Química, Física e Mineralogia de Solos Utilizados na Agricultura Familiar e na Fabricação de Cerâmica Artesanal em Itaobim, Médio Jequitinhonha, MG

• Autor(a) principal: Simões, Diana Ferreira de Freitas
• Data de Publicação: 2008
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/5488
• topic: Solo; Agricultura familiar; Escultura em cerâmica; Soil; Familiar agriculture; Ceramic Sculpture; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::CIENCIA DO SOLO

Located in the northeast of Minas Gerais state, the Mid Jequitinhonha occupies about 18 thousand km², corresponding to about 25 % of the total area of the Jequitinhonha valley. Its natural characteristics have distinct characteristics of climate, relief, geology, soil and land use. The main support of the regional economy are family agriculture, extensive cattle ranching and handcrafted pottery. Family agriculture is concentrated mainly in the Haplic Cambissoils of cropped slopes and Fluvial Neosoil located in the alluvial plains of the rivers Jequitinhonha, Araçuaí and some of their tributaries. In the areas of Haplic Cambissoils, small hill (murundu) micro reliefs are found that are also used for family agriculture, but little characterized. Although the crop yields are low, the farmers consider them satisfactory, suggesting the higher natural fertility of the soils. In addition to these soils, Planosoil and Gleysoils (barriers), depending on the horizon, are used to manufacture handcrafted pottery pieces. Thus the objectives of this study were to characterize physically, chemically and mineralogically the Fluvial Neossoilos, Cambissolos and Cambissolos with small hills, both Haplic, used in family agriculture along two toposequences and characterize the hydromorphic soils used to manufacture handcrafted pottery in the Pasmado community, municipality of Itaobim, MG. Nine profiles were selected and collected for the physical chemical and mineralogical characterizations, distributed in toposequence 1 (T1) consisting of two Haplic Cambisoils (P1 and P2), a Cambisoil with small hills (P3) associated to profile P2 and two Fluvial Neosoils (P4 and P5) and in toposequence 2 (T2), consisting of a Haplic Cambissoil (P6), its Cambissoil with small hills (P7) and a Fluvial Neosoil (P8) used for family agriculture. A Haplic Cambisoil profile (P9) was also collected that served as an extra sample and reference for this class. In addition, three `barrier´ profiles were used to manufacture handcrafted pottery. Granulometric analyses were carried out along with the water retention curve test and consistency limits for pottery soils; routine chemical analyses and total Ca, Mg, K, P, Co, Cu, Zn and Ni in the TFSA contents in the sand and silt fraction, Fe extraction for dethionite citrate bicarbonate (DCB) and ammonium exalate and mineralogical analyses by X ray difratometry in the clay, silt and sand fractions. Semi-structured questionnaires were carried out with the craftsmen and a manufacture flow gram was made of pottery up to its commercialization. The Haplic Cambissoils and Fluvial Neosoils presented medium texture and, or clay, texture, and there were high values of clay in the B horizon of the Cambissoils. The soils were slightly acid, eutrophic and dystrophic, suggesting that there is differentiation in the yields reached, even though the calcium magnesium and potassium contents were good and considered from medium to good in the surface horizons. Furthermore, the total and exchangeable contents of the sand and silt fractions, together with the clay fraction, seemed to be important sources of nutrients for the plants. The Haplic Cambissoils with small hills had greater silt and clay, Ca2+, P and organic carbon (CO) contents, indicating that termite activity, probably in the past, was important for its greater fertility compared to the Haplic Cambissoils to which they are associated. The minerology of the Fluvial Neossoils and Cambissoil clay fraction consists basically of kaolin and ilyte and the sand and silt fraction consists of mica, calcium and soda plagioclasium and potassium feldspars. The total chemical analysis of the TFSA fraction and the sand and silt fractions confirmed greater potassium contents in these soils. The horizons selected by the potters for handcrafted pottery manufacture have greater clay and silt contents, plasticity index (PI) and colloidal activity index (Ia), that are important for the end pottery quality. The small quantities of fine sand did not seem to be sufficient to promote a non-plastic effect on the Gleysoil, confirmed by its restricted use for the manufacture of some handcrafted pieces. With the increase in temperature in the pottery mass, the Feo/Fed decreased that led to questioning whether this can influence the quality of the end pottery product, especially in terms of resistance to breakage. The surface layers, because they are more sandy, and the subsurface layers, because of their hardness, are discarded even though in some cases the latter can be used to manufacture handcrafted pieces (C horizon). The mineralogical analyses of these soils indicate the presence of quartz, feldspar, plagioclasiums and mica in the sand and silt fractions, and kaolin and mica in the clay fraction. This aspect is relevant because of the small areas that the Jequitinhonha river alluvial plains occupy, and they can be considered as a finite natural resource. The stages of the manufacture process of the handcrafted pottery count on the participation of the men in the initial collection stages, `mud´ transport and paste formation while mostly women model the pieces to the final art. The pottery activity is carried out in all the months of the year, by men, women and children and they all sell their own production. In addition to retirement pensions and social programs such as the School Grant, the pottery activity is an important complement of the family income, and is even, in some cases, the only source of income in the Pasmado community.