Interactions of ALS-Inhibiting Herbicide Residues in Three Prairie Soils

Abstract

The objective of this study was to determine if the presence of two acetolactate synthase (ALS)-inhibiting herbicide residues in different Saskatchewan soils would result in additive, synergistic, or antagonistic interactions. This was determined through field trials where herbicides were applied sequentially over the course of 2 yr. The herbicides examined in these experiments were imazamethabenz, flucarbazone, sulfosulfuron, and florasulam, each in combination with imazamox and imazethapyr. The phytotoxicity and persistence of the herbicides in soil was assessed using an oriental mustard root inhibition bioassay. The determination of herbicide interaction was made through the comparison of the experimentally observed values to theoretically expected values derived from a mathematical equation. On the basis of the bioassay analysis, it was found that the herbicide residue combinations resulting from sequentially applied ALS-inhibiting herbicides in the three soils produced additive injury effects rather than synergistic or antagonistic interactions.

Repeat‐pulse 13CO2 labeling of canola and field pea: implications for soil organic matter studies

“…The plant density was four plants per core, which reflected recommended seeding rates of field pea (224 kg ha À1 ) and canola (6.7 kg ha À1 ). The plants were grown in a controlledenvironment growth chamber (228C, 18 h of light per day) and watered daily to soil field capacity 24 which was measured periodically during the experiment with a 5TE soil moisture sensor (Decagon Devices Inc. Pullman, WA, USA). The W-CNL soil had been fertilized in the field prior to core collection (15.2 kg P ha À1 as mono-ammonium phosphate (11-52-0) and 74.4 kg N ha À1 as mono-ammonium phosphate and urea (46-0-0)); no additional fertilizer was applied to the cores.…”

Field and Greenhouse Bioassays to Determine Mesotrione Residues in Soil

“…Greenhouse bioassays are an alternative to field bioassays; in greenhouse bioassays, low concentrations of residual herbicides can be detected and results are available in a shorter time period than with field bioassays. Soil bioassays have been used to detect different herbicide residues, especially sulfonylureas (Eliason et al 2004;Geisel et al 2008;Hernandez-Sevillano et al 2001;Stork and Hannah 1996;Sunderland et al 1991). O'Sullivan (2005) developed a grower-friendly greenhouse bioassay to determine the effect of imazethapyr residues in the soil on vegetable crops.…”

Application of a Laboratory Bioassay for Assessment of Bioactivity of ALS-Inhibiting Herbicides in Soil

“…Organic matter in the form of humus is colloidal in nature with a highly reactive surface containing many functional groups capable of binding herbicide molecules. Reduced phytotoxicity of flucarbazone (Eliason et al, 2004;Geisel et al, 2008), imazethapyr (Szmigielska & Schoenau, 1999), metsulfuron (Szmigielska et al, 1998), pyroxsulam and thiencarbazone (Szmigielski A.M., unpublished) in Canadian prairie soils of high organic (a) (b) matter content was explained by increased herbicide sorption. Using mustard root bioassay, dose-response curves were constructed for these herbicides and the I 50 values were estimated.…”

“…Interactions of imazamethabenz, flucarbazone, sulfosulfuron and florasulam in combination with imazamox/imazethapyr in western Canadian soils were investigated in laboratory experiments (Geisel, 2007) and field trials (Geisel et al, 2008). In the laboratory experiments, soils were amended with individual herbicides and combinations of herbicides, and their effect on mustard root length inhibition was measured.…”