Soil profile properties in relation to soil redistribution by intense tillage on a steep hillslope
Little is known about soil redistribution by tillage and its impact on the properties of soil profiles with thin soil layers on hillslopes. In this study, consecutive tillage by hoeing was performed 5 and 15 times on an Orthic Regosol within a steep hillslope landscape of the Sichuan Basin, China, to simulate the impact of short- and long-term tillage on soil profile properties at different slope positions. After intense tillage, significant changes in 137Cs inventories of the soil occurred in the summit and toeslope positions. The soil profile (originally 0.3 m in depth) disappeared on the slope summit due to intense soil downslope translocation, and the soil profile was truncated in upper slope positions in the proximity of the summit, while a thickened soil profile was present in toeslope positions, where the original soil profile was buried. The summit was characterized by an exposure of bedrock corresponding to areas of 4.77 and 10.0% of the experimental plot for 5 and 15 tillage operations, respectively. Soil organic C (SOC) and P were completely depleted with the disappearance of soil profiles at the summit position, while a substantial increase in SOC and extractable P inventories of the post-tillage soil profile was found in the toeslope position. Intense tillage caused remarkable soil redistribution within the landscape of the steep slope, resulting in net soil loss and gain close to the upslope and downslope boundaries of the field, respectively. Tillage results in an intense transformation of soil profiles and the variation in soil properties in steeply sloping fields.