Combined and separate effects of future climate change and elevated atmospheric CO2 on maize growth and water consumption in the US Corn Belt.

BACKGROUND: The joint effects of climate change and rising atmospheric CO2 concentration ([CO2]) can alter maize phenology, yield, and water use, but the extent to which elevated [CO2] offsets climate-related impacts on C4 maize remains uncertain. This study quantified the combined and separate effects of future climate change and elevated [CO2] on irrigated maize growth and water consumption in the Southwestern Plain of the Great Lakes (SPG) - a region of the US Corn Belt. A validated Agricultural Production Systems sIMulator (APSIM) model was driven by three bias-corrected global climate models (GCMs) under Representative Concentration Pathways (RCPs) 4.5 and 8.5 for the near-future (2025-2049), mid-future (2050-2074), and far-future (2075-2099) periods. For each period, paired simulations were conducted using baseline [CO₂] (378 ppm) and period-specific elevated [CO₂] concentrations. RESULTS: Maximum temperature increased more than minimum temperature during the growing season. Compared with RCP 4.5, RCP 8.5 resulted in a greater shortening of growing-season duration under warming (GSD-w), greater yield loss, and a greater increase in water footprint. Annual precipitation increased toward the far future under RCP 8.5, whereas growing-season precipitation showed a non-monotonic response and fell below the 1995-2014 baseline in the far future. Elevated [CO2] reduced average projected yield losses by 2.7 percentage points under RCP 4.5 and by 3.5 percentage points under RCP 8.5, while reducing water footprints by 12.1% under RCP 4.5 and by 19.3% under RCP 8.5. However, elevated [CO₂] offset GSD-w shortening by only 0.2 days under RCP 4.5 and 0.3 days under RCP 8.5. CONCLUSION: Elevated [CO2] partially alleviated climate-related yield losses and increases in water footprint but did not offset the adverse effects of future warming, particularly under RCP 8.5. Adaptation strategies should combine region-specific water management with adjustments in sowing date and cultivar selection. © 2026 Society of Chemical Industry.