Abstract: Results of the sampling of representative soils in the Taihu Lake watershed between 1982 and 1999 show that decades of P fertilization at rates exceeding the removal rates by crops has resulted in widespread accumulation of P in agricultural soils. The increase in Total P and Olsen P is 0.1 g/kg on average and 4-5 mg/kg for most soils, respectively. Such a surplus has brought up the P level by a large margin in the soils of lands grown with cash crops, and the area of soils deficient in P has largely decreased. The increase in soil P, however, also enlarges the risk of P loss from soil to surface water. Soils differ from type to type in P adsorption capacity. Moreover, in this region, soils with low P adsorption capacity are often used to grow cash crops. As a result, excess P input increases the risk and the amount of soil P loss to water bodies.

Key words: phosphorus, soil, Taihu Lake, water environment quality, watershed