Samiha A. Ouda, Fouad A. F. Khalil, Mohamed R. K. Ashry and Kamal M. R. Yousef( 2008). Effect of Water Stress on Soybean Yield and Water RelationsTwelfth International Water Technology Conference, IWTC12 2008, Alexandria, Egypt
Abstract: Two field experiments were conducted at Giza Agricultural Research Station, Agricultural Research Center, Egypt in 2006 and 2007 growing seasons to study the effect of three irrigation treatments (irrigation using 1.2 pan evaporation coefficient, irrigation using 1.0 pan evaporation coefficient and irrigation using 0.8 pan evaporation coefficient) on yield and water relations of soybean and to use Yield- Stress model to simulate the effect of saving irrigation water on soybean yield. Results
showed that all yield components were significantly affected by irrigation treatments over the two growing seasons, except for number of pods/plant in 2006 growing season and number of branches/plant and 100-seed weight in 2007 growing season.
Results also showed that the highest sobean yield and its components were obtained under irrigation using evaporation pan coefficient equal to 1.2, over all the two growing seasons. Furthermore, under irrigation with 1.0 pan evaporation coefficient,
soybean seed yield was reduced by 3.28 and 3.37% and biological yield was reduced by 5.61 and 3.54% over the two growing seasons, respectively. Moreover, soybean seed yield was reduced by 47.54 and 58.43% and biological yield was reduced by
37.38 and 58.59% under irrigation with 0.8 pan evaporation coefficient over the two growing seasons, respectively. The highest consumptive water used was obtained under irrigation with 1.2 pan evaporation coefficient i.e. 2395 and 2413 m3/fed for both growing seasons, respectively. The highest water use efficiency was obtained under irrigation with 1.0 evaporation pan coefficient. Yield-Stress model prediction showed good agreement between measured and predicted values of soybean seed and biological yield and consumptive water use, which facilitate using it in yield prediction under irrigation water saving. Running the model under deducting 10% of the amount of irrigation water of the control showed that soybean seed yield could be reduced by 4.91 and 5.49% for both growing seasons, respectively. Whereas, biological yield could be reduced by 5.61 and 5.05% for both growing seasons, respectively. Therefore, it could be concluded that to increase water use efficiency and to save irrigation water, it could be recommended to irrigate soybean with 1.0 evaporation pan coefficient. Furthermore, saving about 10% of the applied irrigation amount compared with the control treatment could reduce soybean seed yield and biological yield by an averge of 5.20 and 5.33% over the two growing seasons.
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