Evaluation of Summer Maize Water and Nitrogen Management Strategies Across Different Hydrological Years Using the DSSAT Model

Summer maize (Zea mays L.) production on the North China Plain is highly dependent on variable seasonal rainfall, which increases the likelihood that inappropriate water and nitrogen allocation will cause yield fluctuations and ecological and environmental risks. Previous studies have mainly relied on single-site field comparisons or basic statistical evaluation methods, limiting the understanding of the dynamic response mechanisms of drought stress coupled with nitrogen application during the jointing and grain-filling stages. Based on field experiments conducted in 2024–2025, the DSSAT model was used to simulate aboveground dry matter accumulation (CWAM), grain yield, leaf area index (LAI), dry matter evapotranspiration productivity (DMPEM), and dry matter nitrogen productivity (DPNAM) of summer maize under different water–nitrogen treatments at different growth stages. Then, historical meteorological data for Henan Province from 2003 to 2023 were imported. The years were classified into three hydrological year types: wet years, normal years, and dry years. Subsequently, Principal Component Analysis (PCA), the TOPSIS method, and the Rank-Sum Ratio (RSR) method were employed to construct a multidimensional evaluation system for assessing water and nitrogen management strategies under different hydrological year types. The results showed that the nitrogen application rate had a significant regulatory effect on yield, DPNAM, and DMPEM. All three initially increased and then decreased as the nitrogen application rate rose, with the optimal performance observed under the normal nitrogen (N2) treatment. Under drought conditions during the same growth stage, the increase in the maximum yield under the N2 treatment was approximately 8.1% and 50% higher than that under the high-nitrogen (N1) and low-nitrogen (N3) treatments, respectively. Compared with drought during the grain-filling stage, drought during the jointing stage had a smaller negative effect on CWAM and LAI. A comprehensive evaluation with long-term meteorological data reflects that drought during the jointing stage combined with normal nitrogen (Q2) is the optimal water–nitrogen management strategy for wet years (with an RSR value of 0.994). The treatments of drought during the jointing stage combined with high nitrogen (Q1) and drought during the grain-filling stage combined with normal nitrogen (H2) reveal greater adaptability and favorable universality across different hydrological year types. The model’s reliability under various water–nitrogen coupling conditions was validated by integrating field experiments, DSSAT model simulations, and a multidimensional evaluation system. This study lays a scientific theoretical foundation for achieving high and stable yields in summer maize under different water–nitrogen coupling conditions and across various hydrological year scenarios.