Weed Science (2012) 60, 468-473

Anna M. Szmigielski, Jeff J. Schoenau, Eric N. Johnson, Frederick A. Holm and Ken L. Sapsford (2012)
Determination of thiencarbazone in soil by oriental mustard root length bioassay
Weed Science 60 (3), 468-473
Abstract: Using an oriental mustard root length bioassay, thiencarbazone bioavailability and dissipation in five Saskatchewan soils was investigated under laboratory conditions. Thiencarbazone bioavailability was assessed at 0 to 3.9 µg ai kg⁻¹. Thiencarbazone concentrations corresponding to 50% inhibition (I₅₀ values) obtained from dose-response curves varied from 0.56 to 1.71 µg kg⁻¹. Multiple regression analysis indicated that organic carbon content (P = 0.018) and soil pH (P = 0.017) predicted thiencarbazone bioavailability. Thiencarbazone dissipation was examined in soils incubated at 23 C and moisture content of 85% field capacity. Thiencarbazone half-lives estimated from dissipation curves were 9 to 50 d, and organic carbon content (P = 0.002) and soil pH (P = 0.008) were significant factors affecting thiencarbazone dissipation. Thiencarbazone bioavailability decreases and dissipation rate is slower in Canadian prairie soils of high organic matter content and low soil pH. Because root length of oriental mustard plants also was reduced by ammonium, therefore ammonium-containing or -producing fertilizers can cause false positive results for thiencarbazone soil residues. Canaryseed roots had the same sensitivity to ammonium as oriental mustard roots but were not inhibited by thiencarbazone. Therefore canaryseed root length bioassay was effective in identifying inhibition caused by ammonium toxicity. Use of oriental mustard root and canaryseed root bioassays together can aid in interpreting bioassay results for detection of thiencarbazone residues.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Eric N. Johnson

Research topic(s) for pests/diseases/weeds:
control - general

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Brassica juncea (weed)