The favor able natural condition is advantageo us to various land use patterns in low mountains and hills of south Jiangsu province.And various ways of land uses have changed the properties of the soil.In general

the soil erosion and the nutrient loss of the cultivated soil that are disturbed by human are larger than that of the uncultivated soil in natural or half-natural condition.In order to know the quantity of nutrient loss caused by soil erosion

the soil erosion intensity should be decided.The tracer method by cesium-137 can be used to resolve two problems.One is to determine the backg round content of 137Cs.The other is to establish the model of soil erosion.After estimating the soil erosion rate of various ways of land uses

the quantity of soil nutrient loss is calculated.For the sake of indicating the potential risk of soil erosion

and comparing the danger of the loess with red soil area

the concept of the equal value soil erosion is put forward.It is preliminary found that cultivated soil

especially paddy

may be a primary agricultural source of nutrient elements of Taihu lake.