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Universidade Federal de Viçosa (2016)

Gênese de solos com horizonte Bt no domínio gnáissico da depressão semiárida do Vale do Jequitinhonha, MG ;

Gonçalves, Mariana Gabriele Marcolino

Titre : Gênese de solos com horizonte Bt no domínio gnáissico da depressão semiárida do Vale do Jequitinhonha, MG ;

Genesis of soils with Bthorizonin gneiss area of semiarid depression of the Vale do Jequitinhonha, MG

Auteur : Gonçalves, Mariana Gabriele Marcolino ;

Université de soutenance : Universidade Federal de Viçosa

Grade : Mestre em Solos e Nutrição de Plantas 2016

Résumé
The Brazilian semiarid region occupies approximately 11, 5% of the national territory.Low and poor rainfall distribution with long periods of drought and high temperatures are characteristics that influence the soil formation which are different from those commonly found in warm and humid tropical regions.In the State of Minas Geraisthe semiarid occurs dominantly in the northern and occupies about 17 % of the territory, with great diversity of soils.The class of Alfisols, for example, has a small geographical expression and occurs only in the northeast of Minas Gerais, near the border with the state of Bahia. Although most studied in the semiarid region of northeastern states, few studies that consider the chemical, physical, mineralogical and micromorphological soil with high or low activity clay and textural B horizon in the semiarid region of Minas Gerais. Thus, the objective of this research is to study the physical, chemical, mineralogical and micromorphologicalfeatures these soils to better understand their pedogenesis, especially Alfisols and Ultisols of Minas Gerais semi-arid.To this end, were selected, described and sampled soils of the following classes : Alfisols, Ultisols and Mollisols.After selection and soil sampling, analysis for characterization were performed.In addition to Na + , the Mg 2+ it seems influences on clay dispersion, contributing to the formation of columnar structure breaks in angular blocks and subangular of soils studied. These soils have a considerable reserve of nutrientsdue to the strong presence of easily weatherable primary mineralsas plagioclase, orthoclase and biotitein silt and fine sand fractions, contributing to eutrophic feature observed in all soils. The conditions of moderate drainageand low rainfallpermit the formation of 2 : 1 minerals (expandable or not), and it is corroborated by the high ki values of these soils (ki > 2.2).In Ultisolsand Alfisols significant correlation was foundbetween the iron oxide contentextracted by sulfuric acid attackand some trace elements analyzed by the total attack, reaffirming the geochemical affinity between Feand some of these elements. It was not found in the waxy soil field description with Bt and micromorphological analysis also did not indicate the occurrence of illuvial clay coatings, indicating that lessivagem was not the main process in the formation of Bt. The presence of stress-oriented clay suggest that elutriation and the formation of clay "in situ" better explain the genesis of the Bt horizon in the soils.

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Page publiée le 8 août 2017