Soil erodibility and its estimation for agricultural soils in China

Soil erodibility (the K factor in the Universal Soil Loss Equation, USLE) is an important index to measure soil susceptibility to water erosion, and an essential parameter needed for soil erosion prediction. To evaluate the appropriateness of the nomograph and other methods for estimating the K factor for the USLE and to develop a relationship for soil erodibility estimation for Chinese soils, a set of soil erodibility values was calculated using soil loss data from natural runoff plots at 13 sites in eastern China. The definition of soil erodibility in relation to the USLE was strictly followed. Comparing these measured values to those estimated using the nomograph method, the method adopted for the EPIC model and the formula of Shirazi and Boersma, we found that all these estimated soil erodibility values were considerably higher than the measured soil erodibility for these sites in eastern China. Soil erodibility for these Chinese sites is typically in the range from 0.007 to 0.02 t h (MJ mm)−1 and consistently lower in comparison to the measured K values from the USLE database for the conterminous United States. Strong linear relationship between the estimated and measured K values were used to develop empirical formulas for soil erodibility estimation from soil survey data for sites in eastern China.