Agregação e matéria orgânica como indicadores de qualidade e sustentabilidade do solo no cerrado do leste maranhense

Abstract

The classification of soil aggregates based on their formation pathway, combined with the analysis of physical, chemical, and biological attributes, has proven to be an efficient tool for assessing soil quality and sustainability. In this context, this study integrated a systematic literature review and experimental field analyses to understand how different management systems and textural relationships influence the genesis of aggregates in soils of the Brazilian Cerrado, as well as their edaphic attributes. The systematic review was conducted in the Scopus, Web of Science, and ScienceDirect databases, resulting in 233 studies, of which 19 met the selection criteria. The results indicated that conservation practices and agroforestry systems, especially in finer-textured soils, favor biogenic aggregation and the maintenance of carbon and nutrient stocks. In contrast, conventional systems and intensive pastures tend to intensify physiogenic aggregation, associated with greater carbon losses and soil structure degradation. The field study was carried out in April 2024 at Fazenda Barbosa, in Brejo (MA), covering three representative land-use areas: Native Cerrado (CN), Perennial Pasture (PP), and Crop-Livestock Integration (ILP). Physical attributes (bulk density, total porosity, micro- and macroporosity, mean weight and geometric diameter under dry and wet conditions, and aggregate stability index), soil macrofauna, the classification of aggregates into biogenic and physiogenic, as well as chemical analyses (pH, P, K, Ca, Mg, Al, and H+Al) and the physical fractionation of organic matter within aggregates according to their formation pathway, were evaluated. Among the systems assessed, ILP showed the best results in chemical attributes, greater macrofauna diversity, and higher accumulation of organic carbon in more stable forms. Additionally, it was closer to CN in the physical attributes of the surface layer (0 0.05 m), highlighting its conservation potential. PP, in turn, contributed positively to soil fertility, showed higher biological diversity and uniformity, and promoted more significant physical improvements in the 0.05 0.10 m layer, standing out for the higher proportion of biogenic aggregates at this depth. Overall, all systems favored biogenic aggregation, which is efficient in carbon accumulation, reinforcing the importance of conservation practices for the sustainability of Cerrado soils. The indicators used demonstrated sensitivity and effectiveness in assessing the impacts of land use on soil quality in Eastern Maranhão, allowing the identification of both the potential and the limitations of different management systems. Taken together, the findings of the systematic review and the experimental study demonstrate, albeit with particularities, that conservation practices constitute effective strategies to stimulate the biogenic pathway of aggregation, improve soil quality, enhance carbon sequestration, and contribute to climate change mitigation across different Brazilian biomes.