Long-term effects of no-tillage on dynamic soil physical properties in a Rhodic Ferrasol in Parana, Brazil

No-tillage has been adopted worldwide as a strategy to reduce the negative effects of soil erosion in conventional tillage. However, no-tillage can lead to over-compaction of the soil, which can have detrimental effects on soil structure and on crop yield. The objective of this study was to evaluate the soil physical functionality of a Rhodic Ferrasol under long-term no-tillage. The following physical properties were measured: dry bulk density (Db), total porosity (Pt) and macroporosity as well as saturated hydraulic conductivity (K-sat) and intrinsic air permeability (K-a). Physical quality of the soil was also evaluated by the S index at each depth increment. The study was carried out in a Rhodic Ferrasol under a 14-year old, no-tillage system in Ponta Grossa, Parana, Brazil. Undisturbed soil samples were collected at depths of 0-0.10, 0.20-0.30, 0.40-0.50, and 0.60-0.70 m. The soil properties such as dry bulk density, total porosity and macroporosity showed the presence of a denser layer at a depth of 0.20-0.30 in. The Db and Pt values in this layer were significantly different from the other layers. However, the values of 1.23 Mg m(-3) for Db, 0.52 m(3) m(-3) for Pt, and 0.17 m(3) m(-3) for macroporosity were all still adequate for the growth and development of roots at this layer. The values of K-sat and K-a were higher at the surface layer than deeper layers. The lowest values were around 80 and 70% in comparison with surface, respectively to the depths of 0.40-0.50. and 0.60-0.70 in K-sat and K-a values were 7.79 x 10(-5), 2.76 x 10(-5), 1.58 x 10(-5), and 1.91 x 10(-5) m s(-1), and K-a values were 3.70 x 10(-11), 2.04 x 10(-11), 7.69 x 10(-12), and 1.10 x 10(-11) m(2) for the depths of 0-0.10, 0.20-0.30, 0.40-0.50, and 0.60-0.70 m, respectively. This demonstrated that better conditions for the exchange of gases and water existed in the layers above 0.30 m. The S index indicated that the soil had good structure in all layers studied, with values above 0.035, but that a small increase in Db in the 0.20-0.30 m layer could lead to deterioration of the soil structural quality. The long-term use of no-tillage resulted in increases of organic carbon and pore connectivity in the surface layer, providing functionality in the soil. (C) 2008 Elsevier B.V. All rights reserved.