Solos com feições espódicas do Pantanal Sul-Mato- Grossense: Antagonismos às condições pedogenéticas

Abstract

In the Pantanal of Mato Grosso do Sul, spodic soils are registered, whose chemical characteristics are divergent from the central concept of pedogenesis by podzolization process. In this sense, the hypothesis of this study is that neutral to alkaline conditions of Pantanal pedoenvironment does not inhibit the development of spodic soils. So that, the objective is to evaluate characteristics and attributes of soils with spodic features from the Pantanal to fit in the podzolization process. Four soil profiles were selected in a transect, three in the bay area (P1, P2 and P4) and one in the transition area between bay and “cordilheira” (P3), whose morphology was indicative of the spodic horizon. The analysis of granulometry, chemical and X-ray fluorescence (XRF) of the soils, as well as organic carbon (C org) and XRF of the nodules, were carried out. All profiles have characteristics that denote the redoximorphism process: small development of the solum (except for P3), mottles formed by the precipitation of Fe and Mn oxides, as well as the presence of Fe and Mn nodules. These nodules have an organic matter content, in general, greater than or equal to the surrounding material and without a relative increase in aluminum in relation to the fine earth fraction, which reiterate the redoximorphism process in the horizons with spodic features of the Pantanal soils. The texture of the soils is substantially sandy, with a finer granulometry of the sand fraction, and, in the P3 profile, there is a horizon of low permeability and some clay accumulation. The occurrence of sodic and solodic characters in the soils, as well as the subsurface clay accumulation in the P3 profile indicate the occurrence of the sodification process. In the soils studied from Pantanal, the neutral to alkaline pH, the high sum of bases, low organic carbon and aluminum oxides, compared to other spodic horizons, contradict what is observed in soils formed by the classic podzolization processes. Hovewer, the accumulation of Fe, Al and C org, even if small, in the nodules and in the B horizons, characterize the spodic features in these soils.