ADSORPTION AND DESORPTION OF DIMEPIPERATE BY SOILS

The adsorption and desorption of dimepiperate, ha,alpha-dimethylbenzyl )-1-piperidinecarbothioate, on three soils of various physical and che mical properties was studied. Adsorption isotherms conformed to Freund lich equation. The k(f) values increased with increasing organic carbo n content of the soils. To confirm the effect of organic matter, the a dsorption of the herbicide was studied after removal of organic matter by peroxidation. This soil treatment caused a sequential loss of adso rptive capacity. Desorption isotherms also conformed to Freundlich equ ation, but K(des) values were higher than those for adsorption and inc reased with increase in concentration of initially adsorbed dimepipera te. Hysteresis was indicated by the decrease in slope of desorption co mpared to adsorption isotherms. Hysteresis decreased with increasing m ethanol content in the extracting solution. The factors involved are d iscussed.