THE PRESENT SITUATION AND SOME THOUGHTS OF SOIL LOSS TOLERANCE STUDY

As the criterion of judging non-erosion and erosion area,the value of soil loss tolerance(T-value) must be determined scientifically and rationally.To assign a T-value soil formation rate,relationship between soil loss and productivity and gully prevention must be considered.Current methods of evaluating the soil loss tolerance mainly include: ①soil profile thickness;②the geochemistry cycle theory;③nutrient balance;and ④ according to erosion model.The international existing T-value standards are mainly established according to the soil profile thickness and soil formation rate.The history and the main content of soil loss tolerance study are reviewed in this paper,and the method of using Barth equation and on the basis of the risk assessment are also introduced.In face of the existing problems in the evaluation method and conclusion of T-value research,future T-value study should be concentrated on the characteristic of soil formation(natural attribute),the durative of rational productivity level(social attribute) and the soil and water environment safety(social and natural attribute)is raised.