SOIL AIR PERMEABILITY IN A RHODIC HAPLUDOX UNDER DIFFERENT TILLAGE SYSTEMS

Air permeability (K-alpha) can be used to assess soil structure changes resulting from different tillage systems. This study tested the hypothesis that the reduced soil disturbance in no-tillage results in continuous pores and better soil aeration conditions. The objective was to evaluate the aeration of a Rhodic Hapludox under conventional tillage (CT) and no-tillage (NT), based on soil air permeability (K-alpha), air-filled porosity (epsilon(a)) and indices of pore continuity (K-1 and N). Eighty undisturbed soil cores (2 treatments x 2 depths x 20 repetitions) were collected from each tillage system at 0-0.10 and 0.10-0.20 in in an experimental area of the Agronomic Institute of Parana in Ponta Grossa, Parana. After the samples had been saturated and equilibrated at six matric potentials (-2, -6, -10, -30, -70, and -100 kPa), the air permeability and air-filled porosity were determined for each matrix potential. The soil bull? density, particle density, organic carbon and soil porosity were also evaluated. Soil bulk density was not a limiting factor, with values below the critical limit for clay soils in both systems. In NT, the greater micropore volume was related to higher water retention in the evaluated moisture range (-2 to -100 kPa) and greater volume of pores blocked for air flow (epsilon(b)), thus reducing Ka in this system. At 0-0.20 m, the indices of pore continuity (K-1 and N) indicated more continuous pores in CT than NT, contradicting the hypothesis tested.