New pathways and the associated uncertainties for increasing maize water use efficiency under global warming

The DSSAT4.7-CERES model was employed to simulate plant-water nexus conditions in the future of Mazandaran province in Iran, using ensemble outputs of various GCMs and emission scenarios with LARS-WG 5.5 in the time period 2010-2100. The results showed during the 21st century, maize water requirement is expected to be reduced by 3.3-14.1%. Under climate change scenarios, both negative and positive changes in crop yield are projected, between -37.4% to 36.1%, which consequently results in a 5.1-27.2% reduction in water use efficiency (WUE) in the future periods. Deficit irrigation (DI) with 25% reduction in irrigation water depth (DI75) lead to a moderate reduction of 4.3-5.5% in WUE, but WUE was highly reduced under DI55. While early planting may reduce WUEs by 0.4-17%, late planting almost resulted in improved WUE, especially under DI75. Less frequent irrigation significantly reduces actual evapotranspiration, which consequently resulted in improved WUE by 0.57-42.47%. In conclusion, the integrated assessment reveals that DI75, with an irrigation interval of 5 days, together with a 20 days delay in cropping date of maize in Mazandaran province, may be considered as an effective adaptation solution, when considering both food and water security.