Real-time water-nitrogen co-regulation improves winter wheat productivity: Insights from field experiments and HYDRUS-3D modeling

Efficient water and nitrogen management is essential for improving winter wheat productivity and resource-use efficiency in irrigated agroecosystems. However, the three-dimensional redistribution of soil water, heat, and nitrogen under real-time water-nitrogen co-regulation remains insufficiently quantified. This study integrated field experiments with HYDRUS-3D modeling to investigate root-zone soil water, temperature, and nitrogen dynamics under different irrigation and nitrogen regimes in the North Henan Plain, China. Soil moisture, temperature, and nitrogen observations were used to calibrate and validate the model, and an integrated evaluation framework based on the Analytic Hierarchy Process was used to identify the optimal management strategy. The HYDRUS-3D model accurately reproduced soil moisture, temperature, and nitrogen transport across treatments, with coefficients of determination generally greater than 0.70, confirming its suitability for characterizing three-dimensional soil water-heat-nitrogen transport under drip fertigation. Water and nitrogen showed clear spatial heterogeneity in the root zone, with depletion mainly occurring in the 20–40 cm root-active layer and nitrogen accumulation in the 40–60 cm layer. The moderate water-nitrogen treatment W2N2 improved root-zone conditions by increasing soil moisture in the 0–60 cm profile, reducing daily soil temperature fluctuations, and enhancing nitrogen retention, and was identified as the optimal regulation strategy. Compared with the conventional control, W2N2 increased grain yield, water use efficiency, and partial factor productivity of applied nitrogen by 6.76%, 36.02%, and 74.12%, respectively. These findings indicate that coupling real-time monitoring with process-based modeling can support precision water-nitrogen management and improve productivity and resource-use efficiency in winter wheat production.