Simulating Water Stress Effects in Soybean for Water Management in Delhi, India.

Water scarcity is expected to be a major challenge for most of South Asia due to increased water demand and poor water management leading to water related food scarcity. Objectives of this study is to observe the response of soybean to water deficit stress, and to simulate soybean growth and yield to identify suitable water management strategy for maximizing yield under drought scenarios. A field experiment was conducted to quantify the performance of soybean under water stress at different growth phases at Research Farm-IARI, New Delhi, India, with soybean (variety PUSA 2614) with five treatments subjected to water stress using rain-out shelter at different growth phase of plant. Results indicated that among the treatments, plants exposed to water stress during flowering and those exposed during vegetative growth phase had significantly low yield and TDM (Total Dry matter) as compared to other treatments. Experimental data was used to calibrate and validate the InfoCrop-soybean model before it is applied to simulate the optimal time of irrigation in different drought scenarios. This model was further used to simulate the impact of dry spells of different intensity and duration on growth yield of soybean crop. Thereafter the model was used to find optimal time of irrigation in 1620 drought scenarios for Delhi region using 36-year weather data from 1978 to 2014. Results indicated that in Delhi region, a 20% reduction in rainfall from climatological mean during any fortnight of crop season does not affect the crop yield significantly. From the above results, it can be concluded that, soybean yields are sensitive to water stress during 1^st and 2^nd fortnight of August and 1^st fortnight of September and these dry spells significantly reduce soybean yield in Delhi region and supplemental irrigation, in the event of dry spell, can minimize the yield loss.