Removal of 2,4-Dichlorophenoxyacetic Acid and Its Calcium Salt from Six Different Soils by Leaching

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Abstract
Six soils with a wide range in physical properties and in pH from 3.8 to 8.4 were treated with lime, and the herbicides, 2,4-D and the Ca salt of 2,4-D to obtain 4 conditions in each soil. The soils were leached with water at rates equivalent to 10 and 16 surface-inches over a 6-week period. The leachates were collected and tested weekly with a bio-assay to determine relative toxicities of each soil treatment. Leachates from peat soil were relatively free of toxicity at the end of 2 weeks and those from all soils except a naturally alkaline soil were relatively free of the herbicides at the end of 6 weeks. There were no significant differences in degree or persistence of toxicity in the limed as compared with the nonlimed samples of each soil type or of the Ca salt versus the acid.