Soybean Response to Drought and Seed Inoculation

Drought is one of the most important factors that limits N fixation, growth and yield of soybean. 2 The aim of this study was to determine the effects of water stress, starter N application and seed inoculation on yield and yield components of soybean (cv. Williams). The experiment was conducted in 2010 at the Islamshahr town that located in 12 km of South-west of Tehran, the capital of Iran. The experiment was laid out in a split plot on the basis of randomized complete block design with three replications that placed different irrigation levels (irrigation after, E0= 40, E1= 80 and E2= 120 mm evaporation from the class “A pan” evaporation) in the main plots and seed inoculation treatments (I0= 0 kg N ha + un-inoculation, I1= 20 kg N 1 ha + inoculation with Rhizobium japonicum, I2= 20 kg N ha + inoculation with Azotobacter chroococcum, 1 1 I3= 20 kg N ha + inoculation with Azospirillium brasilense, I4= 20 kg N ha + inoculation with mix of bacteria, 1 1 I5= 20 kg N ha + un-inoculation and I6= 100 kg N ha + un-inoculation) in the sub plots. Results showed that 1 1 water stress decreased bacteria activity, number of pods per plant, number of seeds per pod, seed weight and seed yield. Under optimum and water stress conditions, application of 20 kg N ha as starter and seed 1 inoculation especially with mix of bacteria, produced maximum yield.