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

Abstract

1. Six soils with a wide range in pH and in physical properties were treated with lime, 2,4-dichlorophenoxyacetic acid, and the calcium salt of the acid in such a manner as to obtain four conditions for each soil. 2. The treated 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 corn-seed bio-assay to determine relative toxicities. 3. The bio-assays indicated that the leachates from soil C (peat) were relatively nontoxic at the end of 2 weeks and that those from all soils except soil F (naturally alkaline) were relatively free of the herbicides at the end of 6 weeks. There were no significant differences in the degree of toxicity and its persistence in limed as compared with unlimed samples within each soil type or in that of the calcium salt versus the acid. 4. At the end of 6 weeks, the bottom half of each soil mass was tested for residual toxic effects by the germination of red kidney beans. This test indicated that soil F was still somewhat toxic from the treatment and that the samples of this soil leached with 10 surface-inches of water were more toxic than those leached with 16 surface-inches of water. All other soils were then free of the toxic effect of the herbicide.