Combined heat and drought suppress rainfed maize and soybean yields and modify irrigation benefits in the USA

Abstract Heat and water stress can drastically reduce crop yields, particularly when they co-occur, but their combined effects the mitigating potential of irrigation have not been simultaneously assessed at regional scale. We quantified temperature precipitation on county-level maize soybean yields from irrigated rainfed cropping in USA 1970–2010, estimated yield changes due to expected future precipitation. hypothesized that reductions would be induced jointly by heat during growing season, caused low total ( P GS ) high mean temperatures T over whole or many consecutive dry days CDD such spells within season. Whole season , intra-seasonal climatic indices had comparable explanatory power. Rainfed yielded least under warm conditions with longer higher spell temperature. Yields were lost faster warming conditions, lengthening conditions. For indices, loss per degree increase was larger wet compared benefit increased greater cooler The reverse true for soybean. An 2 °C no change gave a predicted reduction across counties 15.2% 27.6% Irrigation alleviated both stresses, even reverting response temperature, dependencies remained. provide carefully parameterized statistical models including interaction terms between improve predictions climate context-dependent benefits irrigation.