Variables related to soil fertility in successional agroforestry systems – Serras do Sudeste, RS, Brazil

Abstract Successional agroforestry systems have the capacity to increase soil fertility and restore degraded ecosystems. The objective of this study was to investigate the influence of agroforestry systems, at different stages of ecological succession, on the dynamics of chemical and physical soil fertility attributes in the Brazil South region. Soil samples were collected under five different conditions: i) Control (T) = initial system (without agroforestry); ii) SAF1 = agroforestry with 1 year of development; iii) SAF3 = agroforestry with 3 years of development; iv) SAF7 = agroforestry with 7 years of development; and v) reference system (naturally regenerating forest with 30 years). Subsequently, determinations/calculations were carried out for chemical attributes/parameters (exchangeable Ca+ 2, Mg+ 2, K+, Na+, P, Al+ 3, H+, sum of bases, effective and potential cation exchange capacity, cation exchange saturation with bases and Al+ 3), physical attributes (soil bulk density, particle density, total porosity, and moisture), and soil physicochemical properties (pH H2O, pH in saline solutions, and SMP method), as well as chemical element stocks were calculated based on soil mass in each sampled layer. Results indicated an increase in pH, total porosity, and nutrient stocks with the systems' development time, accompanied by a decrease in acidity components. The change in soil fertility is directly related to the increase in soil organic matter content.