Metalaxyl mobility in acid soils: evaluation using different methods

In the present work, different methods were tested to evaluate the adsorption and desorption of metalaxyl in two acid soils with different organic carbon and clay contents. The three methods (batch, stirred flow chamber and column) that were examined produced similar findings when the two soils were compared: (a) the metalaxyl adsorption capacity was higher in the soil with higher organic matter and clay content, and (b) the soil with the lower organic matter and clay contents provided higher adsorption rate constants. In the two soils tested, the metalaxyl adsorbed in the soil was highly reversible. When only one soil was considered, the different methods yielded different results. The metalaxyl adsorption and its rate were higher with the stirred flow chamber than in the column experiments, and in the column experiments, the total metalaxyl adsorption and the rate of adsorption were higher than in the batch experiments. The percentages of metalaxyl desorbed from the soil were similar in the stirred flow chamber and column experiments, but in the batch experiments, the percentages were significantly lower. In the stirred flow chamber experiments, the desorption processes were faster than the adsorption processes, while in the column experiments, the adsorption and desorption processes exhibited similar rates.