Modelling the impacts of climate change on the sustainability of rainfed and irrigated maize in Pakistan

Maize is a globally significant food crop but its future sustainability under rainfed conditions is at risk due to climate change and increased climate uncertainty. In Pakistan most maize is rainfed but there is increasing interest in the role of supplemental irrigation to reduce the vulnerability of crop yields to future drought and climate risks. Using a crop model (DSSAT CERES-Maize) with downscaled data from a weather generator (LARSWG) and for five selected GCMs, two RCPs (4.5 and 8.5) and two time slices (2050s and 2080s), this study assessed the impacts of climate change and climate variability on rainfed maize grown in the Pothwar region of Pakistan, and the extent to which irrigation could offset future yield reductions. Model simulations were calibrated and validated using experimental data from 2021 and 2022. The outputs showed that on average the yield of maize could be increased by 55% with a single irrigation of 60 mm during the reproductive stage. For the baseline (1991-2020) the average rainfed yield was 3370 kg/ha. The climate change scenarios for the 2050s indicated a -13.5% and -5.8% decline in rainfed yield under RCP4.5 and RCP8.5, respectively. Irrigation applications (between 162 mm and 180 mm) increased grain yields by 5615 kg/ha and 5732 kg/ha, respectively. For the 2080s scenarios there was a projected decrease in yield by -9.3% and -39.7% under RCP4.5 and RCP8.5, respectively. Modelling also confirmed significant reductions in maize biomass production which would negatively impact on feedstocks for both livestock and renewable energy generation.