Irrigation and shifting planting date as climate change adaptation strategies for sorghum

Climate change is projected to have a global impact that affect food production and security. The objectives of this study were to determine the potential impact of climate change on sorghum yield for rainfed production systems and to evaluate the potential of irrigation and shifting planting dates as adaptation options for two major sorghum production regions in Ethiopia. The Decision Support System for Agrotechnology Transfer (DSSAT) Cropping System Model (CSM)-CERES-Sorghum model was used to simulate the impact of climate change on sorghum yield for two Representative Concentration Pathways (RCPs; RCP 4.5 and RCP 8.5) and for three future periods including the 2025s (2010–2039), 2055s (2040–2069), and 2085s (2070–2099). The Agricultural Model Improvement and Inter-comparison Project (AgMIP) framework was used to select five representative GCMs for hot/dry, cool/dry, middle, hot/wet, and cool/wet climate scenarios. Two climate change adaptation practices including supplemental irrigation at two levels (deficit and full) to the current rainfed production system and shifting planting dates were evaluated. The CSM-CERES-Sorghum model was calibrated and evaluated using eight years of experimental data from Meisso, eastern Ethiopia. The model was then run for Kobo and Meisso under different climate change and crop management scenarios. Based on model evaluation results, the model performed well for simulating sorghum yield (R2=0.99), anthesis (R2=0.86, RMSE=1.3), and maturity (R2=0.79, RMSE=4.4). The results showed that the average temperature for Kobo and Meisso is expected to increase by up to 6 °C under RCP8.5 in 2085. For the rainfed production systems without adaptation practices, drought stress is projected to intensify during anthesis, which was reflected by projected yield reductions by up 2 tha−1 for the two sites. Full irrigation was effective in reducing moisture stress and, thereby, increasing sorghum yield by up to 3 tha−1 for Kobo and 2 tha−1 for Meisso. On average, full irrigation resulted in a 1 tha−1 yield increase compared with deficit irrigation. Early planting dates also resulted in an increase in yield compared to the baseline planting dates, especially when combined with supplemental irrigation, although late planting was consistently disadvantageous even with supplemental irrigation. This study highlighted that the CSM-CERES-Sorghum model can be effectively used to simulate climate change effects on sorghum yield and evaluate different climate change adaptation practices. The outcomes of this study can also help to implement management decisions towards climate change adaptation for the current subsistence and fragile rainfed crop production system in Ethiopia and similar ecoregions across the globe.