Microbial biomass-persistence relationships of acifluorfen in a clay-loam soil.

The interference of the effect of the herbicide acifluorfen on microbial biomass and on hydrolytic capacity, and its persistence in a clay-loam soil before and after enrichment with glucose, were investigated. The experiment was carried out under laboratory conditions for 120 days. Acifluorfen was added to the soil at two different application rates corresponding to 1X and 10X the recommended field rate. Biomass-C was significantly higher in the enriched soil during the first 35 days; subsequently there was a tendency to return to the original value of the unenriched soil. The herbicidal treatments depressed the biomass-C level, particularly at the higher rate. The hydrolytic capacity, measured as FDA-hydrolase activity, was significantly higher in the enriched soil than in the unenriched soil. This was enhanced by acifluorfen treatment, chiefly at the higher rate. The degradation trend of acifluorfen was not significantly different at the two rates, but was significantly faster in the enriched soil. Half-life values of 28 and 40 days were found in the enriched and unenriched soil, respectively.