The fate of atrazine and metolachlor, applied as a mixture, in soil taken from two pesticide-contaminated sites in Iowa (denoted as Alpha or Bravo) were determined in laboratory studies. Atrazine and metolachlor degradation, as well as atrazine mineralization, were greater in soil collected from Kochia scoparia L. (Schrader) rhizosphere than in soils from unvegetated areas. The radiolabeled 14C-carbinol and 14C-morpholinone metabolites were identified in 14C-metolachlorapplied soil 60 d after treatment. The half-life for atrazine in Alpha soil was significantly less in the rhizosphere soil (50 d) than in unvegetated soil (193 d). Quantities of specific atrazine degraders were one to two orders of magnitude greater in Bravo soils than in Alpha soils. In an experiment with plants present, significantly more 14C-atrazine was taken up by K. scoparia (9.9% of the applied 14C) than by Brassica napus L. Significantly less atrazine was extractable from soils vegetated with K. scoparia than from soils vegetated with B. napus or unvegetated soils.
- Microbial degradation
- Pesticide contamination