The impact of black soil degradation on saturated hydraulic conductivity

Abstract Severe soil degradation represents a critical threat to agricultural productivity and ecological sustainability in the black soil region of Northeast China. Prolonged anthropogenic cultivation has induced varying degrees of degradation, markedly impairing soil hydraulic properties—particularly saturated hydraulic conductivity ( K sat ). As K sat is governed by multiple interrelated pedological processes, its temporal dynamics under long‐term cultivation remain poorly understood, especially with respect to the relative influence of key controlling factors across degradation stages. This study investigates how cultivation history and progressive soil degradation jointly regulate K sat in black soils of Northeast China. Results indicate that soil organic matter (SOM) declines exponentially with cultivation duration, approaching a carbon equilibrium state after approximately 150 years of continuous farming. Across degradation gradients, K sat exhibits a nonlinear, unimodal response to both the soil structural stability index (SSI) and SOM—initially increasing and subsequently declining. Crucially, the dominant control on K sat shifts from nutrient‐related properties (e.g., SOM content) during early degradation to structural and textural attributes (e.g., aggregate stability, clay dispersion, and pore continuity) under severe degradation. Separate regression models were developed for mildly and severely degraded soils to quantify these divergent controls. Collectively, these findings elucidate the dynamic hydrological mechanisms underlying soil degradation and offer a robust scientific foundation for improving hydrological modeling, land‐use planning, and targeted soil conservation strategies in the black soil region.