Previous and ongoing research clearly indicates that P& N losses in agricultural runoff is one source of nonpoint pollution of surface waters, especially P is the limiting elements of inland surface water. The concentration of P in runoff was related to the content of P in the surface layer of soil. Movement of P through soil into groundwater has generally been considered to be insignificant because P is fixed firmly by soil colloids or organic matter. However, evidence is now accumulating that small but si...