Ground and Surface water contamination by herbicides commonly used in rice cultivation is a matter of current concern in Corrientes regions. The fact that most commercial formulations of herbicides containing the active materials in a form immediately available increases the risk of transmission losses of herbicide applied to the crop and, consequently, the risk of contamination of ground and surface water. In this work we presented the adsorption of the herbicide 2-methyl-4-chlorophenoxyacetic acid (MCPA), widely used to control weeds in the rice cultive on soil high in organic matter (used in rice cultive) from determined from batch test. The adsorption equilibrium data were processed in accordance with four most widely used adsorption isoterms: Freundlich, Langmuir, Temkin and Dubinin-Radushkevitch isotherm models. The equilibrium data were best represented by Freundlich isotherm model, showing higher Kd values reveal that adsorption is light.
