Physical quality of an oxisol under different uses

The use of a soil induces changes in the physical properties according to the management, tillage intensity and type of crop. The objective of this work was to measure the alterations of some of the soil physical properties and evaluate the physical quality by the S index, an indicator proposed by Dexter (2004), comparing the land uses: eucalyptus plantations at different ages, grazing pasture, annual crops, and an area of preserved secondary vegetation with an area of preserved native forest (National Forest Araripe - NFA) as control. The study was carried out on an Oxisol on the Fazenda Redenção, in Jardim, State of Ceará, Brazil. The experiment was arranged in a completely randomized design with seven treatments and three replications in the layers 0-0.1 and 0.1-0.2 m. The soil was analyzed for the following physical properties: bulk density, particle density, total pore volume, micro and macroporosity, soil water retention curves and water availability. Based on the S index, the hypothesis that the use of a soil deteriorates the physical quality was accepted. Clearly, native forest (NFA) was the land use with the best conditions in all physical properties studied, followed closely by the area reforested with 20 year-old eucalyptus. The use as grazing pasture affected the soil physical conditions most, especially in the surface layer (0-0.1 m), as evidenced by increased bulk density and a substantial reduction in soil porosity, mainly in macroporosity. Microporosity was not influenced by any of the uses and in any layer studied.