With the aim to evaluate the soil mechanic reaction-traffic relationship to different tillage systems, penetration resistance and soil bulk density measurements were made. Four traffic conditions (6, 8, 10 and 12 passes of a 2WD, 52.25 kW tractor) were evaluated in a typic Argiudol soil with six years of wheat-soybean rotation under no-tillage and conventional tillage. Bulk density and penetration resistance were used to evaluate the traffic effects on soil compaction. After the six-year rotation, no-tillage system showed significant higher penetration resistance values with respect to conventional tillage system in the topsoil layer. The bulk density values recorded in the non tillage system determine root growth limitation at low number of passes and at shallow depth. The greater the number of passes, lower the depth at which the penetration resistance can reach potential root growth limiting values.