bluuebunny/crossref_metadata_2025_split huggingface dataset:
Micromorphological and analytical studies of the fine matrix of an Australian humus iron podzol
Authors: MILNES A. R. , FARMER V. C. 
Published: July 2006

SUMMARYDetailed micromorphological observations and associated electron probe microanalyses are used to examine the proposition that kaolinite and gibbsite in the B horizon of a humus iron podzol could arise by transformation of allophanic deposits. The B horizon of this podzol is highly complex. In the upper B horizon, this complexity is due to alternating episodes of the influx of organic matter and the deposition of allophanic material; evidence for the separate deposition of allophane and organic matter is presented. Material within the B horizon that has gibbsiporphyric fabric appears to have arisen by crystallization of gibbsite from aluminium‐rich gels deposited before the main influx of allophanic material; there is no convincing evidence that allophanic material has transformed to kaolinite or gibbsite.
Effect of timing of simulated rainfall on ammonia volatilization from urea, applied to soil of varyingmoisture content
Authors: BLACK A. S. , SHERLOCK R. R. , SMITH N. P. 
Published: July 2006

SUMMARYAmmonia volatilization from granular urea applied at 10gNm−2 to pasture was investigated using an enclosure method. Misting 0, 4 or 16 mm of water on to the soil at field capacity within 3 h of urea application resulted in total NH3 losses of 2.81, 0.92 and 0.18 g N m−2 respectively. Further delaying the watering reduced this effect until at 48 h, volatilization was lowered from 3.33 to only 3.09gNm−2 with 16mm of water. Hydrolysis and NH3 loss were rapid. Similar trends occurred at a lower initial soil moisture content.On air‐dry soil (0.06 g H2O/g soil), hydrolysis was slow (73 ± 14% of the urea remained after 30 days) and volatilization, while gradual, accounted for 33% of applied urea‐N after 30 days. Addition of 16 mm of water 48 and 96 h after urea application was followed by a period of rapid hydrolysis and volatilization, resulting in a total loss of 2.59 and 2.40gNm−2 respectively. Repeated addition of 2mm of water produced bursts of hydrolysis and NH3 loss until completion of hydrolysis when additional water had no effect. A total loss after 30 days of 3.94 g N m−2 occurred in this 2 mm treatment.
Size and charge characteristics of kaolinitic soils in SE Queensland
Authors: KOPPI A. J. , SKJEMSTAD J. O. , PAGE D. W. , COCKAYNE D. J. H. 
Published: July 2006

SUMMARYSome kaolinitic soils derived from basaltic material contain 2:1 minerals as a discrete phase and/or interstratified with kaolin as determined by X‐ray diffraction (XRD) and by chemical analysis of DCB‐treated clays, while others show little or no evidence of 2:1 minerals. Mineral impurities were not detected by electron diffraction in the latter group. There is good agreement between the interpretation of XRD traces and the SiO2/Al2O3 ratio given by chemical analysis. Some kaolin is seen by electron microscopy to be of very small particle size, and two distinct morphological types have been recognized. High surface area measurements are consistent with fine particular size. These profiles contain kaolin with higher than normal CEC and permanent negative charges which cannot be accounted for by the presence of 2:1 clay minerals alone and which are attributed to a degree of isomorphous substitution. This substitution and/or mineral impurities may have limited kaolin crystal growth during neoformation.
Ion chromatographic determination of nitrate in 2 M KC1 soil extracts
Authors: STEWART B. M. 
Published: July 2006

SUMMARYA method for the analysis of NO3‐N in a 2 m KCL soil extract, using ion chromatography, is discussed. It involves the treatment of the KCl extract with Ag+‐activated cation exchange resin to remove excess Cl–, followed by analysis using a Dionex ion chromatograph. The results of NO3‐N in soil extracts agreed closely with those obtained by steam distillation. The method was linear up to 20 mg N dm–3 with a detection limit of 0.1 mg Ndm–3. Quantitative recovery of NO3‐N added to soil extracts over the linear range were observed.Standard deviations of samples containing 2.57 and 15.11 mgN dm–3 were found to be 0.06 and 0.11 respectively.
Copper‐induced indefinite aggregation of humic substances: theoretical consequences for copper‐binding behaviour
Authors: TEASDALE R. D. 
Published: July 2006

SUMMARYAn important factor in plant availability of copper is its anomalous binding to soil humic substances, for which aggregation phenomena have been implicated. Two alternative models of copper‐induced humate aggregation are theoretically explored to characterize binding behaviour. In the first model the copper modifies the humic acid so that it self‐associates indefinitely. Copper binding is found to be dramatically enhanced, except at the very low concentrations corresponding to copper‐deficiency. In the second model bivalent copper forms bridges between different humate molecules to yield an array of large cross‐linked complexes. In the latter cross‐linking model, binding of copper is markedly enhanced at low copper concentrations, a behaviour still found when only relatively few sites sterically permit cross‐linking. The cross‐linking model accounts, at least in part, for the low availability and immobility of copper in some problem soils and is consistent with several items of experimental evidence.
Migration of phosphate into aggregated particles of ferrihydrite
Authors: WILLETT I. R. , CHARTRES C. J. , NGUYEN T. T. 
Published: July 2006

SUMMARYThe slow reaction of phosphate with aggregated particles of ferrihydrite, after initial rapid phosphate sorption, was investigated by measuring the changes, with time and temperature, in the amount of phosphate sorbed, and the extractability of the sorbed phosphate. The ferrihydrite was, subsequently, recovered and examined by infra–red spectrometry (IR) and electron probe micro–analysis.Phosphate continued to react with ferrihydrite for at least 90 d at 25°C, but was completely recovered by extraction with 0.1 m NaOH. The IR spectra of sorbed phosphate was insensitive to the temperature and duration of the reaction. Electron probe micro–analysis of the aggregates showed that phosphate migrated to surface sorption sites within the aggregated particles of ferrihydrite.There was no evidence for the formation of surface coatings of ferric phosphate, for changes in the type of bonding, or for penetration of phosphate into the crystal lattice. The slow reaction was attributed to the migration of phosphate to surface sorption sites of decreasing accessibility within aggregates.
The influence of sand‐and silt‐size particles on the cracking during drying of small clay‐dominated aggregates
Authors: TOWNER G. D. 
Published: July 2006

SUMMARYShrinkage through drying is an important natural process contributing to the disintegration of clay aggregates in the field. Sand‐size particles distort the shrinkage of the surrounding clay matrix, causing the latter to shrink anisotropically until cracking ensues.Small artificial aggregates of kaolinite clay and glass beads were observed for cracking during shrinkage under ambient laboratory drying. In tests in which only single‐sized beads were present (1, 2, 3, 4 or 5 mm) the aggregates passed from a state where none cracked to that where all cracked as the concentration of beads was increased, except for 1 mm beads for which no cracking was observed. Furthermore, the concentration corresponding to the onset of cracking increased as the bead size decreased. In tests in which 3 or 5 mm beads were mixed with 1 mm beads, the same trends were observed, but increasing the 1 mm bead fraction tended to inhibit cracking. Some observations on thin clay annuli formed round solid discs complemented the aggregate results.The results provide a framework for a further study on natural soils.
Electrophoretic evidence of the integrity of humic substances separated by means of electrofocusing
Authors: DE NOBILI MARIA 
Published: July 2006

SUMMARYThe alkaline extracts of an andic soil, a Bhir horizon of a spodic soil and leonardite which, after electrofocusing, displayed bands in the neutral region of the pH gradient, were fractionated by electrophoresis in phosphate buffer at pH 6.5. The non‐migrated fraction gave an electrofocusing profile containing only bands focused at pH values above that of the electrophoretic separation. Electrophoresis in sodium acetate buffer pH 4.8 of humic substances extracted from peat permitted isolation of bands focusing above pH4.8. The distribution of metals after electrophoresis suggests that a great part of humic substances which originate bands above pH 6.5 consists of negatively charged Fe and Al complexes. Addition of EDTA to solutions of humic substances extracted from the samples resulted in the disappearance of bands in the neutral region of the pH gradient in the electrofocusing profile of the Bhir sample, while a consistent lessening of these bands was observed in the leonardite and andic soil samples.
Accumulation of pyrite and Fe‐rich carbonate and phosphate minerals in a lowland moor area
Authors: JAKOBSEN B. H. 
Published: July 2006

SUMMARYPyrite and iron‐rich carbonate and phosphate minerals are found in large quantities in an inland moor in western Jutland, Denmark. Sediments with up to 10.4% pyrite (FeS2) occur well‐separated from sediments with iron‐rich carbonate and phosphate minerals both reaching up to ∼6–7%. Analysis of the ground water showed that water enters the moor from different sources. Water of high alkalinity (up to 2.05 meq l−1) as well as water rich in sulphate (up to 79 mg l−1), sulphide (up to 1.75 mg l−1) and Fe2+ (up to 22.4 mg l−1) were sampled from the upper ground water flowing into the moor. On entering the moor processes within moor sediments control authigenic mineralogy, resulting in segregated mineral precipitation.
Changes caused by Norway spruce in an ochreous brown earth, assessed by the isoquartz method
Authors: SOHET K. , HERBAUTS J. , GRUBER W. 
Published: July 2006

SUMMARYPrevious investigations had shown that about 80 years of Norway spruce monoculture on an ochreous brown earth of the Belgian Ardennes were sufficient to accentuate the weak podzolization process already present in the climax beechwood soil and to increase the weathering of several minerals, e.g. 2:2 clay minerals. In order to evaluate more accurately mineral weathering and spruce‐induced losses of nutrient elements, an isoquartz assessment method has been applied to a pair of soil profiles, one developed under beech, the other under spruce.Results show a clear decrease of several weatherable minerals in the soil of the spruce stand which was more marked than in the beechwood, especially for chloritic minerals: losses reach about 30% of the initial chlorite content in the cambic horizon and regularly increase up to 70% in the humic layer. There were severe spruce‐induced losses of Mg and Na: 27% of the initial Mg reserve was removed from the whole soil and the losses reached 60% in the upper 20 cm.It is concluded that 86 years of Norway spruce monoculture have appreciably increased weathering processes and removal of elements.
Aggregation in soils with small amounts of swelling clays. II. Chemistry and surface properties of Na resin stable soil aggregates
Authors: BARTOLI F. , PATERSON E. , PHILIPPY R. , DEMAI J. J. , DOIRISSE M. 
Published: July 2006

SUMMARYStable aggregates of soils with small amounts of swelling clays were characterized after 16 h shaking with Na resin. Different kinds of organic material operate at various levels of micro‐aggregate size, being more aromatic in the coarser aggregates and combined with poorly‐ordered Al and Fe hydrous oxides.Effects on aggregate surface properties are described. For each size of resin stable aggregate, the mesopore volume increased with both increasing aggregating organic materials and poorly‐ordered Al and Fe hydrous oxides.
Source minerals and formation of partially interlayered vermiculites in Dystrochrepts derived from Tertiary sediments
Authors: MATSUE N. , WADA K. 
Published: July 2006

SUMMARYThe formation of partially interlayered vermiculite (PIV) was studied in six Dystrochrepts derived from Tertiary sediments. Mineralogy of silt and clay fractions of gravel and fine earth separated from surface and subsurface samples were determined by X‐ray diffraction. PIV, mica, vermiculite and regularly interstratified 1:1 PIV/chlorite (PIV/Ch(l:l)) were the dominant clay minerals. The contents of these minerals were compared between the specific particle‐size fractions of gravel and fine earth for each sample and the difference was interpreted in terms of mineral transformation associated with soil formation. PIV was formed from mica and PIV/Ch(l:l) in soils with a pH(KCl) of 3.5 to 4.0 and little organic matter. Vermiculite was formed from mica in surface soils with a low pH (pH(KCl) 3.5) and abundant organic matter. PIV would form directly from mica without an intermediary phase of vermiculite and form from PIV/Ch(l:l) by partial dissolution of interlayers in chlorite layers.
Quasi‐thermodynamic basis of competitive‐adsorption coefficients for anionic mixtures in soils
Authors: ROY W. R. , HASSETT J. J. , GRIFFIN R. A. 
Published: July 2006

SUMMARYEquilibrium competitive‐adsorption coefficients derived from the application of the multi‐component Freundlich‐type Sheindorf‐Rebhun‐Sheintuch (SRS) equation appeared to have a soil‐specific, quasi‐thermodynamic basis. Using three soils, single‐solute adsorption isotherms at 288, 298, and 308 K were constructed with arsenate, phosphate, and molybdate. A Clausius‐Clapeyron‐type equation was used to estimate apparent isosteric heats of adsorption values (qiso). The adsorption of the three anions was characterized by different qiso values, and was generally in the order of H2PO4‐>H2AsO4‐>MoO42‐. The magnitudes of the SRS competitive coefficients derived from binary‐solute mixtures were in agreement with the distributions of the heats of adsorption of the individual anion‐soil systems. Higher competitive coefficients, indicating the preferential adsorption of solute i in a binary‐solute mixture containing solutes i and j, tended to associate with higher qiso values for solute i relative to solute j. However, the qiso values for the adsorption of molybdate by one soil underestimated the extent of competitive interactions between arsenate and molybdate.
On predicting the fate of radioactive caesium in soil beneath grassland
Authors: KIRK G. J. D. , STAUNTON S. 
Published: July 2006

SUMMARYA simple mechanistic model is developed for predicting the fate of radioactive caesium in the soil beneath grassland. A continuity equation is derived describing the diffusion, leaching and reaction of caesium in soil, with uptake by a uniformly distributed root system. The soil reaction is characterized by three phases: an instantaneous exchange, a moderately‐fast reversible reaction and a slow reversible reaction. The time‐dependent reactions and root uptake have first‐order kinetics. It is shown that caesium is unlikely to be removed from the root zone by leaching and diffusion, even under prolonged high rainfall. Therefore, since the rates of the soil reactions and root uptake are much greater than the rates of diffusion and leaching, it is not necessary to calculate the concentration profile to find the rate of uptake. The computer program for the model is just 30 lines of fortran, and requires only a few seconds of micro‐computer CPU time for each year of simulation.Some predicted rates of plant uptake and distributions in the soil are given. It is seen that the fate of the caesium is markedly influenced by soil parameters dependent on soil clay content, clay mineralogy, organic matter content, cation saturation and pH, and by the rooting density. The predicted rates of uptake vary from about 0.5% to 50% per annum, which is compatible with data reported elsewhere. The predictions are intended to expose gaps in knowledge of the fate of caesium in soil: in particular, the mobility of sorbed radio‐nuclides on soil surfaces needs further study. Predictions are not given for the fate of caesium in any real situations because insufficient data are available.
Aluminium contamination and other changes of acid soil solution isolated by means of porcelain suction‐cups
Authors: RAULUND‐RASMUSSEN KARSTEN 
Published: July 2006

SUMMARYComparison was made between the chemical composition of soil solutions isolated by means of a suction method using porcelain cups and by centrifugation. The soil solutions were isolated from three depths of field plots, where the soil (Typic Haplohumod) had been subjected to various pretreatments.The cups were made of mullite and corundum as shown by X‐ray diffraction analysis. The material when powdered had a cation exchange capacity of about 10meq kg−1. Solutions with similar ionic strengths were obtained by the two methods, but the cups were found to release substantial amounts of Al and to adsorb H, Ca, K, Na and organic matter.After the cups had been placed in the soil for more than 7 months, calculations suggested that the Al activity in cup solutions was controlled by amorphous gibbsite. This amorphous material was probably produced by proton‐induced decomposition of part of the cup material. It is concluded that such cups are improper for isolation of soil solution from acid soils.
The application of classical physics transport theory to water movement in soil: development and deficiencies
Authors: TOWNER G. D. 
Published: July 2006

SUMMARYThe development of soil‐water transport theory is essentially that of the application of classical physical theories that were originally derived for the perceived analogous transport of fluids, heat and electricity in continua. Much of soil‐water transport theory was developed by Buckingham at the turn of the century, but it took several decades for it to become well understood and established. An inability to solve partial differential equations with water‐dependent transport coefficients hampered a rigorous analysis and a proper interpretation of early experiments. The theory has been well proven in the laboratory, but application to the field has been less than successful because of hetereogeneity and macropores. More recent theories based on other principles have not yet received adequate testing. Future work should extend the established theory as well as develop and test new ones.
Effect of farmyard manure and its humic fractions on the aggregate stability of a sandy–loam soil
Authors: FORTUN A. , FORTUN C. , ORTEGA C. 
Published: July 2006

SUMMARYThe effect of cattle manure and its humic fractions on the aggregate stability of a sandyloam soil has been studied. Cattle manure was extracted with 0.1 m NaOH and the extract was dialysed to obtain a combined fulvic acid + humic acid fraction (FHA). Humic acid (HA) was precipitated from this extract, redissolved in 0.1 m NaOH solution and dialysed. The manure and the organic fractions were added at two rates to a sandy–loam soil and the mixtures incubated for 2 and 17 weeks.Changes in the water‐stable aggregation of the soil were followed. In these tests, the effects on water stability of pre‐wetting with alcohol or benzene were also examined. Addition of manure, by itself, was rather ineffectual, but stability was significantly improved after two weeks of incubation by addition of the organic fractions. FHA was much more effective than HA, particularly in increasing stability after the benzene pretreatment. There were only slight changes in aggregation after 17 weeks as compared with 2 weeks.
Measuring unsaturated sorptivity and hydraulic conductivity using multiple disc permeameters
Authors: SMETTEM K. R. J. , CLOTHIER B. E. 
Published: July 2006

SUMMARYA new field method of obtaining, with minimal disturbance, the unsaturated hydraulic conductivity (K0) and sorptivity (S0) from unconfined disc permeameter measurements is introduced. Conventionally, the sorptivity is obtained from the initial square‐root‐of‐time behaviour of discharge from the disc permeameter. In some cases this can be difficult to measure, in part because multi‐dimensional flows approach quasi‐steady state very rapidly. As an alternative we extend the ponded twin‐ring method to unsaturated discs of several radii. This method has the advantage that only long‐time, quasi‐steady discharges are needed to obtain K0 and S0. In the present study, the two methods are tested using data obtained for a fine sandy loam at a supply potential (Ψ0) of – 35 mm and agreement is good.
Frost action in clay soils. II. Ice and water location and suction of unfrozen water in clays below 0°C
Authors: BROWN S. C. , PAYNE D. 
Published: July 2006

SUMMARYThe relation between temperature, unfrozen water content (UWC) and shrinkage of a number of clays, and the distribution of ice and water within the clays, was studied. The clays included sodium and calcium Wyoming bentonites, < 1 μm and 1–2 μm kaolinite and three English subsoil clays. On freezing blocks of these clays (initial size up to approximately 1 cm3) over a period of months, they shrank progressively with reduction in temperature studied except for the < 1 μm and 1–2 μm kaolinites, which ceased shrinking at – 0.24°C and – 0.73°C respectively. During shrinkage, the water in the clay blocks migrated to freeze outside the blocks where ice was already nucleated. After equilibration for a month at – 0.19°C and at – 0.73°C, the water contents of the finer clays, excluding ice bands, equalled the UWCs measured previously using a differential scanning calorimeter. Two stages of ice formation were apparent in the curves of UWC vs temperature and were attributed to the different locations of the ice in the clays. Initially, ice formed in bands outside the clay matrix, accompanied by clay shrinkage (Stage 1). After a shrinkage limit had been reached ice began to form within the pores of the clay (Stage 2). Comparisons of the results of these freezing experiments with conventional moisture‐release curves showed that the suction of the unfrozen water in clays was, within experimental error, as predicted by the Schofield equation. Results are also discussed in terms of ice‐water and air‐water interfacial tensions.
Determination of effective diffusion coefficients for gaseous and dissolved organic substances in soil material using a ‘stopped elution’ method with HPLC and GC
Authors: GOSS K‐U. , SCHRAMM K‐W. 
Published: July 2006

SUMMARYNon‐steady‐state diffusion of chemicals in soil can be described by Fick's second law using suitable effective diffusion coefficients. In this study a ‘stopped elution’ method was used to determine experimentally these effective diffusion coefficients for gaseous and dissolved substances in dry and water‐saturated soil. For this purpose a high‐performance liquid chromatography (HPLC) apparatus and a gas chromatograph (GS) were used in combination with soil‐filled columns. The method is based on the observed spreading of a substance moving through a soil column. This broadening is the result of several processes, one of which is diffusion. A suitable experimental design permits the separate measurement of that part of the widening caused by diffusion.The measured effective diffusion coefficients were compared with theoretical values calculated using predictive algorithms from the literature. For liquid‐phase diffusion the maximum deviation between the calculated and the measured values was 34%. The experimental results for gaseous diffusion showed systematic upward deviation from the calculated Coefficients. This might be caused by the diffusion of molecules in the adsorbed state, a phenomenon that had been neglected in the calculations.