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Averaged over the 7 rates of nitrogen fertilization the straw-to-grain ratios for Inia, Ciano, Noroeste and PM2 were 1.45, 1.36, 1.42, and 1.22, respectively. All of these ratios are low and indic te that the wheat plants were very efficient In producing grain. This is normally not true for very late plantings and probably reflects the influence of a relatively co'ol April. The PM2 plants were about 15% more efficient in grain production than the double dwarf varietie . Effect of Flooding on Wh at Development In irrigated agriculture, the root zone of slowly permeable soils is often partially saturated for several days following an irrigation. Similar soil conditions occur in rainfed agriculture during periods of continuous rains. Reports indicate that the development and yield of wheat are adversely affected by he low oxygen diffusion rates in the root zone associated with such saturated soil conditions. The way in which an excess 01 soil The movement of water into the soil on irrigating is observed using'a set of tensiometers installed at varying depths from six inches to 5 feet. Show here, the tensiometers are being read on one tier of plots, while another tier is irrigated. The interaction among 3 variables was studied in a wheat experiment comprising three varieties, 4 rates of nitrogen and 4 irrigation treatments. The experiment as shown below included a two meter strip across the center of the irrigation treatments for sampling to determine moisture contents. 122
moisture affects wheat development is believed to depend upon the stage of growth at the time it occurs. Reported effects include a reduction in the number of tillers, the fertility of the spikes, and the size of the grain. The effects of flooding on wheat development have been studied at the Northwest Agricultural Research Center (CIANO) Mexico, during the past two seasons. The soils in this region are heavy clays and farmers have an ample supply of low cost irrigation water; these conditions suggested that an excess of soil moisture after irrigating might be a yieldlimiting factor. In 1969-70, wheat production in normally irrigated plots was compared with that in plots flooded for 4 or 8 days at different times during the growing season. The soil was a heavy clay with a bulk density that varied with depth from 1.1 in the 0-30 cm horizon, to 1.35 in the 60-90 cm horizon, to 1.20 at the 120 cm depth. Apparently the more dense horizon below 60 cm was almost impermeable to water, as little penetration occurred below that depth, even in plots flooded for as long as 4 days. Oxygen diffusion rates were measured as soon as possible after flooding and the measurements were continued until the rates were adequate for normal growth. After a normal irrigation, the oxygen diffusion rate remained below 0.2 micrograms/cm 2 /min at a soil depth of 15 cm for a period of 9 to 12 days. Following 4 days of flooding, the oxygen diffusion rate was less than 0.2 micrograms/cm 2 /min at a 15 cm depth for 12 to 15 days. Flooding was found to affect plant development in several ways: Flooding for 4 days at planting time reduced plant emergence by 17 percent and plant height at 26 days by 11 percent. The number of heads .and grain yield decreased very slightly. Flooding for 4 days, at 15 and 30 days after planting, increased plant height and the number of tillers per plant at 53 days. Straw yields were increased by about 16 percent. At 45 days after planting, flooding reduced plant height, tiller density at 53 days, grain size, grain yield and straw yield; it did not change the number of grains per head. Flooding for 4 days at 60 and 75 days after planting had no significant effect on wheat development. Flooding for 8 days at 65 days after planting slightly increased both grain size and yield. The INIA variety used in this study flowered at 61 days after planting. Evidently, as far as grain yield was concerned, the INIA wheat variety was most sensitive to a low oxygen diffusion rate at planting time and about 45 days later. The effect of flooding at 45 days was similar to that observed in 1968-69, when flooding at 38 days reduced both plant height and straw yields. Surprisingly, flooding for four days at 15, 30, 60 and 75 days after planting, did not reduce grain yields; while flooding for 8 days, at 65 days after planting, slightly increased yields. Similar results were obtained in a growth chamber study at the University of California at Riverside, which found that maximum production of wheat grain occurred at atmospheric oxygen levels about one-fourth normal level. Results obtained in studies conducted during the past two years clearly indicate that present wheat varieties can tolerate several days of flooding without important reductions in yield. Further information is needed on the quantitative effects of low oxygen diffusion rates occurring about 45 days after planting. Timing of the Second Irrigation for Wheat Field studies conducted in India over the past 5 years have shown that maximum wheat yields are obtained when the first irrigation after planting is made 20 to 25 days following planting, when crown root development begins. CIANO experiments in 1969-1970 have obtained more information on this point. Second irrigations in both years were applied 15, 22, 29, 36 and 43 days after planting. The varieties used in the 1969 experiments were Sonora 64 and Tobari, while Sonora 64 and INIA were used in 1970. Grain yields of Sonora 64 and Tobari were 5.00 and 4.78 ton/ha, respectively, in 1969. Timing of the second irrigation did not affect yields significantly. The INIA variety produced equal yields of 3.67 ton/ha in 1970 when the second irrigation was applied 15, 22, 29, and 36 days after planting. Delaying the second irrigation until 43 days after planting reduced the grain yield to 3.46 ton/ha. The Sonora 64 variety produced the highest yields, 4.30 ton/ha, when the second irrigation was applied at 22 or 29 days after planting. Yields were slightly less (4.00 ton/ha) when the second irrigation was applied at 15 or 36 days after planting. These results are not conclusive, but, in the case of Sonora 64, do provide some evidence that application of the second irrigation at about 25 days after planting is essential for maximum grain production. 123
Page 1 and 2:
REPORT ON PROGRESS TOWARD INCREASIN
Page 3 and 4:
Contents Page INDEX Page INDEX 3 BO
Page 5 and 6:
Board of Directors JUAN GIL PRECIAD
Page 7 and 8:
WHEAT HEADQUARTERS STAFF NORMAN E.
Page 9 and 10:
Introduction Throughout the develop
Page 11 and 12:
sistance, ~etc. is obtained in one
Page 13:
Puebla can be readily transferred a
Page 16 and 17:
In support of these global efforts.
Page 18 and 19:
In the case of Opaque-2 populations
Page 20 and 21:
High Protein Quality Mutants from P
Page 22 and 23:
Quantitative Approach in Improving
Page 24 and 25:
BREEDING In CIMMYT's maize breeding
Page 26 and 27:
To generate a maize population of m
Page 28 and 29:
During the past year, grain-to-stov
Page 30 and 31:
Based on one year's data, the corre
Page 32 and 33:
A Comparisonof of Two Methods of of
Page 34 and 35:
With the same purpose in mind, 35 S
Page 36 and 37:
Two rates of N (80 and 160 kgsjha)
Page 38 and 39:
TABLE 20. Incidence of stunt diseas
Page 40 and 41:
ENTOMOLOGY Stem Borer Resistance An
Page 42 and 43:
TABLE 23. Percent mortality of Sito
Page 44 and 45:
Optimum Sample Size for Determining
Page 46 and 47:
the workshop were to: review work d
Page 48 and 49:
A project was initiated in 1968 to
Page 50 and 51:
station produced seed of synthetics
Page 52 and 53:
crossed to 250 elite varietal colle
Page 55 and 56:
WHEAT 57 MEXICO: The Joint CIMMYT·
Page 57 and 58:
duced under very unfavorable weathe
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for research on spring wheat improv
Page 61 and 62:
inary yield tests and were given th
Page 63 and 64:
est climate and locations for ident
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TABLE W5. Grain yields of ten of th
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sound scientific approach, incorpor
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TABLE W8. Lines from the Bread Whea
Page 71 and 72:
TABLE W10. Seedling and adult plant
Page 73 and 74: Nematode Damage on Wheat For the pa
Page 75 and 76: !las been done by Dr. Mario Vela of
Page 77 and 78: ~~-----~ tein. The protein ranged f
Page 79 and 80: Cultural Practices: Special attenti
Page 81 and 82: grain is highly undesirable and pro
Page 83 and 84: 21 20 " " VHrl ,. ,, . :'. . i ,.."
Page 85 and 86: HA'UR HAPUR MARlEr MARrET WUA'l'PII
Page 87 and 88: market for consumer goods. How much
Page 89 and 90: ern Rajasthan. At 20% urea concentr
Page 91 and 92: and other governmental and semi-gov
Page 93 and 94: the Effect of Tube Well Development
Page 95 and 96: The Need for Continued Teamwork One
Page 97 and 98: of ofboth both breadand and durum w
Page 99 and 100: evaluation on Septaria resistance.
Page 101 and 102: A cost benefit ratio of 2.9 to 1 is
Page 103 and 104: denser stands resulting from improv
Page 105 and 106: seed needs for next year and for po
Page 107 and 108: TABLE W22. Effect ·of different ra
Page 109 and 110: TABLE W24. The Highest Yielding Lin
Page 111 and 112: to dwarfs, cover about 20 percent o
Page 113 and 114: which removed the leaves during the
Page 115: the milk stage of development. It i
Page 118 and 119: PROMOTION OF ACCELERATED MAIZE PROD
Page 120 and 121: nitrogen applied in the usual manne
Page 122 and 123: pIing dates. Nitrogen fertilization
Page 126 and 127: Response of Triticales to Nitrogen
Page 128 and 129: problem is due to aluminum toxicity
Page 130 and 131: five percent and one percent as sto
Page 133 and 134: COMMUNICATIONS INTRODUCTION Page IN
Page 135 and 136: TABLE C1. USA MEXICO and CANADA CEN
Page 137 and 138: A third film on the Puebla Project
Page 139: SOURCES OF SUPPORT FOR 1970 GENERAL
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