Monitoring soil quality changes in diversified agricultural cropping systems by the Soil Management Assessment Framework (SMAF) in southern Brazil

Assessment and monitoring impacts of agricultural systems on soil quality are imperative to establish best management practices and sustainable land use for mitigating climate change, conserving biodiversity and achieving food and energy security. The SMAF has successfully been tested as an objective tool to quantify land use and management effects on soil quality, including under some Brazilian soil conditions. Nevertheless, the SMAF potential to properly address soil quality changes under contrasting soil and climate conditions, and integrated farming systems must still must be investigated. Thus, a field study was conducted to apply the SMAF guidelines as a strategy for assessing land use (native vegetation, pasture, sugarcane, no-tillage, and integrated crop-livestock systems) effects on soil quality in southern Brazil. Soil samples were taken in three layers (0.0–0.10, 0.10–0.20, 0.20–0.30 m) of clay Ferralsol (traditional agricultural region), Sandy loam Ferralsol and Arenosol (new agricultural frontiers), in the state of Paraná, Brazil. The soil quality indicators investigated were: chemical attributes (pH, phosphorus and potassium), physical (bulk density) and biological (soil organic carbon). Using the SMAF scoring curves, the measured values were transformed (0 to 1 range) and an overall soil quality index (SQI) was calculated. Our findings revealed that long-term conversion from native vegetation to agricultural land uses (i.e., pasture, no-tillage/integrated crop-livestock system, or sugarcane) reduced soil quality assessed by SMAF scores, compromising the soil’s capacity to perform its functions. Nevertheless, conservationist systems, e.g. the no-tillage, associated or not with the integrated crop-livestock system are promising alternative to enhances soil quality by increasing C content and soil chemical fertility compared to degraded pasture or conventional sugarcane cultivation. However, soil physical changes should be monitored to alleviate soil compaction in no-tillage cropping systems. In conclusion, this study provided important insights about soil quality changes induced by land use and diversified cropping systems. In that direction, new studies including a large number of sites, soil types and cropping systems are needed for validating our conclusions in a regional scale, enabling to support decision-making towards more sustainable expansion and intensification of agriculture in Brazil.