Effect of Climate Change and Evaluation of Planting Date on Soybean Yield

Climate change affects precipitation and temperature patterns and, hence, may affect the crops yield. In this study investigated the simulation of grain yield and biomass of soybean under future climate in different irrigation treatments and different planting date as adaptation strategy using AquaCrop model. For this purpose, the data of precipitation, minimum temperature, maximum temperature and sunshine hours and the LARS-WG statistical downscaling model was used from HadCM3 atmospheric general circulation model and under emission scenarios A2 and B1, in the periods 2011- 2038, 2039-2066 and 2067-2094. AquaCrop model was calibrated and validated by the data collected in the field before being used. Finally, the amount of grain yield and biomass simulated in future periods, for 6 different planting dates and for treatments of 100%, 75% and 55% water requirement. Based on the results, under emission scenarios A2 and B1 in 17 June for the period 2011- 2038 as compared to the base period (1981-2008), the amount of simulated biomass and grain yield, decreased, respectively, between 5 to 11.5% and 8.3 to 13.7% and for the period 2039-2066 increased, respectively, between 18.6 to 24% and 16 to 24.4%, and for the period 2067-2094 increased between 9 to 21.8% and 7.2 to 21.2%. Also, by selecting planting date of 20 June, the largest increase of biomass and grain yield were simulated for periods 2011-2038, 2039-2066, and 2067-2094 under the A2 and B1 scenarios. These results will be useful for future irrigation planning in Gorgan area.