Adsorption of Ametryne and Diuron by Soils

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Abstract
The adsorption of 2-(ethylamino)-4-(isopropylamino)-6-(methylthio)-s-triazine (ametryne) and 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron) varied greatly among 34 Puerto Rican soils was studied using the agitated slurry technique. Adsorption was expressed as a distribution coefficient (Kd), which is the ratio of the amount of herbicide adsorbed to the amount in the equilibrium solution. In general, diuron was adsorbed to a greater degree than ametryne. Adsorption of ametryne was positively correlated with organic matter and silt content but negatively correlated with pH of the soil. The inclusion of soil pH in a multiple regression analysis contributed the highest increase in explanation for adsorption of ametryne. Adsorption of diuron was highly correlated with organic matter content and cation exchange capacity. A correlation was found between adsorption of diuron and content of magnesium, and soil texture. Cation exchange capacity was the only inclusion soil property which, in addition to organic matter, significantly contributed to the adsorption of diuron. Temperature appeared to have a greater effect on the adsorption of diuron than on the adsorption of ametryne. Conversely, the effect of pH on the adsorption of ametryne was significantly greater than that of diuron.