Oil impurities-contg. soils (content 0.5-20 g/kg of soil) and soils with addnl. added urea (N content 200 mg/kg of soil), compost, bentonite, zeolite and CaO (concns. 3%, 2%, 2% and 50% by mass, resp.) as well as origin soils were used for maize, spring barley, mustard oats cultivations to test the impact of oil impurities and addnL used substances on total N and nitrate N in soils after crops. The use of urea resulted in a significant increase in content of both forms of N in soils for all cultures, while other substances did not show any specific effect on the N content in soil.