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 decreased in the order of decreasing acidity of the saturating cations. The H-organic matter was more active in triclopyr adsorption than Ca-organic matter and Ca-clay, whereas studies on mixtures of clay and organic matter indicated that the interaction between these two soil components reduced the surfaces available for triclopyr adsorption. Adsorption isotherms conformed to the Freundlich equation. It was found that in soil the Freundlich adsorption constant decreased linearly with organic matter (r = 0.930) and adsorption decreased with increasing pH. Multiple-regression analysis indicated that k(f) values were better correlated if cation-exchange capacity and pH (r = 0.989) were simultaneously taken into account.