Effect of Water Stress on Yield and Yield Components of Three Soybean Cultivars

In order to evaluate the effect of water regims on yield and yield components of soybean in Urmia region, a field experiment was conducted at Urmia Agricultural Research School during 2012 in the form of split plot based on randomized complete block with three replications. The main and subplot were three levels (optimum irigation 60 mm, moderate water stress 110mm and severe water stress 160mm evapration by evapration pan Class A) and three cultivars (Clark, Wiliyams and Onion), respectively. In this experiment traits of total number of node, number of sceondary stem, total number of pod, grain per plant, grain yield, 1000-grain weight, biological yield and harvest index were investigated. The results of variance analysis showed that the effect of water stress on all of the traits was significant at 1% probability. The simple effect of cultivar on the number of sceondary stem, grains per plant, grain yield, biological yield and harvest index were significant. Mean comparison showed that with increasing water stress, all of the traits deacresed significantly so that the highest and lowest obtained by optimum irrigation and severe water stress, respectively. Severe water stress reduced the grain yield by 63 and 45% compared to the optimum irrigation and moderate water stress, respectively. In optimum irrigation and severe water stress conditions, the highest grain yield ontained by Onion cultivar. In this study, Onion cultivar had a good adaptation to stress conditions and it is recommended for areas with dry and semi-arid climates.