bluuebunny/crossref_metadata_2025 huggingface dataset:
THE MEASUREMENT AND CHARACTERISATION OF VOIDS IN SOIL THIN SECTIONS BY IMAGE ANALYSIS. PART II. APPLICATIONS
Authors: MURPHY C. P. , BULLOCK P. , BISWELL K. J.
Published: July 2006

Image analysis was used to measure and characterise the voids in two sets of soil samples; (i) a surface water gley soil of the Deighton series and (ii) soils from a compaction experiment. The results show that the Deighton soil contains two impervious horizons separated by a much more porous horizon. In all the horizons most of the pore space is due to pores >180μm diam. In the case of the soils from the compaction experiment compaction was shown to change the shape, orientation and size distribution of the pores considerably. The range of measurements demonstrates that image analysis is applicable to several areas of soil research.
ISOTOPIC EXCHANGE OF PHOSPHATE ON SOME PHOSPHATIC COMPOUNDS
Authors: de BUSSETTI S. G. , FERREIRO E. A. , HELMY A. K.
Published: July 2006

The kinetics of isotopic exchange of phosphate on hydroxyapatite, amorphous aluminium phosphate, phosphate‐treated aluminium oxide and dicalcium phosphate dihydrate were studied in aqueous suspensions as a function of solid/solution ratio and amount of added isotope. The tracer exchange reaction was independent of time for the dicalcium phosphate due to a very small amount of exchangeable phosphate found in the solid and to the high solubility of the material. For the other phosphates, a power function and/or a function composed of a series of exponential terms were found suitable for representing the tracer kinetics. The theoretical background for both functions is shown to be approximately the same. Both describe tracer kinetics for a system containing more than one solid phase. The amounts of exchangeable P were found to depend strongly on the solid/solution ratio but not on the amount of radioactivity added. The dependence of the tracer kinetics on the solid/solution ratio is due to the ageing processes that give rise to the formation of surface layers having physical and chemical properties different from those of the bulk solid.
FRACTIONATION OF HUMIC ACID BY GEL PERMEATION CHROMATOGRAPHY
Authors: ANDERSON H. A. , HEPBURN A.
Published: July 2006

Humic acids from the L layer and B2hhorizons of a humus‐iron podzol were fractionated by gel permeation chromatography. Elution of the gel column with distilled water adjusted to pH 7.5 gave a fractionation based on both gel permeation and adsorption chromatography. This procedure gave filtered products containing most of the organic nitrogen, and an absorbed fraction. The latter contained most of the components which gave benzene carboxylic acids on oxidation of the humic acid with dilute nitric acid.
SIZE FRACTIONATION, DISSOLUTION ANALYSIS, AND INFRA‐RED SPECTROSCOPY OF HUMUS COMPLEXES IN ANDO SOILS
Authors: HIGASHI TERUO , WADA KOJI
Published: July 2006

Eight samples of Ando soil A1 and buried A1 horizons of different ages were fractionated into clay‐, silt‐, and sand‐size separates, and the yields and carbon contents of these separates were determined. The clay‐size separates were subjected to two series of successive extractions, 1) 0.1 M Na4 P2 O7/2% Na2 CO3/0.5 M NaOH and 2) dithionite‐citrate/2% Na2 CO3/0.5 M NaOH; and to difference infra‐red spectroscopy for identification of the extracted constituents.

The result indicated that humus evolves from forms with a very low complexing ability for Al and Fe into forms that complex Al and Fe in the A1 horizon, and that humus further interacts with allophane‐like constituents, allophane and imogolite in the buried A1 horizon. These reactions between humus and inorganic constituents result in formation of silt‐ and sand‐size aggregates which are stable to sonic wave treatment, but are broken down into finer particles upon boiling with H2 O2.
EXTRACTABLE SESQUIOXIDES IN SIX MEDITERRANEAN SOILS DEVELOPED ON BASALT AND SCORIA
Authors: SINGER ARIEH
Published: July 2006

Iron, 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

The 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

Moralistic 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

Canonical 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

Peat 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

An 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

Seven 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

Two 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

A 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

A 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

An 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

A 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

The 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

Simple 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

The 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

To 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

Successive 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

The 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

Superphosphate, 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

The 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

Simple, 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

The 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.
SOME PRIORITIES FOR BRITISH SOIL SCIENCE1
Authors: COOKE G. W.
Published: July 2006

A Presidential Address provides an opportunity for an account of the state of the subject and a reading of the signposts which seem to point to future progress. The broad philosophical aspects of soil science were discussed by E. M. Crowther (1953) a quarter of a century ago in ‘The Sceptical Soil Chemist’, a paper which is worth reading again. This year our Vice‐President, D. J. Greenland (1978) discussed ‘The Responsibilities of Soil Science’. I shall concentrate on discussing some ways in which soil scientists may contribute further to agricultural development.
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

Potassium‐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

Magnetite 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.
COLLECTION AND EVALUATION OF LARGE SOIL MONOLITHS FOR SOIL AND CROP STUDIES
Authors: BELFORD R. K.
Published: July 2006

A technique is described which allows collection and transportation of undisturbed soil monoliths in glass fibre casings 80 cm in diameter and 135 cm deep. The technique has been used to obtain 150 monoliths from a range of soil types in England and Wales, including soils with compact or chalky horizons.

Measurements from lysimeters containing a non‐swelling sandy loam and a swelling clay showed that the hydraulic properties of both soils were not affected by encasement of the profiles, provided that supplementary drainage outlets at the depth of field mole drains were provided in the lysimeters containing the clay soil. Aeration of the clay monoliths was comparable with that of the same soil in the field.

When winter wheat plants growing on the lysimeters were surrounded by a similar guard crop, yields were equivalent to those obtained in the field. Edge effects were not significant; plants grown adjacent to the lysimeter wall yielded the same weight of grain per unit soil area as those in the central area of the monolith.
ROTHAMSTED STUDIES OF SOIL STRUCTURE VII.
Authors: SKINNER F. A.
Published: July 2006

Natural aggregates of topsoil samples of six British soils (Hanslope, Ragdale, Evesham, Denchworth, Flint and Salop) were incubated with added nutrients and changes in their stability to wet sieving determined. Under anaerobic incubation the type of nutrient added had little effect on stability. Aerobic incubation with glucose gave a larger proportion of stable aggregates than with water. With peptone stability usually decreased, and occasionally increased, which may indicate differences in the binding mechanisms of the soil particles. Both sterile and unsterile aggregates incubated with water became more stable than controls; the rapidity of this change suggested a physical, rather than microbiological cause. Very stable grassland aggregates changed little on aerobic incubation with water, but became more stable with solutions of glucose or peptone. Artificial aggregates made from the same soil developed considerable stability to water on aerobic incubation, but remained almost totally unstable when incubated anaerobically.
THE INFLUENCE OF MAGNESIUM IN SALINE AND SODIC SOILS: A SPECIFIC EFFECT OR A PROBLEM OF CATION EXCHANGE?
Authors: RAHMAN W. A. , ROWELL D. L.
Published: July 2006

Na‐Mg and Na‐Ca exchange isotherms were determined at electrolyte concentrations of 500, 50, 5 and 1 meq per litre for illite, vermiculite and montmorillonite and for three soils containing illite and montmorillonite. This enabled comparisons to be made of clay swelling, dispersion and soil hydraulic conductivity changes between the Na‐Mg and Na‐Ca systems at known SAR, ESP and electrolyte concentration.

Na‐Mg montmoriUonite and a montmorillonitic soil behaved identically to the Na‐Ca systems at the same ESP and electrolyte concentration: there was no specific effect. At the same SAR, the higher ESP in the Na‐Mg system caused greater changes than in the Na‐Ca systems. The Na‐Mg vermiculite, illite, illitic soil and mixed illite‐montmorillonitic soil showed greater changes than the Na‐Ca systems at the same ESP, and there was a specific effect. At the same SAR, the higher ESP in all the Na‐Mg systems apart from vermiculite increased the differences, but for vermiculite with a lower ESP, the differences were reduced. The lack of a specific effect for montmorillonite is probably related to the demixing of cations with the divalent ions concentrated on the non‐swelling (internal) surfaces of the crystals.
THE ALTERATION OF PLAGIOCLASES AND AUGITES UNDER DIFFERING PEDO‐ENVIRONMENTAL CONDITIONS
Authors: ESWARAN H.
Published: July 2006

The alteration of plagioclases and augites in lithorelicts were studied in thin sections of five selected profiles which differed in their mineralo‐chemical composition and stage of soil formation. The scanning electron microscope was employed to monitor the products of alteration of the pseudomorphs.

In the base‐rich environment of the Eutropept and Tropudalf, both primary minerals alter to montmorillonite with small amounts of amorphous alumino‐silicates present on the plagioclases, and amorphous materials of undetermined composition on the augite. Local desiliciflcation of the feldspars results in gibbsite.

In more acid environments, as in the Dystropept, the plagioclases alter to metahalloysite and some amorphous aluminosilicates, and the augite to amorphous iron hydrous‐oxide and goethite. In a freely drained environment as in the Tropudult, the alteration of plagioclases leads to kaolinite and locally to gibbsite; all the augite is converted to goethite. No rock relicts are present in the Oxisols.

The differential alteration is a function of the pedo‐environment which is determined by the rate and amount of water percolating down the profile.
THE ERODIBILITY OF TWO SOILS FROM KENYA
Authors: BARBER R. G. , MOORE T. R. , THOMAS D. B.
Published: July 2006

A portable rainfall simulator was used to measure the runoff rates and soil losses from a freshly ploughed luvisol at Katumani, and a nitosol at Kabete, on a 6° slope at varying rainfall intensities. The soil losses from storms of 50 and 100 mm/h intensities, in which a total of SO mm rain was applied to plots in the wet moisture state, varied from 0.8 to 1.4 metric tons/ha at Kabete and 8.5 to 13.9 metric tons/ha at Katumani. The percentage runoff from these storms was 15 to 17 per cent at Kabete and 67 to 71 per cent at Katumani. The much greater runoff rates from the Katumani soils were shown to be due to surface capping caused by degradation of the surface structure. It has been proposed that soil credibility K factors of 0.4 and 0.04 could be used for the Katumani and Kabete soils respectively in the Universal Soil Loss Equation
RAPID REPRESENTATIVE SAMPLING OF SOIL GASES AND THEIR DETERMINATION BY MASS SPECTROMETRY
Authors: ROBERTSON G. W. , BRACEWELL J. M.
Published: July 2006

The use of a portable field probe for sampling soil gas gives the degree of replication necessary to allow for the local variability of soil gas composition over short distances, and mass spectrometry provides a quick and efficient method of analysis for gases at concentrations above 0.1% by volume. These methods can conveniently be combined and their use is illustrated by the determination of N2, O2, Ar, CO2 and CH4 in two soils having impeded gaseous exchange with the atmosphere.
THE INFLUENCE OF MAGNESIUM AND OF EASILY WEATHERED MINERALS ON HYDRAULIC CONDUCTIVITY CHANGES IN A SODIC SOIL
Authors: ROWELL D. L. , SHAINBERG I.
Published: July 2006

Exchangeable Mg appears to have no specific effect on soil hydraulic conductivity of A and C horizons of a sodic sandy loam soil (montmorillonite and kaolinite clay minerals) leached with solutions which cause clay swelling to be the dominant mechanism reducing conductivity (SAR < 20, electrolyte concentration 10 meq per litre). There is some evidence of a specific effect when these soils are subsequently leached with water which causes clay dispersion to become important. Fresh loess in the A horizon dissolves in percolating rainwater, causing difficulties in the replication of experiments. It seems to give a small degree of ‘self protection’ to soil structure, a property likely to be operating in other soils affected by recent loess deposits.
CHANGES IN MOLECULAR WEIGHT DISTRIBUTION OF SOIL ORGANIC MATTER DURING SOIL DEVELOPMENT
Authors: GOH K. M. , WILLIAMS MARY R.
Published: July 2006

Ten different topsoils representing members of three soil chronosequences were pre‐treated with 0.1 M HC1 and extracted with neutral 0.1 M Na4P2O7 followed by 0.5 M NaOH. Extracts were purified and fractionated into five different nominal molecular weight fractions using gel filtration. With increasing soil development, the proportion of large molecules (>200 000) in the organic matter decreased with an increase in the proportion of intermediate size molecules (200 000 – 10 000). This effect was more evident in the mild Na4P2O7 extracts than in the subsequent NaOH extracts, and in soils of the Manawatu chronosequence than in those of the other two chronosequences and are attributed to changes in the nature and humification of soil organic matter during soil development.
AVAILABILITY OF POTASSIUM TO RYEGRASS FROM SCOTTISH SOILS II. UPTAKE OF INITIALLY NON‐EXCHANGEABLE POTASSIUM
Authors: SINCLAIR A. H.
Published: July 2006

The stable desorption parts of soil Quantity/Intensity isotherms were used to determine the contributions of initially exchangeable and non‐exchangeable potassium to plant uptake from ten soils. The activity ratio, ARK= aK/√aCa, Mg at which K was first taken up from non‐exchangeable sources varied from 3 × 10−3 to 8 × 10−3 M1/2 depending on the soil. Uptake rates of two categories of initially non‐exchangeable K were linearly related to √times;. The first category appeared to be close to equilibrium with the initially exchangeable K, and gave effective diffusion coefficients of 10−7 cm2 s−1 for four soils. The second category gave diffusion coefficients from 10−20 to 10−22 cm2 s−1, probably came from internal surfaces of micaceous clays, and began to be released at activity ratios below 3 × 10−4 to 6 × 10−4 M1/2 depending on soil type. The soils fell into three groups, broadly consistent with soil series, on their ability to release the second category of potassium.
EFFECT OF ADSORPTION OF PHENOXYACETIC ACID HERBICIDES ON THE SURFACE CHARGE OF GOETHITE
Authors: KAVANAGH B. V. , POSNER A. M. , QUIRK J. P.
Published: July 2006

Surface charge titration measurements, performed on goethite in the presence of absorbed herbicide ions, indicate that the result of adsorption is to cause an increase in the positive charge of the mineral surface. The titration results, used in conjunction with adsorption measurements to calculate the exchange coefficients for the adsorption reactions, show that there is a significant selectivity in adsorption of the herbicides over the indifferent counterion nitrate. This is believed to be due to the existence of favourable van der Waals interactions between the adsorbed herbicide ions.
THE INFLUENCE OF pH, IONIC STRENGTH AND REACTANT CONCENTRATIONS ON COPPER COMPLEXING BY HUMIFIED ORGANIC MATTER
Authors: SANDERS J. R. , BLOOMFIELD C.
Published: July 2006

The effects of varying the pH and ionic strength, and the concentrations of organic matter, copper, calcium and phosphate upon the complexing of copper by extracts of humified organic matter from laboratory preparations, soil and peat were measured. The extent of complexing increased as pH increased and ionic strength decreased, and with increasing organic matter: copper ratios in a way consistent with the complexant being heterogeneous. Calcium competed with copper for organic matter, but the effect of phosphate was negligible. The extent of complexing at pH 7 by equal weights of colloidal and dialysable material from the same extract were usually similar. Weight for weight of organic carbon, alkali‐extracted humified organic matter complexed copper much more extensively than the corresponding water‐soluble material.
AMINO ACIDS IN BURIED PALEOSOLS
Authors: LIMMER A. W. , WILSON A. T.
Published: July 2006

A sequence of paleosols date at 80, 7 000, 20 000 and 41 000 years developed on similar parent material in the North Island of New Zealand have been used to study the fate of amino acids with time.

Some amino acids were released by hydrolysis with 6M HC1 for 24 h at 110 °C while others were only released after the mineral matrix had been destroyed by HF.

The mineral bound amino acids were hydrolysed from each paleosol and their composition analysed. The simplicity of the composition of the older paleosols confirms that the amino acids are fossil. This technique could be used for determining whether paleosol samples submitted for carbon dating are contaminated by more recent material. The differential disappearance of amino acids from a paleosol could be used as a dating system and if this was done quantitatively it may be possible to date paleosols beyond the range of carbon dating.
EFFECTS OF TILLAGE AND STUBBLE MANAGEMENT ON THE STRUCTURE OF A SWELLING SOIL
Authors: HEWITT J. S. , DEXTER A. R.
Published: July 2006

A method, described previously, is used to quantify the macrostructure within the surface layers of swelling soil. Dissimilarity coefficients are defined and used to quantify soil structural differences resulting from different treatments. Structural differences over small increments in depth are resolved. Effects resulting from different tillage and stubble management practices are distinguished. Differences resulting from burning or retention of stubble had at least as great an effect as tillage practice on the void and aggregate size distributions. However, tillage increased the macro‐porosity.

The structures of two mechanically‐prepared seed beds are compared with the structure of soil on tillage and stubble management trials where seed beds had not been prepared.

It is shown in Appendix I that the structures measured on the two sections through each impregnated soil sample are essentially independent.

A method is presented in Appendix II for converting the structural transition probabilities at unit spacing (e.g. 0.5 mm) to transition probabilities at double spacing (e.g. 1.0 mm). This enables results from different sources, which have been measured on the two scales, to be compared.
A MODEL OF THE EXTENT OF ANAEROBIC ZONES IN AGGREGATED SOILS, AND ITS POTENTIAL APPLICATION TO ESTIMATES OF DENITRIFICATION1
Authors: SMITH K. A.
Published: July 2006

A model has been developed of the variation in the extent of anaerobiosis in aggregated soils with variations in gaseous diffusion coefficients, respiration rate and aggregate size. It extends previously published models of radial diffusion into individual aggregates to a log‐normally distributed population of aggregate sizes such as is known to occur in the field. It considers in particular the situation in which relatively better drainage and aeration occurs in the inter‐aggregate pores than within the aggregates. The model indicates that in most circumstances the effects of variations in the gaseous diffusion coefficients outweigh comparable variations in aggregate size. It is demonstrated how the model may be applied to calculation of rates of denitrification, and two alternative approaches are proposed: one based on the quantities of nitrogen and nitrous oxide diffusing out of partially anaerobic aggregates, the other on the disappearance of nitrate following diffusion into anaerobic zones.
AN INVESTIGATION OF WEATHERING IN SOME ARCTIC‐ALPINE SOILS ON THE NORTHEAST FLANK OF OKSSKOLTEN, NORTH NORWAY1
Authors: ELLIS S.
Published: July 2006

Morphological, particle size and mineralogical analyses of three soils indicate that the degree of weathering during pedogenesis has been of a low order. Textural characteristics and mineral content variations arc attributed largely to inheritance from the till parent material, rather than to pedological processes. These observations suggest that frost action as a soil weathering process in this particular environment is minimal. Hydration and dissolution by chelation are discussed as possible alternative mechanisms, but their operation is probably impaired by restricted water availability resulting from the extensive duration of seasonally frozen ground conditions.
EVALUATION OF POTENTIAL SUBSTRATES TO MONITOR RESPIRATORY NITRATE REDUCTASE ACTIVITY IN SOILS
Authors: RODGERS G. A.
Published: July 2006

Different inorganic ions were tested for their ability to replace nitrate as the terminal oxidant for bacterial respiration in anaerobic soils. Chlorate, bromate. selenate. tellurite and ferric ions were all unsuitable substitutes, lodate reduction in soils was similar to nitrate reduction because it required anaerobic conditions, was increased by glucose amendment and decreased by phenylmercuric acetate. Amendment of soils with iodate and measurement of iodide production can be used to measure nitrate reductase activity in a soil and so give a qualitative indication, and possibly a quantitative estimate, of the denitrification capacity of soils.
THE EFFECT OF SOIL COMPOSITION AND ENVIRONMENTAL FACTORS ON THE SHRINKAGE OF SOME CLAYEY BRITISH SOILS
Authors: REEVE M. J. , HALL D. G. M. , BULLOCK P.
Published: July 2006

The shrinkage potential of natural clods from a variety of clayey soils was measured and related to their physical, chemical and mineralogical properties. It is shown that the most important factors affecting shrinkage are initial bulk density, clay content, organic carbon content and cation exchange capacity of the peroxidised clay, and mica‐smectite content on a whole soil basis. Multiple regression equations involving the initial bulk density, clay content, organic carbon and cation exchange capacity accounted for 87 and 82 per cent of the variation in total shrinkage of topsoils and subsoils respectively.

Because of restrictions on shrinkage imposed by factors such as climate, crops, ground‐water and moisture release characteristics of soils, soils with a high shrinkage potential may not behave very differently to soils with a much lower potential. On these grounds it is concluded that the shrinkage criteria used in US Taxonomy are not applicable in Britain.
COMPARISON OF THE CERAMIC PLATE AND THE PRESSURE MEMBRANE TO DETERMINE THE 15 BAR WATER CONTENT OF SOILS
Authors: WATERS PATRICIA
Published: July 2006

Volumetric water contents of 17 mineral and 3 peat soils were measured at 15 bar pressure using the ceramic plate and the pressure membrane apparatus. There was no overall significant difference between the results from the two types of apparatus and both ranked the soils in essentially the same order. Although soils of high clay or organic matter content retained up to 13.5% more water on the ceramic plate than on the pressure membrane, available water capacity (AWC) of a clay soil would be decreased by only 1–2%, and that of a peat soil by 3–4%. Due to its greater reliability, the ceramic plate is an acceptable alternative to the pressure membrane when used to determine the 15 bar water content.
THE CONTENTS AND SORPTION OF CADMIUM IN SOME AGRICULTURAL SOILS OF ENGLAND AND WALES
Authors: JARVIS S. C. , JONES L. H. P.
Published: July 2006

Cadmium sorption was measured in 10 agricultural soils with pH ranging from 4.5 to 7.9, and total Cd content from 0.27 to 1.04 μg g−1 dry soil. With initial Cd concentrations of 0.5 to 100.0 μM, sorption from 0.002 M CaCl2 was described by the Freundlich adsorption equation but the gradients of the isotherms increased when the initial concentrations were below 0.5 μm. This indicates that there are specific sites of differing sorption energy; differences between soils in the gradients of the isotherms at low initial concentration could largely be accounted for by their contents of ‘free’ Fe2O3. When initial concentrations were below 0.5 μm there was a linear relationship between the quantity of Cd sorbed and the final concentration in solution. This relationship held with all soils except that of lowest pH from which there was a net loss of Cd to the solutions. Desorption was measured from three soils with contrasting pH. With the soil of lowest pH, over 80 per cent of sorbed Cd was desorbed to 0.002 m CaCl2 and up to 30 per cent to 100 or 500 μm solutions of heavy metal chlorides. In contrast, only very small proportions (<1.25 per cent) were desorbed from the other soils with pH 6.7 and 7.8.

The results indicate that Cd is strongly sorbed by soils of pH of above 6.0 when added in amounts comparable to additions in sewage sludges or phosphatic fertilizers, and illustrate the importance of liming as a means of reducing the mobility of this metal in soils.
THE MONOSACCHARIDE COMPOSITION OF POLYSACCHARIDES IN ANDO SOILS
Authors: MURAYAMA SHIGETOSHI
Published: July 2006

The monosaccharide composition of Ando soils, which originate from volcanic ash and have high organic matter content (8–21% carbon), was quite different from that of non‐volcanic ash soils (1.2–1.9% carbon), being richer in mannose, fucose and ribose, whereas there was less glucose in cellulose‐like form, arabinose, xylose and rhamnose. The Ando soils were also characterized by a lower percentage of organic carbon in the form of saccharide (4.4–7.4%) in comparison with non‐volcanic ash soils (10.5%), though the former soils contain a greater amount of saccharides.

The monosaccharide composition of Ando soils was unrelated to the vegetation, land usage, or climatic conditions, and is presumed to be a soil characteristic resulting from the preferential accumulation of microbial polysaccharides.