Structure represents one of the main soil physical attributes indicators. The soil porous system (SPS) is directly linked to the soil structure. Water retention, movement, root development, gas diffusion and the conditions for all soil biota are related to the SPS. Studies about the influence of tillage systems in the soil structure are important to evaluate their impact in the soil quality. This paper deals with a detailed analysis of changes in the soil structure induced by conventional (CT) and no-tillage (NT) systems. Three different soil depths were studied (0-10, 10-20 and 20-30 cm). Data of the soil water retention curve (SWRC), micromorphologic (impregnated blocks) (2D) and microtomographic (mCT) (3D) analyses were utilized to characterize the SPS. Such analyses enabled the investigation of porous system attributes such as: porosity, pore number and shape, pore size distribution, tortuosity and connectivity. Results from this study show a tri-modal pore size distribution (PSD) at depths 0-10 and 10-20 cm for the soil under CT and a bi-modal PSD for the lower layer (20-30 cm). Regarding the soil under NT, tri-modal PSDs were found at the three depths analyzed. Results based on the micromorphologic analysis (2D) showed that the greatest contribution to areal porosity (AP) is given by pores of round (R) shape for CT (52%: 0-10 cm; 50%: 10-20 cm; 67%: 20-30 cm). Contrary to the results observed for CT, the soil under NT system gave the greatest contribution to AP, for the upper (0-10 cm) and intermediate (10-20 cm) layers, due to the large complex (C) pore types. For the mCT analysis, several types of pores were identified for each soil tillage system. Small differences in the macroporosity (MAP) were observed for the 0-10 and 20-30 cm between CT and NT. A better pore connectivity was found for the 0-10 cm layer under NT. 2016 Elsevier B.V. All rights reserved.
In the soil science, a direct method that allows the study of soil pore distribution is the bi-dimensional (2D) digital image analysis. Such technique provides quantitative results of soil pore shape, number and size. The use of specific softwares for the treatment and processing of images allows a fast and efficient method to quantify the soil porous system. However, due to the high cost of commercial softwares, public ones can be an interesting alternative for soil structure analysis. The objective of this work was to evaluate the quality of data provided by the Image J software (public domain) used to characterize the voids of two soils, characterized as Geric Ferralsol and Rhodic Ferralsol, from the southeast region of Brazil. The pore distribution analysis technique from impregnated soil blocks was utilized for this purpose. The 2D image acquisition was carried out by using a CCD camera coupled to a conventional optical microscope. After acquisition and treatment of images, they were processed and analyzed by the software Noesis Visilog 5.4 ® (chosen as the reference program) and ImageJ. The parameters chosen to characterize the soil voids were: shape, number and pore size distribution. For both soils, the results obtained for the image total porosity (%), the total number of pores and the pore size distribution showed that the Image J is a suitable software to be applied in the characterization of the soil sample voids impregnated with resin. Index terms:Soil structure, image analysis, thin section, soil porous system, soil pore size distribution, Ferralsols. reSumoNa ciência do solo, um método direto que permite o estudo da distribuição dos poros do solo é aquele baseado na análise de imagens digitais em duas dimensões (2D). Tal técnica fornece resultados quantitativos do formato, número e tamanho de poros do solo. O uso de programas específicos para o tratamento e processamento de imagens possibilita um método rápido e eficiente para quantificar o sistema poroso do solo. No entanto, pelo alto custo dos programas comerciais, os programas livres podem ser uma interessante alternativa para análises da estrutura do solo. Objetivou-se, nesse trabalho, avaliar a qualidade dos dados fornecidos pelo programa livre "Image J", usado para caracterizar o espaço poroso de dois latossolos (Latossolo Vermelho-Amarelo e Latossolo Vermelho) da região sudeste do Brasil. A técnica de análise de distribuição de poros, a partir de blocos impregnados com resina foi utilizada nesse trabalho. As imagens 2D obtidas usando uma câmera CCD acoplada a um microscópio óptico convencional. Após a aquisição e tratamento das imagens, as mesmas foram processadas e analisadas, usando os programas "Noesis Visilog 5.4 ® " (selecionado como programa padrão) e "ImageJ". Os parâmetros escolhidos para caracterizar o espaço poroso foram: formato, número e distribuição de tamanho de poros. Para ambos os solos, os resultados obtidos para a porosidade total pela imagem (%), número total de poros e distribuição de tamanho de poros mostraram q...
analysis of the soil pore system represents an important way of characterizing soil structure. properties such as the shape and number of pores can be determined through soil pore evaluations. this study presents a three-dimensional (3d) characterization of the shape and number of pores of a sub-tropical soil. to do so, a second generation X-ray microtomograph equipped with a plain type detector was employed. a voltage of 120 kV and current of 80 ma was applied to the X-ray tube. the soil samples analyzed were collected at three different depths (0-10, 10-20, and 20-30 cm). the results obtained allowed qualitative (images) and quantitative (3d) analyses of the soil structure, revealing the potential of the microtomographic technique, as well as the study of differences in soil macroporosity at different depths. macroporosity was 5.14 % in the 0-10 cm layer, 5.10 % in the 10-20 cm layer, and 6.64 % in the 20-30 cm layer. the macroporosity of unclassified pores (UN) was 0.30 % (0-10 and 10-20 cm) and 0.40 % (20-30 cm), while equant pores (eQ) had values of 0.01 % at the three depths under analysis.Keywords: soil structure, pore size distribution, soil porosity, image analysis, soil microstructural components. RESUMO: CARACTERIZAÇÃO
ResumoO ensino e aprendizagem ao serem conduzidos por meio da problematização, direcionada e inserida em um tema de interesse proporciona diversos caminhos para a construção do conhecimento dos estudantes. Em um ambiente dinâmico e de diálogo deparou-se com questões levantadas pelos próprios estudantes, que abrangem diversos conceitos inseridos no tema: isolantes e condutores térmicos. Estes questionamentos puderam ser compreendidos, por meio de uma atividade experimental que teve como objetivo principal medir condução de calor em diferentes tipos de materiais: tanto isolantes quanto condutores. Pretendeu-se conduzir o aluno a investigar e construir o conhecimento a partir da elaboração de hipóteses, de modo a encontrar respostas a seus questionamentos utilizando-se da linguagem científica tendo por base as ideias de Paulo Freire, de Ausubel e de Moreira, e assim, os alunos utilizassem seus conhecimentos prévios de modo a estabelecer uma relação com sua realidade e com seus interesses. Palavras-chave:Problematização, atividade experimental, condutores e isolantes térmicos. Abstract Contribution to science education through an experimental activity about thermal conductivityTeaching and learning were driven through the questioning, directed and inserted into a topic of student interest provide various ways for the construction of knowledge these students. In a dynamic environment and dialogue was faced
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