Modifying Sowing date as an Adaptation Strategy to Climate Change in Grain Maize (Zea mays L.) Under mild-arid Climates as Simulated by the SSM-Maize Model

Climate change is currently considered the most important threat to sustainable development goals, particularly those goals related to the agricultural sector. The current research investigated sowing date as a strategy for adapting maize to climate change conditions in six sites of Kermanshah province characterized with a mild-arid climate using the SSM-Maize crop simulation model, HadGEM2-ES (the Hadley Centre Global Environmental Model version 2 Earth System configuration) climate model, and AgMIP (the Agricultural Model Intercomparison and Improvement Project) protocol under two emission scenarios (Representative Concentration Pathways: RCP4.5 and RCP8.5). Based on the simulation results, with temperatures rising (14% and 20% in RCP4.5 and RCP8.5, respectively) above the current threshold and CO2 concentrations increasing by 499 and 571 ppm in RCP4.5 and RCP8.5, respectively, maize yield in temperate and cold climates (all sites except Sarepol Zahab) under RCP4.5 and RCP8.5 scenarios will be decreased by -3.8% and - 6.5%, respectively. In Sarepol Zahab, the changes in air temperature and CO2 concentration increased maize yield by 11% and 21.7% in RCP4.5 and RCP8.5, respectively. Two factors influenced by climate change, namely growing season length and number of days with Tmax (maximum air temperature) >= 36 degrees C will play important roles in changing crop yield in the future. The results also showed that changing the sowing date along with increased CO2 concentration could reduce the adverse effects of climate change on maize by 15.6% across all sites, seasons, and scenarios. In fact, in all sites except Sarepol Zahab and Kangavar, sowing on the earliest possible date (April 3) helped the crop avoid encountering temperatures above 36 degrees C during the flowering period. In contrast, in Sarepol Zahab and Kangavar, as the hottest and coldest sites, respectively, delaying the sowing date (May 19 and June 4, respectively) could provide better conditions for crop growth. Overall, the findings of the current study showed that along with breeding activities, policy makers and extension agents of the agricultural sector can help farmers reduce the adverse effects of climate change on grain maize by compiling the cropping calendar and choosing the appropriate sowing date based on future climatic conditions.