ADSORPTION AND DESORPTION OF IMAZAPYR BY SOIL

The adsorption and desorption of imazapyr, -[4,5-dihydro-4-methyl-4-(1 -methylethyl)-5-oxo-1H- imidazol-2-yl]-3-pyridinecarboxylic acid, by s ix soils were studied. Adsorption isotherms conformed to the Freundlic h equation. A multiple regression analysis indicated that K-f(ads) val ues were better correlated if cation exchange capacity and pH (r = 0.9 84) were simultaneously taken into account. The results show that the herbicide adsorption is strongly affected by the pH and the charge of the adsorbing component. The organic matter is effective in imazapyr r etention, but only at pH <5. Enhanced adsorption was observed in amorp hous iron oxide, most likely because of a ligand exchange process.