Factors influencing 2,4-D sorption and mineralization in soil

This study quantified 2,4-D [(2,4-dichlorophenoxy)acetic acid] sorption and mineralization rates in five soils as influenced by soil characteristics and nutrient contents. Results indicated that 2.4-D was weakly sorbed by soil, with Freundlich distribution coefficients ranging from 0.81 to 2.89 microg(1 - 1/n) g(-1) mL(1/n). First-order mineralization rate constants varied from 0.03 to 0.26, corresponding to calculated mineralization half-lives of 3 and 22 days, respectively. Herbicide sorption generally increased with increasing soil organic carbon content, but the extent of 2,4-D sorption per unit organic carbon varied among the soils due to differences in soil pH, clay content and/or organic matter quality. Herbicide mineralization rates were greater in soils that sorbed more 2,4-D per unit organic carbon, and that had greater soil nitrogen contents. We conclude that the effect of sorption on herbicide degradation cannot be generalized without a better understanding of the effects of soil characteristics and nutrient content on herbicide behavior in soil.