Effect of aggregate size on leaching of herbicide in soil columns

Summary: In a column experiment with dry aggregated soils, the effect of aggregate size on leaching of metribuzin from the upper soil layer (2.5 cm) was studied. The penetration of the herbicide was less than predicted by the equilibrium retardation factor. The penetration was less for large than for smalt aggregates due to kinetic effects induced by the aggregates. These kinetic effects overruled the effect of adsorption. Although the mean herbicide penetration was limited, part of the herbicide moved freely with the water as the herbicide was found throughout the column and in the leachate.