Side Effects of Rimsulfuron on the Microbial Biomass of a Clay-Loam Soil
- P. Perucci * and
- L. Scarponi
The effect of Rimsulfuron treatment on soil microbial biomass was studied in a clay-loam soil under field and laboratory conditions. Field trials were performed at the usual field rate (0.005 ppm; FR) and 10 times the field rate (10FR). In addition to FR and 10FR, one hundred (100FR) times the field rate was also assayed in laboratory experiments. Determinations of microbial biomass-C content, fluorescein diacetatehydrolysis activity (FDA hydrolysis) and protease activity were carried out 0, 1, 2, 4, 7, 10, 15, 25, and 45 d after herbicide application. In the field trials there were no significant side effects on the investigated parameters at either rate. Conversely, laboratory experiments showed decreases in microbial biomass-C levels and increases in FDA-hydrolysis and protease activity at 10FR and 100FR within the first 10 d. As increases in the activity of FDA hydrolysis and protease were concomitant with the decreases in the microbial biomass-C content a toxic effect on soil microrganisms with a consequent release of hydrolytic enzymes from cell lysis has been hypothesized. This effect was transitory and only at the higher rates of rimsulfuron was it significant.
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