Excessive soil compaction caused by agricultural tractors during plant production processes results in a considerable risk of reduced crop yields, increased erosion processes, greater input of energy in tillage and increased CO2 emission to the atmosphere. As a consequence we observe a threat of degradation in Luvisols found over a considerable area in the Polish Plain and the North European Plain. In-situ studies made it possible to identify and quantify selected factors determining soil density in loamy sand at a depth of max. 0.4 m in wheel tracks of tractors weighing from 19 to 72 kN with single standard wheels and with dual wheels. Analyses were conducted during the first passage over soil loosened during ploughing. It was generally shown that at a lower initial soil density in the topsoil tractors with both driving systems cause greater density increments and lower soil density than in the hardpan. Tractors with dual wheels exert much lesser pressure and cause soil density by approx. 0.1 g·cm-3 lower in the topsoil and by approx. 0.06 g·cm-3 in the hardpan than it is the case for tractors with single wheels. Tractors varying in their weight cause similar soil densities in the topsoil, while in the hardpan heavier tractors cause greater soil densities than light tractors. Generally, tractors with single wheels compress the soil in the topsoil layer to 45 up to 65% of compressibility, while tractors with dual wheels do it to approx. 26 up to 49% of compressibility, respectively.