Soil organic matter and structural stability under different land uses in Sapezal, Mato Grosso, Brazil

Soil organic matter (SOM) plays a key role in the formation and stabilization of soil structure, influencing aggregate organization and soil physical quality. Changes in land use can alter SOM contents and structural stability, affecting the sustainability of production systems. This study evaluated the relationship between SOM and soil structural stability under different land uses in Sapezal, Mato Grosso, Brazil. The study was conducted in on-farm areas under Pasture, Integrated Crop–Livestock system (ICL), Soybean/Cotton rotation, and Native Forest (Cerradão/Amazon Forest) as a reference. Soil samples were collected from the 0–10 cm layer. SOM was determined using the Walkley and Black (1934) method, and aggregate stability was assessed by wet sieving (Yoder, 1936), expressed as geometric mean diameter (GMD) from three analytical replicates. Data analysis was descriptive and exploratory, comparing land uses and evaluating the dispersion between SOM and GMD. The highest SOM contents were observed in the Native Forest, followed by ICL and Soybean/Cotton systems, while Pasture showed the lowest SOM values. Structural stability was highest in Native Forest and Pasture, whereas agricultural systems presented lower GMD values. In general, land uses with higher SOM exhibited greater aggregate stability. However, the elevated GMD in Pasture despite lower SOM indicates that structural stability is not controlled exclusively by total SOM, but by interactions between SOM, land use and management. Reduced soil disturbance, grass root systems and animal trampling may contribute to the formation of mechanically stable aggregates.