The effects of soil use and management on soil physical quality have been largely discussed due to its environmental and agronomic impacts. The least limiting water range (LLWR) is a modern indicator of soil physical quality that can indicate processes and mechanisms linked to soil physical degradation caused by soil use and management. The aim of this work was to quantify the influence of different land uses and soil tillage on the LLWR of an Oxisol (170, 40 and 790 g kg-1 clay, silt and sand). Four areas were selected: native forest; planted pasture for more than 20 years; area under citrus cultivation for more than 10 years; area with annual crops (corn, sorghum, oat, and cassava) for 15 years after 10 years of pasture. In each treatment, 48 undisturbed samples were collected in the 0-0.10 m layer. A matric potential of -10 to -15,000 hPa was applied and the soil samples were analyzed for soil bulk density (Bd) , water retention curve, soil resistance curve, LLWR, and critical Bd. Bulk density was influenced by soil use and management at the following sequence commercial crops = citrus > pasture > native forest. The relationship between LLWR and Bd was linear and negative, except under native forest, where the Bd range (1.35-1.55 Mg m-3) had a positive relationship. In the areas under citrus and annual crops, LLWR reached zero, with a critical bulk density (Bd c) of 1.75 and 1.80 Mg m-3, respectively, with severe soil physical degradation. The ratio of these values was 21 % for soil under citrus and 18 % for soil under commercial crops. The loss of soil physical quality was less marked for the soil under pasture than citrus and annual crops, with a less pronounced decrease of LLWR with increasing Bd a. The lowest Bd value, at which the reduction of LLWR begins, was named alert bulk density (Bd a). The Bd was 1.55 Mg m-3 and can be used as a reference value for the process of soil regeneration, valid for soils with soil texture and soil use and management similar to this study.
soil bulk density; soil structure; soil resistance to penetration; soil water; soil physical quality
