Movement and Persistence of Picloram in Pasture Soils of Nebraska

Abstract

More 4-amino-3,5,6-trichloropicolinic acid (picloram) was detected in soil samples by soybean ( Glycine max (L.) Merr., var. Ford) bioassay when the herbicide was applied in the fall than when it was applied in the spring to several pasture types. Downward movement was greater in sandy loam than in silty clay loam. Dissipation of picloram was greatest in the upper 12 inches regardless of soil type. More picloram was detected in the 24 to 36-inch depth from plots treated 1, 2, or 3 years before sampling than in plots sampled the year of treatment. This indicated downward movement into the subsoil.