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In southwest Rwanda, upland forest soils developed on quartzites and micaceous sandstones along steep slopes have sometimes the macromorphological look of true Podzols. An investigation of the micromorphological, mineralogical and chemical properties, however, reveals only weak indications of illuviation of amorphous organic complexes. This process of cheluviation seems to be secondary relative...
Management of soil organic matter (SOM) is esential to sustaining the quality and productivity of soils around the globe. This appears to be particularly true in the tropics where there is a greater proportion of nutrient poor, highly weathered soils that are more susceptible to losses of SOM. Developing management practices that promote the maintenance and storage of SOM in the tropics depends on...
Sand, silt and clay fractions were analysed to characterise different soil-forming processes of two acid forest soils from the Strengbach catchment. On the northern slope, a podzolic soil was formed on only slightly hydrothermally altered Brezouard granite and on the southern slope was an acid brown soil derived from granite strongly influenced by hydrothermal activity. During hydrothermal alteration,...
The release of base cations by the weathering of soil minerals provides the primary buffer against the detrimental impact of acid deposition on the soil. The rate of release of base cations will be governed by mineral composition and the exposed surface area of mineral grains. In theory it is possible to calculate the surface area of a mixture of grains on the basis of particle size and geometry....
Weathering rates in 12 horizons of soils developed in loess and clay sediments were measured by means of laboratory experiments. The experiments were carried out by percolating thin columns containing approximately 2 g of soil material. Despite the small amount of sample used, the results were fairly reproducible. Weathering rates in loess soils were 0.8 to 8 times higher than rates measured in sandy...
The objective of this study was to relate the major chemical and mineralogical properties of soils formed on sedimentary deposits in southeastern Nigeria to the stability of their aggregates at both the macro and micro (colloidal) levels. Five profiles and twenty-five topsoil samples representing four major geological formations were studied. The soils are classified as Entisols and Ultisols. The...
The chemistry, mineralogy and micromorphology of three soil profiles formed on genetically different Quaternary deposits have been studied in relation to the podzolization process. The soil materials showed quite uniform geochemical composition both within and between the study sites independent of great geographical distance and there is accumulation of sesquioxides in the Bs horizons at all three...
Halloysite-bearing weathered pyroclastic deposits of the Roccamonfina volcanic area (Southern Italy), consisting generally of light grey clay masses richer in slightly weathered pumice grains, mottled patches of whitish clayey material and yellowish-brown veins along vertical root channels, were characterised by chemical analysis, X-ray diffraction (XRD), infrared spectroscopy (FT-IR), optical (OM),...
Sixteen Pallic (Aqualfs, Ustalfs, Aquepts, Ochrepts) and related soils collected from the North and South Islands of New Zealand were studied to determine if variations in nonexchangeable K supply could be explained by mineralogical composition. A strong relationship was found which indicates that mica is weathering to vermiculite. Proportions of vermiculite and kandite are generally higher in the...
Pile and windrow burning of logging slash are important silvicultural practices in sub-boreal forests, yet, little is known about their effects on soil properties. We investigated the physical, chemical, and mineralogical properties of soils collected 2 years after prescribed pile and windrow burning treatments of clearcut forest site in the central interior of British Columbia. We also used scanning...
A 6-year study of the behaviour of heavy metals in Calcaric Fluvisols dedicated to agricultural use was made. The total metal content and the fractions extractable in bicarbonate, nitric acid, DTPA and citrate-dithionite solutions were determined and the mineralogical fractions to which the metals were bound were examined. When the factors that, according to the bibliography, most influence heavy...
The inorganic fractions of 25 samples from 12 representative Brazilian soils were separated into six subfractions (clay, silt, very fine sand, fine sand, medium sand, coarse+very coarse sand) and their effective cation and effective anion exchange capacity (ECEC and EAEC, respectively) evaluated by the compulsive exchange method using unbuffered BaCl 2 solution. The soils had developed from...
Five arsenic affected soil profiles, one each from Ghentugachhi and Gotera village of Chakdah block, Gayeshpur, Kalyani block, Nadia district; Ramnagar village of Baruipur block and Sonarpur mouza of Sonarpur block of South 24 Parganas district of West Bengal, India covering the soils of Typic Haplustepts, Typic Endoaquepts, Vertic Haplustepts and Aquic Haplustepts respectively have been studied for...
Information on soil mineralogy is essential for weathering rate calculations. Quantitative mineralogical analyses are expensive and time-consuming, and thus indirect methods of determining the mineralogical composition are important, for example estimating the composition based on the elemental content in till (total concentrations), or based on information about the underlying bedrock. The mineralogical...
The aim of this study was to characterize carbon sequestration by mineralogical control at the scale of a volcanic soil horizon. We adapted the classical density fractionation procedure and focused on the heavy fractions (>1.9), which we divided into eight organomineral fractions. We characterized them simultaneously through non-destructive mineralogical analyses (XRD and NMR of Al and Si) and...
The issue of sustainable soil K management has partly been ignored during the last decades when the potential environmental impact from agricultural use of nitrogen and phosphorus has been considered a more important problem. It has become evident that mixed systems, especially under organic farming practices, commonly suffer from negative K field balances, which may deplete the soil in exchangeable...
In the tropical moist semi-deciduous forests of West Africa, gravelly soil horizons common on the summits and upper slopes in the landscape, are often covered by a thin layer of gravel-free soil. Previous investigations have shown that these top layers are formed by termites transporting gravel-free soil material from the subsoil to fallen logs and branches on the soil surface. The present study located...
Much of the previous work on potassium (K) fixation by soils and pure minerals has focused on K fixation and release by the clay size fraction. However, in soils containing considerable amounts of silt- and sand-size K-fixing minerals, such as vermiculite and hydrobiotite, K fixation capacity may be substantial in the coarser size fractions. We measured the contribution of clay, silt, very fine sand...
Three Oxisols, developed from serpentinite (Sungai Mas Series), basalt (Kuantan Series) and andesite (Segamat Series), selected to represent the most common Oxisols in Malaysia were sampled and studied. The objectives of this study were: (i) to determine mineralogical composition and factors responsible for changes in point of zero charge (pH 0 ) of the variable charge component of three Oxisols;...
We studied the mineralogy of a perudic Andosol developed on the Dieng Tephra Sequence in central Java, Indonesia. The objective was to confirm the presence and determine the origin and stability of 2:1 and interlayered 2:1 phyllosilicates in well-drained Andosols. This was and still is a debated topic in the literature. Total elemental and selective dissolution, as well as microscopic and X-ray diffraction...
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