Research on the Coupling Effect of Water and Fertilizer on Maize under Multi-Objective Conditions and Its Application Scenarios

It is of great significance to establish maize water and fertilizer application schemes under multi-objective conditions to improve water- and fertilizer-use efficiency, reduce agricultural greenhouse gas emissions, and promote sustainable agricultural developments. This study aims to analyze the effects of different water and fertilizer combinations on the summer maize yield, water-use efficiency, and field N2O flux and to determine the optimal water and fertilizer application scheme for summer maize. Field experiments were conducted in 2023, with a total of 15 different combinations of upper and lower limits of irrigation and fertilizer levels. A binary quadratic regression model based on the yield, water-use efficiency, and N2O emission flux was constructed. The fast non-dominated sorting genetic algorithm III (NSGA-III) was employed for verification and solution finding to simulate the optimal water and fertilizer regime. The results indicate that with increasing water and fertilizer applications, the field N2O emission flux gradually increases. The summer maize yield and water-use efficiency show a trend of initially increasing and then decreasing. Compared to fertilization, irrigation has a more significant impact on the summer maize yield and water-use efficiency, while fertilization notably influences the field N2O emission flux to a greater extent. Using NSGA-III, the simulated optimal water and fertilizer combination showed no significant difference in the yield and water-use efficiency compared to the actual optimal water–fertilizer irrigation combination (moderate water and moderate fertilizer), with a 3.12% increase in the field N2O emission flux, a 15.30% decrease in the irrigation amount, and an 11.90% reduction in the fertilizer application. In conclusion, employing the optimized water and fertilizer combination can reduce agricultural irrigation and fertilization while ensuring crop yields, providing theoretical support for the green, efficient, and sustainable development of the summer maize industry.