Field Testing Pesticide Transport Models at a Cooperative Test Site Near Plains, Georgia

Abstract

Leaching of pesticides is a potential problem in the major agricultural production areas of southern Georgia where sandy soils are predominant. Compounds used on crops such as peanuts, corn, and soybeans are of particular interest because of their potential to leach under certain conditions. Several models that simulate transport and transformation of pesticides in the environment have been developed; these include: RUSTIC (Dean et al., 1989), GLEAMS (Leonard, et al., 1987), AGG (Fong and Mulkey, 1990), and LEACHM (Wagenet and Hutson, 1989). These or other models can be useful for making management decisions pertaining to chemical use. Effective use of such models is dependent on how well these models perform in field situations. Field data are necessary for evaluating factors that affect the leaching process. Such data are required for testing model predictive capability. A field study to provide a database for model testing was initiated in 1988 at a site near Plains, GA. The study site is in the Fall Line Hills district of the Coastal Plain province. The Claiborne aquifer recharge area is located in this district. The U.S. Environmental Protection Agency, the U.S. Department of Agriculture, the U.S. Geological Survey, and the University of Georgia Agricultural Experiment Station developed a joint research effort to investigate and to model pesticide movement at the Plains site. The study was planned for 5 years duration, beginning with the 1989 cropping season. As early as 1986, the USDA and USGS were involved in characterization studies at this site. The participants are sharing technical expertise and resources to develop a better understanding of physical, chemical, and biological processes that affect leaching, to evaluate spatial and temporal variability, and to develop and test linked models for chemical transport and transformation. One product of this cooperative research effort will be a comprehensive database that should be useful for testing such models. The study design is amenable to implementing the testing methodology proposed by Parrish and Smith (1990), as well as other techniques. This paper describes the field design and presents preliminary pesticide leaching results obtained for the first year of the study.