Screening Procedure for Soils and Pesticides for Potential Water Quality Impacts

Abstract

A screening procedure has been developed to evaluate the relative loss of pesticides from soils, to assist the Soil Conservation Service in implementing water quality for conservation planning. This screening procedure is a first-tier evaluation of the impact of using a particular pesticide on a specified soil. The screening procedure was developed from evaluating pesticide loss from over 40 thousand runs of the GLEAMS (Groundwater Loading Efects of Agricultural Management Systems) model. The model input data were a combination of soils and pesticides with a wide range of properties. The estimated pesticide losses were categorized into losses by leaching, losses adsorbed on sediment in runoff, and losses in the solution phase of runoff. Algorithms using soil properties were developed to rate soils into four loss potential classes for leaching and three loss potential classes for the two categories of runoff. Also, algorithms using pesticide properties were developed to rate pesticides into four loss potential classes for leaching and three loss potential classes for runoff. The soil and pesticide groupings are combined in a matrix to give an overall loss potential rating. Statistics of the overall loss potential indicate the low loss potential class is pure, that is, it does not contain occurrences that have medium or high losses. The medium loss potential classes does not contain occurrences of high loss, but does contain many occurrences of low loss. The high loss potential class contains incidences of medium and low loss.