Soybean yield under water deficit conditions

Drought stress is the main environmental factor that limiting crops growth and productivity in Iran. Therefore, in order to evaluate effects of water deficit on yield and yield components of soybean, an experiment was performed in the research field of the Islamic Azad University of Kermanshah, Iran. Response of four soybean cultivars at four irrigation regimes investigated based on randomized complete block design with three replications. At the end of growth season, ten plants were selected randomly from each plot and then final yield and yield component were measured. The results of this experiment show that there are significant differences among cultivars in yield and yield components at different irrigation regimes. The lowest values of grain and biological yield were obtained under condition in which water stress occurred in R1 that indicating the importance and sensitivity of this stage in plant life cycle. Also, number of pod and seed per plant decreased when that withholding irrigation occurred at the early of flowering stage. Withholding irrigation at seed-filling stage had the most effects on reducing seed weight. Therefore, the lowest 100-seed weight per plant was obtained when withholding irrigation at R6. The results of path coefficient analysis were shown that seed/plant and seed weight had high and positive direct effects on seed yield. In addition, Withholding irrigation at R3 had more effect on reducing pod and seed dry weight