Varietal adaptations matter for agricultural water use - a simulation study on grain maize in Western Switzerland

Climate change is altering agricultural production conditions. Adaptation measures to reduce negative impacts of climate change and utilize emerging potentials may involve the increased use of irrigation water. With increased irrigation water consumption, water use conflicts and resource constraints may occur and aggravate under climate change. Estimates of expected changes in irrigation water demands are of great value to anticipate if and where such issues may arise. This study presents an analysis of projected changes in irrigation water demand and grain yield of maize subject to variation in cultivar choice, sowing dates, soil depth and texture, as well as climate projection uncertainty and crop model parameterization uncertainty. Study results suggest that varietal choice opens up a large scope for adaptation of future grain maize productivity with important implications for agricultural water use. Assuming that no mitigation measures are taken (RCP8.5), the cultivation of late-maturing varieties in combination with earlier sowing can be considered a suitable adaptation choice, even allowing for increasing yield levels until mid-century. However, with this adaptation choice, irrigation water demands could be expected to increase by up to 40% until the end of the century. While absolute estimates of irrigation water demands are strongly dependent on soil depth (and to a much smaller degree on soil texture), change signals of irrigation water demands were largely unaffected by variation in soil parameters. However, estimates of future changes in irrigation water demands are subject to large uncertainties originating from climate projection uncertainties, implying possible increases in irrigation water demands between < 10% and > 60%. Increases in irrigation water demands could be constrained by cultivating early-maturing varieties at the expense of lower production potentials. Selection and breeding efforts steered towards early varieties with extended grain filling duration may help to increase yield potentials.