Soil quality index for extensive pastures in hilly landforms region of highly weathered soils in an Atlantic forest biome, Brazil

Abstract

Extensive pasture systems established in highly weathered tropical soils on steep slopes are vulnerable to soil degradation. Soil degradation can be monitored using an soil quality index (SQI). The SQI can assess both environmental aspects and indices related to pasture productivity within specific environments. A framework to evaluate and map a soil quality index for Ferralsols was developed in this study, emphasising pasture quality and seasonal variations, as well as geologic–geomorphological influences. Ground cover was determined in pasture areas with different levels of degradation. A minimum data set associated with pasture quality and productivity was selected by partial least squares regression to generate the SQI. The SQI is controlled by geomorphology and geology. In highlands, Ferralsols that develop in the oldest surfaces show strong leaching of basic cations and have higher acidity and, although components of organic matter increase, they are less important to pasture quality. In lowlands, landscape dissection exposes less weathered saprolite, forming Ferralsols with good chemical properties. This favours sustainability in pasture systems and reduces soil degradation in vulnerable environments. Soil quality indices were able to better evaluate pasture quality when established in summer.

Keywords: multivariate analysis; pasture management; soil degradation; soil fertility; soil organic matter; soil variability