Soil Quality Evaluation Using the Soil Management Assessment Framework (SMAF) in Brazilian Oxisols with Contrasting Texture

The Soil Management Assessment Framework (SMAF) was developed in the U.S.A. and has been used as a tool for assessing and quantifying changes in soil quality/health (SQ) induced by land uses and agricultural practices in that region and elsewhere throughout the world. An initial study using SMAF in Brazil was recently published, but additional research for a variety of soils and management systems is still needed. Our objective was to use data from five studies in southern Brazil to evaluate the potential of SMAF for assessing diverse land-use and management practices on SQ. The studies examined were: (i) horizontal and vertical distribution of soil properties in a long-term orange orchard; (ii) impacts of long-term land-use change from native vegetation to agricultural crops on soil properties; (iii) effects of short-term tillage on soil properties in a cassava production area; (iv) changes in soil properties due to mineral fertilizer and pig slurry application coupled with soil tillage practices; and (v) row and inter-row sowing effects on soil properties in a long-term no-tillage area. The soils were classified as Oxisols, with clay content ranging from 180 to 800 g kg. Six SQ indicators [pH(H2O), P, K, bulk density, organic C, and microbial biomass] were individually scored using SMAF curves and integrated into an overall Soil Quality Index (SQI) focusing on chemical, physical, and biological sectors. The SMAF was sensitive for detecting SQ changes induced by different land uses and management practices within this wide textural range of Brazilian Oxisols. The SMAF scoring curve algorithms properly transformed the indicator values expressed in different units into unitless scores ranging from 0-1, thus enabling the individual indicators to be combined into an overall index for evaluating land-use and management effects on soil functions. Soil sector scores (i.e., chemical, physical, and biological) identify the principal soil limitations and can therefore be used to establish priorities for specific management actions. The SMAF can be used as a tool for assessing SQ in Brazilian soils, thus helping farmers, land managers, and politicians make better decisions regarding sustainable land-use and management practices.