bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE MECHANISM OF PHOSPHATE ADSORPTION BY KAOLINITE, GIBBSITE, AND PSEUDOBOEHMITE
Authors: MULJADI D. , POSNER A. M. , QUIRK J. P. 
Published: July 2006

SummaryThe adsorption isotherms (20°C) of phosphate on two potassium kaolinites and two aluminium oxides have been determined at pH values from 3 to 10 and at concentrations ranging from 10−4 to 10−2M. The reversibility of the adsorption with respect to pH and concentration has also been examined.The isotherms result from at least three types of adsorption site (regions I, II, and III) of widely different reactivities. The number of adsorption sites increases to a limit with decrease in pH for regions I and II. The behaviour of region III is more complex.The different adsorbents behave in essentially the same manner and differ only in the number of adsorption sites.It is tentatively suggested that regions I and II are located on an edge –Al(OH)2 of the adsorbents, while region III results from penetration into some amorphous region of the crystal surface.
THE MECHANISM OF PHOSPHATE ADSORPTION BY KAOLINITE, GIBBSITE, AND PSEUDOBOEHMITE
Authors: MULJADI D. , POSNER A. M. , QUIRK J. P. 
Published: July 2006

SummaryThe 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

SummaryA 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

SummaryConductimetric 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

SummaryCalcite 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

SummaryThe 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

SummaryThe 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

SummaryDispersion 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

SummaryStudies 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

SummaryA 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

SummaryClay‐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

SummaryAmmonium 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

SummaryThe 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

SummarySoils 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

SummaryBiochemical 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

SummaryExchange 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

SummaryMineralizable‐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

SummaryThe 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

SummaryAn 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

SummaryA 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.