Persistence of Some Plant Growth-Regulators when Applied to the Soil in Herbicidal Treatments

Abstract

1. Greenhouse experiments for determining the leachability and persistence of 2,4-dichlorophenoxyacetic acid in soil have been described. 2. When a soil was contaminated with 2,4-dichlorophenoxyacetic acid and then leached, it was found that the compound was present in the leachate. 3. It was demonstrated that normal plants developed in a green-house soil 8 weeks after the latter had been treated with high rates of 2,4- dichlorophenoxyacetic acid. Observations with respect to seed germination were similar. It may therefore be concluded that, under greenhouse conditions, this herbicide does not remain active in unleached soil for longer than 8 weeks. 4. In the field it was shown that 2,4- dichlorophenoxyacetic acid did not persist in soil for more than 80 days after treatment, while isopropyl N-phenylcarbamate had apparently disappeared within 60 days after treatment. 5. A field comparison was made of the persistence of 2,4-dichlorophenoxyacetic acid, 2-methyl-4- chlorophenoxyacetic acid, and isopropylphen...