AbstractA 140‐day laboratory incubation, using surface soil from a long‐term soybean tillage study, evaluated tillage influence on [14C]metribuzin degradation. Higher plant residue conditions in no‐tillage (NT) soil inhibited metribuzin mineralization to[14C]carbon dioxide as compared to metribuzin degradation patterns observed in conventional tillage (CT) soil. At 140 days, relative abundance of extractable14Ccomponents in NT included polar metabolites>metribuzin = deaminated metribuzin (DA) = deaminated diketometribuzin (DADK), while in CT, components included metribuzin>polar metabolites>DADK≫DA. Conditions in NT apparently inhibited polar14Cdegradation, and resulted in its accumulation, while in CT polar14Cdegradation proceeded relatively rapidly. For both NT and CT, more14Cwas measured in an unextractable fraction than in any other fraction. A greater portion of the unextractable fraction in NT was associated with decomposed plant residue than in CT. Surface accumulation of crop residue, such as occurs under NT, provided a soil environment which altered metribuzin degradation p
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