Improving yield, quality, and environmental co-benefits through optimized irrigation and nitrogen management of hybrid maize in Northwest China

Seed yield (SY) of hybrid maize tends to be emphasized over seed quality, which collectively determine maize planting and production. The maize seed production in the Hexi Corridor supports more than half of China's maize cultivation, but the shortage of water resources and inefficient agricultural resource use limit high-yield, high-quality, and high-efficient production of hybrid maize. In this study, the Jensen- and Rao-based models were developed for SY and seed vigor (SV) of hybrid maize based on data collected from multi-year field experiments, and found that the heading and filling stages were sensitive to water and nitrogen (N) for SY, and jointing and filling for SV. Building on these insights, a framework was developed to optimize irrigation and N fertilization management under different hydrological years, considering interactive sensitivity coefficients of water and N at different growth stages, precipitation, and initial soil available water and N content. Results showed that the optimized irrigation (22.6-37.8%) and N fertilization inputs (34.1-53.2%) and N-surplus (35.3-60.6%) were significantly decreased and irrigation water productivity (WPI) and partial factor productivity from applied N fertilization (PFPN) were significantly increased compared with the current scenario, regardless of whether SV maximization is set in the optimization framework. The optimized scenario that maximizes both SY and SV objectives requires 0.6-8.8% more water and N inputs than the scenario considering only the maximized SY objective in wet, normal, and dry years. The best optimization scenario evaluated by using the osculating value method considering SY and SV, WPI, PFPN, and N-surplus varied between different hydrological years. Our optimization framework and findings would guide high-yield, high-quality and highresource use efficient production of hybrid maize, with low risk of agricultural N pollution in the Hexi Corridor, and has the potential for further use for optimizing irrigation and fertilization management of other crops.