The objective of this work was to determine the coefficients of ametryn sorption and desorption in Red-Yellow Ultisol (PVA) and Red-Yellow Latosol (LVA) with different pH values. Thus, 0-20 cm depth soil samples were collected from degraded pastures without the use of herbicide in the region of Viçosa-MG, and incubated or not with limestone for 90 days. The Batch slurry method was used under controlled laboratory conditions. The method consisted of using 10.0 mL solution at increasing concentrations of ametryn standard, prepared in 0.01 mol L-1 CaCl2 solution, added to 2.00 g of soil, and remaining under rotating agitation for 12 h (pre-determined equilibrium time). After centrifugation and filtration, the supernatant concentration was determined by high performance liquid chromatography (HPLC) with UV detector of 245 nm. Desorption was evaluated using the samples contained in the tubes, after the sorption trials, which contained the initial dose of 25 mg L-1 of herbicide. The PVA presented the highest adsorption coefficient (Kfa) compared to the LVA,regardless of the pH values of the samples. This was attributed to the higher organic matter content in the PVA, compared to the LVA. When comparing the same soil (LVA) at different pH values, it was observed that pH value increase resulted in a lower Kfa value. Low hysteresis indices were observed for ametryn in the soils studied, representing a risk of this herbicide leaching in the profile of these soils.
herbicide; soil behavior; chromatography; Freundlich isotherms
