The pressure applied by animal hooves can lead to soil surface compaction in a crop-livestock system (CLIS), with effects on soil physical quality. The hypothesis of this study was that the trampling of animals as a result of grazing on oat and ryegrass crops in a Latossolo Vermelho distroférrico (Oxisol) under no-tillage in a CLIS degrades soil physical quality. The aim of this study was to evaluate the effect of different grazing heights on soil bulk density (BD), total porosity (TP), macro- and microporosity, porosity in the soil macropore domain (PORp) and in the soil matrix domain (PORm), total soil aeration capacity (ACt) and soil matrix capacity (ACm), soil water and air storage capacity, and the least limiting water range (LLWR) of an Oxisol after seven years under CLIS. The area under study, located in Campo Mourão, PR, Brazil, was managed in a CLIS with a no-till system of soybean/corn in the summer and oat+ryegrass in the winter, which was used as forage for animal grazing. The treatments consisted of four grazing heights (7, 14, 21 and 28 cm) and a control (control). In each treatment, 36 undisturbed samples were collected at the 0.0-7.5 and 7.5-15.0 cm depths for determination of soil physical properties. The hypothesis of the study was confirmed as aeration was compromised from intensification of grazing. After seven years of CLIS, the grazing height of 7 cm resulted in reduction of soil physical quality as indicated by BD, TP, PORm, and number of samples with BD > the critical BD (BDc) in the 0.0-7.5 cm depth; and by macroporosity, ACm, Act, and air storage capacity in the 7,5-15.0 cm depth. With the increase of BD, restrictive values of aeration and resistance to penetration in the LLWR were found in all treatments and in the two layers, with the most pronounced effect in the 0.0-7.5 cm layer.
aeration; soil structure; least limiting water range; animal trampling; soil resistance to penetration
