Enhancing inherent soil productivity increases maize yield and nitrogen use efficiency by improving soil water and nutrient status

Introduction: Soil management technologies centered on fertility enhancement are essential for achieving the synergistic improvement of crop yield and resource use efficiency. This study aims to identify key soil factors driving the coordinated increase in yield and nitrogen use efficiency of spring maize, thereby providing a scientific basis for promoting high yield and efficiency through improved soil quality. Methods: Based on variations in inherent soil productivity (ISP) across maize ecological regions in Inner Mongolia, China, this study established two soil management modes-Conventional Practices (CP) and Improved Soil Management Practices (IMSP)-to quantitatively identify key factors influencing ISP, yield and nitrogen use efficiency (NUE) through the random forest algorithm. The effects of soil fertility improvement on maize yield and nitrogen use efficiency were also examined. Results: Our results showed that soil organic matter and alkali-hydrolysable nitrogen were the major nutrient related drivers of ISP, maize yield, and NUE, whereas N mineralization, N losses, soil water content, and WUE dominated process-related regulation. Among these, soil organic matter was the core factor governing ISP. Soil organic matter content indirectly affects soil nitrogen mineralization and water conservation capacity, which is the core of regulating soil productivity. The core process of synergistic regulation of maize yield and NUE by fertility improvement mainly lies in two aspects: on the one hand, by expanding the storage capacity of soil water to meet the water demand of the maize population; on the other hand, by increasing the net mineralization of soil nitrogen (16.0%), reduce the apparent loss of nitrogen (11.4%), reduce the risk of nitrogen leaching, and make it have the best soil water and nitrogen environment, so as to achieve synergy between yield and NUE. The regulation effect of IMSP model and nitrogen-dense interaction on yield increase and efficiency is more significant. Discussion: Enhancing soil fertility through increased organic matter improves water storage and net nitrogen mineralization while reducing nitrogen loss. The IMSP model and nitrogen-dense interaction effectively regulate this process, creating an optimal soil environment to synergistically achieve high maize yield and improved nitrogen use efficiency.