Unsustainable agricultural land use will lead to an increased risk of soil erosion and soil degradation. However, few studies have investigated impacts of changes in root and soil properties on the soil detachment process. Therefore, we investigated the effects of agricultural land use on the relative contribution of root and soil properties to soil detachment capacity. Soil samples were collected from six different land use types and subjected to flow scouring under six shear stresses ranging from 4.98 to 16.37 Pa. Agricultural land use influenced root distribution and soil properties in the soil surface layer. Root length density, root surface area density, and root volume density in orchards with no cover, orchards with grass cover, and farmland were less than those of grassland samples. Different land use types affected soil detachment capacity. Bare land, farmland, and orchards with no cover were more vulnerable to erosion, while forest, orchard with grass cover, and grassland showed little soil detachment. Soil detachment capacity decreased exponentially with increasing soil bulk density, aggregate stability, organic matter, and root mass density. The root mass density and aggregate stability had the greatest contribution to the soil detachment capacity. Agricultural land use increases the risk of soil erosion; a groundcover management strategy, such as planting grass in orchard, could effectively increase the fine root distribution and aggregate stability to control soil erosion.

Slope farmland is prone to soil erosion, especially in sub/tropical regions. However, our understanding of near-surface hydrology characteristics and their controlled factors in red soil sloping farmland remains limited. Here, we conducted simulated rainfall experiments to assess the impact of rainfall pattern, straw mulching, and soil structure on near-surface hydrological processes of red soil sloping farmland of southern China. Results showed that: (1) short duration-high intensity rain caused greater surface runoff and sediment production than did long duration-low intensity rain, whereas the variation pattern of subsurface flow exhibited the opposite trend; (2) tillage behavior could weaken the surface runoff intensity and promote the development of subsurface flow; (3) straw mulching increased the water infiltration rate and associated subsurface flow production (increased by 1.33~12.71 times), and thus reduced the surface runoff production (reduced by 99.68~100%). These findings highlight the crucial roles of rainfall pattern and straw mulching in regulating the spatial distribution pattern of rainwater and suggest that straw mulching can effectively reduce soil erosion via accelerating water infiltration and subsurface flow form in slope farmland of soil erosion in southern China.