Impact of short-term grazing on physical properties of Planosols in Northeastern Brazil

Abstract

This study evaluated the response of several physical properties and the organic carbon (OC) content in a sandy soil before and after grazing in Northeastern Brazil. Three Girolando heifers with a mean weight of 300 ± 5 kg were kept under a continuous grazing system in an experimental area of 40 × 40 m for 21 days. Soil cores were sampled before and after grazing, and the following soil physical–hydric indicators were determined: total porosity (TP), bulk density (BD), soil penetration resistance (PR), saturated hydraulic conductivity (K0), OC, gravimetric water content, and least limiting water range (LLWR). Intensity grazing resulted in changes to the physical–hydric attributes and OC. Compaction slightly increased, with a consequent reduction in the TP, K0, and LLWR. The reduction of K0 did not decrease to critical levels that caused limitations in soil aeration and drainage. The reduction of the LLWR, due to grazing, was caused mainly by an increase in the limiting PR (i.e., PR > 2.0 MPa), which is likely to cause root growth limitation with high BD levels. In sandy soil, the LLWR is naturally narrow because of the low water retention capacity (field capacity) of this soil, but it could decrease further as a result of the compaction caused by grazing, becoming close to zero.