Tropical soil attributes and the sorption of imazaquin

Abstract

Imazaquin is an acid herbicide widely used in Brazil to control weeds associated to the soybean crop. The purpose of this research was to study imazaquin sorption and its relation to CEC, pH and organic carbon (OC) and clay contents of eleven tropical soil samples. In order to establish the sorption isotherms, imazaquin solutions at concentrations of 0.53, 0.88, 1.45, 2.71, and 5.20 mg mL-1 were prepared in 0.005 mol L-1 CaCl2 solution with the addition of radiolabeled tracer (14C-imazaquin). The sorption coefficients (Kf) were calculated according to the linear shape of the Freundlich isotherm equation. Imazaquin sorption ranged from low to moderate (Kf < 3.0), except for the Aquox soil. OC content and pH were the soil attributes that best correlated to imazaquin sorption. The incorporation of clay content in the regression analysis increased the model×s precision by 20 %. Imazaquin shows higher availability and, therefore, higher leaching potential when applied to soils with pH higher than 6 and low contents of OC and clay.