Caracterização de solos arenosos sob Campinaranas da região de Manaus e Presidente Figueiredo (AM)

Abstract

Amazonas has the most significant areas of sandy soils in Brazil, which have environmental importance once they are associated with the occurrence of Campinaranas. Economically these areas are also important as they are the primary source of sand mining for the construction industry in the metropolitan region of Manaus. Efforts to expand knowledge and develop technologies to restore sandy soils near urban centers are essential, once exploratory activities had more impact on these areas. This research aimed to characterize and classify sandy soils under Campinaranas vegetation in Manaus and Presidente Figueiredo (AM). Soil profiles were opened in five areas of sandy soils under Campinaranas, to describe their morphological and physico-chemical characteristics. Soils were classified as NEOSSOLO QUARTZARÊNICO Órtico típico (P01, P02 and P03), ESPODOSSOLO HUMILÚVICO Órtico dúrico (P04), and NEOSSOLO QUARTZARÊNICO Órtico espodossólico (P05). Soils were characterized by loose to friable consistency, sandy loam to sand texture, with fine sand predominant, low clay contents, low density, and high porosity. Quartz was the only mineral identified in the sand fraction, whose grain morphology showed subangular roundness with high sphericity. Soil pH ranged from strongly acidic to extremely acidic, H+Al and Al3+ concentrations were higher on the surface and lower in the sub-soil, except in the Bh horizon (P04). The concentration of total organic carbon was higher on the surface and Bh, which is directly correlated with the Al3+ concentration. CEC was also higher in the top layers, Bh (P04) and C4+ (P05). Al2O3 and Fe2O3 crystalline concentrations were higher than Al2O3 and Fe2O3 amorphous, especially in the Bh horizon (P04) and in aggregates structures of organic matter + sand randomly distributed in P03. This data shows the process of podzolization and indicates that Al is an important factor in the formation of spodic horizons in these soils.