Effects of Soil Erosion on the Tillage-Layer Quality and Limiting Factors of Sloping Farmland

Abstract

Soil erosion is the key factor leading to the degradation of tillage-layer quality, which directly threatens regional food and ecological security. To study the characteristics of soil structure, water retention capacity, and nutrient changes in the tillage layer of purple soil sloping farmland under different erosion conditions, a shovel soil erosion test was performed to distinguish the factors that hinder the tillage-layer quality of sloping farmland under different erosion degrees. The degradation of soil structure showed that with the intensification of erosion, soil bulk density, soil capillary porosity, and sand content displayed an overall increasing trend; the soil water retention degradation was expressed by the average increase in the soil water holding capacity and the average decrease in the infiltration rate; soil nutrient degradation was derived from the average decrease in soil nutrient content. At the initial stage of erosion, the soil nutrient degradation was extremely sensitive to soil erosion, which was the limiting factor of the tillage layer; when the erosion reached stage E-15 (erosion 15 cm), the soil nutrients, soil permeability, and soil capillary porosity became the limiting factors; for E-20 (erosion 20 cm), the limiting factors added an index on the basis of stage E-15, namely, soil total porosity. When soil erosion continued for 53 years, the tillage-layer quality index was lower than the threshold value (0.46). Reconstructing soil profile of the tillage layer is an effective way to break the limitations of the barrier factors and improve the tillage-layer quality.