Spatial Variability of Soil Erodibility at the Field Scale.

Soil erodibility is a key factor affecting soil erosion process. Different topographic positions on the landscape may have different surface and subsurface hydrology resulting in different localized soil condition and properties. In order to better assess soil erosion at the landscape, knowledge on the variability of soil erodibility within the same field (topographic effect) is necessary to provide scientific basis for soil erosion prediction. Two soils collected from the shoulder and toe slope positions are studied and compared. The main experimental methods including rainfall simulation and mini flume experiments are used to derive process-based erodibility parameters, i.e., Ki, Kr and Tau-C. The USLE-K factor is back calculated from the Water Erosion Prediction Project (WEPP) model and the WEPP derived USLE-K is compared with the value in current NRCS database. By using fluidized bed technique and a sand abrader, soil cohesion and dry crust strength can be measured. Within the same field, different topographic locations may have impacts on the physicochemical properties of the soil (soil particle composition, organic matter content, etc.), causing the variability in soil strength, hence soil erodibility.