991 resultados para Simo Penttilä


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A espectroscopia de reflectncia difusa (ERD) pode ser utilizada como alternativa para quantificao de atributos como granulometria e matria orgnica do solo (MOS). Essa tcnica pode ser opo para quantificar esses atributos em grande volume de amostras de solos, visto ser rpida, com menor custo e sem a gerao de resduos qumicos. O objetivo deste estudo foi desenvolver modelos usando anlise de regresso linear mltipla para predizer o teor de argila, areia, silte e MOS, utilizando dados de ERD em uma rea de relevo e geologia complexa localizada na regio central do Rio Grande do Sul. No estudo, foram utilizadas 303 amostras coletadas na profundidade de 0,00-0,20 m para determinar os teores de argila, areia, silte e MOS por meio da anlise laboratorial e de reflectncia espectral. O desempenho dos modelos de predio apresentaram bons resultados, com capacidade de explicao da varincia de 77 e 72 % para areia e argila, respectivamente. Mesmo com a complexidade geolgica e pedolgica, os resultados evidenciaram que a tcnica promissora, sendo possvel a aplicao dessa tcnica para predio da granulometria e teor de MOS.

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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.

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Plant species that naturally occur in the Brazilian Caatinga(xeric shrubland) adapt in several ways to these harsh conditions, and that can be exploited to increase crop production. Among the strategic adaptations to confront low water availability, desiccation tolerance stands out. Up to now, the association of those species with beneficial soil microorganisms is not well understood. The aim of this study was to characterize Tripogon spicatusdiazotrophic bacterial isolates from the Caatingabiome and evaluate their ability to promote plant growth in rice. Sixteen bacterial isolates were studied in regard to their taxonomic position by partial sequencing of the 16S rRNA gene, putative diazotrophic capacity, in vitro indole-acetic acid (IAA) production and calcium phosphate solubilization, metabolism of nine different C sources in semi-solid media, tolerance to different concentrations of NaCl to pHs and intrinsic resistance to nine antibiotics. Finally, the ability of the bacterial isolates to promote plant growth was evaluated using rice (Oryza sativa) as a model plant. Among the 16 isolates evaluated, eight of them were classified as Enterobacteriaceae members, related to Enterobacter andPantoeagenera. Six other bacteria were related toBacillus, and the remaining two were related toRhizobiumand Stenotrophomonas.The evaluation of total N incorporation into the semi-solid medium indicated that all the bacteria studied have putative diazotrophic capacity. Two bacteria were able to produce more IAA than that observed for the strain BR 11175Tof Herbaspirillum seropedicae.Bacterial isolates were also able to form a microaerophilic pellicle in a semi-solid medium supplemented with different NaCl concentrations up to 1.27 mol L-1. Intrinsic resistance to antibiotics and the metabolism of different C sources indicated a great variation in physiological profile. Seven isolates were able to promote rice growth, and two bacteria were more efficient than the reference strainAzospirillum brasilense, Ab-V5. The results indicate the potential of T. spicatus as native plant source of plant growth promoting bacteria.

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A integrao de mtodos qumicos de extrao e a difrao de raios-X podem ampliar o entendimento das formas de reserva de K+ nas fraes do solo e o seu potencial de liberao para as plantas. Os objetivos deste estudo foram empregar os mtodos de extrao qumica para estimar a reserva mineral de K+ das fraes areia, silte e argila de solos subtropicais, associar os mecanismos de extrao com as formas liberadas do nutriente e acompanhar a dinmica dessa liberao em estudo de cintica. As fraes areia, silte e argila dos horizontes A e Bt de trs Argissolos subtropicais foram submetidas extrao de formas no trocveis e estruturais de K+pelos mtodos: cido oxlico 0,01 mol L-1 (cintica de liberao at o tempo acumulado de 2.889 h); HNO3 1 mol L-1 fervente; NaHSO4 na forma de cristais; e HNO3/HF/H2SO4 concentrados (teores totais). A frao argila tambm foi submetida a tratamento com NaOH 5 mol L-1. As esmectitas dioctaedrais na frao argila foram consideradas importantes na dinmica de liberao de formas de reserva de K+. A maior e menor liberao de formas no trocveis e estruturais de K+ foram pela extrao com NaHSO4 e pelo ataque cido com HNO3, respectivamente. Com os dados da cintica de liberao de K+ possvel concluir que as plantas cultivadas, nos Argissolos estudados, no longo dos anos nos solos estariam bem nutridas a partir de formas no trocveis e estruturais de K+.

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ABSTRACT Diffuse reflectance spectroscopy (DRS) is a fast and cheap alternative for soil clay, but needs further investigation to assess the scope of application. The purpose of the study was to develop a linear regression model to predict clay content from DRS data, to classify the soils into three textural classes, similar to those defined by a regulation of the Brazilian Ministry of Agriculture, Livestock and Food Supply. The DRS data of 412 soil samples, from the 0.0-0.5 m layer, from different locations in the state of Rio Grande do Sul, Brazil, were measured at wavelengths of 350 to 2,500 nm in the laboratory. The fitting of the linear regression model developed to predict soil clay content from the DRS data was based on a R2 value of 0.74 and 0.75, with a RMSE of 7.82 and 8.51 % for the calibration and validation sets, respectively. Soil texture classification had an overall accuracy of 79.0 % (calibration) and 80.9 % (validation). The heterogeneity of soil samples affected the performance of the prediction models. Future studies should consider a previous classification of soil samples in different groups by soil type, parent material and/or sampling region.

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