EVALUATION OF SELECTED CROP YIELD WATER USE MODELS FOR A WHEAT CROP.
EVALUATION OF SELECTED CROP YIELD WATER USE MODELS FOR A WHEAT CROP.
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Date
1997-12
Authors
IGBADUN, HENRY
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Abstract
Relationships between crop yields (dry matter and grain yields) and
seasonal evapotranspiration for wheat in Samaru- Zaria, Nigeria, under conditions
of moisture stress caused by evapotranspiration deficits at four growth stages of
the wheat crop are presented. Wheat, (Triticum aestivum L.CV. sete ceros) was
planted in the Institute for Agricultural Research (I..R.) farm during the 1995/96
cool harmattan season, under irrigation. Evapotranspiration deficits were created
by withholding irrigation for some days in excess of the regular 7 day irrigation
interval at each of the four growth stages considered. The resultant moisture
stress affected grain and dry matter yields. Crop water use was monitored
throughout the season for each treatment and grain and dry matter yields were
recorded at harvest.
Two multiplicative crop yield models: Jensen(1968) and Minnas et al
(1974); and two additive models: Stewart et al (1977) and Bras and Cordova
(1981) were evaluated using the experimental data, and their stress sensitivity
factors estimated for the four growth stages considered. Their accuracy and
predictability of crop yields were also tested. The results indicated that strong
linear relationships exist between grain and dry matter yields and seasonal
evapotranspiration within the limits tested. An evapotranspiration (ET) threshold
of 69.3mm is required for dry matter yield initiation, while an ET threshold of
145mm is required for grain yield. Thereafter, an increment of 10.2 kg/ha in
grain yield and 22.5kg/ha in dry matter yield is expected for every mm of crop
water use. The four models, using the estimated stress sensitivity factors, were
found to adequately predict crop yield. However, the Jensen (1968) and Bras and
Cordova(198l) models predicted closer results than the others.
The grain yield losses due to the moisture stress caused by the
evapotranspiration deficits were relatively equal to the dry matter yield losses at
booting to heading stage, and at soft dough to hard dough development, while
moisture stress at flowering to milkdough development had greater yield reduction
effect on the grain yield than dry matter yield.
Description
Being a thesis submitted to the Post Graduate School, Ahmadu Bello
University, Zaria, in partial fulfillment of the requirement for the award of
Master of Science degree in Agricultural Engineering.
December, 1997.
Keywords
EVALUATION,, SELECTED,, CROP,, YIELD,, WATER,, MODELS,, WHEAT,, CROP..