bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE DETERMINATION OF ORGANIC PHOSPHORUS IN SOILS
Authors: STEWARD J. H. , OADES J. M. 
Published: July 2006

SummaryA 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.
THE MEASUREMENT AND MECHANISM OF ION DIFFUSION IN SOILS. VIII —A THEORY FOR THE PROPAGATION OF CHANGES OF pH IN SOILS
Authors: NYE P. H. 
Published: July 2006

SummaryThe way pH changes in soil are propagated by movement of acids and bases is described. In acid soils the H3O+‐H2O acid‐base pair is most important, while in alkaline soils the H2CO3‐HCO3− pair is always dominant, its effect depending directly on the pressure of CO2. In neutral and slightly acid soils, soluble organic matter and the H2PO4−‐HPO24− pair may also contribute.A soil acidity diffusion coefficient is derived, and defined as:
image

where vl= the volume fraction of the soil solution, fl= the impedance factor for the liquid diffusion pathway, bHS= the pH buffer capacity of the soil, b
HB= the pH buffer capacity of each mobile acid‐base pair, Dl
HB= the diffusion coefficient of each mobile acid‐base pair in free solution,and the sum is taken over all mobile acid‐base pairs.The soil acidity diffusion coefficient may be used to predict the course of pH equilibration in practical situations. It is high in acid and alkaline soil, and at a minimum in slightly acid soil. It is little affected by variation of the ionic strength of the soil solution at concentrations less than 0.01M. When the pH buffer capacity of the soil is constant, and only the H3O+‐H2O and H2CO3‐HCO3− pairs are important, the soil acidity diffusion coefficient varies as cosh{2.303(pH—pH0)}, where pH0 is the pH at which the soil‐acidity diffusion coefficient is a minimum.
THE CHARACTERIZATION OF SOME SCOTTISH ARABLE TOPSOILS BY AGRICULTURAL AND ENGINEERING METHODS
Authors: SOANE B. D. , CAMPBELL D. J. , HERKES S. M. 
Published: July 2006

SummarySamples from fifty‐eight arable topsoils in south‐eastern Scotland were analyzed for compactability, plasticity, organic matter content, particle density, and particle‐size distribution. The samples were classified by the methods employed for engineering soils and the groupings so obtained were compared with the textural classes. The criteria for the classification of engineering soils provide useful information on the likely mechanical behaviour of arable soils in the field. Tests were made for correlation between fifteen soil properties. The organic matter content, which in the samples studied ranged from 2 to 10 per cent, was shown to influence several mechanical properties, including optimum moisture content, maximum dry bulk density, liquid limit, and plastic limit.Maximum bulk density and optimum moisture content were strongly correlated with Atterberg limits and organic matter content. The liquid limit was more closely correlated with particle‐size distribution than was the plastic limit. Unlike soils encountered in engineering, the particle density of these soils was not correlated with particle‐size distribution but, like the Atterberg limits, was strongly correlated with organic matter content.
CHARGE DISTRIBUTION AND THE CATION EXCHANGE CAPACITY OF AN IRON‐RICH KAOLINITIC SOIL
Authors: BARBER R. G. , ROWELL D. L. 
Published: July 2006

SummaryThe positive charge on an iron‐rich kaolinitic soil was found to increase from 11.1 to 14.2 me per 100 g as a result of lowering the pH from 8.5 to 3.0 in M NH4Cl solution and the negative charge decreased from 22.2 to 14.1. In 0.002M NH4C1 the positive charge increased from 0 to 0.3 and the negative charge decreased from 5.6 to 3.2. The variations in charge can be explained by the presence of 3 me per 100 g of permanent negative charge, pH dependent positive and negative charge influenced by the indifferent electrolyte concentration, and the overlap of diffuse layers causing a neutralization of charge.The ability of this soil to hold cations under field conditions is overestimated by m ammonium acetate at pH 7. Instead, a solution approximating to the pH, composition, and concentration of the soil solution should be used.
THE CLASSIFICATION OF ARID ZONE SOILS
Authors: WESTERN S. 
Published: July 2006

SummaryIn the arid environment of South Arabia the soils (sedosols, see Part I) are not significantly affected by pedogenetic processes. Classification of these soils is therefore in accordance with the principles outlined in Part I, being based upon a consideration of the mode of deposition rather than on considerations of pedo‐genesis. Sedimentary geomorphology, soil classification, soil mapping are discussed for two areas of South Arabia. Mapping purity was satisfactory and reliability was probably greatest in series that were wholly anthropic or wholly natural in origin. In classifying land for single‐flood irrigation agriculture, the total readily available moisture capacity is the major land classification factor. It is a function of texture and effective depth, modified in places by severe stratification.
A STUDY OF HUMIC ACID BY EQUILIBRIUM ULTRACENTRIFUGATION
Authors: POSNER A. M. , CREETH J. M. 
Published: July 2006

SummaryEquilibrium ultra centrifugation is a superior method to the more conventional sedimentation velocity technique for measuring the molecular weight of poly‐disperse humic acid. The technique can be used to estimate number, weight, and Z‐average molecular weights of humic acid and a measure of the polydispersity of the acid can thus be achieved.
HYSTERESIS IN THE MOISTURE CHARACTERISTICS OF CLAY SOIL
Authors: PAVLAKIS GEORGE , BARDEN LAING 
Published: July 2006

SummaryThe relation between soil suction, degree of saturation, and the air and water permeabilities is experimentally investigated for two clay soils. Marked hysteresis can exist between saturation and permeability, but does not follow a unique trend. Thus permeability can be greater on a wetting or drying cycle depending on the structure of the clay soil. This behaviour is considered in terms of the cluster concept of soil structure, and it is concluded that any general theory of hysteresis must recognize both the macrostructure and microstructure of a soil.
DETERMINATION OF 14C IN SOIL BY A GEL SUSPENSION METHOD
Authors: CHESHIRE M. V. , SHEPHERD H. , KNIGHT A. H. , MUNDIE C. M. 
Published: July 2006

SummaryRadioactivity in soils labelled with 14C was determined by suspending the finely ground soil in a thixotropic gel, dispersing it by ultrasonics and counting the dispersion in a liquid scintillation spectrometer. The relationship between the weight of sample and counting efficiency was found to be almost linear. Using 30 mg soil, the counting efficiency is 50 per cent and 14C may be determined with an average coefficient of variation of 1.5 per cent to within 5 per cent of the value determined by oxidative procedures.
POTASSIUM RESERVES IN A ‘HARWELL’ SERIES SOIL
Authors: TALIBUDEEN O. , WEIR A. H. 
Published: July 2006

SummaryA sample of Harwell soil containing 36 percent fine clay (< 0.3 μm) and 14 per cent coarse clay plus fine silt (0.3–5μm) was separated into fractions, and the K‐supplying power of soil and fractions measured by cropping with ryegrass, exchange with Ca resin and double‐label isotopic exchange with 42K and 45Ca ions.Mineralogical examination of the fractions coupled with the cropping experiments showed that the K‐supplying power of the soil to ryegrass can be explained by the presence of a zeolite, clinoptilolite‐heulandite, in addition to the clay minerals, mica, and interstratified illitic smectite, commonly found in a glauconitic clay‐rich soil. The 0.3–5 μm fraction, containing much zeolite, has an exchange diffusion coefficient for K ions to Ca resin of 1.8 × 10−16 cm2sec−1 compared with a value of 5.7 × 10−20 for the < 0.3μm fractions in which interstratified illitic smectite is the dominant mineral. Isotopic exchange shows that all Ca ions in fractions < 50μm are isotopically exchangeable. In fractions coarser than 20μm, some of the K ions in felspar and mica were not exchangeable within the duration of the experiments.
THE MECHANICAL STRENGTH OF UNSATURATED POROUS GRANULAR MATERIAL
Authors: TOWNER G. D. , CHILDS E. C. 
Published: July 2006

SummaryThe influence of pore‐water suction on the strength of a porous material is that it contributes a compressive load which increases the shear strength. When the material is unsaturated, the normal load or effective stress is due, in part to the continuous water at measured suction in unemptied pores, and in part to isolated bodies in nominally emptied pores at suctions approximating to the suction at emptying.When the material is draining from saturation, the effective stress σ is
image

where S is the fraction of saturation, α is the fraction of the initial water content drained at the maximum suction, Psd is the prevailing pore water suction, and Psd is a suction passed through in reaching pSd at which the reduction of S is dS. When the material is rewetting, the relationship becomes
image

where psw is now the prevailing suction during wetting and f is a distribution function of the degree of saturation such that
image

δS is the fractional saturation removed in the suction range δsd at sd and regained in the suction range δsw at sw. msd is the maximum suction attained.The effective stress is revealed experimentally by unconfined compression tests on samples with imposed pore water suctions, and the dependence on this suction confirms reasonably that which is predicted by the theoretical formulas.
SOME EFFECTS OF FERTILIZERS AND FARMYARD MANURE ON THE ORGANIC PHOSPHORUS IN SOILS
Authors: ONIANI O. G. , CHATER MARGARET , MATTINGLY G. E. G. 
Published: July 2006

SummaryThe amounts of P applied cumulatively to a neutral arable soil (pH 7.1–7. in 0.01M CaCl2) at Rothamsted, as farmyard manure, alone or with superphosphate, which were converted to organic P in 100 years ranged from 18 to 44 μg P/g of soil (0–23 cm). Superphosphate alone (3300 kg P/ha) slightly lessened the total organic P in the soil. Neither farmyard manure nor super‐phosphate significantly changed the amounts (38 to 42 μg P/g) of inositol penta‐ and hexaphosphate in these soils. In the surface layers (0–7.5 cm) of soils from permanent grassland at Rothamsted, superphosphate (3370kg P/ha) increased organic P by 134 μg P/g at pH 4.5 and 19 μg P/g at pH 6.5, about 6 and 1 per cent respectively of the P remaining from superphosphate applied cumulatively since 1858. In the sub‐surface layers (7.5–23 cm) superphosphate increased organic P by 93 μg P/g at pH 4.5 and 62 μg P/g at pH 6.2, about 18 and 10 per cent respectively of the P remaining from superphosphate. The sum of inositol penta‐ and hexaphosphates accounted for 32 per cent at pH 4.5 and 21 per cent at pH 6.5 of the increases in organic P in the surface layers and 45 per cent and 26 per cent in the sub‐surface layers at pH 4.5 and 6.5 respectively.Superphosphate (1260–2100 kg P/ha) applied intermittently or cumulatively increased total organic P by 19 to 52 μg P/g and inositol penta‐ and hexaphosphates by 13 to 17 μg P/g in acid tea soils (pH 3.2–3.4) from Georgia, U.S.S.R. Rock phosphate (510–1020kg P/ha) applied cumulatively had no effect on either the total organic P or the inositol P in acid tea soils (PH 3.6–3.7) from Ceylon.
THE EFFECT OF ORGANIC MATTER ON THE BULK AND TRUE DENSITIES OF SOME UNCULTIVATED PODZOLIC SOILS
Authors: ADAMS W. A. 
Published: July 2006

SummaryOrganic matter content was found to have a dominant effect on both the bulk and true densities of soil in the organic and eluvial horizons of the podzolic soils examined. The soils were stone‐free, structureless, and of similar texture. The effects of organic matter on bulk density were described by the equation:
image
A similar equation was devised for true density. Use of these equations indicated that, in the soils examined, total pore space could be predicted from organic matter content measured as per cent loss on ignition.
THE EFFECT OF pH ON THE INCORPORATION OF AMINO ACIDS INTO HUMIC ACID EXTRACTED FROM SOIL
Authors: ADAMS W. A. , PERRY D. R. 
Published: July 2006

SummaryThe effect of pH on the incorporation of six 14C‐labelled amino acids and a dipeptide into humic acid extracted from a podzolic soil was examined. Maximum incorporation was found to occur at a pH which coincided with the apparent dissociation constants of their α‐amino groups. Incorporation took place, into forms which were both acid‐hydrolysable and non‐hydrolysable, the latter accounting for between ten and twenty per cent of the total.
CLAY MINERALS IN SOILS DERIVED FROM LOWER OLD RED SANDSTONE TILL: EFFECTS OF INHERITANCE AND PEDOGENESIS
Authors: WILSON M. J. 
Published: July 2006

SummaryThe clay mineralogy of thirty‐two profiles located mainly in the Vale of Strathmore and developed on glacial till derived from Lower Red Sandstone sediments and lavas has been investigated by X‐ray diffraction. The soils were selected so that the parent material was related predominantly to one of the rock types common in the Lower Old Red Sandstone succession—namely, marl, sandstone, lava, or conglomerate. Comparison of the < 1.4μm fractions separated from fresh rock samples with those separated from the C horizons of the soils clearly established the dominant influence of parent rock on the soil‐clay mineralogy. The clay minerals inherited by the soil often include unusual trioctahedral expansible minerals such as saponite, interstratified vermiculite‐chlorite, and smectite‐vermiculite, as well as more common types like mica, montmorillonite, and chlorite. Kaolinite is also found but it is not certain that it is only of inherited origin. Weathering of the clays during soil formation brings about complete degradation of the expansible trioctahedral minerals, a process usually well advanced in the B or even at the top of the C horizon, and vermiculitization of mica. The latter process occurs mainly in the A horizon, with concomitant precipitation of interlayer aquohydroxy‐aluminium ions thereby forming a vermiculite‐chlorite intergrade. Chlorite and kaolinite appear to be little affected by weathering. The weathering transformations are most pronounced in freely drained acid soils (pH < s) and are at a minimum in poorly drained soils and where the pH remains above 6. The susceptibility to weathering of the trioctahedral expansible minerals results in relatively high values for exchangeable magnesium at the base of the profile.
TACTOID SIZE AND ION EXCLUSION IN FLOCCULATED CLAYS
Authors: MILLS J. G. , ZWARICH M. A. 
Published: July 2006

SummaryThe chloride‐exclusion volume of calcium‐saturated specimens of two bentonites and seven soils were determined over a range of electrolyte concentrations. These systems are believed to approximate the flocculated condition of most Manitoba soils. The montmorillonite was found to be arranged in tactoids or crystallites having an approximate 19Å basal spacing. The assumption of complete chloride exclusion from the interlayer volume over most of the concentration range combined with exclusion according to Gouy theory by the external surfaces provided a reasonable explanation of the experimental data. The number of montmorillonite layers comprising a tactoid, as calculated from the negative absorption determinations, was found to be strongly dependent upon the particle size of the montmorillonite.
DETECTION OF CLAY IN SOIL SOLUTION WITH METHYLENE‐BLUE PAPER AND THE ASSESSMENT OF CLAY MOBILITY IN SOILS
Authors: GOMBEER R. , D'HOORE J. 
Published: July 2006

SummaryThe adsorption of methylene blue and the accompanying colour change appears to be a fairly specific and sensitive reaction for colloidal soil clay, especially when used with chromatography paper as a supporting medium. Thus minute amounts of clay in migrating soil solutions can be detected, and stability and electro‐phoretic mobility of very dilute suspensions evaluated.
STUDIES ON SOIL COPPER I. THE FRACTIONATION OF COPPER IN SOILS
Authors: McLAREN R. G. , CRAWFORD D. V. 
Published: July 2006

SummaryA method for fractionating soil copper was developed and applied to 24 soils representing a range of British soil types.The scheme distinguishes five fractions:

soil solution and exchangeable copper;
copper weakly bound to specific sites;
organically bound copper;
copper occluded by oxide material; and
residual copper mainly in clay lattice structures.

Correlation and regression analyses confirmed the general validity of the scheme and indicated an association between free manganese oxides and copper which considerably influences the distribution of copper between the main soil constituents. It is suggested that the concentration of copper in the soil solution is controlled by equilibria involving specifically adsorbed copper and that the bulk of the‘available’soil copper reserves reside in the organically bound fraction.
OXIDOREDUCTIVE DEGRADATION OF SOIL MINERALS AND CLAYS D,L‐3(3,4‐DIHYDROXYPHENYL) ALANINE BY SOIL MINERALS AND CLAYS
Authors: MAYAUDON J. , EL HALFAWI M. , BATISTIC L. 
Published: July 2006

SummaryThe effect of the perhydrol (H2O2) treated soils on the decarboxylation rate of d,1‐3(3,4‐dihydroxyphenyl) alanine (DOPA), as examined by radiorespirometry, is highly significant and well‐correlated (r=+0.913) with the clay content.Among the pure Na clays used, Wyoming bentonite had the strongest effect on the DOPA decarboxylation. The reaction was activated by phosphate buffer and completely inhibited by a dithionite treatment.Gas phases like carbon monoxide, hydrogen, or nitrogen do not inhibit the DOPA decarboxylation rate.A chromatographic study of the intermediate products formed during DOPA degradation reveals the presence of 5,6‐dihydroxyindole. These results suggest that DOPA degradation by clays proceeds by a sequence of oxidoreductive reactions following the Raper (1927) scheme. The ferric oxides associated with the clay, and not the dissolved oxygen, are the electron acceptors. DOPA is oxidized to eumelanin which has an elementary percentage composition of C = 62.65; N = 11.05; H = 6.30; 0 = 20.
REAPPRAISAL OF ETHYLENE GLYCOL MONO‐ETHYL ETHER (EGME) METHOD FOR SURFACE AREA ESTIMATIONS OF CLAYS
Authors: ELTANTAWY I. M. , ARNOLD P. W. 
Published: July 2006

SummaryUsing an ethylene glycol mono‐ethyl ether (EGME) retention method, full unimolecular layer coverage of Ca‐montmorillonite surfaces was established in 2 hours in an evacuated system (0.5 mm Hg) containing a free liquid surface of EGME and dry CaCl2, as a separate phase. EGME retention in the presence of CaCl2‐EGME solvate led to incomplete unimolecular layer coverage, the EGME retention being governed by exchangeable Ca‐EGME interaction and not by the real extent of the clay surface. Unlike montmorillonite which has the two layers of EGME molecules between adjacent alumino‐silicate sheets, a vermiculite intercalated only one layer of EGME in the interlamellar space. Relevant X‐ray and differential thermal microanalysis data are provided.
STUDIES ON IODINE IN BRITISH SOILS
Authors: WHITEHEAD D. C. 
Published: July 2006

SummaryA method for the determination of iodine in soils and other agricultural materials was developed on the basis of an existing Auto‐analyser procedure for iodine in blood.Using this method, soils from twenty‐three widely separated sites in the U.K. were found to have total iodine contents ranging from 2.7 to 36.9 mg/kg. Total iodine contents were not closely correlated with the distance of the site from the coast or with rainfall, indicating that these factors did not exert major effects on iodine content. When two soils derived from marine alluvium were excluded, total soil iodine contents were positively correlated with aluminium oxide extracted by Tamm's reagent (r= 0.88***), with ferric oxide extracted by citrate‐dithionite (r= 0.64**), and with soil organic matter (r = 0.59**).Analysis of twenty‐two fertilizer materials, and of the faeces and urine from sheep fed diets containing two levels of iodine, indicated that inputs of iodine to the soil from these sources were small.From the correlation between total soil iodine contents and other soil properties, together with the proportions of the total iodine extracted by various reagents including sodium hydroxide and oxalic acid, it is concluded that soil iodine is associated, in part, with sesquioxide material and, in part, with soil organic matter.
THE PREPARATION OF CLAY SOILS FOR DETERMINATION OF STRUCTURE
Authors: GREENE‐KELLY R. 
Published: July 2006

SummaryMost methods for the determination of structure require the soil to be freed of water and yet to retain its original character. The methods of freeze‐drying and critical point‐drying are examined and it is concluded that they are not generally satisfactory. It is possible to preserve the soil fabric whilst water is slowly exchanged with an organic solvent (e.g. methanol or dioxan). The fabric is hardened and the degree of hardening is increased by subsequent exchange with certain water‐immiscible solvents (e.g. diethyl ether). Some shrinkage must be tolerated when it is desired to remove the liquid from the fabric. The best method was found to be infiltration by liquid carbon dioxide and its removal above its critical temperature. Despite some shrinkage the fabric seems unchanged.
THE EFFECT OF DENSITY ON WATER RETENTION PROPERTIES OF FIELD SOILS
Authors: REEVE M. J. , SMITH P. D. , THOMASSON J. 
Published: July 2006

SummaryThe bulk density, available water (Aν), air capacity (Cα), and retained water capacity (θν) were determined for 158 A, B, and C horizons of field soils. Clay (< 2 μm) and silt (2=60 μm) were also determined. Statistical analysis of the results demonstrated that bulk density exerts a profound influence on Aν, Cα, and θν, but the effect varies between texture groups and horizons. Significant negative correlations were obtained between bulk density and Cα for most texture and horizon groups. In B and C horizons Aν and θν also decrease with increasing density, whereas in A horizons Aν and θν tend to increase with bulk density except in silty soils. Within a limited range it is feasible to control these parameters by using field techniques to achieve optimum bulk density for particular soils.