, 461<br />
Carbon dioxide, 309-310,326<br />
Carbon path (in endosperm), 139,<br />
142-145
Index 629<br />
Carfentrazone, 467<br />
Carolina colonies. 69<br />
Carolina Gold ciiltivar, vii, 89,<br />
97<br />
Carolina White cnltivar, vii<br />
Carotenoids, 148<br />
Carruthers, Edgar, 76<br />
Cary, S. L. 73<br />
Caryopsis, 111<br />
Case-IH combines, 501,509, 511,<br />
513, 537<br />
Caterpillar, 528<br />
CBs, see Chinch bugs<br />
CCC, see Commodity Credit<br />
Corporation<br />
CCRI, see Central <strong>Rice</strong> Research<br />
Institute<br />
Central America, 4,486. S ee also<br />
specific countries<br />
Centralrachis. 111<br />
Central <strong>Rice</strong> Research Institute<br />
(CCRT), 608,609<br />
Century Patna 231 cultivar, 97<br />
Chambliss, Charles E., 80,81<br />
Chemical composition, mutants<br />
for, 166<br />
Chemical control of diseases,<br />
433-434. See also specific<br />
diseases<br />
Chemical properties of soils,<br />
315-319, 322-326<br />
electrical conductivity, 317-318,<br />
326<br />
oxidation-reduction reactions,<br />
315-317<br />
oxidation-reduction status,<br />
322-325<br />
pH, 317,325-326<br />
soil solution, 318-319,326<br />
CHIAS (CHromosome Image<br />
Analysis System), 162<br />
Chicago Board of Hade, 479,480<br />
China, 68<br />
current rice <strong>production</strong> in, 247<br />
differentiation of ecogenetic<br />
races in, 18<br />
early cultivation of rice in, 67<br />
germplasm resources in, 608<br />
harvesting in, 518,519,522<br />
historic evidence of rice in,<br />
12-13<br />
hybrid rice in, 167<br />
marketing competition with,<br />
485,487<br />
rice <strong>production</strong> in, vii<br />
Chinch bugs (CBs), 445-446<br />
Chinese Academy of Sciences, 60S<br />
Chioroacetamide-type herbicides,<br />
464<br />
Chloropicrin, 559<br />
Chlorpyriphos-methyl, 560<br />
Choppers (combines), 292<br />
Chroma (soil color), 304<br />
Chromosomes:<br />
cytogenetics, 161-164<br />
physical mapping of, 206<br />
CHromosome Image Analysis<br />
System (CHIAS), 162<br />
Chromosome number, 5-6, 31,154,<br />
155<br />
Chung-Pfost equation, 578-579<br />
C (iron-manganese concretions),<br />
303<br />
Cities, cultivation <strong>and</strong>, 67,68<br />
Claas/Caterpillar combines, 510,<br />
511,513<br />
Classification of cnltivars, 88-89<br />
Clay films, 304<br />
Clean Air Act of 1991, 559<br />
Cleaning system (combines),<br />
513-514<br />
Cleaning time (harvesters), 536-537<br />
Clefoxydim, 467<br />
Cletliodim, 465<br />
Clomazone, 461-463,468<br />
Cloning, 206<br />
Closed irrigation systems, 285<br />
Coffeebean, 459<br />
Cold injury, 432<br />
Coleoptile, 109,112, 115-117<br />
Coleorliiza. 112,117<br />
Collar, 107<br />
Collego, 463<br />
Colonial rice trade, 69-70<br />
Color, soil, 304-305<br />
Colusa cultivar, 95,98<br />
Combines, 292<br />
adjustment of, 293<br />
rice-special, see <strong>Rice</strong> combine<br />
harvesters<br />
self-propelled, 493<br />
Commercial dryers, 477-478.<br />
588-590<br />
Commercial warehouses, 477-478<br />
Commodity Credit Corporation<br />
(CCC), 477, 479<br />
Common cocklebur, 459<br />
Common rice, vii. See also Asian<br />
rice<br />
Competition:<br />
in export markets, 435-486<br />
globalization <strong>and</strong>, 249<br />
Computer software (soil chemistry<br />
modeling), 318-319<br />
Condensation pattern<br />
(chromosomes), 162<br />
Conduction, heat, 313-314<br />
Conservation tillage, 286,464<br />
Continental cnltivars, 88<br />
Continental drift, rice dispersion<br />
<strong>and</strong>, 8<br />
Continuous flooding, 281,282,284<br />
<strong>and</strong> red rice control, 465<br />
<strong>and</strong> weed control, 462<br />
Continuous root exudate trapping<br />
system, 231-232<br />
Contracts, rice, 478-479<br />
Control <strong>and</strong> information systems<br />
(harvesting), 541<br />
Controlled ambient aeration, 561<br />
Controlled storage atmospheres,<br />
560<br />
Convective dispersion equation,<br />
312<br />
Convective flow (gases), 311<br />
Conventional tillage, 286<br />
Conveying functions (combines),<br />
517<br />
Cooking quality, 188-190, 564<br />
Cooperatives, 478-480<br />
Cooperative Extension Services,<br />
340<br />
Copper spray, 431^32<br />
Copper sulfate, 449-450<br />
Costa Rica, 485<br />
Cotyledon, 112<br />
Cotyledonary node, 109<br />
Country, rice <strong>production</strong> by,<br />
257-264<br />
Craddock, J. C., 601<br />
Craigmiles, J. P., 82<br />
Crawfi.sh, 290<br />
Crayfish, 450<br />
Crop Advisory Committees,<br />
604-605<br />
Crop dividers (combines), 505<br />
Crop feeding <strong>and</strong> threshing<br />
(combines), 509-512<br />
Crop field loss, 529<br />
Crop improvement programs, vii<br />
Crop insurance, 477<br />
Crop management models, 104<br />
Crop revenue insurance, 477<br />
Crop rotations, 289,290<br />
Cross-flow design (dryers), 589-590<br />
Cross-pollination, 124<br />
Crowley soils, 300,302,319<br />
Crown diseases, 418-419<br />
Crown roots, 109<br />
Crown rot, 419<br />
Crown sheath rot, 422<br />
Culm;<br />
diseases of, 420-423<br />
morphology of, 107-108<br />
Cnltivars. S ee also U.S. rice cnltivars;<br />
specific cnltivars<br />
aromatic, 191<br />
classification of, 88-89<br />
commercial vs. red rice, 459<br />
continental, 88<br />
development of new, 178-196<br />
diversification of, 14-19<br />
insular, 88<br />
introduction to U.S. of, vii<br />
lack of genetic diversity in,<br />
612-623<br />
maturity groups of, 113<br />
mutant, 164
630 Index<br />
Ctiltivars {con tin u ed)<br />
origiiis/ancestral lines of,<br />
619-623<br />
pedigree schematics of, 614-618<br />
selection of, 289<br />
stiff-strawed, 343<br />
time needed to develop, 178<br />
Cultivated rice:<br />
in Asia, 49<br />
development of, 104,113-125<br />
morphology of, 104-113<br />
similarity of weedy rices to, 56<br />
Cttltivation of rice;<br />
changes in plants following, 16<br />
<strong>history</strong> of, 13-14,67-68. S eeaiso<br />
American rice industry<br />
spread of, 14,16<br />
tidal flow water system for, 70-71<br />
Cultural practices:<br />
<strong>and</strong> rice diseases, 433<br />
for rice leaf miner control, 447<br />
for rice seed midge control, 447<br />
for rice water weevil control,<br />
441^42<br />
for weed control, 458<br />
Custom-made rice combine<br />
harvesters, 499-500<br />
Cuts, 274<br />
Cutter bars (combines), 293.<br />
505-506<br />
Cuulong <strong>Rice</strong> Research Institute<br />
(Vietnam), 611-612<br />
Cyanobacteria, 335<br />
Cylialofop, 464, 468<br />
Cypress cultivar, 97<br />
Cytogenetics, 161-164<br />
Cytokiiiins, 143<br />
Dacca Agricultura] Research Station<br />
(India), 608<br />
Dale Bumpers National<br />
<strong>Rice</strong> Research Center<br />
(DBNRRC), 163,605-606<br />
Damping-off, 417<br />
DAP (diammonium phosplutc),<br />
366<br />
Dawn cultivar, 89<br />
DBNRRC, see Dale Bumpers<br />
National <strong>Rice</strong> Research<br />
Center<br />
Deep water agro eco systems, 15<br />
Deere & Co. combines, 501,<br />
511-513, 528, 537<br />
Deficiencies, diagnosis of.<br />
iron, 382-383<br />
manganese, 382-383<br />
phosphorus, 365-368<br />
potassium, 371-373<br />
sulfur. 375-376<br />
zinc, 377-382<br />
Degree days, 118<br />
Degree of milling, 569<br />
Delayed flooding, 281, 282,<br />
284, 460-462. See also<br />
Dry-seeded systems<br />
Delayed phytotoxicity syndrome,<br />
466<br />
Delayed preemergeace application<br />
(herbicides), 461-462<br />
Della cultivar, 94<br />
A-cyhalothiin, 440-441,444,446<br />
Denitrification, 333,335-336<br />
Depredation, 538<br />
Development of rice, 104,113-125<br />
germination, 114-117<br />
growth phases, 113,114<br />
physiology of, 130-131. See also<br />
PhysLolog}' of rice<br />
plant growth rate, 118<br />
reproductive phase, 120-124<br />
ripening phase, 124-125<br />
role of coordinated function in,<br />
130<br />
of roots, 120<br />
of seedlings, 117-118, 131,<br />
133-137<br />
tillering, 119-120<br />
vegetative phase. 113-120<br />
yield components, 113,114<br />
DeWitt soils, 319,357<br />
Diammonium phosphate (DAP),<br />
366<br />
Diatomaceous earth, 560<br />
Diffusion (gases), 311-312<br />
Diflubenzuron, 440,441<br />
Dilday, H. D., 599<br />
Dilday, R. H., 500-601<br />
Dimethenamid, 464<br />
Dinitroanaline lierbicides, 464<br />
Diploid species, 154<br />
Direct food use (processed rice),<br />
481-483<br />
Diseases, 414^34<br />
aggregate sheath spot, 422<br />
akagare disease, 147<br />
alkalinity or salt damage, 431<br />
A ltern aría leaf spot, 426<br />
bacterial blight, 426<br />
bacterial diseases, 431<br />
bacterial streak, 427<br />
bakanae (foot rot), 419<br />
biological control of, 434<br />
black kernel, 430<br />
blast, 423-424<br />
bronzing, 431-432<br />
brown spot, 424-425<br />
chemical control of, 433-434<br />
cold injury, 432<br />
crown rot, 419<br />
crown sheath rot, 422<br />
<strong>and</strong> cultural practices, 433<br />
downy mildew, 430<br />
eye spot, 427<br />
felse smut, 428-429<br />
foliar diseases, 423-428<br />
grain discoloration, 430<br />
head <strong>and</strong> grain diseases, 428-430<br />
<strong>and</strong> host resistance, 433<br />
hydrogen sulfide toxicity, 432<br />
integrated management of,<br />
432-434<br />
kernel smut, 429<br />
leaf scald, 427<br />
leaf smut, 427-428<br />
narrow brown leaf spot, 425-426<br />
nematode diseases, 431<br />
nutrition-related, 146-149<br />
panicle blight, 429-430<br />
pecky rice, 428<br />
<strong>and</strong> plant quarantine, 432-433<br />
resistance to, see Disease<br />
resistance<br />
root <strong>and</strong> crown diseases, 418-419<br />
root knot, 419<br />
root rot, 418-419<br />
seed <strong>and</strong> seedling diseases,<br />
415-418<br />
seedling blight, 417-418<br />
sheath blight, 420-421<br />
sheath rot, 422-423<br />
sheath spot, 423<br />
stem <strong>and</strong> culm diseases, 420-423<br />
stem rot, 421-422<br />
straighthead, 432<br />
viral <strong>and</strong> mycoplasma-like<br />
diseases, 430-431<br />
water mold, 415-417<br />
white leaf streak, 428<br />
white tip nematode, 428<br />
<strong>and</strong> yieldlquality of rice, 414-415<br />
Disease resistance:<br />
breeding for, 182-187<br />
genetic engineering for, 211-212<br />
Dispersion of rice, 8,67-63<br />
Diversification of rice cultivars,<br />
14-19<br />
across five agroecosystems, 14,15<br />
ecogenetic races, 17-19<br />
genetic <strong>and</strong> human forces in, 14,<br />
15<br />
<strong>and</strong> spread of rice cultivation, 14,<br />
16<br />
Dixiebelle cultivar, 94<br />
DNA, see specific species<br />
Domestication of rice, 13,14,16<br />
Domestic rice market (U.S.), 474,<br />
475<br />
Dormancy, 114,115<br />
Downy mildew, 430<br />
Drainage, 284-285<br />
<strong>and</strong> irydraulic conductivity of<br />
soils, 307-309<br />
prior to harvesting, 285<br />
<strong>and</strong> type of soils, 285<br />
Drainage ditches, 274<br />
Drapers (combines), 509<br />
Drilled seeding systems, 283,286<br />
Dry broadcast seeding systems, 286
Index 631<br />
Drying fronts, 591<br />
Drying of rice, 293-294,570-591<br />
commercial dryers, 477-478<br />
equilibrium moisture content,<br />
576-580<br />
<strong>and</strong> issues at harvest, 570-577<br />
milling quality <strong>and</strong> rate of,<br />
580-585<br />
moisture content reduction<br />
during, 583-588<br />
<strong>and</strong> property characterization,<br />
570-574<br />
<strong>and</strong> respiration effects, 575-577<br />
rough rice drying systems,<br />
583-591<br />
Dryl<strong>and</strong>, viii<br />
Dryl<strong>and</strong> agroecosystems, 15<br />
Dry matter losses, 575<br />
Dry-seeded systems, 283-284<br />
nitrogen fertilizer application in,<br />
349-352<br />
nitrogen fertilizers for, 341,342<br />
phosphorus fertilizer application<br />
in, 366<br />
<strong>and</strong> salinity, 389-392<br />
Ducksalad, 221, 459<br />
Duripan (qm), 303<br />
Early-maturing cultivars, 113,180<br />
Early-maturity mutants, 165<br />
Early Prolific cultivar, 95<br />
Ear-neck node, 109<br />
Eating quality, 564<br />
EC, see Electrical conductivity<br />
Eclipta, 459<br />
Ecogene tic races, 17-19<br />
Economic injury level (BIL), 440<br />
Economic performance<br />
(harvesting), 533<br />
Economic thresholds (ETS):<br />
for chinch bugs, 445<br />
for tice stink bugs, 444<br />
for rice water weevils, 440,441<br />
for stem borers, 448<br />
EBP, see Export Enhancement<br />
Program<br />
Efferson, J, Norman, 82-83<br />
Egypt, 485,487<br />
EIL (economic injury level), 440<br />
Electrical conductivity (EC),<br />
317-318,326<br />
El Salvador, 485<br />
Embryo, 112,113<br />
EMC, see Equilibrium moisture<br />
content<br />
Emthomyl, 461<br />
Endosperm, 111, 112,139,142-145<br />
Entomologists, rice, 328,450-451<br />
Enzymes, 129,130,139,142,148<br />
Epidermis, 112<br />
Equilibrium moisture content<br />
(EMC), 552, 576-580<br />
Equilibrium relative humidity<br />
(ERH), 577-578<br />
ET; see Bvapotranspiratioii<br />
Ethylene, 143<br />
Ethyl parathion, 450<br />
BIS, see Economic thresholds<br />
Bui mutant, 166<br />
European Union, 487<br />
Evapotranspiration (E T ), 305-307<br />
Evers, G. W., 82<br />
Evolution;<br />
of O, glaberrim a, 11-12<br />
of O. sativa, 9-11<br />
of weedy rice, 55-57<br />
Exports, rice, vii, 475-476<br />
major countries importing, 485<br />
in mid-1800’s, 73,74<br />
regional statistics for, 250-253,<br />
261,264<br />
by the United States, 68,83-84<br />
Export Credit Guarantee Programs<br />
(GSM), 486<br />
Export Enhancement Program<br />
(EBP), 475, 486<br />
External feeders (insects), 555,558<br />
Eyespot, 427<br />
FAIR, see Federal Agricultural<br />
Improvement <strong>and</strong> Reform)<br />
Act of 1996<br />
Pall army worm (FAW), 444—445<br />
False smut, 428-429<br />
FAO International <strong>Rice</strong><br />
Commission Working<br />
Party on <strong>Rice</strong> Breeding<br />
(1955), 151,158<br />
Farm Act of 1996,477<br />
Farm-scale bins, 547-548<br />
FAS (Foreign v^rkultiiral Service),<br />
82<br />
FAW, see Fall armywonn<br />
PCI (Federal Crop Insurance), 477<br />
Federal Agricultural Improvement<br />
<strong>and</strong> Reform (FAIR) Act of<br />
1996,476,486<br />
Federal Crop Insurance (PCI), 477<br />
Federal Farm Board, 81<br />
Federal Grain Inspection Service<br />
(FGIS), 479<br />
Feeding (combines), 509-512<br />
Fenoxaprop, 463,468<br />
Fenthion, 450<br />
Fertilization, 124<br />
Fertilizers, 332-385<br />
<strong>and</strong> disease control, see specific<br />
diseases<br />
fall application of, 287<br />
iron, 383<br />
manganese, 382-383<br />
nitrogen, 340-359<br />
phosphorus, 361-368<br />
potassium, 369-373<br />
<strong>and</strong> poultry litter, 400<br />
for precision graded soils,<br />
398-400<br />
silicon, 334<br />
sulfur, 375-376<br />
zinc, 377-382<br />
FGIS (Federal Grain Inspection<br />
Service), 479<br />
Fiber-FISH, 162<br />
Pick’s first law, 311<br />
Pick's second law, 312<br />
Field efficiency, 534-536<br />
Field operations management<br />
(harvesting), 533-537<br />
Field testing methods (breeding),<br />
194-195<br />
Fipronil, 440,441,446-449<br />
First tillering, 119<br />
FISH (fluorescence in situ<br />
hybridization), 162<br />
Fissiiring, 572<br />
Five-leaf stage (seedlings), 118<br />
Flag leaf, 106<br />
Flooding:<br />
continuous, 281, 282,284,462,<br />
465<br />
delayed, 281,282,284<br />
<strong>and</strong> need for fertilizers, see<br />
Fertilizers<br />
pinpoint, 281,282,284,438<br />
for red rice control, 465<br />
<strong>and</strong> soil pH, 272<br />
tidal flow, 70-71<br />
water required for, 276<br />
as weed contiol, 188,460-462<br />
winter, for weed control, 287<br />
Flood management, 284-286<br />
Flood-prone agroecosysteins, 15<br />
Florida, vii, 290<br />
Flotation assistance (harvesting),<br />
499, 528-529<br />
Flower, 111. S e e a l s o Spikelets<br />
Flowering (anthesis), 120,123-124<br />
Fluazifop, 465<br />
Flnfenacet-based herbicides, 464<br />
Fluorescence in situ hybridization<br />
(FISH). 162<br />
Flushing, 458<br />
Flush irrigation, 355<br />
Foliage, nitrogen loss from, 338 -339<br />
Foliar diseases, 423-428<br />
Food Security Act (PSA) of 1985,<br />
475<br />
Foot rot, 419,422<br />
Ford Foundation, 33<br />
Foreign Agricultural Service (FAS),<br />
82<br />
For tuna cultivar, 91<br />
Fourier’s law, 314<br />
Pragipan (x), 303<br />
French, David, 76<br />
Front (combines), see Gathering<br />
head (combines)<br />
Fructose, 142
632<br />
I W<br />
FSA (Pood Security Act) of 1985,<br />
475<br />
Fuller, W.H., 79<br />
Fumigants (insect control), 559<br />
Fungi:<br />
diseases caused by, 415-430<br />
hormones produced by, 145<br />
in stored rice, 562-563<br />
Fungicides, 433. S ee also sp ea fic<br />
diseases<br />
Furrow irrigation, 285-286,356<br />
Fusarium sheath rot, 372<br />
Futures trading, 479,430<br />
Gases, soil, see Aeration<br />
Gates, levee, 275-276<br />
Gathering head (combines), 501,<br />
504<br />
GATT, see General Agreement on<br />
Tariffs <strong>and</strong> li'ade<br />
Genes, 129,130<br />
segregation <strong>and</strong> recombination<br />
of, vii<br />
symbols for, 158,161<br />
Gene banks, 57-58<br />
General Agreement on lariffe <strong>and</strong><br />
Trade (GATT), 476-477,<br />
485,486<br />
Genetics, 154^161<br />
chromosome number, 154,155<br />
genomes, 154,155<br />
karyotype, 154,156-160<br />
linkage groups <strong>and</strong> gene symbols,<br />
155,158,161<br />
Genetic diversity;<br />
lack of. 612-623<br />
recent loss in, 19-20<br />
Genetic engineering, 207,209-212.<br />
S ee also Bio<strong>technology</strong><br />
Genetic linkage maps, 205<br />
Genetic male sterile mutants, 166<br />
Genetic transformation, 209<br />
Genetic variability, breeding for,<br />
192<br />
Genomes, 4-6,31,48,154,155<br />
Genome analysis, 205-207<br />
Genomic in situ hybridization<br />
(GISH), 162<br />
Georgia, vii—^viii, 72<br />
Germ, rice, 568<br />
Germination, 113,114-117<br />
anaerobic, 116<br />
physiology of, 131-137<br />
<strong>and</strong> planting temperature, 288<br />
saline conditions during, 393<br />
Germplasm, 598-623<br />
gene banks for, 57-58<br />
regeneration of, 58<br />
U.S. National Plant Germplasm<br />
System, 598-607<br />
Germplasm Resources Information<br />
Network (GRIN), 602, 606,<br />
614<br />
G (gleyed), 303<br />
Gibbercilic acid, 145-146, 417, 419<br />
Gibberellins, 143, 419<br />
GISH (genomic in situ<br />
hybridii'.ation)i 162<br />
Gleaner combines, 513<br />
Gleyed (g), 303<br />
Global marketing, 249<br />
Global rice <strong>production</strong>, 247-269.<br />
See also specific countries<br />
by country, 257-264<br />
milled yield/milling rate, 264,<br />
266-269<br />
by regions, 249-257<br />
rice area harvested, 258, 261-266<br />
Glucose, 142<br />
Glufosinate, 465, 466,468-469<br />
Glufosinate resistance, 460,<br />
465-466<br />
Glyphosate, 464-466, 469<br />
Glyphosate resistance, 211, 460,<br />
465-466<br />
Golden rice, 204, 210<br />
Gold hull mutants, 166<br />
Gondwana, 4, 7-8<br />
Government-assisted exports,<br />
475-476<br />
Grades (of rough rice), 479<br />
Grain, 111-113<br />
breeding for appearance of,<br />
190-191<br />
development of, 139<br />
discoloration of, 430<br />
diseases of, 428^30<br />
quality of, see Quality<br />
types of, 289<br />
Grain blight, 429^30<br />
Grain borers, 555, 556<br />
Grain coolers, 561<br />
Grain elevators, 548-550<br />
Grain-filling phase, see Ripening<br />
phase<br />
Grain-ripening process, 124-125<br />
Granular ammonium sulfate, 341<br />
Granular carbofuran, 440<br />
Grape colaspis, 449<br />
Grass control, 463-464<br />
Great Depression, 81<br />
Green revolution, 19,20,104,420,<br />
430<br />
Green ring, 347<br />
GRIN, see Germplasm Resources<br />
Information NeUvork<br />
Grotli, D., 600<br />
Growth. S ee also Development of<br />
rice<br />
allelopathic compounds <strong>and</strong><br />
inhibition of, 224, 225<br />
duration of, 96,113<br />
effects of soluble salts on,<br />
392-394<br />
phases of, 113,114<br />
rate of, 118<br />
GSM (Export Credit Guarantee<br />
Programs), 486<br />
Guangdong Academy of<br />
Agricultural Sciences,<br />
608<br />
Guatemala, 485<br />
Guerard, Peter Jacob, 69<br />
Guyana, 485, 486<br />
Ilaage <strong>and</strong> Schmidt, 600<br />
Half-inch elongation stage, 122<br />
Halosulfuron, 463,466, 469<br />
Hard dough stage, 124<br />
Harvesters, 75. See also Combines;<br />
<strong>Rice</strong> combine harvesters<br />
Harvesting, 291-294, 493-542<br />
<strong>and</strong> breeding for threshability,<br />
181<br />
ajid combine functions, 501-504<br />
control <strong>and</strong> information systems<br />
for, 541<br />
custom-made combines for,<br />
499- 500<br />
drying issues at, 570-577<br />
field drainage prior to, 285<br />
field operations management<br />
during, 533-537<br />
global area harvested, 258,<br />
261-266<br />
<strong>and</strong> grain quality, 531-533<br />
measuring/reduclng losses<br />
during, 528-531<br />
milling quality issues at, 570-577<br />
<strong>and</strong> need for rioe-special<br />
combines, 496-499<br />
<strong>and</strong> operation of combines,<br />
504-518<br />
power threshers for, 520-528<br />
private equipment ownership vs.<br />
contracting for, 537-541<br />
quality issues in, 570-577<br />
timing of, 494-496<br />
tractioii/flotation assistance for,<br />
528-529<br />
<strong>and</strong> trash, 514-516<br />
<strong>and</strong> types of rice combines,<br />
500- 501<br />
Head diseases, 428-430<br />
Header (combines), see Gathering<br />
head (combines)<br />
Heading, 123<br />
Head rice yield (HRY), 563-564,<br />
569-570, 572,573, 581-588<br />
Heating (insect control), 561<br />
Heat treatment (germination), 114,<br />
115<br />
Height, 96<br />
breeding for, 179<br />
culm, 109<br />
Hemp sesbannia, 459<br />
Henderson, M. T, 163<br />
Herbicides, 458. See also Weed<br />
conti'ol; specific herbicides
Index 633<br />
drainage for application of, 285<br />
for winter vegetation control, 287<br />
Herbicide resistance, 57,211<br />
Hidden hunger, 367<br />
H id eri a o d a ch i straighthead, 147<br />
High-yielding varieties (HYVs),<br />
104. See also Green<br />
revolution<br />
History;<br />
of ciiltivars, 89-96<br />
of induced mutation, 164<br />
of O ryza,2S<br />
of rice cultivation, 13-14<br />
of rice industry, see American<br />
rice industry<br />
Hogan, Joseph T„ 82<br />
Hoja Blanca, 430<br />
Honduras, 485<br />
Honduras rice, vii, 79,80<br />
Horizontal resistance (to blast), 424<br />
Hormones, 143,145-146<br />
Host resistance (disease control),<br />
424,433<br />
Hotspots, 558<br />
HRY, see Head rice yield<br />
Hsien (sen) rice, 18<br />
Hubei Academy of Agricultural<br />
Sciences, 608<br />
Hue (soils), 304<br />
Hull, 111,568<br />
Humans;<br />
importance of rice to, 4<br />
role of, in diversification of<br />
cultivars, 14<br />
Hybridization, 167-169<br />
fluorescence in situ, 162<br />
genomic in situ, 162<br />
of indica <strong>and</strong> japónica, 89,98-99<br />
naturally occurring, 45<br />
researcli on, 163<br />
of wild <strong>and</strong> cultivated rice, 56,88<br />
Hydraulic conductivity, 307-309<br />
Hydraulic properties of soils, 319<br />
Hydrogen sulfide injury, 285<br />
Hydrogen sulfide toxicity, 432<br />
Hysteresis effect, 578<br />
HYVs (high-yielding varieties), 104<br />
lARI, 609<br />
IBPGR, see International Board for<br />
Plant Genetic Resources<br />
ICAR, see Indian Council of<br />
Agricultural Research<br />
IITA (International Institute of<br />
Tropical Agriculture), 607<br />
Imazethapyr, 447,465,466,469<br />
Imazethapyr resistance, 465-466<br />
Inidzetliopry, 463<br />
Iinidazolinoiie resistance, 211,460<br />
Importers of U.S. rice, 83-84<br />
Improvement of rice, germplasm<br />
in. 612-623<br />
In-bin, batch system drying, 590<br />
Inceptisols, 298<br />
Independent marketing agencies,<br />
478<br />
India, 68,485, 487<br />
current rice <strong>production</strong> in, 247<br />
germplasm resources in, 608-609<br />
historic evidence of rice in, 12<br />
I'icc <strong>production</strong> in, vii<br />
Indian Agricultural Research<br />
Institute, 609<br />
Indian Council of Agricultural<br />
Research (ICAR), 608, 609<br />
Indian patna type cultivars, 97<br />
Indica subspecies (race), 18.19,47,<br />
48,88-89,95-97<br />
Indira G<strong>and</strong>hi Vishva Vidyalaya<br />
(India), 609<br />
Indonesia, vii, 247,487<br />
Induced mutations, 164-166,208<br />
Inekctonc, 230,238<br />
Information processing (in plant),<br />
143,145-146<br />
Injury;<br />
cold, 432<br />
hydrogen sulfide, 285<br />
salinity, 393-394,431<br />
Inorganic pliospliorus, 350<br />
INSA (National Institute for<br />
Agricultural Sciences), 612<br />
Insects. See also Arthropod pests<br />
damage from, during storage,<br />
555-558<br />
extenraf feeders, 555, 558<br />
internal feeders, 555-558<br />
protection from, during storage,<br />
559-562<br />
Insecticides, 285. S ee also specific<br />
insecticides<br />
Insect resistance:<br />
breeding for, 187<br />
genetic engineering for, 211<br />
Institue de Recherdies<br />
Agronomiqiies 'ffopicales ei<br />
des Cultures (IRAT), 607,<br />
609<br />
Insular cultivars, 88<br />
Insurance, ciop/crop revenue, 477<br />
Integrated disease management,<br />
432-434<br />
Integrated pest management,<br />
561-562<br />
Intermediate-maturing cultivars,<br />
U3<br />
Internal feeders (insects), 555-558<br />
International Board for Plant<br />
Genetic Resources (IBPGR),<br />
607,610<br />
International germplasm resources,<br />
607-612<br />
International Hybrid <strong>Rice</strong><br />
Symposium, 167,168<br />
International Institute of Hopical<br />
Agriculture (IITA), 607<br />
International marketing, 486-487<br />
International <strong>Rice</strong> Gene bank (IRG),<br />
610, 611<br />
International <strong>Rice</strong> Genome<br />
Sequencing Project, 196<br />
International <strong>Rice</strong> Research<br />
Institute (IRRI), 6<br />
allelopathic activity test at,<br />
221-222<br />
<strong>and</strong> axial-flow thresher<br />
development, 523-525<br />
bio<strong>technology</strong> sponsored by, 204<br />
collection/conservation of<br />
traditional cultivars by, 19,<br />
20<br />
establishment of, S3<br />
genebankat, 610-611<br />
<strong>and</strong> germplasm research,<br />
607-612<br />
research using Oryza gene pool<br />
at, 163<br />
stripper-gatherer developed at,<br />
519<br />
Internodes, 104-105,108,121<br />
Iran, 487<br />
Iraq, 487<br />
IRAT, see Institue de Recherdies<br />
Agronomiqiies Tropicales et<br />
des Cultures<br />
IR8 cultivar, 96<br />
IRG, see International <strong>Rice</strong><br />
Genebank<br />
Iron, 138,382-383<br />
deficiendes in, 212<br />
diagnosis of deficiency in,<br />
382-383<br />
fertilizing with, 383<br />
forms <strong>and</strong> behavior of, 382<br />
improving content/iiptake of,<br />
210<br />
in soil iiuti’ition, 382-383<br />
Iron-man gánese concretions (c),<br />
303<br />
Iron oxides, 326<br />
Irradiation, 560-561<br />
IRRI, see International <strong>Rice</strong><br />
Research Institute<br />
Irrigated wetl<strong>and</strong> agroecosysteras,<br />
15<br />
Irrigation. S ee a b o Flooding<br />
dosed systems of, 285<br />
Hush, 355<br />
furrow, 285-286, 356<br />
in 19th century, 78<br />
quality of water for, 277-278<br />
<strong>and</strong> salinity/alkalinity of soil, 385<br />
sprinlder, 285, 355<br />
in the United States, 277<br />
water management for, 284-286<br />
water quality for, 387-388<br />
water temperature for, 287-279<br />
water volume for, 279<br />
Irrigation canals, 274
634 Index<br />
:li :<br />
IR36 cultivar, 161<br />
Japan:<br />
germplasm resources in, 609-610<br />
Jiarvcsting in, 518-520<br />
marketing competition with,<br />
485,487<br />
rice culture in, 18<br />
Japanese premium-quality rice, 192<br />
Japónica subspecies (race), 18,19,<br />
88-89<br />
in California, 95<br />
long-grain pedigrees from, 91<br />
nomenclature confusion with,<br />
47,48<br />
yield of, 96-97<br />
Jasmine 85 cultivar, 89<br />
Jasmonic acid, 143<br />
Javanica race, 18,19,88<br />
Jeypore Botanical Survey, 609<br />
Jodou, N. E„ 158<br />
Johnson, L E., 82<br />
Johnstone, Mckewn, 71<br />
Jointvetch, weed control for, 463<br />
Jones, Jenkiti W., 82<br />
Karyotype,6,154,156-160<br />
K (calcic horizon), 303<br />
KCl (potassium chloride), 370<br />
Keng rice, 18<br />
Kernel, 569-574. See a h o Grain<br />
Kernel smut, 429<br />
Key-stop, 517<br />
Kihara, H., 609<br />
Kimbriel, Rex L., 82<br />
Kiuslni (Kyushu) rice, vii, 78,80<br />
Km (petrocalcic horizon), 303<br />
Knapp, Seaman A., vii, 76, 78, 79,<br />
599,600<br />
Knockout mutants, 166<br />
Kokuho Rose cultivar, 95<br />
Kyushl rice, see Kiushu rice<br />
tabelle cultivar, 94<br />
LaGme cultivar, 94<br />
LAI (leaf area index), 133<br />
Lamina, see Leaf blade<br />
L<strong>and</strong> forming, see Precision graded<br />
soils<br />
L<strong>and</strong> leveling, 272-274,306<br />
L<strong>and</strong> selection, 272-276. S ee also<br />
SoU(s)<br />
Laser <strong>technology</strong> (water leveling),<br />
274<br />
Late-maturing ciiltivars, 113,180<br />
Latin America, 31,43-46,485,486<br />
LDP (loan deficiency payment),<br />
479<br />
Leaching (of nitrogen), 333, 337,<br />
338<br />
Leaching requirement (LR),<br />
394-395<br />
Leaf(-ves), 104-107,110<br />
growth rate <strong>and</strong> initiation of, 1)8<br />
nitrogen in, 146<br />
during reproductive phase, 121<br />
during seedling development,<br />
117-118<br />
tiller, 109<br />
true, 117,118<br />
during vegetative phase, 113-114<br />
Leaf angle, 106<br />
Leaf area index (LAI), 133<br />
Leaf blade (lamina), 105,106<br />
Leafhoppers, 448,449<br />
Leaf miners, rice, 447<br />
Leaf scald, 427<br />
Leaf sheath, 105-106,109<br />
Leaf smut, 427-428<br />
leased equipment, 537-541<br />
Leboniiet cultivar, 94, 97<br />
L eersia, 29, 30<br />
Lemma, 111<br />
Lemont cultivar, 97,179,349<br />
Leonard Seed Co„ 600<br />
Lesser grain borer, 555,556<br />
Lettuce, 234<br />
Levees, 274-276<br />
Levee gates, 275-276<br />
Leveling;<br />
of l<strong>and</strong>, 272-274,306<br />
water leveling, 273-274<br />
Lifters (combines), 509<br />
Light green hull mutants, 166<br />
Light (seedling development), 117,<br />
133<br />
Ligule, 106,107<br />
Linkage groups, 155,158<br />
Loan deficiency payment (LDP),<br />
479<br />
Lodged materials, 499<br />
Lodging resistance, 179<br />
Lodicules, 111<br />
Long-grain cultivars, 289<br />
aromatic, 191<br />
for California, 97—98<br />
germplasm pool of, 96-97<br />
grain quality of, 97<br />
<strong>history</strong> <strong>and</strong> characteristics of,<br />
90-95<br />
prices for, 482<br />
released post-1972, in U.S., 92-94<br />
released pre-1972, in U.S., 89-91<br />
Loss, harvesting, 528-531<br />
Louisiana, vii<br />
crop rotation in, 289<br />
early rice <strong>production</strong> in, 73,<br />
75-79,81<br />
grain types grown in, 289<br />
growers <strong>and</strong> millers associations<br />
in, 81<br />
immigration to, 75<br />
rice <strong>production</strong> in, viii<br />
salinity problems in, 389<br />
soils in, 300<br />
Louisiana Farm Bureau Marketing<br />
Association, 478<br />
Louisiana Purchase Exhibit of 1904,<br />
600<br />
Lowl<strong>and</strong> rice, vii<br />
LR, see Leaching requirement<br />
L-200 series cultivars, 95,97—98<br />
Lucas, Jonathan, 71, 72<br />
Lundberg Family Farms, 561<br />
Lycosid spiders, 449<br />
M. W. Johnson Seed Co., 600<br />
Mackie, William W., 80<br />
Macropores, 309<br />
Main culm, 108,109<br />
Major l<strong>and</strong> resource areas (MLRAs),<br />
298,326<br />
Malathion, 560<br />
Malaysia. 519,538, 610<br />
Malaysian Agricultural Research<br />
<strong>and</strong> Development Institute<br />
(MARDI),610<br />
Manganese, 382—383<br />
diagnosis of deficiency in, 382,<br />
383<br />
fcrtlliziiig with, 383<br />
forms <strong>and</strong> behavior of, 382<br />
Manganese oxides, 326<br />
Manure, 335<br />
MAP (Market Access Programs),<br />
486<br />
Mapping, see Genome analysis<br />
MARDI (Malaysian Agricultural<br />
Research <strong>and</strong> Development<br />
Institute), 610<br />
Margins, marketing, 484,485<br />
Market Access Programs (MAP),<br />
486<br />
Market classes, 97<br />
Marketing, 473-488<br />
global, 249<br />
international, 486-487<br />
of processed rice, 481-486<br />
of rough rice, 477-481<br />
in United States, 473-486<br />
U.S. rice policy, 475-477<br />
US. supply <strong>and</strong> dem<strong>and</strong><br />
conditions, 473-475<br />
Mars cultivar, 95, 98<br />
Material-other-than-grain (MOG),<br />
497,501,503,504,507,517<br />
Material processing performance<br />
(harvesting), 533<br />
Mature stage, 124<br />
Maturity;<br />
groups, maturity, 113<br />
time to, ISO<br />
MC, see Moisture content<br />
Medium-grain cultivars, 289<br />
grain quality of, 98<br />
<strong>history</strong> <strong>and</strong> characteristics of,<br />
89-96<br />
released post-1972, in U.S., 92-94<br />
ilf i
Index 635<br />
released pre-1972j in U.S., 89-91<br />
sheath blight resistance of, 194<br />
Meiosis, 123<br />
MERCOSUR, 485,487<br />
Mercury cultivar, 95<br />
Mesocotylar roots, 109,110,117<br />
Mctalaxyl, 417<br />
Metal microimfrients, 376-383<br />
Metirane, 326<br />
Methoxyféiiozide, 448<br />
Methyl bromide, 559<br />
Methyl paratliion, 444, 446, 449,<br />
450<br />
Metokchlor, 464<br />
Mexican rice borer (MRB), 447-448<br />
Mexico, 485,487<br />
M-401 cultivar, 95<br />
Microsatellite molecular markers,<br />
189-190,192<br />
Microsporogencsis, 123<br />
Middle Bast, 485<br />
Milk stage, 124<br />
Mills;<br />
in mid-1800’s, 73<br />
private <strong>and</strong> cooperative, 478<br />
tidal-powered, 71-72,75<br />
Milled rice:<br />
global yield for, 264,266-269<br />
mass, 569<br />
storage otj 546<br />
yield for, 569<br />
Milling;<br />
by-products of, 484<br />
degree of, 569<br />
global rate of, 264,266-269<br />
in ISOO’s, 76,77<br />
Milling quality:<br />
breeding for, 190<br />
definitions/terms related to,<br />
568-570<br />
<strong>and</strong> issues at harvest, 570-577<br />
<strong>and</strong> property characterization,<br />
570-574<br />
<strong>and</strong> rate of drying, 580-585<br />
<strong>and</strong> respiration effects, 575-577<br />
Milling yield, 190<br />
Mineralization-immobilization;<br />
of nitrogen, 339<br />
of sulfvii', 374<br />
Mineral nutrition, 146<br />
Ministry of Agriculture, Forestry,<br />
<strong>and</strong> Fisheries (Japan),<br />
609-610<br />
‘'Miracle" rice, 83<br />
Mississippi, vii<br />
early rice <strong>production</strong> in, 82<br />
grain types grown in, 289<br />
rice <strong>production</strong> in, viii<br />
soils in, 299<br />
Missouri, vii<br />
grain types grown in, 289<br />
rice <strong>production</strong> in, viii<br />
MLRAs, see Major l<strong>and</strong> resource<br />
areas<br />
Model system, rice as, 196,205<br />
Modified Henderson equation, 578<br />
MOG, see Material-other-thangrain<br />
Moisture content (MC):<br />
<strong>and</strong> fungal growth, 562<br />
for germination, 114<br />
at harvest, 494-496<br />
of harvested rice, 291<br />
of individual Icernels, 570-575<br />
<strong>and</strong> milling quality, 580-581<br />
reduction in, during drying,<br />
583-588<br />
<strong>and</strong> respiration, 553, 554,<br />
575-576<br />
<strong>and</strong> spoilage, 293<br />
Moisture ratio, 578, 580<br />
Mold growtli (during storage),<br />
562-563<br />
Molecular characterization, Oryza,<br />
6-7<br />
Molecular genetic linkage maps,<br />
205-206<br />
Molecular markers:<br />
AFLPs, 162,206<br />
microsatellite, 189-190, 192<br />
RAPD, 6, 52,162,205<br />
RPLPs, 43, 62,161, 192,205, 207<br />
selection assisted by, 207-208<br />
SSR, 206<br />
STS, 162<br />
Moliiiate, 463,465,469-470<br />
Mollisols, 298<br />
Momilactones, 230-231,236,238<br />
Monitoring (of plant development),<br />
104<br />
Monodioria assay, 233, 234<br />
Monsanto, 207<br />
Morning glories, 459<br />
Morphological characteristics<br />
(soils), 298-304<br />
Morphology, rice, 104-113<br />
culm, 107-108<br />
flower, 111<br />
grain, 111-113<br />
leaves, 105-107<br />
panicle, 110-111<br />
roots, 108-110<br />
shoot unit concept, 104-105<br />
Morris, John, 79<br />
Mottles, 304<br />
MRB, see Mexican rice borer<br />
M-202 cultivar, 95, 98<br />
Mudding in, 286<br />
Mullins, D, Ti’oy, 82<br />
Mutations;<br />
induced, 164-166, 208<br />
somatic, 209<br />
Mycoplasma-like diseases, 430-431<br />
NAFTA, see North American Free<br />
Trade Agreement<br />
Names of species, variation in, 48<br />
Narrow brown leaf spot, 185-186,<br />
425-426<br />
National Bureau of Plant Genetic<br />
Resources (NBPGR), 609<br />
National Center for Genetic<br />
Resources Conservation<br />
(NCGRC), 606<br />
National Institute for Agricultural<br />
Sciences (INSA), 612<br />
National <strong>Rice</strong> Seed Storage<br />
Laboratory for Genetic<br />
Resources (Thail<strong>and</strong>), 611<br />
National Small Grains Collection,<br />
599-604<br />
Nato cultivar, 95,98<br />
Natric soil horizon (n), 303<br />
NBPGR, see National Bureau of<br />
Plant Genetic Resources<br />
NCGRC (National Center<br />
for Genetic Resources<br />
Conservation), 606<br />
Nematode diseases, 419,431<br />
Net blotch, 425<br />
New cultivar development, see<br />
Breeding<br />
New Deal, 81<br />
New Guinea, 52-53<br />
New Holl<strong>and</strong> combines, 513,537<br />
Newman, Ralph S., 82<br />
New Orleans, Louisiana, 73,76-77<br />
Newrex cultivar, 94,97<br />
Nicaragua, 485<br />
Nipponbare cultivar, 161<br />
Nitrate, 326<br />
Nitrification, 339<br />
Nitrification inhibitors, 342-343<br />
Nitrogen;<br />
decomposition of crop residues<br />
<strong>and</strong>, 283<br />
forms/behavior of, 333-340<br />
in leaves, 146<br />
<strong>and</strong> oxidized soil layer, 325<br />
Nitrogen fertilizers, 146, 333-359<br />
in alternative irrigated systems,<br />
355-356<br />
application rate for. 356-359<br />
application timing for, 343-349<br />
early/preflood application of,<br />
349-353<br />
management options with,<br />
348-356<br />
midseason application of,<br />
353-355<br />
preplant application of, 351-352<br />
ill ratoon <strong>production</strong>, 290<br />
<strong>and</strong> soil nutrition, 340-359<br />
souices/placemcnt of, 341-343<br />
N (natric soil liorizoii), 303<br />
Nodal roots, 109<br />
Nodes, 104-105,108.109,117,118
63Ó<br />
Index<br />
r I<br />
ií i i<br />
Nolinatc, 462<br />
Nomenclature, confusion in, 46-48<br />
Notimachine loss, 529<br />
Nonrecourse loan program, 479<br />
Nortai ciillivar, 95<br />
North America, 4. See also specific<br />
coun tries<br />
North American Free Trade<br />
Agreement (NAFTA),<br />
485-487<br />
North American L<strong>and</strong> <strong>and</strong> Timber<br />
Company, 73<br />
No-tillage systems,-286-287<br />
Nova 76 cultivar, 95<br />
Nowick, E,, 600<br />
NPGS, see US, National Plant<br />
Germplasm System<br />
Nutrition, 332-385<br />
diseases related to, 146-149<br />
<strong>and</strong> grain quality, 210<br />
iron in, 382-383<br />
manganese in, 382-383 ;<br />
metal microiiutrients, 376-383<br />
nitrogen in, 340-359<br />
phosphorus in, 361-368<br />
physiology of, 146-149<br />
potassium in, 369-373<br />
silicon in, 383-385<br />
sulfur in, 375-376<br />
zinc in, 377-382<br />
Nutsedge, 459,463<br />
Nymphal cast skins, 449<br />
Office de la Recherche Scientifique<br />
et Technique Outre-Mer<br />
(ORSTOM), 607, 609<br />
Oka, H. 1., 10,609<br />
On-farm diying <strong>and</strong> storage, 477,<br />
478,590-591<br />
Optimum preflood (OFF) fertiliKer<br />
application, 345-348<br />
Options, 480-481<br />
Organic carbon, 315,322-325<br />
■Organic phosphorus, 350<br />
Organic rice farming, 561<br />
Organ ophosphate, 445,461<br />
ORSTOM, see Office de la<br />
Reclierdie Scientifique et<br />
Technique Outre-Mer<br />
Oryza, 4-11, See also specific topics<br />
biosystematics research<br />
directions, 57<br />
continental drift <strong>and</strong> dispersion<br />
of, 8<br />
evolution of, 28<br />
genomes, 4-6<br />
<strong>history</strong> of, 28<br />
karyotype of, 6<br />
key characteristics of species in,<br />
30<br />
molecular characterization of,<br />
6-7<br />
0. braclxyantha Chev. ct Roehr,<br />
30-33<br />
O. g la b b en iin a, 11-12<br />
O. gran ulata complex, 31, 33-34<br />
O, officinalis complex, 31, 35-46<br />
0. rid h y i complex, 31, 35,36<br />
O. sativa, 9-11<br />
0, sativa complex, 31,44-55<br />
O. scííjeehferí Pilger, 30,31<br />
species complexes of, 88<br />
species of, 4-8, 31<br />
taxonomic position of, in the<br />
Poaceae, 29-30<br />
updated biogeography map for,<br />
7-8<br />
■weedy rice, 55-57<br />
O ryza a b r o m e itia m , 34<br />
O ryza alta Swallen, 43,44, 46<br />
O ryza australiensis, 6<br />
O ryza australiensis Domiii, 31,<br />
42-43<br />
Oryza barthii, 6,55<br />
O ryza barthii A, Chev., 11, 51,52<br />
O ryza brachyantka, 30<br />
Oryza brachyantha Chev. et Roejir,<br />
30-33<br />
O ryza eichingeri Peter, 31,37-38<br />
Oryza glaberrim a, 6,11-12<br />
O ryzaglu m aepatu la, IS<br />
O ryza glu m aep atu la Steud., 53-55<br />
O ryza gr<strong>and</strong>iglum is (DoelL) Prod.,<br />
43,45<br />
O ryzagram ilata complex, 31,33-34<br />
O ryza gran ulata complex, 31,33-34<br />
Oryza gran ulata Nees et Arn. ex.<br />
Watt, 33,34<br />
O ryza in d an d am an ica Ellis, 34<br />
Oryza latifolia, 55<br />
Oryza latifolia Desv., 43,44<br />
Oiyzalcxins, 230,238<br />
Oryza longiglw nis Jansen, 35, 36<br />
O ryza longistam inata, 45, 55<br />
O ryza longistam inata A. Ciiev., 11<br />
Oryza longistam in ata Chev, et<br />
Roehr, 50-51<br />
O ryza meridiortalis, 18<br />
O ryza m eridionalis Ng, 52,53<br />
Oryza m eyerian a subsp. tubercuiata,<br />
34<br />
Oryza m eyerian a (Zoll, et mor. ex.<br />
Steud.) Baill., 33<br />
O ryza m inuta J, S, Presl. ex C. B.<br />
Presl., 31, 39^0<br />
O ryza m a ca led on ica Moral, 34<br />
O ryza nivara, 6, 9<br />
O ryza officinalis, 6,55<br />
O ryza officinalis complex, 31,35-46<br />
CCDD genome species in Latin<br />
America, 31, 43-46<br />
O. australiensis Domin, 31,42-43<br />
O. eichingeri Peter, 31, 37-38<br />
O. m in u ta J, S. Presl. ex C, B,<br />
Pres)., 31, 39-40<br />
O. officinalis Wall cx. Watt, 31,<br />
35-37<br />
O. pHnefata Kofschy ex Steud.,<br />
31, 40-42<br />
0, rhizom atis D. A. Vaughan, 31,<br />
38-39<br />
O ryza officinalis Wall ex. Watt, 31,<br />
35-37<br />
O ryza perren nis Moench, 9<br />
Oryza pu nctata, 55,164<br />
O ryza p u n cta ta Kotschy ex Steud,,<br />
31,40-42<br />
O ryza puntato, 6<br />
O ryza rhizom atis D. A. Vaughan,<br />
31,38-39<br />
Oryza r id h y i complex, 31,35,36<br />
O ryza rid h y i Hook, 35,36<br />
O ryza rufipogon, 9,47,48<br />
genome symbol for, 6<br />
sativa rices derived from, 88<br />
Oryza rufipogon Griff., 9<br />
Oryza rufipogon sensu lacto, 52,53<br />
subsp. nivara, 49,50<br />
subsp. rufipogon, 49-50<br />
as weed, 55<br />
O ryza sativa, vii, 9-11, 47, 48, See<br />
also specific topics<br />
evolutionary pathway of, 9-11<br />
genetic base of, 19<br />
genome symbol for, 6<br />
O ryza sativa complex, 31,44-55,88<br />
in Africa, 50-52<br />
in Asia, 35-40<br />
ill Australia <strong>and</strong> New Guinea,<br />
52-53<br />
in Latin America, 53-55<br />
O ryza sativa L, 104-113<br />
O ryza sativa sensu lacto, 49<br />
O ryza schlechten , 30<br />
O ryza sch lediteri Pilger, 30,31<br />
Oryzeae tribe, 29<br />
Osmotic pressure (of soil solution),<br />
393<br />
Overflows, 276<br />
Oxidation-reduction reactions, 148<br />
Oxidation-reduction status (soils),<br />
315-317, 322-325<br />
Oxygen, 138,148,309-310<br />
Paddy Breeding Station (India), 608<br />
Paddy (paddy rice), vii, viii,<br />
147-149. S ee also Rough<br />
rice<br />
Pakistan, 485,487<br />
Palea, 111<br />
Panicles, 106,110-111<br />
formation of, 123<br />
as nitrogen sinks, 146<br />
during reproductive phase,<br />
122-124<br />
during vegetative phase, 113,114<br />
Panicle blight, 186,429-430
Index 637<br />
Panicle differentiation stage,<br />
122-123<br />
Paraquat, 464<br />
Parrot beak, 430,432<br />
Particle bombardment (of callus<br />
tissue), 209<br />
Passes (of drier), 590<br />
Pasting properties (rice flours), 564<br />
Peck, 428, 443<br />
‘Peckyrice, 428<br />
Pecos cultivar, 95<br />
Pedicles, 110, 111<br />
Pendimethalin, 461-464,470<br />
Perendiyma, 112<br />
Perennial rices, 49<br />
Pericarp, 111, 112<br />
Perled rice, viii<br />
Pests, see Arthropod pests; Insects<br />
Pest management, 450-451<br />
Petri dish assay method, 232-233<br />
Petrocalcic horizon (km), 303<br />
PGQO, see Plant Germplasm<br />
Quarantine Office<br />
PH, soil, 272,317,325-326<br />
Phenolic adds, 225,226, 236-238<br />
Phenoxy, 419<br />
Philippines, 487,493,610-611<br />
Phosphine, 559<br />
Phosphorus, 359-368<br />
diagnosis of deficiency in,<br />
365-368<br />
fertilizing with, 361-363<br />
forms/behavior of, 359-361<br />
in soil nutrition, 362<br />
soil test methods for, 361-365<br />
Phostoxin, 559<br />
Photosensitivity, 96<br />
Pliotosyntliesis, 133, 137-138<br />
Phyllochron, 118<br />
Physical chromosome mapping,<br />
206<br />
Physical properties of soils,<br />
304-315, 319-322<br />
aeration, 309-312<br />
color, 304-305<br />
hydraulic conductivity, 307-309<br />
hydraulic properties, 319<br />
structure. 305<br />
temperature/thermal<br />
characteristics, 312-315,<br />
320-322<br />
texture, 305<br />
water <strong>and</strong> balance/use, 305-307<br />
water infiltration <strong>and</strong><br />
redistribution of, 319-<br />
321<br />
Physiology of rice, 129-149. See also<br />
Development of rice<br />
aerenchyma, 138<br />
<strong>and</strong> coordinated function in<br />
development, 130<br />
disorders related to, 431—432<br />
gennination <strong>and</strong> seedling<br />
development, 131-137<br />
grain development, 139<br />
hormones, 143,145-146<br />
mineral nutrition, 146<br />
nutritional conditions <strong>and</strong><br />
stresses, 146-149<br />
path of carbon in endosperm,<br />
139,142-145<br />
photosynthesis, 133, 137-138<br />
plant development, 130-131<br />
reproductive development,<br />
139-141<br />
Phytoalexins, 230<br />
Phytomer, 105<br />
Phytotoxins, 224, 236-238<br />
Pickup reek (combines), 293,505<br />
Pinpoint flooding, 281, 282, 284,<br />
438, 465<br />
Piracy, rice trade <strong>and</strong>, 70<br />
Pirimiphos-methyl, 560<br />
Pistil, 111<br />
Plant box method, 231<br />
Plant Genetic Resources Program<br />
(Pakistan), 610<br />
Plant Germplasm Quarantine<br />
Office (PGQO), 606,607<br />
Planting of rice;<br />
dates for, 287-288<br />
evolving methods of, 14,16<br />
methods for, 281-284<br />
seeding rates, 288<br />
water-seeding systems, 281-282<br />
Plant quarantine, 432-433<br />
Plastochron, 118<br />
Plate tectonics, 8<br />
Platform augers (combines), 506.<br />
See a h o Gathering head<br />
(combines)<br />
PL480 programs, 475,486<br />
Plumule, 112<br />
Poacae family. O tyza in, 29-30<br />
Poising (soils), 322<br />
Poisoning (of rodents), 563<br />
Polished rice, viii<br />
Pollen formation, 123<br />
Pollen shed, 124<br />
Pollination, 124<br />
Polyolefin-coated urea, 342<br />
Polypeptide hormones, 143<br />
Porteresia, 29,30<br />
Postharvest loss, 529<br />
Potassium, 368-373<br />
diagnosis of deficiency In,<br />
371-373<br />
fertilizing witli, 370-371<br />
forms/beiiavior of, 368-369<br />
in soil nutrition, 369-370<br />
Potassium chloride (KCl), 370<br />
Poultry litter, 399-400<br />
Power thresliers, 520-528<br />
Prairie rice farmers, 73,78-79<br />
Precision graded soils:<br />
l<strong>and</strong> leveling for, 272-274,306<br />
reclamation <strong>and</strong> fertilization of,<br />
398-400<br />
Preflood fertilization, 341<br />
Preharvest loss, 529<br />
Presprouted rice, 416-417<br />
Prices, rice, 481, 487<br />
Pricing methods, 478-479<br />
Prilled urea, 341,342<br />
Primary branches, 110, 111<br />
Primary roots, 120<br />
Primary tillers, 109<br />
Private equipment ownership,<br />
537-541<br />
Private rice mills, 478<br />
Processed foods, rice in, 481,482<br />
Processed rice, marketing of,<br />
481-486<br />
Production of rice, vii—-viii. See<br />
also specific topics<br />
acreage involved in, 4<br />
by country, 257-264<br />
crop rotations/doublc-a'opping,<br />
289,290<br />
cultivar selection, 289<br />
<strong>and</strong> diseases, 414-415<br />
drying rice, 293-294<br />
global, 247-269<br />
harvesting, 291-294<br />
<strong>history</strong> of, 67-84<br />
l<strong>and</strong> sclection/formation for,<br />
272-276<br />
milled yield/milling rate, 264,<br />
266-269<br />
planting dates, 287-288<br />
planting methods. 281-284<br />
ratoon <strong>production</strong>, 290-291<br />
rice area harvested, 258, 261-266<br />
seeding rates, 288<br />
seed <strong>production</strong>, 167-168<br />
storage <strong>and</strong>, 546<br />
tillage practices. 236-287<br />
in the United States, see U.S. rice<br />
<strong>production</strong><br />
water management, 284-286<br />
water requirements for, 276-281<br />
by world regions, 249-257<br />
world-wide, 487<br />
Productivity:<br />
<strong>and</strong> iiutritioiial disorders, 146<br />
<strong>and</strong> precision grading of soils,<br />
398<br />
Programmed ceil death, 138<br />
Propanil, 285,445, 450-451, 462,<br />
463, 470<br />
Prophyllleaf, 109,117,118<br />
Protectants:<br />
for disease control, 418<br />
for insect control, 560<br />
Proteins, 129,130<br />
Providence crop, 180<br />
P (tillage pan), 303<br />
Puerto Rico, 289
638 Index<br />
Pump discharge capacity, 279<br />
Purple ammannia, 459<br />
Put options, 480,481<br />
Pyrethrins, 560<br />
Qm (duripan), 303<br />
Quality:<br />
breeding for, 188-192<br />
control of, 479<br />
<strong>and</strong> harvesting, 531-533,<br />
570-577<br />
<strong>and</strong> nutrition, 210<br />
as primary breeding objective,<br />
179<br />
rice diseases <strong>and</strong>, 414-415<br />
st<strong>and</strong>ards for, 532<br />
during storage <strong>and</strong> aging,<br />
563-564<br />
<strong>and</strong> storage conditions, 552-555<br />
of US, rice, 97-98<br />
Quaternary tillers, 109<br />
Quick-killing rice combine<br />
harvesters, 517-518<br />
Qiiinclorac, 461,463, 467, 470-471<br />
Quizolofop, 465<br />
Rachilla, 112,113<br />
Racliis, 110, 111<br />
Radiative stress, 148<br />
Radical oxygen, 148<br />
Radical oxygen-related stress, 148<br />
Radicle, see Seminal root<br />
Railroads, 73, 76-78<br />
Rainfed wetl<strong>and</strong> agro ecosystems, 15<br />
R<strong>and</strong>omly amplified polymorphic<br />
DNA (RAPD), 6, 52,162,<br />
205<br />
Ratoon crops, 290-291<br />
<strong>and</strong> breeding for maturity, 180<br />
milling quality of, 190<br />
<strong>and</strong> stripper-header use, 293<br />
water management for, 285<br />
yield of, 180<br />
Katooniiig (vegetative<br />
propagation), 167<br />
RCGC, see <strong>Rice</strong> Crop Gennplasm<br />
Committee<br />
Record keeping, harvesting, 535<br />
Red flour beetle, 558<br />
Redox potential (soils), 316-317,<br />
360<br />
Red rice, 88, 459-460<br />
<strong>and</strong> delayed-flooding, 282<br />
imazathapyr for controJ of, 447<br />
mudding in for control of, 286<br />
<strong>and</strong> ratoon cropping, 290<br />
<strong>and</strong> rice rotation systems, 289<br />
seed dormancy in, 133<br />
weed control for, 464-466<br />
Redstem, 459<br />
Reduced condition (soil), 315<br />
Reduced tillage, 286-287<br />
Regeneration (of germplasm), 58<br />
Regional research laboratories, 82<br />
Regional rice <strong>production</strong> (world),<br />
249-257<br />
Rcimei mutants, 164<br />
Relay seeding, 231, 232<br />
Reproductive stages, 113,120-124<br />
culm during, 108<br />
physiology of, 139-141<br />
Research <strong>and</strong> Marketing Act of<br />
1946, 599<br />
Research laboratories. See also<br />
Breeding<br />
international, 83<br />
private, 192<br />
regional U.S., 82<br />
Respiration, 552, 553,559, S 75-5 7 7<br />
Restriction fragment length<br />
polymorphism (RFLP), 43,<br />
52,161,192,205,207<br />
Rexarkcultivar, 95<br />
Rexmont cultivar, 94<br />
Rexoro cultivar, 91,94,97<br />
RPLP, see Restriction fragment<br />
length polymorphism<br />
RGC (<strong>Rice</strong> Genetics Cooperative),<br />
161<br />
RGN (R ice G enetics N ew sletter), 161<br />
RGP map, see <strong>Rice</strong> Genome<br />
Research Program map<br />
RGP (<strong>Rice</strong> Genome Research<br />
Program), 207<br />
<strong>Rice</strong> allelopathy:<br />
research, 222-236<br />
for weed control, 221<br />
<strong>Rice</strong> blast disease, 182-184, 356<br />
<strong>Rice</strong> bran, 113<br />
<strong>Rice</strong> combine harvesters, 292-293,<br />
496-522<br />
in Asia, 518-524<br />
categories of, 500-501<br />
cleaning system in, 513-514<br />
conveying functions of, 517<br />
crop feeding <strong>and</strong> tlrreshing in,<br />
509-512<br />
custom-made, 499-500<br />
cutterbars in, 505-506<br />
functions of, 501-504<br />
lifters for, 509<br />
<strong>and</strong> need for rice-special<br />
combines, 496-499<br />
operation of, 504-518<br />
pickup reels in, 505<br />
platform augers in, 506<br />
quick-killing, 51 7-t5 18<br />
rice combines, 500-501<br />
rice-special, 496-499<br />
separation process in, 512-513<br />
stripperheads in, 507-509<br />
<strong>and</strong> trash, 514-516<br />
unplugging, 518<br />
Vibramat attachments for, 509<br />
windrow pickups for, 509<br />
<strong>Rice</strong> conditioners, 561<br />
<strong>Rice</strong> Council for Market<br />
Development, SI, 82<br />
<strong>Rice</strong> Crop Germplasm Committee<br />
(RCGC), 604-605<br />
<strong>Rice</strong> entomologists, 328,450-451<br />
<strong>Rice</strong> flours, 564<br />
<strong>Rice</strong> gauge, 355-356<br />
<strong>Rice</strong> G ene S ym bolization an d<br />
Linkage Groups, 153,161<br />
<strong>Rice</strong> Genetics <strong>and</strong> Cytogenetics<br />
Symposium (1963), 6<br />
<strong>Rice</strong> Genetics Cooperative (RGC),<br />
161<br />
R ice G em tk s N ew sletter (RGN), 161<br />
<strong>Rice</strong> Genome Project, 7<br />
<strong>Rice</strong> Genome Research Program<br />
(RGP), 207<br />
<strong>Rice</strong> Genome Research Program<br />
(RGP) map, 161-162<br />
<strong>Rice</strong>l<strong>and</strong> Foods <strong>and</strong> Producers<br />
Cooperative, 478<br />
<strong>Rice</strong> leaf miner (RLM), 447<br />
<strong>Rice</strong> Millers’ Association, 81,478<br />
<strong>Rice</strong> Production Act of 1975,475<br />
<strong>Rice</strong> Quality Evaluation program<br />
(USDA—ARS), 188<br />
<strong>Rice</strong> Research Unit (USDA—^ARS),<br />
192<br />
<strong>Rice</strong> seed midges, 446-447<br />
<strong>Rice</strong>-special combines, 496-499<br />
<strong>Rice</strong> stalk borer, 447-448<br />
<strong>Rice</strong> stem borers, 447—448<br />
<strong>Rice</strong> stink bug (RSB), 438,443-444<br />
<strong>Rice</strong>Tec, Inc., 167<br />
<strong>Rice</strong> Technical Working Group<br />
(RTWG), 340,605<br />
<strong>Rice</strong> water weevil (RWW), 438,<br />
440-443<br />
breeding for resistance to, 187<br />
drainage for control of, 285<br />
<strong>Rice</strong> weeds, 459-460<br />
<strong>Rice</strong> weevils, 556-558<br />
Rico 1 cultivar, 95<br />
Ring-A-Rouiid, 167<br />
Ripening (grain-filling) phase, 113,<br />
124-125<br />
Risk Management Agency (RMA),<br />
477<br />
RLM (rice leaf miner), 447<br />
RMA (Risk Management Agency),<br />
477<br />
Rockefeller Foundation, 83,204<br />
Rodent problems (during storage),<br />
563<br />
Rogers, Woodes, 70<br />
Roller mills, 73<br />
Roosevelt, Franklin D., 81<br />
Roots:<br />
branching of, 120<br />
<strong>and</strong> continuous flooding, 282<br />
diseases of, 418-419<br />
Root development, 104, 105,<br />
108-110
Index 639<br />
during reproductive phase, 122<br />
of seedlings, 117,118<br />
during tillering, 119-120<br />
during vegetative phase, 113,114<br />
Root knot, 419<br />
Root rot, 418-419<br />
Rotary combines, 500,501, 513<br />
"Rotten neck" syndrome, 424<br />
Rough rice, 567-592<br />
■ drying systems for, 588-591<br />
global <strong>production</strong> of, 4<br />
grades of, 479<br />
marketing system for, 477-481<br />
milling quality delinitions/terms,<br />
568-570<br />
storage of, 546<br />
Roundleaf mudplantaiii, 459<br />
RSB, see <strong>Rice</strong> stink bug<br />
RTWG, see <strong>Rice</strong> Technical Working<br />
Group<br />
Rust-red flour beetle, 558<br />
RWW, see <strong>Rice</strong> water vícevil<br />
Salicylic acid, 143<br />
Saline soils, 385-395<br />
behavior of soluble salts, 388-392<br />
determina tioii of soil salinity,<br />
386-388<br />
effects of salts on plant growth,<br />
392-394<br />
management of, 394-395<br />
Salinity:<br />
definition of, 385<br />
injury from, 393-394<br />
Salt(s). See also Saline soils<br />
accumulation of, 277<br />
in irrigation water, 277<br />
Salt-affected soils, 385<br />
Salt damage, 431<br />
Salvage weed control, 463-464<br />
Sampath, S., 609<br />
Satake image analyzer, 571<br />
S ativa Ros che V., 7<br />
Saturated paste extract metliod<br />
(EC), 318<br />
Saturn cultivar, 98<br />
Saudi Arabia, 487<br />
SEE, see Starcli branching enzyme<br />
Scab, 372<br />
Screenings, 569<br />
Scuteliuin (cotyledon), 112<br />
SDC (Swiss Agency for<br />
Development <strong>and</strong><br />
Cooperation), 610<br />
Seasonal behavior of soils, 319-326<br />
Seasonal water balance equation,<br />
305<br />
Secondary metabolites, 222,<br />
224-231<br />
Secondary roots, 120<br />
Secondary tillers, 109<br />
Secondary trisomies, 161<br />
Second cropping, see Ratoon crops<br />
Second heads, 569<br />
Seeds;<br />
diseases of, 415-418<br />
germination of, 113-117<br />
<strong>production</strong> of, 167-168<br />
Seedbed preparation, 286<br />
Seed coat (tegmen) ,111-114<br />
Seeding rates, 288<br />
Seedlings:<br />
breeding for vigor of, 187-188<br />
diseases of, 415-418<br />
Seedling blight, 417-418<br />
Seedling development, 111,<br />
117-118<br />
physiology of, 131,133-137<br />
<strong>and</strong> salinity, 392-394<br />
Seed midges, rice, 446-447<br />
Self-pollination, 124<br />
Semidwarf cultivars, 179<br />
Semidwarfing mutants, 164-165<br />
Semidwarfism, 96<br />
Seminal root, 109,110,112, 117<br />
Senescence, 125<br />
Sen rice, 18<br />
Separation process (combines),<br />
512-513<br />
Sequence-tagged site (STS)<br />
markers, 162<br />
Sethoxydim, 465<br />
Shape,panicle, 111<br />
Sharkey soils, 299,302, 305,319,<br />
467<br />
Sliastry, S. V. S., 609<br />
Shattering, 570<br />
Shatter resistance, 180<br />
Sheath, leaf, see Leaf sheath<br />
Sheath blight, 184-185,420-421<br />
Sheath rot, 422-423<br />
Sheath spot, 423<br />
Shelbourne Reynolds stripperheader,<br />
292, 293, 501,<br />
503<br />
Shoot unit concept, 104-105<br />
Short-grain cultivars, 289<br />
grain quality of, 98<br />
<strong>history</strong> <strong>and</strong> characteristics of,<br />
89-96<br />
released post-1972, in U.S., 92-94<br />
released pre-1972, in U.S., 89-91<br />
Signaling networks, 145<br />
Silica, 130<br />
Silicon, 383-385<br />
fertilizing with, 384<br />
in soil nutrition, 383-385<br />
Simple sequences repeat (SSR)<br />
markers, 206<br />
Sínica race, see Japónica subspecies<br />
(race)<br />
Slave labor, 69<br />
Slickensides (ss), 304<br />
Smitli, D. H, Jr., 601<br />
Sodic soils, 397-398<br />
Soft dough stage, 124<br />
Soil(s), 326. See also Soil solution<br />
aeration of, 120,309-312<br />
alkaline, 385-386,395-398<br />
anoxic, 316<br />
calcareous, 396-397<br />
Calloway, 319-322<br />
characteristics <strong>and</strong> behavior of,<br />
298-327<br />
chemical properties of, 315-319,<br />
322-326<br />
color of, 304-305<br />
Crowley, 300,302,319<br />
desirable types of, 272-276<br />
DeWitt, 319<br />
drainage <strong>and</strong> type of, 285<br />
electrical conductivity of,<br />
317-318,326<br />
fertilization of, 332-385<br />
gases in, see Aeration<br />
hydraulic conductivity <strong>and</strong><br />
drainage of 307-309<br />
hydraulic properties of 319<br />
iron in, 382-383<br />
manganese in, 382-383<br />
metal micro nutrients in, 376-383<br />
morphological diaracteristics of,<br />
298-304<br />
nitrogen forms <strong>and</strong> behavior in,<br />
33,3-340<br />
nitrogen iiuti'ition <strong>and</strong><br />
fertilization practices,<br />
340-359<br />
nutrition of, see Nutrition<br />
oxidation-reduction status of,<br />
315-317, 322-325<br />
pH of, 272,317, 325-326<br />
phosphorus deficiency in,<br />
365-368<br />
phosphorus forms <strong>and</strong> behavior<br />
in, 359-361<br />
phosphorus nutrition <strong>and</strong><br />
fertilization practices,<br />
361-368<br />
physical properties of, 304-315,<br />
319-322<br />
potassium in, 368-373<br />
precision graded, 398-400<br />
saline, 385-395<br />
salt accumulation in, 277<br />
seasonal behavior of 319-326<br />
Sharkey, 299,302,319<br />
silicon in, 383-385<br />
sodic, 397-398<br />
structure of 305<br />
submergence <strong>and</strong> properties of<br />
315<br />
suboxic, 316<br />
sulfur ill, 373-375<br />
temperature/thermal<br />
diaracteristics of, 312-<br />
315,320-322<br />
texture of, 305<br />
<strong>and</strong> water balaiice/use, 305-307
640 Indox<br />
Soils (con tin u ed)<br />
water infiltration <strong>and</strong><br />
redistribution of, 319-<br />
321<br />
Willows series, 301, 302<br />
zinc in, 376-382<br />
Soil management;<br />
alkaline soils, 385, 39S-39S<br />
saline soils, 385-395<br />
Soil solution, 318-319, 326<br />
Solar radiation, stored rice <strong>and</strong>, 555<br />
Somaclonal variation, 209<br />
Somatic mutations, 209<br />
Sooty mold fungus, 449<br />
Sorenson, ]. W., ]r,, 82<br />
South Africa, 485<br />
South America, 4, 486. S ee also<br />
specific countries<br />
South Carolina, vii—^viii. S ee also<br />
American rice industry<br />
Southern, Pacific, <strong>and</strong> Delta <strong>Rice</strong><br />
Growers, 81<br />
Southern Pacific Railroad, 73,<br />
75-77<br />
Southern Real Estate, Loan <strong>and</strong><br />
Guaranty Company, 76<br />
Southern Regional Research<br />
Laboratory, 82<br />
South Korea, 485,487,518<br />
Soybeans, rotation with, 289,290,<br />
464, 465<br />
SPAD meter, 355-356<br />
Specialty rices, 191-192<br />
Speck back, 444<br />
Spiders, 449<br />
Spikelets, 110, 111, 123-124<br />
Spillways, 276<br />
Split method fertilizer application,<br />
345-346<br />
Spoon-feeding fertilizer<br />
application, 348<br />
Sprangletop, weed control fer, 463<br />
Sprinkler irrigation, 285,355<br />
SSR (simple setjueiiees repeal)<br />
markers, 206<br />
Ss (slickensides), 304<br />
Stackburn, 426, 575<br />
Stale-seedbed systems, 287<br />
Stalk borer, rice, 447-448<br />
Siam 3-13,461<br />
Stamens, 111<br />
St<strong>and</strong>ards, quality, 532<br />
Starch;<br />
storage of, 112,138<br />
synthesis of, 142-144<br />
Starch branching enzyme (SEE),<br />
143,144<br />
Starch paste viscosity profile, 189<br />
Starch storage tissue, 112<br />
State agriculture experiment station<br />
programs, vii<br />
Steam engines, 73<br />
Stelly, R<strong>and</strong>all, 82<br />
Stem, see Culm<br />
Stem borers, rice, 447—448<br />
Stem nematode disease, 431<br />
Stem rot, 421-422<br />
breeding for resistance to, 185<br />
<strong>and</strong> potassium deficiency, 372<br />
Stiff-strawed cultivais, 343<br />
Stink bug, rice, 443-444<br />
Storage of rice, 546-565<br />
commercial warehouses for,<br />
477-478<br />
effects of rice <strong>production</strong> on, 546<br />
facilities for, 547-550<br />
in farm-scale bins, 547-548<br />
in grain elevators, 548-550<br />
insect damage during, 555-558<br />
<strong>and</strong> moisture content, 293<br />
<strong>and</strong> mold/fungal problems,<br />
562- 563<br />
on-farm, 477,478,590-591<br />
practices, storage, 548-554<br />
protection from insects during,<br />
559-562<br />
<strong>and</strong> rice quality, 552-555,<br />
563- 564<br />
<strong>and</strong> rodent problems, 563<br />
<strong>and</strong> stackburn, 426<br />
Storm, 466,467<br />
Straighthead, 147,432<br />
breeding for resistance to, 186,<br />
187<br />
<strong>and</strong> drainage, 284-285<br />
Straw spreaders (combines), 292<br />
Streaking, 350-351<br />
Stress(es), 146-149<br />
breeding for tolerance to,<br />
187-188<br />
genetic engineering for tolerance<br />
to, 212<br />
Strike price, 480-481<br />
Stripperheads, 292-293, 502,<br />
507-509<br />
STS (sequence-tagged site) markers,<br />
162<br />
Stubble management, 291<br />
Stuttgart soil, 308<br />
Subaleurone layer, 112<br />
Suboxk soils, 316<br />
Subsidized crop insurance, 477<br />
Sucrose, 139, 142<br />
Sucrose synthase, 142<br />
Sugarcane borer, 447-448<br />
Sulfide, 326<br />
Sulfur, 373-376<br />
diagnosis of deficiency in,<br />
375-376<br />
fertilizing with, 375-376<br />
forms/behavior of, 373-375<br />
in soil nutrition, 375-376<br />
Sulfur-coated urea, 342<br />
Superoxide radicals, 148<br />
Surveying, 274<br />
Swiss Agency for Development <strong>and</strong><br />
Cooperation (SDC), 610<br />
Syngenta, 207<br />
Systemic fungicides, 418<br />
T. W, Wood <strong>and</strong> Sons, 600<br />
Ihdpole shrimp, 449-450<br />
Taichung Native 1 cultivar, 96<br />
Tailings, 512<br />
Taiwan, 487, 518<br />
llmgential feed harvesters, 510<br />
Tangential flow harvesters, 497, 498<br />
T (argillic soil horizon), 302-303<br />
Taxonomy;<br />
of Asian rice (O. sativa L.J, 48<br />
position of O ryza in, 29-30<br />
of weedy rice, 55<br />
Tebufciiozidc, 448<br />
Tegmen, see seed coat<br />
Temperature:<br />
breeding for extremes ofi 188<br />
for germination, 116-117<br />
<strong>and</strong> hot spots in stored rice, 558<br />
<strong>and</strong> metal micronutrients, 376<br />
for planting, 287-288<br />
<strong>and</strong> respiration, 576<br />
of rice water, 278<br />
<strong>and</strong> seedling development, 117<br />
for stored rice, 553,554<br />
Temperature characteristics (of<br />
soils). 312-315,320-322<br />
Tempering, 590<br />
Tertiary roots, 120<br />
Tertiary tillers, 109<br />
Texas, vii<br />
early rice <strong>production</strong> in, 76-79<br />
grain types grown in, 289<br />
growers <strong>and</strong> millers associations<br />
in ,81<br />
immigration to, 75<br />
rice <strong>production</strong> in, viii<br />
USDA-ARS in, 178<br />
Texture, soil, 305,358<br />
Thai Jasmine rice, 191<br />
Thail<strong>and</strong>, 4<br />
germplasm resources in, 611<br />
harvesting in, 519<br />
marketing competition with,<br />
485,486<br />
size of Tice farms in, 69<br />
Thermal characteristics (of soils),<br />
312-315<br />
Thermal time (degree days), 118<br />
Thermosensilivity, 96<br />
Thiobencarb, 461-463,465,471<br />
Three-leaf stage (seedlings), 118<br />
Threshability, 181,499<br />
Threshers, 493-495<br />
in harvesters, 497,498<br />
power threshers, 520-528<br />
Threshing:<br />
combine setting for, 511<br />
by h<strong>and</strong>, 520
Index 641<br />
in rice combine harvesters,<br />
509-512<br />
Throw-in threshers, 525<br />
Thurber, John, vii, 69<br />
Tidal flow water cultivation, 70-71<br />
Tidal-powered rice mill, 71-72,75<br />
Tidal swamp agroecosystems, 15<br />
Tillage, 283-284,286-287<br />
Tillage pan (p), 303<br />
Tillers, 104,105,109,110,121<br />
Tillering, 119-120<br />
breeding for, 179-180<br />
light for, 137-138<br />
Tiller leaf, 109<br />
Tissue culture, 208-209<br />
TNCs (total nonstructural carbohydrate<br />
concentrations),<br />
188<br />
Total field loss, 529<br />
Total mass, 569<br />
Total nonstructural carbohydrate<br />
concentrations (TNCs), 188<br />
Total yield, 569<br />
Traction assistance (harvesting),<br />
499, 528-529<br />
IVade associations, 81<br />
Transcontinental railroad, 73<br />
Transformation, genetic, 209<br />
Trapping (of rodents), 563<br />
Trash, liarvesting, 514-516<br />
Traverses (of drier), 590<br />
Tricarbocyclic diterpenes, 230<br />
Triclopyr, 458, 463,464, 471<br />
Tricyclic diterpenes, 238<br />
Trifluralin, 464<br />
Triple superphosphate (TSP), 366<br />
THploid plants, 161<br />
THsomic rice plants, 161-162<br />
Tfopleal japónica cultivái s, 95-97<br />
Tropical fices, classification of, 88<br />
Ibilica, 147<br />
TSP (triple superphosphate), 366<br />
Hirn flows, 590<br />
T\iraing time, 536<br />
24-hour Penraan-Monteith<br />
equation, 307<br />
2,4-D, 285, 464, 471^72<br />
United States. See also specific topics<br />
arthropod pests in, 437-451<br />
ciiltivars grown in, see U. S. rice<br />
cultiva rs<br />
exports of rice from, vii, 68<br />
harvesting in, 499-500<br />
<strong>history</strong> of rice industry in, see<br />
American rice industry<br />
marketing of rice in, 473-483<br />
<strong>production</strong> of rice in, vii—^viii,<br />
4,68-69. S ee also U, S. rice<br />
<strong>production</strong><br />
regional researcli laboratories in,<br />
82<br />
rice breeding programs in, 178<br />
rice policy in, 475-477<br />
role of rice entomologists in,<br />
450-451<br />
supply <strong>and</strong> dem<strong>and</strong> conditions<br />
in, 473-475<br />
U.S. Department of Agriculture—■<br />
Agricultural Researcli<br />
Service (USDA—ARS), 178,<br />
598- 602,606<br />
U.S. Department of Agriculture<br />
(USDA);<br />
agricultural experiment stations<br />
of, 80, 599<br />
breeding programs of, 87,178<br />
introductions of rice by, vii<br />
<strong>and</strong> subsidized crop in.suiance,<br />
477<br />
U.S. National Plant Germpiasm<br />
System (NPGS), 598-607<br />
Crop Germpiasm Committees,<br />
604-605<br />
Dale Bumpers National <strong>Rice</strong><br />
Researdi Center, 605-606<br />
Germpiasm Resources<br />
Information Network,<br />
606<br />
international resources, 607-612<br />
National Center for Genetic<br />
Resources Conservation,<br />
606<br />
National Small Grains Collection.<br />
599- 604<br />
Plant Germpiasm Quarantine<br />
Office, 606,607<br />
rice improvement <strong>and</strong> use fif,<br />
612-623<br />
U.S. rice cultivars, 87-99<br />
agronomic cliaracteri.stics of,<br />
96- 97<br />
<strong>and</strong> classification of tUltivars,<br />
88-89<br />
derivation of 89-96<br />
future trends in, 98-99<br />
grain quality characteristics of<br />
97- 98<br />
long-grain, 90-91,9*4-95<br />
medium-grain, 95-4»6<br />
short-grain, 95-96<br />
U.S. rice <strong>production</strong>, 272-294. See<br />
also specific topics<br />
crop rotations/double-cropping,<br />
289, 290<br />
ciiltivar selection, 289<br />
drying, 293-294<br />
harvesting, 291-294<br />
<strong>history</strong> of, 67-84<br />
l<strong>and</strong> selection/formation for,<br />
272-276<br />
planting dates, 287-288<br />
planting methods, 281-284<br />
ratoon <strong>production</strong>, 290-291<br />
seeding rates, 288<br />
tiJage practices, 286-287<br />
water management, 284-286<br />
water requirements for, 276-281<br />
Unloading time, 536-537<br />
Upl<strong>and</strong> rice, vii<br />
Urea, 341-343<br />
Urea-ammonium nitrate, 342<br />
Uruguay, 485-487<br />
USA <strong>Rice</strong> Council, 478<br />
USDA, see U.S. Department of<br />
Agriculture<br />
USDA-ARS, see U.S. Department of<br />
Agricult ure—Agricultu ral<br />
Research Service<br />
USDA-ARS <strong>Rice</strong> Quality Research<br />
Laboratory, 97<br />
USDA National <strong>Rice</strong> Quality<br />
Laboratory, 479<br />
Value (soil color), 304<br />
Varietal improvement programs,<br />
see Breeding<br />
Vascular bundle, 112<br />
Vavilov Institute of Research (Soviet<br />
Union), 612<br />
Vegetative lag phase, 121<br />
Vegetative phase, 108,113-120<br />
Vegetative propagation (ratooning),<br />
167<br />
Vertisols, 298,319<br />
Vibramat.attachmen.ts, 509<br />
Vietnam:<br />
germpiasm resources in, 611-612<br />
market competition with, 485,<br />
487<br />
rice <strong>production</strong> in, vii, 247<br />
Vigyaii Parishad Kendra<br />
Agi'iculturnl Station<br />
(India), 609<br />
Vilmorin Audrieiix Co., 600<br />
Viral diseases, 430-431<br />
Volatile compounds, 224, 225<br />
Walker-type combines, 500, 512<br />
Ward, D.J., 601<br />
WARDA, see West Africa <strong>Rice</strong><br />
Development Association<br />
Warera (Wataribunc) rice, 80<br />
Watabe, T„ 609<br />
Water, vlii, See also Water<br />
management<br />
breeding for reduced use of 188<br />
conservation of, 280-281<br />
for gerraination/seedliiig<br />
development, 131,133<br />
<strong>and</strong> levee construction, 274-276<br />
19th century canal <strong>and</strong> irrigation<br />
systems, 78<br />
<strong>and</strong> plant maturation time, 180<br />
<strong>production</strong> requirements for,<br />
276-281<br />
quality of, 277-278<br />
required volume of, 279<br />
soils <strong>and</strong> balaiice/use of 305-307
642 Index<br />
t [<br />
sources of, 277<br />
temperature of, 278-279<br />
Water ciiltivalion, tidal How, 70-71<br />
Water extraction bioassay method,<br />
233<br />
Water infiltration, redistribution of<br />
soils <strong>and</strong>, 319-321<br />
Water leveling, 273-274<br />
Water management, 284-286. See<br />
also Irrigation<br />
nitrogen fertilizer in alternative<br />
systems, 355-356<br />
in ratoon <strong>production</strong>, 290-291<br />
seasonal water balance equation,<br />
305<br />
<strong>and</strong> soils, 305-307<br />
Water mold, 415-417<br />
Water rice mill, 71-72, 75<br />
Water-seeded systems, 281-282<br />
nitrogen fertilizers for, 341-342,<br />
352-353 ;<br />
phosphorus fertilizers for, 366<br />
presprouted rkc in, 416-417<br />
seedbed preparation for, 286<br />
seeding rates for, 286<br />
Water weevils, rice, 438,440-443<br />
Watkins, fabez Bunting, 73<br />
Waxy endosperm mutants, 165<br />
Waxy genes, 189-190<br />
Waxy (sweet) rice, 192<br />
Webb, B. D„ 82<br />
Webster, Robert K., 82<br />
Weed control, 458-472<br />
acifluorfen for, 466<br />
bensulfuron for, 467<br />
bentazon for, 467<br />
bispyribac for, 467<br />
burndown treatments, 464<br />
carfentrazone for, 467<br />
clefoxydim for, 467<br />
domazone for, 468<br />
in conservation tillage rice, 464<br />
in continuously flooded rice, 462<br />
cyhalofop for, 468<br />
in delayed-flood rice, 460-462<br />
<strong>and</strong> delayed phytotoxicity<br />
syndrome, 466<br />
fenoxaprop for, 468<br />
flooding as, 188, 460-462<br />
glufosinatc for, 468-469<br />
glyphosate for, 469<br />
halosulfuron for, 469<br />
imazethapyr for, 469<br />
for jointvetch, 463<br />
molinate for, 469-470<br />
for nutsedge, 463<br />
pendimethalin for, 470<br />
propanil for, 470<br />
quinclorac for, 470-471<br />
for red rice, 464-466<br />
rice allelopathy use for, 221<br />
rice weeds, 459-460<br />
salvage weed control, 463-464<br />
for spranglctop, 463<br />
tliiobeiicarb for, 471<br />
traditional programs for,<br />
462-463<br />
tridopyr for, 471<br />
2,4-D for, 471-472<br />
winter flooding for, 287<br />
Weedy rice, 55-57. See also specific<br />
types, e.g.; Red rice<br />
West Africa, 56<br />
West Africa <strong>Rice</strong> Development<br />
Association (WARDA), 163,<br />
607<br />
Western Regional Research<br />
Laboratory, 82<br />
Wliite combines, 513<br />
Wliite leaf streak, 428<br />
Wliite tip nematode, 428<br />
"Wide compatibility* allele, 89<br />
Wild rice. See also Z izan ia palustris<br />
L<br />
in Asia, 49<br />
evolution of, 9-11<br />
weedy species of, 55, 56<br />
William Deering <strong>and</strong> Company, 75<br />
Willows soils, 301,302,305<br />
Wilson, James W., 80<br />
Windrow pickups (combines), 509<br />
Wingate, Dan, 76<br />
Winter flooding, 287<br />
Winter nurseries, 193-194
Woodward, A. W., 82<br />
Woodward, Henry, vii, 69<br />
World Food Program, 486<br />
World Trade Organization (WTO),<br />
476, 485, 486<br />
Wright, S., vii, 78,80, 95<br />
WTO, see World lirade<br />
Organization<br />
X (fragipan), 303<br />
Yeast artificial chromosome (YAC)<br />
library, 206<br />
Yeh, Birdie, 163<br />
Yellowing, 575<br />
Yield(s). S.ee also specific topics, e.g.:<br />
Fertilizers<br />
breeding for, 96-97, ISO<br />
components of, 113,114<br />
genetic engineering for, 210-211<br />
milled rice yield, 559<br />
milling, 97,190<br />
of ratoon crops, 290<br />
rice diseases <strong>and</strong>, 414-415<br />
as rough rice at 14% moisture,<br />
124<br />
<strong>and</strong> salt content of water, 277<br />
<strong>and</strong> time of tilling, 283<br />
Y-leaf N concentration, 355-356<br />
Zen i til cultivar, 95<br />
Zhongxian 3037 cultivar, 161<br />
Zinc, 148<br />
<strong>and</strong> bronzing, 431<br />
deficiencies in, 272,377<br />
diagnosis of deficiency in,<br />
377-380<br />
fertilizing witli, 377-382<br />
forms/behavior of, 376-377<br />
in soil nutrition, 377-382<br />
Z izan ia, 2 9 ,30<br />
Z izania a q m tic a L., 4<br />
Z izan ia palustris L., vii, 4
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