In a field experiment, the accumulative level of a brown acid soil (Dystric Cambisols) formed of slightly clayey sand, the sewage sediment was introduced in the following doses of dry mass: 30; 75; 150; 300 and 600 Mg·ha^–1. The control object was the soil with no organic fertiliser. The purpose of this paper was to estimate the reaction of various doses o f the sewage sediment on protease and urease activity in the light soil, not fertilised during the last six years. An essential increase in the protease and urease activity in comparison to the activity of these enzymes in the soil of the control object was confirmed in presence of the higher doses of sewage sediment (300 and 600 Mg·ha^–1). This stimulation was in fact accompanied with the higher content of organic carbon, nitrogen (total N) and the mineral forms of nitrogen (N-NH₄⁺and N-NO₃^–) in the soil. The results we obtained have shown there is a possibility to use the sewage sediments in order to better the fertility of light soils.