The aim of our experiment was to determine the effect of heating oil application on the count of mi-croorganisms and some physico-chemical properties of limed and lime-free soil and soil sown with yellow lupine of the Markiz variety and unsown soil. The results obtained indicate that heating oil deteriorated the physico-chemical properties of the ex-perimental soil (acidification, decrease in the total alkaline exchangeable cations, soil exchange capacity and alkaline cation soil saturation). At the same time, it stimulated, to a different degree, the multiplication of soil microorganisms, especially oligotrophic bacteria (10-fold) and bacteria representing the genera of Pseudomonas spp. (8-fold). Lime application and cultivation of yellow lupine had a positive effect on the physico-chemical properties of soil and stimulated the growth of Azotobacter spp.