LAUSR

Abstract Adaptation measures are required to enhance climate change resilience of agricultural systems and reduce risks associated with climate change at both regional and global scales. The Texas High Plains is a semi-arid region that faces major challenges from climate change risks and dwindling groundwater supply from the exhaustible Ogallala Aquifer for sustaining irrigated agriculture. The overall goal of this study was to assess the impacts of climate change on yield and water use of grain sorghum and identify optimum climate change adaptation strategies for three study sites in the Texas High Plains. Future climate data projected by nine Global Circulation Models (GCMs) under two Representative Concentration Pathways (RCPs) of greenhouse gas emissions (RCPs 4.5 and 8.5) were used as input for the DSSAT CSM-CERES-Sorghum model. The climate change adaptation strategies were designed by modifying crop genotype parameters to incorporate drought tolerance, heat tolerance, high yield potential, and long maturity traits. Irrigated and dryland grain sorghum yield and irrigation water use were projected to decrease at varying percentages at the study sites in the future. On an average (of 9 GCMs), irrigated grain sorghum yield is expected to decrease by 5–13 % and 16–27 % by mid-century (2036–2065) and late-century (2066–2095), respectively under RCP 8.5 compared to the baseline (1976–2005). The irrigation water use is expected to decrease by 7–9% and 14–16 % by the mid-century and late-century, respectively. Among the adaptation strategies, an ideotype with high yield potential trait (10 % higher partitioning to the panicle, radiation use efficiency, and relative leaf size than the reference cultivar) resulted in maximum grain sorghum yield gains in the future under both irrigated (6.9 %–17.1 %) and dryland (7.5 %–17.1 %) conditions, when compared to the reference cultivar. Enhancing drought tolerance by increasing root density at different soil depths also resulted in a significantly higher irrigated grain sorghum yield than the reference cultivar. A longer maturity cultivar will likely increase irrigation water use and, therefore, is not recommended for water limited conditions.