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Section 4: Post-harvest Processing
Part 17; Drying
Part 18: Paddy Storage
Part 19: Milling
Part 20: Milled Rice Storage
63
65
67
69
Section 5: The Future of Rice
Part 21 : Environmental Concerns in Rice Production
Part 22: Efforts in Sustainable Rice Farming
Part 23; Genetic Improvement
71
73
75
Conclusion
References
77
79

Section 1: Introduction to Rice Production
Part 1: Brief History of Rice Cultivation
Rice is one of the three most important crops in the world (the other two being com and
wheat). An estimated 3.5 billion people, more than half of the world’s population, consume
rice as a staple food. It is grown in every continent except Antarctica and is the source of
livelihood for more than one billion people. Ninety percent of rice production is concentrated
in Asia, where rice is grown in roughly 200 million, mostly small-scale (less than 1 ha), rice
farms. Two species of rice are currently cultivated: Oryza sativa, or Asian rice, and Oryza
glaberrima, or African rice. The former is the most common species grown worldwide,
whereas the latter’s cultivation is limited to West Africa, from where it is believed to have
originated.
Archaeological evidence has revealed that the cultivation of rice {O. sativa) began along the
middle Yangtze and upper Huai rivers in China. Rice and farm tools more than 8000 years
old were discovered there. From these rivers, the practice is thought to have moved
downwards to Thailand in the next 2000 years. But older evidence of rice as a food source
exists. Remains of rice plants dating back to 10,000 B.C. were found in Spirit Cave on the
border of Thailand and Myanmar. Pieces of pottery with printings of rice grains and husks
believed to be 4,000 years old were also discovered in Non Nok Tha, Korat, Thailand.
From Thailand, rice cultivation spread throughout South and Southeast Asia. The armies of
Alexander the Great are credited for bringing rice to Europe in 300 B.C through West Asia
and Greece. Traders from India and Indonesia brought rice to East Africa in 800 A.D. There
are two different versions of how rice arrived in North America. One version is that African
slaves brought rice with them when they arrived in the southern United States; in the other
version, a ship captain is said to have given rice to colonizers in the Carolinas in exchange for
repairs to his damaged ship. Portugal and Spain were instrumental in bringing rice to South
America. Portugal introduced rice to Brazil, whereas Spain introduced it to the rest of South
and Central America.
There is little information on the history of the cultivation of O. glaberrima. It is genetically
descended from O. barthii, which can still be found growing wild in Africa. Evidence points
to its earliest domestication in the Upper Niger River’s inland delta 2000 to 3000 years ago.
Whereas O. sativa has extended its range of cultivation to most continents, O. glaberrima has
remained limited to West Africa. The reason for its limitation has been attributed to the
species’ lower grain quality compared to the more superior Asian rice, although it exhibits
better tolerance to environmental stresses and some pests and diseases. Recent breeding
efforts by African scientists between O. glaberrima and O. sativa have resulted in a variety

Top 20 rice producing countries in the world (2010):
1. China ( 197.2 M metric tons)
2. India (120. 6 M metric tons)
3. Indonesia (66.4 M metric tons)
4. Bangladesh (49.3 M metric tons)
5. Vietnam (39.9 M metric tons)
6. Burma (33.2 M metric tons)
7. Thailand (31.5 M metric tons)
8. Philippines ( 15.7 M metric tons)
9. Brazil (11.3 M metric tons)
10. United States (11.0 M metric tons)
11. Japan (10.6 M metric tons)
12. Cambodia (8.2 M metric tons)
13. Pakistan (7.2 M metric tons)
14. South Korea (6.1 M metric tons)
15. Madagascar (4.7 M metric tons)
16. Egypt (4.3 M metric tons)
17. Sri Lanka (4.3 M metric tons)
18. Nepal (4.0 M metric tons)
19. Nigeria (3.2 M metric tons)
20. Laos (3.0 M metric tons)
Source: FAO.org
8

Section 2: Basics of Rice Growing
Part 4: Types of Rice Culture
The methods by which rice is cultivated can be distinguished into four distinct types;
1. Irrigated lowland
Also called paddy rice culture, irrigated lowland rice culture is the most common type
used in vast areas of South, Southeast, and East Asia. Irrigated lowland rice refers to
rice grown in bunded fields in low lying areas that obtain their water from irrigation
canals that are sourced from bodies of water such as dams, rivers and lakes. Farmers
can control the amount of water that is fed to the rice field. When sufficient rainfall is
present to wet the fields, no irrigation is necessary. This system has benefited the most
from research on varietal development and produetion practices including efforts in
irrigation improvement through the construction of dams and channels that divert
water to rice fields. Because of this, it has been possible for rice farmers to grow rice
two times a year from the traditional one crop per year. Irrigated lowland rice culture
can yield from 4 to 6 tons per hectare of rice.
2. Rainfed lowland
Rainfed lowland rice is grown in low-lying valleys and deltas in tropical regions that
benefit from the natural flooding that occurs during the monsoon season. It is the
second most common system of rice production in South and Southeast Asia after
irrigated lowland rice. The working definition for rainfed lowland rice, according to
IRRI, is “It is rice, usually transplanted, that is grown in leveled, bunded fields that are
shallowly flooded with rainwater.” This definition includes the practice by which
lowland rice farmers collect rainwater in ditches then provide the water to the paddies
during the absence of rain. However, there is sufficient crop loss in times of drought
in this type of culture because no alternative water sources are available. Although the
potential for improving production is very high, rainfed lowland rice culture has not
been the focus of much research. Rice yields are generally from 2 to 3 tons per
hectare.
3. Rainfed Upland
Upland rice refers to rice grown in areas that rely only on rainwater (i.e. no irrigation)
9

ut does not experience long periods of flooding or submergence as in rainfed lowland
rice. Rice farmers take advantage of frequent rainfall by planting in lowland areas and
on the slopes of hills and mountains. Rainfall flows down from the top and is
naturally collected in the rice paddies. Southeast Asia accounts for much of upland
rice production, although it is also being practiced in South Asia and China. Because
of its reliance on rainfall, the plants are usually subjected to periods of drought stress.
As such, yield from upland rice culture can vary significantly for each growing cycle.
Upland rice culture is also practiced in rotation with other crops, unlike the other types
of rice culture. Rainfed upland culture yields rice at 1 to 2 tons per hectare.
4. Deepwater
Deepwater rice is cultivated along low-lying areas in rivers, deltas, estuaries, and
swamps. The practice is common in the tropical regions of Asia and in Sub-Saharan
Africa. Generally, rice plants that are submerged to a depth of at least 50 cm for long
periods are considered deepwater rice. In this type of culture, the rice farmer relies on
rainfall and the natural flooding caused by the swelling of the bodies of water nearby.
The farmer has no control of the amount of water available to the rice field, and there
may be periods of drought and flood throughout the growing season. The rice plants
must be able to tolerate being dry or being submerged for periods of time and to high
levels of salinity (as in the case of flooding near estuaries). Deepwater culture yields
0.5 to 2 tons per hectare of rice.
NOTE:
The terms “upland” and “lowland” does not necessary refer to the topography or elevation of
the planted rice. The more appropriate term would be “dryland” and “wetland”, respectively,
because they refer to the surface hydrology of the soil in which the rice is planted. However,
because the terms upland and lowland have been in use for so long, its use is not likely to
change.
Part 5: Assessing Climate, Soil and Water
When considering whether to grow rice or not, and specifically which type of rice culture
would be most appropriate for a given area, the farmer needs to carefully study the ecosystem
in which the rice plant will be grown. Some points to consider include the following;
10

г 1.
hydrology
2. climate (rainfall and temperature)
3. soil quality
4. biological constraints (weeds, diseases, and insect pests)
5. socioeconomic factors
1. Hydrology
Knowing the water source and how much and how often there is access to this water
is the most vital information that will be needed. The topography determines how
efficiently water is delivered. The farmer will also need to remember that the water
requirements of rice depends on its variety, particularly how long it takes to reach
maturity from the time it is planted on the field (either by direct seeding or
transplanting). Water needs also depend on the temperature throughout the growing
season. High temperatures will naturally mean higher transpiration in rice plants and
higher rates of evaporation, which in turn demand higher water usage. Rice plants can
withstand a few days of drought, but they thrive best with a constant supply of water.
The water requirements of rice extend beyond that of the biological needs of the plant.
Water is also needed for land preparation, during which losses from seepage and
percolation normally occur, and the need to drain excess water must also be taken into
account. The importance of water supply for rice cultivation cannot be stressed
enough. Rice is the only cereal crop that is adapted to withstand submerged
conditions for lengthy periods.
2. Climate
a. Rainfall
The amount of rainfall that a given area receives needs to be considered especially
if water supply through irrigation is a limited option. The construction of
catchment areas or ponds to store rainwater is important whether rainfall is
abundant or not. This is because the occurrence of rainfall eannot be controlled,
and the sensitivity of the rice plant to drought at specific growth stages can greatly
affect the number of grains that it produces. Rice is therefore best suited to areas
where the supply of water (artificial or natural) is assured. Lowland rice culture
requires an average of 200 mm of monthly rainfall, whereas upland rice culture
requires half of that. At the vegetative stage, rice plants need about 125 cm of

ainfall. During the ripening stage, water is not a necessity because rice fields are
left to dry up in preparation for harvest.
b. Temperature
Rice is native to the tropical and sub-tropical zones where day and night
temperatures are relatively constant, but in temperate or sub-temperate areas, a
period of three to six months of warm weather is necessary to complete one
growing cycle. Starting by growing seeds indoors during the colder months could
be helpful in areas with short summer months. Rice grows best at a mean
temperature of about 22°C throughout the growing period. Rice is sensitive to
temperature fluctuations at different stages of its development. For instance, it
requires a minimum of 10°C to sprout, the optimum temperature for flowering is
around 23°C, and for grain formation it is around 21“C. Temperatures above 22°C
accelerate respiration, which in turn reduces the period of grain filling. Rice can
tolerate temperatures of up to 40°C.
3. Soil quality
Water retention capacity is the most important determining factor for choosing the
best soil type for rice. Rice grows best in clay and loamy type soils such as silty clay,
silty clay loam, and loamy, especially those containing organic matter. It is also
beneficial to assess the soil’s nutrient content to determine if additional enrichments
(i.e. fertilization) will be required. Soil pH affects nutrient availability and in the case
of rice, a neutral pH is the most favorable for growth. Nitrogen, phosphorus,
potassium, iron, manganese and zinc are the six most essential nutrients for rice.
Under submerged conditions, the pH level of soil generally falls between 6.5 and 7. At
this range, all the essential nutrients are
more easily absorbed by the rice plant.
4. Biological limitations
a. Weeds
Weeds that resemble rice, called “weedy rice”, can easily infest rice fields,
particularly those that are direct-seeded. This is because direct-seeded fields are
initially not flooded to allow the rice seeds to germinate and attain a certain height.
This period of dryness encourages weedy rice to germinate along with the rice
12

seeds and establish themselves even after the field is fiooded. Weedy rice is very
competitive, and some species can even grow more vigorously than the rice itself.
When allowed to mature and produce seeds, weedy rice can continue to be a
nuisance in succeeding growing cycles. In transplanted fields, the fiooded
conditions are a deterrent to weedy rice germination, and even when they do
germinate the rice plants are already at a more competitive stage of growth. Rice
fields can be more easily weeded at this point because weedy rice is easier to
detect.
Weedy rice has become a big problem in the major rice-producing regions of the
world, including Asia and the Americas.
b. Diseases
Rice is susceptible to many fungal and bacterial diseases particularly those
attacking the leaves and panicles. The disease-causing bacteria and fungi can be
present in the field through many growing cycles and complete eradication is
impossible. Planting rice varieties that are disease-resistant is the best option in
combating disease occurrence in the field, but this may not be a permanent
solution because new generations of fungi and bacteria that can overcome host
resistance develop quickly. Several cultural management practices can be followed
to minimize the occurrence and damage caused hy these diseases.
c. Insect pests
Insect pests are not only harmful because of the damage they cause to the rice
plant, they can also act as vectors for viral diseases. Furthermore, the injury they
cause to the plant serves as a point of entry for bacterial and fungal diseases. Even
after harvest, if the field is not properly cleared, insects can feed on the debris or
use them as shelter; thus allowing them to infect the next cropping cycle. Insect
pests can attack rice at various stages of its development, so careful monitoring of
any insect-related damage is essential in determining a course of action for their
management.
d. Socioeconomic factors
Capital, land, labor, availability of input, and the level of knowledge are just some
of the socioeconomic factors that determine whether growing rice will be a
productive venture for any farmer. Many rice farms in Asia are maintained by
13

small farmers and their families who grow rice in less than one hectare of land.
Profit from such a small space is minimal, although labor costs are irrelevant
because family members are never paid for their work. Most of the operation such
as planting and harvesting is done by hand or with the aid of an animal particularly
during land preparation. Rice farming techniques are passed down from one
generation to another. In developed countries such as those in Europe and the US,
rice operation is completely mechanized: from land preparation to planting to
harvesting. As such, growing rice in these countries would require higher capital
and labor costs than growing rice in developing countries.
Part 6: Tools, Equipment and Machinery
Equipment and machinery used in rice production include those for land preparation,
planting, harvesting, drying and storage. The use of equipment varies by region and economic
factors. In poor farms in South and Southeast Asia, many farmers still use hand tools to
prepare the land for rice planting. Other farmers attach land preparation implements to
animals such as water buffalos and oxen to break up the soil. Two- and four-wheeled tractors
make land preparation an easier and faster process. Planting and harvesting are also done
either manually or with the aid of hand-powered equipment or tractors. In developed
countries, the entire rice production process is mechanized and various tractors are used for
land preparation.
The following are the implements needed in the production of rice through the various stages
of operation.
Activity T ools/Equipment/Machinery Use/Purpose
Land preparation
tiller/cultivator, plow, harrow,
leveling board
to loosen and break up the
soil into small clumps and
level the land
Planting seeder to transplant rice seedlings
in rows; can be handoperated
or motorized
Harvesting harvester to separate the panicles from
the plants
14

Threshing (mechanical) thresher to remove the grains from
the panicles
Drying flash dryer to remove moisture from the
grains to lengthen storage
life
Milling miller to separate the husk and bran
layer from the grain
Storage storage facility to store grains prior to or
after milling.
Part 7: Preparing the Soil
1. Rice paddy construction
Lowland rice culture begins with the construction of a rice paddy. A paddy is simply an area,
usually square or rectangular, where water is impounded for the growing of rice. Rice paddies
are constructed by excavating the existing soil to create levees (called bunds) that trap water
and dikes that allow the drainage of excess water. The size of one paddy is determined by
such factors as topography, contour, and the natural flow of run-off water from irrigation
sources or rainfall.
2. Land preparation
Land preparation is an integral part of rice production. Good land preparation results in soil
that is properly conditioned for establishing and growing rice seedlings. The purpose of land
preparation is three-fold:
a. To till the soil to a depth that allows good root development of rice plants;
b. To control weeds; and
c. To level the field so as to ensure even water distribution, which in turn ensures proper
plant growth and weed control. Leveling also helps in drainage by facilitating the
removal of excess water.
Tillage refers to the practice of disturbing the soil surface to prepare it for plant cultivation.
Tilling also serves the purpose of destroying insect pests and their habitats, and the addition
of lime and basal fertilizers when needed. Tillage can be done on dry fields typical of upland
rice culture or on wet fields typical of lowland rice culture. Various types of plows and
harrows are used for this purpose. The choice of implement will depend on the size of the
farm and the cost.

3. Steps in land preparation
1
a. Plowing
Plowing (also referred to as primary tillage) is done either after harvest or at the start
of the following wet season. The soil is inverted to a depth of from 10 to 15 cm to
eliminate weeds by destroying them at the root level, aerate the soil, incorporate plant
debris (as organic fertilizer), and contain rainwater. The time to plow depends on the
type of soil and its level of saturation. Clay soils often need flooding to become fully
saturated before plowing, whereas loamy or sandy soils can be plowed even below full
saturation.
i. Animal-powered systems use the moldboard plow (common in Asia);
ii. Two-wheeled tractors (hand-powered or motorized) use the moldboard plow
or the more preferred disc plow (more fuel efficient and can be better at
overcoming obstructions);
iii. Four-wheeled tractors use three- or seven-disc and offset plows. In upland rice
culture, tined plows are better at disrupting the soil. However, this type of plow is
not yet available in the Asian market.
Plowing produces large clumps of soil or peds and leaves the field uneven. Therefore,
secondary tillage is needed.
b. Secondary tillage or harrowing
In secondary tillage, the large clumps dug up by the initial plowing are reduced to
smaller clumps that enable proper planting of seedlings. The first step in secondary
tillage is to plow the field again; this time at a shallower depth. After plowing,
harrowing is carried out to puddle the soil (i.e. to break the clumps into smaller pieces
such that the soil is turned into mud).
i. Animal-powered systems use moldboard plows and peg-tooth harrows;
ii. Two-wheeled tractors use the moldboard plow or disc plow and the rotovator
or peg tooth harrow;
iii. Four-wheeled tractors use seven-disc or offset plows and rotovators for
harrowing. Puddling is done using rotovators and leveling boards or cage wheels
16

and harrows.
In both two-wheeled and four-wheeled tractor systems, a cage wheel is attached to
the tractor to provide traction. The cage wheel also aids in puddling the soil.
The two most common problems when tractors are used in secondary tillage of
flooded soils are traction and flotation. In clay soils, the farmer is essentially working
with mud. As the tractor moves along, the mud can stick to the tires and render the
tractor immobile. In sandy soils, flotation problems occur when tractor tires slip and
sink as it breaks down the compact layer of the soil surface.
c. Leveling
Leveling ensures that the field on which rice will be planted is even. When a rice field
is evenly leveled, water is distributed equally throughout. An uneven field requires
more water to cover its entire area. When some parts of the field are not submerged,
weeds could grow and become not just a nuisance, but also a host for insect pests and
diseases. If some parts of the field receive less water than other parts, the growth and
development of the rice plant could be hindered, thus resulting in plants that mature at
different times or do not attain their optimum growth, potentially reducing yield.
Leveling of the land can be done using animal-powered implements or two- and fourwheeled
tractors. The principle of leveling is simple: move the soil from higher areas
to lower areas in the field.
Steps in leveling:
i. Conduct a topographic survey to determine the high and low points in the field;
ii.
iii.
iv.
Create a topographic map based on the survey;
Mark the high and low areas in the field (e.g. use flags);
Move soil from the high to the low areas;
V. Repair levees (bunds) that were removed to accommodate soil transfer.
If an entire field contains several paddies, it may be necessary to temporarily remove
bunds to facilitate the transfer of soil. In cases where the high point is far from the low

point (i.e. >50m), it is advisable to remove soil from a midway point to the low point,
then transfer soil from the high point to the midway point. The idea is to find the most
eost- and time-efficient way to transfer the soil.
i. Animal-powered systems use harrows with leveling boards. Leveling a one hectare
area can take 12 days.
ii. Two-wheeled tractors use harrows with leveling boards. Leveling a one
hectare area can take seven to eight days.
iii. Four-wheeled tractors use tractor blades (for lowland areas) or drag buckets
(for upland areas). Leveling a one hectare area can take eight hours when using
tractor blades and four hours using drag buckets.
Part 8: Deciding on the Type of Rice to Grow
1. Rice classification
Rice cultivars are divided into two subspecies: indica and japónica. There are various
morphological and physiological differences between the two; the most distinct being that
indica rice are long grained, whereas japónica rice are sticky and short grained. Indica rice is
grown in lowland rice culture and is the more prevalent subspecies. .Japónica rice is
cultivated in upland rice culture and is more widely eaten in East Asia. Over 40,000 rice
varieties have been developed within these two subspecies. Each variety is unique in its grain
characteristics, nutritional content, and growing conditions. Some of the more popular rice
varieties include basmati, jasmine, arborio, and brown.
There are thousands of rice varieties currently being planted around the world, so there are
several factors to consider when choosing the variety of rice to grow. The first step is to
determine which cultivars are grown in the region where rice is to be planted. This is
important because such cultivars will most likely be adapted to the region’s climate and have
been bred for resistance to pests and diseases that are common in the area. Cultivar
information can be obtained from the local agriculture office or from academic institutions.
Rice varieties can be grouped according to various classifications such as pest and disease
resistance, type of grain, texture and flavor, or days to maturity. It is important to keep in
mind that new cultivars continue to be released, so keeping track of them and their
characteristics may help in the decision-making process.
18

a. Type of grain (long, medium, short)
The choice may very well be dictated by demand. Consider which type is more
commonly sold or consumed in the market, unless the farmer wants to cater to a
specialty market. Specialty rice are varieties that have different processing and
cooking requirements than the commonly sold long, medium and short grain types.
Examples of specialty rice are basmati, arborio and glutinous rice.
b. Pest and disease resistance
Determine which pests and diseases are prevalent in the area where the rice will be
grown. Choose cultivars that are resistant or tolerant to such pests and diseases.
c. Days to maturity
Rice plants generally take 90 to 120 days to reach maturity. In major rice-producing
areas, planting cultivars with short maturity enables the farmers to plant for two
growing cycles. Such cultivars are also the choice in regions with short summer
months or areas that experience monsoon rains. Upland rice varieties generally take
longer to reach maturity.
d. Texture, aroma and flavor
Texture refers to how rice feels when it is cooked. Consumers generally have
preference for certain textures over others. Rice texture can be nutty, soft, chewy, or
sticky. Aroma and flavor refer to the smell and taste of cooked rice. Aroma can be
fragrant, roasted, or woody. Flavor can be earthy, sweet, or starchy.
Surveys have shown that the aroma and taste of cooked rice is a major factor in
consumer preference for one variety over another. However, aroma and flavor are not
just determined by the riee variety; they are also affected by cultural management
practices, harvesting and storage methods, and even the type of eooker.
Part 9: Seed Germination and Seedling Maintenance
A good harvest begins with good seeds. Once the farmer has deeided which variety to plant,
finding a reliable supplier of high quality seeds is the next logical step. Examining the visual
quality of the seeds and testing their germinability are important in determining how the seed
lot will perform onee planted. High quality seeds have the following characteristics:
19

a. Genetically trae to its kind (often referred to as varietal purity);
b. Whole and evenly sized;
c. No damage or deformity;
d. Not carriers of seed-bome pathogens, pests and diseases;
e. Viable (with at least 80% germination rate and good vigor);
f Have no impurities such as weed seeds, seeds from other crops, or inorganic matter;
and
g. Have no discoloration on the kernel surface (or less than 25% of the surface area).
Government institutions provide seed certifications for seed producers that ensure seeds sold
to farmers are of high quality and are genetically pure. Seeds are classified as breeder,
foundation, registered, and certified based on their genetic purity. Certified seeds are those
that are commercially available. Many poor farmers in Asia use the harvested seeds from the
previous crop for the next cropping cycle. Such seeds do not perform as well as certified
seeds, especially if the growing conditions were not optimal.
For farmers who have purchased seeds, it is important to take seed samples from different
bags and examine them for the previously mentioned physical attributes. Seeds can be
sampled by number (e.g. for germination tests and seed-bome diseases) or by weight (e.g. for
impurities and varietal purity). It may also be necessary to test for seed-bome diseases using
standard laboratory procedures.
1. A simple germination test (source lRRl.org)
Materials;
3 waterproof containers (e.g. tray)
Water absorbent material such as cotton, tissue or cloth for each container
Seeds
Water
20

Procedure:
a. Line each container with water-absorbent material that has been pre-soaked with
water;
b. Obtain seed samples from several bags and mix;
c. Take three samples of 100 seeds each from the mix;
d. Spread the seeds evenly on the soaked material in each container (one sample one
container);
e. Cover the seeds with another layer of moist material;
f. Keep the containers at room temperature in a shaded area away from drafts and any
source of contamination;
g. Check daily to ensure that the absorbent material remains moist;
h. On the fifth (5th) and tenth (10th) day, count the number of germinated seeds in each
container.
i. Compute the germination rate:
number of germinated seeds
X 100 = germination rate (%
total number of seeds in the container
j. Obtain the average from the three samples
The higher the germination rate, the higher the seed vigor. Faster seed germination is a good
indicator that the seedling will establish well once planted in the field. Seedlings that have
good vigor at the planting stage are able to survive environmental stresses, overcome
competition from weeds and withstand or recover from insect and disease damage.
2. Testing for impurities in the seed batch
a. Take three seed samples of 100 g each from several bags;
b. Spread the seeds over a clean surface;
21

г
c. Separate weed seeds and seeds from other crops into one pile;
d. Separate inorganic matter into another pile;
e. Weigh the weed seeds and calculate the weed percentage:
Weight of weed seeds
x 100 = % weed
Total weight of sample
f Weigh inorganic matter and calculate inert matter percentage:
Weight of inter matter x 100 = % inert matter
Total weight of sample
g. Obtain the average for weed and inorganic matter percentage from three samples.
Certified seeds should contain no more than 0.08% weed seeds and a maximum of 2%
inorganic matter. Weed seeds, when accidentally planted, can become a nuisance to the rice
plant.
3. Testing for genetic purity
Each rice variety has a unique grain size and shape that distinguishes it from other varieties.
Comparing seed samples to published data for a specific variety is a simple test to determine
genetic purity of the seed lot.
a. Measuring grain dimension
i. Obtain seed samples from each bag and mix;
ii.
Collect twenty (20) seeds at random from the seed sample;
iii. Measure the length and width of each seed using a Vernier caliper or
photographic enlarger;
iv.
Obtain the length and width average from the twenty seeds;
V. Calculate the length-to-width ratio:
Average seed length = Length-to-width ratio
Average seed width
22

vi. Compare the value to published values for the variety. The value should fall
within the range specified for the variety.
b. 1000-grain weight measurement
Each rice variety has a unique 1000-grain measurement, which is the weight of 1000
of its grains.
i. Obtain a random sample of seeds from each bag;
ii.
iii.
Count 1000 whole grains from the sample;
Weigh the 1000 grains;
iv. Compare the weight obtained to the variety’s published weight for 1000
grains. The obtained value must not depart from the published value.
High quality seeds result in uniform germination, less replanting, fewer weeds, and yields that
are 5 to 20% higher.
4. Planting the seeds and transplanting the seedlings
Rice seeds can be directly seeded onto the field or germinated elsewhere then transplanted.
a. Direct seeding
In direct seeding, seeds that are either dry or pre-germinated (soaked in water for 24
hours prior to planting) are broadcasted by hand or sown using a manually operated or
motor-powered planter. In large operations, seeds are broadcasted aerially using
airplanes. In lowland rice culture, seeds are usually pre-germinated first then
broadcasted. In upland or deepwater rice culture, seeds are directly sown on the
surface of the dry soil then blended with it using a plow or harrow. Eighty to 100 kg of
seeds is needed to cover one hectare of rice field.
Direct seeding requires less labor because there is no need to prepare nursery beds for
transplanted seedlings. Seeds that are directly sown also mature seven to ten days
earlier than transplanted rice because the seedlings do not experience stress from
transplanting and root re-establishment. However, direct seeding has several
disadvantages: 1) seeds are in danger of being fed upon by birds, rats and snails; 2) the

ice seeds germinate with weed seeds resulting in greater competition between the
two; 3) rice plants tend to fall down (referred to as lodging) because they are not
planted deeply enough to allow the root systems to provide good anchorage; and 4) it
requires more seeds to plant one hectare of rice field compared with transplanting (80
to 100 kg versus 35 to 65 kg).
Types of direct seeding:
i. Broadcasting
Seeds are dispersed by hand uniformly on an even/leveled field. Alternatively,
when planting on dry land (upland culture), shallow furrows can be made on the
field using a furrower. The seeds are dispersed onto the field then a spiked tooth
harrow is used to cover the furrows with soil. In developed countries, broadcasting
seeds on a field covered with standing water is sometimes done using airplanes.
ii.
Drilling
Drilling is also done manually or with the aid of manual or motor-powered drillers
in lowland and upland conditions. In this method, furrows are first made on the
field, then the seeds are dropped into the furrows and covered with soil using a
harrow similar to broadcasting.
iii.
Dibbling
Dibbling is commonly practiced in upland conditions. It involves digging holes in
the ground then placing or dropping seeds into the holes and covering them with
soil. Dibbling is the method of choice when planting rice on sloped terrain that
cannot be plowed or harrowed.
b. Transplanting
Transplanting involves germinating seeds on nursery beds then planting the seedlings
onto the field. This planting method is the most predominant technique in many parts
of Asia. Although it requires more labor, fewer seeds are used, and because seedlings
are at an advanced stage of growth when planted, control of weeds is easier.
i. Prepare the area to be used as nursery bed. This can be at a separate location in the
farm or in one of the rice paddies. Make sure the area is leveled. You need 100 sq
m of nursery area for every one hectare area to be planted. Many rice farmers use
long sections of one or more of their rice fields as nursery beds.
24

ii. Cover the soil surface with plastic sheeting or other impermeable material.
This will help keep the germination medium moist and keep the seedlings from
developing roots into the soil underneath.
iii. Frame the edges of the nursery bed with slabs of wood or other materials that
are at least 4 cm in height. This is to prevent run-off of seeds and leaks when the
bed surface is watered.
iv. Cover the sheet with a layer of soil either from the rice field or with a specially
prepared mixture of soil, manure, and water. Four cubic meters of germination
medium for every 100 sq m of nursery area is needed.
V. Pre-germinate the seeds to be planted by immersing them in water for 24
hours.
vi. You need 12 to 25 kg of seeds (at 80% germination) for every hectare of field
to be planted if the planting rate is 1 to 2 seedlings per hill 20 cm apart. The closer
the planting space, the more seeds required.
vii. Drain the water and keep the seeds moist by wrapping them in a waterabsorbent
material such as cloth. Allow the seeds to germinate for another 24
hours.
viii. Spread the pre-germinated seeds uniformly on the nursery bed in a single
layer. Cover the seeds with a light layer of soil.
ix.
Keep the seeds moist by watering the beds twice a day.
X. Seedlings are ready for transplanting after 15 to 20 days.
xi. If planting manually, cut out manageable slabs of the seedlings and bring them
to the field to be planted.
xii. If planting using a tractor cut out larger slabs and place on the planter tray.
c. Planting the seedlings
To prepare for transplanting, the rice paddy is usually watered 24 hours prior to
planting. The paddy should be saturated but not flooded. Seedlings can be
transplanted in the rice paddy either randomly or in straight rows at depths of between
1.5 and 3.0 cm and at 3 to 6 seedlings per hill. In random planting, seedlings are
manually planted anywhere with no set distance between plants. When planting in
straight rows, lines are used as planting guides. The line can be made of metal wire,
twine or wood. It is secured at both ends of the paddy by removable pegs. Seedlings
25

г
are planted just under the line at a set distance (e.g. 20 cm apart). When one row has
been planted, the pegs are moved at a set distance (e.g. 20 cm) then more seedlings are
planted. The process is repeated until the entire paddy has been planted. Extra rice
seedlings are planted along the sides, near the levees, to be used to replace seedlings
that die within the rows. This is usually done ten days after the initial planting.
Manually operated or motor-powered planters make straight-row planting faster and
easier. Whether done manually or with the use of planters, transplanting is carried out
by working backwards on the rice paddy.
The advantages of planting in straight rows are quite obvious; 1) planting space is
optimized; and 2) cultural management practices such as weeding, fertilizing and
application of pesticides and herbicides are easier to perform.
d. Planting distance
When transplanting, there is no standard distance between hills that must be observed.
Rather, the season of planting, the level of fertility in the soil, and the rice variety
determines the distance. Proper spacing increases grain yield because, among other
factors, it limits the chances of shading among rice plants (mutual shading), which
allows the plants to maximize their photosynthetic activity.
i. Variety
Rice varieties that grow tall, produce many leaves and tillers, and are more prone
to lodging should be spaced far apart. On the other hand, short varieties that are
not sensitive to photoperiod and do not lodge should be spaced close together.
ii.
Season
When planting during the dry season, both tall and short varieties should be
spaced closer together because solar radiation is higher. During the wet season,
plants tend to have more vegetative growth, planting them farther apart can
prevent mutual shading.
iii.
Soil fertility
In terms of soil fertility, both tall and short varieties should be planted farther apart
in fertile soils to prevent mutual shading. In poor soils, the seedlings can be spaced
closer together because tillering is more common.

Based on the previous criteria, the recommended spacing for tall and short varieties
are as follows:
1. Tall varieties
Dry season: 25 cm x 25 cm in poor soils and 30 cm x 30 cm in fertile soils
Wet season: 30 cm x 30 cm in poor soils and 35 cm x 35 cm in fertile soils
2. Short varieties
Dry or wet season: 20 cm x 15 cm or 20 cm x 10 cm in poor soils and
20 cm X 20 cm
Part 10: Crop Management
After sowing the seeds or planting the seedlings, maintaining good cultural management
practices to ensure the best growth for the plant is essential. Rice plants have different
management requirements at different stages in their development.
7. Growth stages o f the rice plant
a. Vegetative stage
This phase is characterized by the emergence of leaves at regular intervals, profuse
growth of tillers (a tiller is a plant shoot that emerges from the root), and increase
in plant height. The duration of this stage determines the growth duration of a
variety. Some early maturing varieties usually have vegetative stages that are
shorter. Others have both short vegetative and reproductive stages. The availability
of nitrogen also affects duration because it is critical in tiller formation.
Depending on the variety, it can take 15 to 25 days from germination to the
emergence of the first tiller. The plant will continue to produce tillers until it has
reached the maximum number it can produce, which is determined by genetics and
nutrient availability. Panicle initiation signals the beginning of the reproductive
stage and generally commences from 40 to 60 days after germination; this is
preceded by a vegetative lag phase wherein tillering slows down and plant height
and weight increase level off. The development of tillers may continue even after
panicle initiation until maximum tillering is achieved. Generally, transplanted
plants develop more tillers than directly seeded ones (10 to 30 vs 2 to 5). This is
because the former are planted at well-defined spaces that maximize their growth
27

potential, whereas in the latter, the plants may germinate and grow clumped
together.
Between the point of maximum tillering and panicle initiation, the rice plant is
said to be in a photoperiod sensitive stage. At this stage, the plant can differentiate
the length of day from the length of night. This is an adaptive mechanism that
ensures the reproductive stage will proceed under the most beneficial conditions
of temperature and humidity, thereby ensuring successful fertilization and grain
development. Therefore, planting must be done at the correct time of the year to
ensure that the plants are at the reproductive stage when the optimum conditions
are present. In tropical climates, such conditions occur during the start of the rainy
season. In temperate climates, late spring and early summer are the best times. It
is important for the farmer to be aware of the photoperiod sensitive stage of the
variety to be planted, so that the planting date can be adjusted accordingly.
b. Reproductive stage
This stage is characterized by a series of developmental events that begins with a
decline in tillering, flag leaf emergence, booting or culm (or stalk) elongation,
heading (the emergence of the spikelet-bearing panicle from the leaf sheath), and
flowering (when the spikelets on the panicles open to reveal the anthers). This
stage generally lasts on average 45 days for most varieties.
Panicle emergence from each tiller within the same plant can differ from 10 to 14
days. Flowering on the panicle occurs from the topmost spikelets to the lowermost
ones. Rice is self-pollinating and fertilization occurs within six hours of flowering
from mid-morning to early afternoon. The flowering period for any variety can last
15 days.
Each of these events is susceptible to environmental stresses that could affect
grain development and consequently yield. For instance, poor panicle exertion can
result in poor filling of grains when solar radiation is low three weeks prior to and
past the heading stage; low temperatures during flowering can also result in poor
fertilization. Varietal differences in environmental stress tolerance or resistance
exist, so it is best to obtain such information from published data about the variety
to be planted.
c. Ripening stage
The ripening stage is distinguished by several different stages in the process of
grain development: milk, soft dough, hard dough, and maturity. Ripening can take
28

anywhere from 25 to 40 days depending on the variety. The grains are considered
to have reached maturity and be ready for harvest when they have turned golden
brown and are hard and opaque. At this stage, the leaves start to decay and lose
their color.
The developing grains are susceptible to attack from sucking insects in the early
stages and birds and rats in the later stages. They are also sensitive to changes in
environmental conditions. Grain filling (during milk and dough stages) is the
process whereby starch and protein accumulate in the grain. This process is greatly
hastened when the ambient temperature increases, resulting in partially filled
grains containing undeveloped starch granules. On the other hand, low
temperatures will lengthen the grain filling period; a significant incidence of frost
will cause the entire ripening process to stop altogether.
Light intensity is another factor that affects grain filling. Carbohydrates are
synthesized during photosynthesis in the leaves and delivered to the grains. During
periods of cloudy or rainy weather, the rate of photosynthesis decreases resulting
in lower carbohydrate production and grain filling.
Part 11: Cultural Management Practices
1. Water management
a. Upland rice culture
In developing countries, rice plants grown under upland conditions are completely
dependent on rainfall for water. In developed countries, irrigation water may be
made available to the field. In both cases, it is important to ensure that the soil is
moist but not flooded; therefore, a good drainage system must be constructed to
ensure good plant growth. Flooding during the vegetative stage results in poor
tillering; during the ripening stage, grain filling is affected resulting in poor grain
quality.
b. Lowland rice culture
The largest amount of water usage during lowland rice production occurs during
land preparation when the soil is flooded to facilitate easy plowing and harrowing.
The action of breaking the soil surface results in significant water loss through
percolation and seepage. It is therefore vital that land preparation be done as
quickly as possible after flooding.
Once the seeds have been sown or the seedlings transplanted, continuous supply of
water on the field ensures good plant growth resulting in high yields. At the early

vegetative stage, water levels should be kept at a depth of about 3 cm. As the
plant grows taller, the depth is increased to 5 cm. This level is kept through the
reproductive and ripening stages until 10-15 days prior to the expected harvest
date. Draining the field at this time hastens the ripening process, inhibits further
uptake of nitrogen, and makes the field accessible during harvest.
Water scarcity
During the growth period, water may not always be available to the rice field.
There are several reasons for this: lack of rainfall, decreasing water levels in
reservoirs, pollution and contamination, salinization, breakdown in irrigation
systems, and competition from urban development. The occurrence of one or
more of the above events can greatly reduce yield and even destroy the entire crop.
The International Rice Research Institute has come up with a method to deal with
instances of water scarcity. The Alternate Wetting and Drying (AWD) method is a
mitigating measure that addresses the issue of limited water availability. In this
method, water is applied to the field a certain number of days after the
disappearance of water on the soil surface. This can be anywhere from one to ten
days. Using a “field water tube” inserted into the soil to measure how far under the
surface the water has receded, the field is flooded to a 5 cm depth when the water
level has gone down to 15 cm below the surface. This distance is referred to as
Safe AWD because no apparent reduction in yield is observed at this level of
water. Water conservation using this method is about 15%. If higher water
savings is desired, water levels below Safe AWD may be tried (e.g. 20 cm, 25 cm,
or 30 cm below the surface) as long as yields do not suffer. Thus, it may be
necessary to experiment with the levels over several growing cycles to find the one
that the rice variety being grown can tolerate.
There are breeding programs in several countries that have developed lowland rice
varieties that are able to grow in soils deprived of water. Such rice varieties are
called “aerobic rice”. They have the same qualities as upland rice varieties in that
they can be grown in soils lacking sufficient water, but they possess the superior
characteristics of lowland rice in terms of yield potential.
2. Nutrient management
a. Compost
Adding compost to the rice field for incorporation into the soil at least two weeks
before land preparation greatly improves soil quality. The compost can be made
30

up of organic matter such as animal manure, plant waste, sewage sludge, oil cakes,
and green manure (legume clippings are a great source of nitrogen). Rice straw is
an example of plant waste that can easily be added to the soil. After harvesting,
rice straw can be left on the field to compost for the next growing cycle. Although
compost contain little of the major nutrients (N, P, K), it has essential
micronutrients and other growth factors that are not found in inorganic fertilizers.
Compost also harbors beneficial microorganisms and improves soil fertility. When
left on the field to degrade, the high temperatures (>55°C) generated during the
eomposting process inhibits pathogens and reduces weed seed viability.
b. Fertilization
The best way to assess if inorganic fertilizers should be added to the soil is to
conduct a soil nutrient analysis prior to planting, espeeially if this will be the first
time the field will be used for growing rice. Detection of the levels of nutrient
defieiencies or toxicities can be managed accordingly thereby ensuring proper
growth of rice plants. Some nutrients can remain in the soil for several growing
cycles after being added, so there is always a chance of accumulation that may
lead to toxicity. The soil may also naturally contain high amounts of a specific
nutrient. Other nutrients may either be completely utilized by the rice plants or
washed out, so frequent addition is necessary.
31

г
с. Macronutrients and their roles in rice plants
Nutrient
Function
Deficiency
symptoms
Toxicity symptoms
Nitrogen
At vegetative stage:
Essential for leaf
development, plant
height, and tiller
formation.
At reproductive
stage:
Essential for panicle
formation and
spikelet number.
Reduced growth and
yellowing of leaves
starting from older
leaves to younger
ones; reduction in
number of filled
grains.
Dark green foliage;
increased lodging
due to increased
number of tillers;
higher incidence of
insect invasion and
increased disease
occurrence because
of robust growth.
At ripening stage:
Essential for grain
filling.
Phosphorus
At vegetative stage:
Promotes root
formation and
tillering and
increases stem
strength.
At reproductive
stage:
Promotes early
flowering.
At ripening stage:
Stunted seedlings;
reduction or absence
of leaves and tillers;
small and erect dark
green older leaves;
small stem diameter.
Lethargic or weak
growth; decreased
uptake of N and K;
decreased flowering;
high number of
empty grains, or
absence of grain
formation.
Causes deficiencies
in micronutrients
such as iron and zinc.
Promotes early
ripening.
32

Potassium At vegetative stage: Symptoms occur in May cause
older leaves first: deficiencies in
Leaves senesce later
resulting in a thicker
yellowish brown leaf
tips then entire leaf
magnesium and
calcium
canopy that increases
photosynthetic rate.
changes from yellow
to brown; droopy
upper leaves; stunted
At reproductive
plants with small
stage:
leaves; wilting and
Inereases number of rolling of leaves;
spikelets per panicle early leaf
senescence;
At ripening stage: blackened roots.
Increases grain
filling percentage.
d. Site-specific nutrient management
Site-specific nutrient management (SSNM) is a system that incorporates best
management practices for fertilizer application in rice production. It involves
applying nitrogen (N), phosphorus (P) and potassium (K) fertilizers based on a
fertilizer calculation chart and a leaf color chart. Using this system, farmers can
determine not only when to apply fertilizers, but also how much to apply.
Fertilizer application therefore becomes cost-effective and efficient.
The SSNM is done in three steps:
i. Establish the yield target
The yield target or the estimated grain yield if N, P, К limitations are removed
is influenced by such factors as variety, climate, and crop management
practices. The yield target determines how much N, P, К is needed by the plant
to achieve its yield potential. Farmers can obtain the yield target values either
by field experimentation or by consulting literature specific to the variety that
has been grown under the same climate using similar crop management
practices.
11. Use existing nutrients in the soil
33

The soil naturally contains nutrients from organic matter such as manure and
crop residues and deposits from irrigation water. The nutrient-limited yield is
first estimated by determining the grain yield for a variety when a specific
nutrient (e.g. N) is withheld but other nutrients are added to make sure that
they are not yield limiting.
iii. Deduct the nutrient-limited yield from the yield target to determine
how much N, P, К fertilizers to apply.
Guidelines for the application of N, P, К fertilizers based on the SSNM principle have
been developed by IRRI. They can be downloaded from the following web pages:
1. Nitrogen Management:
http://irri.org/images/stories/SSNM/researcher_attachment/nitrogen%20managem
ent.pdf
2. Phosphorus and Potassium Management:
http://irri.org/images/stories/SSNM/researcher_attachment/phosphorous%20and%
20potassium%20management.pdf
Nitrogen fertilizer is applied two or more times during the growing season to supply
the needs of the rice plants at specific stages of their development. The leaf color
chart (LCC) is the indicator used to determine whether the fertilizer needs to be added
or not. Phosphorus and potassium fertilizers are usually applied from two days before
sowing or transplanting to 14 days after transplanting. All phosphorus needs are
applied at this time, but only half of the potassium required is applied unless soil
levels are low. The other half is applied during the early stages of panicle initiation.
34

e. Leaf color chart
Source: IRRl.org
The nitrogen content of a plant can be easily monitored using a standardized LCC
to check a leafs shade of green. This chart was developed from the collaboration
between IRJU and the Lfniversity of California Cooperative Extension. The chart is
made of a white plastic strip with four panels of different shades of green (from
yellowish to dark). Each shade corresponds to a specific amount of N in the plant.
To determine if the rice plants need supplemental N, first a sample of ten healthy
rice plants or hills are randomly selected. The topmost, fully expanded leaf from
each plant is removed and the middle portion of the leaf is used to locate the panel
color that closely matches that of the leaf. If the leaf color falls between Panels 3
and 4, then supplemental nitrogen is not needed. If the color falls below Panel 3,
then the soil is nitrogen-deficient and must be supplemented. Panel 5 indicates
excess nitrogen. In this case, fertilization should be withheld.
Leaf color readings should always be conducted at a specified time of day, and
they must be done in the shade because direct sunlight affects leaf color reading.
f. Micronutrients important to rice plant growth
Zinc deficiency is common in sodic soils with high pH or when the soil or water
that is used for irrigation contains high amounts of bicarbonate. It is considered as
the most prevalent deficiency of any micronutrient in rice. The symptoms of zinc
deficiency include stunted plants, brovm spots on leaves, basal leaf chlorosis,
stacking of leaf sheaths, slow growth, and reduced tillering. During the
reproductive stage, increased sterility of the spikelets may occur.
To correct zinc deficiency, zinc sulfate can be applied to the field at 5 kg per
hectare 14 days before transplanting. Alternatively, seedlings may be treated with
35

1
zinc sulfate while still in the nursery beds or dipped in a 2 to 4 % zinc oxide
suspension prior to transplanting. If the deficiency is observed after transplanting,
the field should be drained and the soil allowed to dry up. When transplants
exhibit new shoot and root growth, 2.5 kg per hectare of zinc EDTA or 5 to 6 kg
per hectare of zinc complexes should be applied. Ammonium sulfate is then added
at a rate of 50 kg per hectare and shallow flooding of the field is done. Doing this
salvage measure may lengthen the growing season by two to three weeks, but the
rice plants can still attain as much as 90% of their yield potential.
Iron deficiency is characterized by stunted plants with chlorotic or yellowing
leaves. Young leaves exhibit interveinal yellowing. The occurrence of this
deficiency is quite rare but correcting it is a very expensive undertaking; to be
effective, large amounts of inorganic iron sources are needed. Nonetheless, if
found deficient, 30 kg per hectare of FeS04 should be applied close to the rows or
broadcasted (requires a larger amount). A 2 to 3% solution of FeS04 or iron
chelates can be sprayed on the leaves two to three times at two-week intervals
starting at tillering.
Chlorotic young leaves with necrotic tips, whereas older leaves exhibit no necrosis
are the symptoms of sulfur deficiency. When the deficiency occurs during the
vegetative stage, the effect on yield is more pronounced. Sulfur-deficient soils can
be corrected by application of 2.5 to 3 kg of S per hectare per ton of anticipated
yield 14 days before transplanting.
There are other micronutrients that are important to rice. It is best to consult
existing literature when deficiency symptoms do not match the deficiencies
detailed above.
3. Weed management
Weed management should begin during land preparation, three to four weeks before
sowing or transplanting. The land must be kept dry prior to land preparation so that
weed seeds will dry up. Weed seeds that do germinate are allowed to grow, then they
can be incorporated into the soil during plowing or harrowing. This method
effectively reduces weed seed reserves in the soil resulting in lower infestation in the
following growing cycle.

Weed management is very important during the vegetative stage of the rice plant. The
first 30 to 40 days after sowing or transplanting is when competition from weeds is the
highest and great reductions in yield can occur if proper crop and cultural management
practices are not undertaken. To ensure that weed growth is kept to a minimum,
inspect nursery beds and remove weed seedlings that germinated with the rice seeds.
For lowland rice culture, maintain a water depth of about 5 cm after transplanting to
discourage weed seed germination on the field. In both upland and lowland rice
culture, manual or mechanical weeding may be done. If the soil is to be flooded, the
water depth must be kept shallow 7 to 10 days after transplanting to allow the
mechanical weeder to pass through each row crosswise. The weeder pushes the weed
seedlings into the mud, and the shallow water depth is maintained for another two
days to keep the seedlings buried. After two days, the water depth is brought back to
5 cm.
In cases where severe weed infestation has occurred or when problematic (i.e. difficult
to eradicate) weeds are present, either prior to or during the growing cycle, it may be
advisable to use herbicides. However, herbicide use varies from region to region and
from country to country. What is allowed in one country might be banned in another.
Several rice varieties have been bred for herbicide resistance to facilitate the removal
of weeds using herbicides without damaging the rice plant. If weeds are a major issue
in the area to be used for rice production, using herbicide-resistant rice varieties can
help alleviate the problem.
Although weeding is not necessary during the reproductive and ripening stages, the
presence of weedy rice necessitates their removal before they mature and produce
seeds that can infest the field in subsequent growing cycles. Removing weedy rice is
costly if they have infiltrated the rice field, especially because they are genetically
related to rice and resemble its physical characteristics in many ways. They can be
taller, shorter, or of the same height as the rice plant. They can also have the same
growth cycle. During the reproductive stage, they develop panicles and spikelets and
produce grains. The difference is that weedy rice grains fall off easily and cannot be
harvested. The seeds however remain on the ground and may germinate in the next
growing cycle. To prevent the introduction of weedy rice into the field, it is important
to make sure that the rice seeds purchased are pure and do not contain weed seeds.
Machinery that has been used in weedy rice-infested fields must be inspected and
cleaned of residues before being used in the next growing cycle. Irrigation canals and
ditches must be kept weed-free. If infestation is not severe, and weedy rice can be
easily distinguished, cutting off the panicles or removing them by hand before they
flower can be an effective preventive measure. After harvesting an infested field, the
straws can be left on the ground and burned to destroy weedy rice seeds. During the
next land preparation, allowing weedy rice seeds to germinate then incorporating them
into the soil can help break the cycle of infestation.
37

In both upland and lowland rice culture, planting rice in rows rather than broadcasting
them makes it easier to distinguish weedy rice seedlings; they can be easily removed
by hand or with the aid of a mechanical weeder.
Rouging is another method of removing weeds from the rice field. It is the term used
to remove undesirable rice varieties or off-types in a rice field growing true-to-type
hybrid rice varieties. Off-types are rice varieties that are not phenotypically the same
as the true-to-type variety that the farmer wishes to grow. They may be known or
unknown rice varieties. Off-types can appear if the field was planted with it in the
previous growing cycle or if it was introduced from another field. Rouging is
commonly practiced by hybrid seed growers who must ensure that the seeds they
produce come only from the cross between the true parents.
It is advisable obtain information from the local agriculture office with regards to the
most common weeds in the local area and their control measures.
4. Insect management
The health of the rice plant can greatly affect the incidence or absence of insect pests.
Plants that are too robust (e.g. too much N fertilizer) are attractive to insects not just
because of the shade and humidity they provide, but also because they serve as a food
source. Plants that are too weak cannot recover easily from insect damage and could
even die. Insect pests of rice can be categorized based on how they attack the plants.
There are root feeders, stem borers, defoliators, grain suckers, leafhoppers and
planthoppers. Different insect pests attack different growth stages of the rice plant.
For instance, in the vegetative phase, mealybugs, thrips, stem borers, and leaf folders
are common pests. In the reproductive stage, planthoppers and leafhoppers attack rice
plants. During the ripening stage, seed bugs and stink bugs feed on the grains.
There are also regional differences in the proliferation of these pests. It is best to
check with the local agricultural office regarding insect pests that are prevalent in the
area to be used for rice production.
Control of insect pests depends on the success of cultural management practices
including water, fertilizer and weed management; biological control; planting time;
cropping pattern; and planting method.
38

a. Water management
Alternately flooding and draining the riee field is a good practice to discourage
insects that inhabit the soil, viral diseases, and virus vectors.
b. Weed management
Weeds can be either good or bad for rice plants. Many weeds act as alternate hosts
of pests and pathogens, but they also provide shelter to beneficial insects that are
natural enemies of insect pests. The best course of action to take in terms of weed
management is to remove weeds that grow within the rows of plants but allow
weeds to grow near the rice field to serve as habitats for natural enemies of pests.
c. Fertilizer management
As previously mentioned, avoid providing too much nitrogen as this encourages
heavy growth that attract insect pests.
d. Biological control
Although insect infestation might convince farmers to spray pesticides, it is not
advisable because pesticides indiscriminately kill all insects. In the process,
beneficial insects such as natural parasites and predators of the target insect pest
are also eradicated. Furthermore, eradicating one insect pest might leave an
opening for another insect (i.e. secondary pest) to attack the plants. Following
proper cultural management practices is the best course of action to take.
e. Planting time
Planting at the earliest possible time is more desirable than planting later when
insect population is higher.
f. Cropping pattern
It is better to plant the entire rice-growing area at the same time than leave gaps in
the schedule of planting. If rice plants in one field mature earlier than those in
another field, insect pests can relocate to that other field and continue their
damage. The result is higher yield losses over a wider area from insect pests.
5. Disease management
The most damaging diseases attacking rice plants are sheath blight, blast, stem rot,
bacterial panicle blight, grain smuts, the Cercospora complex, seed rot, and water
mold.
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Combating disease attack involves host resistance (disease-resistant varieties), cultural
management practices, and chemical control. As with insect pests, disease prevalence
differs by region. It is better to check with local agricultural authorities regarding
which diseases are prevalent in the area where rice will be grown.
Planting resistant varieties is the first line of defense in crop protection when it comes
to disease management. No single rice variety has resistance to all or most diseases,
but new varieties with improved resistance to many diseases have been bred.
Crop rotation is one method to break the cycle of disease infestation but it is possible
only in upland rice culture: when disease outbreak occurs in one season, it is advisable
to plant a different crop in the next growing cycle to prevent the outbreak from
spreading.
When a disease outbreak occurs, using chemical control is the best way to limit crop
damage. But application of pesticides should be a last resort because, as with insect
pests, fungi and bacteria develop resistance to chemicals used in their control. Early
detection and targeted use of chemicals is the best approach to take in controlling
diseases.
Major diseases in rice plants
The two major diseases in rice are leaf sheath blight and rice blast. Management
practices for both diseases are similar: plant varieties that show at least moderate
resistance, avoid planting late in the season, and do not apply too much nitrogen
fertilizer.
a. Sheath blight
Causal fungi: Rhizoctonia solani
Sheath blight usually attacks the rice plant from the intemode elongation phase
(during the vegetative stage) to the ripening stage. The pathogen is spread through
the field during flooding and the first signs of infection appear on the stems along
the water line. Symptoms appear as brown oval lesions on the stem that can spread
through the entire plant except the roots. High nitrogen rates result in thick stands
and thicker canopies which increase moisture levels in the plant thereby
encouraging the development of the disease. The rice field should be inspected
from intemode elongation to heading stage for signs of blight infestation. To

determine if fungicide application is warranted, check the percentage of tillers that
are infected from a sample number of plants. In susceptible varieties, if the
percentage of infection is 5 to 10%, fungicide should be applied. For moderately
resistant varieties the percentage of infected tillers should be 10 to 15%. The best
time to apply fungicide is during the booting stage (i.e. the panicle is 2 to 4 in
from the flag leaf sheath).
The spores of the causal organism overwinter in infected plant debris that is left on
the field after harvest and can spread through the air to other fields. When the fleld
is flooded again for the next cropping cycle, new infestation begins. Thus, it may
be necessary to spray the field twice to control further spread of the disease.
Sheath blight infestations cause sterility resulting in decreased harvestability and
quality of grains. Additional losses come from the cost of fungicide application
for the current and succeeding crop.
b. Rice blast
Causal organism: Pyricularia oryzae
The blast fungi infect rice plants from the vegetative stage to the harvest stage.
The fungi can infect all parts of the plant except the roots. Infection initially
appears on the leaves as diamond-, football- or spindle-shaped lesions with a lightcolored
center and dark brown edges. Lesions start small but enlarge as infestation
becomes more severe. During heading, lesions appear just below the head or on
individual panicles causing the parts to break off. Infected stems have blackened
nodes that lodge. As with sheath blight, the development of rice blast is favored by
the consequences of high nitrogen rates. Infestation is more severe in upland rice
culture. Sandy soils and fields lined with trees also favor blast development. Rice
blast infestation is considered the most serious disease of rice. Entire fields can be
completely destroyed in a short time. Losses stem from reductions in yield due to
plant deaths and the cost of applying fungicides.
Rice varieties with resistance to rice blast have been developed, but they do not
remain resistant for long because new strains of the fungi develop quickly.
Susceptible varieties should be scouted for signs of blast infection during the
vegetative stages. When blast is detected, preventive spraying is required. In
resistant varieties, fungicide is not applied to infected plants unless they are dying.
41

í
The best time to apply fungicide is at the booting stage (i.e. when the panicle is 2
to 4 in from the flag leaf sheath) and at 50 to 70% heading, the most effective time
being no later than 50 to 70% heading.
The spores of rice blast overwinter in infected plant debris that is left on the field.
They can be carried to other fields by wind and rain. Unlike sheath blight, flooding
prevents blast from infecting rice plants in the next cropping cycle.
6. Other pests
a. Snails
The golden apple snail is a major pest of rice in Southeast Asia. It was first
introduced from South America as a potential source of food for the people,
instead it has become a major nuisance in rice paddies. The snails feed on young
and emerging seedlings and will decimate the entire field if left unchecked.
The first 10 days after transplanting or the first 21 days after direct seeding are
critical for snail management. Beyond this period, rice growth is fast enough to
compensate for any damage.
Besides planting rice varieties that grow vigorously, there are biological, cultural
and chemical means to manage the pest. Ducks introduced into the paddy feed on
the snails and ants feed on the snails’ eggs. Snails can also be handpicked and
their egg masses manually destroyed. They can be lured away from rice seedlings
with leaves that they find attractive. Entry into the field or paddy can be prevented
by covering irrigation inlets and outlets with screens (e.g. bamboo or wire) or
planting plants that are toxic to the snails.
b. Rodents
The major rodent pests of rice are the rice field rat (Rattus argentiventer), the
Black rat (Rattus rattus), and the bandicoot rat {Bandicota bengalensis).
The rice field rat is the most destructive rodent pest particularly in Southeast Asia.
Symptoms of rat damage include seedlings that appear to have been cut or
chopped or are missing from their hills. In older plants, stems and tillers have 45°
cuts or bites. In plants at the ripening stage, buds and ripening grains have been
chewed on or are missing. When any of the symptoms are present, signs of
confirmation include rat footprints on the wet mud and holes or burrows near the
area where the damage was observed.

Rice field rat populations can increase rapidly because they breed quickly and the
female can have as many as 10 to 14 offspring. The breeding period starts at
panicle initiation and ends at ripening. If a nearby rice field is planted two weeks
after the currently infested field, the rats will move on to that field and continue
breeding. If left unchecked, an explosion in the rat population could happen
leading to more severe crop damage. After harvest, when the field is empty and
during land preparation, the rats can be found along runways and water channels
or in gardens.
Eradicating rats from the rice field only temporarily solves the problem because
they can breed in the villages or towns nearby then burrow their way to the field to
infest it again. A community-wide eradication effort must be undertaken to keep
the rat population low.
General control measures that can be used against rats include the following:
a. Locate rat burrows and either flood, fumigate or dig out the rats.
b. Minimize growth of thick vegetation around the rice fields.
c. Install kill traps or live traps around the field.
d. Maintain cleanliness throughout the farm, especially around the grain storage
area (remove garbage that can serve as food source and piles of wood that may
be used as shelter).
e. Use rat poisons wisely and carefully (ensure no other farm animal or children
can access them).
f. Plant rice synchronously (less than two weeks apart) within the farm and if
possible with neighboring farms.
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7. The Economic Threshold
The economic threshold is a concept used by farmers in deciding whether or not to
apply pesticides when a pest incidence is detected in the field. The level of pest attack
is first assessed and based on the estimated cost of treatment, the farmer determines if
the benefits of applying the treatment (yield value after damage) can cover the cost of
that treatment. Methods used to assess the level of pest attack include number of
insect pests per 10 plants, percentage of plants harboring a disease in a given area, or
the number of weeds in a one-square-meter area. Once the level of pest attack has
been determined, then the cost to apply the treatment can be calculated. The farmer
then determines how much can be earned from the reduced yield with and without the
pest treatment. The economic threshold is expressed as a percentage of crop loss using
the following formula:
% crop loss necessary for treatment to be worthwhile = [C/YP(K/100)] x 100%
Where:
C = the cost of treatment,
Y = the expected yield of the crop,
P = the expected price per ton, and
К = the expected effectiveness of the treatment
For pest treatment to be justified, the percentage yield loss without treatment must be
greater than the percentage crop loss necessary for treatment to be worthwhile.
Part 12: Harvest
The best time to harvest rice is when 80 to 85% of the grains have ripened (i.e. they are strawcolored),
with the remaining 15 to 20% in the hard dough stage. Fully ripe grains will have a
moisture content of between 20 and 25%. On average, grains are ready for harvest 30 days
after flowering. Rice varieties differ in the number of days to harvesting from sowing.
Generally, early-maturing varieties take 110 days, average-maturing varieties take from 113
to 125 days, and late-maturing varieties take from 130 to 136 days. The days after heading
44

can also be used to determine harvest time. During the dry season, 28 to 35 days after heading
is the optimum period to harvest; in the wet season, the optimum period is from 32 to 38
days. Harvesting too early will yield chalky grains, whereas harvesting too late will yield
grains that shatter easily.
Rice can be harvested manually or with the use of a thresher or a combine harvester. In either
case, it is important that the harvesting method used can ensure that grain yield is maximized
and that grain damage and quality deterioration are minimized. Yield losses from harvesting
due to improper handling can result from grain shattering, scattering, separation, cracking, or
breakage.
The three basic harvesting processes are cutting, threshing, and cleaning. Other processes
such as hauling, field drying or stacking/piling may or may not be necessary depending on the
method of harvesting. Each of the basic processes can be done separately using hand-held or
mechanized equipment, but they can also be combined using a combine harvester.
1. Cutting
Manual cutting involves separating the tillers from the plant by cutting them 15 to 25
cm from the base when using sickles or just below the panicles when using knives.
Manual cutting is the most common method used by small rice farmers around the
world, but it is labor intensive and time consuming. However, it is an effective
method for harvesting rice plants that have lodged (i.e. not erect).
Rice plants can also be cut mechanically using a reaper mounted in front of a handoperated
tractor. The reaper cuts the tillers and lays them in a windrow that can be
easily picked up later.
2. Threshing
Threshing is the separation of the grains from the rice straw. It is usually done near or
on the field, right after harvest. Threshing can be done manually or with the aid of
specialized machinery.
a. Manual
Manual threshing is accomplished by pounding grain-filled straws against a mat
spread on the ground or by trampling on them using bare feet or an animal. The
straws can also be threshed by beating them against any hard object such as an oil
drum, a slatted bamboo or a wooden frame; the grains fall to the ground and are
collected and piled together using spades or hoes. All these methods are labor
intensive.

The pedal thresher is a hand-operated mechanical equipment comprised of a
threshing drum attached to a frame, a transmission unit, and a foot crank. When
the crank is pedaled, the drum turns and the rice straw can be threshed by hitting
them on the rotating drum. The grains are separated and fall to the ground along
with bits of straw, chaff and other foreign matter. The grains are then separated
from the other materials by flailing, sieving or winnowing. This equipment makes
manual threshing less labor intensive.
Hand threshing of rice is easier if the straw is allowed to dry in the sun for two
days prior to separation. A grain moisture content of 18 to 20% will result in the
highest milling yield. The grains must not be over-dried or rewetted as the former
will lead to shattering and the latter will result in grain fissures that cause breakage
during milling.
b. Machine
Stationary machine threshers that are mounted on tractors or trucks have made
threshing faster and more efficient. There are two types of machine threshers:
hold-on and feed-in. In the hold-on type, only the panicles are placed in the
machine. The threshing capacity is lower than the feed-in type, so the machine is
mainly used for rice straw that have been bundled and stored for later processing.
The threshed grains will need to be cleaned once they are separated. The feed-in
type is larger, has a higher threshing capacity, and can handle both threshing and
cleaning. In many rice-growing areas, such machines are owned by a few
individuals who rent them to farmers. This entails scheduling the harvest to when
the thresher is available for use.
Some rice farmers combine manual cutting and mechanized threshing. This system
lowers labor requirements and increases the volume of rice straws that can be
processed.
3. Cleaning
Grain cleaning is the separation of all unwanted matter from the rice grains. After
threshing, grains can become contaminated with bits of rice straw, weed seeds, chaff,
soil, garbage, and other inert materials. Removing all contaminants will result in
grains with higher value. Cleaning grains also removes diseases and insect pests that
could re-infect the field. Furthermore, cleaning improves drying, grain storability, and
reduces contaminants during milling. When clean grains are milled, the output and
46

quality of the milled rice are greatly improved. Cleaning can be done manually or
mechanically.
a. Winnowing
In winnowing, the grains are placed on a winnowing tray which is then manually
shifted in a to-and-fro or up-and-down movement against a blower, air fan or the
wind. This method of cleaning will remove lighter materials such as bits of straw,
weed seeds, chaff, and unfilled grains. However, heavier materials such as dirt,
stones, off-types, and other weed seeds remain with the grain. This type of
cleaning is both labor intensive and time consuming.
A hand-operated wirmower can hasten the cleaning process and handle a greater
volume of grains. The grains are placed on a tray at the top of the winnower, then
it is shifted down an inclined air duct using a hand-cranked wheel. A blower at the
bottom of the tray blows away the lighter material as the grains fall down the air
duct to a catchment tray at the bottom of the setup.
b. Screening/sifting
This machine has several layers of sieves of different sizes. The threshed grains
are placed at the topmost layer and the machine shakes to sift the grains through
each layer of sieve until only the rice grains are left. This method of cleaning can
handle large volumes of grains in a relatively short period of time compared with
manual or hand-operated cleaning.
c. Seed cleaner
This machine is a combination winnower and sifter. A fan removes lighter
impurities in the harvested grains, then a sifter removes the heavier impurities.
Cleaned seeds should be inspected prior to storage. Consider removing those that have
malformations or discolorations, those that have germinated, or those that are broken
or moldy. Such seeds can greatly impact the quality of the seed, its viability and vigor.
47

г
I*

Section 3: Overview of Important Rice Production Technologies
Part 13: Production technologies from the 1960s to the early 1990s (Green Revolution)
The Green Revolution created high-yielding varieties (HYVs) that significantly increased rice
yields and prevented famine in many rice-growing countries. However, HYVs required high
inputs of inorganic fertilizers, pesticides, and herbicides. While yields did increase, so too did
pest outbreaks and the indiscriminate use of pesticides and herbicides. Such use led to
increased pest resistance; the emergence of secondary pests; pollution of the air water, and
soil; the deterioration of the health of farmers; and the loss of habitat and biodiversity.
The realization of the serious environmental effects brought on by the Green Revolution led
to the development of various production systems that focused on more sustainable and
environmentally sound practices.
Part 14: Integrated Pest Management System
The Integrated Pest Management (IPM) system had its beginnings at the University of
California in the USA a few years after the end of World War II. There, entomologists
preached the “supervised control of insects” using “parasites and predators”. Supervised later
became “integrated” to mean the combination of chemical and biological control measures.
This system of insect pest management has been adapted by the FAO, which defines IPM as:
“.. .the careful consideration of all available pest control techniques and subsequent
integration of appropriate measures that discourage the development of pest populations and
keep pesticides and other interventions to levels that are economically justified and reduce or
minimize risks to human health and the environment. IPM emphasizes the growth of a
healthy crop with the least possible disruption to agro-ecosystems and encourages natural pest
control mechanisms.”
The IPM is a step-by-step process that rice farmers can follow before, during, and after the
growing cycle of their crop.
1. Prevention and suppression
The best way to discourage pests is to create an environment where they cannot
49

establish themselves. Some common-sense practices include the following:
a. Practice crop rotation or inter-cropping.
Crop rotation is planting another crop after one cropping cycle of rice. This
breaks the life cycle of rice pests. Intercropping is planting a different crop
beside or near rice fields. Intercrops have several functions: they serve as
alternate hosts for rice pests and/or hosts for their predators; they break the
monotony of rice thereby preventing the spread of pests to other rice fields;
and they are a supplementary source of income to the rice farmer.
b. Use resistant or tolerant rice varieties from certified seeds.
c. Use cultivation methods that promote healthy growth of rice seeds or seedlings
such as sowing at the earliest possible time, sanitizing the nursery beds prior to
seeding, proper spacing of seedlings during transplanting, land preparation
practices that follow good water management principles, and the incorporation
of organic matter to improve soil fertility.
d. Observe proper sanitation and hygienic practices in an around the rice field
such as removal of garbage, dead and infected plants or plant parts, and
maintaining clean machinery and equipment.
e. Protect and enhance beneficial organisms by providing ecological habitats for
them in and around the rice field.
f Follow proper fertilizer management, especially for nitrogen application.
g. Synchronous planting of rice fields.
2. Detection and monitoring
When pests are detected in the field, they should be carefully monitored. Monitoring
may include using warning systems and early diagnostic tools to determine their levels
or population and forecasting their threat to the crop.
2. Non-chemical control
If the results of the monitoring reveal a low threat level, no pest control is done. If the
threat level is above the economic threshold, then biological, physical and
50

nonchemical control methods should first be employed before resorting to the use of
pesticides.
a. Biological control
There are hundreds of natural enemies of insect pests of rice, particularly in the
tropics. It is best to check with the local agricultural office regarding which
natural enemies are present in the area to be planted with rice and whether
introduction of a natural enemy is advisable.
Examples of natural enemies of insect pests of rice:
Insect pest Natural enemies Nature of attack
stem borers Meadow grasshoppers egg predator
Tetrastichus schoenobii Ferriere
Cotesia flavipes Cameron
Lady beetles
Wolf spiders and water bugs
egg parasitoid
larval and pupal parasitoid
larval and pupal predator
adult predators
Beauveria bassiana (Balsamo)
Vuillemin
adult fungal pathogen
leafhoppers and Oligosita yasiunatsui Viggiani et egg parasitoid
planthoppers Subba Rao
leaffolders
Green mired bug
Pseiidogonatopus spp.
Wolf spiders and water bugs
Metarhizium anisopliae
Copidosomopsis
nacoleiae (Eady)
Crickets {Amixipha longipeimis)
Gonioziis nr. tr angui {far Kieffer
Ground beetles
Bacillus thuringiensis Berliner
egg predator
nymph and adult parasitoid
nymph and adult predators
adult fungal pathogen
egg parasitoid
egg predator
larval and pupal
parasitoids
larval predator
larvae fungal pathogen
51

. Mechanical control
Use traps to catch rodents, erect barriers around the field to deter fiarther
attack, and hand pick pests whenever possible.
4. Pesticide use
When nonchemical methods fail to control the pests, pesticides should be applied.
However, application should be at the lowest dose possible and it should specifically
target the pest in question. Furthermore, pesticides should have minimal side effects
on humans and other organisms. It should also have a limited effect on the
environment.
Pesticide application should be limited to the area where the pests are detected.
Broadcast spraying of pesticides should be done as a last resort.
5. Monitoring the success o f pesticide application
After applying pesticides, the pest population should be monitored. The goal is not
complete eradication, which is usually not possible, but a reduction in the number to
manageable levels.
Limitations o f IPM
Although IPM provides a lot of benefits from the reduced number of pesticide applications,
there are limitations in its application as well.
1. Knowledge of pests and pesticides required
IPM requires that the farmer has extensive knowledge of rice pests and the specific
pesticides used for their control. This may be easy for experienced rice farmers but not
for those who are new to growing rice. Poor rice farmers also may not have access to
current control information.
52

2. Can be labor intensive and time consuming in terms of manual removal of pests and
targeted applieation of pesticides.
3. Interpretation of crop monitoring results can be challenging.
4. No price benefits for IPM-produced crops
Unlike organically grown produce which are priced higher, crops produced using IPM
are priced the same as conventionally grown crops. This can be a downside because
1PM crops will have some amount of damage or blemish that may reduce its market
value.
5. Yield inereases plateau after several growing seasons.
Part 15: System of Rice Intensifícation
The System of Riee Intensification (SRI) was developed in 1983 in Madagasear by Fr. Henri
de Laulanié, a Jesuit priest who arrived there in 1961. Father de Laulanié worked to improve
the produetivity of rice farms without the aid of external inputs that they could not afford. In
Madagascar, rice was being grown in limited irrigated lowland areas with low yields that
were unsustainable. With the help of the Cornell International Institute for Food, Agriculture
and Development (CIIFAD), SRI principles were promoted to marginalized farmers. By
practicing SRI, farmers were able to increase their yields by more than four times compared
with the traditional methods.
The CIIFAD defines SRI as a system “based upon a set of principles and practiees for
increasing the productivity of irrigated rice by changing the management of plants, soil, water
and nutrients.”
Practicing SRI is said to reduce water usage by 25 to 50%, reduce seed requirements by 80 to
90%, reduce cost of production by 10 to 25%, and raise net income per hectare by 50 to
100%.
The CIIFAD further explains that SRI is not a teehnology but a methodology that is
continually evolving and that can be adapted by the farmer to suit the particular environment
in which rice is grown. It was developed with the enhancement of the livelihoods of very poor
farmers in mind.
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1. Claims o f SRI:
a. Results in higher yields;
b. Less water and fewer seeds required;
c. Use of chemical fertilizers and pesticides (external inputs) are not needed; and
d. Purchase of new seeds is not needed.
2. The key elements of SRI:
a. Seedlings are germinated at a lower seeding rate than normal in nursery beds that
are kept moist but not flooded;
b. Transplant seedlings at 8 to 12 days, younger than normal, when they are at the
two-leaf stage;
c. Seedlings are planted one per hill instead of the recommended 3 to 4 seedlings per
hill;
d. Seedlings are spaced farther apart than usual (e.g. 25 cm x 25 cm or wider) and in
a square pattern to facilitate easy weeding;
e. Seedlings are transplanted quickly, carefully, and shallowly (1 to 2 cm deep) to
limit transplant shock especially to the roots. Seedlings are lifted off from the
nursery bed using a trowel to minimize damage to the roots.
f. The soil is kept moist but not saturated. Alternatively, water can be supplied
intermittently to create soil conditions that are alternately wet and dry; this
principle is similar to the AWD type of irrigation covered earlier. This latter
practice is less labor-intensive than keeping the soil moist at all times.
g. A rotary weeder (rotating hoe or conoweeder) removes weeds mechanically while
at the same time improving soil aeration; weeding is done 10 to 12 days after
transplanting and every 10 days thereafter until the rice plant is large enough;
h. Organic fertilizers (e.g. compost) are added to the soil in greater amounts than
normal to improve soil fertility.
54

3. Principles behind the System:
a. Transplanting seedlings at a younger age:
Younger seedlings have greater potential for profuse growth of roots and tillers,
particularly before 15 days after sowing. In temperate regions, however, seedling
growth is slower. So planting 15 to 25-day old seedlings is the equivalent of
planting 8 to 12-day old seedlings in tropical regions.
b. Promote the growth of root systems:
Planting just one seedling far apart from each other encourages deeper and wider
root growth as well as encouraging greater tiller production per plant because of
less competition for space and nutrients. More tillers result in more panicles and
more grains per plant. Better root systems also result in better resistance to
drought and lodging because they are better able to tolerate heavy rain, windy
conditions and damage from storms. Furthermore, planting singly prevents mutual
shading within the hill, thereby maximizing the photosynthetic ability of the
leaves.
c. Increase the abundance and diversity of soil organisms:
Keeping the soil flooded creates anaerobic conditions that are believed to hinder
root growth and the activity of aerobic soil organisms which improve soil fertility.
d. Limited to zero external or chemical inputs:
The System was initially developed with the addition of inorganic fertilizers to the
soil. Eventually, the use of compost was recommended to enhance soil microbial
activity.
4. Cultural practices that complement SRI
The System encompasses the time frame from transplanting to harvesting. Practices
before and after that are pretty much in line with management practices that have been
established for rice growing such as those for land preparation, varietal selection, seed
selection, seed priming (or pre-germination), and nursery bed preparation.
The SRI has not been adopted as a recommended methodology for rice production by
international organizations such as the FAO and IRRI, which could provide funding or project
support for farmers. The biggest constraint has been the lack of peer-reviewed research about
its claims of yield improvement, particularly because some of the reported yields exceeded
55

the genetic yield potential of the high yielding varieties planted. Other claims such as shorter
crop cycle, better grain quality, and higher milling yield for SRJ-grown rice have all come
from reports from the field that may not have been based on scientific observations. However,
a recent joint agreement has been made between Cornell University, IRRI, and Wageningen
University in the Netherlands to compare SRI methodologies with best management practices
for growing rice.
The ClIFAD has been instrumental in spreading SRI to government agencies of various ricegrowing
countries such as China, India, and the Southeast Asian countries. The ClIFAD does
not promote SRI as a technology that must be strictly followed to be successful. Instead, SRI
is promoted as a set of practices that farmers “can adapt to suit local conditions and cropping
systems.” The System is now practiced in more than 30 countries around the world. While its
main focus has been helping poor farmers with small rice growing areas, SRI can be adapted
to middle and large farms if issues of careful manual transplanting, weeding and water control
over a larger area can be overcome.
5. Limitations of SRI:
a. Needs stable supply of water.
The System uses an alternate wet and dry type of irrigation for rice, so it cannot be
practiced if the water supply is not stable such as in rainfed lowland rice culture
because these areas are subject to periods of drought.
b. Labor intensive
The System can be labor intensive when it comes to transplanting, watering, and
weeding. This is particularly true in the initial stages of adoption when farmers are
just learning the methodology.
c. Pest occurrence
Pests that would otherwise not be present in conventional rice growing methods
appear in SRI practice. Such pests include root nematodes, weeds, and snails that
take advantage of the unflooded conditions to feed on or compete with the planted
seedlings.
d. Availability of compost material
In SRI, the soil needs great amounts of compost to augment the requirements of
rice plants. Obtaining such compost would require labor, which may not always be
available.
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Part 16: Ricecheck System
The Ricecheck system was developed in Australia in 1986 by the New South Wales
Department of Primary Industries (NSW DPI) in response to concerns that rice varieties were
not reaching their yield potentials, resulting in a yield gap. By using benchmarks based on the
highest yielding crops to identify production limitations and following best management
practices to correct such limitations, this system has been able to overcome the yield gap. The
key to Ricecheck’s success has been the creation of farmer groups that provided feedback to
researchers and extension workers and hastened the transfer of current rice production
technologies. This participatory framework has allowed the Ricecheck system to achieve its
goals to improve yield, grain quality and profitability. It is best applied to irrigated and
rainfed lowland rice culture.
According to the NSW Department of Primary Industries, “Ricecheck encourages you to
manage your rice crop by comparing your practices with the practices producing the highest
yielding crops...It helps you to learn from your experiences to improve your crop management
in the future.”
Ricecheck is being adopted and promoted as a holistic approach to rice production in several
developing countries in Southeast Asia, Latin America and Africa with the help of the FAO
and its member countries.
1. How to Use Ricecheck
a. Use the key checks to manage the rice crop.
b. Observing, measuring, and recording the growth of the crop is essential.
c. Compare and interpret results to identify problem areas. Ask the question: Was the
grain quality target achieved?
d. Identify practices that achieved key checks and management practices that may
have limited the yield and can be improved.
e. Determine the best practices by comparing current practices with those that
resulted in the highest yielding crops. Determine which practices need to be
changed.
f Implement improved management practices in the following growing cycle. It is
important to leam from experiences.
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2. Befare planting:
a. Establish target yields (depends on variety, growing region, climate).
b. Set water productivity targets (ton/million liter).
c. Plan the entire operation from start to finish.
These recommendations are provided yearly by NSW DPI to every rice farmer in New South
Wales, the primary rice-growing region in Australia. The recommendations are based on data
provided by participating farmers which the Department analyzes to find the practices that
result in the highest yield and productivity. Rice farmers are free to join the program but not
every farmer has to do so. Participating means that farmers have to provide data about their
rice production to the Department and engage in farmers’ group meetings. For instance, the
recommendation that water level be at a depth of 20 to 25 cm at microspore stage was arrived
at by comparing the different water levels that participating farmers used and finding that this
water level resulted in the highest yield.
The Ricecheck Recommendations:
1. Land suitability
Key Check: A suitable land for growing rice must be one that has low permeability.
This prevents unnecessary water loss through percolation and seepage. By minimizing
access to water sources (irrigation canals or groundwater), considerable water
conservation is achieved. The recommended total water usage is below 14 to 16
million liters per growing cycle.
2. Field layout
Key Check: A rice field with a good layout is flat and even. The bunds must be wellconstructed
(no seepage or leakage) and be at least 40 cm in height at its lowest point.
Water channels should be constructed to facilitate efficient supply, drainage, and
recycling.
2. Sowing time
Key Check: Sowing should be done during the recommended sowing window for
each rice variety when environmental conditions such as temperature favor seed
germination and seedling survival.
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4. Crop establishment
Key Check: The recommended density for planting is 200 to 300 plants/m^. This can
be achieved with 125 to 150 kg/ha of seeds for aerial sowing or 135 to 170 kg/ha for
drill sowing. Plant density below 150 plants/m^ and above 300 plants/m^ reduces yield
potential. The field should be flooded with 3 to 5 cm of water 7 days prior to sowing.
5. Crop protection
Seedlings are susceptible to weed competition especially if they are directly seeded. It
is important to have good knowledge of what weed species are common in the area
(using data from other farmers or from previous seasons) to be able to apply the
appropriate control measure when necessary. Regular inspection of the rice field
particularly in the initial stages of growth is important. This also applies to insect
pests and diseases.
Key Check: Following IPM principles, the application of pesticides and herbicides
should only be done to prevent economic yield loss.
Key Check: Paddy water that has been sprayed should not be drained into public
drainage systems within 21 to 28 days (or as recommended by local irrigation
authorities) after the application of pesticides.
6. Crop nutrition
Following best management practices for fertilization in rice plants, split application
of nitrogen is recommended. Phosphorus is also added to the soil prior to sowing.
Key Check: Pre-permanent water nitrogen
Nitrogen is applied to the soil prior to flooding and sowing. The amount of nitrogen
applied is based on variety, soil type, previous nitrogen applications, and the nitrogen
from organic manure (e.g. legumes) incorporated into the soil during land preparation.
The nitrogen should be sufficient enough so that at panicle initiation, the rice plants
can absorb the nutrient in the recommended uptake range.
Key Check: PI nitrogen
Nitrogen is applied again at panicle initiation (PI) in preparation for grain
development and filling. The amount applied is considerably less than the first
application, generally it should not exceed 60 kg/ha. It is determined using fresh
weight, NIR analysis, and cold risk. Nitrogen uptake is usually higher at high
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temperatures.
Key Check: Phosphorus
Phosphorus fertilizer is added by drilling and incorporating into the soil before sowing
the rice seeds. If soil analysis determines that the soil phosphorus level is below 20
mg/kg, 10 to 25 kg P/ha is applied.
Key Check: Soil characteristics, crop vigor and growth variability, and land that need
fertilizer and organic matter supplementation can be identified using maps (cut/fill
area maps, electromagnetic maps, and aerial image maps).
7. Panicle initiation date
Key Check: Achieve PI before January 10.
In Australia, summer is from December to February, the ideal time for planting rice.
Rice plants that reach panicle initiation before January 10 are at a lower risk of
temperatures being low at the microspore and flowering stages. Therefore, it is
important that sowing be done at the appropriate time.
8. Water management
Key Check: Increasing the water depth to 20 to 25 cm during the microspore stage
has been shown to increase grain yield and improve grain quality.
The recommended water depths at each growth stage of rice are as follows:
a. Establishment/sowing: 3 to 5 cm
b. Mid-tillering (3 shoots per plant): 5 cm
c. Late tillering: 5 to 10 cm
d. Panicle initiation: 10 to 15 cm
e. Microspore stage: 20 to 25 cm
f. Flowering: >5 cm
g. Lock-up (Ripening): as required
h. Late dough stage: drain quickly, within 1 to 2 days
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“Mid-season dry down” is the practice of draining the paddies when rice plants are at
the late tillering stage. The dry conditions should be kept for 5 to 8 days. Doing so has
been shown to increase yields, especially when the soil is of the poorly structured
sodic type.
The practice of delayed permanent water (DPW) involves flooding a paddy when rice
plants are at the later growth stage of about two weeks before panicle initiation instead
of the usual flooding at the 3-leaf stage of growth. This practice results in considerable
water savings (15-20%) but presents problems of weed management, nitrogen
application, and delayed crop development. Whereas new methods in weed control
can eliminate the weed problem, the timing of nitrogen application presents greater
risks because it directly affects yield. It is therefore recommended that sowing be done
7 to 10 days earlier than normal if DPW is to be practiced.
9. Grain quality
Key Check: Grains that are harvested when the moisture content is between 20 and
22% have the best grain quality that results in a higher percentage of whole kernels.
Factors that can affect grain moisture content include weather, sowing date, and
draining methods. Temperatures at the time of harvest should be carefully monitored.
Quality assurance
Key Check: Harvest operations should ensure that no contaminants such as weed
seeds, off-types, insects, and inorganic materials are mixed with the paddy rice.
Milling operations should yield grains that are whole, clean, not discolored, free of
contaminants, and with no unusual flavors.
Limitations o f the Ricecheck System
1. Requires farmer participation:
The Ricecheck System requires the participation of farmers to share the necessary data
and know-how with extension workers and researchers. As in the case in Australia,
not all rice farmers are willing to be part of the system because it requires
considerable investment in time (e.g. measurements and record keeping) and other
resources.

2. Requires data-gathering skills:
Many farmers, especially in poor countries, may not have the necessary data gathering
skills or research know-how to ensure accurate information is provided to the lead
agronomist.
3. Advanced technology input:
Ricecheck requires the use of equipment and technologies that poor farmers cannot
afford such as obtaining aerial and EM maps.
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Section 4: Post-harvest Processing
Rice terminology
Paddy or rough rice is the term used for rice grains that have just been harvested and still have
their husks (hull) intact. Brown rice is the term used for rice grains whose husks have been
removed but which still have the bran layer intact. The bran layer is rich in in dietary fiber,
vitamins, and minerals, but it also has a high fat content. This means brown rice, although
more nutritious, has a shorter shelf life than rice in which the bran layer has been removed.
Removing the bran layer reveals the white endosperm, which is called white or milled rice.
Consumers have a preference for white rice, even though it is low in nutrients. In countries
such as the United States, white rice is coated with vitamins and minerals to make it more
nutritious. But in many poor countries where rice is eaten as a staple food, nutrient
supplementation of rice is not a wide practice, so rice producers are encouraged by the
governments to leave a bit of the bran layer during milling.
Part 17: Drying
Drying is the most critical post-harvest operation in rice production. It is the process
of reducing the moisture content in rough rice to a level that is safe for storage. Drying
removes moisture that can encourage the growth of molds, cause discoloration, and
decrease the grain quality. Harvested grains should be dried within 24 hours. There
are many methods of drying and there is not one specific method that is recommended
for all drying operations in rice. There are drying methods for small-scale and largescale
operations. It is helpful to obtain a moisture meter to detect the moisture content
of the grains as they dry. The moisture content determines how long grains can be
safely stored.
Length of storage
Required
Moisture
Content
Possible problems
2 weeks to a few months 14 to 18% molds, discoloration, respiration loss,
insect damage
8 to 12 months 13% loss of germination
>1 year 9% loss of germination
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1. Sun drying
This drying method is most common in Asia because it is much cheaper than
mechanical drying. In sun drying, the grains are spread in a thin layer (2 to 4 cm) over
a cemented or paved area that is well-aerated or windy. The grains are mixed every 1
to 2 hours. Temperature and moisture readings of the grains are taken frequently using
a thermometer and moisture meter. The grains should be protected from very high
temperatures (> 50°C) and collected or covered if it rains and at nighttime.
Grains can be bagged and stored once the moisture content goes dovm to 18%. If
longer storage is desired, the grains can be further dried using another method.
Sun drying is labor intensive and limited in capacity. It is weather-dependent and
controlling the temperature is difficult. Thus, it may take several days to get the
desired moisture content and during that time, grain losses and damage are likely to
have occurred. The quality of milled rice from sun-dried grains is generally low.
2. Heated air drying
In heated air drying, burners and fans blow warm air (40^5°C) through grains that are
either stirred manually or mechanically for even drying. The flat-bed dryer is common
in Asia and have capacities of from one to ten tons depending on its size. Small dryers
can process one to three tons of grains in six to 12 hours. In developed countries,
recirculating batch dryers have long been in use not just for rice but for other types of
grains too (e.g. wheat and barley). They are vertical-type dryers and can handle loads
of up to 20 tons. Continuous flow dryers are used by large milling companies. It has
separate sections for drying, tempering and conveying. Continuous supply of grains
for drying is necessary to justify their operation at an economically viable level.
3. In-store drying
This type of drying is widely used in Korea and, recently, in Thailand. Ambient air is
blown through the grain bulk at low velocities via air ducts in the storage bin or
compartment. This method is slow but gentle, thereby ensuring that grain quality is
maintained. Depending on the moisture content, the process can take several days to
weeks to bring down the moisture level to the desired percentage. This method is best
used in tandem with other drying methods to hasten the drying process.
To dry the gain in the shortest time that will not damage its quality, a two-stage drying

process can be done. Harvested grain has a moisture content of between 20 and 25%. In
the first stage of the two-stage drying process, the moisture content is first brought down
to 18%. This can be accomplished at high temperatures of from 50 to 60°C. When the
18% moisture content is reached, the grains are cooled down or tempered for about four
hours. Then they can be dried again at a lower temperature of 42°C to the desired
moisture content (e.g. 14%). In recirculating batch dryers and continuous flow dryers,
heating and tempering are done in the same system.
Part 18: Paddy Storage
Paddy storage refers to the storing of rough rice which has achieved the desired moisture
content.
1. Sack storage
In Asia, dried rough rice is usually stored in sacks made of woven plastic or jute at 40
or 80 kg weights. The sacks are then kept in a storage facility where they are placed on
racks and stacked on top of each other.
2. Bulk storage
Some farmers store their rough rice in bulk in small wooden granaries on the farm or
near their houses. Others use containers such as woven baskets or those made of
concrete, wood, or metal, which are then stored inside or under their houses. In
developed countries or large commercial operations, rough rice is usually stored in
bulk in metal or concrete silos which have capacities of from 20 to 2000 tons. The
advantage of storing rough rice in silos is that grain wastage is minimized and the
structure can be easily fumigated if there is an infestation. However, silos are not
popular in tropical countries because hotspots, which encourage mold growth, can
develop inside.
3. Hermetic storage
In this type of storage, rough rice is poured into airtight containers such as those made
of different types of plastic (e.g. PVC and polyethylene). When storing rough rice in
sacks, they can first be placed inside thick polyethylene bags. The bags are tightly
sealed then placed in the sack. The airtight condition in hermetic storage helps the
grains retain their moisture content, thereby maintaining or even improving the quality
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’Г
of the milled rice. If any biological organisms get trapped inside, their respiratory
activities will soon deplete the oxygen supply and they will suffocate and die.
Rough rice stored hermetically can retain their favorable qualities over longer periods
(e.g. more than 8 months) even if their moisture content would normally allow only a
few short months.
4. Storage problems
a. Pests and microbial growth
The most common storage insect pests of rice are the rice weevil, grain moth and
grain borer. The adult rice weevil is responsible for grain damage, whereas the
larvae of the moth and borer are the grain eaters.
Two species oí Aspergillus and Pénicillium are the main storage fungi that cause
damage to rice grains. They are present everywhere, but if their spores are packed
with the grains and the temperature and moisture levels are high (>65%), they can
multiply quickly. Fungal infections result in grains with that germinate poorly,
have low vigor and grain quality. Besides these problems, fungi also produce
poisonous mycotoxins. Temperature and moisture control is very important in
preventing fungal development.
Under storage conditions, the most important rodent pests are the black rat, the
common rat, and the house mouse. Rodents not only feed on the grains, they also
damage materials and equipment used in rice production and can transmit diseases
such as typhoid and scabies to humans.
The best way to prevent storage pests from attacking the grains is to maintain good
storage hygiene by clearing the area in and around the storage facility of garbage
and other materials that may provide shelter or breeding areas for pests. Make sure
that the facility is properly sealed with no entry and exit points for insects and
rodents. Maintain ambient temperatures and low relative humidity inside the
facility. Regularly inspect the grains (or their containers) for signs of infestation
such as holes in the sacks, partially eaten grains, and droppings.
b. Moisture migration
Grains stored in metal bins such as silos are susceptible to moisture migration
especially in regions with seasonal variations in air temperature. In temperate
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countries, for instance, during late autumn or the early part of winter, the
temperature of the rough rice inside the metal bins tends to be warmer than the
outside air. This causes warm air from the rice in the middle to rise or move
towards the sides. When the warm air comes in contact with the cold rice closest
to the walls of the bin, the relative humidity there increases, causing the grains to
gain moisture. In some cases, condensation can even develop.
To prevent moisture migration, air from the outside should be forced through the
grains to reduce the difference in temperature between the grains inside and the
outside air. To be effective, the temperature difference should be within 12°C.
Part 19: Milling
A grain of rice has three basic parts; the husk (20%), the bran (10%) and the endosperm
(70%). Milling removes the husk layer (hulling) then the bran layer (polishing) to reveal the
endosperm or white rice. The quality of the milled rice depends on the quality of the rough
rice, the milling process used, and the ability of the miller to operate the equipment.
Obtaining whole rice kernels (head rice) at a high percentage is the mark of good milling.
This is referred to as head rice milling yield. Milled rice with a high percentage of broken
kernels will fetch a lower price than milled rice with a high percentage of head rice.
White rice has a longer shelf life than brown rice. So a good milling operation should be able
to remove as much of the bran layer as possible. Milling degree refers to the amount of bran
layer that is left on the grain after milling: the higher the degree, the whiter the grain is.
Rice milling can be accomplished using traditional or mechanical methods, and it can be a
one-step, two-step or multistep process.
1. One-step milling
a. Mortar and pestle
This is one type of traditional milling that is still practiced by small farmers
around the world. The rough rice is placed in a large mortar then repeatedly
pounded using a pestle in an upward-downward motion. Friction between the
grains causes the endosperm to break free of the husk and bran. The hard
pounding however results in a great number of broken kernels. This method is
commonly used to obtain white rice for home use because the quality of the rice is
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not commercially viable,
b. Single pass mill
Tliis type of mill is similar to a coffee huiler. It is made of steel and uses very high
pressure for hulling and polishing grains. The process however leads to a high
percentage of broken kernels, resulting in only a 30% recovery rate of head rice.
The single pass mill is still used by many small farmers, but its commercial use is
not licensed because of the poor recovery rate.
2. Two-step milling
In two-step milling, hulling is done separate from polishing by the same machine.
Compact mills are the widely used equipment for this process. The husk is first
removed by rubber rollers, then the bran layer is removed using a steel friction
whitener. The compact mill has a greater than 60% recovery rate for head rice. It can
process from 0.5 to 1.0 ton of grains per hour, and it is widely used for small-scale
commercial operations.
3. Multi-pass milling
This type of milling is used by large commercial mills. Multi-pass mills can handle
several different operations using a set-up of intercoimected machines. The processes
include cleaning, hulling, polishing, separating broken white rice kernels, bagging,
and handling the by-products (husks, bran, impurities, broken kernels). Depending on
the size of the machines used, multi-pass rice mills can process several tons of rough
rice per hour with a 50 to 60% recovery of head rice, 5 to 10% large broken kernels
and 10 to 15% small broken kernels.
Parboiling
In many parts of Asia and Africa, parboiling rough rice is a common practice. Parboiling is
done in three steps:
1. Soaking rough rice in water to raise the moisture content to about 30%;
2. Steaming the wet rice;
3. Drying the rice back down to a moisture level that is safe for milling (e.g. 18%).
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Parboiling causes physical and chemical changes that modify the appearance of rice
especially after cooking. Parboiling affects the milling process in that hulling becomes easier
and there are fewer broken kernels resulting in higher head rice milling yield. Parboiled white
rice is also less prone to insect attack during storage and keeps longer once cooked. However,
removal of the bran layer or polishing is more difficult. Parboiling also presents additional
costs in rice processing. Uncooked parboiled rice cannot be stored for long because it
becomes rancid easily. It also takes longer to cook, thus consuming more energy. However,
there is considerable consumer demand for parboiled rice.
Part 20: Milled Rice Storage
After milling, rice is bagged and either transported directly to the market or stored to be sold
later. In Asia, rice is usually bagged in 50-kilo sacks. In the US, rice is bagged in pounds.
Milled rice is rarely stored for long periods because the quality of the taste is the best soon
after milling. In some countries like the US, rough rice is the preferred stage for storage.
Milled rice is immediately sold to local and export markets. In Thailand, most rough rice is
immediately milled after harvest then sold to local and export markets. In Japan, hulling is
done near the harvest site, and the brown rice is the preferred stage for storage. Milled rice is
produces closer to the selling date.
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70

Section 5: The Future of Rice
The world’s population currently stands at 7 billion. Of this number, more than 50% rely on
rice as their major food source. The United Nations predicts that by 2050 world population
will grow to 8.9 billion people. Most of this growth is expected to occur in less developed
countries. In fact, 58% of the 2050 projection will be living in Asia where 90% of the world’s
rice is currently grown. To feed this expected increase in the number of people, the FAO
estimates that rice production has to increase to 800 million tons annually by 2025 from the
current 600 million tons. But the average growth yield for rice is not on pace to meet this
target. For instance, in South and Southeast Asia, the increase in rise yield fell by 1.4% from
1990 to 2005. In the major rice-producing areas, growth has been minimal in the last five
years. Consequently, rice prices in the international market have doubled since the beginning
o f2008.
There are several reasons for the minimal increase in rice yield: a rapid increase in the
population, the conversion of farm land for urban development, and the unsustainable rice
production practices over decades that have resulted in unusable land for rice growing.
Part 21: Environmental Concerns in Rice Production
1. Methane emission
Rice production is a major contributor to global methane gas emissions. Methane is
one of the greenhouse gases that are believed to cause climate change or global
warming. Rice cultivation accounted for 10% of global methane emissions in 2010.
The waterlogged conditions necessary for rice growing creates anaerobic soil
conditions that favor methane-producing bacteria, which convert carbon from the
organic environment to methane gas. Most of the world’s rice is grown under lowland
conditions that favor methane production. If rice production needs to increase to meet
the demands of a growing population, consideration must be given to the problem of
methane gas emission.
Methane gas emission in rice is believed to be tied to the plant’s ability to utilize
carbon that is available in the soil. During the ripening stage, for instance, rice plants
that have more flowers utilize more carbon in the production of grains, thereby
limiting the carbon supply in the soil for methane-producing bacteria. Timing of
planting is also a big factor. Methane production is higher in the wet season when
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production is typically lower than in the dry season when rice production is higher.
Another factor is the number of growing cycles in one year. Rice can be grown as
often as three times a year (three growing cycles), but doing so means that rice paddies
remain waterlogged for longer periods resulting in more methane gas production.
Draining rice paddies even just once in the growing season has been shown to
significantly cut methane production.
Developing and planting rice varieties that can better utilize carbon sources and
limiting the amount of time that rice paddies are flooded to only during the production
phase (purposely removing standing water outside of the growing cycle) are some
measures that can reduce methane gas emission.
2. Monoculture
Rice monoculture is the planting of rice on the same field for many growing cycles
without breaking to plant a different crop. It can also refer to the planting of an entire
area with only rice, instead of diversifying by planting other crops in the same
vicinity. Farmers practice rice monoculture to maximize the economic benefits of
planting one crop that yields higher prices. This intensive farming method however
has many downsides. The incidence of pests and diseases increases with each new
cycle because the food source is always present. Consequently, the need to use
pesticides to control them increases with each cycle. The continued application of
inorganic fertilizers leads to contamination of the water and adds to the cost of
production. The quality of the soil decreases with each new cycle because of the
constant plowing and harrowing which results in compaction, nutrient leaching, and
loss of water retention ability.
2. Fertilizers and pesticides
The use of agrochemicals in rice production is extremely high particularly in intensive
rice production systems. This is especially true in less developed countries where
farmers are less educated about best practices in farming that favor more sustainable
methods, and governments do little to regulate the use of agrochemical inputs. The
result is higher contamination of soil, air, and water. Insect pests and diseases also
develop increasing resistance to pesticides with each application, whereas their natural
predators are eliminated. Human health is also greatly affected with farmers reporting
greater incidence of illness than those who are less exposed to agrochemicals.
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4. Slash and burn
Removal of forest cover to make way for land to plant rice is common in very poor
communities who rely on rice growing as a source of food and income. However, this
fanning method results in top soil erosion, increased surface run-off resulting in
flooding in the low-lying areas, and loss of biodiversity.
5. Water demand
Intensive rice farming demands greater amounts of water especially in irrigated
lowland rice culture. This leads to water scarcity not only for agricultural uses, but
also for human consumption and urban needs.
Part 22: Efforts in Sustainable Rice Farming
1. Positive externalities
The traditional rice paddy has largely remained unchanged since rice was first cultured
over 10,000 years ago. Until the advent of the Green Revolution when rice growing
favored high yielding varieties that relied heavily on the use of inorganic fertilizers
and pesticides, rice growing was a sustainable and environment friendly agriculture
practice. In recent years, efforts are being made to bring back the traditional practices
that have made it survive thousands of years of population growth and human
development.
a. Reduction of floodwaters
Because rice fields are built to impound water, they are act as temporary flood
control structures particularly at the height of water flow. In the lowlands, they
contain overflows from rivers and estuaries thereby protecting human settlement
areas. Rice fields carved on hilly and mountainous terrain catch runoff thereby
preventing serious flooding in low-lying areas.
b. Recharging of the groundwater
Water in rice paddies percolates down to recharge the groundwater supply below.
The amount that percolates largely depends on the type of soil and the level of
water in the paddy. This action is particularly important in areas where the
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irrigation water is obtained from underground aquifers.
c. Preventing soil erosion
This is especially true for paddies constructed along hilly and mountainous areas.
The paddies prevent the loosening of the soil in times of heavy rainfall thereby
reducing the chances of landslides. Preventing surface soil erosion also prevents
soil nutrients from contaminating water sources.
d. Purifying water
Micro-organisms found within the paddies act as water purifiers by breaking down
and consuming organic pollutants. In addition to the purifying abilities of the soil,
water that percolates to the aquifers becomes cleaner and safer.
e. Controlling ambient temperature
Although rice paddies release methane, they also have air-cooling properties by
virtue of evapo-transpiration. Areas where 70% of the land is rice paddy can have
temperatures that are 2° lower in the middle of the day compared with areas
without paddies. Locating rice fields near urban areas can help reduce ambient
temperatures especially during the summer months.
f. Providing habitat for wetland species
The rice paddy is essentially a wetland habitat that supports various aquatic and
terrestrial plants and animals. In fact, in many areas in Asia, farmers raise tilapia
and other freshwater fish in their rice paddies as a supplementary source of
income. The fish feed on insects and organic matter while enriching the soil with
their wastes. Rice paddies also attract migratory birds.
2. The Sustainable Rice Platform
In late 2011, the United Nations Environment Programme, IRRI, Louis Dreyfus
Commodities and Kellogg Company created the Sustainable Rice Program with the
aim to “elevate rice production to a new level by helping farmers, whether subsistence
or market-focused, boost their rice production, keep the environment healthy,
facilitate safer working conditions, and generate higher incomes to address poverty
and improve food security.”
The goals of the initiative are the following;
a. To ensure that rice is grown in an environmentally sustainable and socially
responsible manner, management standards will be set for rice production;

. By reducing the cost of inputs, increasing production, and/or obtaining extra
benefits on their produce, poverty in poor rice farmers will be reduced; and
c. To assure consumers and processors that rice grown under the Platform is not only
beneficial to the environment, but also to the welfare of farmers.
Part 23: Genetic Improvement
Conventional breeding methods have created thousands of rice varieties that, along with
improved cultural practices, have increased rice yields from about 200 million tons in the
1960s to 678 million tons in 2009. Such breeding methods have largely focused on
creating high yielding varieties with increased tolerance to pests and abiotic stresses.
But recent advances in molecular biology and biotechnology techniques have made it
possible to not only overcome genetic barriers in conventional breeding, but also pinpoint
genes responsible for specific characteristics in rice that could enhance its performance.
These genes make it possible for targeted breeding to develop rice varieties specifically
expressing that gene.
Genetic improvements in rice are currently focused on the following characteristics:
1. Increased yield;
2. Resistance to biotic stresses;
3. Resistance to abiotic stresses;
4. Nutrient-use efficiency; and
5. Improved grain quality.
Recent successes have included the creation of rice that can produce beta-carotene, the
precursor to Vitamin A, the identification of a gene responsible for increased phosphorus
uptake that enables rice to grow in phosphorus-deficient soils without the addition of
inorganic fertilizers, and the identification of a gene responsible for increased number of
grains resulting in increased yields.
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76

Conclusion
Rice has been an important source of food and income for humans for thousands of years and
with more than three billion people subsisting on it, it is likely that it will continue to be an
important staple food for thousands of years more.
The basic principles of rice growing have remained the same through the years but the
techniques have improved along with advancements in science and technology.
Rice growing has been an important learning tool for world politics, economics,
environmental science, social science, engineering, and the life sciences.
As new production techniques are developed, the goal of rice growing will continue to be
increasing yield and profitability and improving grain quality.
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5. University of California Davis Department of Plant Biology. (2012). Where rice came
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81

The information within this book will help you maximise your effort and
finances with regards to rice farming.
Increase your crop yield by 30%, 50% or even 100% using simple methods.
Rice is one of the three most important crops in the world w ith the other two
being corn and wheat. An estimated 3.5 billion people, more than half of the
world’s population, consume rice as a staple food. It is grown in every
continent except Antarctica and is the source of livelihood for more than one ^
billion people. <
Ninety percent of rice production is concentrated in Asia, w here rice is grow n
in roughly 200 million, mostly small-scale rice farms. Two species of rice are
currently cultivated: Oryza sativa, or Asian rice, and Oryza glaberrima, or
African rice. The former is the most common species grown worldwide, whereas
the latter’s cultivation is limited to West Africa, from where it is believed to
have originated.
Chapters include:-
- Important advances in rice production
- Assessing climate, soil & water
- Crop Management
- Overview of rice production systems
- Efforts in sustainable rice farming
Discover methods used to increase rice crop yield to achieve a higher quality
rice crop along with requiring less resources such as less seeds, less water and
even less land to grow the same quantity of rice.
ISBN 9781480236271
781480 236271