The application of herbicides to the soils led to a significant drop in dehydrogenase activity with respect to untreated control soil samples. Obtained results indicated that soils treated with primeextra had the lowest dehydrogenase activity, while soils treated with glyphosate had the highest dehydrogenase activity when compared to other herbicides used in this study. In literature, opposite effects on several soil enzymes are reported (Gianfreda et al., 1994, 2005; Quilchano and Maranon 2002).