Qualidade do solo em diferentes condições de uso no semiárido paraibano.

Abstract

In the semiarid, because of climate, soil, and vegetation peculiarities, added to human action without planning, it is necessary to conduct several studies attempting to identify management techniques for regional agricultural ecosystems focused on sustainability. The monitoring of soil quality attributes is an activity of great importance in the sustainability of agricultural ecosystems, because through it you can evaluate whether the management is adequate. Thus, the purpose of this study was to assess physical and chemical properties of soils in agricultural areas under different usage conditions in the town of São João do Cariri, in the state of Paraíba, under the influence of the desertification process. Three areas were selected: native vegetation, cultivated vegetation, and vegetation under degradation process. Soil samples were collected at depth levels between 0-5, 5-10 and 10-20 cm from the main type of soil identified in the region, classified as Alfisol. Analyses of chemical variables were performed (pH, P, K+ , Ca2+, Mg2+, Al3+ Na⁺, potential acidity and organic matter) and physical variables (soil and particle density, total porosity, aggregate stability) and physical fractionation of organic matter. In the physical determinations, the results showed that despite the amounts of sand, silt and clay have differed among the areas, the textural classification of the soil was Sandy Loam. The amount of clay in the area of native vegetation was higher than in the cultivated area, while, in turn, the amount of sand was greater in the cultivated area and lower in the degraded and cultivated areas, respectively. Water dispersible or natural clay was higher in the area with native vegetation. The dried macroaggregates were higher in the area with native vegetation compared to the degraded area, although they did not differ statistically. In the chemical determinations, organic matter content in the area with native vegetation was higher than in the cultivated and degraded areas respectively. This result occurs due to the preservation and higher quantity of forest residue, as well as the absence of tillage. The values of Ca and Mg tended to be higher in the native vegetation area and lower in the cultivated area. The levels of P and K were also higher in the native vegetation area, but much lower in the degraded area. The longer the land was used, the more alterations there were in the physical and chemical properties of the soil.