Soil compressibility depends on the type, intensity and frequency of the load applied by agricultural machinery and on soil management. This study was aimed at evaluating the effect of traffic of agricultural machines on the compressibility of a Paleudalf chisel plough and compacted under no-tillage. In an area under no tillage since 1989, the following treatments were used for sampling: PD = no tillage since 1989; PDE1 = no tillage plus chisel plough in december the year 2002 and february 2004; PDE2 = no tillage plus chisel plough in december 2004; PDC1, PDC2 and PDC3 = no tillage plus four passes of a machine of 10Mg in December, respectively to the agricultural years of 2001/2002, 2002/2003 and 2001/2002 - 2002/2003. Soil cores were collected at 0.08-0.13m depth to evaluate the compressive parameters of soil. In the no tillage under additional compaction higher and lower values were obtained respectively of bulk density and soil compression index. The bulk density and the soil compression index are concistant and sensitive parameters to detect alterations in the soil structure. The non linear model (McNabb & BOERSMA, 1993) is a potential tool to determine the bulk density of soils under no tillage, starting from the initial bulk density and the loads to be applied in the soil.
soil compaction; preconsolidation pressure; compression index; compression curve
