The complex genesis of red soils in peninsula de Yucatán,Mexico: Mineralogical,micromorphological and geochemical proxies

The origin of red clayey soils developed on limestones has been largely questioned. We have analyzed thick red soils on Eocene-Pliocene limestones of the Yucatán peninsula (with detail in the Kantunil Kin area). The morphological, geochemical and mineralogical characteristics were interpreted as a record of pedogenesis and geomorphic dynamics during the Quaternary. Sand fraction mineralogy, the Zr/Ti ratio and ternary diagrams of Trace elements (Ti-Y-Zr, La-Th-Sc and Zr-Th-Sc) indicated a mixed origin of the soil parent material; volcanic and granitic/metamorphic components, redeposited by eolian transport. Within the soil matrix, primary minerals were transformed by weathering and caused desilication with the accumulation of kaolinitic clay. Reworked pedofeatures were originated from different soil bodies eroded. In the lower part of the profiles, we described the zone of carbonate leaching front, were the clay translocation in suspensions and posterior coagulation is more probable than the migration of elements in solutions and posterior synthesis.     

Micromorphology and petrography of Late Weichselian glaciolacustrine varves in southeastern Sweden

The purpose of this investigation is to describe and interpret the sedimentology and petrography of Late Weichselian varves in southeastern Sweden in order to determine their nature and origin. It is focused on the microscopic evidence for glaciolacustrine varve sedimentation in the Baltic Ice Lake and the possibilities of making a detailed facies classification of the sediments in an area with an established varve chronology. The material examined was cores taken from five representative localities in an area below the highest shoreline of the Baltic Ice Lake in the provinces of Skåne and Blekinge, i.e., below an altitude of 55–65 m. The investigations included chemical analyses, XRD, microscopy (polarized) and SEM-EDX investigations of the summer and winter layers of the varves. The results of the chemical, clay mineralogy (XRD) and microscopic examinations of the bedrock and mineral fragments indicate that the material in the different facies of the varved clay is mainly produced by moderate alteration and erosion from the local bedrock of predominantly granitoid rocks and of residual kaoline deposits. It is possible to distinguish microscopic evidence of four varve types differing in texture depending on the water depth and how close to the ice the different facies were deposited, i.e., if they were deposited proximally, distally or extramarginally in relation to the ice margin. It is also possible to relate these differences to changes in the palaeoclimate during the deglaciation of the area in the Bölling and Older Dryas chronozones.     

An approach to rheometry in soil mechanics—Structural changes in bentonite, clayey and silty soils

Rheology is regarded as the science of flow behaviour, where, based on isothermic equations, the deformation of fluids and plastic bodies subjected to external stresses may be described. Hooke's law of elasticity, Newton's law for ideal fluids (viscosity), Mohr-Coulomb's equation, and finally, Bingham's yielding are well known relationships and parameters in the field of rheology.

Rheometry is a well established measurement technique to determine the specific rheological properties of fluid and plastic bodies. However, the application of this technique in soil mechanical investigations is yet relatively uncommon. In order to explain point contact processes and strength an extrapolation of such findings to data of triaxial, direct shear or oedometer tests is still missing. Thus, this paper aims to introduce rheometry as a suitable method to determine the mechanical behaviour of soils and mineral suspensions when subjected to external stresses. To do this a Na-bentonite, Ibeco Seal-80 (IS-80) has been used as a testing material, and the suspensions were equilibrated with NaCl solutions in different concentrations in order to determine the ionic strength effects on interparticle strength and changes in mechanical properties. Furthermore a vertisol, a clayey oxisol, both from Brazil, and loess material from Israel, saturated with NaCl in several concentrations were analysed.

A parallel-plate-rheometer MCR 300 (Modular Compact Rheometer, Paar Physica, Ostfildern, Germany) has been used to conduct oscillatory tests. From the stress–strain relationship parameters and specific characteristics as thixotropy, storage modulus G′ and loss modulus G″, viscosity η, yield stress τ_y and the linear viscoelastic deformation (LVE) range including a limiting value γ_L were determined and calculated, respectively. With aspect to salt effects, amplitude sweep tests on CaCO₃ rich Avdat loess show an increasing stability due to higher NaCl concentrations. In a comparative test of Avdat loess and Ibeco Seal-80, turbulent versus sliding shear behaviour could be illustrated. To demonstrate clay mineralogy effects or textural effects clay rich substrates from Brazil, a smectitic vertisol and a kaolinitic oxisol were compared, showing a higher level of stored elasticity (stability) in case of smectites and a lower value in regard to kaolinites. These preliminary results of amplitude sweep tests show that rheometry is a potential method of investigating microstructural characteristics of mineral suspensions and of clayey or silty soils.     

An extended nitrogen,phosphorus, and potassium model for tall fescue

Abstract

Dry matter yields and plant nutrient uptake of forage grasses are influenced by levels of applied nitrogen (N), phosphorus (P), and potassium (K). Response to one element generally depends on levels of the other two. In this article, a mathematical model is presented which includes the major elements, N, P, and K as inputs. It consists of triple logistic equations with a total of thirteen parameters. The model is evaluated for Kentucky 31 (KY 31) and Kenwell tall fescue (Festuca arundinacea Schreb.) grown at Watkinsville, GA on Cecil sandy loam (clayey, kaolinitic, thermic, Typic Hapludult). Procedures are described for parameter estimation. The model provides high correlation between yields and plant uptake of N, P, and K with applied N, P, and K for both cultivars of tall fescue, as demonstrated in response graphs and scatter diagrams. Intercept and N response coefficients from this study agree closely with those from previous work. Data from this study support the hyperbolic relationship between dry matter yield and plant N uptake predicted by the model. The model is mathematically well‐behaved and is relatively easy to use in practice.     

Physical properties of tsunami-affected soils in Aceh, Indonesia: 2½ years after the tsunami

On 26 December 2004, a tsunami caused extensive loss of life, damaged property and degraded agricultural land in the province of Aceh, Indonesia. While some of the associated soil chemical changes have been documented, information on soil physical properties is sparse. The objective of this study was to quantify physical properties of some tsunami-affected upland agricultural soils in Aceh, Indonesia. Soil was sampled approximately 21/2 years after the tsunami, from the 0–0.1 m, 0.1–0.3 m and 0.3–0.5 m depths in four sites in the villages of Kling Cot Aroun in Aceh Besar sub-district, Kuta Kruen in Aceh Utara sub-district, Udjong Blang Mesjid in Bireuen sub-district and Meue in Pidie Jaya sub-district on the east coast of Aceh. These sites were located within 1 km from the sea at elevations ranging from 0 to 5 m ASL. The soils were Ultisols except for Meue, which was an Entisol. Soil properties measured were bulk density, structural stability and particle size distribution. Soil water retention, pore-size distribution and saturated hydraulic conductivity were estimated by inserting the values of bulk density, clay, sand and silt contents into pedotransfer functions from the literature. The analyses conducted during this study did not permit us to ascertain what proportion of the soil particles were of tsunami-origin. Nonetheless, deposition of finer-textured material may have occurred in two of the sites. In comparison with the greyish-white, coarse textured soil in the rest of the profile, a finer-textured yellow horizon was present in the lower slopes of the Udjong Blang Mesjid site. At Meue, clay and silt contents were higher in the surface 0.3 m than in the 0.3–0.5 m depth, although a distinct horizon was absent. Particle size distribution in all sites was dominated by the sand fraction, although clay and silt contents were relatively high (20–30 g 100 g^− 1) at Kuta Kruen. Among the sand fractions, fine sand (0.02–0.25 mm) was highest at Kling Cot Aroun, Kuta Kruen and in the “yellow horizon” at Udjong Blang Mesjid, making them more prone to hardsetting and compaction after intensive tillage. Soil compaction was present in all sites with that in the “yellow horizon” at Udjong Blang Mesjid being highest. The relatively low porosity in this layer may be beneficial, as it is likely to reduce the high rates of water drainage and nutrient leaching in this sandy soil. The more compacted soils were characterised by higher numbers of micropores (r, pore radius < 4.3 μm), lower water retention at saturation, smaller numbers of macropores (r > 14.3 μm), lower hydraulic conductivity and intensive gleying, indicating frequent waterlogging. The soils in all depths from Kling Cot Aroun and the “yellow horizon” at Udjong Blang Mesjid were very dispersive, that at Meue moderately dispersive in the 0.3–0.5 m depth but stable in the 0–0.1 m depth, and at Kuta Kruen very stable in all depths. Soil physical degradation was a feature of the soils examined, and its amelioration will be the key to improving and sustaining crop yields in these soils. Possible management interventions include organic amendments such as compost or manure, and minimum tillage options such permanent beds or zero tillage with retention of crop residues as in situ mulch together with suitable cover crops.     

Micromorphology of a “welded” Sangamonian to Wisconsinan age paleosol in southwestern Wisconsin

Micromorphological characteristics indicate that in southwestern Wisconsin pedogenesis transgressed the Sangamonian-Wisconsinan chronostratigraphic boundary in conjunction with colluvial and eolian sedimentation. The use of micromorphology helps to distinguish between pedological, colluvial, and eolian components in the paleosol horizon sequence, which can be difficult to resolve and interpret solely from field investigations and from other laboratory analyses. Results show that a basal loess “mixed zone” within the welded paleosol profile contains features that are the products of colluvial reworking processes. We present micromorphology data which support stratigraphic relationships suggesting that colluvial processes were important in the formation of basal loess “mixed zones” in addition to other possible mixing processes such as pedoturbation and bioturbation.     

Long‐term effects of lime and gypsum additions on no‐till corn and soybean yield and soil chemical properties in southern Brazil

A long‐term experiment on a clayey, kaolinitic, thermic Rhodic Hapludox where dolomitic lime was applied to the surface (either at 4.5 t/ha or at 1.5 t/ha per yr for 3 yr), or incorporated into the topsoil (4.5 t/ha), and gypsum applied to the surface (3, 6, and 9 t/ha), was carried out to evaluate their effects on soil profile chemical properties and yields of corn (Zea mays L.) and soybean (Glycine max L. Merrill). Lime applied to the soil surface at either full or split rates, or incorporated and surface‐applied gypsum had long‐lasting effects on soil acidity or calcium and sulphur availability respectively, as measured 8 yr after application. Grain yields of corn and soybean were not influenced by liming. Gypsum at 9 t/ha significantly increased corn grain yields by 7 and 8% respectively 7–10 yr after application, but did not affect soybean grain yields. The differences in response of the corn and soybean crops to gypsum might be related to the Ca²⁺ uptake by plants because of cation exchange properties of roots, being smaller for corn than for soybean. The use of gypsum in no‐till systems becomes more viable when corn is grown with a greater frequency in crop rotation.     

Soluble salts dynamics in the soil under different climatic conditions

The dynamics of soluble salts concentration in the soil was investigated at seven research stations in Israel that represent four climatic regions: Mediterranean, semi-arid, mildly arid and arid. Measurements were taken in different seasons from soils that were developed on hillslopes, which are consisted of hard calcareous rocks. The relationship between the soluble salts content and rainfall was found to be non-linear. An abiotic threshold, which is characterized by a sharp change in the soluble salts content, exists around 200 mm isohyet: sites that receive less than 200 mm rainfall are characterized by significantly high soluble salts content whereas sites that receive more than 200 mm are characterized by very low soluble salts content. Each side of this abiotic threshold expresses typical behavior that can be defined as “environmental signature”. At the “dry” side of the threshold temporal heterogeneity, rate of change, potential of change and differences between layers are higher than those at the “wet” side of the threshold.     

Relationship between soil geochemistry and grape composition in Tuscany (Italy)

The concentrations of 13 trace elements were determined in soils and Sangiovese grapes collected in vineyard zones of Tuscany (Italy). The purpose was to establish a correspondence among the chemical composition of grape, the geochemistry of vineyard soil and the geolithological features of cultivation zone, and determine the provenance of the grapes by means of their chemical fingerprints. Statistical analysis of Ba, Rb and Sr concentrations distinguished three classes of grapes according to the geochemical and geopedological characteristics of the soils. Grapes with the highest Sr levels grew on high‐Sr soils derived from calcareous, calcareous‐marly and marly‐clayey rocks, whereas the most elevated Rb concentrations characterized the berries cultivated on soils formed from clayey‐marly and sandy‐marly lithologies. Grapes with the highest Ba concentrations grew on soil derived from arenaceous rocks and carbonate lithologies of evaporitic origin. These findings suggested that Ba, Rb and Sr could be used as fingerprints for the chemical traceability of Sangiovese grapes.     

武都晚更新世泥石流堆积体的沉积相

本文以沉积学的方法,对武都晚更新世泥石流堆积体的地层剖面进行了划分对比,并建立了该期泥石流堆积体的综合地质柱状图,并较详细地研究了它们的沉积相特征。认为武都本期泥石流堆积体,是由与泥石流作用有关的泥流型洪积相、水流型洪积相以及与泥石流作用无关的冲积沉积相和黄土状土沉积相所组成。由此推断了它们的形成环境,探讨了泥石流发生、停歇与新构造作用及气候的关系,从而进一步划分了本次泥石流作用期的4次作用阶段。     

Soil formation and weathering on ultramafic rocks in the mountainous tundra of the Rai-Iz massif,Polar Urals

Gravelly clay loamy and clayey soils developed from the derivatives of ultramafic rocks of the dunite-harzburgite complex of the Rai-Iz massif in the Polar Urals have been studied. They are represented by raw-humus pelozems (weakly developed clayey soils) under conditions of perfect drainage on steep slopes and by the gleyzems (Gleysols) with vivid gley color patterns in the eluvial positions on leveled elements of the relief. The magnesium released from the silicates with the high content of this element (mainly from olivine) specifies the neutral-alkaline reaction in these soils. Cryoturbation, the accumulation of raw humus, the impregnation of the soil mass with humic substances, gleyzation, and the ferrugination of the gleyed horizons are also clearly pronounced in the studied soils. Despite the high pH values, the destruction of supergene smectites in the upper horizons and ferrugination (the accumulation of iron hydroxides) in the microfissures dissecting the grains of olivine, pyroxene, and serpentine, and in decomposing plant tissues take place. The development of these processes may be related to the local acidification (neutralization) of the soil medium under the impact of biota and carbonic acids. The specificity of gleyzation in the soils developing from ultramafic rocks is shown in the absence of iron depletion from the fine earth material against the background of the greenish blue gley color pattern.     

ANDESITE WEATHERING

Petrographic and quantitative mineralogical analyses of two andesites and their saprolite (weathered rock) from the Cascade Range in California reveal a mineral weathering sequence in the rocks related to crystal size and composition and to weathering environment. Both the hypersthene andesite and the olivine andesite studied have been subjected to moderate to intensive leaching by acid solutions percolating through the superjacent soil bodies. Although the two parent rocks differ in chemical and mineralogical composition, their weathering to saprolite has followed a similar progression. During early stages of weathering of both rocks, relatively large hypersthene phenocrysts are most resistant. Following in decreasing order of resistance in both cases are plagioclase phenocrysts and finegrained mafic minerals, olivine, and glassy matrix material. Quartz is relatively stable in the earliest weathering stages, but it decreases rapidly with increased weathering. Free iron oxides and clay increase with increased weathering. Amorphous clay dominates the early weathering stages, but as weathering progresses, kaolin increases relative to amorphous clay.     

Biochemical analysis of soil organic matter and microbial biomass composition—a pilot study

Biochemical composition of both intracellular (biomass) and extracellular soil organic matter was determined after extraction with 0.5 M K₂SO₄. Extractable carbon, hexoses, pentoses, total reducing sugars, ninhydrin-reactive nitrogen (NRN), proteins and DNA content were colorimetrically determined. The objective of the pilot study was to examine the information potential included in newly measured biochemical characteristics, their environmental variance and the relationships with main soil properties. Correlation analysis and PCA showed independence between biochemical parameters and physico-chemical properties of the soil. Thus, the parameters characterising biochemical composition of the soil biomass and extracellular matter seem to bring new information about the soils beyond the physico-chemical parameters. They also seem to reveal a more detailed view on microbial biomass or extracellular organic matter pool than C_bio or C_ext alone, respectively. The variance, which occurred in biochemical characteristics, also displayed a high discrimination potential between the defined soil categories. Three types of indices were newly proposed: index I (“substrate quantity index”)—the biomass-specific amount of the extracellular organic compounds, index II (“immobilisation ratio”)—the portion of the organic compound immobilised in microbial biomass, and index III (“substrate quality index”)—the extracellular organic compound content related to extracellular organic carbon. The indices displayed a higher potential than both soil biotic and abiotic parameters to discriminate soil characters and soil types.     

Improved prediction of water-retention properties of clayey soils by pedological stratification

The water-retention properties of clayey soils have been studied at ?0.3 × 10⁵ and ?15 × 10⁵ Pa matric potentials using three sets of clayey horizons differing in their pedological origin. Measurements were made on small clods collected in winter when swelling is at a maximum. The results are discussed in relation to variations in the clay content and clay fabric. The bulk volume, which appears to be closely related to both clay content and clay fabric, allows the variations in water retained to be explained better than with clay content alone. With clayey horizons originating from a single soil family, differences in water retained can be explained by variations in clay content alone because clay fabric does not change greatly. These results demonstrate the significance of pedological stratification in estimating the water-retention properties when a single soil characteristic, such as clay content, is used.     

The effects on corn and on a rhodic paleudult soil of 17 annual Cu and Zn sulfate additions

A long-term field experiment was established in 1967 and continued through 1983 to evaluate the response of corn (Zea mays L.) and the loading capacity of a Davidson clay loam soil (clayey, kaolinitic, thermic Rhodic Paleudult) to yearly additions of Cu and Zn sulfates. By 1983, the 17 annual additions of Cu and Zn resulted in cumulative totals up to 280 kg Cu and 560 kg Zn ha^?1. These Cu and Zn additions, either alone or together, did not cause any grain or stalk yield decreases. The DTPA extractant separated most of the soil treatment levels for both Cu and Zn. The sevenfold increase in DTPA extractable Cu and eighteenfold increase in DTPA extractable Zn followed linear relationships to treatment levels. Copper concentrations in the blades and grain were not related to soil additions of Cu or Zn. However, Zn concentrations in blades and grain were directly related to each other, to soil Zn treatment levels and to DTPA Zn. Increasing blade Zn concentrations were accompanied by decreasing blade Mn concentrations.     

Review of Ecological Engineering Solutions for Rural Non-Point Source Water Pollution Control in Hubei Province,China

Anthropogenic contamination by heavy metals in fluvial systems is mostly bound to fine-grained clay minerals and organic substances, which accumulate by vertical accretion in sediment traps along river courses (oxbow lakes, dams and floodplains). These environmental settings are considered as good archives of historical changes in contamination. Much less attention, however, is paid to deposits of river channels, which act as sourcing transport paths for these archives and/or build archives of their own. In order to provide a better insight into the spatio-temporal distribution of pollutants in channel deposits, we investigated contamination levels of Cu, Pb and Zn in a series of sediment cores along the River Morava, a left-hand tributary of the Danube River, Czech Republic. In particular, the relationships between metal concentrations, sediment lithology (facies), grain size, magnetic susceptibility and mineralogy and chemistry of fly-ash particles were investigated. Element chemistry and lithology of channel deposits were compared with those of the nearby floodplain deposits in the same catchment. Four river-channel facies were defined, ranging from sandy gravels to clayey silts, and confronted with the floodplain sediments. Al/Si ratios were found to be useful proxies of grain size, and Al was utilized as an excellent normalizing element for heavy metals, which filters out much of the grain size effects on contamination. The floodplain deposits are significantly less contaminated than their river-channel counterparts. Heavy-metal contamination of river bed sediments (expressed as enrichment factors, EFs) is not simply bound to fine-grained particles, and much of the contamination was found in coarse-grained, sandy facies. Elevated EFs of Zn, Cu and Pb in several sediment layers, which show high magnetic susceptibility (MS), high values of MS normalized to Fe and a high proportion of magnetic fly-ash spherules and their chemistry suggest that significant part of the heavy-metal contamination can be carried by magnetic fly-ash spherules. A part of this contamination is bound to coarse-grained fluvial facies, indicating that the magnetic spherules can be transported as bed load sediments. Magnetic pollution and heavy-metal pollution can therefore coincide in river bed deposits. It is suggested that most of this contamination can be related to local point sources of pollutants (fly-ash deposit spills).     

Impact of biochars on swell–shrinkage behavior,mechanical strength,and surface cracking of clayey soil

Swell–shrinkage, cracking and stickiness of expansive clayey soils usually lead to their low yield. Improvement of these poor soil physical properties is a key goal for enhancing the crop productivity of expansive clayey soils. This article presents results of a study on the impact of three biochars produced from wheat straw (SB), woodchips (WCB), and wastewater sludge (WSB) on the swell–shrinkage behavior, mechanical strength, and surface cracking of a clayey soil. The soil was treated with biochars at the rate of 0, 20, 40, and 60 g biochar kg^?1 soil, respectively; and incubated for 180 d in glasshouse. Application of biochars decreased significantly (p < 0.01) the coefficient of linear extensibility (COLE) of the soil, the effect of SB being most prominent. The tensile strength (TS) of the clayey soil was originally 937 kPa, which decreased to 458 kPa, 495 kPa and 659 kPa for 6% SB‐, WCB‐, and WSB‐amended soils, respectively. Shear strength tests indicated that biochars significantly reduced cohesion (c) and increased internal friction angle (θ). Biochar significantly reduced the formation of soil surface cracks, surface area, and length of the cracks. The surface area density of cracks in the 6% biochar‐amended soils decreased by 14% for SB, 17% for WCB, and 19% for WSB, respectively, compared with control. The results suggest that biochar can be used as a soil amendment for improving the poor physical properties of the clayey soil, particularly in terms of reduction in swell–shrinkage, tensile strength and surface area density of cracking.     

Global analysis of the protection status of the world’s forests

This study presents a global analysis of forest cover and forest protection. An updated Global Forest Map (using MODIS2005) provided a current assessment of forest cover within 20 natural forest types. This map was overlaid onto WWF realms and ecoregions to gain additional biogeographic information on forest distribution. Using the 2008 World Database on Protected Areas, percentage forest cover protection was calculated globally, within forest types, realms and ecoregions, and within selected areas of global conservation importance. At the 10% tree cover threshold, global forest cover was 39 million km². Of this, 7.7% fell within protected areas under IUCN management categories I–IV. With the inclusion of IUCN categories V and VI, the level of global forest protection increased to 13.5%. Percentage forest protection (IUCN I–IV) varied greatly between realms from 5.5% (Palearctic) to 13.4% (Australasia), and for forest types from 3.2% (temperate freshwater swamp forest) to 28% (temperate broadleaf evergreen forest). Median protection of forest cover in 670 ecoregions (forest above a specified threshold) was 5.9% (IUCN I–IV); at IUCN I–VI, 46% of the ecoregions had less than 10% forest protection. Considering their biodiversity importance, forest protection within global priority areas was insufficient, e.g., median protection of 8.4% in biodiversity hotspots (IUCN I–IV). Results have policy relevance in terms of the target of the Convention on Biological Diversity (CBD), reconfirmed in 2008, to effectively conserve “at least 10% of each of the world’s forest types”. Regular updates of these analyses would allow progress towards achieving that target to be monitored.     

The influence of gleyzation and sulfate reduction in different rocks on the lysimetric water from them: A model experiment

The model experiments showed that, under the influence of gleyzation and sulfate reduction, deep changes occurred both in the solid and liquid phases of the soil-forming rocks (soils). The results of an experiment with three widespread soil-forming rocks—river clayey alluvium, loess-like clayey alluvium, and lacustrine calcareous loamy-clayey alluvium—demonstrated that, under the stagnant-percolative water regime and periodic gleyzation, the liquid phase was drastically acidified (by 2–4 pH units) and the redox potential of the lysimetric water was significantly lowered. A significant increase in the input of iron (by 80 to 100 times compared to the control), calcium (10 times), and silicon (1.5–2.0 times) to the lysimetric waters was observed. The sulfate reduction retarded the removal of iron from the substrates to the lysimetric runoff.     

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.