PHYSICAL, CHEMICAL, AND BIOLOGICAL QUALITY IN AN OXISOL UNDER DIFFERENT TILLAGE AND FERTILIZER SOURCES

Soil quality (SQ) assessment is an important strategy for defining management practices and systems capable of maintaining and/or improving the sustainability of agricultural systems. Thus, the aim of this study was to evaluate changes in SQ by physical, chemical, and biological indicators in an Oxisol under different tillage systems and fertilizer sources. The study was conducted in Taquarucu do Sul, RS, Brazil based on an experiment set up in 2009 in a randomized block design with four replications. The treatments studied were tillage systems (no-tillage, minimum tillage, and chisel plowing) associated with different fertilization practices (without fertilization, 80 m(3) ha(-1) of pig slurry, and mineral fertilizer). It was used as reference the soil of an area of native forest, adjacent to the experiment. Undisturbed and disturbed soil samples (0-10 and 10-20 cm) were taken to analyze the chemical, physical, and microbiological soil indicators, and Provid traps were installed to assess biological soil indicators. The soil physical indicators, bulk density, soil penetration resistance, macroporosity, and total porosity proved to be sensitive to changes in the soil caused by agricultural use compared to native forest. In contrast, physical-mechanical properties are not recommended for SQ assessments. Organic matter is the indicator most responsive to SQ degradation; however, the effects from soil tillage are not manifested in three years of study. Fertilization with 80 m(3) ha(-1) of pig slurry under no-tillage favors macrofauna diversity and microbial activity in the soil, and it constitutes an important soil management strategy in southern Brazil.