bluuebunny/crossref_metadata_2025 huggingface dataset:
THE MECHANISM OF PHOSPHATE ADSORPTION BY KAOLINITE, GIBBSITE, AND PSEUDOBOEHMITE
Authors: MULJADI D. , POSNER A. M. , QUIRK J. P.
Published: July 2006

The adsorption isotherms of phosphate have been determined at pH 5 on K‐kaolinite, gibbsite, and pseudoboehmite at 2° and 40°C, and compared with those already determined at 20°C. The extent of adsorption increases with temperature, largely because of an irreversible increase in the number of adsorption sites.

The shape of the isotherms remains essentially the same, indicating that the heat of adsorption is small, and that the driving force for phosphate adsorption is largely entropic. This was confirmed by calorimetric measurements.

It is suggested that, when phosphate is adsorbed, there is an increase in the entropy of the water surrounding the phosphate ion and the adsorption site.
CERTAIN EQUILIBRIUM ION RATIOS FOR A SOLONETZIC SOIL
Authors: KHAN S. U. , WEBSTER G. R.
Published: July 2006

A method is described for determining the true equilibrium soil solution for a saline soil adjusted to various moisture contents by interpolation of ion ratios in solution before and after equilibration. Over the moisture range studied, equilibrium values were different at each moisture content. The ionic strengths of the equilibrium solutions were considered to be too high for calculation of activity coefficient and therefore concentration ratios were used instead of activity ratios. The ionic strength and ion ratios for the soil equilibrium solutions changed gradually over the moisture range 35 to 100 per cent, but abruptly over the lower moisture range (5 to 35 per cent). The expression log(Na)–½ log(Ca) is regarded as being particularly important.
ELECTRIC CHARGES OF CLAYS
Authors: CASHEN G. H.
Published: July 2006

Conductimetric titrations, with NaOH, of solutions containing Al ion detect two OH‐ions of Al in the acid range, with OH/Al ratios of ions such as Al(OH)2+ and A16(OH)3+15; in the alkaline range aluminate Al(OH)−14 is formed. Similar titrations of an Al‐kaolin, prepared by acid washing, give results that can be adequately interpreted in terms of these three ions, i.e. by the reaction with alkali of Al3+ ions balancing the permanent isomorphous replacement charge. If there are reactions with alkali at the edge‐faces of the kaolin, e.g. the neutralization of residual positive edge‐charge, these edge‐charges must be small in comparison with the permanent charge. Bonding by the complex ion Al6(OH)3+15, formed on the surfaces of clay particles, explains why the viscosity of Al clays is greatest at the five‐sixths stage of neutralization, because the formation of the hydroxide Al(OH)3 is theoretically equivalent to the measurement of the permanent charge.
QUANTITATIVE DETERMINATION OF CALCITE AND DOLOMITE IN PURE CARBONATES AND LIMESTONES
Authors: PETERSEN G. W. , CHESTERS G.
Published: July 2006

Calcite and dolomite were differentiated quantitatively from calcite‐dolomite mixtures and limestones by a method based on the quantitative dissolution of calcite in pH 5.85N citrate buffer. The acidity and chelating ability of citrate favoured greatly the dissolution of calcite to that of dolomite. The method consisted of determination of citrate‐soluble Ca and Mg which, in conjunction with a Ca and Mg analysis of the residue, or a determination of total CO3 in the system, allowed calculation of the calcite and dolomite contents of the sample.

Analyses of artificially prepared mixtures and limestone samples gave essentially the same calcite and dolomite contents when determined by the residue and total CO3 methods. The residue method is to be preferred because error can be reduced by determination of the actual Ca:Mg ratio of the dolomite. However, the total CO3 method would be superior for heterogeneous systems, such as soils, since dissolution of dolomite in the residue by strong acid treatment may introduce errors from the dissolution of non‐carbonate Ca and Mg minerals.
ORGANIC PHOSPHATE COMPOUNDS IN CALCIUM CHLORIDE EXTRACTS OF SOILS: IDENTIFICATION AND AVAILABILITY TO PLANTS
Authors: WILD A. , OKE O. L.
Published: July 2006

The organic phosphate in CaCl2 extracts of dried soils was concentrated and purified by the use of ion exchange resins. Graded elution with formic acid separated three phosphate fractions (P1, P2, and P3), all of which contained inositol. By paper chromatography and assay of inositol, the phosphate in two of these fractions (P2 and P3) was found to be present mainly as myo‐inositol monophosphate. One form (P2) was resistant to hydrolysis and had a low availability to plants grown under aseptic conditions. The other (P3) was not pure, but was more easily hydrolysed and was readily used by plants. The phosphate in the remaining fraction (P1) was also available to plants and may also have been present as myo‐inositol monophosphate.
THE MICROPORE SIZE DISTRIBUTIONS OF CLAY MINERAL SYSTEMS
Authors: AYLMORE L. A. G. , QUIRK J. P.
Published: July 2006

The micropore (<100 Å) size distributions of compacted clay mineral systems have been examined by means of low‐temperature N2 sorption isotherms to saturation. The calculation of pore sizes was based on the application of the Kelvin equation, corrected for the adsorbed film thickness, to the parallel plate model.

Clay‐mineral systems have been shown to exist with a high degree of parallel alignment of the plate‐shaped crystals. This results in a high proportion of microporosity and in relatively discrete pore sizes.

In montmorillonite clays much intercrystalline overlap area in the dry matrix is inaccessible to N2 sorption. The structure of these systems may be governed partly by the effect, in suspension, of electrostatic interaction between the charged particles on crystal size, but largely by mechanical interaction on sedimentation and the size of the exchangeable cations present.
DISPERSION OF SOIL PARTICLES BY SONIC VIBRATION1
Authors: EDWARDS A. P. , BREMNER J. M.
Published: July 2006

Dispersion of soil particles is achieved without use of oxidants, acids, or peptizing reagents, by subjecting an aqueous suspension of the soil sample (10 g soil, 25 ml water) to sonic vibration at 13 to 15°C using a Raytheon (9 kc, 50 w) vibrator. Studies using soils of widely different textures and organic matter contents showed that the dispersion caused by sonic vibration for 30 min, as evaluated by pipette analysis for < 2 μ material, was similar to that obtained by chemical methods currently used for dispersion of soils. The dispersion effected by ultrasonic vibration of soil‐water suspensions using a probe‐type vibrator (18–20 kc, 60 w) is comparable to that achieved by sonic vibration. The vibration method of dispersing soil particles yields stable suspensions and is effective with highly calcareous soils and with soils containing large amounts of montmorillonite and organic matter. It permits dispersion of soil particles without dissolution of more than trace amounts of organic or inorganic material and does not significantly affect the pH or conductivity of the soil suspension.
MICROAGGREGATES IN SOILS1
Authors: EDWARDS A. P. , BREMNER J. M.
Published: July 2006

Studies of the dispersion of compound soil particles by sonic vibration and cation‐exchange resin techniques indicate that the difficultly dispersible particles in mineral soils of high base status are microaggregates (< 250μ diam) consisting largely of clay and humified organic material linked by polyvalent metals. The inter‐particle bonds in these microaggregates can be disrupted by application of mechanical energy (sonic vibration or prolonged shaking with water), the amount of energy required for dispersion of clay‐size mineral material being reduced by treatments that weaken or destroy these bonds (e.g. treatments leading to replacement of polyvalent metals by monovalent metals or to destruction of organic matter). A theory is proposed depicting microaggregate formation as a solid‐phase reaction involving linkage of electrically neutral clay mineral and organic matter particles by polyvalent metals on exchange sites, and microaggregate disruption by sonic vibration as a reversal of this reaction. Experiments to evaluate this theory are described.
THE ECOLOGY AND PHYSIOLOGY OF SOIL FUNGI INVOLVED IN THE DEGRADATION OF LIGNIN AND RELATED AROMATIC COMPOUNDS
Authors: JONES D. , FARMER V. C.
Published: July 2006

A study has been made of the colonization by soil fungi of kaolin pellets in which was incorporated either a lignin preparation extracted from Phragmites or the lignin‐related substances, vanillic acid or α‐conidendrol. Fungi isolated from the lignin pellets by the dilution method were grown in liquid culture containing the Phragmites lignin. Subsequent analysis by UV absorption spectrometry indicated up to 40 per cent loss of this material. IR analysis of the residual lignin showed that it was little altered.

Fungi from the pellets containing vanillic acid and α‐conidendrol were isolated by direct transfer of spores and mycelium from the pellets to agar plates. The range of soil fungi already known to metabolize vanillic acid in pure culture was extended by this method and included Stilbum spp., Humicola sp., and two unidentified species. Dry‐weight determinations of mycelia combined with UV absorption spectrometry and paper chromatography of culture filtrates indicated that, with the exception of Acremoniella sp., all isolates metabolized vanillic acid when it was supplied as sole C source. Growth‐promoting substances present in yeast extract were required by Volutella spp. before the vanillic acid was metabolized.

The pellet technique offers many possibilities for studying the microbiological degradation of soil substances and in addition enables the soil micro‐habitats to be explored in greater detail than has previously been possible.
THE ORIGIN AND DEVELOPMENT OF CLAY‐WITH‐FLINTS AND ASSOCIATED SOIL HORIZONS ON THE SOUTH DOWNS
Authors: HODGSON J. M. , CATT J. A. , WEIR A. H.
Published: July 2006

Clay‐with‐flints rests on remnants of the exhumed sub‐Eocene surface, which is shown to be an important geomorphological feature of the West Sussex Downs. Mineralogical and other soil profile studies indicate that the deposit has developed by the action of cryoturbation and soil‐forming processes on a thin cover of Reading Beds clay left on the sub‐Eocene surface during the southward recession of a small Eocene escarpment. Two horizons corresponding to Clay‐with‐flints sensu stricto of Loveday (1962) are recognized. The basal horizon is composed partly of insoluble Chalk residue, but mainly of clay moved down from overlying horizons into the spaces left on dissolution of the Chalk at the junction of the Chalk with the base of the Clay‐with‐flints. The upper horizon is composed of material from weathered remnants of Reading Beds clay, thoroughly mixed by cryoturbation with flints, other insoluble Chalk residue and clay from former basal horizons. The surface horizons of the soils often include additions of loess.
MEASUREMENT OF LOSSES FROM FERTILIZER NITROGEN DURING INCUBATION IN ACID SANDY SOILS AND DURING SUBSEQUENT GROWTH OF RYEGRASS, USING 15N‐LABELLED FERTILIZERS
Authors: GASSER J. K. R. , GREENLAND D. J. , RAWSON R. A. G.
Published: July 2006

Ammonium sulphate and calcium nitrate both containing excess 15N were applied to four acid sandy soils; two were from old arable fields and two from grassland, selected so that one of each pair was about pH 5 and the other about pH 6 (in water). The soils were incubated for 6 weeks at 21°C in large glazed earthenware pots, one set with the nitrification inhibitor 2‐chloro‐6‐(trichloromethyl)‐pyridine added and another without inhibitor. Ammonium and nitrate N were determined at intervals, and the total‐N at the start and after 6 weeks. The atom per cent 15N in the mineral‐N extracted from soils treated with ammonium sulphate was determined after 0, 3, and 6 weeks, and in the total‐N of all the soils given N‐fertilizer at 0 and 6 weeks.

Much added N was immobilized at first, but some was re‐mineralized during the second half of the incubation. Mineral‐N extracted from soils treated with ammonium sulphate contained less 15N than the fertilizer added, showing that part of the apparent re‐mineralization during the second half was from unlabelled soil organic matter.

After incubating for 6 weeks less than 5 per cent of the N added as nitrate was lost but about 5 per cent of the labelled‐N added as ammonium sulphate was lost from the two grassland soils. Adding the inhibitor prevented this loss.

After incubating, the soil remaining in each jar was halved to provide duplicate pots and sown with ryegrass. A similar series of pots with the same treatments (but with unlabelled fertilizer) was also prepared from the soils that had been stored slightly moist and at 21°C; these were sown with ryegrass. All pots were harvested after 42 days and again after 70 days.

More than 93 per cent of the labelled‐N was recovered in plants and soil, except from the two grassland soils to which calcium nitrate was added. It is concluded that while a little nitrogen may be lost during nitrification in some of these soils, more nitrogen may be lost during the growth of grass, when nitrate is present in relatively large amounts.

The nitrification inhibitor decreased yields of grass at the first cutting on grassland soils treated with ammonium, but increased them on soil treated with nitrate, suggesting that changing the proportions of nitrate to ammonium by adding the inhibitor alters the growth rate and yield of grass.
ASH SOILS IN WESTERN SUDAN
Authors: WHITE L. P.
Published: July 2006

The ash soils of the Jebel Marra region of Western Sudan are developed on a relatively recently deposited felspathic ash and do not contain allophane. Though they show some specific characteristics of ash soils elsewhere, many features are common to other soils of entirely different origin in the same region. Because of their immaturity, variation due to altitude and rainfall, which may differ considerably over short distances in the Jebel Marra, Massif, is minimal.
GENESIS, MINERALOGY, AND RELATED PROPERTIES OF WEST INDIAN SOILS
Authors: AHMAD N. , JONES R. L. , BEAVERS A. H.
Published: July 2006

Soils of the Maracas series from two sites in the Northern Range of Trinidad differ only in minor aspects. With the exception of cheluviation of iron and formation of goethite the soils preserve the mineralogy and to some extent the structure of the parent phyllite. Weathering of calcic and sodic plagioclases is rapid. Mica is well preserved even in surface horizons and resists physical weathering, but when reduced to clay‐size, it weathers rapidly to kaolinite throughout the solum with little accumulation of expandable minerals. Exchangeable K is very low in spite of the micaceous nature of the soil parent material. Low levels of availability of Ca, Mg, and particularly P are also characteristic of these soils. Total inorganic P is very low, the main fraction being reductant‐soluble iron phosphate; other forms of inorganic P are unimportant. Organic P, derived from the carbonaceous matter of the parent rock, increases with depth. From the results obtained, the Maracas series may be classified as a latosol. For these soils located in a humid tropical environment, the paradoxical situation exists that they do not undergo sufficient weathering to release and make available plant nutrients before the solum is carried downslope by erosional processes. As a result, they are relatively infertile.
A STUDY OF ACTIVITIES OF ENZYMES HYDROLYSING SUCROSE AND STARCH AND OF OXYGEN UPTAKE IN A SEQUENCE OF SOILS UNDER TUSSOCK GRASSLAND
Authors: ROSS D. J. , ROBERTS H. S.
Published: July 2006

Biochemical activities were studied at three sampling dates in a sequence of four soils, ranging in altitude from 275 to 1,520 m, on schist parent material in a tussock‐grassland association on the Old Man Range, Central Otago. Activities were similar under different tussock species.

The uppermost part of the soil appeared to be most affected by seasonal changes because fluctuations at different sampling dates were greater in samples of topsoil from depth 1 to 7.5 cm than in samples of A, AB, and B horizons at depths approximately 4, 13, and 28 cm.

Activities of enzymes without added substrate and of enzymes hydrolysing sucrose or starch generally increased with increasing altitude of the soils and were strongly correlated with organic C content and, to a lesser extent, with soil moisture content. In previous pasture surveys, enzymes hydrolysing sucrose had not been significantly correlated with organic C. Although oxygen uptakes were also positively correlated with these factors, and with numbers of viable bacteria, consistent differences between soils were not found.

Differences between A and AB horizons were usually greatest in the soil at the highest altitude but, otherwise, rates of regression of biochemical activities with depth of soil were generally similar in all soils.

Results may be indicative of biochemical activities in other mountain‐soil sequences.
CALCIUM: ALUMINIUM EXCHANGE EQUILIBRIA IN CLAY MINERALS AND ACID SOILS1
Authors: COULTER B. S. , TALIBUDEEN O.
Published: July 2006

Exchange reactions between 0.0in AlCl3 solutions of different pH and Ca‐saturated montmorillonite, vermiculite, illite, and soils from the Park Grass Experiment at Rothamsted and the Deerpark Experiment, Wexford, Ireland, showed that Al3+ and Al(OH)2+ were adsorbed from solutions of pH > 4.0 and Al3+ and H+ from solutions of pH < 3.0. When Al was adsorbed, the cation exchange capacity of Ca‐saturated soils and clays increased.

Conventional Ca: Al exchange isotherms showed that Al3+ was strongly preferred to Ca2+ on all soils and clays. The equilibrium constant for Ca: Al exchange, K, was identical for soils before and after oxidizing their organic matter and did not vary, for any exchanger, with Al‐saturation or the initial pH of the AlCl3 solution. This proved the validity of the procedure used for calculating exchangeable Al3+.

K values for Ca:Al exchange favoured Al3+ in the order: vermiculite > Park Grass soil > Deerpark soil > illite > montmorillonite.

The influence of surface‐charge densities of the clay minerals on this order is discussed and a method proposed and tested for calculating the K value of a soil from its mineralogical composition.
A SIMPLE AVAILABLE SOIL NITROGEN INDEX
Authors: ROBINSON J. B. D.
Published: July 2006

Mineralizable‐N (Δ mineral‐N) was correlated more with total‐N than with organic‐C in topsoils from maize fertilizer trial sites.

In the absence of N fertilizers, Δ mineral‐N was correlated with maize yield and per cent N in the leaf, in both seasons. Tests showed that a single regression equation calculated from data for two seasons, could be derived to express both these relationships.

Maize yield on plots treated with fertilizer‐N was not correlated with mineralizable‐N in the first season and was correlated only at the lower rate of application (45 kg N/ha) in the second season. But maize‐yield response to both rates of fertilizer‐N was correlated with mineralizable‐N in both seasons. Tests on the regression equations showed that yield responses were subject to seasonal variation.

The Δ mineral‐N value determined on conditioned soil samples (see Part 1) provided a good index of available N. It may be used to predict maize yield without N fertilizer and to rank soils, in terms of likely response to fertilizer‐N, for advisory purposes.
CHARACTERIZATION OF THE INOSITOL PENTA‐ AND HEXAPHOSPHATE FRACTIONS OF A NUMBER OF CANADIAN AND SCOTTISH SOILS
Authors: McKERCHER R. B. , ANDERSON G.
Published: July 2006

The nature of the inositol pentaphosphate and hexaphosphate isomers in a number of contrasting Canadian and Scottish soils has been examined.

The mixed esters were extracted from the soil with alkali and separated from other soil phosphates by anion‐exchange chromatography using HCOONH4 as eluent. The composition of the mixture was established by anion‐exchange chromatography using a gradient of HC1 as eluent, followed by paper chromatography of the esters thus separated, and by paper chromatography of the hydrolysis products.

Esters of myo‐ and scylloinositol together constituted more than 90 per cent of the mixture in most cases. Relatively small amounts of dl‐inositol and neoinositol were detected in hydrolysates and it was estimated that esters of these cyclitols did not exceed 10 per cent and 1 per cent, respectively, of the total. The ratio of myo‐+dl‐inositol hexaphosphates to scylloinositol hexaphosphate ranged from 1.1 to 2.7 in the Canadian soils and 1.8 to 4.6 in the Scottish soils. The ratio of hexaphosphates to pentaphosphates ranged from 0.9 to 2.4 in the Canadian soils and 3.0 to 4.3 in the Scottish soils.

The three soils with the highest pH values contained relatively large amounts of scyllo‐ relative to myoinositol hexaphosphate, but one very acid soil also contained a high proportion of this isomer and no consistent relationship was noted between the constitution of the inositol polyphosphate fraction and any other soil property.
AN ELECTROLYTIC RESPIROMETER FOR MEASURING OXYGEN UPTAKE IN SOILS
Authors: BIRCH J. W. , MELVILLE MARGARET
Published: July 2006

An electrolytic respirometer and its accompanying pressure compensator are described together with some examples of performance. A simple transistorized detector circuit is used to automatically switch electrolysis and timing circuits to replace O2 used by a respiring sample. The respirometer is capable of measuring oxygen uptake within the range of 2 ml to 500 ml per 24 h. Oxygen uptake is calculated from the duration and rate of electrolysis. The accuracy of the method depends upon the maintenance of a stable current during electrolysis. The pressure compensator utilizes motor‐operated syringes to eliminate variation in air volume within the respirometer chamber due to changes in atmospheric air pressure.
THE INFLUENCE OF TEXTURE ON THE MOISTURE CHARACTERISTICS OF SOIL
Authors: SALTER P. J. , WILLIAMS J. B.
Published: July 2006

A quantitative assessment was made of the effect of the proportion of sand, silt, clay, and organic matter in twenty‐six soils on the moisture contents at the upper and lower limits of available‐water of the soils. Regression equations were obtained which enabled the moisture contents to be estimated on a weight or volume basis from mechanical analysis data using either International or American size grades. The accuracy of estimating the upper limit of available‐water from the various equations ranged from ±9 to 22 per cent: for the lower limit from ±8 to 16 per cent of the measured values.

Mean values of the moisture contents at the upper and lower limits of available‐water for each textural class were calculated from the average particle‐size composition for each class and from the regressions obtained.
A BASIS FOR THE CLASSIFICATION OF SOIL
Authors: MACVICAR C. N.
Published: July 2006

Considering the nature of soil and the ends which a classification must serve, principles are stated whereby a soil classification may be devised for application over extensive areas of varied soil composition.

Naturally occurring bodies of soil, each with a high degree of homogeneity, are apparent rather than real individuals as their properties overlap to form a continuum. This continuum is multi‐dimensional because soil is characterized by numerous properties. The procedure of devising a classification is one of subdividing the continuum such that class boundaries accommodate, as far as possible, apparent individuals rather than of grouping like apparent individuals together.

A classification may be used to locate the position of a profile in the continuum and so define its relationship with other profiles. It may also be used to indicate the soil composition of land by using soil classes on a map to show differences in the soil mantle. The latter procedure may best be regarded as land classification or soil mapping rather than soil classification; a class of land or mapped area seldom contains profiles belonging exclusively to a single class, whereas a soil class never contains profiles of another class.

The soil form, a specific arrangement of diagnostic horizons, is introduced as a category above the series to facilitate the identification of soil profiles. Member series of a form are defined according to property variations within the diagnostic horizons of the form. It is suggested that a binomial system of profile nomenclature, using the form and the series, would have much to commend it.
THE EFFECT OF THE CONCENTRATION AND MOVEMENT OF SOLUTIONS ON THE SWELLING, DISPERSION, AND MOVEMENT OF CLAY IN SALINE AND ALKALI SOILS
Authors: ROWELL D. L. , PAYNE D. , AHMAD N.
Published: July 2006

Changes in permeability of a soil containing montmorillonite, and the swelling of orientated aggregates of extracted clay have been measured for a range of exchangeable sodium percentages and electrolyte concentrations. The concentrations at which clay moved out of the soil in the percolates have been found and compared with the concentrations at which aggregates dispersed in stationary solutions, and the concentrations at which soil suspensions dispersed when shaken.

The results indicate that: (a) permeability begins to decrease at the same concentration as the clay begins to swell, (b) the changes in permeability are directly controlled by the swelling of clay until clay dispersion and movement begins, (c) the concentration at which clay disperses depends on the mechanical stress applied, (d) when small mechanical stresses are applied, the proportion of the clay which swells and disperses depends directly on the exchangeable sodium percentage, and (e) large mechanical stresses may disperse most of the clay even at low exchangeable sodium percentages.
THE TIMES REQUIRED FOR THE ATTAINMENT OF AIR‐WATER EQUILIBRIUM IN CLAY SOILS
Authors: SIDES G. R. , BARDEN LAING
Published: July 2006

The coefficient of diffusion of air through the pore water of clay soils has been measured directly and has been shown to be markedly less than for free water and to decrease with water content.

It has been shown that these low coefficients of diffusion are not accounted for by the sinuosity of the flow channels, or by any important departure from Henry's law of solution at curved air‐water interfaces. The main factors appear to be constrictions in the flow channels and the reduced viscosity of the adsorbed water. It is concluded that air‐water equilibrium in partly saturated soils will be attained much more slowly than is generally assumed.
INORGANIC SOIL PHOSPHORUS
Authors: WEBBER M. D. , MATTINGLY G. E. G.
Published: July 2006

Sixteen soils and 4 soil preparations were cropped exhaustively with ryegrass in the glasshouse and monocalcium phosphate potentials (½pCa+pH2PO4=1) were measured after each of 6 consecutive harvests. The amounts of phosphorus (Q) removed from the soils by ryegrass accounted for 95·1–96·6 per cent of the variance in 1 for 3 soils and 2 soil preparations (P < 0·001), for 88·4–93·7 Per cent of the variance for 6 soils and 2 soil preparations (0·001 < P < 0·01), for 71·6–82·6 per cent of the variance for 3 soils (0·01 < P < 0·05) and for insignificant amounts of the variance for 4 soils. Values of ΔI/ΔQ ranged from 7 × 10–4 to 431 × 10–4½pCa+pH2PO4/ppm P removed from soil.

ΔI/ΔQ tended to decrease (i.e. the soils were more buffered) with increasing clay contents and with increasing amounts of NaHCO3‐soluble P and to increase (i.e. the soils were less buffered) with increasing amounts of CaCO3. Variations in organic C did not significantly affect ΔI/ΔQ. The following equation accounts for 81 per cent of the variance in ΔI/ΔQ for all soils except those in equilibrium with octacalcium phosphate:

ΔI/ΔQ× (104) = 225·9–4·17(% clay)+8·01(% CaCO3)–1·38(ppm NaHCO3‐soluble P).
INORGANIC SOIL PHOSPHORUS
Authors: WEBBER M. D. , MATTINGLY G. E. G.
Published: July 2006

Mixtures of Woburn (non‐calcareous) and Barnfield (calcareous) soils, with and without added monocalcium phosphate, and of Woburn soil with added CaCO3, were stored moist in an incubator at 25 ± 2 °C. Equilibrium phosphate concentrations in 0·01M CaCl2 and pH were measured on moist soils and mono‐calcium phosphate (½pCa+pH2PO4) and lime (pH–½pCa) potentials were calculated at intervals up to 670 days. Most of the mixtures remained under‐saturated with respect to CaCO3; values of ½pCa+pH2PO4 and pH–½pCa changed during storage but remained close to the solubility isotherm for octacalcium phosphate (OCP). Mixtures which reached equilibrium with CaCO, remained undersaturated with respect to OCP.
EFFECTS OF GREEN MANURING, FARMYARD MANURE, AND STRAW ON THE ORGANIC MATTER OF SOIL AND OF GREEN MANURING ON AVAILABLE NITROGEN
Authors: CHATER MARGARET , GASSER J. K. R.
Published: July 2006

In an experiment on green manuring started at Woburn in 1936, farmyard manure (FYM) was applied in alternate years until 1954 and straw similarly from then until 1963. Various green manures were grown from 1936 to 1953. From 1954 to 1963 ryegrass and trefoil were grown either each year or in alternate years; in 1964 and 1965 they were grown each year.

After annual cropping without organic manuring the organic‐C and total‐N decreased from 0·86 per cent and 0·091 per cent respectively in 1936 to 0·76 percent and 0·082 per cent in 1966. Ploughing in straw alone approximately halved the loss. FYM and green manures both maintained the original percentages of soil C and N. The effect of FYM and straw applied together was approximately the sum of the effects of FYM and straw applied separately.

Of the green manures ploughed in, trefoil returned the most nitrogen to the soil. Trefoil increased and ryegrass decreased the mineralizable‐N in the soil.
CONTENT OF INOSITOL PHOSPHATES IN SOME ENGLISH AND NIGERIAN SOILS
Authors: OMOTOSO T. I. , WILD A.
Published: July 2006

The mono‐, di‐, tri‐, tetra‐, penta‐, and hexaphosphates of inositpl accounted for between 11·2 and 30·4 per cent of the organic P in three English and four Nigerian soils. M yoinositol hexaphosphate was the component present in greatest amount in all soils. The lower esters (mono‐, di‐, and triphosphates) accounted for less than 3 per cent of the organic P in all soils, with the lowest amounts in the soils from Nigeria. For the penta‐ and hexaphosphates the ratio of myo‐ plus dl‐ isomers to scyll oinositol varied from 2·9 to over 10, the highest ratio occurring in the soils from Nigeria.

Examination of the techniques showed that they gave approximately correct estimates of the inositol phosphates. The organic P in soil which was not estimated as inositol phosphate occurred in other forms.
QUANTITATIVE PEDOLOGICAL STUDIES ON SOILS DERIVED FROM SILURIAN MUDSTONES
Authors: STEWART V. I. , ADAMS W. A. , ABDULLA H. H.
Published: July 2006

Considerable variations in the apparent density of the fine earth fraction were recorded in stony soils in Cwmcadian, Merionethshire. A highly significant relationship between fine earth apparent density and stone content was observed which was not caused by disturbance during sampling. The relationship could be predicted by assuming that the bulk volume of a stony soil approximates to the sum of the self‐packing volumes of the separated stone and fine earth components. It is suggested that in natural soils there is a similar relationship between soil apparent density and organic matter content, namely that the bulk volume of a soil containing organic matter approximates to the summed self‐packing volumes of the mineral and organic components.
SOIL WATER MEASUREMENT BY A LOW‐RESOLUTION NUCLEAR MAGNETIC RESONANCE TECHNIQUE
Authors: PREBBLE R. E. , CURRIE J. A.
Published: July 2006

A low‐resolution nuclear magnetic resonance analyser was used to measure soil water. The physical principles of the method are outlined to enable the non‐linearity of the response to water to be discussed. Two sands, five soils, and vermiculite were tested in the Laboratory. The instrument readings for all were depressed below the values that might have been expected from absolute water contents. In sands the depression increases with water content, that is, as pores of progressively larger size fill with water. In clay soils an initial depression is attributable to the rigidity with which the first small amounts of water are adsorbed on to the clay lattice: with more water the depression, as in sand, reflects the size distribution of the macropores.‘Relaxation’, a condition needed to ensure accuracy, can be induced by adding iron compounds and salts, but there is evidence that where these substances are present naturally in the soil they may cause different degrees of relaxation from soil to soil. When many soil samples of known type, structural state, and chemical status have to be analysed, a good calibration curve can be obtained and used to give water contents to a fraction of a per cent. A moisture characteristic was measured on a sand to assess the ability of the instrument to scan moisture profiles in long columns.
EDAPHOIDS AND PALEOSOLS OF BASALTIC ORIGIN IN THE GALILEE, ISRAEL
Authors: SINGER ARIEH
Published: July 2006

Red soil‐like layers intercalated amid basaltic flows from the Miocene‐Pleistocene in the Galilee, Israel, were examined. Micromorphological features which can be related to (a) translocation of materials, and (b) biological activity, and are therefore of distinct pedological origin, identify two of the layers as paleosols. Absence of these features and preservation of the fabric of the parent basalt serve to identify the third layer as an edaphoid. A fourth layer consists of an edaphoid superimposed on a paleosol. The edaphoids are composed almost entirely of a dioctahedral smectite. In two of the paleosols dioctahedral smectites predominate. In the third kaolinite and haematite are present also in considerable amounts. The presence of quartz in the paleosols is attributed partly to precipitation from Si‐rich solutions percolating the upper basalt layer and partly to aeolian contamination. In all the layers the free iron is predominantly in an anhydrous form. Similarity in the clay mineral composition of the Plio‐Pleistocene paleosols with that of contemporaneous basaltic soils is taken to indicate similarity in climatic conditions of formation. Differentiation between paleosols and edaphoids cannot be made by the use of a single criterion but must be based on corroborative evidence derived from micromorphological and mineralogical examinations.
THE STABILITY OF DICALCIUM PHOSPHATE DIHYDRATE IN SOIL
Authors: PROBERT M. E. , LARSEN S.
Published: July 2006

The rate of dissolution of labelled dicalcium phosphate dihydrate (DCP) of different particle sizes was measured by crop uptake and by extraction with phosphate solution.

Powdered DCP (< 0·18 mm) behaved similarly to monocalcium phosphate (MCP) throughout but larger particles dissolved more slowly and their availability increased with time. The 0·18–0·35, 0·35–0·7, and 0·7–1·4 mm fractions became more available than the equivalent rate of MCP during the growing period of 103 days. Such behaviour is predictable on the basis of a dissolutionimmobilization mechanism.
DETERMINATION OF THE CONTENTS OF CLAY‐SIZED PARTICLES IN SOILS
Authors: EMERSON W. W.
Published: July 2006

Edwards and Bremner's (1967) technique of dispersing soils by Bonification to form stable suspensions for particle‐size analysis without the addition of dispersant has been tested on a range of soils and a chalk. Carbonate soils or acid soils, containing a suite of minerals which normally form flocculated suspensions in water, yielded stable suspensions in water if the soil organic matter content was sufficiently high. With similar soils, low in organic matter, dispersant had to be added to stop partial flocculation of the test suspensions. Any gypsum present in soils has to be removed to prevent flocculation. For soils very strongly aggregated by organic matter, all the < 2 μm particles present can be released only by sonic vibration in dispersant rather than water.

On four soils studied in detail, the maximum amounts of < 2 μm particles obtained by sonic vibration, vigorous shaking, and the I.S.S.S. method have been compared. On three of the four soils, the values were in close agreement.
A MINERALOGICAL CHARACTERIZATION OF SOME VERTISOLS IN THE GEZIRA AND THE KENANA CLAY PLAINS OF THE SUDAN
Authors: FADL A. E.
Published: July 2006

Examination of the clay fraction of the Gezira and Kenana soils of the Sudan revealed montmorillonite as the dominant clay mineral, accompanied by kaolinite. The presence of illite and vermiculite is questionable. Quartz was found as an accessory mineral. Most of the kaolinite is concentrated in the ‘coarse clay’ (2–0.2 μm), whereas more than 90 per cent of the ‘fine clay’ consists of montmorillonite.
THE EFFICIENCY OF AGGREGATION INDICES IN THE COMPARISON OF SOME ENGLISH AND CANADIAN SOILS
Authors: BRYAN RORKE B.
Published: July 2006

The efficiency of indices of aggregation was tested by assessing the accuracy with which they reflected observed differences between selected samples from a variety of Albertan and Derbyshire soils. The most efficient indices were shown to be the percentage‐weight of water‐stable aggregates > 3 mm, > 2 mm, > 1 mm, > 0.5 mm, the coefficient of aggregation, and the mean‐weight diameter. Indices also showed highly significant variations in aggregation between fourteen soil groups, ranging from humus‐iron podzol to brown solodized‐solonetz. The Derbyshire soils showed significantly higher aggregate stability than those from Alberta. These differences may be the result of variations in clay mineral type, sodium content and climatic factors.
GEL CHROMATOGRAPHY OF HUMIC ACID
Authors: SWIFT R. S. , POSNER A. M.
Published: July 2006

Gel‐solute interactions have been reported in the application of gel chromatography to humic acid. The origins and nature of these interactions are discussed with particular reference to the behaviour of ‘Sephadex’ with compounds which are aromatic, heterocyclic, phenolic, or charged. Such structural units are known to be present in humic acid and could account for its observed interactions with ‘Sephadex’gel.

The behaviour of humic acid on ‘Sephadex’and a number of other gel materials in a variety of eluants is examined. The observed deviations of these systems from that of an ideal gel chromatography system are explained in terms of charge and adsorption effects.

The results indicate that a fractionation based solely on molecular weight differences can be achieved by using an alkaline buffer containing a large ammo cation as eluant together with ‘Bio‐gel’, ‘Sephadex’ or an agar based gel. Systems in which gel‐solute interactions occur should not be used for molecular weight fractionations.
A SIMPLE TRANSDUCER METHOD FOR THE MEASUREMENT OF MILLIMETER CHANGES IN WATER LEVEL
Authors: COUTTS J. R. H.
Published: July 2006

A description is given of a transducer‐float system for the measurement of small changes in water level in an evaporimeter tank. Readings can be recorded continuously, or at intervals of 15, 30, or 60 min.
WILKS'S CRITERION: A MEASURE FOR COMPARING THE VALUE OF GENERAL PURPOSE SOIL CLASSIFICATIONS
Authors: WEBSTER R.
Published: July 2006

Wilks's Criterion, the ratio of the determinants of the within‐class and total dispersion matrices, is described. It can measure the relative goodness of a general purpose soil classification, and can be used to determine how many clusters are present in a population, and hence how many classes can reasonably be recognized. Its use is illustrated with two examples. In the first, three soil maps of the same area, but at different scales, are compared. In the second, classifications of a set of profiles are shown to have recognized only three clusters.
ON THE POSSIBILITY OF CHARACTERIZING CALCIUM PHOSPHATES IN CALCAREOUS SOILS BY ISOTOPIC EXCHANGE
Authors: AMER FATHI , RAMY A.
Published: July 2006

Characterization of calcium phosphates depended upon the nature and the amount of phosphate used to react with reagent‐grade CaCO3. Formation of octa‐calcium phosphate (OCP) was inferred from the solubility equilibria after reacting CaCO3 with KH2PO4 solutions. Isotopic exchange measurements confirmed the presence of OCP, when the amount of P retained exceeded 44 μrnoles/g CaCO3. The determined surface‐Ca to surface‐P molar ratios were close to the theoretical Ca/P ratio of 1.33 in OCP. As P retained on CaCO3 decreased the surface Ca/P ratio markedly increased because of interference from surface Ca of the CaCO3. When CaCO3 was reacted with monocalcium phosphate (MCP), solubility equilibria indicated the formation of dicalcium phosphate dihydrate (DCPD). Isotopic exchange measurements, however, showed an average Ca/P ratio of only 0.375. This value corresponds to the composition of the metastable triple point solution (MTPS) formed on MCP dissolution rather than to the Ca/P ratio in DCPD.

MCP application decreased the measured surface‐Ca (exchangeable Ca) either for soil or Ca‐resin, because of blocking of the exchange sites by the MCP reaction products and, consequently, a lower rate of isotopic exchange. Surface phosphorus of the two investigated calcareous soils proved to be proportional to the lowering in pH initiated by MCP application. Characterization of MCP reaction products in calcareous soils may thus prove infeasible, in view of the unexpected reduction in surface‐Ca and the pH dependency of surface P.
EXCHANGEABLE SODIUM AND YIELDS OF COTTON ON CERTAIN CLAY SOILS OF SUDAN
Authors: ROBINSON GLENN H.
Published: July 2006

Within Sudan there are extensive areas of Vertisols in the Nile River valley south of Khartoum. These soils have clay contents ranging from 40 to 60 per cent, very slow permeability, exchangeable sodium percentages up to 35 or more in the upper 60 cm, and pH values between 8.0 and 9.6. Under present management, satisfactory yields of long staple cotton are obtained under irrigation on soils having exchangeable sodium percentage (ESP) of up to 35 in the upper 60 cm. It is proposed that soil characteristics such as type of clay, cracking and exchangeable sodium in the hot, dry climate of Sudan influence soil structure and water availability and thus the yields of cotton.
THE APPLICATION OF MULTIVARIATE ANALYSIS TO SOIL STUDIES
Authors: NORRIS J. M. , LOVEDAY J.
Published: July 2006

Allocation of a profile to a predetermined group is normally made by the surveyor in the field but alternatively a computer can be programmed to process data and make the allocation. Differences arising from these procedures may be due to differences in either the information used by computer and surveyor or the rules used to analyse the data. There is a third method, in which the surveyor, using the same data as the computer, provides a link between the other two. Comparison, in general terms, of possible results from these three methods is supported by a study on profiles from the Riverina, N.S.W. Using data for a standard set of variables and allocating into one of three groups, misallocation of 4 per cent of a test sample of forty‐six profiles resulted from both the computer method and the surveyor in the laboratory as compared with the surveyor's allocation of the same profiles on morphological properties in the field. This concurrence between the surveyor and the computer method allows the skill of the surveyor to be extended by way of the computer to technicians.
QUANTITY‐INTENSITY RELATIONSHIPS FOR LABILE SODIUM IN FIELD SOILS1
Authors: BOLTON J.
Published: July 2006

Exchange isotherms for Na with Ca+Mg in ten unfertilized soils show smaller buffer capacities for Na than K, larger Na than K activity ratios at equilibrium, and curvatures of the graphs at small Na activity ratios that could indicate larger exchange energies on about 0.5 per cent of the exchange sites.

Since equilibrium Na activity ratios in the soils were similar to those in rain, the latter ratios could be most important in controlling Na activity ratios in soils and the percentage saturation of exchange complex with Na. The geochemical significance of these ratios is discussed.
THE OCCURRENCE OF ETHYLENE IN ANAEROBIC SOIL
Authors: SMITH K. A. , RESTALL S. W. F.
Published: July 2006

The production of ethylene and other hydrocarbon gases by soils under anaerobic conditions was measured by gas chromatography. Ethylene was the only hydrocarbon gas which occurred in physiologically significant concentrations; more than 20 ppm was found in several soils after 10 days at 20°C. These concentrations were considerably higher than those which were known to cause severe reductions in the extension of root axes of some plant species.

Experiments with sterilized and unsterilized soil indicated that ethylene was produced by enzyme activity and not by chemical action. The gas was found in soil when the oxygen concentration fell below 2 per cent; total evolution was correlated with organic matter content, and was affected by drying and rewetting and by the growth of plant roots. The rate of production was increased by raising the temperature and by addition of glucose or peptone; high concentrations of nitrate depressed the rate, but sulphate and phosphate had little effect.

It is concluded that ethylene may be a significant factor in causing injury to crop plants under waterlogged conditions and also in situations where anaerobic pockets occur within a mainly aerobic soil structure, provided that escape of the gas from the soil is impeded sufficiently to allow inhibitory concentrations to build up in the vicinity of plant roots.
THE OXIDATION OF IRON SULPHIDES IN SOILS IN RELATION TO THE FORMATION OF ACID SULPHATE SOILS, AND OF OCHRE DEPOSITS IN FIELD DRAINS
Authors: BLOOMFIELD C.
Published: July 2006

Aerating pyritic soils causes acidification and the forrnation of acid sulphate soils, or cat‐clay. The Oxidation of pyrite in soils is associated with the deposition in tile drains of a form of ochre quite distinct from that formed by the action of filamentous iron bacteria. Pyrite‐derived ochre results from the action of Thiobacillus ferrooxidans, which, below pH 3.5–4.0, catalyses the Oxidation of Fe2+ and pyrite. In soils less acid than c. pH 4, pyrite oxidizes relatively slowly by chemical reactions to Fe2+ and SO24−. Under these conditions iron enters the drains as Fe2+ and is there oxidized by T. ferrooicidans and deposited as hydrated ferric oxide. Once the soil becomes acid enough for T. ferrooxidans to multiply, the rate at which pyrite oxidizes increases several‐fold, and at c. pH 3 iron appears in the drainage water in the ferric form. Liming seems to decrease the rate of Oxidation.
THE DETERMINATION OF ORGANIC PHOSPHORUS IN SOILS
Authors: STEWARD J. H. , OADES J. M.
Published: July 2006

A method for extraction and determination of organic phosphorus based on a pretreatment with IM HC1 followed by ultrasonic Vibration in 0.5M NaOH is proposed and shown to be generally superior to two commonly used procedures in terms of efficiency and speed. Determination of organic phosphorus by the proposed technique showed that almost a third of the phosphorus applied to a red‐brown earth growing a mixed legume‐grass pasture has been incorporated into organic molecules.