Evaluation of Climate Change Impacts and Effectiveness of Adaptation Options on Crop Yields in the Southeastern United States.

The Environmental Policy Integrated Climate model was used to evaluate the potential impacts of climate change adaptations on yields of corn (Zea mays L.)  and soybean (Glycine max L.), as well as aggregated yields of C₃ [soybean, alfalfa (Medicago sativa L.), winter wheat (Triticum aestivum L.)] and C₄ [corn, sorghum (Sorghum bicolor L.), pearl millet (Pennisetum glaucum L.)] crop types from representative farms in Alabama, Arkansas, Missouri, Mississippi, Florida, Kentucky, Louisiana, Texas, Georgia, and Tennessee that were grouped into North, South, and West regions. Adaptations included annual biochar applications and irrigation. Historical baseline (1979 – 2009) and future (2038 – 2068) climate scenarios were used for simulations with baseline and future CO₂ concentrations of 360 ppmv and 500 ppmv, respectively. The experiment was analyzed as randomized complete block design with split-plots in time for baseline vs. future comparisons, and as randomized complete block design with repeated measures for comparisons between periods. Compared to historical baseline scenario, corn yields initially increased from 36% to 84% depending on region. However, future corn yields significantly decreased by 3-15% across the entire Southeastern US in 2038-2068 due to temperature stress. Compared to the historical baseline scenario, soybean yields have decreased. Future soybean yields significantly decreased by 1-13% due to temperature and moisture stresses. C₄ crops produced higher yields compared to historical C₄ yields. C₃ crops historical baseline and future yields were not significantly different. Annual biochar applications caused significant yield reductions of 1-20% for corn, soybean, C_3, and C₄ crop yields depending on region. Irrigation caused significant increases in corn yields up to 33% for the South region, with no effect on soybean yields. Irrigation resulted in increased C₃ and C₄ crop yields for farms in drier areas. Under some weather scenarios, irrigation may be a promising potential adaptation strategy for agriculture in the Southeastern US.