Effects of limited irrigation on yield and water productivity increasing of three soybean genotypes in Rasht region

In order to study the effect of limited irrigation on increasing the yield and water productivity of soybean, a split plot experiment based on a randomized complete block design with four replications was conducted in two cropping seasons of 2013 and 2014, in Rasht. Three irrigation treatments including two irrigations (I₂): irrigation at flowering and pod formation stages, three irrigations (I₃): irrigation at flowering, pod formation and ripening stages, and rainfed (I₀): as control treatment were allocated to the main plots and three soybean genotypes including Williams (V₁), L17 (V₂), and Habbit (V₃) to subplots. During the critical growth stages of the plant, based on the irrigation treatment and considering the precipitation and available moisture in the root zone, only one irrigation was applied (I₁) in 2013 while Williams and Habbit genotypes were, respectively, at pod formation and at flowering stage. But, in 2014 crop season, considering the lower precipitation, all irrigation treatments were conducted. Yield and yield components were measured at seed ripening time. The results showed that the limited irrigation in both years improved yield and yield components of all soybeans genotypes. The highest average grain yield in both crop seasons were obtained with I₁V₂ and I₃V₂ treatments, being 4616 and 4198 kg/ha, respectively. In both cropping seasons of 2013 and 2014, L17 genotype had the highest average grain yield compared with the other two genotypes, being 3932 and 3000 kg/ha, respectively, therefore, it can be recommended for planting in Rasht region. In 2013 and 2014 crop seasons, respectively, I₁V₂ and I₃V₂ treatments had the highest water productivity, corresponding to 1.72 and 0.97 kg/m³.