Metribuzin degradation in soil: I—effects of soybean residue amendment, metribuzin level, and soil depth

Abstract

A BSTRA CT Plant residue and soil depth ejfects on metrihuzin degradation were investigated. Dundee silt loam soil collected at depth increments of0-10 em (SUR) and 10-35 cin (SUB) was treated with labeled Samples were assayed at several time points up to 140 days after treatment. Soybean residue nws added to half of the SUR samples (RES), with remaining SUR unamended (NORES). None of the SUB samples were amended with soybean residue. Metribuzin mineralization to I4CO2 proceeded more slowly in RES and SUB than in NORES and SUR, respectively. Extractable components in SUR samples included polar metabolites, plus deaminated metrihuzin ( D A ) in the RES, and parent metrihuzin in the NORES. Deaminated diketometribuzin (DADK) and metribuzin comprised major I4C components extractedfroni SUB, while in SUR, faster degradation of metabolites resulted in metrirubin as the primary identifiable compound. Unextractable 14C increased until day 35 for both RES and NORES, after which it remained constant for NORES, hut declined for RES. A corresponding rise in RES polar 14C suggested that as soybean residue decomposed, I4C bound in the residue MIUS released as extractable polar material. Soil with soybean residue accumulation r n q alter metabolite degradation patterns, but does not impede initial metribuzin degradation. Depth diffL'renceS in metribuzin degradation were attributed to reductions in microbial activity with increasing soil depth.

Atrazine and Metribuzin Sorption in Soils of the Argentinean Humid Pampas

“…For atrazine, K f values ranged from 7.82 to 2.06, and the order was Balcarce Ͼ Tres Arroyos Ͼ Dorrego, with similar patterns of decreasing atrazine sorption with increasing soil depth. Thus, shallow subsoils would appear to provide increased opportunity for further leaching of compounds escaping from the surface layer [14,24]. Lower K f values for atrazine with increasing depth would indicate a lower sorption at greater depths and therefore a greater leaching potential for this herbicide once it has passed throughout the upper layers of the soil.…”

Mobility and persistence of four herbicides in soil of a South Australian vineyard

“…Applying a pesticide to the soil surface without incorporation, which is typical practice for conservation tillage, can increase the amount of pesticide leaching shortly after application 1. 2…”

Impact of Basic Soil Parameters on Pesticide Disappearance Investigated by Multivariate Partial Least Square Regression and Statistics

“…Pesticides may be degraded by purely abiotic processes as exemplified by the hydrolysis of aldicarb, but a review of several pesticides has shown that in subsoils the degradation is primarily microbial (Fomsgaard, 1995). Regarding metribuzin the microbial degradation and the mobility in natural aquifers and soil columns has been characterized (Locke and Harper, 1991; Agertved et al, 1992; Locke et al, 1994; Buss et al, 2006). Likewise, the microbial degradation of MCPA has been described (Loos et al, 1979; Sorensen et al, 2006).…”