Dissipation of Dicamba, Picloram, and 2,3,6-TBA Across Nebraska

The dissipation and detoxification of 3,6-dichloro-o-anisic acid (dicamba), 4-amino-3,5,6-trichloropicolinic acid (picloram), and 2,3,6-trichlorobenzoic acid (2,3,6-TBA) was followed for 6 years at three locations across Nebraska. Herbicide persistence was determined by growing field bioassays of field beans (Phaseolus vulgaris L.) and soybeans [Glycine max (L.) Merr.]. Picloram showed the greatest soil persistence, 2,3,6-TBA was intermediate, and dicamba showed the least persistence across Nebraska. The residual phytotoxicity of picloram in soil was not necessarily dependent upon rainfall but was greatest in the fine textured soil with higher organic matter content.