by L.D. Olsen
This report is available as a pdf below
In 1989, the U.S. Geological Survey began a long-term project to evaluate the effectiveness of agricultural best management practices (BMP's) on controlling soil erosion and improving water quality in the Beaver Creek watershed in West Tennessee. The Beaver Creek watershed consists of about 95,000 acres and includes some of the Nation's most productive farmland and most highly erodible soils. Resource-management agencies in this locality have recommended conservation tillage or "no-tillage" as a BMP to control soil erosion.
Unlike conventional tillage, in which the top 1 foot of soil is turned over by a moldboard plow before planting, no-tillage preserves the natural structure of the soil and retains the crop residues from the previous growing season . No-tillage reduces soil erosion and run off by slowing the flow of rainwater from the field. However, by preserving the macroporosity of the soil (by not tilling up old root channels and earthworm pathways), no-tillage has been found in some cases to accelerate chemical movement through the soil, increasing the potential for groundwater contamination (Dick and others, 1989; Hall and others, 1989; Isensee and others,1990).
The risk of ground-water contamination associated with the implementation of no-tillage needs to be addressed. Because the relation between no-tillage and chemical movement depends upon the climate and soils of a specific region, a field-level study was conducted to compare pesticide behavior in no-tilled and conventionally tilled soils in West Tennessee.
In 1993, the U.S. Geological Survey, in cooperation with the Tennessee Department of Agriculture, initiated an investigation of pesticide movement and degradation in soils. This fact sheet summarizes the goals of the study, the methods used, and the results of the pesticide analyses of the soil samples taken during the 1993 growing season. Additional details of this investigation are presented in Olsen and others, 1994.
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