Microestruturas de vertissolos em litossequência do semiárido brasileiro: contribuições ao estudo das origens e evolução pedológica

Present in the Brazilian Semiarid region, Vertisols are soils that have a vertic horizon and are made up of mineral material and small textural variation along the profile. They have a plastic consistency due to the presence of high activity clays. During its moistening and drying cycle, the phenomena of soil contraction and expansion occur, which leads to the development of features such as cracks, slickensides and gilgai. This work sought to contribute to the advancement of knowledge related to the genesis of two Vertisol profiles in the Brazilian Semiarid region, formed from different lithologies, located in the region of Madalena, Ceará. As a basis for this study, soil micromorphology techniques were used. From a more specific perspective, it was also possible to: i) identify, describe and analyze the genetic meaning of micromorphological features present in thin sections; ii) compare the mineralogy of these different source materials, both developed in the Brazilian Semiarid region. The technique used to collect undisturbed samples followed the concepts of Castro and Cooper (2019), samples were collected from both profiles after opening the trenches. The collected soils were placed in transport boxes and sent to the “Luiz de Queiroz” College of Agriculture - ESALQ/USP, in Piracicaba/SP for subsequent impregnation in thin sections in the Soil Micromorphology laboratory of that institution. The slide analyzes were carried out at the Pedology Laboratory of CODAGEO - Geography Coordination of IFMG - Federal Institute of Education, Science and Technology of Minas Gerais, Ouro Preto campus. After the micromorphological descriptions and analyzes of the slides, the high presence of altered minerals, organic nodules and zones of ferruginization were noted, as well as the processes of ferruginization, carbonation and bissialitization. Thus, micromorphological analyzes indicated that the mineralogical constitution of the source materials, the pedogenetic processes found and the Brazilian Semiarid climate contributed to the formation of Vertisols in the city of Madalena, Ceará.