6SHEA O L. An economic approach to reducing water pollution:point and diffuse sources [ J ]. The Science of the Total Environment,2002,282/283 : 49 -63.
7PARRY R. Agricultural phosphorus and water quality:A U. S. environmental protection agency perspective [ J ]. J of Environ Qual, 1998,27 : 258 - 261.
8DENNIS L C,PETER J V,KEITH L. Modeling non-point source pollution in vadose zone with GIS [ J ]. Environmental Science and Technology, 1997,8:2157 - 2175.
9BOERS P C M. Nutrient emissions from agriculture in the netherlands: Causes and Remedies[ J ]. Water Science and Technology, 1996,33 : 183.
10NOVOTNY V, OLEM H. Water quality: prevention, identification and management of diffuse pollution [ M ]. New York : Van Nonstandard Reinhold Company ,1993.
