Availability and Persistence of Imazaquin, Imazethapyr, and Clomazone in Soil

Abstract

The availability and persistence of imazaquin, imazethapyr, and clomazone were studied in a Cisne silt loam (1.3% organic matter) and a Drummer silty clay loam (5.8% organic matter). Availability of all three herbicides to bioassay species was greater in the Cisne soil than in the Drummer soil. Corn root growth was more sensitive to imazaquin and imazethapyr than corn shoot growth. Shoot and root growth of wheat was inhbited by similar clomazone concentrations. In field experiments conducted in 1984, 1985, and 1986, all three herbicides were more persistent in the Drummer silty clay loam than in the Cisne silt loam. Clomazone and imazethapyr were detected by liquid or gas chromatographic analysis in the Drummer soil 3 yr following application. Crop injury occurred 5 months after application of imazaquin and clomazone to the Drummer soil. In the Cisne soil, only imazethapyr caused crop injury 5 months after application. Herbicide residues found below 7.5 cm were greater in the Drummer soil than in the Cisne soil.

VA-mycorrhizae and mycorrhiza stimulating isoflavonoid compounds reduce plant herbicide injury

“…Imazaquin-phytotoxicity is lower in coarse-textured than in finetextured soils. The I50 for imazaquin was found to be 9 ppb in a silt loam and 73 ppb in a silt clay high organic matter loam soil (Loux et al, 1989). Herbicide effects on VAM root colonization are complex.…”

“…Although these herbicides are very selective, they can cause injury on susceptible crops (Barrett, 1989a, b;Loux et al, 1989;Renner et al, 1988). Crop phytotoxic symptoms include stunting, shortened internodes, deformed leaves, interveinal chlorosis, loss of apical dominance and premature senescence (Hess, 1989;Shaner, 1989b) and have been found to occur in double cropped soybeans and other crops (Barnes et al, 1989;Basham et al, 1987;Mills and Witt, 1989a, b;Renner et al, 1988).…”

“…Although the threshold level for imazaquin carryover is approximately 13 ppb, soil concentrations as low as 7ppb soil can affect crop growth (Basham et al, 1987;Basham and Lavy, 1987;Stougaard et al, 1990). Herbicide carryover injury is, however, not restricted to imidazolinones (Barrett, 1989c;Hartzler et al, 1989;Loux et al, 1989;Marking, 1988). Attempts to minimize herbicide injury by using chemical antidotes or 'safeners' (Hatzios, 1989) and by developing herbicide crop resistance (Schulz et al, 1990) have been made, but they presently have limited commercial application.…”

Response of four fall-seeded cover crops to residues of selected herbicides

“…Differences in soil organic matter (OM), cation exchange capacity (CEC) and soil texture in two growing seasons may also have contributed to the observed differences between years for oilseed radish from imazethapyr residues. Many studies have reported the effects of soil OM, CEC and clay content on imazethapyr persistence (Loux et al, 1989;Goetz et al, 1990). Loux et al (1989) found that there was positive relationship between adsorption of imazethapyr and clay content.…”

“…Many studies have reported the effects of soil OM, CEC and clay content on imazethapyr persistence (Loux et al, 1989;Goetz et al, 1990). Loux et al (1989) found that there was positive relationship between adsorption of imazethapyr and clay content. According to Goetz et al (1990), lower degradation of imazethapyr was associated with greater adsorption in heavy textured soils with high OM and CEC content, resulting in increased imazethapyr persistence.…”