METRIBUZIN SORPTION DYNAMICS IN ACID SOILS OF NZOIA SUGARCANE ZONE IN WESTERN KENYA

Abstract

The adsorption, desorption and leaching of metribuzin in agricultural soil samples taken from Nzoia sugarcane farming area in Kenya were determined using standard methods. The Freundlich adsorption isotherm constants (Kf and 1/n) were found to be 0.54 µg/g and 0.61 µg mL-1, respectively. 94.9% of the residues were recovered after 6 hours of the desorption test and 93.7% of applied dose was found in the leachate after 9 hours of leaching in a soil column. The adsorption curves indicated L-type of adsorption for 0.1, 1.0 and 2 µg L-1 initial pesticide concentrations and S-type for the 5 ppm initial concentration with peak equilibrium adsorption established after 4 hrs of exposure for the 0.1, 1.0, 2.0 µg L-1, respectively, and after 6 hours for the 5 µg L-1 initial concentration. Although the metabolites were not determined, HPLC analysis showed that degradation was rapid and started to occur after 4 hours of exposure, influencing its adsorption isotherms