Uso de técnicas de extração de fósforo em solos antrópicos da Amazônia

Abstract

The presence of the nutrient phosphorus in the soil can be used as indicators of daily activities or even the ancient fertility evaluation. Found throughout the Amazon basin, the Indian Black Earth or simply Black Earth (BE), a Antrosolo rich in nutrients, particularly phosphorus, has its origin attributed to the deposition of waste materials produced by the ancient peoples of the Amazon. Thus, phosphorus bound to organic matter (Po), iron (PFe), aluminum (PAL), calcium (PCa) and weakly bound (PFL), and consequences of this association on the Mehlich-1, Mehlich-3, Olsen and Bray-1 were studied in eight sites of BE in the State of Amazonas. The influence of extraction time on the four methods was also evaluated. Soil samples were collected at a depth of 0-20 cm, in eight sites of BE, distributed in the municipalities of Barreirinha, Itacoatiara, Parintins and Manaus. The soil characterization was done by physical, chemical (pH, organic matter, Na, K, Ca, Mg, Al, Fe, Zn, Mn, Cu), texture (sand, silt and clay) and mineralogical (X-ray diffraction X). The total phosphorus, extracted and fractionated, and the kinetic study were determined by the ascorbic acid. The data were subjected to multivariate statistical analysis by hierarchical clustering (HCA), principal components (PCA) and analysis of variance. Despite the high variability of chemical attributes in all BE, the results show that concentrations of total phosphorus were similar to each other, except to the site Barreirinha. In terms of extracting it was observed that most of the BE sites obeys the following order: Mehlich-1>> Mehlich-3> Bray-1> Olsen. The sequence observed is directly related to the amount of PCa, although the high levels of Po prevails in almost all the BE. This fact was confirmed by PCA whose main components are PCa and Po and corroborated with the HCA with the formation of three distinct groups. The settings of the equation of desorption kinetics were best for Olsen and Mehlich-1 sites in Manaus and Barreirinha, clearly indicating that both methods depend directly on the extraction time. Finally, the results of this study suggest that the Mehlich-3 and / or Bray-1 are more suitable for studies of fertility, however, the Mehlich-1 to be able to differentiate between the BE itself is more suitable for the archaeological study match.