The activity of flumioxazin and metribuzin herbicides was evaluated in four different soils using washed sand. The soils were: an Utisol collected in an agricultural region in the State of Minas Gerais and an Oxisol collected in three different agricultural regions; two in the State of Minas Gerais and one in the State of Mato Grosso do Sul. Ten rates of each herbicide were evaluated for each soil in pots, with five replications per treatment. Herbicide rates tested and the amount of soil per pot varied with the type of soil being evaluated. The soil moisture content was maintained at soil moisture capacity with simulated rainfalls. The soil type, its physical-chemical properties, and mainly its organic carbon content affected the activity rate of both herbicides. For flumioxazin, the soils with the highest organic carbon content presented the highest values of I50, which means, greater adsorption of the herbicide. Meanwhile, for metribuzin, the activity rate was affected by the pH and the organic carbon content of the different soils tested. The results of this study sug gest that the recomendations for use of herbicides should vary according to the type of soil.
Adsorption; bioassay; organic carbon