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Title: THE EFFECTS OF ACETOLACTATE SYNTHASE INHIBITING HERBICIDES ON SOIL MICROORGANISMS

Author
item POTERA, R - UNIV OF ILLINOIS
item RIECHERS, DEAN - UNIV OF ILLINOIS
item TRANEL, PATRICK - UNIV OF ILLINOIS
item SIMS, GERALD

Submitted to: American Society for Microbiology Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 12/6/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Impairment of plant amino acid biosynthesis is a common mode of action of many herbicides. These herbicides also inhibit microbial ALS, which raises the possibility that soil bacteria will also be affected by these compounds. When measured at the bulk process level, many soil processes, for which catabolic genes are widely distributed, may appear unaffected by the addition of these compounds. Field plots with no previous history of herbicide application were established and treated with field rates of imazethapyr, flumetsulam, atrazine, or atrazine in combination with flumetsulam. Samples taken over a two-year period were analyzed to determine what effect ALS treatment had on soil nitrification, microbial growth, and degradation of atrazine. Rates of 14C-atrazine mineralization were determined in the presence and absence of ALS herbicides. In soils with no history of prior treatment, flumetsulam inhibited atrazine mineralization. Inhibition of nitrification was measured using a rapid difussion method. Susceptibility of atrazine- degrading bacteria, pseudomonas sp. ADP, to the ALS herbicides was tested using an ALS ensyme assay. The ALS enzyme of this bacterium showed only 62% of its activity at nanomolar concentrations of imazethapyr, 50% with prosulfuron, 60% with thifensulfuron-methyl, and 70% with chloruslfuron, although the growth of this organism was not affected. These results suggest that there is an inhibitory effect on soil microorganisms by the ALS herbicides, but that the microbial populations may rapidly become less sensitive to these herbicides.