Microaggregates in red earths and related soils in East and Central Africa, their classification and occurrence

Trapnell, C. G.; Webster, R.; Hesse, P. R.

doi:10.1111/j.1365-2389.1986.tb00012.x

Cited by 33 publications

(28 citation statements)

References 6 publications

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“…The result of this intense fissuration of the porphyric groundmass is the creation of a network of planar voids isolating polyedric microaggregates (PM) that are later included into the enaulic soil matrix by pedoturbation processes. Trapnell & Webster (1986) observed the same process of microaggregate formation, calling them fragmental aggregates.…”

Section: Origin Of the Microaggregate Structurementioning

confidence: 85%

“…Consequently, the formation of the microaggregate structure can be considered complex due to the existence of various hypotheses that may explain their formation and shape. Among them, a biological origin of microaggregates (Stoops, 1983;Eschenbrenner, 1986;Miklós, 1992;Vidal-Torrado, 1994), a geochemical origin (Chauvel et al, 1978;Cambier, 1986;Pedro, 1987;Santos et al, 1989) and finally a physical origin by fragmentation (Muller, 1977;Trapnell & Webster, 1986) may be involved.…”

Section: Introductionmentioning

confidence: 99%

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Origin of microaggregates in soils with ferralic horizons

Cooper

Vidal‐Torrado

Chaplot

2005

Sci. agric. (Piracicaba, Braz.)

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Microaggregates that characterize ferralic soils have been hypothesized to have physical, geochemical and/or biological origins. Despite of many studies, the hierarchy between these processes that form microaggregates has seldom been reported. The objective of this work was to study the genesis of microaggregates in a sequence of Ferralic Nitisols developed on Quaternary red clayey sediments and diabase in Piracicaba (SP), Brazil. This issue was tackled by combining optical microscopy, image analysis, scanning electron microscopy and elemental iron quantifications by X-ray fluorescence. Micromorphological investigations showed three different types of microaggregates: (i) oval microaggregates with well sorted quartz grains in their interior; (ii) oval microaggregates without or with poorly sorted quartz grains in their interior; and (iii) dense polyedric microaggregates. These morphological evidences, together with the elemental iron determinations and scanning electron microscopy, revealed the contribution of more than one process for microaggregate formation: (i) the mechanical action of the mesofauna would form the first type of microaggregates (ii) geochemical and biological processes would form the second type and (iii) the fissuration of the soil matrix by expansion and compression processes would form the third type.

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Section: Origin Of the Microaggregate Structurementioning

confidence: 85%

Section: Introductionmentioning

confidence: 99%

Origin of microaggregates in soils with ferralic horizons

Cooper

Vidal‐Torrado

Chaplot

2005

Sci. agric. (Piracicaba, Braz.)

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“…The presence of such layers in soils is thought to be due to the transport by termites of fme materials to the surface for mound and surface sheeting construction. Recent studies using micromorphological techniques have also concluded that the relic features of many tropical soils are a result of both pronounced leaching over extended periods of time, and continuous disturbance and homogenization, principally through termite activity [92,96,99]. Examination of microaggregate structure in such soils has revealed termite derived aggregates and lends further support for this hypothesis [23,92,99,100].…”

Section: Soil Translocationmentioning

confidence: 87%

Termites and Soil Properties

Holt

Lepage²

2000

Termites: Evolution, Sociality, Symbioses, Ecology

239

168

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Abstract:This chapter reviews the advances made in our knowledge of the effects of termites on the physical, chemical and biological properties of soils. Emphasis has been placed on more recent contributions, particularly those that explore new concepts in the ecology of termites and soils. There are sections dealing with the effects of termite activity on soil profile development, soil physical properties, soil chemical properties, soil microbiology and plant growth. The physical effects of termites on soils range from micromorphological to soil profile evolution and structure. Recent evidence points to the substantial positive influence of termites on soil hydraulic conductivity and infiltration rates. Their influence on organic matter decomposition and nutrient recycling rates are well recognized and in some landscapes termite mounds act as foci for nutrient redistribution. New information on the microbiology of termite mounds suggests that most are sites of diverse bacterial and fungal activity. Furthermore, the association between mound-building termites and the microbial population present in the structures has a synergistic effect on organic matter decomposition and hence nutrient cycling and availability. Examination of the effects of termite activity on plant production generally indicates a positive influence.

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“…Microaggregates are near spherical ranging from 80 to 300 μm in size usually. They correspond to the 'pseudosand', 'micropeds', 'granules' described earlier by Kubiena (1950), Brewer (1964) and Trapnell and Webster (1986), respectively. Thus, Ferralsols porosity is closely related to the arrangement of microaggregates and the packing of clay particles within the microaggregates with a contribution of large pores resulting from biological activity.…”

Section: Introductionmentioning

confidence: 99%

Change in the hydraulic properties of a Brazilian clay Ferralsol on clearing for pasture

Balbino¹,

Bruand²,

Cousin³

et al. 2004

Geoderma

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Ferralsols under native vegetation have a weak to moderate macrostructure and a welldeveloped microstructure corresponding to subrounded microaggregates that are usually 80 to 300 μm in size. The aim of this study was to analyze how the hydraulic properties of a clay Ferralsol were affected by a change of structure when the native vegetation is cleared for pasture. We studied the macrostructure in the field and microstructure in scanning electron microscopy. The water retention properties were determined by using pressure cell equipment. We determined the saturated hydraulic conductivity, K s , by applying a constant hydraulic head to saturated core samples, and the unsaturated hydraulic conductivity, K(Ψ), by applying the evaporation method to undisturbed core samples. Results showed a significant decrease in the water retained at −1 and −10 hPa from 0-to 40-cm-depth when the native vegetation is cleared for pasture. That decrease in the water retained was related to a smaller development of microaggregation and greater proportion of microaggregates in close packing. For smaller water potential, there was no difference of water retained at every depth between native vegetation and pasture. Pedotransfer functions established earlier for Brazilian Ferralsols and using clay content as single predictor gave pretty good results but the precision of the estimation decreased when the water potential increased. This decrease in the precision was related to the lack of predictor taking structure into account. K s and K(Ψ) showed an upward trend with depth under native vegetation and pasture. Except at 0-7-cm depth between the Brachiaria clumps in the pasture where smaller K s and K(Ψ) than at the other depth was recorded whatever land use, we did not record any significant difference of K s and K(Ψ) at every depth between native vegetation and pasture. The upward trend shown by the hydraulic conductivity with depth was related to the increase in the development of microaggregation with depth.

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Microaggregates in red earths and related soils in East and Central Africa, their classification and occurrence

Cited by 33 publications

References 6 publications

Origin of microaggregates in soils with ferralic horizons

Origin of microaggregates in soils with ferralic horizons

Termites and Soil Properties

Change in the hydraulic properties of a Brazilian clay Ferralsol on clearing for pasture

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