Clay-humus complexation: Effect of pH and the nature of bonding

Varadachari, Chandrika; Mondal, Ajijul Haque; Nayak, D.C.; Ghosh, Kunal

doi:10.1016/0038-0717(94)90136-8

Cited by 58 publications

(22 citation statements)

References 10 publications

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“…Além disso, a ausência no modelo da mineralogia, predominantemente oxídica nos solos de clima tropical que favorece a formação de complexo organomineral, pode também ter contribuído para a subestimativa dos estoques de COT nos tratamentos com a adubação orgânica, conforme preconizado por Woomer et al (1994). Por outro lado, Varadachari et al (1994) relataram que a quantidade de ácidos fúlvicos adicionada, que permaneceu adsorvida a diferentes minerais de argila, não se relacionou com a superfície específica das argilas. Ainda nesta linha, Hassink (1997) não constatou relação entre o tipo de mineral de argila predominante e o teor de C e N orgânicos associados às frações argila e silte.…”

Section: Comparação De Valores Medidos E Simulados Pelo Modelo Centuryunclassified

Simulação pelo modelo century da dinâmica da matéria orgânica de um Argissolo sob adubação mineral e orgânica

Leite

Mendonça

Machado

2004

Rev. Bras. Ciênc. Solo

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Section: Comparação De Valores Medidos E Simulados Pelo Modelo Centuryunclassified

Simulação pelo modelo century da dinâmica da matéria orgânica de um Argissolo sob adubação mineral e orgânica

Leite

Mendonça

Machado

2004

Rev. Bras. Ciênc. Solo

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“…However, clay -humic substances complexes have been seen to form also at neutral pH through different physical and chemical mechanisms depending on the nature of the clay and of the saturating cation, and on the electrolyte concentration (Kodama and Schnitzer, 1968;Rashid et al, 1972;Theng, 1976;Varadachari et al, 1994). The probable modes of interaction in clay -humus complexes included anion and ligand exchange on the crystal edges, cation or water bridges on the basal surface, H-bonding to the siloxane or gibbsite sheet, van der Waals forces, trapping in crystal pores and intradomain regions, adsorption in interlayer spaces (Schnitzer and Kodama, 1966;Varadachari et al, 1991).…”

Section: Microstructure Of the Smectite -Humic Acid Associationmentioning

confidence: 99%

“…Our preparation procedure did not include any attempt to eliminate the weakly bound humic acid, consequently, we observed by cryo-SEM a suspension in which humic acid and smectite should be associated by both strong and weak forces. According to Varadachari et al (1994), in such suspension, water bridges must bond humic substances to the cations at the surface of the clay mineral. The cryo-SEM images (Fig.…”

Section: Microstructure Of the Smectite -Humic Acid Associationmentioning

confidence: 99%

Characterization of model soil colloids by cryo-scanning electron microscopy

et al. 2004

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The cryo-scanning electron microscopy (cryo-SEM) consists of the SEM examination of samples whose microstructure has been fixed by plunge-freezing into a liquid with a high thermal conductivity, such as nitrogen slush. The advantage of this cryopreparation method is that it can transform the interstitial water of the samples into ice whose crystalline domain dimensions (a few nm to a few tens of nanometers) do not exceed those of the finest details that can be observed, and thus do not modify sample morphology at the observation scale. Cryo-SEM was applied to the study of wet-state model soil colloids: a soil humic acid, a commercial smectite, a synthetic ferrihydrite and their binary and ternary associations. The cryo-SEM images have given the following information: The smectite suspension behaved as a non-oriented network, the ferrihydrite suspension was formed from particles of various shapes and dimensions, and the humic acid exhibited a sponge-like structure. The micromorphology of the ferrihydrite -humic acid association was close to that of pure ferrihydrite, while the smectite-containing associations recalled the basic network of the smectite. The comparison of the images obtained by cryo-SEM, and by conventional SEM performed on the same samples after they had been freeze-dried, points out the morphologic modifications deriving from the conventional drying process. Besides SEM investigation, the soil colloids have been characterized by X-ray diffractometry, FTIR spectroscopy, elementary analysis and surface area determination. D

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“…In oxidic and kaolinitic soils, humic acids (HA) are less sorbed than fulvic acids (FA). This difference can be attributed to the influence of carboxylic groups, which are more abundant in FA and contribute to the sorption of HS by oxides (Varadachari et al, 1995). There is a selective uptake of lower molecular weight material in 2:1 aluminosilicates (Feng et al, 2005), which results in lower HA sorption in highly weathered soils.…”

Section: Introductionmentioning

confidence: 99%

Organic matter quality and dynamics in tropical soils amended with sugar industry residue

Busato

Leão

Baldotto

et al. 2012

Rev. Bras. Ciênc. Solo

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SUMMARYSoil organic matter depletion caused by agricultural management systems have been identified as a critical problem in most tropical soils. The application of organic residues from agro-industrial activities can ameliorate this problem by increasing soil organic matter quality and quantity. Humic substances play an important role in soil conservation but the dynamics of their transformations is still poorly understood. This study evaluated the effect of compost application to two contrasting tropical soils (Inceptisol and Oxisol) for two years. Soil samples were incubated with compost consisting of sugarcane filter cake, a residue from the sugar industry, at 0, 40, 80, and 120 Mg ha -1 . Filter cake compost changed the humic matter dynamics in both content and quality, affecting the soil mineralogical composition. It was observed that carbon mineralization was faster in the illitecontaining Inceptisol, whereas humic acids were preserved for a longer period in the Oxisol. In both soils, compost application increased fulvic acid contents, favoring the formation of small hydrophilic molecules. A decrease in fluorescence intensity according to the incubation time was observed in the humic acids extracted from amended soils, revealing important chemical changes in this otherwise stable C pool. Index-terms: humic substances, soil electrical charges, stable carbon, filter cake.(1) Part of the doctoral thesis presented by the first author at the Universidade Estadual do Norte Fluminense Darcy Ribeiro, UENF, Campos dos Goytacazes (RJ

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Clay-humus complexation: Effect of pH and the nature of bonding

Cited by 58 publications

References 10 publications

Simulação pelo modelo century da dinâmica da matéria orgânica de um Argissolo sob adubação mineral e orgânica

Simulação pelo modelo century da dinâmica da matéria orgânica de um Argissolo sob adubação mineral e orgânica

Characterization of model soil colloids by cryo-scanning electron microscopy

Organic matter quality and dynamics in tropical soils amended with sugar industry residue

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