Soybean production in 2025 and 2050 in the southeastern USA based on the SimCLIM and the CSM-CROPGRO-Soybean models

This study developed an approach to determine the potential impact of climate change on soybean yield for 2025 and 2050 projections by combining the statistical downscaling model SimCLIM with the crop simulation model CSM-CROPGRO-Soybean. SimCLIM is an integrated assessment model (IAM) which can provide site-specific projections by using statistical downscaling based on 21 general circulation models (GCMs) and 6 greenhouse gas emission scenarios. The response of rainfed and irrigated soybean growth and yield to climate patterns based on 3 GCMs and 6 emission scenarios was investigated. Tifton, Georgia, USA (31.48° N, 83.53°W) was selected as an example location. The increase in temperature caused the number of days to maturity to decrease by 1.8 d for 2025 and by 2.3 d for 2050 compared to the reference years for both rainfed and irrigated conditions; however, later planted soybean showed a lower decrease. Increases in precipitation during the soybean growing season and in CO₂ concentration led to projected yield increases of 6 to 22% for 2025 and 8 to 35% for 2050 for rainfed conditions. Projected increases for irrigated soybean yield were about 1 to 12% less than for rainfed soya. Generally, Tifton is suitable for both rainfed and irrigated soybean planting based on projections by the 3 GCMs. Farmers might have to shift the planting date to after June 5 to avoid potential heat stress. The cultivars that are suitable for rainfed conditions include AG6702 and S80-P2, while DP5634RR, DP5915RR, and AG6702 are more suitable for irrigated conditions.