The term soil compaction refers to the compression of an unsaturated soil during which an increase of the bulk density of soil occurs in consequence of the reduction of its volume, due to the expulsion of the air caused by inadequate management. To study the effect of different soil management systems on maximum dry bulk density and optimum moisture content, an experiment was conducted in a Dusky Red Latosol of the Lavras (MG, Brazil) region, submitted to the following management systems: plow disk (AD), plow moldboard (AA), minimum tillage (CM), no tillage (SD) and harrow disk (GD). The experiment was installed in November, 1994. Disturbed soil samples were taken in 1996: in January before bean plantation; in April, before bean harvest; and in November, before corn planting. Soil samples were taken from the 0 to 0.07 layer and from the 0.20 to 0.27 m layer, under management systems AD, CM and AA. For management system SD, the disturbed soil samples were taken from the layer of 0-0.07 and 0.25-0.32 m depth and for GD from the layer of 0 to 0.07 and 0.15 to 0.22 m depth. Maximum dry bulk density (Ds máx) and critical moisture content(Ucrít) were obtained from the soil compaction curves. Clay content, organic matter, plasticity limit (PL) and water content retained at - 0.033 and - 0.01 MPa were also determined. The Ds máx, Ucrít for the soil management systems, time of sampling and depth were not statistically different, showing that they were not influenced by clay and organic matter content. Ucrít was observed to occur at 90% of PL and at 90% of the water retained at - 0.01 MPa, being approximately equal to the water content retained at - 0.033 MPa.
soil tillage systems; standard Proctor test; physical properties