The aim of this study was to determine the effects of the commercial biofertilizer UGmax on soil cellulase (CEL) and dehydrogenase (DH) activities, microbial biomass carbon content (MB-C), and some chemical properties in the humus horizon of an arable field (Luvisols) over a three-year period (2005, 2006, 2008) for winter wheat and for winter rapeseed in 2007. Twenty soil samples were taken from the area studied in 2005 (the control year without UGmax treatment), while in the other years ten soil samples were taken after UGmax treatment and ten from the control, always after plants were harvested. No clear effects of UGmax treatment on the studied properties were found. Compared to the control, the application of UGmax increased soil reaction and soil organic carbon (C_ORG) concentrations in the entire study period, although for the latter property the changes were not statistically significant in 2007. A significant reduction of CEL activity was noted after the second and third years of UGmax application, while DH activity was significantly higher when UGmax was applied compared to the control only after the first year of treatment.