Microbial and Photolytic Dissipation of Imazaquin in Soil

Abstract

Microbial degradation of imazaquin {2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-3-quinolinecarboxylic acid} was monitored by measuring14CO2evolution for 7 months under controlled laboratory conditions. Up to 10% of the14C chain-labeled imazaquin that was applied to a Crowley silt loam was evolved as14CO2in 7 months. Less evolution of14CO2occurred on a Sharkey silty clay, a soil with higher clay and organic matter content, than on silt loam soils. The loss of 66 to 100% of the imazaquin applied to a Crowley silt loam incubated for 8 months at 18 C or 35 C, respectively, suggested that metabolic changes in addition to CO2evolution were occurring. Rapid loss of imazaquin phytotoxicity occurred when soils were held at warm-moist (35 C and −33 kPa) conditions conducive to microbial growth. Imazaquin was more persistent in soils stored under cool, dry (18 C and −100 kPa) conditions. Imazaquin on a soil surface dissipated rapidly when exposed to ultraviolet light or sunlight. Photodecomposition could be a major mode of imazaquin dissipation if this herbicide is allowed to remain on the soil surface.

Sulfentrazone Dissipation in a Tennessee Soil1

“…Rainfall in 1996 was above normal (Table 1). Above-normal moisture conditions may be conducive to more rapid chemical and microbial degradation (Basham and Lavy 1987). With more rain, sulfentrazone could have moved below the sampling zone.…”

Weed management in conservation crop production systems

“…Use of tillage to incorporate herbicides into soil in reduced tillage systems is a limited option. Incorporation in conventional systems can prolong the residence time for some herbicides by protecting them from volatilization or photodecomposition (Basham & Lavy 1987). Extending the residence time in the soil by incorporation may cause herbicide carryover problems in crop rotation systems (Curran et al 1992; Ferris et al 1989; Renner et al 1988).…”

Tillage Affects Imazamox Carryover in Yellow Mustard

“…The warmer soil likely increased the rate of microbial degradation of imazamox compared to other tillage treatments. Microbial degradation under aerobic conditions is the primary degradation mechanism of imidazolinones (Basham and Lavy 1987). Conditions that tend to favor microbial activity, such as warm, moist soils, also are the conditions under which the imidazolinones are most rapidly degraded (Mangels 1991).…”