bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mineralogy of Soils Developed on Alluvium in the Indo‐Gangetic Plain (India)
Authors: Sidhu P. S. , Gilkes R. J. 
Published: July 2010

AbstractX‐ray diffraction, electron microscopic, and petrographic techniques have been employed to study the mineralogy of four soils developed on the Indo‐Gangetic alluvium in northwestern India. Sand and silt fractions are dominated by primary quartz. Other minerals present in these fractions include muscovite, plagioclase and alkali feldspars, amphibole, biotite, and chlorite. Illite, chlorite, and kaolinite have been identified in the clay fraction of each soil with smectite being present in one soil. Both muscovite and illite belong to the dioctahedral 2M1 polymorph, whereas chlorite is trioctahedral. Quartz and feldspar grains appear to be unaltered and very angular. Although the studied soils show morphological and physico‐chemical evidence of pedogenesis, mineral alteration has been minimal. The mineralogy of all the soils is very similar and no changes in the mineralogical make‐up with depth in a particular pedon have been observed. Soil mineralogy can be related to the mineralogy of rocks in the source areas which contributed sediments. It is considered that insignificant post depositional weathering of sediments has occurred.
Estimation of the Spatial Variability of the Soil‐Water Flux
Authors: Rao P. S. C. , Rao P. V. , Davidson J. M. 
Published: July 2010

AbstractA simple method for estimating the spatial variability of the soil‐water flux from known variability of soil microhydrologic properties is presented. The method is based on the theory of approximating a differentiable function using Taylor‐series expansion (TS‐method). Published data for means and variances of the soil microhydrologic properties were used to estimate the mean and variance of the soil‐water flux in a draining profile of Panoche soil. These values were compared with those estimated using a Monte Carlo simulation procedure (MC‐method) on the same set of data. Relative advantages and disadvantages of these two methods are briefly discussed.
The Lithoplinthic Horizon, a Diagnostic Horizon for Soil Taxonomy
Authors: Smith Guy D. , A. Pedro Brito , Luque Oswaldo 
Published: July 2010

AbstractA new diagnostic horizon, the lithoplinthic horizon, is proposed for an indurated ironstone that contains many irregular, tubular, channels filled with fine earth, that conduct water and permit plant roots to reach underlying horizons. It is hard rock for many engineering interpretations and soil for interpretations for plant growth. It is proposed that, if there are no overlying diagnostic horizons other than an ochric epipedon, the soils should be classified as lithoplinthic subgroups of Orthents. Use of family classes of particle size and depth is proposed, but not of mineralogy.
The Mechanism of Sulfate Adsorption on Iron Oxides
Authors: Parfitt Roger L. , Smart Roger St. C. 
Published: July 2010

AbstractAdsorption isotherms were determined for sulfate adsorption on iron oxides under acid conditions. The product of the surface reaction between the iron oxides and sulfate ions was examined by infrared spectroscopy which showed four bands in the v S‐O stretching region. Thus a structural model could be obtained for the reaction. Two surface hydroxyl groups (or OH2+ ions) are replaced by one sulfate ion, and two oxygen atoms of the sulfate ion are coordinated each to a different Fe3+ ion, resulting in the binuclear bridging surface complex Fe‐O‐S(O2)‐O‐Fe. The complex is formed on the surfaces of goethite (α‐FeOOH), akaganéite (β‐FeOOH), lepidocrocite (γ‐FeOOH), hematite (α‐Fe2O3) and amorphous ferric hydroxide.
A Study of a Deep Weathering Profile on Granite in Peninsular Malaysia: III. Alteration of Feldspars
Authors: Eswaran H. , Bin Wong Chaw 
Published: July 2010

AbstractFeldspar grains or their pseudomorphs from the different weathering zones are studied with the SEM. Weathering commences with dissolution to form voids in the grains. Close to the rock, the first product is allophanic material present as globules adhering to the voids in the grains. In the δ zone the product is halloysite with some amorphous silica spherules. The surface of the pseudomorph has a hummocky appearance suggesting an amorphous intermediary phase prior to halloysite formation. Kaolinite formation commences in the γp zone and gibbsite in the γm zone. Admixtures of kaolinite and halloysite may be found on the same pseudomorph, but admixture of gibbsite with another secondary mineral is not encountered.Biotite follows a similar trend of alteration. It is concluded that irrespective of the primary weatherable mineral, the type of secondary mineral found is a function of the microenvironment.
Interaction of Monomeric Silicic Acid With Copper and Zinc and Chemical Changes of the Precipitates With Aging
Authors: Leggett G. E. 
Published: July 2010

AbstractPrecipitates were formed by titrating dilute, acidic solutions of monomeric silicic acid [Si(OH)4] and copper (Cu) or zinc (Zn) to various pH values. Those containing Cu formed above pH 6.0; those containing Zn formed above pH 7.0. Periodically, during 2 years of aging in their mother liquor, the liquid phase was sampled and analyzed and the Cu/Si or Zn/Si molar ratios of the precipitates calculated. The Cu/Si ratios of those containing Cu stabilized readily near 0.78 and were unaffected by pH. The Zn/Si ratios of the Zn‐containing precipitates, however, changed as a result of Si enrichment from near 1.80 soon after their formation to near 0.80 after aging 2 years. The systems with the lowest pH changed first and most rapidly and became stabilized within 6 months; those above pH 8.0 changed more slowly.The Zn‐containing precipitates gave diffuse X‐ray diffraction patterns indicative of a 2:1 layer silicate, whereas those containing Cu were amorphous.
Scanning Electron Microscopy of Rhizobium spp. Adhering to Fine Silt Particles
Authors: Fehrmann R. C. , Weaver R. W. 
Published: July 2010

AbstractBacterial polysaccharides binding to soil particles were observed with the scanning electron microscope. The bacteria were grown in shake culture with dispersed silt particles (2–5 µm) to promote polysaccharide‐soil particle interactions. Species of Rhizobium were used because of their abundant polysaccharide production. The mucilagenous polysaccharides exhibited connective networks that joined particles to one another and also to bacteria. Aggregates of particles were seen only when bacterial polysaccharides were present. These micrographs provide visual evidence of the binding action of bacterial polysaccharides to soil particles.
Approximate Analytical Solution for Solute Flow During Infiltration and Redistribution
Authors: De Smedt F. , Wierenga P. J. 
Published: July 2010

AbstractAn approximate analytical solution is developed to describe solute flow in soil during infiltration and redistribution. For the solution it is assumed that hydrodynamic dispersion is linearly related to the pore water velocity. In order to use the solution it is necessary to estimate the solute penetration depth. Methods of estimating the solute penetration depth are discussed. Solute concentration distributions computed with the approximate analytical solution are compared with those obtained with a numerical model. It is shown that the solution proposed is most useful during the infiltration phase. During the redistribution phase the approximate analytical solution provides a first‐order estimate of the solute distribution with time and depth. Computed chloride distributions compare favorably with chloride concentrations observed by Warrick et al. (1971).
Root Growth in Cores Formed from Fragipan and B2 Horizons of Hobson Soil
Authors: Blanchar R. W. , Edmonds C. R. , Bradford J. M. 
Published: July 2010

AbstractThe effect of changes in acidity and bulk density of cores formed from B2 and fragipan horizons of a Hobson soil on probe penetration and pea root growth were evaluated. Increasing soil pH in the range of 4.2–6.5 had no measurable effect on probe resistance, but resulted in greater root length in both B2 and fragipan samples. Probe penetration resistance increased as bulk density was increased. The silty clay loam B2 horizon was more resistant to probe penetration than the sandy loam fragipan when compared at the same bulk density and moisture tension. Root length was more closely related to probe penetration resistance than to bulk density. Root growth in both B2 and fragipan soil decreased as probe resistance increased from 10 to 20 bars and essentially stopped in soil where probe penetration resistance exceeded 20 bars.
Spatial Variation of Sand Content and pH Within Single Contiguous Delineations of Two Soil Mapping Units
Authors: Campbell James B. 
Published: July 2010

AbstractQuantitative estimates were made of the rates of spatial variation of soil properties within each of two sampled areas displaying contrasting patterns of variation. Samples were collected at 10‐m intervals on two sampling grids, each 8 by 20, positioned on contiguous delineations of the Ladysmith and Pawnee series in eastern Kansas. The Pawnee is developed from glacial till, the Ladysmith from fine‐textured sediments.Spatial variation of sand and pH measurements within both of the sampled areas was studied using the semivariance, a statistical function tailored for the analysis of continuous geographic variables. There is a contrast in spatial variation of sand content within the two areas; in the Ladysmith area, a distance of 30 m is sufficient to encounter full variation of sand content, but in the Pawnee area, a distance of 40 m is required. pH has random variation within both areas. This information can be used to select optimum spacing of samples in designing soil sampling plans.
Effect of Mulching on Sediment in Runoff From Simulated Rainfall
Authors: Singer Michael J. , Blackard John 
Published: July 2010

AbstractSimulated rainfall was used to test the relationship between sediment in runoff and percent of the soil that was mulch covered. Oak leaves (Quercus Douglasii H. & A.), redwood litter (Sequoia sempervirens (D. Don) Endl.) and oat straw (Avena barbata Brot.) were used as mulches on a 0.37m2 plot of Auburn (loamy, mixed, thermic, Ruptic‐Lithic Xerochrepts) surface soil at a 9% slope. Cover percentage was related to sediment in surface runoff by a parabolic relationship. The relationship between redwood and oak covers and sediment in runoff was not significantly different, but both were significantly different from oat straw. Cover shape or distribution of inter‐cover space appears to be important in affecting sediment loss. Runoff volume was significantly reduced by high cover levels which protected the soil from sealing and helped maintain a high infiltration rate.
Solubility Product of Belle Fourche and Colony Montmorillonites in Acid Aqueous Solutions
Authors: Kittrick J. A. 
Published: July 2010

AbstractPublished solubility studies for Belle Fourche and Colony montmorillonites were re‐examined to help answer the question as to whether or not montmorillonite can come to equilibrium with acid aqueous solutions. Values of pH‐⅓pAl3+ for both montmorillonites were plotted against pH4SiO4 after adjusting to common values of pH‐½pMg2+ and pH. Three lines of reasoning indicate that selected Belle Fourche montmorillonite samples came to equilibrium with acid aqueous solutions during a 3‐to‐4‐year study period. First, the slope of the solubility line for Belle Fourche montmorillonite was in agreement with that predicted for equilibrium with a solid phase of the same Al/Sl ratio as Belle Fourche montmorillonite. Second, the stability of the solubility line in relation to the stability of other minerals agreed with known natural relationships, and third, the precision of the pK values is well within experimental error. Similarly adjusted pH‐⅓pAl3+ values for Colony montmorillonite have a wide scatter when plotted against pH4SiO4. This scatter indicates that collectively these samples had not come to equilibrium with any solid phase during a study period of approximately 1 year or less. By examining comparable data for gibbsite (previously unpublished) it is shown that variation in the apparent pK values for Colony montmorillonite may be a consequence of pH variation as the system approaches equilibrium. It is argued that statistical relationships between nonequilibrium components for noncongruent dissolution do not permit conclusions with regard to equilibrium relationships for either Colony montmorillonite in particular, or solid phases in general.
Copper and Cadmium Adsorption Characteristics of Selected Acid and Calcareous Soils
Authors: Cavallaro N. , McBride M. B. 
Published: July 2010

AbstractSamples of two New York soils, an acid and a neutral silt loam, were equilibrated with Cu2+ and Cd2+ solutions in concentrations ranging from 10−5 to 10−4M in distilled water and in 0.01M CaCl2. The extent of complexation and adsorption of the heavy metals was measured using specific ion electrodes and atomic absorption. The data were found to fit the Langmuir adsorption model, and the Cu2+ adsorption maxima were greater than those of Cd2+ for both soils. Acid soils demonstrated much less ability to retain the heavy metals than neutral soils. In the presence of 0.01M CaCl2, adsorption of the metals was much reduced, suggesting Ca2+ competition for adsorption sites. A considerable amount of Cu2+ was complexed in the soil solutions, but Cd2+ complexation was much less evident. The results support an ion exchange mechanism of adsorption in the surface soils, and suggest that precipitation occurs in calcareous subsoils.
A Chemical and Spectroscopic Characterization of some Synthetic Analogues of Humic Acids
Authors: Mathur S. P. , Schnitzer M. 
Published: July 2010

AbstractFourteen analogues of humic acids (“HA's”) were synthesized from phenols, quinones, and salicylic acid by methods described in the literature. Elemental and functional group measurements, and infrared and electron spin resonance spectroscopy, indicated that seven of these “HA's” were in general similar to natural HA's. These “HA's” were methylated and further investigated by chemical degradation. Identities and quantities of the methylated degradation products resembled those from natural HA's treated in the same way. Thus, “HA's” resulting from oxidative polymerizations of salicylic acid, catechol, hydroquinone, and pyrogallol, under a variety of reaction conditions, appear to be suitable for investigations of interactions of humic materials with pesticides, enzymes and other N‐compounds. Some of these synthetic “HA's” can be readily prepared in any laboratory and, in contrast to microbially‐synthesized “HA's”, also as N‐free analogues.
Analytical Properties of the Soluble, Metal‐complexing Fractions in Sludge‐soil Mixtures: III. Unaltered Anionic Surfactants in Fulvic Acid
Authors: Holtzclaw Kenneth M. , Sposito Garrison 
Published: July 2010

AbstractA rapid analytical procedure was developed for the quantitative determination of unbiodegraded anionic surfactants in the fulvic acid fraction of sewage sludge. This procedure, which is a modification of the methyl green method of Moore and K olbeson, consists of: (i) hydrolysis in 4N HCl, (ii) separation on an anion exchange resin, (iii) extraction of a methyl green‐surfactant complex into benzene, and (iv) colorimetric determination of the complex. The modified procedure is free of the negative interferences that occurred when the original methyl green method was applied to a sludge‐derived fulvic acid and does not require specialized reagents or expensive instrumentation.An application of the modified procedure to two representative fulvic acids extracted from anaerobically‐digested sewage sludges indicated that about 5% of the dry mass of a sludge‐derived fulvic acid (water‐ and ash‐free basis) may be attributed to unaltered anionic surfactant compounds. This result suggests that a significant aspect of the chemistry of agricultural soils into which sewage sludge has been incorporated will be reactions involving both unaltered and partially biodegraded anionic surfactants.
Tillage Implements − Soil Structure Relationships and Their Effects on Crop Stands
Authors: Hadas A. , Wolf D. , Meirson I. 
Published: July 2010

AbstractUnder rainfed dryland farming, tillage performed on a dry soil prior to the rainy season is the most important practice to improve the soil physical conditions for crop establishment and development. However, questions have seldom been raised as to the degree of clod breakdown required to improve soil physical conditions for seed germination, as well as the cost in energy and number of implements involved.The objectives of the work reported here were to: (i) collect and correlate data concerning energy input with the degree of soil clod breakdown and aggregate size distributions attained by various tillage implements and operation sequences when performed on dry soils; and (ii) to compare crop stands under field conditions on differently tilled plots.Crop stands and fineness of seedbed tilth were not significantly correlated. Yet, finer tilth could only be obtained through an elaborate tillage operation sequence and a tremendous input of energy if performed on air dry soils, whereas tilling the same soil while moist (approximately at wilting point‐moisture content), produced finer tilth at a much lower energy input.
Differential Infrared Spectroscopy in the Study of Parathion‐Bentonite Complexes
Authors: Mingelgrin U. , Yariv S. , Saltzman Sarina 
Published: July 2010

AbstractDifferential infrared spectroscopy was used to investigate parathion degradation in the adsorbed state. This technique enables observations of the 1,380–1,150 cm−1 region, which is usually overlapping with the strong SiO absorption of bentonites. The appearance of the P=O absorption band upon heating clay‐parathion complexes, in conjunction with other tests, confirmed that parathion degradation on bentonites occurs mainly via a rearrangement reaction.
Displacement of Soil Water by Simulated Rainfall
Authors: Quisenberry V. L. , Phillips R. E. 
Published: July 2010

AbstractDisplacement of initial soil water by simulated rainfall was measured in aggregates of Maury silt loam soil in columns in the laboratory and under field conditions using tritiated water and/or Cl‐ as a tracer of added water. Displacement values measured in aggregates were larger (53 to 85%) than those measured under field conditions (7 to 56%). Percent displacement of initial soil water in Calloway silt loam under field conditions were similar to those of Maury, but were larger in Huntington silty clay loam than in Maury. Initial soil water content of Maury soil did not appear to affect percent displacement. Percent displacement in Maury soil increased as the depth of tillage increased.
Electron Probe Microanalysis of Calcite Grains Containing Phosphorus in Soil
Authors: Qureshi R. H. , Jenkins D. A. 
Published: July 2010

AbstractCalcite, comprising both clastic sand‐sized grains and fossil foraminifera inherited from a marine Cretaceous (“Gault”) clay, has been isolated from a haplaquept (“gleyic brown calcareous earth”) in the United Kingdom and shown by wet chemical analysis to contain an average of 0.3% phosphorus. Electron probe microanalysis indicates that this phosphorus is uniformly distributed within the calcite rather than concentrated as discrete calcium phosphates, and it is concluded that it was biogenic/diagenic rather than pedogenic in origin. Such sources constitute 50–80% of the total soil phosphorus and would be relatively available in the upper horizons of the profile.
Transport of a Noncohesive Sandy Mixture in Rainfall and Runoff Experiments
Authors: Walker P. H. , Kinnell P. I. A. , Green Patricia 
Published: July 2010

AbstractRainfall intensities of 45, 100, and 150 mm/hr with systematically varied kinetic energies were applied to a saturated noncohesive, sandy bed 3 m long and set at slopes of 0.5 and 5%. Detailed size analyses of solids discharged showed that the <31‐µm fraction was most readily mobilized and behaved as a suspended load; the 31‐ to 250‐µm fraction was transported slowly, much apparently as saltating bed load; the 0.25‐ to 4‐mm fraction was transported rapidly, grains tending to move as rolling bed load; the >4‐mm fraction behaved as a lag gravel. The sedimentary properties of bed deposits also reflected the differentiation of various size fractions and minerals in the original mixture. The effects of raindrop impacts within the flow were more important in promoting transport of solids than the aerial component of splash. Under conditions where overland flow had developed, transport of solids was related directly to rainfall intensity and variations in rainfall energy that were associated with variations in raindrop impact frequency. Increases in rainfall energy due to increasing raindrop sizes did not result in increases in solids discharged.
Iron Oxide Mineralogy of Well‐drained Ultisols and Oxisols: II. Influence on Color, Surface Area, and Phosphate Retention
Authors: Bigham J. M. , Golden D. C. , Buol S. W. , Weed S. B. , Bowen L. H. 
Published: July 2010

AbstractSubsoil samples from selected North Carolina Ultisols and Brazilian Oxisols were analyzed to determine how the colors of these materials were influenced by the nature and distribution of their constituent iron oxides. The effects of extraneous variables, i.e., other than the iron oxides, were minimized by utilizing pairs of red and yellow soils that were otherwise similar in their physical, morphological, and mineralogical properties.The iron oxides were found to be concentrated in the <0.2‐µm fractions, and the colors of these clays were the same as or similar to those of the parent soils. The spectral properties of the <0.2‐µm clays were primarily influenced by iron mineralogy. Goethite or mixtures of goethite and hematite were identified in all of the clays; however, Mössbauer analyses indicated that the red members of all sample pairs contained larger proportions of hematite than did their yellow counterparts. In addition, as the clays became redder in hue, the ratio of hematite to goethite generally increased. Calculated surface areas for the iron oxides ranged from 60 to 200 m2/g; values from the yellow clays were consistently higher than those obtained from their red counterparts. The yellow clays were also more efficient adsorbers of phosphate.
Phosphorus Supplying Capacities of Previously Heavily Fertilized Soils
Authors: Novais Roberto , Kamprath E. J. 
Published: July 2010

AbstractFour Coastal Plain soils and one Piedmont soil heavily fertilized in the past were intensively cropped in greenhouse pots to determine changes in extractable soil P as measured by North Carolina, Bray I and Olsen extractants. Slopes relating changes in extractable P with P removed by cropping were very similar for the three sandy soils. Changes in extractable P with the North Carolina and Bray I extractants were correlated with P buffer capacity, % clay, and soil surface area. The principal source of P removed by cropping was NH4F‐P in sandy Coastal Plain soils; NH4F‐P and NaOH‐P supplied equal amounts in the clayey Piedmont soil. Sandy Coastal Plain soils which originally contained more than 74 ppm North Carolina extractable P and 71 ppm Bray I extractable P supplied 82 to 108 kg P/ha to nine crops of pearl millet (Pennisetum americanum, cv. Gahi‐1).