A pot experiment was undertaken to investigate the effect of soil contamination with diesel oil, used at doses of 0, 3, 6, 9, 12 and 24 g kg^-1, on the activity of dehydrogenases, urease, acid phosphatase and alkaline phosphatase. An attempt was also made to reduce the negative effects of diesel oil on the biochemical activity of soil by its fertilization with finely ground pinewood sawdust and urea. Enzymatic activity was determined on days 14, 58 and 108 of the experiment.
The experiment demonstrated that soil contamination with diesel oil at amounts from 3 to 24 mg kg^-1 disturbed the biochemical equilibrium of soil. The contamination stimulated the activity of dehydrogeanses, urease and alkaline phosphatase. In addition, it had adverse influence on the growth and development of oat and maize.