The objective of this study was to determine the effect of soil tillage systems, moldboard plough, harrow disc and no-tillage, on the variability of some soil physico-chemical properties. The study was conducted in a clayey Oxisol, subjected to different soil tillage systems for five consecutive years and cultivated with corn in the summer and bean in the winter. Forty nine soil samples were collected from a grid 7x7 lattice sampling area spaced 4x4 m at 0-5 cm and 5-20 cm soil depth. The values of Cu, Zn, Fe, Mn, B, organic matter and clay contents of soil varied for different treatments. The Cu, Mn, B, organic matter and clay content values were higher in the 0-5 cm soil depth in no-tillage treatment. Among the soil chemical properties evaluated, the concentrations of Cu and Zn showed the highest variability, whereas organic matter and clay contents had the lowest. In 20 samples analyzed, the variables clay, organic matter, B and Mn were estimated with an error of 10% of the actual value. For Cu and Zn, the mean variation using the same procedure reached over 25%.
mouldboard ploughs; disc harrows; direct sowing; soil fertility
