Critérios mineralógicos, químicos e físicos para uso agronômico de pó de basalto hidrotermalizado no sul do Brasil

• Ano de defesa: 2018
• Autor(a) principal: Korchagin, Jackson
• Orientador(a): Bortoluzzi, Edson Campanhola
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade de Passo Fundo
• Programa de Pós-Graduação: Programa de Pós-Graduação em Agronomia
• Departamento: Faculdade de Agronomia e Medicina Veterinária – FAMV
• País: Brasil
• Palavras-chave em Português: Basalto; Minerais de argila; Mineralogia do solo; Solos - Produtividade
• Área do conhecimento CNPq: CIENCIAS AGRARIAS::AGRONOMIA
• Link de acesso: http://tede.upf.br:8080/jspui/handle/tede/1766

The exploitation of amethyst geodes in the region of Ametista do Sul, Rio Grande do Sul state, southern Brazil, generates a large amount of hydrothermal basalt tailings, which accumulate alongside the mines. This material contains clay minerals such as smectite and celadonite types which makes it promising as a remineralizer for agricultural soils. The following objectives were established to evaluate the potential use of this material in agriculture: i) assessment of the mineralogical and geochemical variability of hydrothermal basalt in the horizontal profile of the main geode exploration lava flow, in the region of Ametista do Sul; ii) determination of the solubility of chemical elements of agricultural interest from the hydrothermal basalt powder by using different extraction methods; and iii) assessment of the chemical and mineralogical characteristics of a Ultisol under native field after applying hydrothermalized basalt powder, as well as pasture production and nutrient export by plants. Hydrothermal basalt consists of plagioclases, clinopyroxenes, opaque minerals and apatite as accessory mineral, and is significantly altered for clay minerals in the matrix or filling vesicles. The mineral assemblage and the geochemical composition of the hydrothermalized basalt are similar along the horizontal profile. However, the basalt located near geodes is slightly more altered into clay minerals than the basalt composing the rest of the flow. The identified clay minerals are predominantly of the smectite and celadonite types. Among the methods tested to evaluate ion solubilization, those using ion exchange or solubilization in water extracted low percentages of calcium, magnesium, phosphorus, potassium and sodium from the hydrothermalized basalt powder. The method using acidic extractors increased the solubilization of calcium, magnesium and phosphorus, but potassium and sodium contents in solution did not exceed 3% of the total contents. Phosphorus was the most solubilized element, with release of up to 60% of the total contents, and 2% citric acid was the most efficient reagent for ion solubilization. Field tests showed changes in soil chemical and mineralogical characteristics, but at low magnitude. The application of increasing doses of basalt powder was responsible for increased available levels of phosphorus and copper in the soil, increased water pH but reduced potential acidity and potential cation exchange capacity of the soil. According to the mineralogical analyzes, increase in amounts of vermiculite in the soil clay fraction, that received hydrothermalized basalt powder application, was presumed. Dry mass production from the pasture had a linear and positive increase with the application of basalt powder but the increase in productivity was generally of low magnitude for the periods evaluated. Lastly, according to the amount of nutrients exported by the pasture during the research period, the concentration of the main nutrients contained in basalt powder is enough to supply partially or completely plant needs and exportation without depleting soil mineral reserves.