Pedogênese de espodossolos em ambientes da formação Barreiras e de restinga do sul da Bahia

• Autor(a) principal: Oliveira, Aline Pacobahyba de
• Data de Publicação: 2007
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/5544
• topic: Espodossolos; Barreiras; Restinga; Pedogenesis; Barreiras; Sandbank; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::CIENCIA DO SOLO

In areas of the Barreiras and sandbank on southern Bahia, the occurrence of Spodosols that are much differentiated morphologically is common. In the sediment domains of the Barreiras formation in this region, it is common to observe an edaphologically differentiate environment and locally co-called "muçununga" which occurs in depressed areas of the Tabuleiros Costeiros and flood in the rainy season. In those muçunungas, one may observe the Spodosols with horizon E (white muçunungas) and without this horizon (black muçunungas), that show characteristics differing among each other and in relation to those found in the sandbank. Because the shortage of studies on Spodosols in Brazil, there is a need for knowing their physiochemical characteristics in order to get a better understanding of its genesis in those environments. So, this study was carried out to accomplish the chemical, physical and mineralogical characterization of those soils and to evaluate the possible differences in the Spodosol formation processes of both Barreiras and sandbank on extreme southern Bahia. Eight soil profiles with spodic materials were described and collected. Then, the following procedures were performed under laboratory conditions: selective extractions of either iron and aluminum by sodium dithionite-citrate-bicarbonate (DCB) and the ammonium oxalate and sodium pyrophosphate, characterization and fractioning of the organic matter and extraction of the low molecular weight organic acids, mineralogical by x-ray diffractometry in the clay, silt and sand fractions of the spodic horizons in the soils under study, and physical analyses for textural characterization. The analysis for visualization and obtainment of the photographs by optical microscopy were also performed in the coarse sand fraction. In Barreiras environment, the Spodosols showed fragipan below the spodic horizons. The white muçunungas showed a cemented spodic B horizon, whereas the black ones show small granular structure with dark coloration from the surface. Besides presenting sandy texture and increased clay contents in the spodic horizons, those are acid, distrophic and alic soils. So-called H + Al, the CTC is basically represented by the organic matter. The results obtained by the sulfuric attack to TFSA show relatively higher silica contents in the fragipans of the profiles, but low Fe and Al contents, so suggesting destructed clay in the cohesive Yellow Ultisols that occur surrounding the Spodosols in Barreiras areas. The soils show accumulation of organic matter, mainly both fulvic and humic acids and the Al and Fe oxides in the spodic B horizons B. The participation of Al is more accentuated in relation to Fe in the podzolization process, as well as that of the poorly crystallized forms in relation to those with better crystallinity. So, the brown and dark coloration found in those soils seems to be more related to the organic compounds than to the iron oxides. In the analysis for determination of the organic acids with low molecular weight, the occurrence of the acids (acetic, butyric, succinic, malic, malonic, tartaric, and oxalic) were verified, and the acetic, butyric and succinic acids showed the more expressive values, therefore they are probably contributing to the Spodosol formation process, when together with other organic materials they promote the solubilization and translocation of the ions along the profile, therefore favoring the accumulation of the organometallic complexes as a function of depth, consequently the formation and development of the spodic B horizons. The main components at the mineral phase of the clay fraction in the spodic horizons are the minerals caulinite and probably the vermiculite with inter layers hydroxy (VHE), as being the last one at very low amounts. Quartz, mica and caulinite traces were observed in the silt fraction, but only quartz in the sand fraction. Chemical physical, morphological and mineralogical differences were found in the Spodosols of both Barreiras Formation and sandbank. The white and black muçunungas showed only morphologic and chemical differences among each other.