ABSTRACT Soils in the Brazilian Pantanal classified as Espodossolos and registered in the literature diverge from the central concept of pedogenesis by podzolization, especially due to the high values of pH and basic cations, although the morphology is similar to that of spodic horizons. In this sense, this study hypothesized that the neutral to alkaline conditions along the edges of the saline basins in the Lower Nhecolândia region do not inhibit the podzolization process nor the development of spodic soils. The objectives were to analyze the attributes of soils with spodic features and evaluate whether they correspond to a podzolization process. Four profiles in a transect in Lower Nhecolândia were selected, where the morphology indicated the presence of a spodic horizon. Three profiles (P1, P2 and P4) were located in a bay and one in the transition between a bay and a “cordilheira” (small elevation between lagoons) (P3). The soils were analyzed for particle size, chemistry and X-ray fluorescence (XRF), as well as organic carbon (C org), total carbon (TC) and XRF of the nodules. The complexity of features and characteristics of soil profiles in the Lower Nhecolândia region indicate multiple pedogenetic processes in this environment. The characteristics of all profiles denote a redoximorphic process: poor profile development (except for P3), mottles formed by precipitation of Fe and Mn oxides, as well as presence of Fe and Mn nodules. The organic matter content of these nodules is mostly greater than or equal to that of the surrounding material, and aluminum is relatively not higher than in the fine earth. This reinforces a rexodimorphic process in the horizons with spodic features. The occurrence of sodic and solodic characters, as well as clay accumulation in P3 also characterize the sodification process. The neutral to alkaline pH values in water, high sum of bases and low C org and Al oxide contents of the studied soils all contradict the occurrence of a podzolization process. However, Fe, Al and C org accumulation in the nodules and some B horizons indicate a spodic character. Also, the fact that SiBCS criteria classify the studied soils as Espodossolos indicates the relevance of establishing limits for chemical attributes, which would adjust the taxonomy of soils with a spodic character according to their pedogenesis.

Pouco se conhece sobre os solos dos sistemas cársticos carbonáticos no Brasil, apesar da sua importância e reconhecida fragilidade. Os objetivos deste estudo foram avaliar a gênese de solos desenvolvidos de rochas calcárias e materiais derivados e caracterizar os atributos desses, contribuindo para o Sistema Brasileiro de Classificação de Solos (SiBCS). Foram estudados três perfis de solos em uma topossequência na Serra da Bodoquena, MS, dispostos nas posições de sopé (P1), terço médio (P2) e topo (P3) de encosta suave-ondulada com pendente longa e perfil longitudinal plano-convexo-plano. Todos os perfis são profundos, com cores bruno-escura nos horizontes superficiais e avermelhada em subsuperfície, além de textura argilosa com incremento de argila em profundidade. O íon cálcio predomina no complexo sortivo, bem como a fração humina entre as frações húmicas. A micromorfologia dos solos revela feições de iluviação de argila em associação com feições de acumulações de CaCO3. Porém, em nenhum dos perfis, os teores de CaCO3 equivalente foram suficientes para o reconhecimento do horizonte cálcico e, ou, petrocálcico, ou de caráter carbonático ou hipocarbonático. Com sequência de horizontes A-Bt (P1); A-E-Bt (P2); e A-Bi (P3), os solos apresentam a seguinte ordem de evolução pedogenética: P1 > P2 > P3. De acordo com o SiBCS, os solos são classificados como Argissolo Vermelho eutrófico nitossólico (P1); Argissolo Vermelho distrófico típico (P2); e Cambissolo Háplico Tb eutrófico típico (P3). Para todos os perfis, no quinto nível aplica-se a classe de atividade de argila - Tm (atividade média), validando proposta recente do SiBCS.

Despite their importance and vulnerability, little is known about the soils in the calcareous karst systems in Brazil. The objective of this study was to evaluate the genesis of soils formed from calcareous parent materials and to characterize their properties, as a contribution to the Brazilian Soil Classification System (SiBCS). Three profiles located at footslope (P1), backslope (P2) and summit (P3) positions in a toposequence with slightly undulated relief, were studied in the Serra da Bodoquena, Mato Grosso do Sul State. All profiles were relatively deep, with dark brown surface horizons and reddish in the subsurface, clayey texture and increasing clay content in deeper layers. Calcium was the dominant exchangeable cation, and humin the main fraction of soil organic matter. Soil micromorphology showed clay illuviation features associated to CaCO3 accumulation. However, the CaCO3 levels were insufficient in the profiles to characterize a calcic or petrocalcic horizon or carbonatic diagnostic properties. The horizons in the profiles were arranged: A-Bt (P1); A-E-Bt (P2) and A-Bw (P3), and the evolution of the soil genesis in the order - P1> P2 > P3. According to the SiBCS, the profiles were classified as eutrophic Red Argisol (P1), dystric Red Argisol (P2), and eutrophic Tb Haplic Cambisol (P3) (equivalent to Udalf, Udult and Udept sub-orders in the USDA Soil Taxonomy, respectively). For all profiles, at the family level the class medium activity clay (Tm) was applied, validating a recent proposal to the SiBCS.

As espécies de leguminosas Piptadenia gonoacantha e Piptadenia paniculata apresentam dificuldade para nodular e crescer em substratos esterilizados, o que dificulta a seleção de estirpes de rizóbio eficientes dessas espécies. As plantas que apresentam nódulos no campo estão micorrizadas. Assim, a boa resposta das plantas no campo pode ser devida à presença de FMAs. O objetivo deste trabalho foi estudar o efeito da micorrização sobre a nodulação e crescimento de plantas de P. gonoacantha e P. paniculata. Os experimentos foram realizados em casa de vegetação, na Embrapa Agrobiologia, Rio de Janeiro. As plantas foram inoculadas com estirpes de rizóbio específicas de cada espécie e com os fungos Gigaspora margarita e Glomus clarum. Ambas as espécies vegetais demonstraram-se altamente responsivas à inoculação com FMAs. Plantas que receberam rizóbios e fungos micorrízicos apresentaram-se noduladas, com maior produção de matéria seca. Já as plantas inoculadas apenas com rizóbio não exibiram nódulos e tiveram menor acúmulo de matéria seca. As plantas de P. gonoacantha apresentaram maior conteúdo de P na parte aérea quando inoculadas com FMAs. Esses resultados indicam que a micorrização é necessária para a nodulação e crescimento satisfatórios das espécies estudadas, e sugere-se a inoculação com FMAs para a seleção de estirpes eficientes de rizóbio em leguminosas com dificuldade de crescimento no sistema convencional de seleção de estirpes.

The leguminous species Piptadenia gonoacantha and Piptadenia paniculata do not nodulate and grow well on sterilized substrates. For this reason selection of efficient rhizobial strains for these species becomes hard to perform. Plants growing in the field are well nodulated and colonized with mycorrhizal fungi. Mycorrhizal colonization may be an explanation for the good plant responses in the field. The effect of mycorrhizal inoculation on nodulation and growth of the woody legume species P. gonoacantha and P. paniculata was studied. The experiments were carried out under greenhouse conditions, at Embrapa Agrobiologia, Rio de Janeiro. The species were inoculated with specific rhizobia and with the mycorrhizal fungi Gigaspora margarita and Glomus clarum. Both tree species were highly responsive to mycorrhizal inoculation. Only the plants inoculated with both rhizobium and mycorrhizal fungi were nodulated. Plants inoculated with both rhizobia and mycorrhizal fungi presented higher dry matter than those inoculated only with rhizobia. P. gonoacantha plants presented higher shoot phosphorus content when inoculated with mycorrhizal fungi. These results show that mycorrhizal inoculation is needed for nodulation and growth of the tree species studied. We suggest the use of mycorrhizal fungi to select rhizobial strains for legumes which have difficulty to grow in Leonard jars.