Researchers have suggested soil organic matter (SOM) as a key indicator of soil quality (SQ), due to its positive influence in other important soil attributes. With the objective to evaluate the potential use of SOM as an indicator to select soil management systems, two long-term experiments carried out on Paleudults in southern Brazil were used. In the first ten-year experiment located in Santa Maria (Rio Grande do Sul State, Brazil) at the Federal University of Santa Maria, five treatments composed of three crop systems (winter fallow/corn, rye+vetch/corn and velvet bean/corn) under no-tillage, bare soil and native vegetation were selected. In the second experiment that was 15-years-old, in Eldorado do Sul (Rio Grande do Sul State, Brazil) at the Federal University of Rio Grande do Sul, the following treatments were selected: black oat/corn under conventional tillage without nitrogen fertilization and four other treatments consisting of soil tillage systems (conventional, reduced and no-tillage) with black oat/corn, and black oat + vetch/corn + cowpea under no-tillage. The last four latter treatments received N fertilization at an average rate of 144 kg ha-1, applied to corn. In this experiment native vegetation (undisturbed) and pigeon pea/corn under no tillage with N fertilization of 144 kg ha-1 applied to corn were used as reference treatments. In both experiments the treatments were ranked based on expected SQ. Total Organic Carbon (TOC) and Total Nitrogen (TN), TOC and TN in soil fractions above and below 53 µm, potential of carbon and nitrogen mineralization and microbial biomass were evaluated. Only the 0-5 and 0-20 cm deep layers were considered. Soil management impacted SQ in both experimental areas. The soil attributes TOC and TN at 0-5 cm depth were effective to discriminate the impact of soil management systems on SQ, in line with the expected ranking in both areas. Among the SOM fractions, that > 53 µm was the most sensitive to discriminate SQ alterations induced by soil management systems.
total organic carbon; cover crops; soil conservation
