摘要：The Chesapeake Bay is a major water resource whose quality has been threatened by soil erosion and agrichemical contamination. The control of agricultural pollution of the Bay is one of the focal points of the 1987 Chesapeake Bay agreement formed by four states in the Bay's watershed (Virginia, Maryland, Pennsylvania, and the District of Columbia). Among the suggested solutions is the promotion of low-input agricultural practices. However, some low-input practices also include frequent cultivations of the soil for non-chemical weed control practices, which may induce erosion. This analysis uses a case study approach to determine agricultural practice selection and potential erosion under different soil erosion constraints. A multi-period mathematical programming model was used to determine the preferred agricultural practices for a fanner maximizing net returns in Richmond County, Virginia. Richmond County is adjacent to the Rappahanock River and above the Columbia aquifer, major sources of fresh water for the Chesapeake Bay. A range of agricultural practices was available, including conventional and organic practices. Soil erosion and the level of chemical and nitrogen losses through sedimentation and leaching are discussed in this article. Soil erosion constraints were introduced that reduced erosion by 10, 20, 30, 40, and 50 percent from current levels. These constraints were met without idled cropland, besides that enrolled in the Conservation Reserve Program or Virginia's mandatory Buffer Strip Program. The results of this study illustrate that soil conservation policies and low-input practices produce few environmental tradeoffs between erosion control and the reduction of agrichemical pollution.
