Formas de fósforo e solos com sedimentos fossilizados, Alto Solimões, Amazonas

Abstract

In the Amazon Region, terra firme soil environments are naturally poor in phosphorus, the most common classes being Oxisols, Argisols and Plinthosols. There are some exceptions of soils with high natural fertility, such as the Eutrophic Luvisols of Acre. In recent years, very high P Mehlich-1 values have been found in the Alto Solimões region, which sparks interest in understanding its genesis/origin. Thus, the main objective of this work is to understand the genesis and origin of phosphorus (elevated melich-1). Through fractionation; extract phosphorus Resin and Melihch -1 and total phosphorus, present in soils with fossilized sediments of the Solimões Formation. The study area is located in the Alto Solimões Region, in the Municipality of Benjamin Constant, Amazonas, in a previously evaluated profile. In this, samples were collected only in the Ap, Bi and C1B horizons, (where the highest levels of P Melich-1 are included). After collection, the samples were conditioned in air-dried fine earth, and the following analyzes were performed: P Melich-1, according to the methodology described by Embrapa, P-resin as described in the cation and anion exchange resin method and quantified by colorimetric method. And the fractionation, performing sequential extractions in P-Labil, P-Al, P-Fe P-Ca, and P-residual. The final results were interpreted and discussed, so it is possible to say that P-Ca is the most abundant form followed by P-Al and P-Fe. These results indicate that the high values of P available in these soils are of biogenic origin (fossilized shells). These shells, being material of low stability, are undergoing dissolution and increasing P values in the soil, probably transforming into a more stable form such as P-Al and P-Fe. Occurrence of shells in the current landscape of Alto Solimões, indicates a period of formation of lakes, isolated or partially isolated, which dried and deposited fine sediments (siltstones and claystones) impregnated by shells, forming varied depositions of shells, becoming fossilized, is still little known to science.