Minerais ferruginosos e fertilidade natural de solos magnéticos do Vale do Jequitinhonha, Minas Gerais, Brasil

Abstract

RESUMO:Este estudo teve como objetivo caracterizar as naturezas química e mineralógica de solos derivados de materiais de origem básicos e ácidos do Vale do Jequitinhonha, Minas Gerais, Brasil, com foco na ocorrência de minerais magnéticos e suas relações com a fertilidade natural. ABSTRACT: This study aimed at characterizing the chemical and mineralogical nature of soils derived from basic and acidic bedrocks from the Jequitinhonha Valley, Minas Gerais State, Brazil, focusing on the occurrence of magnetic minerals and its relationship with the natural fertility. The following soils were described, classified and sampled, according to the USDA Soil Taxonomy nomenclature: Typic Haplustox, Rhodic Kandiustox, Rhodic Haplustox and Typic Argiustoll. Granulometric analyzes and contents of macro and micronutrients were determined. In order to get more insights about each diagnostic soil horizon, the contents of the main metal cation oxides, specifically, iron, aluminum and manganese, were obtained by sulfuric acid digestion, and through their residual extractions with mixtures dithionite -citrate -bicarbonate and oxalate -oxalic acid. The samples were also analyzed by Mössbauer spectroscopy in an attempt to identify the main magnetic iron oxides. Maghemite (γFe 2 O 3 ) was found in all samples and magnetite (Fe 3 O 4 ) was identified only for the sample Typic Argiustoll. Soils with higher magnetizations were found to have higher natural fertility.

Mineralogical Evolution of Magnetic Rhodic Oxisols under Different Lithological Influences in Brazil

“…Rhodic Oxisols exhibit strong magnetic attraction due to high contents of ferrimagnetic Fe oxides (maghemite and magnetite) (Costa et al, 1999(Costa et al, , 2014Camêlo et al, 2018;Poggere et al, 2018). These minerals have often been used in studies on pedogenesis (Silva et al, 2017;Camêlo et al, 2018) for stratification of environments (Ramos et al, 2017) and soil fertility (Costa et al, 2018) in Brazil and elsewhere in the world.…”

“…Therefore, several authors have reported on magnetite predominance in the coarse fractions (sand and silt) and maghemite in the clay fraction (Costa et al, 1999;Carvalho Filho et al, 2015;Camêlo et al, 2018;Poggere et al, 2018) of Fe-rich Rhodic Oxisols in Brazil. However, it is known that both minerals can display distinct soil size fractions or occur in all of them (Causevic et al, 2004;Maxbauer et al, 2016;Silva et al, 2017;Costa et al, 2018).…”