ABSTRACT Bases are chemical species that donate electrons, accept protons, or release hydroxyls (OH–) in aqueous solution. In Soil Science, “base saturation”, “exchangeable bases” or “basic cations” has been widely used to distinguish Ca2+, Mg2+, Na+, and K+ from H+ and Al3+ cations. This terminology is confusing since none of these cations are truly a base in chemistry sense. However, in the absence of the proposition of a correct term, the term “base saturation” remains in use nowadays, causing confusion among students, professionals, and even among professors and researchers in Soil Science, as it leads to the erroneous interpretation that the soil acidity can be corrected by adding these cations to the soil. Here, we present the historical background of this nomenclature and a theoretical foundation that justifies the abolition of the use of these terms in Soil Science. We consider that the most correct is to call it “Ca-Mg-K-Na saturation”, which, despite being long, would refer directly and without any misinterpretation of the terminology. In Soil Fertility, the “base saturation” is often calculated only as a function of the sum of Ca, Mg, and K, since the Na content is negligible in most tropical and subtropical soils. Thus, one could use the term “Ca-Mg-K saturation”. Likewise, it is also suggested to abolish the use of the term “sum of bases” and use the term “sum of Ca-Mg-K” or “sum of Ca-Mg-K-Na” instead when necessary.

RESUMO O intemperismo do material de origem é o processo inicial que garantirá ao solo maior ou menor fertilidade, tornando o estudo desse processo fundamental para entender a dinâmica do solo. Grande parte dos estudos de intemperismo é baseada em índices que calculam a taxa de dissolução dos feldspatos (CIA, CIW e PIA, por exemplo) muitas vezes não refletindo a complexidade do intemperismo ocorrendo no perfil de solo. Outras metodologias- como balanço geoquímico, diferença elementar (DE) e índice W- têm sido desenhadas para melhorar esses estudos. Avaliar se essas metodologias serão mais eficientes que os índices CIA, CIW e PIA para apontar as variações intempéricas em perfis recentes desenvolvidos de basalto é o objetivo desse trabalho. Foram utilizados dados de óxidos principais para calcular o balanço geoquímico, DE, CIA, CIW, PIA e W e analisar a intensidade do intemperismo em dois perfis originados de basalto no Estado de São Paulo. Foram fatorados também os índices Ki e Kr e a relação Fe o/Fed e analisada a mineralogia dos horizontes dos solos e da rocha de origem. O índice W e a DE mostraram maior variação intempérica que CIA, CIW e PIA. O balanço geoquímico, a mineralogia e as razões Ki e Kr, Feo /Fed foram eficientes em explicar as variações que ocorreram entre os horizontes. A junção da DE com o balanço geoquímico trouxe novas informações para a análise do intemperismo que a observação isolada de CIA, CIW e PIA.

ABSTRACT Weathering of the parent material is the initial process that plays an essential role in soil fertility. The study of this process has become crucial to better understand soil dynamics. Most studies on weathering are based on indexes that calculate the feldspar dissolution rate (for example, CIA, CIW, and PIA) which not always reflect the complexity in the soil profile. Other methodologies have been designed to improve these approaches, such as geochemical balance, difference of elemental contents (DE), and the W index. This work aim to assess the efficiency of these methods to identify variations in recent soil profiles developed from diabase as compared to the CIA, CIW, and PIA indexes. Data on the main oxides were used to calculate the geochemical balance, DE, CIA, CIW, PIA, and W indexes to analyze weathering intensity in two profiles originated from diabase in the São Paulo State, Brazil. The Ki and Kr indexes and Feo /Fed ratio were also factored and we analyzed the mineralogy of soil horizons and the source rock. The W index and DE presented greater weathering variation than the CIA, CIW, and PIA in both profiles. The geochemical balance, mineralogy, and the Ki, Kr and Feo /Fed ratios explained the variations between the horizons. The DE and geochemical balance together generated new information for the analysis of the weathering process than the isolated indexes.

ABSTRACT Soils in alluvial plains of the lower course of the Acaraú River, Ceará State, Brazil, are weakly developed and have a complex distribution in the landscape. This study reports the pedogenic characterization of such soils in an effort to understand their formation. Soil pits were opened in four representative sites, profile morphology was described, and soil samples were collected for chemical, physical, mineralogical, and micromorphological analyses. All profiles had weak pedogenic development, as inferred from their morphological characteristics, lack of B horizon, and high silt/clay ratio. Organic carbon and particle size distributions were heterogeneous in Fluvisol, Planosol, and Solonchak, in agreement with their sedimentary nature. Intrinsic characteristics of each profile indicated variations in pedogenic processes related to depositional conditions, which, in turn, were determined by the alluvial nature of sediments and water table dynamics. Consequently, Fluvisols at higher elevations showed reduced pedogenic development. In adjacent areas, Planosols showed pores filled with clay minerals and a texture gradient, indicative of past lessivage. Vertisol was identified in small depressions and exhibited intense pedoturbation and high sodium concentration in deep layers. Solonchak had a high degree of hydromorphism, high sodium concentration, and high electrical conductivity. The distinct pedogenesis of alluvial plain soils in Northeastern Brazil is evidenced by their morphological, chemical, and physical properties.

ABSTRACT Information is scarce on the genesis and classification of soils derived from calcareous rocks in the Northeastern region of Brazil. This study describes the morphological, physical, chemical, mineralogical, and micromorphological properties of four soil profiles (P1-P4) located in the Apodi Plateau. A pedogenesis hypothesis and soil classification, according to the Brazilian System of Soil Classification (SiBCS), are proposed for these profiles. The interactions between parent material, surface topography and climate affected the pedogenesis processes and soil properties, although the calcareous nature of the parent material most affected the soil morphology and chemical properties. The sand fraction contained mainly quartz and calcite, and a smaller amount of mica. Smectite and interstratified illite-smectite occurred in the clay fraction of profile P1 and in some horizons of P2 (Ccmќ and Ccrќ) and P3 (2Ccrќ). Kaolinite predominated in profiles P2, P3, and P4; where as illite and vermiculite were present in the Bicќ, Bcќ, Bcmќ horizons of P2, in Bt2c of P3, and in C of P4. The mineralogy showed illite, hematite, and goethite, and anatase in a number of horizons. Micromorphological analysis of P2 indicated a strong cementation of Bcmќ and Ccmќ by calcium carbonate, and other properties indicate the formation of a petrocalcic horizon, but this horizon lacked lateral continuity in the profile. Therefore, the parapetrocalcic term is proposed for classifying P2 in the fourth level of the SiBCS. The 3Biќ-P1 horizon exhibited calcite coating and iron coating or quasi-coating, indicating distinct pedogenesis processes occurring under different environmental conditions. Likewise, the occurrence of petroplinthite in P2 indicates that climatic conditions during its formation differed from present conditions, and both situations are interpreted as evidence that the soils were formed by polygenetic processes. In the SiBCS classification, the soils are classified as Cambissolo Háplico Carbonático vertissólico (P1), Cambissolo Háplico Carbonático concrecionário (P2), Luvissolo Crômico Pálico petroplíntico (P3), and Neossolo Litólico Carbonatico típico (P4); and a new class (parapetrocálcico concrecionário) is proposed for P2 in the fourth level.

Os Neossolos Regolíticos apresentam baixo potencial de uso devido a sua pequena profundidade efetiva, à presença de pedregosidade/rochosidade, ao contato lítico próximo à superfície e à ocorrência frequente em terrenos declivosos. Análises mais detalhadas são necessárias para a melhor interpretação desses solos, visto que a filtragem da água de percolação, retenção de solutos e fluídos e sua possível transformação são de interesse ambiental. Nesse sentido, este estudo gerou informações sobre a infiltração de água em cinco áreas de Neossolos Regolíticos, na região do Rebordo do Planalto do Rio Grande do Sul. Para cada área foram descritos e analisados três perfis, sendo a infiltração de água determinada pelo método dos duplos anéis concêntricos. Mesmo com idêntica classificação taxonômica até o quarto nível categórico, os Neossolos apresentaram variações no seu comportamento hídrico, inclusive quando comparados entre os perfis do mesmo ponto de coleta. Os dados sugerem que a infiltração, nesses Neossolos, é influenciada pela configuração de fraturas do saprolito, granulometria, condições de relevo e uso do solo.

Neossolos Regolíticos (Regosols) are fragile from a natural resource perspective because of their small depth, stones and/or rocks presence, near surface lithic contact, fractures in saprolite and frequent occurrence in steep slopes. These soils requires more specific analysis for a better interpretation of their capacity to filtrate water, retain and transform solute and fluids, contributing to the maintenance of the water quality that reaches the groundwater. In that sense, this study generates information on water infiltration in five areas from the the Rio Grande do Sul plateau edge. Three profiles were described and analyzed for each Regosol and the water infiltration was performed whit the double rings method. Even showing the same taxonomic classification, the Regosols showed hydraulic variation behavior, even though when compared among the profiles from the same location. The data suggest that the water infiltration in the Regosols is affected by the saprolite fracture configurations, granulometry, relief conditions and soil use.

A relação entre as características e a utilização das informações do mapa do levantamento de reconhecimento de solos do estado do Rio Grande do Sul na escala de 1:750.000 e dos mapas semidetalhados dos municípios de São João do Polêsine - RS (SJP), na escala de 1:20.000, e São Pedro do Sul - RS (SPS), na escala 1:50.000, foi estudada. Para este fim, comparou-se a área total em hectares e a percentagem de área do município ocupada por cada classe de solo delineada nos diferentes mapas. Foram verificadas grandes diferenças quanto ao número, tipo e distribuição das classes de solos delineadas. A ampliação de mapas de pequena escala não permite identificar e delinear solos que ocorrem na área estudada e que não foram delineadas por problemas de escala. Para planejamento de uso dos solos de propriedades rurais, microbacias e municípios, levantamentos detalhados e semidetalhados devem ser elaborados.

The relationship between the characteristics and use of information of the reconnaissance soil survey map of the state of Rio Grande do Sul in the scale of 1:750.000 and the semidetailed maps of the São João do Polêsine county (SJP), in the scale of 1:20.000, and São Pedro do Sul county (SPS), in the scale 1:50.000 was studied. For this purpose the total area, in hectares, was compared, and the percentage of area of the counties occupied by the different soil classes, delineated in different maps. Differences were verified concerning the main classes of soils delineated in the maps and also in the percentage of distribution of the area occupied by the classes in these maps. For this reason, the enlargement of soil maps of small scale doesn’t permit to identify and to delineate soils that occur in the studied area, and which were not mapped due to the limitations in scale. For planning use of soils in watersheds, counties and farm areas, detailed and semidetailed surveys should be elaborated.

A forte pressão provocada pela expansão urbana desordenada sobre os recursos naturais, principalmente os solos, tem provocado danos, muitas vezes de difícil reparo. A grande concentração populacional em centros urbanos cada vez maiores tem dirigido a atenção de diferentes profissionais para o recurso solo, no sentido de entender sua dinâmica para minimizar sua degradação. No entanto, a falta de conhecimento sobre as propriedades, bem como sobre a aptidão dos solos sob uso urbano tem provocado o seu mau uso, resultando em processos como compactação, erosão, deslizamentos e inundações, assim como poluição com substâncias orgânicas, inorgânicas e patógenos, aumentando os custos do desenvolvimento afetando toda a sociedade. Neste sentido, este texto discute como o conhecimento pedológico pode diminuir os efeitos negativos provocados pelo processo de urbanização.

The strong pressure caused by the disordered urban expansion over the natural resources, mainly the soils, has caused damages, many times difficult to repair. The great population concentration in urban centers getting larger and larger has been driving the attention of different professionals to soil resource, in the sense of understanding its dynamics to minimize its degradation. The lack of knowledge related to the soils properties and capability promote their inappropriate use, resultig in degrading processes as compaction, erosion, sliding, floods, and organic, inorganic and patogenic pollution, increasing the cost of development and affecting the whole society. This text discusses how pedologic knowledge can reduce the negative effects caused by the urbanization process.