Conservation Buffers to Reduce Pesticide Losses

Conservation buffers can be used in a systems approach to help manage soils, water, nutrients, and pesticides for sustainable agricultural production which minimizes environmental impact. Buffers have long been a staple in conservation systems designed to prevent erosion and trap sediment and nutrients from field runoff. They also provide other benefits such as wildlife habitat improvement, streambank protection, and farming safety. Many studies have been conducted to document these benefits and to provide guidance in designing buffers for these purposes. But do buffers work to reduce pesticide losses?

Rainfall or irrigation can cause pesticides to run off the surface of treated fields. Edge-of-field losses can range from less than one percent of the amount applied to as much as ten percent (Wauchope, 1978). Losses are greatest when severe rainstorms occur soon after pesticide application. Edge-of-field concentrations of pesticides in surface runoff can range from less than 1 part per billion (ppb) to 1 part per million (ppm) or more.

Until recently, few studies had been conducted to measure the effectiveness of buffers in trapping pesticides in runoff. Physical properties of pesticides affect their behavior and transport. Some pesticides are highly adsorbed to soil particles and are carried primarily adsorbed to eroded sediment. Trapping of these pesticides by buffers should be very similar to sediment trapping. However, some pesticides are only moderately adsorbed to soil particles, and are carried off fields primarily dissolved in water. In order for buffers to be effective in trapping this type of pesticide, either water infiltration into the buffer must occur, carrying the chemical into the soil, or chemical must be removed from solution flowing over the soil surface by contact with soil or vegetation. Most studies indicate that an increase in water infiltration is the most important factor in trapping these pesticides.

This booklet will examine current knowledge of how conservation buffers can be most effectively used to reduce pesticide losses to water. Studies specifically measuring pesticide trapping by buffers will be reported, as well as relevant studies on effectiveness of buffers in trapping sediment and increasing water infiltration. The effectiveness of buffers in reducing pesticide losses will depend on the properties of the specific pesticide, the design and maintenance of the buffer, and local climate, weather, and soil conditions. When combined with specific local input from sources such as the National Resource Conservation Service (NRCS), this booklet will provide guidance to those providing advice and assistance to farmers and landowners installing conservation buffers. Other Best Management Practices which improve management and reduce losses of pesticides and can be used in combination with buffers will also be discussed.