Soil physical degradation is one of the main factors responsible for water erosion. The conventional tillage usually acellerates this process because it involves an intense soil tillage. Thus, no-tillage is considered a soil conservation management system because it preserves crop residue on the soil surface, inducing soil organic matter increase. However, no-tillage may also increase soil density and decrease surface soil total porosity. This study was conducted in Lages, SC, Brazil, on a Haplumbrepts soil, from May 1995 to November 1997. Two soil tillage treatments were used: conventional tillage (plowing plus disking) and no-tillage. Each soil treatment was replicated four times. The crop sequences used were oat, maize, oat, maize and oat in no-tillage system and oat, maize, fallow, maize and fallow in conventional tillage system. Soil bulk density, organic carbon, macroporosity, microporosity, total porosity and the ratio between macroporosity and total porosity were evaluated at soil layers of 0-2.5, 2.5-5.0, 5.0-10.0 and 10.0-15.0cm depth. Under no-tillage, there were higher values of soil bulk density and lower values of macroporosity and the ratio macroporosity/total porosity at the superficial layers of 0-2.5 and 2.5-5.0cm. Conversely, soil bulk density decreased with depth in the notillage treatment, thus enhancing macroporosity and the ratio between macroporosity and total porosity at the deeper layers of soil profile. An opposite trend was observed for the conventional tillage.
bulk density; porosity; organic carbon; soil structure
