Adsorption and Desorption of Chlorsulfuron in Agricultural Soils of Mara River Basin, Kenya

Chlorsulfuron is a sulfonylurea herbicide widely used in Kenya to control broadleaf and grass weeds in wheat. Its sorption was studied in five wheat growing soils from Mara River Basin in Kenya using batch sorption method. Freundlich adsorption equation described the sorption mechanism of chlorsulfuron with adsorption coefficients (Kf) ranging between 0.46 and 0.75. The Kf showed positive and negative correlation (P ≤ 0.05) with organic carbon (r = 0.7882) and soil pH (r = 0.8111) respectively. Adsorption isotherms were L-type suggesting the herbicide sorption was inversely related to the initial concentration of chlorsulfuron in solution. Desorption of the herbicide was concentration dependent and hysteresis effect was present in three soils implying that sorbed chlorsulfuron was not easily released possibly leading to phytotoxicity to rotational crops. Chlorsulfuron was poorly sorbed on to the soils demonstrating its high leaching potential onto the lower profiles and carry over that would injure susceptible plants in the future.