Sorption and desorption of the herbicide alachlor on humic acid fractions from two vermicomposts

The present study focuses on the analysis of two vermicomposts, that have b een used as alternative sources of restitution of soil organic matter, as w ell as sources of nutrient replacements. For this purpose, two samples of v ermicomposts from different Brazilian regions (Sao Carlos-SP and Londrina-P R) were characterized according to their humic acid content. Both samples h ad a pH value near 7.0, and the humic acids present showed high cationic ex change capacities and low values for the C/N ratios. The infrared spectra s howed bands that suggested the presence of aliphatic and aromatic component s bound to phenolic, carboxylic and amide groups. The effect of vermicompos t added to soil on the application of alachlor was evaluated. Alachlor sorp tion, Freundlich isotherms and alachlor desorption curves in the soil matri x and the vermicompost/soil mixture matrix were determined.