Effects of water deficiency and plant density on some quantitative and qualitative characteristics of two soybean (Glycine max L.merr) cultivars in Varamin region

To find the best plant density and study the compatibility of soybean cultivars in water stress condition, a field experiment was performed in randomized complete block design with split-factorial arrangement with 4 replication during 2009. the main plots were to two irrigation regimes (T1=normal irrigation, T2=100mm evaporation from the surface of evaporation basin); sub plots were jointly three levels of plant densities (60, 80 &100 plant per m2) and two soybean cultivars (Williams & mutant clarck).The studied traits were seed yield, harvest index, seed oil percentage and oleic and palmitic acids Contents. The results showed significant differences among different level of irrigation, plant densities and cultivars. The highest values of measured traits were achieved in normal irrigation and the lowest in water stress condition. Increase of plant density from 60 to 100 plant per m2 decreased all the traits. The seed yield and harvest index of cv. Williams was more than cv. Mutant clarck, while seed oil percentage of cv. Mutant clarck was higher than that of Williams. However, palmitic and oleic acids contents were not significantly different in two cultivars. Maximum and the minimum seed yield were obtained in the highest and lowest plant densities respectively. Increased of plant density from 60 to 100 plants per m2, decreased seed oil percentage in both irrigation regimes and both cultivars. Increase of plant density also decreased palmitic and oleic acids contents in both irrigation regimes and both cultivars.