Reliability of soil erodibility estimation in areas outside the US: a comparison of erodibility for main agricultural soils in the US and China

Soil erodibility (K), which has important influences on the accuracy of soil loss prediction, is a critical factor in the universal soil loss equation (USLE) and the models modified from it. As an effective tool to estimate soil loss, USLE has been widely applied in the US and around the world. Since the 1980s, the USLE framework for soil erosion prediction and assessment has been adopted in China. During its application in China, it has been noticed that the K values appear to be considerably lower than those in the US. This fact means that the estimated values of soil erodibility from existing methods, such as the nomograph-based database in the US, might be unreliable for their application in China and other areas. In this study, the K values for the main agricultural soils in China with those in the US were systematically compared based on the database from field runoff plots. Possible reasons for the differences were analyzed, and the reliability of soil erodibility estimation in areas outside the US was assessed. Results show that the average K factor for soils in the US is two to three times greater than that in China. For two typical stations with similar soil types located in the US and China, soil loss per rainfall erosivity is higher in the US than in China, although erosivity for the given rainfall in the US is sometimes smaller than that in China. There might be a great bias in soil loss prediction in China if the K value formulas derived from the database of the United States are used directly. This implies that the erodibility estimation formula currently used in the USLE model may need to be verified and revised.