Assessment of the Impacts of Climate Change on Soybean Yield and Water Requirement Using Crop Models

Climate change can have significant impacts on crop growth, yield, water requirement and, consequently, crop water productivity. In this study, the effect of climate change under RCP2.6, RCP4.5, and RCP8.5 projection scenarios of the CanESM2 model on soybean yield and water requirement was investigated in Kermanshah, west of Iran. Crop growth was simulated using crop growth simulation models (DSSAT and AquaCrop) based on historical (1985-2015) and projected (2025-2064) weather data. Using the AquaCrop model in RCP2.6, RCP4.5, and RCP8.5 scenarios, the average increase in seasonal crop evapotranspiration (ETc) was estimated to be 9.4, 11, and 14.9%, respectively. The results of the DSSAT model showed 4.1, 8.5, and 12.1% increase in seasonal ETc under the RCP2.6, RCP4.5, and RCP8.5 scenarios, respectively. Based on the AquaCrop and DSSAT models, soybean yield decreases by 5.3, 3.7, and 2% and by 5.7, 4.8, and 1.6% for the RCP8.5, RCP4.5, and RCP2.6 scenarios, respectively. The results also show a decrease in crop water productivity under climate change scenarios as a result of increased ETc and reduced grain yield. According to AquaCrop and DSSAT models, the maximum daily ETc that should be used for the design of irrigation systems will increase by 11.5 and 10.2%, respectively.