bluuebunny/crossref_metadata_2025_split huggingface dataset:
EXTRACTABLE SESQUIOXIDES IN SIX MEDITERRANEAN SOILS DEVELOPED ON BASALT AND SCORIA
Authors: SINGER ARIEH 
Published: July 2006

SummaryIron, Al, and Mn were extracted by oxalate and dithionite from two Brown Mediterranean Soils, two Red Mediterranean Soils, one Vertisol and one Gley soil, all derived from basalt or scoria in the sub‐humid and humid Mediterranean regions of the Golan Heights.Ratios of oxalate: dithionite extracted iron (Feo:Fed) were low in all soils, indicating that the predominant form of free iron is crystalline. Feo accumulates in the argillic B horizons of the Mediterranean soils, while Fed accumulates in the surface horizons. A large part of the free iron oxide in the surface horizons of Mediterranean soils is associated with non‐clay fractions. While manganese behaves in a manner somewhat similar to that of iron, no definite trends could be discerned in the vertical distribution of free aluminium.In the Vertisol, Feo and Mno accumulate in the subsoil. Fed and Mnd increase slightly with soil depth. In the Gley soil, amorphous iron accumulates in the surface horizon, total free iron in the bottom horizon. Both amorphous and total free Mn had been depleted from the upper horizons of the Gley soil.
THE WEATHERING OF CHLORITIC MINERALS IN SOME SCOTTISH SOILS
Authors: BAIN D. C. 
Published: July 2006

SummaryThe mineralogy of 14 chloritic soils of various drainage classes developed on different parent materials from the Loch Awe area of Argyllshire, Caithness, and the Southern Uplands reveals only minor variations'in clay mineralogy with profile depth, the frequent presence of primary minerals indicating that all the soils are immature, and that weathering is at an early stage. Iron‐rich chlorite generally persists throughout the profiles, varying little in amount or chemical composition between horizons; where identifiable, the polytype is II b. Oxidation of iron modifies the thermal characteristics of the chlorite in all the freely‐drained soils but usually only in the surface horizons of gleys. Irrespective of soil type or drainage class, in most profiles chlorite weathers only slightly, probably by vermiculitization around the edges of flakes.
MINERALOGY AND CHEMISTRY OF A TRANSVAAL BLACK CLAY TOPOSEQUENCE
Authors: HTZPATRICK R. W. , LE ROUX J. 
Published: July 2006

SummaryMoralistic soils (vertic and non‐vertic black clays) were sampled along a 200 m top sequence in the Transvaal Highveld, South Africa. The Milk wood soil on the upper part of the margalitic top sequence has an Al horizon which lacks both slickensides and self‐mulching properties but has strong blocky structure, the others are all self‐mulching (i.e. Vertisols). The Vertisols differ in some morphological properties such as the absence (Mngazi series) and presence (Arcadia series) of pedogenic calcite accumulation, both overlying decomposed dolerite, whereas the third member from a red‐black centenary sequence is calcareous with a gleyed subsoil horizon.Chemical and XRD analysis suggest that the clays of the Vertisols comprise mainly a partly chloritized iron‐rich smectite with Ie > Mg + Al in the octahedral layer (and interlayer positions), while in the upland Milkwood soil intergradient halloysitic clay occurs in addition to a more‘open’structured chloritized iron smectite. The mineralo‐chemical results and the geomorphic data suggest that the genesis of these soils is controlled primarily by the internal soil water regime.
CANONICAL CORRELATION IN PEDOLOGY: HOW USEFUL?
Authors: WEBSTER R. 
Published: July 2006

SummaryCanonical correlation is an analytical technique for relating one multivariate set of measurements on a population to another in terms of linear functions of the two sets. It can express quantitatively the relation between the soil, described by one set of variates, and its environment, described by another, and attempt statistical prediction of the one from a knowledge of the other. The method is described briefly, and applied to soil and environmental data from soil surveys in Britain (the Dee catchment of North Wales) and Australia (Ginninderra in the Australian Capital Territory and the Wungong Brook catchment near Perth, Western Australia).The technique is judged to be a useful exploratory tool for seeking relations in situations that are little known or understood.
REMOVAL OF CONTAMINANTS TO IMPROVE THE RELIABILITY OF RADIOCARBON DATES OF PEATS
Authors: GOH K. M. 
Published: July 2006

SummaryPeat samples from Timaru Downs, New Zealand were subjected to a wide range of chemical treatments before radiocarbon assay. A step wise procedure was used in which each sample was radiocarbon dated before and after the treatments were applied. The criterion adopted for indicating the removal of young contaminants and thus resulting in the improvement in the reliability of radiocarbon dates is the increase in the radiocarbon age of the sample after treatment.When peat samples were radiocarbon dated without prior chemical treatments the results could not be used to accurately date the time of formation because of young contaminants. Contaminants could be removed by chemical treatment of peats with mineral acids, particularly 70% HNO3 for the very old peat sample. The improvement brought about by acid treatment was greater than that from the classical humus extraction and fractionation method.
A SIMPLE ELECTROLYTIC RESPIROMETER‐LEACHING TUBE COMBINATION FOR SOIL METABOLISM STUDIES
Authors: TRIBE H. T. , BEWICK M. W. M. 
Published: July 2006

SummaryAn apparatus is described consisting of a combination of an electrolytic respirometer and a leaching tube. This allows determination in the same soil sample of O2 uptake, CO2 release, and N release as NO3−, NH4+, and NH3 Release of other water soluble components can also be followed. Unlike other electrolytic respirometers the apparatus measures O2 uptake directly, the O2 being replaced periodically by electrolysis. Fluctuations in electrolyte level due to changes in atmospheric temperature and pressure are compensated for using a control apparatus with a volume equal to the air space in the experimental apparatus. The simplicity of the apparatus allows ready replication.
COMPARISON OF AQUEOUS ACETYLACETONE AND POTASSIUM PYROPHOSPHATE SOLUTIONS FOR SELECTIVE EXTRACTION OF ORGANIC‐BOUND Fe FROM SOILS
Authors: BASCOMB C. L. , THANIGASALAM K. 
Published: July 2006

SummarySeven samples of iron oxyhydroxides, characterised by crystallinity and surface area (monolayer water content), were examined for solubility in aqueous acetylacetone (0.68 M), potassium pyrophosphate pH 10 (0.1 M) and acid ammonium oxalate pH 3 (0.2 M). Solubilities in acetylacetone and oxalate were dependent on surface area, being 30 per cent Fe or more for non‐crystalline oxides in 40 h. Solubility in pyrophosphate was 2 per cent Fe or less in 40 h even when surface area was 300 m2/g.Pyrophosphate solution was more suitable than aqueous acetylacetone for selective extraction of iron‐organic complexes from soils which contain amorphous or poorly crystalline iron oxides.
OPTIMALLY PARTITIONING SOIL TRANSECTS
Authors: WEBSTER R. 
Published: July 2006

SummaryTwo methods are described for locating soil boundaries on transects from multivariate data. One method (split moving‐window, SMW) examines a transect through a window which is split at its mid point and the two halves compared. The window is moved along the transect and a boundary inferred wherever the difference between the two halves attains a local maximum. The other (maximum level‐variance, MLV) examines all possible partitions of a transect that can be produced by a given number of boundaries or less and places boundaries in those positions that minimize the within‐segment sum of squared deviations from the segment means (and hence maximize the between‐segment sum of squares). The performances of the two methods are compared for two soil transects in Oxfordshire. MLV identified all major changes even where gradual, but was less reliable for small changes. SMW identified all sharp boundaries, even between soil types that are fairly similar. In its original form SMW did not identify gradual changes reliably, but its performance was improved both by omitting data near the centre of the window and by concentrating the discriminating power of the data beforehand as in MLV. SWM requires less computing than MLV.
THE SIGNIFICANCE OF SOIL VARIABILITY FOR FOREST SOIL STUDIES IN NORTH‐EAST SCOTLAND
Authors: BLYTH J. F. , MACLKOD D. A. 
Published: July 2006

SummaryA study of 13 sample plots (0.01 ha) in 6 forests showed that the average number of topsoil samples required per plot to secure 95 per cent confidence limits for a range about the mean of 10 per cent was 6 for total nitrogen, 9 for total phosphorus and 29 for 0.5 M acetic acid extractable nutrients (calcium, magnesium, phosphorus and potassium). In some plots 95 per cent confidence intervals, based on 5 composite samples, for extractable nutrients were as large as the range of mean values for different plots within a forest. High variability within plots causes large variation in correlation coefficients between tree growth and soil properties so that the intensity of sampling should be of the order indicated above to identify factors affecting growth. For predicting timber yield the accuracy of regression equations containing predictors of high within‐plot variability is too low to be of practical value. The sampling effort required to achieve a given level of precision does not increase greatly when plot size is increased from 0.01 to 0.1 ha. Since Yield Class, the most useful measure of growth, is not designed for areas less than 0.5 ha, the use of the larger plot size is recommended.
A GAS FLOW‐THROUGH SYSTEM FOR STUDYING DENITRIFICATION IN SOI
Authors: WICKRAMASINGHE K. N. , TALJBUDEEN O. , WITTY J. F. 
Published: July 2006

SummaryA continuous gas ‘now‐through’ system, incorporating a soil incubation cell and a gas sampling device, was developed to measure the nitrogen and carbon losses as gaseous N2, N2O, NH3 and CO2 from soil during denitrification under ‘steady state’ anaerobic conditions. Nitrogen was added as KNO3 to the soil in amounts equivalent to 0, 30,100 and 300 kg N ha‐1.At 25 °C and one quarter of the water‐holding capacity, N2 and N2O evolution accounted for most of the nitrogen lost. In the effluent gas stream, N2O appeared about six hours after anaerobic conditions were established, and increased steadily. Initial N, production was small and reached a maximum between 90 and 100 h with a simultaneous decrease in N2O evolution. Gaseous N losses were highest with the 100 kg N ha−1 treatment and accounted for 59 per cent of the nitrate lost.A weight ratio, CO2 ‐C/(N2 O + N2)‐N of 1.0–1.3 was observed in the effluent gas once a ‘steady state’ was achieved, which conforms with that expected from nitrate respiration when N, and N2O are produced simultaneously. When denitrification ceased, CO2 production decreased to a steady rate. An increase in the duration, rather than the rate, of denitrification was observed when more N was added. A time lag before the onset of a maximum rate of denitrification was also observed, which increased with the amount of added N.
A SYSTEM FOR MEASURING THE RATES OF EVOLUTION OF NITROUS OXIDE AND NITROGEN FROM INCUBATED SOILS DURING DENITRIFICATION
Authors: GALSWORTHY A. M. , BURFORD J. R. 
Published: July 2006

SummaryAn incubation system is described for studying denitrification rates in incubated soil by measuring the gaseous products removed in a stream of helium flowing across the soil.The system has been used to demonstrate the effect on denitrification of air‐drying a soil. A constant rate of denitrification occurs in soil pre‐incubated aerobically at 50% water holding capacity for a period of 3 weeks prior to the denitrification assay. By contrast, air‐dry soil wetted immediately prior to denitrification measurement showed a rapid increase in denitrification rate to a maximum at 1–3 days and a decline thereafter until a steady state is reached about 2–4 weeks after rewetting. Nitrous oxide was the dominant product from both soils studied: the ratio of N2O to N, in the gases evolved changed little with time for the pre‐incubated soil, but diminished with time of incubation for the air‐dried soil.
MEASUREMENT OF THE MOBILITY OF SOIL COLLOIDS
Authors: DIXIT S. P. 
Published: July 2006

SummaryA method is described for measuring the relative mobility (RM) of colloidal suspensions. It was used to assess the potential mobility of clay in the horizons of 12 profiles from Belgium, Bolivia, Brazil and India.The colloid from surface horizons of soil was always more mobile than that from deeper layers. The values of relative mobility differed between profiles and appeared to give a useful indication of potential clay migration under natural conditions.
UNSTEADY TWO‐DIMENSIONAL INFILTRATION FROM SEMI‐CIRCULAR FURROWS
Authors: SOLIMAN N. F. , BAKR H. M. A. , HASSAN M. N. , BOTROS Y. Z. 
Published: July 2006

SummaryThe water flow equation for two‐dimensional, unsteady infiltration from semicircular furrows in unsaturated soil is solved numerically with the aid of the alternating‐direction implicit (ADI) difference method. Laboratory experiments were conducted on infiltration from semi‐circular furrows into sandy clay loam sott contained in a model tank. Water contents measured at different locations for different times were in close agreement with the predicted moisture profiles and the locations of the wetting fronts.
CHARACTERIZATION OF WATER DISPLACEMENT IN SOILS USING SIMPLE CHROMATOGRAPHIC THEORY
Authors: THOMAS G. W. , PHILLIPS R. E. , QUISENBERRY V. L. 
Published: July 2006

SummarySimple chromatographic equations were adapted to describe frontal water displacement by tracer‐containing water in soils where only partial displacement occurs. The equations were shown to give excellent agreement with experimental data in five field experiments where tracer was added in artificial rainfall. The consequences of partial displacement for soil water replenishment in the root zone, salt leaching and ground water recharge are discussed.
ANALYSIS OF ONE‐DIMENSIONAL STEADY FLOW IN CONSTRAINED SWELLING SOILS
Authors: TOWNER G. D. 
Published: July 2006

SummaryThe relation between the steady‐state flow rate in horizontal columns of swelling soils and the pressure difference applied across the ends is derived for small flow rates. The slope of the curve representing the relationship at zero flow rate gives the value of the hydraulic conductivity corresponding to the initial water content (and hence to the average water content). The result is valid for hysteretic systems.The curves are concave to the pressure axis for published moisture characteristics. However, they can be convex for characteristics of a form that has not been reported but which does not violate known physical laws. A particular hydraulic conductivity/water content relationship leads to linear curves.
THE MEASUREMENT AND MECHANISM OF ION DIFFUSION IN SOILS. IX. CHANGES IN SOIL ACIDITY NEAR A SOURCE OF BICARBONATE IONS
Authors: RAMZAN M. , NYE P. H. 
Published: July 2006

SummaryTo simulate processes tending to raise the pH of soil near a plant root, a stack of moist HCO‐3saturated ion exchange resin papers was placed in contact with non‐calcareous soil of varying pH, containing HC1 + CaCl2 in the soil solution. Changes in the concentration profiles of Ca2+, Cl‐ and H+ in the soil were followed. HCO‐3 released from the resin in exchange for soil Cl‐ reacted with the soil and raised its pH. Increases of up to 1 unit were measured near the interface. The zone of pH increase extended into the soil much less than the zone of chloride depletion. It was shown that Ca2+ could accumulate near the interface in the absence of mass flow in this experimental system.
ASSESSMENT OF SOIL POTASSIUM RESERVES AVAILABLE TO PLANT ROOTS
Authors: TALIBUDEEN O. , BEASLEY J. D. , LANE P. , RAJENDRAN N. 
Published: July 2006

SummarySuccessive extraction with Ca‐saturated sulphonated resin is used to remove potassium from soils. The kinetics of K‐release are analysed mathematícally to define three simultaneous rate processes by the amounts and rate‐functions associated with them. The diffusion coefficient (3 × 10‐19 cm2 sec‐1) calculated for the slowest process (suggested to be from the mineral matrix) is of the same magnitude as that for illitic clay minerals. The effect of K manuring on these parameters is evaluated from measurements on soils from the Nil and K‐fertilised plots of the Rothamsted Classical Experiments.Based on this analysis, a procedure is suggested for deriving from a smaller number of observations the amount of K a soil would release in a given time, and the contribution of each process to this amount is demonstrated.
THE SIGNIFICANCE OF TRUNCATION IN THE EVOLUTION OF SLOPE SOILS IN MID‐WALES
Authors: ADAMS W. A. , RAZA M. A. 
Published: July 2006

SummaryThe pattern of loss and gain of Fe was quantitatively determined for the soils of two hill slope sequences in mid‐Wales. Overall, both sequences showed a net gain in Fe, with individual profiles showing gains related to slope. The pattern of gains is discussed in relation to lateral movement, aerial input and movement of Fe out of the hill mass. It is concluded that creep erosion (truncation) offers the only adequate explanation of the data recorded; further, that truncation is concurrent with vertical redistribution of Fe and constitutes a major evolutionary process on sites with slopes greater that l0°
COMPARISON OF DIFFERENT FORMS OF PHOSPHATE FERTILIZERS PART II: GRASSLAND
Authors: ARCHER F. C. 
Published: July 2006

SummarySuperphosphate, granular and powdered basic slag, and normally and very finely ground Gafsa rock phosphate were compared as sources of phosphorus for established grassland under a wide range of conditions in England and Wales. Superphosphate and both forms of basic slag were about equally effective in all cases. Gafsa rock phosphate was a useful form of phosphate for grassland where the soil pH value was below about 6.0, but it was much less effective and slower acting on neutral soils or where lime had recently been applied. Very finely ground rock phosphate was only slightly more effective than the normally ground form, and their value as phosphatic fertilizers depended primarily on soil pH rather than on rainfall.
MEASUREMENT AND MECHANISM OF ION DIFFUSION IN SOIL X. PREDICTION OF SOIL ACIDITY GRADIENTS IN ACID‐BASE TRANSFERS
Authors: NYE P. H. , RAMZAN M. 
Published: July 2006

SummaryThe concentration gradient of soil acid neutralised when a block of moist soil was placed in contact with a source of HCO3‐ was predicted from an equation for diffusion of HCO3‐, and its simultaneous reaction with the soil. The reaction was defined by empirical rate constants describing the changes of pH with time in a soil: M/100 CaCl2+ KHCO3 solution, suspension system. Values of these constants, determined independently, were too large resulting in prediction of steeper and leas extensive concentration profiles of soil acid neutralised than measured in the diffusion system. The true pH of the soil pore solution in the block would have been considerably greater than a predicted ‘equilibrium’ pH. The consequences for rhizosphere processes are discussed.
MÖSSBAUER EFFECT AND MAGNETIC STUDIES OF SECONDARY IRON OXIDES IN SOILS
Authors: LONGWORTH G. , BECKER L. W. , THOMPSON R. , OLDFIELD F. , DEARING J. A. , RUMMERY T. A. 
Published: July 2006

SummarySimple, rapid and non‐destructive measurements of magnetic properties (magnetic susceptibility, saturation isothermal remanent magnetization and coercivity of isothermal remanence) coupled with more time consuming and sophisticated analyses such as thermomagnetic and Mössbauer effect studies, provide a basis for identifying forms of iron oxide present in the soil.At two of the sites studied, Caldy Hill, Merseyside, and Llyn Bychan, N. Wales, the secondary ferrimagnetic oxide formed in surface soil as a result of recent forest fires is shown to be non‐stoichiometric magnetite approximating to the formula Fe2. 904. No evidence for the presence of maghemite was found in any of the soil samples from these sites or in soils from the Annecy region of S.E. France.
CATENA OF SODIUM‐RICH SOIL IN RHODESIA
Authors: STOCKING M. A. 
Published: July 2006

SummaryThe spatial pattern of sodium in soils was investigated in a catenary sequence in central Rhodesia. Sodic horizons occurred predominantly in mid‐slope and are related to (a) fluctuations in water table, (b) poor lateral drainage and a perched water table and (c) the weathering rate of feldspars. Observations suggest that a subsurface dam wall is responsible for lack of groundwater drainage and that this impediment to lateral drainage is caused primarily by excess sodium and the dispersion of clays. Near‐surface fluctuations of the water table encourage weathering and increase the sodium concentrations. The existence of a perched water table and readily dispersibte soil may have important implications in erosion, explaining why sodium‐rich soils are often associated with severe erosional phenomena especially in tropical and subtropical environments.
POTASSIUM RESERVES IN A SANDY CLAY SOIL FROM THE SAXMUNDHAM EXPERIMENT: KINETICS AND EQUILIBRIUM THERMODYNAMICS
Authors: GOULDING K. W. T. , TALIBUDEEN O. 
Published: July 2006

SummaryPotassium‐calcium exchange equilibria in, and the kinetics of K release from, soil from the Nil and PK treatments of the Saxmundham Experiment, Rotation 1, and the Ga, Ca + K and K saturated panicle size fractions of the soils were investigated.The free energy and enthalpy ot exchange showed K preference in all the solids. Selectivity for K decreased with increasing particle size and pre‐treatment with K salts. A comparison of the ‘differential enthalpy of exchange: per cent K saturation’ relationship for the whole soil with those of the particle size fractions suggests that soil dispersion during particle size separation also decreased K selectivity significantly. When related to the mineralogical composition of the soil, the differential enthalpy data suggest that maximum K. selectivity is associated with a vermiculite/smectite component of inter‐stratified minerals in the soil.Isotopic exchange using 4sCa on the decalcified solids showed a measurable rate of exchange for the Ca forms of the <0.2 and 0.2–2 /μm fractions. This is attributed to traces of blocking materials (CaCO3 or hydroxy‐aluminium polymers), which are removed or rendered porous during treatment with dilute KCl solution, so that isotopic exchange with Ca is then much more rapid.The kinetics of K extraction with a Ca saturated resin, interpreted on the basis of a three‐compartment model, suggest that sorbed K and K released by ‘fast’ and slow processes, representing sites of low and high K selectivity, were associated with minera‐logically distinct phases in the various particle size fractions.
MAGNETITE ALTERATION IN DEEPLY WEATHERED ADAMELLITE
Authors: GILKES R. J. , SUDDHIPRAKARN ANCHALEE 
Published: July 2006

SummaryMagnetite grains in deeply weathered granitic rocks in Western Australia altered to haematite pseudomorphs which usually had magnetite cores. No evidence was found for maghemite development either as a separate phase or in solid‐solution with magnetite.