ADSORPTION OF TRICLOPYR ON SOIL AND SOME OF ITS COMPONENTS

The adsorption of triclopyr [[(3,5,6-trichloro-2-pyridynyl)oxy] acetic acid] by homoionic clays, soil organic matter (H- and Ca-saturated), and seven soils was studied. The extent of adsorption on clays decreas ed in the order of decreasing acidity of the saturating cations. The H -organic matter was more active in triclopyr adsorption than Ca-organi c matter and Ca-clay, whereas studies on mixtures of clay and organic matter indicated that the interaction between these two soil component s reduced the surfaces available for triclopyr adsorption. Adsorption isotherms conformed to the Freundlich equation. It was found that in s oil the Freundlich adsorption constant decreased linearly with organic matter (r = 0.930) and adsorption decreased with increasing pH. Multi ple-regression analysis indicated that k(f) values were better correla ted if cation-exchange capacity and pH (r = 0.989) were simultaneously taken into account.