Abstract

Soil surveys can be used to group soils according to taxonomic classification and potential for pesticide transport, but estimation of pesticide mobility may be limited by inclusions of dissimilar soils within map units. Estimation of pesticide mobility may also be affected by the level of detail of soil maps as dictated by the needs and purposes of the soil survey. The objective of this research was to determine the most appropriate level of soil map detail for predicting pesticide mobility in terrace soils. Soil cores were collected on river terrace landscape positions in southwestern, south-central, and southeastern Nebraska. Soil thin-layer chromotography was used to measure the relative mobility (Rf) of benchmark pesticides (alachlor, atrazine, carbofuran, and dicamba) in samples from each core. Composite Rf values were calculated for each soil pedon to compare pesticide mobility among map units and sample areas. Mobility was affected more by pesticide solubility and Koc, and by the general physical and chemical properties of parent materials at the sample sites, than by specific soil type. The research suggests that soil association maps, comprised of map units that are groupings of soil series associated geographically in a repeating pattern, may be the most appropriate for predicting pesticide mobility in terrace soils.