ABSTRACT The application of rock dust (RD) in agricultural soils has shown the capacity to improve soil conditions for plant growth. However, the successful use of RD requires understanding its effects on weathering in soil surfaces and its possible products. In this study, we present the results of an exploratory test in which a RD had its weathering intensified in a soil column by temperature (45 °C) and intense leaching (1,339.2 mm in 24 weeks), in the absence of plants. There was a significant increase in amorphous phases of iron (Fe) and particularly of aluminum (Al) to the amount of 0.13 g kg –1 for Fe and 0.16 g kg –1 for Al in the 0-0.05 m layer of the column and 0.22 g kg –1 for Al in the 0.05-0.10 m layer. These values account for 6 % of the total Fe, and 27 % of the total Al added as RD in the column. Spectral features in the visible-near infrared-short wave infrared (VIS-NIR-SWIR) and mid-infrared (MIR) range, as well as X-ray diffraction (XRD) scans, were inconclusive because of the small signal-noise ratio of the newly precipitated phases. Selective chemical methods targeted to specific soil pools (precipitated, adsorbed, and leached) were more sensitive to capture the new amorphous phases resulting from the RD dissolution. This study contributes to understanding the effects of RD on the availability of ions and the possibility of amorphous oxides precipitating in the soil. In addition, it helps identify other effects associated with using RD, such as changes in the pH, cation exchange capacity (CEC), and nutrient availability. (RD growth However products 45 (4 °C C 1,339.2 13392 1 339 2 (1,339. weeks, weeks , weeks) plants (Fe (Al 013 0 13 0.1 – 016 16 00.05 0005 0.05 05 0-0.0 022 22 0.2 0.050.10 005010 0.10 10 0.05-0.1 visiblenear visible near infraredshort short VISNIRSWIR VIS NIR SWIR (VIS-NIR-SWIR midinfrared mid MIR (MIR range Xray X ray XRD (XRD scans signalnoise signal noise precipitated, (precipitated adsorbed leached dissolution addition pH CEC, CEC (CEC) 4 ( 1,339. 1339 33 (1,339 01 0. 00 00.0 000 005 0.0 0-0. 02 050 0.050.1 00501 010 0.05-0. (CEC 1,339 133 3 (1,33 00. 0-0 0.050. 0050 0.05-0 1,33 (1,3 0- 0.050 0.05- 1,3 (1, 1, (1

ABSTRACT The term Sum of Bases has different meanings in Soil Science and the Remineralizer Regulations. This issue may cause misunderstandings in communication, particularly between the agricultural community and the mining community, becoming an obstacle to the advancement of the use of this soil amendment. In this scientific note we propose the use of subscript “R” (SBR), standing for Rock, in English, and Rocha, in Brazilian Portuguese, and “S” (SBS) standing for Soil in English and Solo in Brazilian Portuguese. In this way SBR will refer to the Sum of Bases as defined in the Remineralizer Regulation (), and SBS to the Sum of Bases as defined in Soil Science (SBS = Ca (mmolc dm-3) + Mg (mmolc dm-3) + K (mmolc dm-3) + Na (mmolc dm-3)). This approach avoids confusion and facilitates the correct use of laboratory data. We provide a working example, a conversion table and a formula to estimate the potential increase in SBS caused by SBR. Regulations communication amendment R “R SBR, , (SBR) Rock Rocha Portuguese S “S () mmolc dm3 dm 3 dm-3 dm3. . dm-3)) data example (SBR ( dm-

RESUMO Na região da Serra da Mantiqueira os estudos pedogenéticos podem contribuir tanto para o entendimento de eventos pretéritos como para auxiliar na conservação dos recursos naturais. Este estudo objetivou caracterizar solos de região altomontana de Minas Gerais para avaliar a influência das condições paleoambientais na pedogênese. Cinco perfis foram selecionados e caracterizados quanto aos atributos morfológicos, físicos e químicos. Análises isotópicas de 13C foram realizadas em amostras de solo coletadas nas profundidades de 10, 20, 30, 40, 50, 60, 80 e 100 cm; exceto em P2, que foi coletado até 60 cm de profundidade. A distribuição errática das frações granulométricas e de C evidenciam a natureza sedimentar dos solos, resultado da ação erosiva condicionada pelo relevo. Nos perfis P2, P4 e P5 (Cambissolos/Cambisols) a coloração brunada indica o processo de xantização, enquanto no perfil P1 (Argissolo/Lixisol) é evidenciado o processo de eluviação e iluviação, resultando no incremento de argila em profundidade e pela presença de cerosidade. Em P3 (Latossolo/Ferralsol) os pequenos valores de soma de bases, remoção de sílica e valores da razão SiO2/Al2O3 (índice ki) inferiores a 1,0 evidenciam o intemperismo avançado e o processo de alitização. Nos perfis verifica-se elevados teores de C orgânico em profundidade e acúmulo superficial, o que sugere a ocorrência do processo de melanização. A variação na assinatura isotópica do δ 13C indica uma condição pretérita mais seca, com vegetação mista, com mudança gradual de vegetação com via fotossintética predominante C3. Em P1 e P4, a diminuição dos teores de δ 13C em superfície é resultado da ação antrópica.

ABSTRACT In the Serra da Mantiqueira region the pedogenetic studies contribute to both the understanding of past events and supporting the conservation of natural resources. This study aimed to characterize the soils from the Minas Gerais high-mountains region to evaluate the influence of paleoenvironmental conditions on pedogenesis. Five profiles were selected and characterized for morphological, physical and chemical properties. Isotopic analyses of 13C were performed in soil samples collected at depths of 10, 20, 30, 40, 50, 60, 80 and 100 cm; except in P2, which was collected up to 60 cm deep. Erratic distribution of the particle-size fractions and C contents highlight the sedimentary nature of the profiles, resulting from the erosive action favored by the relief. High organic C content in subsurface and its accumulation in the surface were observed in the profiles, which suggests the occurrence of the melanization process. In the profiles P2, P4 and P5 (Cambissolos/ Cambisols) the brownish color indicates the xanthization process, while in P1 (Argissolo/ Lixisol), is highlighted the process of eluviation and illuviation resulting in the increase of clay in subsurface and presence of clay films. In P3 (Latossolo/ Ferralsol), the low values of sum of bases, silica removal and SiO2/Al2O3 ratio (ki index) values below 1.0 point to the advanced weathering and the allitization process. The variation in the isotopic signature of δ13C indicates a drier past condition, with mixed vegetation, with gradual change of vegetation with predominant C3 photosynthetic pathway. In P1 and P4, the decrease in the contents of δ13C in surface results from anthropic action.

ABSTRACT The combination of pillarization and charge neutralization with Li+ can make montmorillonite an important support material for industry and decontamination of pollutants in soil and water. Montmorillonite characterization techniques were described in detail, and pillarization procedures were used, after Li+ saturation, to modify and manipulate the chemical and mineralogical surface properties of this montmorillonite. Eight samples were produced: 1) natural montmorillonite (Chisholm Mine - MMT); 2) Li+ saturated montmorillonite (MMTLi); 3) polyethylene glycol (PEG) Al-pillared montmorillonite (AlPEG); 4) PEG Al-pillared montmorillonite saturated with Li (AlPEGLi); 5) Al-pillared montmorillonite with 14 h contact time (Al14h); 6) Al-pillared montmorillonite Al14h saturated with Li (Al14hLi); 7) Al-pillared montmorillonite with 0 h contact time (Al0h); and 8) Al-pillared montmorillonite Al0h saturated with Li (Al0hLi). The natural sample was identified as interlayered montmorillonite composed of chlorite layers or with a high degree of Al-hydroxy filling. Concerning the total permanent charges, 70 % occurred by isomorphic substitution of Al3+ by Mg2+ in octahedral layer and 30 % of Si4+ by Al3+ in tetrahedral layer. The pillarization method using the PEG produced a small number of stable pillars. The new milder pillarization method (Al0h) did not cause damage in the formation of Al-hydroxy. In this method, the resulting pillars were more homogeneous in size. Thereby, the Al0h Li method has been shown to produce a supporting material with a constant interlayer spacing, increased of the specific surface area (SSA), and drastic reduction of the cation exchange capacity (CEC) as compared to MMT. This modified mineral can be used in, for example, decontamination of polluted water with nonionic organic pollutants.

ABSTRACT: Regolith characterization in its entirety is particularly difficult in gneissic regoliths due to the heterogeneity of their rock structure. Rare earth elements (REE) are a useful tool in helping understand the evolution of regoliths. This study relates the mineralogy and weathering indexes of three gneisses regoliths (P1-leucocratic, P2-mesocratic and P3-melanocratic gneisses) to the distribution of REE at depth. In soil, clay activity, iron and manganese oxides, CaO, SiO2, P2O5, TiO2, Fe2O3, and MgO showed high positive correlation with REE. The absolute content of REE was enriched in mafic minerals. At the interface between the soil and saprolite, the sum of absolute REE content was greater in soil than in saprolite in P1, while the opposite pattern was found in P2 and P3. The sums of absolute REE in the whole profiles did not overlap between P1, P2 and P3, and the absolute concentration of Gadolinium (Gd) differentiated the three gneisses in all and every horizon/layer of their regoliths without overlapping values. Normalized REE content was greater in the subsurface of P1 due to Eu content in plagioclase, and fractionation had less variation when estimated by Light REE / Heavy REE (LREE/HREE) than by La/Yb, since the variation in REE is great in gneisses (due to the segregation of minerals into bands), and had low levels of association with the Chemical Index of Alteration (CIA) and the Weathering Index of Parker (WIP).

Resumo O objetivo deste trabalho foi analisar as modificações mineralógicas, morfológicas e composicionais resultantes do intemperismo de grãos de diabásio enterrados em solo sob diferentes usos da terra por até 378 dias. Amostras de diabásio cominuído foram colocadas em sacos de poliéster e enterradas em solo sob cultivo de milho, capim-elefante e floresta, tendo sido desenterradas e avaliadas após quatro períodos. As amostras do remineralizador (RM) foram analisadas por difratometria de raios X, análise química total, microscopia eletrônica de varredura, e teores de Al (Ald e Alo) e Fe (Fed e Feo) extraídos com soluções de ditionito-citrato-bicarbonato (DCB) e amônio oxalato (AAO). Os plagioclásios e os piroxênios intemperizaram mais rápido nos três tipos de uso da terra, e mostraram o mesmo padrão de ganhos e perdas no balanço de massa de elementos. A caracterização das formas de Fe e Al em DCB e AAO mostrou que a maior mudança destes elementos foi da fase litogênica e cristalina para a secundária e amorfa, em comparação aos seus teores totais. Os plagioclásios e os piroxênios foram os minerais mais alterados, e Fe e Al apresentam grande transferência entre a fase cristalina e amorfa, com valores de até 26 e 175, respectivamente, para as razões entre sacos com RM/Feo e RM-controle e sacos com RM/Alo e RM-controle.

Abstract The objective of this work was to analyze the mineralogical, morphological, and compositional modifications resulting from the weathering of diabase grains buried into soil under different land uses for up to 378 days. Samples of comminuted diabase were put into polyester bags and buried into soil under corn crop, elephant grass, and woods, being unburied and evaluated after four time periods. The samples of the remineralizer (RM) were analyzed by X-ray diffractometry, total chemical analysis, scanning electron microscopy, and Al (Ald and Alo) and Fe (Fed and Feo) contents extracted by sodium dithionite-citrate-bicarbonate (DCB) and ammonium oxalate (AAO) solutions. Plagioclases and pyroxenes were the most weathered minerals in all three land uses and showed the same pattern of elemental gains and losses. The characterization of Fe and Al solubility in DCB and AAO showed that the greatest change in these elements was from the lithogenic and crystalline to the pedogenic and amorphous phase, when compared with their total content. Plagioclases and pyroxenes were the most weathered minerals, and Fe and Al show a great transfer from the crystalline to the amorphous phase, with values up to 26 and 175, respectively, for the ratios between bags with RM/Feo and RM-control and bags with RM/Alo and RM-control.

ABSTRACT Saprolite plays a central role into hydrologic and nutrient cycles. Despite that, saprolite research is scattered and uses heterogeneous, sometimes conflicting, methods and concepts. During field work, it is difficult to assign the boundary between soil and saprolite. This paper aimed to identify the subjacent logic that pedologists use to assign to a regolith volume its soil or saprolite nature. To achieve this goal, a tree algorithm was used to build a hierarchy of physical and chemical properties of a set of regolith profiles. Such hierarchization expose the inner, subjective criteria used by researchers during the assignment of a certain profile zone as saprolite or soil. The following variables were measured: total porosity (TP); bulk density (Bd); particle density (Pd); total Fe2O3, Al2O3, CaO, MgO, K2O, Na2O, P2O5, and TiO2; selective extraction of iron by ditionite-citrate-bicarbonate (FeDCB) and ammonium oxalate (FeOA); and the FeDCB/FeOA ratio. These measurements were done in a set of 25 regolith profiles (137 horizons and layers), located in the Southeast region and Northeast region of Brazil. The decision tree algorithm was applied using the recursive partition method to identify which of the measured property was most strongly associated with the field assignment of the pedologists to a certain profile zone as saprolite or soil. The Bd, FeDCB/FeOA, MgO, CaO, TP, and P2O5 explained 93 % of the pedologists choice, being Bd responsible for 81 %.

ABSTRACT Lithological and geomorphological variations determine formation of soils with different mineralogical constitutions and can influence the distribution of potentially toxic elements (PTE). The aim of this study was to determine the contents of PTE and mineralogical assemblages along soil profiles of different classes and parent materials and to investigate the association among these factors in the São Francisco sedimentary basin in the northern part of the state of Minas Gerais (Brazil). Eight soil pedons of different classes that developed from different parent materials (limestone, siltstone, phyllite, alluvial-colluvial sediments, detrital cover, and rhythmite) were studied in two lithotoposequences. Soil morphological, particle-size, and chemical analyses were carried out for soil characterization and classification. A mineralogical investigation was carried out by X-ray diffraction on soil sand, silt, and clay fractions. Potentially toxic elements were extracted by microwave-assisted acid digestion (EPA 3015A method) and determined in an ICP-OES. Soil mineralogy showed relevant interactions between pedogenesis and morphogenesis. Quartz is the main mineral in the sand and silt fractions, with varying amounts of weatherable primary minerals, whereas kaolinite is the main mineral in the clay fraction, followed by 2:1 clay minerals and oxides. The main soil properties associated with PTE variability were pH, redox environment, mineral and organic reactive surfaces, and clay content. The unique patterns of PTE distribution per pedon and differences in PTE contents in soils from the same parent material, but with different pedogenic evolution, showed that pedogenic processes influence PTE distribution. Mainly Mn, Ni, Pb, and Ba were influenced by parent material, especially limestone, siltstone, and detrital cover, but Cd, As, and Cu were also influenced. To a lesser extent, Mo was influenced by phyllite and Cr by detrital cover and phyllite. Rhodic Ferralsol (Latossolo Vermelho Distrófico típico) was the only taxonomic class to show class association with PTE. The association of Ferralsols (Latossolos) with Cd, Mn, Ni, Pb, Ba, As, and Cu and the low contents of these elements in soils of this class suggest that pedogenic processes common to Ferralsol (Latossolo) evolution are responsible for decreasing levels of these PTE.

RESUMO: O uso de remineralizadores como insumo agrícola foi regularizado em 2013, mas seus mecanismos de ação precisam ser melhor conhecidos para viabilizar o manejo nos campos agrícolas. Atributos químicos de um Latossolo foram monitorados após remineralização com diabásio. O aumento de Na trocável foi atribuído à dissolução das bordas dos plagioclásios (albita) onde a concentração deste elemento é maior. Infelizmente, não é possível especular se o tempo decorrido desde a aplicação (um a dois anos, dependendo do tratamento) foi suficiente para solubilizar o núcleo cálcico (anortita) destes cristais, já que o remineralizador possui outros minerais fonte de Ca. Houve aumento da capacidade de troca catiônica efetiva sem aumento do pH. As hipóteses propostas para explicar este fenômeno são a precipitação de fases oxídicas amorfas e o aparecimento de cargas elétricas na superfície dos grãos do remineralizador durante sua dissolução. Apesar da concentração de Al2O3 do remineralizador (11,90%) e Fe2O3 (14,45%), não houve aumento destes elementos no complexo de troca, possivelmente por sua rápida precipitação em formas amorfas (Alo e Feo no solo).

ABSTRACT: Remineralizers are comminuted rocks that are applied to soil, and their use as an agricultural amendment was regulated in Brazil in 2013. However, mechanisms of action of these materials must be better known to enable them to be best used in agricultural fields. Soil chemical attributes of an Oxisol were monitored after the application of a diabase remineralizer. The increase in exchangeable Na observed was associated with the dissolution of the border of the plagioclase crystals where this element is highly concentrated (albite). Therefore, it was inferred that the time since the application of the remineralizer (1 to 2 years depending on the treatment) was not sufficient to exhaust this crystal volume. Unfortunately, the presence of several sources of Ca-containing minerals in the remineralizer did not allow to infer if the calcic nuclei was dissolving. An increase in effective cation exchange capacity was observed without the concurrent increase in the pH of the soil. The two non-exclusive hypotheses proposed to explain this result were that an extra surface charge has originated on the surface of the newly precipitated oxidic phases and/or from the dissolution of the remineralizer grains. Rapid precipitation of amorphous solids (as measured by the increase in Alo and Feo) would also explain the lack of increase in exchangeable Fe and Al despite the large amount of Al2O3 (11.90%) and Fe2O3 (14.45%) in the remineralizer.

ABSTRACT The Bambuí Group, formed from siliciclastic sediments deposited on an extensive epicontinental platform at the end of the Neoproterozoic era, is characterized by limestones with fine to very fine texture. Limestone-derived soils in the southeast of Tocantins state, Brazil, are less notorious than similar soils in other regions of Brazil and their characterization could contribute to the Brazilian System for Soil Classification (SiBCS). Given that little is known of these soils, despitetheir agricultural potential, the objective of this study was to characterize their properties and the processes leading to soil of genesis, and also contribute to developing the Brazilian System of Soil Classification (SiBCS). Soils profiles were located on the summit (P1), shoulder (P2), backslope (P3), and footslope (P4) of a toposequence in the municipality of Lavandeira, Tocantins. Morphological, physical, chemical, and mineralogical properties of the profiles were determined. The soils were classified as: P1 - Chernossolo Rêndzico Lítico típico (Lithic Haplustolls); P2 - Cambissolo Háplico Ta Eutrófico léptico hipocarbonático (Lithic Haplustolls); P3 - Cambissolo Háplico Carbonático léptico (Lithic Haplustepts); and P4 - Luvissolo Háplico Órtico típico (Typic Rhodustalfs). All the profiles showed high contents of silt, calcium, and magnesium, which resulted in high pH and low exchangeable aluminum content. Base saturation and calcium carbonate equivalent contents were also high, and the horizons showed dark colors due to high organic matter content, which contained humin as the dominant fraction. Mineralogical analysis of the clay fraction indicated predominance of hydroxy-interlayered vermiculite, followed by illite, kaolinite, and quartz, whereas the sand fraction exhibited reflections characteristic of the quartz mineral. Given P4 contents of calcium carbonate equivalent above 50 g kg-1 and the relevance of this feature for agriculture, we propose the inclusion of hypocarbonate as a criterion for classification of Luvissolos Háplicos Órticos at the subgroup level.

RESUMO Os impactos das práticas de manejo intensivo sobre a sustentabilidade da produção florestal dependem da manutenção da fertilidade do solo. A contribuição dos resíduos florestais e da ciclagem de nutrientes nesse processo é crucial. Avaliou-se uma plantação de 16 anos de idade de Pinus taeda em um Cambissolo Húmico Alumínico léptico de textura argilosa, relevo ondulado, no meio-sul catarinense. Dez árvores foram amostradas em cinco classes de diâmetro, de acordo com a distribuição de diâmetro à altura do peito. A biomassa de acículas, galhos, casca, madeira e raízes foi medida para cada árvore. Além da biomassa vegetal, amostraram-se serapilheira acumulada e solo nas camadas de 0,00-0,20; 0,20-0,40; 0,40-0,60; 0,60-1,00; 1,00-1,40; 1,40-1,80, e 1,80-1,90 m. A concentração de nutrientes, o balanço de nutrientes e a caracterização mineralógica foram determinados a partir das amostras de solo coletadas. Três cenários de intensidade de colheita foram simulados, considerando a remoção de madeira (A), madeira e casca (B) e madeira, casca e copa (C). A soma de todos os componentes da biomassa foi de 313 Mg ha-1. O estoque de nutrientes na árvore foi N>Ca>K>S>Mg>P. A mineralogia do Cambissolo Húmico Alumínico léptico evidenciou a predominância de areia de quartzo e pequenos traços de vermiculita na fração silte. A argila é a principal fração que contribui para o intemperismo do solo em razão da transformação de ilita-vermiculita liberando K. O esgotamento dos nutrientes do solo a partir da biomassa foi: P>S>N>K>Mg>Ca. Fósforo e S permaneceram como os nutrientes mais limitantes no cenário A, por causa dos seus baixos estoques disponíveis no solo. No cenário B, o número de rotações florestais foi limitado para N, K e S. O cenário C resultou na maior diminuição de produtividade, e limitado pelo P, apresentando apenas duas potenciais rotações de cultivo para esse nutriente. Dessa forma, evidenciou-se, pelo número potencial de rotações de cultivo, que entre o cenário A, menos exaustivo, e cenário C, mais exaustivo, uma diferença de até 30 anos na capacidade de suporte do solo. Assim, o efeito de diferentes intensidades de colheita sobre a disponibilidade de nutrientes pode comprometer a sustentabilidade do P. taeda em longo prazo.

ABSTRACT The impact of intensive management practices on the sustainability of forest production depends on maintenance of soil fertility. The contribution of forest residues and nutrient cycling in this process is critical. A 16-year-old stand of Pinus taeda in a Cambissolo Húmico Alumínico léptico (Humic Endo-lithic Dystrudept) in the south of Brazil was studied. A total of 10 trees were sampled distributed in five diameter classes according to diameter at breast height. The biomass of the needles, twigs, bark, wood, and roots was measured for each tree. In addition to plant biomass, accumulated plant litter was sampled, and soil samples were taken at three increments based on sampling depth: 0.00-0.20, 0.20-0.40, 0.40-0.60, 0.60-1.00, 1.00-1.40, 1.40-1.80, and 1.80-1.90 m. The quantity and concentration of nutrients, as well as mineralogical characteristics, were determined for each soil sample. Three scenarios of harvesting intensities were simulated: wood removal (A), wood and bark removal (B), and wood + bark + canopy removal (C). The sum of all biomass components was 313 Mg ha-1.The stocks of nutrients in the trees decreased in the order N>Ca>K>S>Mg>P. The mineralogy of the Cambissolo Húmico Alumínico léptico showed the predominance of quartz sand and small traces of vermiculite in the silt fraction. Clay is the main fraction that contributes to soil weathering, due to the transformation of illite-vermiculite, releasing K. The depletion of nutrients from the soil biomass was in the order: P>S>N>K>Mg>Ca. Phosphorus and S were the most limiting in scenario A due to their low stock in the soil. In scenario B, the number of forest rotations was limited by N, K, and S. Scenario C showed the greatest reduction in productivity, allowing only two rotations before P limitation. It is therefore apparent that there may be a difference of up to 30 years in the capacity of the soil to support a scenario such as A, with a low nutrient removal, compared to scenario C, with a high nutrient removal. Hence, the effect of different harvesting intensities on nutrient availability may jeopardize the sustainability of P. taeda in the short-term.

Apesar de vários estudos abordando o limite inferior do solo e o seu contato com a camada saprolítica, ainda existem demandas referentes à padronização da identificação e anotação dessas variáveis no campo. Em solos rasos, a anotação correta desses limites ou contatos é essencial para determinar o seu comportamento e potencial de uso. Os objetivos deste estudo foram identificar e definir o contato e, ou, zona de transição entre solo e saprolito em perfis de Argissolos derivados de arenito fino e siltito argiloso em ambiente subtropical no sul do Brasil e, subsequentemente, validar as observações de campo pelas análises multivariadas de dados obtidos no laboratório. Nos seis perfis avaliados, a sequência de horizontes encontrada foi A, Bt, C e Cr, onde C foi considerado parte do solo, em razão da sua estrutura pedogênica; e Cr, saprolito, por causa da estrutura de rocha. Os atributos morfológicos que foram determinados no campo e se evidenciaram diferentes entre os horizontes B e C e a camada Cr foram: cor, estrutura, textura e fragmentos de saprolito. De acordo com o teste de médias, os atributos que suportam a inclusão do horizonte C como parte do solo foram: areia, argila, argila dispersa em água, relação silte/argila, macroporosidade, porosidade total, resistência a penetração, capacidade de troca de cátions, ferro extraído com DCB, Al, H+Al e atividade da argila. Os atributos que suportam o horizonte C como uma zona de transição foram: silte, Ca, C orgânico total e Fe extraído com oxalato de amônio. A análise discriminante indicou diferenças entre os três horizontes avaliados (B, C e Cr).

Despite numerous studies conducted on the lower limit of soil and its contact with saprolite layers, a great deal of work is left to standardize identification and annotation of these variables in the field. In shallow soils, the appropriately noting these limits or contacts is essential for determining their behavior and potential use. The aims of this study were to identify and define the field contact and/or transition zone between soil and saprolite in profiles of an Alisol derived from fine sandstone and siltstone/claystone in subtropical southern Brazil and to subsequently validate the field observations through a multivariate analysis of laboratory analytical data. In the six Alisol profiles evaluated, the sequence of horizons found was A, Bt, C, and Cr, where C was considered part of the soil due to its pedogenetic structure, and Cr was considered saprolite due to its rock structure. The morphological properties that were determined in the field and that were different between the B and C horizons and the Cr layer were color, structure, texture, and fragments of saprolite. According to the test of means, the properties that support the inclusion of the C horizon as part of the soil are sand, clay, water-dispersible clay, silt/clay ratio, macroporosity, total porosity, resistance to penetration, cation exchange capacity, Fe extracted by DCB, Al, H+Al, and cation exchange capacity of clay. The properties that support the C horizon as a transition zone are silt, Ca, total organic C, and Fe extracted by ammonium oxalate. Discriminant analysis indicated differences among the three horizons evaluated.

A exploração das propriedades químicas e estruturais de argilas expansivas, por meio da intercalação de polímeros inorgânicos no espaço interlamelar, permite o desenvolvimento de materiais reativos e com elevado potencial de aplicação tecnológica, agronômica e ambiental. Esta técnica, conhecida como pilarização, já é bastante difundida na área das ciências química e dos materiais, havendo esforços crescentes nos últimos anos para aplicação desses materiais com fins ambientais. Contudo, apenas uma fração do conhecimento acumulado é atualmente utilizada diretamente por cientistas do solo, abrindo oportunidades para novas pesquisas por meio do intercambio de conhecimento entre as diferentes áreas de pesquisa, como físico-química e microbiologia. Portanto, esta revisão apresenta e discute o que são a pilarização e as argilas pilarizadas, métodos de síntese e algumas aplicações nas ciências do solo e ambiental, buscando encorajar mais grupos brasileiros de pesquisa a explorá-las.

The use of chemical and structural properties of swelling clays intercalated with inorganic polymers allows the development of materials with high reactivity and potential for technological and environmental applications. This technique is known as pillaring and has been studied widely in the field of chemical and material science, but the use of pillared clays for environmental application has increased only in the last few years. Nevertheless, only a fraction of this knowledge is applied by soil scientists being, therefore, an opportunity to develop new studies including a wide range of disciplines, such as physico-chemistry and microbiology. Therefore, this review presents and discusses what are pillaring and pillared clays, methods of synthesis and some applications in soil and environmental science, aiming to encourage more research groups in Brazil to explore it.

No Estado do Rio Grande do Sul (RS), os Neossolos Litólicos e Neossolos Regolíticos são solos que têm sofrido forte pressão de uso, demandando maior conhecimento sobre sua gênese e mineralogia. O objetivo deste trabalho foi determinar o grau de intemperismo de Neossolos Litólicos e Neossolos Regolíticos, avaliando-se a alteração dos minerais em perfis dispostos em uma climo-litossequência no Planalto do RS, através de técnicas de dissolução química e difração de raios X. Foram identificados dois grupos de solos com graus de alteração distintos. O primeiro é constituído pelos perfis da porção Oeste da climo-litossequência (P1, P2 e P3) e encontra-se no estádio entre a bissialitização e a monossialitização, com predomínio de esmectita com hidroxi-Al entrecamadas (EHE), caulinita e hematita na fração argila. O segundo é representado pelos perfis da porção Leste (P4 e P5), encontrando-se no estádio entre a monossialitização e a ferralitização, com predomínio de caulinita e goethita e presença de gibbsita e EHE na fração argila. Os resultados sugerem maior influência do clima na alteração dos perfis. Os índices ki e kr não foram eficientes em representar a condição de alteração secundária dos perfis de Neossolos.

In the Rio Grande do Sul state (RS) Neossolos Litólicos (Leptosols) and Neossolos Regolíticos (Regosols) are soils that have been suffering strong use pressure, demanding better knowledge on their genesis and mineralogy than the existing one. The objective of this research was to determine the weathering degree of Neossolos Litólicos and Neossolos Regolíticos through the evaluation of the minerals alteration in profiles disposed in a climo-litossequence in the RS Plateau, using techniques of chemical dissolution and X rays diffraction. The authors identified two groups of soils with different alteration degree. The first one is composed by the profiles of the West portion of the climo-litossequence (P1, P2 and P3) which has the weathering degree between the bissialitization and the monossialitization, with high content of smectite with hidroxi-Al interlayers (EHE), caulinite and hematite in the clay fraction. The second one is represented by the profiles of the East portion (P4 and P5), with weathering degree between the monossialitization and the ferralitization, with high content of caulinite and goethite and presence of gibbsite and EHE in the clay. The results suggested an higher contribution of the climate on the weathering of the profiles. The ki and kr indexes were not efficient in representing the condition of secondary alteration of the profiles of Neossolos.

Os Neossolos são solos que apresentam inúmeras limitações de uso, principalmente relacionadas à sua profundidade efetiva, e têm sido muito pouco pesquisados no Brasil. Neossolos desenvolvidos sobre rochas sedimentares devem receber especial atenção para que sejam evitados danos ambientais, como a contaminação de aquíferos. O objetivo deste trabalho foi verificar o comportamento da condutividade hidráulica e a capacidade de retenção de água em perfis de Neossolos Litólicos e Neossolos Regolíticos derivados de arenito da Formação Caturrita no Rio Grande do Sul. Foram levantados dados morfológicos e determinadas a granulometria, porosidade, densidade do solo (Ds), condutividade hidráulica saturada (Ks), infiltração básica de água no campo (IB) e retenção de água em amostras de solo e saprolito de seis perfis de Neossolos. Os perfis apresentaram Ds elevada, baixa macroporosidade e alta microporosidade, o que contribuiu para baixa Ks e IB, mesmo em condições de textura franco-arenosa e camada saprolítica altamente fraturada. Os dados de Ks e IB apresentaram elevado coeficiente de variação entre os perfis analisados e entre as repetições de um mesmo perfil. A retenção de água teve valores superiores nas camadas Cr em relação aos horizontes A e volume superior de água disponível às plantas variável entre horizonte A e saprolito para os perfis analisados.

Leptosols and Regosols are soils with a series of restrictions for use, mainly related to the effective depth, which have been poorly studied in Brazil. These soils, when derived from sedimentary rocks should be treated with particular care to avoid environmental damage such as aquifer contamination. The purpose of this study was to verify the behavior of hydraulic conductivity and water retention capacity in profiles of Leptosols and Regosols derived from sandstone of the Caturrita formation in Rio Grande do Sul state. The morphology, particle size distribution, porosity, soil density (Ds), saturated hydraulic conductivity (Ks), basic water infiltration in the field (BI) and water retention were determined in soil and saprolite samples of six soil profiles. High Ds, low macroporosity and high microporosity were observed in the profiles, resulting in a low Ks and BI, even under conditions of sandy texture and a highly fractured saprolite layer. The variation coefficients of data of Ks and BI were high among the studied profiles and between replications of a same profile. Water retention of the studied soils was higher in Cr layers than in the A horizons and the volume of plant-available water greater and variable among A horizons and Cr layers.