AIR PERMEABILITY OF THE SOIL SEEDBED UNDER A NO-TILLAGE SYSTEM

Air permeability may be used as a soil physical quality indicator. The objective of this study was to determine the air permeability and pore continuity index for the seedbed of an Oxisol cultivated under a no-tillage system that underwent mechanical chiseling and biological promotion of pore formation using the forage radish crop. The study was carried out in an experimental area of the Universidade Estadual de Ponta Grossa (Ponta Grossa State University), Parana, Brazil. The treatments were 18 consecutive years under no tillage (SD); no-tillage under mechanical chiseling (SDE); and no-tillage under biological promotion of pore formation by a forage radish cover crop (SDNF). A randomized complete block experimental design was used with four replications. Soil samples were taken at the 0.00-0.05 and 0.05-0.10 m soil depths at 6 and 18 months after setting up the treatments, corresponding to maize (October 2009) and soybean (November 2010) planting, respectively. Air permeability was determined with a constant head permeameter at four matric potentials: -6, -10, -30, and -100 kPa. The following pore continuity indices were determined: N index, K1 index, and blocked porosity; and air-filled porosity. The results were subjected to analysis of variance and, when significant, the means were compared by the Tukey test (p<0.05). For the 0.00-0.05 m soil depth, the air permeability and K1 index in SDNF at the -6 kPa matric potential were significantly higher than in SD and SDE. The N index, blocked porosity and air-filled porosity did not differ statistically among treatments for either depth. The beneficial effects of biological promotion of pore formation on air permeability and on the soil pore continuity index (K1) continued at 18 months after application. Mechanical chiseling resulted in greater continuity of the soil pore system (K1), and this effect persisted at 18 months after application.