A PRECISION LANDSCAPE PLANNING APPROACH FOR CONTROLLING AGRICULTURAL NONPOINT SOURCE POLLUTION

摘要

Conservation buffers have substantial environmental benefits in reducing agricultural nonpoint source pollution and enhancing stream habitats. Reducing adverse environmental impacts of agriculture, such as nonpoint source pollution, has become a highpriority. The National Conservation Buffer Initiative, led by the Natural Resources Conservation Service of the U.S. Department of Agriculture, has a goal of installing 3.22 million kilometers (2 million miles) of buffers by 2002. Conservation buffers are frequently installed along streams and/or edges of agricultural fields. This paper suggests that conservation buffers should be incorporated in crop fields based on landscape characteristics. Specifically, conservation buffers should be placed in variable source areas (VSAs) where surface runoff is generated and accumulated during storm events. Optimal landscape placement of VSAs varies with topographic, soil and land use conditions, and intensity of storm events. Installing conservation buffers in VSAs allows agricultural runoff to enter buffers more uniformly and to be retained for a longer period of time, which increases removal of sediments and nutrients from runoff. A cost-benefit analysis of two conservation buffer alternatives in a small representative agricultural watershed in Missouri indicates that placing conservation buffers in VSAs within a field is more cost-effective than placing them along the edge of the field. In addition, sediment is reduced by 25 to 35 percent, nitrate, phosphorus and atrazine in runoff by 15 percent and nitrogen and phosphorus losses in sediment by 14 to 29 percent.