INFLUENCE OF SOIL PROPERTIES ON THE ADSORPTION AND MOBILITY OF METAMITRON

The adsorption and mobility of herbicide, metamitron, in 41 soils samp les from the province of Salamanca (Spain) was studied. Thirty-four of the samples assayed were from irrigated soils and seven were from nat ural, uncultivated soils with organic matter contents above 3%. The co rrelations between the Freundlich K constants, Kd distribution coeffic ients, and Rf mobility parameters and the soils parameters were determ ined. Considering all the soils, the soils with organic matter content s above 2% or the soils with organic matter contents below 2%, signifi cant correlations (p<0.001 to p<0.05) were found between K and Kd and the organic matter content of the soils. There were also a significant correlations (p<0.05) of K and Kd with clay+silt and clay contents of soils with organic matter contents below 2%. The adsorption of the he rbicide by isolated soil components confirmed the results obtained wit h the soils and point to the importance of the exchangeable cation nat ure of the samples in the adsorption process. Based on Rf values obtai ned by TLC, the herbicide was found to be moderately mobile in 74% and mobile in 26% of the soils studied. The results of metamitron leachin g by thin layer chromatography (TLC) and in undisturbed soil columns i ndicated the influence of organic matter content and of soil texture o n the mobility of this herbicide.