Quantifying future climate impacts on maize productivity under different irrigation management strategies: A high-resolution spatial analysis in the US Great Plains

Producers east of the 100th meridian, a historically wetter portion of the Great Plains, face uncertainties regarding yield, irrigation water use, water productivity, and net returns due to the impacts of climate change in the region. These climate change impacts are spatially variable with a heterogeneous response to environmental variability and different water management techniques. Therefore, the present study addresses climate change impacts on irrigated maize productivity in the Eastern Kansas River Basin of the Great Plains at a fine spatial scale using Shawnee County, Kansas as a case study. We incorporated spatially variable soils and grid-level historical and future climate scenarios under different irrigation management strategies as inputs to CERESMaize crop model. Our model validations closely matched observed yield and irrigation water use, with index of agreement values exceeding 0.85. Future climate projections (RCPs 4.5 and 8.5) were analyzed across three 25-year periods (2025-2049, 2050-2074, and 2075-2099) relative to historical conditions (1991-2015). Results showed yield declines of 21-38 % and 22-70 % (RCPs 4.5 and 8.5, respectively) due to shortened growing season length. Irrigation water use under full allocation increased by 9-23 %, while net returns declined significantly, resulting in significant decline in water productivity. We found that deficit irrigation strategies saved 3-15 % of water without further diminishing maize productivity. These findings highlight the importance of fine scale climate impact analysis of crop productivity. Future maize production in the region necessitates integrating yield-advancing cultivars with improved water management found in this study in order to meet the expected grain demand over the next decades.