Nitrogen, in particular nitrate nitrogen, is a mobile nutrient that can be readily dispersed in soil, thus causing environmental pollution. Sulfur may have a beneficial effect on nitrogen transformations in soil and in plants. The objective of this study was to determine the effect of sulfur fertilization on the dynamics of changes in mineral nitrogen (N-NH4 and N-NO3) content of soil samples collected each year in the spring and fall at a depth of 0-40 and 40-80 cm. A three-year field experiment was conducted in Byszwałd near Lubawa. The soil had acidic reaction (pH 1 mol KCl dm–3 of 5.30) and contained the following concentrations of mineral nutrients: mineral nitrogen – 24.0, sulfate sulfur – 4.10, available phosphorus – 34.5, available potassium – 110.0 mg kg–1 soil. The experiment was carried out in a randomized block design and comprised eight fertilization treatments in four replications. Three sulfate sulfur (S-SO4) and elementary sulfur (S-S0) fertilization levels were applied: 40, 80 and 120 kg ha–1. The content of nitrate nitrogen(V) and ammonia nitrogen(III) was determined in soil samples by the colorimetric method using phenoldisulfonic acid and Nessler’s reagent, respectively. In most cases, increasing sulfur doses caused an increase in the N-NH4 content of soil samples collected at a depth of 0-40 cm. The N-NH4 content of the 40-80 cm soil layer varied. NPK+S fertilization, in particular the application of a single S-SO4 dose, contributed to an increase in N-NO3 concentrations in both sampled soil horizons in the majority of treatments, compared with the NPK treatment.