THE STUDY ON WATER BALANCE OF OILSEED CROPS IN THE NORTHERN THAILAND 1. WATER BALANCE OF SUNFLOWER UNDER IRRIGATION CONDITION
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Abstract
The study was conducted under three irrigation schedules as 7, 10 and 14 days interval at the MCC experimental plots in late December 1986. Sunflower seeds (Hysun # 33) were drilled on the two-rows seedbed with plant spacing 75 x 25 cm. At 15 DAE, side-banding of 15-15-15 fertilizer and Borax were applied with the rate of 200 and 12.5 kg ha-1 respectively and irrigation schedules with 50 mm of water per time were established. Soil moisture content at different depths (10 cm interval) was determined at one day before and after irrigation throughout the growing period. The PET, , and Kc values were calculated from the agrometeorological data. Crop water reguirement was calculated from the water balance equation by mean of lysimeter which installed in the middle of each experimental plot. WUE was also calculated from the ratio of grain yield to the total water used throughout the growing period. Plant samples were weekly taken to determine the yield components and finally the grain yield.
The results shown that total water used of sunflower crop throughout the growing season was 307.3 mm. The maximum values of , and Kc were 5.4 mm day -1 and 1.5, respectively. These values were found during the flowering period as same as the highest water reguirement. WUE based on grain yield was 0.8 kg m-3. Average soil moisture content and the amount of soil water uptake were different among the irrigation schedules. This brought to the differences in plant growth and grain yield. The highest growth rate and grain yield were recorded from the 10 days irrigation treatment.
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References
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