Alachlor biotransformation and sorption in soil from two soybean tillage systems

Document Type

Article

Publication Date

1-1-1996

Abstract

Few studies have investigated tillage effects on alachlor [2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl)acetamide] degradation. Objectives here were to evaluate kinetics and mechanisms of alachlor degradation in surface (0-5 cm) Dundee silt loam (fine-silty, mixed, thermic, Aeric Ochraqualf) from plots managed for 7 years as conventional tillage (CT) or no-tillage (NT) soybeans (Glycine max L.). In experiment I, incubations ranged from 0 to 54 days after 14C-ring-labeled alachlor (4.44 μmolkg-1) application. In experiment II, soil was incubated (10 g:3 mL of CaCl2) with 14C-labeled alachlor (14.8 or 111.2 μmol L-1) from 1 to 25 days. Soils in experiment I were extracted with methanol and in experiment II were sequentially desorbed with 0.01 M CaCl2 and methanol and then oxidized to measure unextractable 14C. Mineralization of alachlor was more rapid in NT. Methanol-extractable and CaCl2-desorbable alachlor declined during incubation for both tillage treatments, with a corresponding increase in methanol-unextractable 14C. Tillage did not influence the initial disappearance of alachlor (half-life ≈ 6.5 days) but did affect metabolite transformations. Alachlor sorption was more rapid in NT, accompanied by less CaCl2-desorbable and more methanol-extractable alachlor and metabolites. Unextractable 14C was also greater in the NT soil. Acidic metabolites accumulated in both tillage soils.

Publication Source (Journal or Book title)

Journal of Agricultural and Food Chemistry

First Page

1128

Last Page

1134

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