Modeling nitrogen leaching in a spring maize system under changing climate and genotype scenarios in arid Inner Mongolia, China

Although the impacts of climate change on crop yield and production in China have been studied, the potential impacts on nitrate leaching are less well-known. In this study, we considered how climate change and crop genotypes with different N uptake capacities could affect soil water drainage, nitrate leaching, and grain yield under currently optimized irrigation and fertilization practices in the spring maize system of northwest China. After testing the performance of the WHCNS (soil Water Heat Carbon Nitrogen Simulator) model, a total number of 420 simulations spanning representative climate projections (2036-2065), genotypes, and time spans led to three key findings. First, the projected climate changes had no significant effects on soil water drainage and thus no impact on nitrate leaching, because the latter was primarily influenced by drainage. Second, the effects of genotype changes on reducing nitrate leaching via increasing N uptake were marginal over the whole growth period, again because these had no significant effect on soil water drainage. Finally, the projected yield reduction (around 6.5%) occurred only in the hottest climate scenario (RCP8.5), in which transpiration was probably a more significant parameter leading to yield differences between climates. We conclude that, to offset the projected yield reduction due to temperature increases, improved agricultural technologies and practices will be needed to cope with decreased crop transpiration. In addition, reducing nitrate leaching through genetic improvement of N uptake should not be considered a research priority for mitigating the effects of current and projected climate scenarios.