Soil Degradation and Its Response to Human Activities in Subtropical High-Intensity Agricultural Systems

Intensive agriculture-driven soil degradation has become a global environmental challenge, urgently requiring governance strategies that integrate farmer behavior with policy intervention to support sustainable development. In this study, matched soil experimental data and household survey responses were used to assess the status and degradation characteristics of key soil nutrient indicators, including soil pH, total nitrogen, ammonium nitrogen, nitrate nitrogen, available phosphorus, quick-acting potassium, organic carbon, and the C/N ratio. The effects of policy measures and farmers’ behavioral practices on both individual soil nutrient indicators and the overall degree of soil degradation were empirically examined. Across 178 plots with an average management duration of 17.93 years, widespread soil acidification (mean pH = 4.535), nitrogen saturation effects, and other nutrient imbalances were identified. The application of restoration technologies was found to significantly reduce soil degradation, although the magnitude of improvement varied by nutrient type. Technical training and farmland transfer policies indirectly mitigated soil degradation by promoting the adoption of restorative practices. Furthermore, combinations of policy instruments demonstrated synergistic effects, compensating for the limitations of single-policy approaches. These findings highlight the need for policy frameworks that incorporate degradation-based targeted guidance, restoration subsidies, and standardized farmland transfer mechanisms. The study deepens understanding of the micro-level mechanisms linking farmer behavior with soil ecological processes and provides empirical evidence supporting progress toward the United Nations Sustainable Development Goal of achieving zero net land degradation.