SIMULATION OF THE EFFECT OF WATER STRESS ON SOYBEAN YIELD AND WATER USE EFFICIENCY

Yield-Stress model was calibrated and validated for soybean yield and consumptive use with data of four-year field trial at Beni Sweif Governorate, Egypt under two treatments of irrigation water quality (fresh and drainage). The goodness of fit between measured and predicted values by the model was tested by calculated percent difference between measured and predicted values of yield and consumptive use, in addition to root mean squared error and Willmott index of agreement. Then, the model was used to predict the effect of four deficit irrigation treatments (95, 90, 85, and 80% of full irrigation). Water use efficiency was calculated under all cases. The results showed that the model performance was highly acceptable in predicting soybean yield and consumptive use. Low yield losses occurred under both fresh and drainage deficit irrigation water as a result of saving of 15 % of irrigation water. Water use efficiency was the highest under irrigation with 80 % of full fresh or drainage water irrigation, which suggested that there is a high potentiality to save an ample amount up to 20 % of the irrigation water to be used in cultivating more lands and increase soybean production.