ABSTRACT: A set of attributes endows the soils with distinctive characteristics and astute understanding is required in order to formulate suitable strategies for soil management. The aim of this study was to physically, chemically and mineralogically characterize samples of the main soil classes in Minas Gerais, Brazil, determine the point of zero salt effect (PZSE) and the point of zero charge (PZC), and ascertain the correlation between these factors and soil attributes. The soils evaluated presented different textural classes ranging from loamy sand (Entisol) to very clayey (some Oxisols and Ultisols). The soils differed substantially in terms of fertility, presenting a range from dystrophic (low fertility, base saturation < 50 %) to eutrophic character (fertility, base saturation ≥ 50 %), even within the same soil class, such as the Oxisols, which suggests the concurrence of the parent material. Highly weathered soils are predominant in Minas Gerais and these soils are composed predominantly of kaolinite, gibbsite, goethite and hematite. Traces of hydroxy-Al interlayered vermiculite and illite were also found in the Oxisols, Ultisols and Inceptisols. A correlation between the PZSE and the PZC in the A horizon was observed. A high degree of correlation was observed between the PZC and the exchangeable aluminum and the ratio of iron obtained by ammonium oxalate and dithionite-citrate (Feo/Fed) in both the A and B horizons of soil classes. The results obtained reinforce the importance of knowledge of soil attributes to the adoption of practices such as the management of phosphate fertilization in clayey soils and liming in soils rich in aluminum.

ABSTRACT: Arsenic (As) is a naturally occurring chemical element considered toxic and carcinogenic by health and environmental protection agencies. Studies of As adsorption/desorption behavior in soils are important to predictions of As’ potential mobility in natural systems. The aim of this study was to assess the adsorption of As(V) in soils from Minas Gerais, Brazil, and determine its immobilization rate in order to identify soils with characteristics more favorable to its deployment as an As geochemical barrier. The adsorption experiment was performed using different As concentrations and the data pertaining to the maximum adsorption capacity of As(V) (MACAs) were determined by Langmuir and Freundlich isoterms. The Oxisols, due to their more oxidic mineralogy, especially more gibbsitic, and clayey texture, showed the highest MACAs, followed by Ultisols, Inceptisols, and Entisols. In terms of the desorption of As the Inceptisols were the soils that showed the most As desorption. Both As desorption and mobility was lower in the more oxidic and clayey soils. In all soils, the total amount of As was desorbed in due course, but the As release ratio tended to decrease with the passage of time. In general, soils with higher MACAs did not necessarily show less As desorption. For use as a geochemical barrier, as important as a high adsorption capacity of As by the soil is a low As desorption rate. The increase in As mobility may increase the risks of contaminating the supplies of water. To be a good As geochemical barrier the soil has to be a clayey Oxisol, with relatively high amounts of Fe and Al oxides, especially gibbsite.

ABSTRACT: Currently, the Brazilian savanna (Cerrado) represents the main agricultural area of the country, comprising a great variety of landscapes and soils, geological formations and vegetation patterns, as well as the major watershed. We studied the hydropedology and morphometry of a representative catchment (Frutal river), on a high tableland (Chapada) in the Triângulo Mineiro region, Brazil, describing the soil-water-landscape relationships to understand land use and water resources. To this end, we applied physical, chemical, micromorphological, and morphometric methods. When dry, compaction was observed in well-structured Ferralsols (Latossolos) with medium texture under intensive agriculture, reducing the water recharge capacity. The soil carbon stock was highest in hydromorphic savannas (veredas), reaching an organic matter content of 316.8 g kg-1 in the studied Umbric Gleysols, representing poorly drained lowlands. Physical and micromorphological properties were relevant parameters to understand the water recharge in soil; in agricultural fields, bulk density tended to increase and hydraulic conductivity to decrease, particularly under long-term sugarcane; morphometric parameters in the Frutal catchment indicated a low flooding risk and high flow capacity. This reinforces the need for soil conservation strategies to enhance water infiltration and groundwater recharge, with a view to maintain the water longer in the catchment. For surface water dynamics, slope morphology is an important property, affecting soil erosion, water retention and crop productivity.

Resumo A degradação do solo é um processo físico intensificado por fatores políticos e socioeconômicos, acentuado drasticamente pelo crescimento da população no século XX. O objetivo deste estudo foi avaliar os sedimentos do Ribeirão Frutal e Córrego Bebedouro, localizados no município de Frutal, Minas Gerais, Brasil, e sua relação com as principais atividades humanas que são responsáveis pelo processo avançado de erosão do solo e assoreamento. Foram coletadas amostras entre 2012 e 2013 para determinar a composição granulométrica, teor de matéria orgânica e sais minerais encontrados nos sedimentos. Para a medição do tamanho das partículas, foi utilizada a escala de Wentworth e, posteriormente, as classes de tamanho foram reagrupadas para a escala ABNT (NBR 6502/1995). De acordo com os resultados, a agricultura e a pecuária são as principais atividades que causam erosão acelerada e assoreamento em ambas as bacias hidrográficas. O Córrego Bebedouro é melhor preservado, uma vez que se encontra totalmente inserido na área rural, com mata ciliar melhor preservada do que o trecho médio do Ribeirão Frutal, localizado na área urbana. O quartzo é o mineral predominante nos sedimentos devido ao solos da região serem formados por arenitos, consequentemente, com poucos elementos nutricionais. A análise de componentes principais mostrou que parâmetros de qualidade da água estão correlacionados com a fração silte/argila e matéria orgânica na maioria das estações.

Abstract Soil degradation is a physical process intensified by political and socioeconomic factors, and by the population growth of the 20th century. In this study, we evaluated the sediments of the Frutal and Bebedouro Streams, located in Frutal municipality, Minas Gerais State, Brazil, and their relation to major human activities that are responsible soil erosion and silting. Samples were collected between 2012 and 2013 for the determination of granulometric composition, organic matter content, and minerals in sediments. The Wentworth scale was used for particle size measurement, and then the size classes regrouped to ABNT scale (NBR 6502/1995). The results found that agriculture and cattle ranching are the main activities that cause intense erosion and silting in both watersheds. Bebedouro Stream is better preserved, as it is completely located in rural area with larger riparian vegetation, unlike the mid-stretch of Frutal Stream, which is located in an urban area. Quartz is the predominant mineral in the sediments as the soils of the region are formed by sandstones; consequently, few nutritional elements were found in the studied samples. Principal component analysis showed that water quality parameters are correlated to silt/clays and organic matter content in most of the collected stations.

ABSTRACT Quilombolas are Afro-brazilian rural peasants who descended from escaped slaves who tried to carve out territories of autonomy (called Quilombos) by collective organization and resistance. Despite many anthropological and ethnopedological studies, little research has been carried out to identify the agricultural practices and the knowledge of people who live in the Quilombos (Quilombolas). Peasant communities who live from land resources have wide empirical knowledge related to local soils and landscapes. In this respect, ethnopedology focuses on their relationship with local practices, needs, and values. We carried out an ethnopedological evaluation of the soils, landscape and land suitability of the Malhada Grande Quilombola Territory, aiming to examine the local criteria involved in land-use decision making, and evaluate the legitimacy of local knowledge. For this purpose, participatory workshops allowed environmental stratification of the Quilombolas into landscape units, recognition of soil types, and evaluation of land-use criteria. This approach was combined with conventional soil sampling, description, and analysis. The Brazilian System of Soil Classification and its approximations to the WRB/FAO system and the SAAT land evaluation system were compared with the local classificatory systems, showing several convergences. The Quilombolas stratified the local environment into eight landscape units (based on soil, topography, and vegetation) and identified eight soil types with distinct morphological, chemical, and physical attributes. The conventional soil survey identified thirteen soil classes, in the same eight landscape units, organized as soil associations. The apparent contradictions between local knowledge and Pedology were relative since the classification systems were established based on different criteria, goals, and sampling references. Most soils are only suitable for pasture, with restricted agricultural use, due to water or oxygen deficiencies. The current land use was only inconsistent with the technical recommendations when socioecological constraints such as the semiarid climate, land availability, and economic conditions for land management led to overuse of the land. Local knowledge demonstrated its legitimacy and allowed a useful and fruitful exchange of information with the academic view of soil-landscape interplays. Although mostly unknown by the scientific community, local knowledge proved capable of achieving social welfare and food security. In addition, a participatory survey proved to be a core factor for more grounded and detailed data collection on how Quilombolas decide land use on a local scale.

Considerando a expressividade de Cambissolos (rasos, adensados e siltosos) e Latossolos argilosos e muito argilosos desenvolvidos de rochas pelíticas do Grupo Bambuí, bem como os poucos estudos relacionados à gênese e potencialidade agrícola desses solos, selecionaram-se duas áreas no município de Curvelo-MG, cujo objetivo foi estudar suas características físicas, químicas e mineralógicas. Para isso, foram descritos e coletados perfis de Cambissolos Háplicos (CX), Latossolos Vermelho-Amarelos (LVA) e Latossolos Vermelhos (LV), sendo a TFSA submetida às análises físicas e químicas de rotina, digestão total e sulfúrica, além das análises mineralógicas. Os difratogramas de raios X (DRX) e o índice de intemperismo (Ki) dos CX indicaram menor grau de pedogênese e maior proporção de caulinita e ilita na fração argila (comparativamente aos Latossolos), que coexistem com gibbsita (Gb) e vermiculita com Al-hidroxi entrecamadas (VHE). Nesse caso, a ocorrência de gibbsita não é um bom indicativo de intemperização acentuada. Nos CX, os elevados teores de silte associados à possibilidade de forte ajuste face a face de caulinita/ilita podem ser os principais fatores que interferem na quase ausência de organização estrutural, no adensamento, na pouca percolação de água e na formação de selamento superficial. Na fração argila dos Latossolos foi constatada coexistência de argilominerais e óxidos de Fe e Al muito semelhante à encontrada para os CX, porém com menores proporções de ilita e maiores de gibbsita, inferidos pelos resultados do Ki em torno de 1,4. Ainda que não haja diferenciações químicas e físicas marcantes entre os Latossolos, constatou-se em LV magnetização considerável na fração areia, cujo DRX confirmou a presença de magnetita, fato pouco comum em Latossolos desenvolvidos de rochas pelíticas do Grupo Bambuí, mas constatado em estudos anteriores.

The widespread occurrence of Cambisols (shallow, dense and silty) and of clayey and very clayey Latosols is typical of pelitic rocks of the pre-Cambrian Bambui Group landscape, but few studies are focused on the genesis and agricultural potential of these soils. Two areas were selected in Curvelo, state of Minas Gerais, for a detailed study of physical, chemical and mineralogical properties of these soils, to deepen the understanding of the pedogenesis of this area. Soils classified as Haplic Cambisols (Inceptisols), Red-Yellow latosol (Xanthic Haplustox) and Red latosol (Rhodic Haplustox) were selected and sampled, and analyzed for the chemical, mineralogical and physical properties. The XRD data coupled with the calculated weathering index indicated a lower degree of weathering in the shallow Cambisols, with higher proportion of illite and kaolinite in the clay fraction, in comparison to the Latosols, where kaolinite, gibbsite and hydroxy-interlayered vermiculite (HIV) coexist. In this case, the occurrence of gibbsite is not a good indicator of severe weathering. In the shallow Cambisols, higher silt content combined with a face-to-face arrangement of clay particles (kaolinite/illite) may have resulted in poor structural organization, denseness, low water infiltration and soil sealing. In the clay fraction of Latosols, we observed the coexistence of kaolinite/illite and Fe/Al oxides, similarly to the Cambisols, but with much less illite and higher gibbsite contents, as inferred from the results of Ki of around 1.4. Although there are no remarkable physical and chemical differences among Latosols, the Rhodic Latosols displayed considerable magnetization in the sand fraction, where XRD confirmed the presence of magnetite, an uncommon fact in the supposedly magnetite-free pelitic lithologies of the Bambuí Group, but reported in previous studies as well.