Atributos quimicos em sistemas agroflorestais, pastagem e floresta no agreste paraibano

Abstract

The planning and use of natural resources, aimed at sustainable development, should be based on landscape characteristics. Therefore, this study aimed to comparatively evaluate soil fertility in agroforestry systems, pasture, and natural forest in the Agreste mesoregion of Paraíba. Geomorphic surfaces were identified and delineated according to topographic criteria. Subsequently, trenches were opened in each pedoenvironment of the toposequence, and their horizons and/or layers were defined for fertility characterization. The selected areas included: a) silvicultural system, b) agrosilvicultural system, c) intensive pasture area, and d) natural forest area. In these locations, soils were sampled at fifteen equidistant points in each layer per environment, totaling 60 points and 120 samples. These sites were georeferenced using a GPS device, and the information was used to develop the altimetric profile. Samples were collected along the transect at depths of 0.00–0.10 m and 0.10–0.20 m, and analyzed for pH in water (H2O) and in potassium chloride (KCl), potential acidity (H++Al), exchangeable aluminum (Al3+), calcium (Ca2+), magnesium (Mg2+), phosphorus (P), potassium (K+), organic carbon (OC), and carbon stock (CS). In general, the soils of the Agreste mesoregion of Paraíba are slightly acidic due to the advanced stage of weathering associated with local rainfall patterns. Additionally, they contain clays predominantly composed of iron and aluminum oxides, which result in low cation exchange capacity (CEC) and low base saturation values. Overall, these soils exhibit good physical conditions for agriculture, with good permeability, strong structure, and high porosity, leading to high fertility.