Adsorção do fósforo em solo sob recuperação florestal após mineração de bauxita em Paragominas, Pa

Abstract

The comprehension about the phosphorus (P) availability and retention in reconstructed soils under forestry recovery process after bauxite mining is important as a tool in the taking of decision with regard to the management of such nutrient. The aim of this study was to assess the adsorption of P in a reconstructed soil as a function of forestry recovery processes after bauxite mining, as well as its relation with some soil chemical and vegetation attributes. The study was performed in a bauxite exploration area in the municipality of Paragominas, PA. In this area, three systems were evaluated: native forest (FLO), as witness, Traditional planting of seedlings (PLT) and natural regeneration of vegetation (RNV). In each system, eight plots were implanted. In each plot, soil samples were collected at depths 0-5, 5-10, 10-20 and 20-40 cm, for fertility and phosphorus adsorption analyzes (P), and an inventory of the vegetation was carried out. All data were submitted to analysis of normality, homoscedasticity, variance, comparison of means and multivariate analysis, all at 5% significance. Regarding soil fertility attributes, FLO was higher, followed by RNV and by PLT, for most attributes. The diversity of forest species in PLT, with an index of 1.70 + 0.30, was significantly higher than the RNV, with a rate of 0.61 + 0.41, although there is a larger basal area RNV (1.31 + 1.60 m² ha-1) than in PLT (0.14 + 0.11 m² ha-1), in the lower stratum. In general, the adsorption curves and the maximum adsorption capacity of P in the soil followed the order PLT> RNV> FLO. There was a higher negative relation of the phosphorus adsorption with the organic matter content, with the CTCpH7 and the available P of the soil. This indicates the importance of the conservation and maintenance of the biomass, aiming at guaranteeing greater availability of P and avoiding the use of phosphate fertilizers, besides or less than necessary, in recovery practices. In addition, such results demonstrate that species diversity should not be the only factor to be taken into account, but also the soil cover when selecting species for recovery.