RESPONSE OF SOYBEAN CULTIVARS TO WATER STRESS AT REPRODUCTIVE STAGES

A split plot experiment on the basis of RCB design with four replications was conducted in 2011, to investigate the effects of different irrigation treatments (I1, I2, I3 and I4: well-watering after 70 mm evaporation from class A pan and irrigation disruptions during flowering, during grain filling and during flowering and grain filling stages, respectively) on ground cover and yield of three soybean cultivars (Clark, Williams and L17). Water stress at reproductive stages reduced percentage and duration of ground cover, plant biomass, pods per plant, grains per plant, mean grain weight, harvest index and grain yield per unit area. However, grains per pod did not differ significantly among irrigation treatments. Reduction in grain yield was increased with increasing duration of water stress at reproductive stages. Williams was a superior cultivar in ground cover, plant biomass, mean 100 grain weight and grain yield per unit area. Interaction of cultivar × irrigation was not significant for yield and yield component. Plant biomass was statistically similar for Clark and L17. Grain yield of L17 was 4.49 % and 17.33 % less than that of Clark and Williams, respectively. It is, therefore, essential to provide sufficient water during flowering and grain filling stages in order to prevent yield loss in soybean cultivars.