RESUMOO objetivo deste trabalho foi estudar a variabilidade espacial do pH da pasta de saturação (pHps), condutividade elétrica do extrato de saturação (CEes) e porcentagem de sódio trocável (PST) de um solo aluvial afetado por sais. Foram coletadas amostras de solo nas camadas 0-20, 20-40 e 40-60 cm, numa área do Projeto de Irrigação Capoeira, localizado em São José do Bonfim, Estado da Paraíba, utilizando-se um esquema sistemático de amostragem numa malha regular de 10 x 15 m. Os dados foram analisados através da estatística descritiva e geoestatística. Verificou-se baixa variabilidade para o pHps (CV < 12 %) e elevada para a CEes e PST (CV > 60 %). Modelos esférico e gaussiano foram ajustados aos semivariogramas das variáveis que apresentaram estrutura de dependência espacial, tendo-se obtido alcances variando de 20 a 40 m. Os mapas de isolinhas da combinação da CEes e PST permitiram visualizar o padrão de variabilidade da salinidade e sodicidade, constituindo-se em uma ferramenta para a definição de estratégias de manejo edáfico e recuperação da área afetada. Palavras ABSTRACTThe objective of this work was to study the spatial variability of pH of saturation paste (pHsp), the electrical conductivity of saturation extract (ECe) and the exchangeable sodium percentage (ESP) in an alluvial salt affected soil. Soil samples were collected in 0 -20, 20 -40 and 40 -60 cm depths, in an area of the Irrigation Project of Capoeira, located in São José do Bonfim -Paraíba (Brazil), following a systematic scheme of sampling in a 10 x 15 m mesh. The data were analyzed through the descriptive statistics and geostatistics. Low variability was observed for the pHsp (CV<12%) in constrast to ECe and ESP (CV> 60%). Spherical and gaussian models were adjusted to the experimental semivariograms of the variables that presented a spatial dependence structure. Structures of spatial dependence, with range varying from 20 to 40 m were observed. The maps of isohypsas of the combination of ECe and ESP allowed the visualization of the pattern of the salinity and sodicity variability, constituting a tool for the definition of soil management and reclamation of the affected area.

Although anthropogenic dark earth (ADE) is generally found in non-floodable land, it also occurs on floodplains but, there is no information about the chemical and physical characteristics of ADE in this environment. In this study, we propose to check the hypothesis that a Gleysol, classified as ADE, presents improved chemical and physical conditions than an adjacent soil, no anthropogenic. Thus, the objective of this study was to characterize the chemical and physical properties of the top layer of two ADE profiles in a Gleysol and compare them with an adjacent soil. Samples were taken from two areas classified as ADE in Bragança, Pará State, Brazil, at the "Jabuti" archaeological site, and from an adjacent non-anthropogenic site. Disturbed and undisturbed soil samples were collected at the soil depth of 0.05-0.10 m for chemical (pH, potential acidity, exchangeable cations, and soil organic carbon) and physical (soil particle size distribution, particles density, water retention curve, total porosity, microporosity, macroporosity, and bulk density) analysis. The two areas of ADE in a Gleysol, showed improved soil chemical properties compared to the adjacent soil, particularly in relation to phosphorus and calcium levels that contributed to higher cation exchange capacity which, in turn, was positively related to organic carbon content. Changes in soil physical properties were less noticeable but both areas of ADE presented higher water retention capacity, particularly at low tension. The improved conditions of the ADE soil under Gleysols shows that these areas are adequate for soil cultivation, especially with plants adapted to floodplain.KEYWORDS: Anthropic horizon, Soil organic carbon, Soil quality, Floodplain soils Propriedades físicas e químicas de Terra Preta Antropogênica em Bragança, Pará, Amazônia Oriental RESUMOEmbora as terras pretas antropogênicas (TPA) geralmente são encontradas em áreas de terra firme, elas também ocorrem em áreas e várzeas, mas, não há informações sobre as características químicas e físicas de TPA neste ambiente. Neste estudo, nós propomos verificar a hipótese de que um Gleissolo, classificado como TPA, apresenta melhores condições químicas e físicas do que o solo adjacente, não antropogênico. Assim, o objetivo do estudo foi caracterizar as propriedades químicas e físicas da camada superficial de dois perfis de TPA em um Gleissolo e compará-los com um solo adjacente. Amostras de solo foram coletadas em duas áreas classificadas como TPA em Bragança, Estado do Pará, Brasil, no sítio arqueológico "Jabuti" e em uma área adjacente não antropogênica. Amostras de solo com estrutura deformada e indeformada foram coletadas na profundidade de 0,05-0,10 m para análises químicas (pH, acidez potencial, cátions trocáveis, e carbono orgânico do solo) e físicas (distribuição do tamanho das partículas do solo, densidade de partículas, curva de retenção de água, porosidade total, microporosidade, macroporosidade e densidade do solo). As duas áreas de TPA em Gleissolo, apresentaram melhores ...

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This study aimed to characterize soil carbon dioxide (CO 2) emission associated with soil pore distribution in an Oxisol and Ultisol under chiseling in the planting row and in total area for sugarcane (Saccharum officinarum) cultivation. The experimental design was a large paired-plot design. Treatments consisted of chiseling in the planting row (CPR) and chiseling in total area (CTA) in an Oxisol and Ultisol. Soil CO 2 emission, soil temperature, and soil moisture were assessed over 12 days in the Oxisol and 11 days in the Ultisol at a depth of 0-0.10 m. Organic carbon associated with minerals (OCAM) and particulate organic carbon (POC) were also assessed. OCAM, pore class C2 (0.05 ≤ ɸ < 0.1 mm), soil moisture, and soil temperature explained 72 and 53% of the variability of soil CO 2 emission in CPR and CTA, respectively. In the Ultisol, pore class C1 (ɸ ≥ 0.1 mm) and OCAM explained 82% of the variability of soil CO 2 emission in CPR. In CTA, soil moisture, OCAM, and POC explained 67% of the variability of soil CO 2 emission. In the Oxisol, CPR and CTA affected soil structure, causing changes in both soil porosity and soil CO 2 emission. In the Oxisol, the lowest average value of soil CO 2 emission (2.8 μmol m −2 s −1) was observed in CPR whereas its highest value (3.4 μmol m −2 s −1) was observed in CTA. In the Ultisol, soil tillage (CPR and CTA) did not affect soil CO 2 emission. These results indicate that the intensity of soil tillage in more clayey textured soils favors soil CO 2 emission possibly due to a higher carbon availability for microbial activity when compared to more sandy textured soils. A less intensive soil tillage can be considered as an efficient strategy to reduce soil CO 2 emission and hence soil organic carbon losses. Thus, this management strategy proved to be efficient in terms of mitigating greenhouse gas emissions, reducing the contribution of agriculture to global climate change.

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