In soil sampled after a two-year pot experiment, the activity of urease and dehydrogenase and content of nitrogen have been determined. The experiment included three factors: 1. the amount of nickel added to the soil (0, 75, 150 and 225 mg · kg-1 of soil), 2. liming (0 and Ca according to 1 Hh hydrolytic acidity), 3. organic materials (straw of rye and brown coal). Test plant was cocksfoot, which four cuts were collected in each growing season. It was found that nickel added to the soli in dose of 75 mg · kg-1 activates enzymes studied, whereas higher doses cause them explicit deactivation. Both liming and waste organic materials limited the negative effect of higher doses of nickel on the activity of dehydrogenase and urease. Simultaneously, both straw and brown coal caused a slight increase in the amount of nitrogen in the soil.