bluuebunny/crossref_metadata_2025 huggingface dataset:
K‐ACTIVITY RATIOS AND THE UPTAKE OF POTASSIUM BY RYEGRASS IN THE FIELD
Authors: BECKETT P. H. T. , CLEMENT C. R.
Published: July 2006

A model (based on the short‐ and long‐term Q/I relations of K in a soil, on graphs of K‐uptake by crop against post‐uptake K‐activity ratios, and the exhaustion value of K‐activity ratios below which K can no longer be taken up) is presented by means of which to estimate the amount of labile K in a soil, and to compare the contributions of labile and fixed K to plant uptake. The application of the model was partially explored in a field experiment. Relative values for the magnitudes of the pools of labile and fixed K developed by 4 years’build‐up treatments were calculated on the basis of the model. Their relative contributions to the K taken up by a ryegrass test crop in the following year were calculated from the soil Q/I relations, and the measured uptakes of K. While the data were incomplete and so could not provide conclusive evidence for the model, the values produced were sensible and apparently consistent.
A FLOTATION METHOD FOR THE RAPID MEASUREMENT OF THE WET BULK DENSITY OF SOIL CLODS
Authors: CAMPBELL D. J.
Published: July 2006

A flotation method for the rapid measurement of the wet bulk density of soil clods is described in which the clods are sprayed with a waterproof coating of a resin and then immersed sequentially in liquids of different specific gravity. It is compared with the wax coating method for a selection of soil textures and moisture contents and shown to be ten times as rapid when used to measure wet bulk density with an accuracy of ± 0.05 g cm‐8. The flotation method was used to show that, for three contrasting soils, clod wet bulk density is independent of clod size.
SOIL STRUCTURE AND CROP YIELD
Authors: LOW A. J.
Published: July 2006

Relatively little has been published in Great Britain relating yields with quantitative assessments of the structure of soils. This paper gives examples of the kind of correlations found, a selection from many years' observations. Where the quantity of soil nutrients or disease was not a limiting factor, the yields of cereals, peas, and red beet were related to the stability of the structure which in turn depended on the number of years the soil had been out of grass.

On a soil of weak structure it was found that stabilizing, with a conditioner, the structure developed by cultivation at a moisture content below field capacity resulted in a marked increase in both yield and size grade of cauliflowers.
THERMODYNAMICS OF COBALT(I1)‐SODIUM EXCHANGE ON MONTMORILLONITE CLAY
Authors: SINGHAL J. P. , SINGH RISHI PAL
Published: July 2006

An attempt has been made to predict the mechanism of Co(I1)‐Na exchange on montmorillonite with the help of thermodynamic parameters derived from the experimental results. The exchange isotherms indicated a preference of Co ions for the clay phase, a fact in accordance with the separation factor. The reaction was accompanied by a decrease in the free energy, enthalpy, and entropy of the system revealing a tighter and more orderly structure of Co ions on the montmorillonite surface.
SOME ASPECTS OF THE HYDRODYNAMIC DISPERSION OF SOLUTES IN POROUS MATERIALS
Authors: ROSE D. A.
Published: July 2006

The paper reviews some quantitative aspects of the hydrodynamic dispersion of solute that occurs under the combined influence of molecular diffusion and convection when a solution flows through a porous material. In particular, the paper (i) describes several methods of analysing the breakthrough curve of one solution as it displaces another from‐ a column of porous material to yield a coefficient of hydrodynamic dispersion (K); (ii) discusses the form of K as a function of particle size and fluid velocity in granular beds composed of solid particles or of aggregates; (iii) discusses the effect of K on the dispersion observed in a column of porous material, as fluid velocity and particle size vary, as an aid in assessing the efficiency of leaching.
MICROBIAL POPULATIONS AND NITROGEN IN SOIL GROWING CONSECUTIVE CEREAL CROPS INFECTED WITH TAKE‐ALL
Authors: BROWN MARGARET E. , HORNBY D. , PEARSON VIVIENNE
Published: July 2006

Annually, for the past 12 years, a consecutive cereal‐cropping sequence was begun. During 1969–72 soil was collected from plots with similar fertilizer treatments, but with different sequences of crops. In 1971 and 1972 wheat seedling bioassays showed that take‐all disease became miximal after two or three crops, decreased to the fifth or sixth crop and then remained fairly constant in the‘take‐all decline’state.

The sequence with maximum disease had most NH4+ ‐N and least NO3‐ ‐N in the rhizosphere soil in spring 1972, but there were no similar relationships in bulk soil in either of 2 years. Soil and rhizoplane populations of ammonifying and denitrifying bacteria were notably smaller in autumn 1970 and 1971 in short cereal sequences (2‐5 yr.) than in the longer sequences. After γ‐irradiating or autoclaving irradiated soils, all sequences contained much NH4+ ‐N and although disease developing from added inoculum differed among soils, it did not follow the take‐all decline pattern. Diffusate from sterilized soil favoured growth of the pathogen (Gaeumannomyces graminis var. tritici) least when it originated from the sequence that supported maximum disease.
SOIL CLASSIFICATION IN THE SOIL SURVEY OF ENGLAND AND WALES
Authors: AVERY B. W.
Published: July 2006

The development of soil classification as a basis for soil mapping in England and Wales is briefly reviewed, and a system for future use is described. The things classified are soil profiles, and classes are defined by relatively permanent characteristics that can be observed or measured in the field, or inferred within limits from field examination by comparison with analysed samples. Profile classes are defined at four categorical levels by progressive division, and are termed major groups, groups, subgroups, and soil series respectively.

Classes in the three higher categories are defined partly by the composition of the soil material and partly by the presence or absence of particular diagnostic horizons, or evidence of recent alluvial origin, within specified depths. Soil series are distinguished by other characteristics, chiefly lithologic, not differentiating in higher categories. Most of the soil groups, regarded as the principal category above the soil series, are closely paralleled in other European systems, in the U.S.D.A. system (7th Approximation with subsequent amendments), or in both. Compared with the system used hitherto, the main innovations are the use of specific soil properties to define classes at all categorical levels, and the separation at group level of classes based primarily on inherited lithologic characteristics.

The soil‐profile classification provides a uniform basis for identifying soil map units, considered as classes of delineated soil bodies. When a map unit is identified by the name of a profile class, it is implied that most of the soil in each delineation conforms to that class, and that unconforming inclusions belong to one or more closely related classes or occupy an insignificant proportionate area. Map units identified by land attributes not differentiating in the profile classification are termed phases.
HUMUS TYPE DISCRIMINATION USING PATTERN RECOGNITION OF THE MASS SPECTRA OF VOLATILE PYROLYSIS PRODUCTS
Authors: BRACEWELL J. M. , ROBERTSON G. W.
Published: July 2006

Mull and mor humus can be distinguished in freely drained British surface soils by the pyrolysis products derived from whole soil samples. About i milligram of soil is pyrolysed at 770 °C in a Curie point apparatus and a sample of the volatile decomposition products is allowed to enter a low‐resolution mass spectrometer. A numerical value (the ‘Discriminator Value’) which will discriminate between the two humus types is then calculated from the spectrum of each sample. This is performed by multiplying the intensity of each mass peak by a weight factor and then summing the weighted intensities up to mass 110

The weight factors are obtained empirically by taking sets of spectra from clearly distinguished mull and mor samples and applying a computerized learning machine procedure. Once obtained, they are relatively easily applied to spectra from other soils.

The method places all samples on a numerical scale on which mull types appear positive up to about 20 × 108 and mor types negative down to about ‐15 × 103, intermediate types being recognized in about the middle of the range. It is indicated that the most important pyrolysis products active in the discrimination process are the olefin hydrocarbons, particularly ethylene, which are produced in greater abundance from mor humus.
AN ANALYSIS OF PORE SIZE IN ILLITE‐KAOLINITE MIXTURES
Authors: SILLS I. D. , AYLMORE L. A. G. , QUIRK J. P.
Published: July 2006

When API‐9 kaolinite and Willalooka illite clays were mixed in various proportions, the pore‐size distributions obtained using nitrogen sorption and mercury injection techniques were found to be characteristic of neither of the components but showed a progressive reduction in the pore size as the concentration of illite was increased. The plate separation of the mixtures showed a marked decrease with initial added illite, approaching that of the illite when the mixture contained approximately 40 per cent illite. This is indicative of a homogeneous mixture in which the fine illite particles fill in the pores bounded by the relatively coarse kaolinite particles.

The relationship between particle dimensions (derived from crystallographic parameters and specific surface area) and pore size of single clays and clay mixtures is consistent with a model in which slit‐shaped pores result from the parallel interleaving of clay crystals for the single clays. Some deviations occur for the mixtures.
CLAY MINERAL DISTRIBUTION AND ORIGIN IN THE SOIL TYPES OF ISRAEL
Authors: GAL M. , AMIEL A. J. , RAVIKOVITCH S.
Published: July 2006

The mineralogical composition of clays (< 2μm) in representative profiles of all soil types of Israel was investigated. The soils were classified according to their clay mineral assemblages into three groups.

I. Montmorillonitic soils. Montmorillonite is the dominant mineral and exceeds 65 per cent of the total minerals found; each of the other minerals comprises less than 15 per cent.

2. Montmorillonitic‐kaolinitic soils. The soil clay fractions contain 50‐60 per cent montmorillonite and 15‐25 per cent kaolinite, generally adding up to more than 75 per cent of the clay fraction.

3. Montmorillonitic‐calcitic soils. The clays contain more than 10 per cent calcite. Montmorillonite is the dominant clay mineral (except for one soil type, mountain rendzina, where calcite is dominant).

The first and second assemblages are typical of the soils of the Mediterranean zone, whereas the soils of the desert zone are characterized by the third assemblage.

The origin of montmorillonite, kaolinite, and illite, the three main clay minerals, was found to be detritic, as was the origin of palygorskite which was mainly found in the calcite rich soils of the desert zone.

The cation exchange capacity of montmorillonite seems to be higher under higher precipitation. Montmorillonite content and cation exchange capacity of the clays were found to be highly correlated. The carbonate content of the clay fraction and the amount of carbonate in the soil were also highly correlated.
TIME DEPENDENCE OF COMPRESSIBILITY FOR REMOULDED AND UNDISTURBED SOILS
Authors: DEXTER A. R. , TANNER D. W.
Published: July 2006

Remoulded soils compress more rapidly than undisturbed soils at the same initial density and water content. Soils with larger particles compress more rapidly than those with smaller particles. Soils compress more slowly when they are more densely packed. Soils expand more slowly than they compress between the same two pressures.

Implications of these results are that soils which are not tilled would be less susceptible to compaction, and that tractors and other vehicles would cause less compaction when travelling at higher speeds.
THE COVARIANCE OF PHOSPHATE SORPTION WITH OTHER SOIL PROPERTIES IN SOME BRITISH AND TROPICAL SOILS
Authors: LOPEZ‐HERNANDEZ DANILO , BURNHAM C. P.
Published: July 2006

Phosphate sorption capacity estimated by Piper's (1942) ‘anion exchange capacity’ and Bache and Williams's (1971) phosphate sorption index were correlated with soil pH, clay, organic matter, ‘free iron oxides’ and ‘extractable aluminium’ (McLean et al., 1958) for topsoil and subsoil samples from twenty tropical and twenty British acidic soil profiles. These two groups of soils did not differ significantly in phosphate sorption. Extractable aluminium and free iron oxide were well correlated with phosphate sorption, free iron oxide being superior to aluminium in freely drained British soils but not in poorly drained ones. Organic matter content correlated well with phosphate sorption for the poorly drained British soils, and for the tropical soils when sorption capacitywas measured using a high phosphate concentration.
THE REMOVAL OF ORGANIC MATTER FROM SOIL EXTRACTS BY BROMINE OXIDATION
Authors: MITCHELL B. D. , SMITH B. F. L.
Published: July 2006

Brown‐coloured extracts are frequently obtained when chemical dissolution techniques are applied to soils. The colour, arising from the presence of organic material, interferes in subsequent spectrophotometric determinations of extractable inorganic components. A bromine oxidation method for the complete removal of interfering organic matter has been devised. This involves the oxidation of the organic matter with alkaline bromine solution and the subsequent removal of excess bromine by acid and heat treatment. To test the effectiveness of the method extracts from chemical dissolution procedures, containing organic matter, were examined before and after bromine treatment by ultra‐violet and infra‐red adsorption and mass spectrometric techniques.
FULVIC ACID. II. INTERACTION WITH METAL IONS
Authors: MacCARTHY PATRICK , O'CINNEIDE S.
Published: July 2006

Evidence is presented, based on sequestration, chemical behaviour, ultra‐violet and infra‐red spectroscopy, to indicate the formation between the non‐cationic fraction of fulvic acid and a variety of transition metal ions, of stable soluble complexes and also of insoluble complexes over the complete pH range. The soluble complexes formed under alkaline conditions are negatively charged. The fulvic material is very effective in competing with other ligands for the metal ions. Mechanisms for the flocculation of the soil organic matter in the presence of heavy metal ions are discussed. The formation of inert complexes between cobalt and the fulvic material is also demonstrated and its implications to the study of metallo‐organic complexes are discussed.
ANNUAL SOIL MOISTURE REGIMES IN THE ROOTING ZONE ACROSS THE PRAIRIE‐FOREST BOUNDARY OF SOUTH‐WEST ALBERTA
Authors: HARRIS STUART A.
Published: July 2006

Vegetation cover is shown to play a major role in determining the soil moisture content in the Front Range of the Rocky Mountains near Calgary. Thus lodge‐pole pine abstracts more moisture from the soil both in summer and winter than aspen, while least moisture loss is experienced on bare soil. Clearly vegetation cover must be kept constant when comparing two soils. Additional important variables are aspect and parent material. It was also found that permanent (IS bar) wilting‐point, as commonly used, bears little relation to the permanent wilting‐point of even the more moisture‐loving native trees studied. They all do not wilt until a much lower moisture content is reached.
THE INFLUENCE OF ORGANIC MATTER, CHALK, AND SESQUIOXIDES ON THE SOLUBILITY OF IODIDE, ELEMENTAL IODINE, AND IODATE INCUBATED WITH SOIL
Authors: WHITEHEAD D. C.
Published: July 2006

Iodine in each of the forms iodide, elemental iodine, and iodate was added, at a rate of 5 mg/kg to a sandy loam and to mixtures of the soil with composted grass roots, chalk and sesquixoides, and its solubility determined after various periods of incubation.

With iodide, solubility in both 0.01 M CaCl2 and 1.0 M NK4 acetate (pH 4.8) declined rapidly over the period o to 3 days and subsequently reached approximate equilibrium levels of 2.8 per cent solubility in CaCl2 and 7.8 per cent in NH4 acetate, these values being the means of samples incubated for 48, 103, and 160 days. The partial (5 per cent) replacement of the soil by composted grass roots had no appreciable effect on the solubility of added iodide, while chalk, incorporated at a rate of 5 per cent, depressed the solubility of iodide in CaCl2 to 1.8 per cent but caused a slight increase in solubility in NH4 acetate. The incorporation of 2 per cent hydrated ferric oxide or of 2 per cent hydrated aluminium oxide reduced the solubility of iodide in CaCl2 to 0.1 and 0.3 per cent, and in NH4, acetate to 3.8 and 5.7 per cent respectively. Elemental iodine was similar to iodide in its solubility in the two extractants and in its response to the various soil treatments. Iodate, however, differed considerably from the other two forms of iodine. With soil alone, and with the soil/chalk mixture, its decline in solubility with increasing incubation time was relatively slow, although after 160 days its solubility was similar to that of iodide and elemental iodine. The incorporation of composted grass roots caused a rapid reduction in iodate solubility, suggesting that the organic matter accelerated the reduction of iodate to elemental iodine or iodide. With the treatments involving the incorporation of ferric and aluminium oxides, there appeared to be considerable sorption of iodate during the 16 h extraction period and the effects of these materials on iodate solubility during incubation were therefore difficult to assess.
THE EFFECT OF THE EVAPORATION OF ENTRAINED LIQUID ON SOIL FABRIC
Authors: GALLAVAN R. C. , GREENE–KELLY R.
Published: July 2006

The evaporation of polyethylene glycol zoo from three remoulded clay soils and a clay aerogel was observed by scanning–electron and incident‐light microscopy. Neither flexing of the fabric during recession of the liquid film, nor reorganization of clay domains during shrinkage, was detected.
WELL–POINT TECHNIQUES AND THE SHALLOW WATER TABLE IN BOULDER CLAY
Authors: VISVALINGAM M.
Published: July 2006

The reliability of water‐table measurements in clay soil is currently under review (Twocock, 1971; Bonell, 1971; Visvalingam, 1972). This paper summarizes some of the experimental results from a boulder clay catchment in East Yorkshire. The experiments investigated the functioning characteristics of cased auger holes and piezometers in clay soil and compared the results with observations made with a neutron moisture probe. It appears that well‐point technique, especially piezometers, are extremely unreliable in clay soil. The measured water level is demonstrated to be influenced by not only the position of the ‘water table’ but also the permeability of the soil; in which context the type, diameter, and length of tubing, as well as the time of installation, become important considerations.
ZINC ADSORPTION AND DIFFUSION IN GOETHITE PASTES
Authors: BAR‐YOSEF B. , POSNER A. M. , QUIRK J. P.
Published: July 2006

Zinc diffusion in goethite (α‐FeOOH) was examined theoretically and experimentally. Concentration profiles of zinc diffusion after various periods of time were determined in physically and chemically defined oxide pastes using a tracer technique. Apparent diffusion coefficients were calculated as a function of diffusible zinc concentration from these results and compared with values obtained indirectly from slopes of adsorption isotherms and experimentally determined impedance factors of the conducting media. To deal with a wide range of experimental conditions, a model for calculating zinc adsorption was applied and evaluated. Changes in pH across the diffusion profile due to zinc transport were postulated to account for some of the results. Where these effects were minimal, the agreement between the diffusion coefficients obtained by the direct and indirect methods was satisfactory. The contribution of surface diffusion to the total transport of zinc in the goethite paste was estimated to be very small.
HUMUS TYPE DISCRIMINATION FROM MASS SPECTRA BY A SIMPLIFIED STATISTICAL TREATMENT
Authors: BRACEWELL J. M. , ROBERTSON G. W. , STEPHEN G. J. M.
Published: July 2006

The calculation of a discriminator between mull and mor humus types from the mass spectra of soil pyrolysis products, described earlier by Bracewell and Robertson (1973), used IIO normalized peak heights; these can be reduced to thirteen and the calculation simplified. Assumption of class for some soils, which was necessary in the previous method of obtaining the pattern classifier, has been obviated by the use of principal components analysis.
PRECIPITATION OF AMORPHOUS ALUMINOSILICATES FROM SOLUTIONS CONTAINING MONOMERIC SILICA AND ALUMINIUM IONS
Authors: WADA KOJI , KUBO HIROSHI
Published: July 2006

Monomeric silica solutions were mixed with solutions containing AlCl3, or Al(OH)2‐55Cl0‐45 to give a SiO2/Al2O3, ratio varying from 8 to 8.0 and were kept at pH 6–0, 7.0, or 8.0 over a period of about I year. All precipitates which formed from solutions with SiO2/Al2O3 ratios of 1–0 or higher were X‐ray amorphous. The SiO2/Al2O2, ratio of the precipitate varied in the range from 1.0 to 3.0. It increased with the Si concentration and the SiO2/Al2O3 ratio of the parent solution and with reaction time. The pH did not affect the SiO2/Al2O3 ratio of the precipitate but did affect its dispersion and flocculation. Al3+ and Al(OH)2.55+0.45 reacted differently with silica and yielded different reaction products. These differences were interpreted in terms of the stability of hydroxy‐Al polymer units in the reaction. The amount of NaOH per Al atom which was required to reach and maintain the same pH, increased with the increasing SiO2/A12O ratio of the precipitate, but the value was generally lower than that predicted from ‘one in four’ substitution of Si by Al in four‐fold co‐ordination. A ‘neutralization’ of the positive charge on the hydroxy‐Al cations by silica was pointed out also to be a cause of the extra acidity. Implications of these observations on synthetic amorphous aluminosilicates to the genesis, structure, and properties of their natural counterparts were discussed.
LIQUID LIMIT DETERMINATION OF ARABLE TOPSOILS USING A DROP‐CONE PENETROMETER
Authors: CAMPBELL D. J.
Published: July 2006

The drop‐cone method, in which a 30° cone of mass 80 g is allowed to sink into a soil sample at a selection of moisture contents, is described and examined as a possible alternative to the Casagrande device for liquid limit determination. The methods are compared for 13 arable topsoils. The drop‐cone method, which uses apparatus that is readily available commercially, is shown to have advantages in ease of conduct of the test and in greatly improved reproducibility between operators.
SOIL GENESIS IN RELATION TO GROUNDWATER AND SOIL MOISTURE REGIMES NEAR VEGREVILLE, ALBERTA1
Authors: MACLEAN A. H. , PAWLUK S.
Published: July 2006

The study was designed to obtain information on flow and salinity of the groundwater, and on moisture regimes above the water table at selected sites near Vegreville, Alberta, and to relate this information to features of soil genesis revealed by soil mapping and analysis. All soils on the lower slopes, unlike those at upper elevations, contained accumulations of salts and gypsum, but the depth of salt accumulation and therefore the kind of soil appeared to be related only partly to current groundwater flow directions and the depth of the water table. The sodium content of the discharging groundwater and past flow conditions also appeared to be important. Lateral flow above the water table is suggested as being of possible importance in desalinization of surface horizons.
QUANTITATIVE PEDOLOGICAL STUDIES ON SOILS DERIVED FROM SILURIAN MUDSTONES
Authors: EVANS L. J. , ADAMS W. A.
Published: July 2006

Using the acid‐resistant residue of soil fine earth as internal standard, the redistribution and losses of SiO2, Al2O3, MgO, K2O, Na2O, and TiO2 were determined for an upland developmental sequence of five profiles on Silurian scree. The mobilization of Al, Fe, and Mg was related to chlorite breakdown. Of these constituents Fe began to be released at an early stage of weathering whereas A1 release lagged behind Fe and Mg; although substantial amounts of Fe and A1 were mobilized in highly weathered horizons. Subsequently, whereas mobilized Fe was almost completely redeposited in illuvial horizons, little of the mobilized A1 was retained by the soils. Amounts of Fe and A1 extracted by 0.1M potassium pyrophosphate were compared with redistribution computed using the internal standard. The concentrations in drainage water of soil constituents mobilized during pedogenesis were estimated and compared with measured concentrations in stream water draining the catchment.
SIMULATION OF THE WATER BALANCE OF SOIL COLUMNS AND FALLOW SOILS
Authors: ROWSE H. R.
Published: July 2006

A model is described that predicts the evaporation of water from, and the distribution of water in, a soil column evaporating into a constant environment. It is based on a numerical solution of the flow equation and requires only the initial water distribution in the column, the equilibrium (air‐dry) water content at the soil surface and the relationship between volumetric water content and diffusivity. The model predictions show good agreement with a published analytical solution and with experimental results.

Modifications to the model that allow for rewetting of the sod by rainfall, and changes in atmospheric conditions above the soil, enable predictions to be made of the water balance of a fallow field. In general, good agreement was obtained with the measured distribution of water deficits in the soil profile, although the predicted water content of the surface 2.5 cm of soil showed systematic differences from the measured values. The reasons for this are discussed.
THE EFFECT OF PARTICLE MORPHOLOGY ON THE K‐Ca EXCHANGE PROPERTIES OF MONTMORILLONITE
Authors: LEE R. , ROWELL D. L.
Published: July 2006

Adsorption isotherms for K on to Ca montmorillonite (< 2 μm and < 0.1 μm. e.s.d. fractions) at ionic strengths from 3 × 10−2M to 3 × 10−5M have been analysed by the methods of Van Bladel and Laudelout (1967) and show that negatively charged sites in the lamellae of both size fractions are the same but when these lamellae are intermeshed in crystals, potassium is favoured, probably in wedge sites between adjacent lamellae. The effectiveness of these wedge sites is lost at zero ionic strength.
SCANNING ELECTRON MICROSCOPE STUDIES OF A SURFACE WATER GLEY
Authors: MCHARDY W. J. , BIRNIE A. C.
Published: July 2006

Specific features of a gley soil developed on varved lacustrine clay have been studied by scanning electron microscopy and electron probe microanalysis. Individual clay platelets can be clearly observed in the red‐brown parent material but they cannot be resolved in the gleyed surfaces which have a smooth skin‐like texture. Ochreous mottles are shown to have a porous blocky structure, the surfaces of the blocks being coated with globular iron oxide. Areas of manganese staining have a characteristic sponge‐like morphology.
REACTIONS BETWEEN METALS AND HUMIFIED ORGANIC MATTER
Authors: BLOOMFIELD C. , KELSO W. I. , PRUDEN G.
Published: July 2006

We studied the properties of the soluble and dispersed compounds of Cu, Mn, Co, Ni, Pb, Zn, and Cd formed by the action of aerobically decomposing plant matter on the respective metal oxides. The metals were mobilized partly in association with colloidal humified organic matter, and partly in true solution as complexes that seemed to be anionic.

In the presence of a clay soil there was no net mobilization of colloidally bound Cu, but the dialysable Cu complex was not appreciably sorbed by the mineral colloids and was leached from the reaction mixture.

The metals were not precipitated under alkaline conditions from the dialysable complex forms. Material with similar complexing properties was found in the dialysable fractions of a soil organic matter extract, of water squeezed from a raw peat, and of laboratory lysimeter solutions from a podzol under Calluna.

Below about pH 6 the exchange of Cu on a soil clay was not affected by the presence of colloidal decomposition products of lucerne. With Co, Ni, and Zn the corresponding pH value was about 4, and the critical value for Cu in the presence of colloidal soil organic matter was also about 4. Below these values the metal and organic matter sorption curves were diametrically opposed so that under these conditions Cu is apparently not strongly bonded to colloidal organic matter.
THE EFFECT OF TEMPERATURE ON THE MICROBIAL TRANSFORMATION OF [14C] GLUCOSE DURING INCUBATION IN SOIL
Authors: CHESHIRE M. V. , GREAVES M. P. , MUNDIE C. M.
Published: July 2006

When two different soils were incubated after the addition of [14C] glucose in the dark at winter temperatures or at 5°C in the laboratory and then hydrolysed, radioactivity was detected in all seven common soil sugars except arabinose. In contrast, in incubations at 20°C, little radioactivity was found in the xylose. Examination of the microflora showed that the number of viable bacteria was one‐tenth at the lower temperatures, whereas the numbers of yeasts, fungi, and actinomycetes were unaffected. Analysis of cultures of representative microbial isolates showed that none of the fungi or actinomycetes and only 3 per cent of the bacteria synthesized xylose, compared with 85 per cent of the yeasts.

It is concluded that when these soils are incubated at low temperatures xylose is synthesized principally by yeasts.
A MATHEMATICAL MODEL FOR THE DIFFERENTIAL MOVEMENT OF TWO SOIL CONSTITUENTS INTO ILLUVIAL HORIZONS: APPLICATION TO CLAY RATIOS IN ARGILLIC HORIZONS
Authors: VAN WAMBEKE A.
Published: July 2006

The effects of the migration of two soil constituents into illuvial horizons is described by a set of equations. Differential movement of clay fractions during illuviation causes changes in the fine to total clay ratios in A and B horizons.

A mathematical model is used for the interpretation of clay fraction data in order to estimate the degree of profile development, the amounts of fine and total clay which have moved, and to determine the original composition of the parent material. No bulk density data of the soil horizons are necessary for the computation.

The equations can be programmed on desk calculators. Comparison with measurements on Alfisols in temperate regions was found to be satisfactory.
THE TEMPERATURE OF THE SOIL UNDER A BARLEY CROP
Authors: HAY R. K. M.
Published: July 2006

Continuous records of soil temperature were collected at 1, 5, and 20 cm depth, throughout the growing season, under crops of barley in the east of Scotland. The values obtained were considerably lower than the temperatures normally employed in laboratory studies of temperate cereal roots. The resulting hazards in extrapolating from the laboratory to the field are briefly discussed.
EFFECTS OF CALCIUM CARBONATE ON THE SWELLING BEHAVIOUR OF A SOIL CLAY
Authors: RIMMER D. L. , GREENLAND D. J.
Published: July 2006

Measurements of the swelling behaviour of a soil clay, in both Ca‐ and Na‐saturated forms, before and after removal of calcium carbonate have been made. For the Ca‐clays, three suctions were used, 10·0 mbar, 63·1 bar, and 1·59 kbar. There were no significant differences in the swelling before and after carbonate removal at 1·59 kbar. At 63·1 bar, removal of carbonate led to decreases in swelling for all samples. At 10 mbar suction, removal led to increases in swelling for samples initially with > 1 per cent carbonate and to decreases for samples with < 1 per cent. For the Na‐clays, only 10mbar suction was used and similar results to those for Ca‐clays were obtained, except that the swelling was greater and the differences larger. The effect of varying the electrolyte concentration on the swelling behaviour of the Na‐clays was also studied. The swelling data can be partly explained in terms of the suppression of diffuse layer formation when calcium carbonate was present. Surface area determinations before and after decalcification led to the conclusion that the carbonate was also acting as a cement. The decrease in swelling after carbonate removal, for all samples at 63·1 bar suction, and for samples initially low in carbonate at 10 mbar suction, is thought to be due to the mobilization and redeposition of hydroxy‐alumina polymers during the treatment.
SOLUBLE POLYMERIC HYDROXY‐ALUMINIUM IONS IN ACID SOILS
Authors: BACHE B. W. , SHARP G. S.
Published: July 2006

Solution concentrations of total Al and of mononuclear Al ions were determined as a function of pH for two acid soils. Polynuclear hydroxy‐Al was taken as the difference between total and mononuclear Al. Salt concentration at 1 : 5 soil: solution ratio was varied from 0·008 to 1·o equiv/l, for CaCl2, KCl, and NH4OAc at pH 4·8. Polynuclear hydroxy‐Al concentrations increased with electrolyte concentration and the valency of the desorbing cation, and rose to 0·2 mM (equivalent to 3 meq/kg soil) in unbuffered salt suspensions, and to 1·0 mM in NH4OAc at pH 4·8. Polynuclear hydroxy‐Al thus behaves like a normal exchangeable cation. I.0M NH4OAc released much more total A1 from some of the more acid samples than might have been expected from its pH of 4·8.
DECOMPOSITION OF ORGANIC MATTER ON THE FOREST FLOOR OF PINUS RADIATA PLANTATIONS
Authors: LAMB D.
Published: July 2006

Laboratory experiments were carried out on the relative decomposition of litters collected from stands with contrasting accumulations of organic matter on the forest floor. Decomposition was measured by the weight loss of sterile litters inoculated with Pholiota and Lenzites, and by the microbial respiration in non sterile litters.

Some differences were measured in litters from stands with dissimilar ages and productivities. The most striking differences in decomposition were those observed in litters from older stands (assumed to be in a steady state condition) of the same age and productivity class but on different soil types. These differences matched the patterns of relative litter accumulations in these stands in the field. The variations found in P. radiata litter decomposition were attributed to nutritionally induced differences in polyphenol complexing of litter materials.
OXYGEN UPTAKE AND RESPIRATORY QUOTIENT OF FIELD SOIL CORES IN RELATION TO THEIR AIR‐FILLED PORE SPACE
Authors: BRIDGE B. J. , RIXONZ A. J.
Published: July 2006

The oxygen uptake and respiratory quotient (RQ) of field cores from three soils of different texture classes were studied using electrolytic respirometers. Critical values of air‐filled pore space (f), above which RQ was always near unity, that is, corresponding to the transition from anaerobic to aerobic respiration, were defined for each soil. These critical values agreed with minimum values off required for plant growth as reported in the literature, suggesting that RQ can be used as an index of adequate soil aeration.

Oxygen uptake by the three soils reached a maximum at f values slightly above the critical values, corresponding to the highest moisture content at which oxygen diffusion was non‐limiting.
EFFECT OF ARTIFICIAL WEATHERING CYCLES ON THE STRUCTURAL STABILITY OF A DISPERSED SILT SOIL
Authors: RICHARDSON S. J.
Published: July 2006

A very fine sandy loam soil was severely puddled in the laboratory and subjected to varying numbers of freeze/thaw‐wet/dry cycles in an attempt to restore its original level of structural stability. After only three cycles the stability of the treated soil reached its maximum value, which was slightly greater than that of untreated soil collected from the field. A higher level of soil organic matter was accompanied by an increase in structural stability as determined by the dispersion ratio technique and a technique involving partial dispersion in Calgon.
ADSORPTION OF PHOSPHATE BY GIBBSITE
Authors: HELYAR K. R. , MUNNS D. N. , BURAU R. G.
Published: July 2006

The effects of the nitrate salts of zinc, cadmium, and strontium on the adsorption of phosphate by gibbsite have been measured at pH 5.5 and 25° C. At solution phosphate concentrations greater than 10 μM strontium and cadmium increased phosphate adsorption whilst zinc had no effect. At lower phosphate concentrations zinc and cadmium increased adsorption of phosphate in a different manner from strontium, sodium, potassium, magnesium, or calcium. Zinc and cadmium at 1 mM concentration inhibited phosphate adsorption, perhaps because they are specifically adsorbed as indicated by pH‐shift data.

A postulated surface complex consists of two adjacent adsorbed phosphate ions and a central divalent cation of appropriate size, charge, and possible co‐ordinating properties.
EFFECT OF pH ON THE REACTION OF SODIUM FLUORIDE WITH HYDROUS OXIDES OF SILICON, ALUMINIUM, AND IRON, AND WITH POORLY ORDERED ALUMINOSILICATES
Authors: PERROTT K. W. , SMITH B. F. L. , MITCHELL B. D.
Published: July 2006

The release of hydroxyl ions from silica and ferric oxide gels on treatment with sodium fluoride solution is very small above pH values of 7.6 and 9 respectively. Hydroxyl release from alumina gel and poorly ordered aluminosilicates is appreciable at pH 9 and varies little with pH, but that from crystalline forms of alumina decreases with decrease of pH. For poorly ordered aluminosilicates, the ratio (OH′ released at pH 8.0): (OH′ released at pH 6.8) is directly proportional to the mole fraction Al/(Al+Si). The measurement of hydroxyl release at differing pH values may enable determination of hydrous alumina separately from the total poorly ordered inorganic gel material; moreover, the amount of hydroxyl released at high pH values is related to phosphate sorption capacity.
THE CATEGORIES OF ALUMINIUM‐ AND IRON‐HUMUS COMPLEXES IN ANDO SOILS DETERMINED BY SELECTIVE DISSOLUTION
Authors: WADA KOJI , HIGASHI TERUO
Published: July 2006

Thirty‐three samples of Ando soils were extracted by sodium pyrophosphate (O.IM; pH 10) and by dithionite‐citrate. The Al, Fe, and C contents of these two extracts offer a means of differentiating the status of humus in relation to Al and Fe in the different horizons. The humus that forms at first in the Al horizon has a very low complexing ability for Al and Fe and little is dissolved by pyrophosphate. The humus evolves with time or pedogenesis into forms that complex Al and Fe released from volcanic ash by weathering, and which are dissolved by pyrophosphate. In the old horizons, the humus further reacts with additional Al and Fe, some of which may be present as hydrous oxides or allophane‐like constituents, allophane and imogolite. This reaction probably makes the humus less soluble in pyrophosphate.
SOME EFFECTS OF MOUND‐BUILDING TERMITES ON SOILS IN UGANDA
Authors: POMEROY D. E.
Published: July 2006

Most large mounds in Uganda are built by termites of the genus Macrotermes. Except for those in valley bottoms they are composed of subsoil which is thought to be collected mainly from depths of 0.5 to 1.0 m, although the evidence is inconclusive. Mounds of both M. bellicosus and M. subhyalinus contain less sand than the subsoil when this is sandy, but only M. subhyalinus mounds contain less clay when the subsoil has a high clay content. In general both species tend to produce a stone‐free topsoil whose physical properties are closer to a loam than the average subsoil. Mounds of both species in valley bottoms appear to be built from topsoil.

The amounts of organic matter, nitrogen, calcium, phosphorus, and potassium in mounds were estimated together with their rates of turnover. In terms of the demands of two typical crop plants the quantities held in mounds and their rate of release to the surrounding topsoil were small. Only calcium was likely to be cycled in significant amounts.

It seems that termites only slightly affect the physical and chemical properties of Ugandan soils, even where mounds are comparatively abundant.
VARIABILITY IN THREE AREAS OF THE DENCHWORTH SOIL MAP UNIT.
Authors: BASCOMB C. L. , JARVIS M. G.
Published: July 2006

Variability of soil within three areas of the Denchworth map unit in southern England Has been investigated by describing and analysing samples from thirty profiles located at the intersects of a randomly oriented grid.

The Denchworth series has been mapped over several stratigraphically different clays, and the areas chosen provide three groups of profiles developed over Gault (Cretaceous), Kimmeridge, and Oxford (Jurassic) Clay respectively.

Purity of the map unit, estimated as the percentage of profiles whose data agree with the definition of the Denchworth series, was 60 per cent, which is comparable with values for other map units both near by and elsewhere.

The variability of individual properties as indicated by coefficients of variation differed widely. Generally, physical properties were more uniform than chemical properties. The Denchworth map unit can consequently be treated uniformly for aspects of land management related to soil physical properties but it provides little guidance for fertilizer application.

A small amount of variability can be attributed to mapping together those soils developed in material derived from stratigraphically different clays, but is insufficient to justify separating them.
TOWARDS AN ABSOLUTE MEASUREMENT OF SOIL STRUCTURAL STABILITY USING ULTRASOUND
Authors: NORTH P. F.
Published: July 2006

Calibrations enabled controlled application of a range of known dispersive energies to a selected soil sample. The corresponding levels of dispersion were measured in terms of the weight fraction of particles <2 μm equivalent spherical diameter produced, and are used to define a dispersion characteristic for the test soil.

Interpretation of this characteristic in terms of a microaggregate theory provides the energy value associated with complete ‘primary dispersion’ of microaggregates, which under normal field conditions is a direct practical measure of soil stability. This leads to a definition of the specific stability index (σ) of a soil which for the gleyed brown earth used in this work has the value (25±3) J g−1.
THE ASYMMETRIC LEACHING PATTERN OF NITRATE AND CHLORIDE IN A LOAMY SAND UNDER FIELD CONDITIONS
Authors: WILD A. , BABIKER I. A.
Published: July 2006

In a field experiment on a weakly structured, almost stone‐free loamy sand, the depths of leaching of chloride and nitrate were measured after sprinkler irrigation at 8 mm/h. The modal depth of movement of the two ions was about half the mean depth of movement, indicating a highly skewed distribution and a pronounced leading tail of chloride and nitrate. The marked asymmetry of the salt distribution is attributed to uneven downward movement of water, including movement down earthworm channels, which results in part of the nitrate and chloride being deeply leached.
SELECTIVE EXTRACTION OF AMORPHOUS IRON OXIDE BY EDTA FROM A MIXTURE OF AMORPHOUS IRON OXIDE, GOETHITE, AND HEMATITE
Authors: BORGGAARD O. K.
Published: July 2006

Iron (III) was extracted by EDTA and ammonium oxalate from a model substance consisting of amorphous iron oxide, goethite, and hematite precipitated in the presence of quartz sand. Even by varying the EDTA concentration between 0.02 and 0.1 M, pH between 4.40 and 6.00, the solid:solution ratio between I:25 and I:250, and using extraction times up to go days, it was found that EDTA was able to extract only a limited amount of iron. In contrast, 0.2 M ammonium oxalate at pH 3.0 is able to dissolve all the iron compounds if the extraction time is sufficient. Nevertheless, the amount of EDTA‐extractable iron is equal to the amount of iron extracted after 4–5 hours with ammonium oxalateat pH 3.0.

From X‐ray analysis, DTA curves, a solubility product determination, and a kinetic investigation, it is concluded that the EDTA‐extractable fraction consists of X‐ray amorphous iron oxide, less soluble than polymeric iron hydroxide, and presumably only one compound.

Therefore, it is concluded that it may be possible by means of EDTA to carry out a selective extraction of X‐ray amorphous iron oxides mixed with goethite and hematite.
THE COMPOSITION OF MOUNDS OF THE TERMITE MACROTERMES FALCIGER (GERSTACKER) ON SOIL DERIVED FROM GRANITE IN THREE RAINFALL ZONES OF RHODESIA
Authors: WATSON J. P.
Published: July 2006

Thirty‐eight termite mounds (about 1.6 m high and 7.6 m basal diameter) and the same number of adjacent soils were sampled in three rainfall zones: low (below 700 mm annual rainfall), medium (700 to 1000 mm annual rainfall), and high (above 1000 mm annual rainfall). Higher amounts of clay, silt, and fine sand, and lower amounts of coarse sand occurred in termite mounds than in adjacent soils of all rainfall zones. Extractable cations (Ca, Mg, and K), calcium carbonate, pH, electrical conductivity, and organic carbon were also higher in termite mounds than adjacent soils of all rainfall zones.

Wide differences in extractable calcium between termite mounds and adjacent soils of low and medium rainfall zones indicated weak leaching of termite mounds; narrow differences in the high rainfall zone indicated strong leaching of the mounds.

The ‘umbrella effect’ of termite mounds in shedding rainfall and retarding leaching is clearly displayed in the medium rainfall zone where high concentrations of extractable calcium in termite mounds and low concentrations in adjacent soils indicate weak and strong leaching respectively.
EFFECT OF SOIL pH AND ORGANIC MATTER ON LABILE ALUMINIUM IN SOILS UNDER PERMANENT GRASS
Authors: CABRERA F. , TALIBUDEEN O.
Published: July 2006

The rates of extraction of Na, K, Mg, Ca, and Al with 1M NH4 NO3 from the mineral‐and organic‐rich layers of some Park Grass (Rothamsted) soils were measured at the pH of the soil. Below pH 3.7 exchangeable Al, derived from the kinetics curve, increases with decreasing soil pH and is less in the organic‐rich layer. The sum of the basic exchangeable cations, ∑(Na + K + Mg + Ca), increases with increasing soil pH and is more in the organic‐rich layer.

The extraction of exchangeable Al obeys first order kinetics, the rate constant being similar for all the soils (mean value 36 ± 7 × 10−6|s−1), which implies that exchangeable Al is released from surfaces with similar properties for the adsorption of Al, and that the rate is not affected by soil pH and organic matter. The rate of extraction of non‐exchangeable Al is the same in the mineral‐and organic‐rich layers of each soil, and is maximal at about pH 3.7, decreasing sharply at more and less acid pH values.
CONCENTRATIONS AND ACTIVITIES OF IONS IN SOLUTIONS DISPLACED FROM BASALTIC SOILS
Authors: BENIANS G. , SCULLION P. , FITZHUGH G. R.
Published: July 2006

Soil solutions displaced from Antrim basaltic soils were analysed for major inorganic constituents. The solutions were nearly saturated with aluminium and phosphate but not sulphate. Iron concentrations were greatly in excess of ferric hydroxide solubility. The solutions were less concentrated than those described for soils of Britain and the U.S.A., representing a leaching environment.
PEAT WASTAGE IN THE EAST ANGLIAN FENS
Authors: RICHARDSON S. J. , SMITH J.
Published: July 2006

Measurements of the decline in peat depth between 1941 and 1971 were taken at 14 sites across the East Anglian Fens. Rates of wastage in the period before 1955 and in the more recent period varied widely from site to site. Wastage rates were higher at all sites but one, in the period before 1955. The mean value for wastage rate over the entire period covered was 1.37 (± 0.78) cm/yr.
WEATHERING STAGES OF THE COMMON IGNEOUS ROCKS, INDEX MINERALS AND MINERAL ASSEMBLAGES AT THE SURFACE OF THE EARTH
Authors: CHESWORTH WARD
Published: July 2006

The system SiO2 ‐AlOOH‐Fe2 O3 ‐H2 O is used to show certain short‐comings in the use of single minerals to index weathering stages. An alternative (analogous to the metamorphic facies concept) is proposed in which three stages are recognized, one of which can already be defined in terms of mineral assemblages, while the two earlier stages should eventually prove open to this treatment.