CLAY MINERALS IN SOILS DERIVED FROM LOWER OLD RED SANDSTONE TILL: EFFECTS OF INHERITANCE AND PEDOGENESIS

The clay mineralogy of thirty-two profiles located mainly in the Vale of Strathmore and developed on glacial till derived from Lower Red Sandstone sediments and lavas has been investigated by X-ray diffraction. The soils were selected so that the parent material was related predominantly to one of the rock types common in the Lower Old Red Sandstone succession—namely, marl, sandstone, lava, or conglomerate. Comparison of the < 1.4μm fractions separated from fresh rock samples with those separated from the C horizons of the soils clearly established the dominant influence of parent rock on the soil-clay mineralogy. The clay minerals inherited by the soil often include unusual trioctahedral expansible minerals such as saponite, interstratified vermiculite-chlorite, and smectite-vermiculite, as well as more common types like mica, montmorillonite, and chlorite. Kaolinite is also found but it is not certain that it is only of inherited origin. Weathering of the clays during soil formation brings about complete degradation of the expansible trioctahedral minerals, a process usually well advanced in the B or even at the top of the C horizon, and vermiculitization of mica. The latter process occurs mainly in the A horizon, with concomitant precipitation of interlayer aquohydroxy-aluminium ions thereby forming a vermiculite-chlorite intergrade. Chlorite and kaolinite appear to be little affected by weathering. The weathering transformations are most pronounced in freely drained acid soils (pH < s) and are at a minimum in poorly drained soils and where the pH remains above 6. The susceptibility to weathering of the trioctahedral expansible minerals results in relatively high values for exchangeable magnesium at the base of the profile.     

Potassium release on drying of soil samples from a variety of weathering regimes and c clay mineralogy in China

Thirty two soil samples from China were analyzed for exchangeable K before and after drying. Most soil samples were higher in exchangeable K after air-drying and ovendrying (60°C) than when wet. Soil clay minerals, especially clay-size mica, affected K released in air-dry and oven-dry samples. According to composition of clay minerals of air-dried samples, five classes were recognized. Soil samples with high mica and montmorillonite have the highest exchangeable K. Samples that contained higher kaolinite than mica had lower exchangeable K. Samples with higher kaolinite than quartz and mica had still lower exchangeable K. Samples of sandy soils contained very low exchangeable K. When quartz was the main mineral, the samples that had kaolinite and gibbsite as the main clay minerals had very low exchangeable K. The degree of weathering (weathering mean) bore an inverse relationship to the amount of K released on drying in air or at 60°C. Udults and Udalfs (Red Earths) of southeastern China, because of their high K release on being dried, are inferred to have received fine mica from the Western Desert dust rainout, reported to Liu et al. (1981).     

Origin of extractable titanium and vanadium in the a horizons of scottish podzols

The A horizons of Scottish podzols often contain unusually high amounts of EDTA-extractable Ti and V. Five such soils developed on different parent materials were studied, total and EDTA-extractable Ti, V and Fe being determined in the samples and their particle size fractions. The fine sand accounts for 50–80% of the total and extractable amounts of all three elements in the total soil although, in general, both the total and extractable Ti and V concentrations increase with decreasing particle size. Thus the clays contain up to 420 ppm Ti and 27 ppm V extractable with EDTA. The main Ti minerals in the samples are anatase, rutile and ilmenite. Observations by scanning electron microscopy of the surfaces of the minerals show clear evidence of chemical, and possibly physical weathering, processes that may lead to the accumulation of Ti in fine fractions, but not to downward translocation. Vanadium is probably associated with iron oxides and ferromagnesian minerals, from which it is released by weathering and subsequently adsorbed by the clay fraction. Electron paramagnetic resonance spectra confirm that most of the V extracted from the samples and their clay fractions is in the vanadyl, (VO)²⁺, form.     

Mineralogy of two red soil (Alfisol) profiles of mysore state,India

Quantitative mineralogical composition of the clay fractions of two red soil (Alfisol) profiles developed on gneissic rocks in Mysore, India, is discussed in relation to the genesis of these soils. Data on the mineralogy of their silt and sand fractions are also presented. Both the silt and clay fractions are kaolinitic and contain considerable amorphous material. A possible weathering sequence of transformation of the minerals, with probable mechanisms involved, is suggested.     

Mineralogic evolution in hydromorphic sandy soils and podzols in “landes du médoc”, France

Soils of the nearly level “Landes du Médoc” in southwestern France have a pattern of alternating bodies of hydromorphic podzols (Haplaquods) and low humic hydromorphic soils (Psammaquents). The soils are formed in a sedimentary mantle of coarse, quartzose sands with a slight microrelief consisting of low, elongated ridges and shallow, intervening troughs. The water table is at shallow depths throughout the plain, even at the surface in places. The podzols on the crests of the low ridges have distinct A₂ and cemented B₂ h horizons. Podzols persist down the sides of ridges but going downslope first lose the A₂ horizon and then the cementation of the Bh horizon. Soils in the shallow troughs have A₁ and Cg horizons without B horizons.The fine silt (2–20 μm) and clay (0–2 μm) fractions of the parent sand contain primary trioctahedral chlorite, mica, feldspars, and quartz, with the last mineral predominant. During soil development, the first three minerals undergo weathering at different rates and to different extents. Chlorite is most strongly weathered, followed in order by plagioclases and K-minerals. In the fine silt fraction, weathering seems to occur mostly by fragmentation of particles. In the clay fraction, the phyllosilicates successively form irregularly interstratified minerals with contractible but not expandable vermiculitic layers, interstratified minerals with contractible and expandable smectitic layers, and finally smectites.The extent to which the silicate minerals are weathered becomes progressively greater from the low humic hydromorphic soils to the podzols with friable Bh horizons to the podzols with cemented Bh horizons. Smectite is present only in the A₂ horizons of these last podzols.The aluminum release by weathering of silicate minerals is translocated in part in the form of organo-metal complexes into the Bh horizons of the podzols. Greatest concentrations of Al are associated with coatings of monomorphic organic matter on mineral grains in the cemented Bh horizons, in which some Al has also crystallized into gibbsite. That mineral was not detected in friable B horizons of podzols nor in the low humic hydromorphic soil. Contrary to expectations, the mobile Al did not enter interlayer spaces of expanding 2:1 clay minerals.     

Andosol to Luvisol evolution in Central Mexico: timing, mechanisms and environmental setting

Surface and buried Andosols and buried Luvisols of the Nevado de Toluca Late Quaternary tephra-paleosol sequence (Central Mexico) were studied to show whether these soils present an evolutionary sequence and to determine the pedogenic mechanisms and environmental factors involved in the evolutionary process. Micromorphological observations and mineralogical composition of fine sand and clay fractions were used to detect type and succession of soil-forming process. Some of the buried Andosols, defined as “intergrade” Andosols, have a predominantly blocky structure, humus-depleted areas, redoximorphic features and thin clay coatings in Ah horizons. Clay fractions of buried Andosols contain halloysite besides amorphous components, whereas in modern Andosols, allophane is dominant. Luvisols have micro-areas with granular structure and abundant phytoliths in the groundmass of Bt horizons assumed to be the relict Andosol features. Luvisol clay fractions are dominated by halloysite and kaolinite. Primary minerals show micromorphological weathering features in all studied soils being stronger in Luvisols; however, even in Luvisols, sand fractions consist mostly of unstable volcanic silicates. We hypothesise that the studied profiles form an evolutionary sequence: Andosols–“intergrade” Andosols–Luvisols; the soil transformation is supposed to be linked to progressive crystallisation of 1:1 clay minerals. Comparing the Nevado de Toluca paleosol properties with the existing data on volcanic soil climo- and chronesequences and assessing the regional paleopedological and lacustrine records of Quaternary paleoclimates, we concluded that wet/dry climatic oscillations took place during the formation of the studied paleosols. Rapid crystallisation of 1:1 minerals occurred during dry phases, which speeded up the Andosol to Luvisol transformation and made it independent from the primary mineral weathering status. The Andosol to Luvisol transformation accelerated by climatic fluctuations is thought to be a common soil evolutionary pathway in the subtropical and tropical regions of recent volcanism, which suffered contrasting precipitation oscillations in the Quaternary.     

Mineralogical study of weathering products of granodiorite at Shinshiro City (IV)

In the preceeding paper(1), the weathering sequences of each primary mineral were established in the weathering profile of granodoritie mainly by X-ray diffraction analysis of the weathered mineral grains coarser than 0.2 mm. Since the silt and clay fractions were assumed to have been produced by disintegration or decomposition of the primary minerals as seen in the former papers (2, 3), there should be genetical interrelation between the mineralogical compositions of the silt and clay fractions and the onen of the weathered grains of the primary minerals.     

Soil adsorption complex of the meadow-chestnut soils at the Dzhanybek research station in the northern Caspian region

Data on the composition and properties of soil adsorption complex in the virgin and ameliorated meadow-chestnut soils in the northern Caspian region are generalized. It is shown that the experimental values of the effective CEC in the A1 horizon are lower than those calculated on the basis of data on the organic matter content and the content and mineral composition of fine fractions. We explain this discrepancy by the interactions between the organic matter and clay minerals resulting in the blocking of a part of the exchangeable positions. In the BC horizon, the experimental values of the effective CEC are twice as high as those calculated from the data on the amount of labile clay minerals in fine fractions. This can be explained by the presence of sorption centers on poorly crystallized illites and chlorites in the clay fraction and by the partial aggregation of clay material into coarser fractions that cannot be destroyed upon the separation of clay fractions by the Aidinyan procedure, which leads to the underestimation of the clay content.     

CLAY AND SILT MINERALOGY OF SOME SOILS FROM QASIM, SAUDI ARABIA

Qasim, some 500 km north-west of Riyadh, is one of the agriculturally important areas of Saudi Arabia. Silt fractions of the soils of the Wadi ar Rimah and side wadis, classified as Torrifluvents, are characterized by high quartz contents and the universal occurrence of kaolinite and felspar, generally with plagioclase predominant; mica, chlorite and hornblende also generally occur. The clay fractions contain mainly palygorskite and a smectite-mica interstratification with smaller amounts of kaolinite, traces of quartz and occasionally chlorite. Palygorskite generally increases in content with depth. Variations in mineralogy probably reflect changes in depositional conditions rather than pedogenic processes; possible reasons for the high palygorskite content are discussed. Sedentary soils (Torriorthents) reflect the mineralogy of the rock from which they were derived. In clay fractions from salt-marsh soils (Salorthids) calcite reacts strongly with smectite-mica during DTA.     

POTASSIUM RESERVES IN A 'HARWELL' SERIES SOIL

A sample of Harwell soil containing 36 percent fine clay (< 0.3 μm) and 14 per cent coarse clay plus fine silt (0.3–5μm) was separated into fractions, and the K-supplying power of soil and fractions measured by cropping with ryegrass, exchange with Ca resin and double-label isotopic exchange with ⁴²K and ⁴⁵Ca ions. Mineralogical examination of the fractions coupled with the cropping experiments showed that the K-supplying power of the soil to ryegrass can be explained by the presence of a zeolite, clinoptilolite-heulandite, in addition to the clay minerals, mica, and interstratified illitic smectite, commonly found in a glauconitic clay-rich soil. The 0.3–5 μm fraction, containing much zeolite, has an exchange diffusion coefficient for K ions to Ca resin of 1.8 × 10^?16 cm²sec^?1 compared with a value of 5.7 × 10^?20 for the < 0.3μm fractions in which interstratified illitic smectite is the dominant mineral. Isotopic exchange shows that all Ca ions in fractions < 50μm are isotopically exchangeable. In fractions coarser than 20μm, some of the K ions in felspar and mica were not exchangeable within the duration of the experiments.     

The Role of Soil Mineralogical Characteristics in Sustainable Soil Fertility Management: A Case Study of Some Tropical Alfisols in Nigeria

The pedogenic horizons of nine profile pits dug across three toposequences were studied to determine the soil mineralogical characteristics and its implications on sustainable management of the fertility of some tropical Alfisols in Nigeria. Results showed that the epipedon which were predominantly ochric had textures that ranged from sand to sandy loam, while the subsurface (B/Bt) horizons had sandy clay loam to sandy clay texture and were gravelly (31.79–83.04%). The soil reaction ranged from strongly acid to neutral (pH 5.10 to 7.05). Calcium and magnesium dominated the exchange sites and accounted for about 75% of the exchangeable bases. Illite/mica and kaolinite were the dominant minerals in the clay fractions, while quartz, mica, and feldspars dominated the fine sand and silt fractions of the soils. While the presence of illite and mica could be important for potassium nutrition in these soils, kaolinite and oxides of iron could also cause phosphorus fixation.     

Bildung schlechtkristalliner bis amorpher Verwitterungsprodukte in stark bis extrem versauerten Waldböden

Formation of poorly crystallized weathering products in strongly to extremely acid forest soils Poorly crystallized weathering products, formed as a consequence of wide-spread extrem acidification and silicate weathering in forest soils, were examined using X-ray diffraction (XRD) and fluorescence (XRF), scanning electron microscopy (SEM, EDXRA) and chemical analyses. The investigations were carried out on five extremely acid forest soils (different Luvisols, a Gleyic Luvisol and a Luvic Podzol) derived from different parent materials (loess, sand loess, glacial sands/loam) in Northrhine Westfalia and Schleswig-Holstein. The results reveal an intense destruction of clay minerals and other silicates in the extremely acid topsoils leading to an accumulation of poorly crystallized to amorphous compounds. These weathering products occur predominantly as silicic coatings on the surface of soil aggregates or as small spherical precipitates on mineral surfaces. Besides Si they contain small amounts of Al and Fe.     

Red soil chemistry and mineralogy reflect uniform weathering environments in fluvial sediments, Taiwan

Purpose

Information on the physicochemical properties, mineral species and micromorphology of lateritic soils and gravel soil layers in paleo-environmental soil profile is severely lacking. Red soil profile of the Taoyuan terrace was employed to demonstrate its different extents of lateritic weathering. The objectives of this study were to compare the physicochemical properties of lateritic soils and gravel soil layers and identify using conventional and synchrotron X-ray diffraction (XRD) analyses mineral species in nanoparticles separated by automated ultrafiltration device (AUD) apparatus.

Materials and methods

Soil samples were collected from paleo-environmental lateritic soils. Soil samples were examined using elemental analysis, conventional and synchrotron XRD analyses, high gradient magnetic separation, separation and collection of nanoparticles by AUD apparatus, and transmission electron microscopy (TEM).

Results and discussion

The soil pH, redness index, quantities of free Al- and Fe-oxides (Al_d and Fe_d), and clay content of lateritic soils are higher than those of gravel soil layers. Illite, kaolinite, gibbsite, quartz, goethite, and hematite were identified in clay fractions and nanoparticles by conventional and synchrotron XRD analyses. TEM images show presence of hematite nanoparticles on the surface coating of kaolinite nanoparticles and aggregated hematite nanoparticles overlapping the edge of a kaolinite flake in a size range of 4?C7?nm. Synchrotron XRD techniques are more straightforward and powerful than conventional XRD with random powder methods for identifying nanoparticles in red soils, particularly for illite, kaolinite, goethite, and hematite nanoparticles. According to chemical compositions of clay fractions and red soil features in the Taoyuan terrace, these red soils can be taken as lateritic red earths or red earths.

Conclusions

This work suggests that physicochemical properties, mineral species, and micromorphology of red soil at all depths can shed light on the extent of paleo-environmental lateritic weathering.     

ABSTRACT of the Articles Printed in Journal of the Science of Soil and Manure,Japan

A contrasting occurrence of clay minerals was found within a soil profile which was derived from volcanic materials in the suburbs of Fukuoka-city, Northern Kyushu. The soil profile is located on an isolated terrace, and the morphological characteristics of the soil correspond exactly to Andosols, so-called Kuroboku soils or Humic Allophane soils.

The clay fraction of upper horizons of the soil consists largely of alumina-rich gel-like materials, gibbsite, and layer silicates such as chlorite and chloritevermiculite intergrades, while that of lower horizons is composed of allophane and gibbsite or halloysite. There was no positive indication of allophane in the upper horizons. Corresponding with the clay mineralogical composition, quartz is abundant in the fine sand fraction of the upper horizons, while the mineral is very scarce or none in the lower horizons, suggesting a close relation between the petrological nature of parent volcanic materials and the mineralogical composition of weathering products. The dominant clay mineral in the volcanic 1.10il might be dependent on the petrological nature of parent materials, and allophane is mostly formed from andesitic materials, and alumina-rich gel-like materials and layer silicates have come from quartz andesitic materials. Allophane would transform to gibbsite or halloysite according to weathering conditions, and aluminarich gel-like materials change to gibbsite under a well-drained condition.

The soil materials have been so greatly weathered that some horizons contain gibbsite of even more than 40 per cent or halloysite over 70 per cent. The morphology and mineralogy are quite similar to so-cailed “non-volcanic Kuroboku soils.”     

Clay mineralogy differs qualitatively in aggregate‐size classes: clay‐mineral‐based evidence for aggregate hierarchy in temperate soils

Clay minerals have a major role in soil aggregation because of their large specific surface area and surface charges, which stimulate interactions with other mineral particles and organic matter. Soils usually contain a mixture of clay minerals with contrasting surface properties. Although these differences should result in different abilities of clay minerals regarding aggregate formation and stabilization, the role of different clay minerals in aggregation has been seldom evaluated. In this study, we took advantage of the intrinsic mineral heterogeneity of a temperate Luvisol to compare the role of clay minerals in aggregation. First, grassland and tilled soil samples were separated in water into aggregate‐size classes based on the aggregate hierarchy model. Then, clay mineralogy and organic C in the aggregate‐size classes were analysed. Interstratified minerals containing swelling phases accumulated in aggregated fractions compared with free clay fractions under the two land‐uses. The accumulation increased with decreasing aggregate size from large macroaggregates (> 500 µm) to microaggregates (50–250 µm). Carbon content and carbon‐to‐nitrogen ratio followed the opposite trend. This fully supports the aggregate hierarchy model, which postulates an increasing importance of mineral reactivity in smaller aggregates than in larger aggregates in which the cohesion relies mostly on physical enmeshment by fungal hyphae or small roots. Consequently, differences in the proportion of the different 2:1 clay minerals in soils can influence their structure development. Further research on the links between clay mineralogy and aggregation can improve our understanding of mechanisms of soil resistance to erosion and organic matter stabilization.     

Genesis of a Xeralf on feldspathic sandstone, South Australia

A Xeralf on feldspathic sandstone was sampled from a hillslope in the Mount Lofty Ranges in order to study its genesis and, in particular, the origin of the strong texture contrast. Micromorphological study demonstrated that the clay present in void argillans and papules in the B2 horizon accounted for only a small amount of the clay present. Elemental analysis of the whole soil (< 2 mm) and sand, silt and clay fractions showed that there had been considerable weathering of both quartz and microcline, which were the dominant minerals present. Kaolinite is the dominant clay mineral weathering product. Illite appears to be forming from vermiculite in the A horizon. Using zircon as an internal standard, it was shown that elemental losses of SiO₂ and reductions in weight and volume were similar in A and B horizons. Losses of aluminium and potassium were greatest in the A horizon, least in the B3. There has been an absolute increase in the amount of iron. A possible source is iron from heavy mineral bands upslope. It was concluded from the similarity of the quartz particle-size distributions of the A2, B2 and B3 horizons that the intensity of weathering of quartz was the same in A and B horizons. In the case of feldspar (mostly microcline), there is a greater proportion of feldspar in the fine sand and silt fractions of the A2 horizon than in the B horizon. Weathering of feldspar is greatest in the A horizon. The texture profile is principally a function of greater lateral loss of clay from the A horizons compared to the B horizons.     

Sand mineralogy and related properties of some soils in South‐Western Nigeria

Abstract

Five representative soil profiles were excavated along a toposequence selected in the Itagunmodi area of South‐Western Nigeria. The soils were subjected to physical, chemical, and mineralogical analyses. The results indicated soils with high fine sand and clay contents, but low silt content. The soils were found to vary from slightly acid to strongly acid (pHH₂O = 4.0 to 6.2). Organic C, available P, and Kjeldahl N contents decreased with increasing depth. Cation exchange capacity (CEC) ranged from 3.11 to 28.75 cmol(+)/kg soil. Base saturation was low (<51%). From a total elemental analysis, Si was found to be the dominant element, followed by Al, and then Fe. Extractable P, and exchangeable K, Mg, and Ca were quite low. The dominant minerals in the fine sand fraction were quartz, feldspar, zircon, hornblende, tourmaline, and opaque ores. The variation in the zircon/tourmaline (two resistant minerals) ratios with depth suggests a stratification of the parent material. The change in the quartz/feldspar ratios was an indication that the degree of weathering in the soil profile is not uniform.     

Clay mineralogy of some volcanic ash soils in which cristobalite predominates

The clay mineralogical composition of soils on volcanic ashes from Mashū and Kamuinupuri-dake volcanoes, Hokkaido, which are rich in cristobalite, was determined using petrological, X-ray diffraction, differential thermal, and selective dissolution and differential infrared spectroscopic methods.

The cristobalite occurred in abundance in every size of fraction from coarse sand to clay and every soli from approximately 1,700 to 8,400 years old, and was concluded to be of igneous origin. The major clay minerals were allophanelike constituents and allophane with some layer silicates as the minor clay mineral, being similar to those of andesitic ash soils and different from those of volcanic ash soils containing abundant quartz. The quartz of volcanic ashes was presumed to bederived from the groundmass-equivalent portion of the ashes which had been formed from magma at a low temperature.     

Exploitation of potassium by various crop species from primary minerals in soils rich in micas

We investigated the question of whether exchangeable K⁺ is a reliable factor for K⁺ availability to plants on representative arable soils (Aridisols) rich in K⁺-bearing minerals. Five soils with different textures were collected from different locations in Pakistan and used for pot experiments. The soils were separated into sand, silt, and clay fractions and quartz sand was added to each fraction to bring it to 1 kg per kg whole soil, i.e., for each fraction the quartz sand replaced the weight of the two excluded fractions. On these soil fraction-quartz mixtures wheat, elephant grass, maize, and barley were cultivated in a rotational sequence. Growth on the sand mixture was very poor and except for the elephant grass all species showed severe K⁺-deficiency symptoms. Growth on the mixture with silt and clay fractions was much better than on the sand fraction; there was no major difference in growth and K⁺ supply to plants whether grown on silt or clay, although the clay fraction was rich and the silt fraction poor in exchangeable K⁺. On both these fractions the plant-available K⁺ supply was suboptimal and the plants showed deficiency symptoms except for the elephant grass. This plant species had a relatively low growth rate but it grew similarly on sand, silt, and clay and did not show any K⁺ deficiency symptoms, with the K⁺ concentration in the plant tops indicating a sufficient K⁺ supply regardless of which soil fraction the plants were grown in. The reason for this finding is not yet understood and needs further investigation. It is concluded that on soils rich in mica, exchangeable K⁺ alone is a poor indicator of K⁺ availability to plants and that mica concentrations in the silt and clay fraction are of greater importance in supplying crops with K⁺ than exchangeable K⁺.     

Natural strontium isotope composition as a tracer of weathering patterns and of exchangeable calcium sources in acid leached soils developed on loess of central Belgium

The natural Sr isotope composition of acid leached soils developed on loess, under beech forest, in central Belgium was used as a tracer of soil forming processes, in conjunction with physico‐chemical and quantitative mineralogical investigations. Attention was focused on weathering and exchange processes, with special emphasis on the origin of the current soil exchangeable fraction and the influence of the atmospheric deposition and biological cycling on the calcium exchangeable pool (Sr acts as a proxy for Ca). The determination of ⁸⁷Sr/⁸⁶Sr ratios was made on the bulk soil, on the clay‐ and silt‐size soil separates, on 0.1 m HCl extracts, on the labile pool, on the soil solution and on the bulk precipitation. The acid leached soil profiles are characterized by a sequence of weathering processes that is highlighted by both mineralogical and isotopic changes. From the calcareous unweathered loess (pH 7.5) to the uppermost soil horizons (pH < 4.0) the evolution of the ⁸⁷Sr/⁸⁶Sr isotope ratio clearly reflects: (i) the selective weathering of Ca‐plagioclase (small ⁸⁷Sr/⁸⁶Sr ratio) and the increasing proportion of resistant K‐ and Rb‐rich minerals (large ⁸⁷Sr/⁸⁶Sr ratio) in the uppermost soil horizons; and (ii) a downward translocation of clay minerals with a large isotopic ratio, a physical breakdown of muscovite and a non‐congruent chemical weathering of K‐feldspar. The influence of organic restitutions or atmospheric deposition is not significant. The comparison between the Sr isotopic signature of the soil solution, and the exchangeable and HCl‐extractible soil fractions provides information about cation exchange efficiency, soil–water interaction and the origin of the exchangeable pool.