Tebuthiuron adsorption was determined in samples from 0-10 to 10-20 cm layers of three soils from the county of Ribeirão Preto (SP)-Brazil: Quartzarenic Neosol (Entisol), Red Latosol dystrofic and Red Latosol dystroferric (Oxisols). Sorption data were obtained by batch equilibrium and fitted to four adsorption models: Freundlich, linear, Langmuir and Lambert. Several statistical criteria were applied for selection among these isotherms. Freundlich model showed the best fit to the data. Kd values ranged from 0.723 to 2.573 L kg-1, and were correlated to organic carbon (OC) and clay content; K OC values ranged from 135.4 to 374.3 L kg-1. Tebuthiuron mobility was evaluated in soil-packed columns under laboratory conditions and detected at the depths of 60 cm in the Quartzarenic Neosol, 20 cm in the Red Latosol dystrofic and 10 cm in the Red Latosol dystroferric, its leaching being inversely related to Kf values.
adsorption isotherms; herbicide; leaching; sandy soil; oxisol; tropical soils