Antagonistic Effects Between Picloram and Bromacil with Oats

Abstract

Combinations of 4-amino-3,5,6-trichloropicolinic acid (picloram) and 5-bromo-3-sec-butyl-6-methyluracil (bromacil) pellets applied to the soil gave antagonistic responses on oats(Avena sativaL. ‘Clintland 64′) with either 5.6 plus 11.2 kg/ha or 11.2 plus 11.2 kg/ha of picloram plus bromacil. In nutrient culture a significant antagonistic response occurred over a 15-day period with a picloram to bromacil ratio of 30 to 1. Of the ratios evaluated, picloram appeared to interfere with the phytotoxic effect of bromacil. The uptake of14C-bromacil alone by oats from nutrient solution was nearly double that of14C-bromacil when combined with picloram. Thin layer chromatographic analyses revealed that 47% of the14C activity from bromacil in the oat was intact bromacil and that 70% of the labeled activity from picloram was unaltered picloram. The loss of nutrient solution by evapotranspiration was less from containers with picloram and bromacil than from those with bromacil alone. Picloramtreated roots were shorter than untreated or bromacil-treated roots.