Impacts of optimized irrigation and diversified crop rotations on groundwater sustainability and productivity in the North China Plain

The conventional winter wheat-summer maize rotation system (WM) achieves high crop yields with persistent groundwater table depletion in the North China Plain (NCP). The joint impact of optimized irrigation and cropping systems adjustments on water-groundwater dynamics in WM rotation remains poorly understood. This study aimed to evaluated the efficacy of integrating optimized irrigation with legume-based rotations in reducing water use, enhancing productivity, and mitigating groundwater depletion in the NCP. Hydrological processes and crop growth (2004–2024) were simulated using the soil-water-atmosphere-plant (SWAP) model to compare conventional WM (three irrigation regimes) with P-WM and S-WM rotations. System performance was evaluated across hydrologic, agronomic, nutritional and economic indicators, with Entropy-TOPSIS identifying the optimal strategy. Compared to the conventional WM scenario, the legume-based rotations (P-WM and S-WM) demonstrated superior hydrological performance, significantly reduced system ETa by 26.6–27.4% and mitigated groundwater level decline by approximately 1.14 m and 1.13 m per year, respectively. The P-WM was the superior scenario, increasing equivalent water productivity and economic output by 20.3% and 72.1%, respectively, while reducing the water footprint by 17.0%. Both diversified rotations enhanced the efficiency of water use relative to yield productivity, protein and economic outputs. The comprehensive evaluation identified P-WM rotation as the optimal system for balancing productivity and groundwater sustainability. Our results indicate that integrating legume-based rotations with optimized irrigation effectively promotes sustainable agriculture in the NCP. This synergy mitigates groundwater depletion while securing economic and nutritional outputs, providing a scalable model for other water-scarce regions.