The evaluation of drought stress impact as irrigation withholding at reproductive stages on quantitative and qualitative performance of soybean cultivars

In order to assess the performance of two soybean cultivars produced in two regions including Karaj and Moghan to drought stress at reproductive stages and also the impact of drought stress on yield and its components, oil and protein percent, an experiment was conducted as a split factorial based on complete randomized block design in three replications in agriculture faculty of Tarbiat Modares University during 2014. Four treatments of drought stress were exerted as complete withholding irrigation at flowering stage (R1-R3), pod formation (R3-R5), seed filling stage (R5-R7) and control (no withholding of irrigation) which were placed in main plot and other treatments were two soybean cultivars (‘Williams’ and ‘L17’) and two seed production sources (Karaj and Moghan) that were placed in sub plots. The results indicated that the effect of drought stress on pod number, 1000-seeds weight, seed yield and also oil and protein percent was significant. The highest seed yield (262.73 gram per meter square) was observed in control (no stress) and the lowest yield (162.22 gram per meter square) belonged to drought stress at pod formation stage. Also the interactions of drought stress × cultivar and drought stress × seed source were significant on grain yield. The lowest seed oil percent (18.24 percent) and the highest protein percent (37.28 percent) of seeds were obtained at seed filling stage. With considering these results, the irrigation at pod formation stage (R3-R5) is necessary for preventing the reduction of soybean seed’s yield.