Influence of Water Deficit on Oil and Protein Content of Soybean (Glycine max L.) Seed

A split-split-plot experiment with randomized complete block design in three replications was conducted in 2004 at the Research Station of the Faculty of Agriculture, University of Tabriz, Tabriz, Iran, to investigate the effects of water limitation on oil and protein accumulation in soybean seeds. Irrigation treatments (I1, I2, I3 and I4: irrigation after 60±3, 80±3, 100±3 and 120±3 mm, from class A pan, respectively) were assigned to main plot, two soybean cultivars (Zane and Huck) were allocated to the subplots and harvest stages with six day intervals were considered as the sub-subplots. The results indicated that percentages of oil and protein in the seeds were not significantly affected by water deficit at different harvests. However, both oil and protein output per unit area were significantly reduced, as water deficit increased. By increasing mean 100 seeds weight, percentage of oil content decreased, but percentage of protein content increased. In general, it was concluded that soybean oil and protein production per unit area under full and limited irrigation conditions could be improved by increasing seed yield via selection of high- yielding varieties.