bluuebunny/crossref_metadata_2025_split huggingface dataset:
URANIUM ACCUMULATION IN SOILS FROM LONG‐CONTINUED APPLICATIONS OF SUPERPHOSPHATE
Authors: ROTHBAUM H. P. , McGAVESTON D. A. , WALL T. , JOHNSTON A. E. , MATTINGLY G. E. G. 
Published: July 2006

SummaryThis paper describes the accumulation of uranium in soils from superphosphate applied annually to arable and grassland soils. Rates of application of superphosphate were equivalent to about 33kg P and 15 gU ha−1 year−1 in three experiments at Rothamsted and to about 37 kg P and 16g U ha −1 year −1 in one experiment in New Zealand. Most of the uranium (about 1300 g U ha −1) applied in superphosphate to the clay loam soil at Rothamsted since 1889 was retained, like P, in the plough layer of arable soils or was adsorbed by the organic surface layers of soils under permanent grassland. Uranium applied in superphosphate to grassland in New Zealand since 1954 (about 330 g U ha−1) was also concentrated in the surface layers of the soil.
CALCIUM DEFICIENCY IN SOME solONETZIC SOILS OF ALBERTA
Authors: CARTER M. R. , WEBSTER G. R. , CAIRNS R. R. 
Published: July 2006

SummaryAnalysis of displaced soil solutions, at half available moisture percentage, indicated that Mg to Ca (Mg/Ca) ratios and Ca to total cation (Ca/TC) ratios ranged from 0.35 to 3.64 and 0.74 to 0.04, respectively, in the A and B horizons of the solonetzic soils under study. The growth of barley in simulated solution cultures commenced to decline when the Mg/Ca ratio in solution exceeded 1.0, or when the Ca/TC ratio was lower than 0.15, regardless of levels of salinity, concentrations of Ca or Mg, or differences in ionic strength. Reduced growth was followed by symptoms of Ca deficiency. Growth of barley in soil from various horizons of solonetzic soils supported the results found in solution culture. Calcium amendments to soils with low Ca/TC ratios or high Mg/Ca ratios in the soil solution, gave increases in growth and prevented Ca deficiency.
THE pH DEPENDENCE OF THE SURFACE CONCENTRATIONS OF CALCIUM AND PHOSPHORUS ON HYDROXYAPATITE IN AQUEOUS solUTIONS
Authors: BELL L. C. , MIKA H. 
Published: July 2006

SummaryA radioisotope dilution technique was used to measure the surface concentrations of Ca and P on hydroxyapatite equilibrated at pH values ranging from 5.19 to 8.81. The concentrations were rarely equal to those calculated for a stoichiometric surface. In general the molar surface Ca/P increased from a value less than the stoichiometric figure of 1.67 at low pH values to a value greater than 1.67 at high pH values. The solution Ca/P showed the opposite trend with pH.The deviations of the surface concentrations of Ca and P from stoichiometric values were attributed to adsorption and desorption of the elements at the solid surface. The extent of these reactions was influenced by both surface charge and the solution concentration of Ca and P. The relevance of the pH dependence of the surface composition of hydroxyapatite to the interpretation of solubility studies on the solid is discussed.
EFFECTS OF CATION EXCHANGE MATERIAL ON ZINC ADSORPTION BY SOILS
Authors: WADA KOJI , ABD‐ELFATTAH ALY 
Published: July 2006

SummaryThe adsorption of Zn by soils which are different in their major cation‐exchange materials was measured at equilibrium Zn concentrations up to 10−2 M in 10−2 to 10−3 M CaCl2. The results are interpreted on KZnCa[Zn]soil plots, where KZnCa is the selectivity coefficient defined by the equation
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All natural samples except those containing halloysite exhibited no or very small specific Zn adsorption. All Ca‐saturated samples exhibited specific Zn adsorption dependent on cation‐exchange materials. The cation‐exchange sites with high selectivities for Zn (KZnCa > 10) constitute more than 40 per cent of the total exchange sites in soils containing allophane, imogolite, and halloysite, whereas those with moderate to low selectivities for Zn (KZaCa < 10) predominate in montmorillonitic, vermiculitic, and humic soils. Differences in the contribution of the respective cation‐exchange materials to specific Zn adsorption are discussed relating to differences in the origin of their negative charge.
SOIL ORGANIC MATTER STUDIES: EXTRACTION WITH FORMIC ACID/DIMETHYL SULPHOXIDE MIXTURES AND FRACTIONATION WITH Zr(IV)
Authors: KIBBLEWHITE M. G. , TINSLEY J. 
Published: July 2006

SummaryMixtures of the dipolar organic solvents formic acid (FA) and dimethyl sulphoxide (DMSO) were used to extract organic matter from soils. At 100 °C optimum extraction from a calcareous clay loam was with 80/20 v/v FA/DMSO, corresponding to a maximum in dielectric constant.Extraction of seven soils with boiling FA/H, O (107 °C) and FA/DMSO (112 °C) indicated that similar amounts of C and N are generally dissolved by the two solvent mixtures. However, FA/DMSO was about twice as efficient as FA/H2O for the ver‐miculite‐rich, calcareous, organic clay loam, removing 66 per cent of its C and 54 per cent of its N.Zr(IV) hydroxide in acidic aqueous acetone was a better flocculant than Ti(IV) for the dissolved organic matter. Model compound studies, together with hydrolytic and NMR studies, indicated that Zr precipitates carbohydrate‐like but not aromatic organic components. The quantity of Zr sorbed to the organic matter corresponds closely with its C.E.C. determined by Ba retention.
EXAMINATION OF THE HETEROGENEITY OF AMORPHOUS SILICO‐ALUMINAS AND ALLOPHANES USING THE ELECTRON MICROPROBE
Authors: PYMAN M. A. F. , KNUIMAN M. , ARMITAGE T. M. , POSNER A. M. 
Published: July 2006

SummaryAmorphous silico‐aluminas of varying composition prepared by simultaneous precipitation from aluminium nitrate and sodium silicate solutions were found to be heterogeneous by analysis in the electron microprobe. Exceptions were samples of Si/Al atomic ratio 1.5, which showed no heterogeneity for varying conditions of preparation. Silico‐aluminas prepared by the co‐hydrolysis of ethyl orthosilicate and aluminium isopropoxide were more heterogeneous, and their heterogeneity showed a greater variation with composition. The technique was able to establish heterogeneity of compositions but it was not certain whether homogeneity of the samples in the microprobe represented the homogeneity of composition in view of the large number of particles that appear to make up the aggregates. The most likely explanation of the heterogeneity is thought to be the presence of a matrix of variable composition surrounding the particles. Two out of five natural allophanes showed no evidence of heterogeneity.
SOIL DEFORMATION AND SHEAR STRENGTH CHARACTERISTICS OF SOME CLAY SOILS AT DIFFERENT MOISTURE CONTENTS
Authors: SPOOR G. , GODWIN R. J. 
Published: July 2006

SummaryThe soil deformation and shear strength characteristics of three clay soils were determined at different moisture contents and spherical pressures, using a quick un‐drained triaxial compression test. The soils were found to deform either in a compressive way or by brittle fissuring, depending upon the relative values of moisture content, dry density and spherical pressure. The critical state concept of soil deformation can explain qualitatively the behaviour of these spils at high moisture contents but not at low. The Bridgman concept for fracture in brittle materials describes the soil behaviour at low moisture contents.The shear strength of the clay soils tested was more closely related to the soil moisture suction and to the amount of shrinkage which occurred on drying than to the absolute dry bulk density. The influence of moisture content and spherical pressure on the effectiveness of certain cultivation operations are considered.
SPATIAL REsolUTION AND CALIBRATION CHARACTERISTICS OF TWO NARROW PROBE GAMMA‐RAY TRANSMISSION SYSTEMS FOR THE MEASUREMENT OF SOIL BULK DENSITY IN SITU
Authors: SOANE B. D. , HENSHALL J. K. 
Published: July 2006

SummaryTwo dual‐probe gamma‐ray transmission systems using caesium‐137 sources were examined. The performance of a small Geiger‐Muller detector was compared in respect to spatial resolution and calibration characteristics with an NaI(TI) crystal detector fitted to a thermally stabilised narrow photo multiplier with variable photon energy discrimination. The NaI(TI) detector had progressively better depth resolution with increasing discrimination threshold and more linear calibration relationships than the GM detector. The calibration linearity and sensitivity with the GM detector were strongly dependent on the mass thickness of the probe wall tubing. Count rate was not dependent on soil composition with either system. The GM detector system provided a satisfactory instrument of restricted performance. For good spatial resolution near the surface a narrow photo multiplier with thermal stabilisation overcame some of the difficulties previously found with NaI(Tl) detectors.
BRITTLE FRACTURE OF SOIL AGGREGATES AND THE COMPACTION OF AGGREGATE BEDS
Authors: BRAUNACK M. V. , HEWITT J. S. , DEXTER A. R. 
Published: July 2006

SummaryA statistical theory is developed for the brittle fracture of soil aggregates. Fracture is assumed to depend on the flaws, such as cracks and holes, within the aggregates, the weakest flaw limiting strength. An equation known as the third asymptote distribution of smallest values gives the distribution of these weakest flaws.The crushing strength of aggregates of five soils from South Australia and Queens land is compared with theory and agreement is good. Larger aggregates have smaller mean values of tensile strength than smaller aggregates at both ‐100 kPa and ‐153 MPa water potential. A sudden increase in strength occurs for aggregates larger than about 6 mm in the Queens land soils which is more marked with the drier samples. This is consistent with the idea that these larger aggregates are produced by the compacting effects of machinery, whereas the smaller aggregates are produced by the self‐mulching effect.Changes in the internal structure of beds of aggregates are described as a function of amount of uniaxial compaction. A statistical method gives information about the size distributions and relative positions of aggregates and voids within the compacted beds. Compaction occurred almost exclusively at the expense of inter‐aggregate porosity, and the largest voids were excluded first by compaction.
AVAILABILITY OF POTASSIUM TO RYEGRASS FROM SCOTTISH SOILS I.
Authors: SINCLAIR A. H. 
Published: July 2006

SummaryScottish soils were cropped with two sowings of perennial ryegrass (Lolium perenne, cv, Dutch Barenza) in the glasshouse, without addition of potassium, until growth virtually ceased. Potassium uptake and the corresponding changes in soil K properties were examined.Uptake of K correlated well over the entire cropping period with the initially labile K predicted from the Q/I isotherms of the soils, although K uptake was at least a factor of 1.9 greater than the initially labile K.The Q/I isotherms were similar for soils from the same series, and the form of the lower part remained virtually unchanged during intensive cropping. The equilibrium activity ratio, AR0, of soil K measured in 0.01 M calcium chloride was reduced in all soils to a narrow range close to a mean value of 3 × 10 −4 M1/2.Drying‐and‐wetting fresh soil samples severely depleted of ryegrass‐available K raised their K status. The increases were negatively correlated with the percentage K saturation of the fresh depleted soils, and a K saturation of 1.4 per cent must apparently be left in the fresh cropped soils for no K to be released. Freezing‐and‐thawing did not affect the K status of these soils.
SUGGESTED AMENDMENTS TO THE WORLD SOIL CLASSIFICATION TO ACCOMMODATE SCOTTISH MOUNTAIN AND AEOLIAN SOILS
Authors: BIRSE E. L. 
Published: July 2006

SummaryThe Scottish mountain soils above 600 m occur in an environment strongly influenced by low temperatures, with associated cryogenic processes having a marked effect on their development and morphology. In the most extreme situations these cryogenic processes dominate the soils and it is suggested that the World Soil Classification (FAO‐UNESCO, 1974) should be amended to include the major unit of Cryosols. Such a unit would also incorporate those soils of high latitudes, which are similarly dominated by freeze‐thaw cycles.A second distinctive group of soils occurs in the Scottish mountains, which are developed on wind‐distributed material. Their existence and continued development are largely dependent on the action of wind and the name proposed for these soils is Aeolisols. Such soils are to be found at lower altitudes also, wherever strong winds prevail and there is a supply of material suitable for movement by wind over fairly short distances.
OPTIMAL INTERPOLATION AND ISARITHMIC MAPPING OF SOIL PROPERTIES
Authors: BURGESS T. M. , WEBSTER R. 
Published: July 2006

SummarySoil properties mapped in two intensive surveys had large nugget variances, leading to large estimation variances and erratic isarithms when mapped by punctual kriging. It is likely that both surveyors and survey clients are interested in average values of soil properties over areas rather than point values, and such values can be obtained by block kriging. Estimation variances are very much smaller, and maps of sodium and stone content at Plas Gogerddan, Central Wales, kriged over blocks 920m2, and thickness of cover loam at Hole Farm, Norfolk, kriged over blocks of 400m2, are much smoother than the punctually kriged maps. The map of Hole Farm has a distinct and meaningful regional pattern.
MACRO‐ AND MICROMORPHOMETRIC INVESTIGATION ON SOIL‐DEXTRAN INTERACTIONS
Authors: PAGLIAI M. , GUIDI G. , MARCA M. LA 
Published: July 2006

SummaryThe effect of three microbial dextrans of defined molecular weight, on shrinkage and porosity inside clods has been studied on two Italian clay soils, a Fluvisol and a Vertisol.Shrinkage was determined on dried soil samples using an electro‐optical apparatus. The same apparatus was also used to measure porosity and pore size distribution inside the clods. For this purpose large thin sections were prepared from cracked soil samples after shrinkage measurements.Dextrans influenced shrinkage and the size distribution of clods and cracks in the two soils. The major effect was found in the Fluvisol where the arrangement of cracks was changed visibly.The dextrans caused a marked increase in total porosity in the Fluvisol but had only a small effect in the Vertisol. In both soils the pore size distribution was changed resulting in a greater number of larger pores in the dextran treated samples.
WATER FLOW IN SOIL MACROPORES I. AN EXPERIMENTAL APPROACH
Authors: GERMANN P. , BEVEN K. 
Published: July 2006

SummaryA method is proposed by which the volume of the macropore system and its effect on the infiltration capacity can be estimated using a soil water potential concept. The macropore systems of two large and undisturbed soil samples were investigated. The volumes of macropores were 0.01 and 0.045 of the sample volumes, respectively. When the samples were drained from full saturation to the point where it may be assumed that there was no more water in the macropore system, the hydraulic conductivity decreased by factors of 18 and 4.3 respectively.
THE ADSORPTION AND PRECIPITATION OF PHOSPHATE ONTO CALCITE
Authors: FREEMAN J. S. , ROWELL D. L. 
Published: July 2006

SummaryScanning electron micrographs show that the reaction products of solution phosphate and calcite are hemispherical, coral‐like growths on calcite surfaces. Electron probe micro‐analysis indicates that these are a calcium phosphate, and solution data plotted against solubility isotherms suggest that dicalcium phosphate (DCP) is formed rapidly and slowly changes to octa‐calcium phosphate (OCP). X‐ray diffraction shows that DCP and OCP are present with DCP predominating. The ratio of Ca:P in the treated calcite, after allowing for the CaCO3 present, is that in DCP, and a surface coating of OCP on DCP is likely. The exchangeability of the reacted P falls from 100 per cent for small amounts (0–10 μg P per g calcite) to a constant 30 per cent when larger amounts are present (200–1000 μg/g) resulting from the porous structure of the coral‐like growths. These cover only a small fraction of the calcite surface even when large amounts of P are present so allowing calcite to control solution pH.
APPLICATIONS OF NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY TO THE STUDY OF THE STRUCTURE OF SOIL ORGANIC MATTER
Authors: WILSON M. A. 
Published: July 2006

SummaryRecent developments in the application of nuclear magnetic resonance (n.m.r.) spectroscopy to soil science are reviewed. Progress in 1H, 13C and CP‐13C n.m.r. spectroscopy of humic substances is reported. Methods of determining the fraction of aromatic carbon in soil organic matter extracts are discussed, and methods by which structural group analysis can be carried out on in situ organic matter of whole soils are reviewed.
COPPER SORPTION BY SOILS AT LOW CONCENTRATIONS AND RELATION TO UPTAKE BY PLANTS
Authors: JARVIS S. C. 
Published: July 2006

SummaryCopper sorption was measured in 14 agricultural soils from England and Wales with a wide range of properties. Sorption from 0.01 M CaCl2was described by the Freundlich adsorption isotherm when Cu in solution was initially at 200HMand greater, but at lower initial concentrations (i. e.100fiMand less) there was a steep rise in the gradients of the isotherms. At initial concentrations of 100 JIM and less, sorption was linearly correlated to the concentration of Cu remaining in solution; the gradients of these relationships varied considerably amongst the soils and were highly correlated to soil pH. There was no correlation between either the gradients or the extrapolated values of final solution concentration at which there was no sorption of added Cu by the soils (an ‘equilibrium’ concentration), and other determined soil properties.The effect of pH adjustment on sorption varied between the 5 soils examined although, in general, there was increasing sorption with increasing pH. Extrapolated values for ‘equilibrium’ concentrations for an individual soil were higher at pH 6.0 or greater, than at pH 5.5. A large proportion of the Cu in the final solutions was apparently complexed but this varied between soils and was dependent on both pH and total concentration. There was little effect of varying pH of the final solution on these proportions in most soils.Neither extractable Cu in the soils, nor the sorption characteristics were related to availability as measured by uptake by perennial ryegrass.
ADSORPTION OF LEAD, COPPER, ZINC, COBALT, AND CADMIUM BY SOILS THAT DIFFER IN CATION‐EXCHANGE MATERIALS
Authors: ABD‐ELFATTAH ALY , WADA KOJI 
Published: July 2006

SummaryThe adsorption of Zn2+, Pb2+, Cu2+, Co2+, and Cd2+ (M2+) by soils was measured at concentrations ranging from 10‐7 to 10‐2 M in 10‐3 to 10‐2 M CaCI2. Exchange between Ca2+ and M2+, and solubility products [M2+][OH−]2 indicate that M2+ is not precipitated as hydroxide but is adsorbed on cation‐exchange sites. The proportion of selective adsorption sites with specified values of the selectivity coefficient calculated using Ca as reference ion, increased in the order montmorillonite < humus, kaolinite, < allophane. imogolite < halloysite, iron oxides. Raising the soil pH by Ca‐saturation increased both the amount and affinity of adsorption. Selectivity of adsorption increased in the order Mg, Ca < Cd, Co < Zn < Cu, Pb, and the selectivity coefficient varied from < 1 to > 10 000. The formation of the coordination complexes of heavy metal with deprotonoted OH and COOH groups as ligands is suggested as a possible mechanism of selective adsorption.
EXCHANGEABLE PHOSPHORUS, ESTIMATES OF IT FROM AMORPHOUS IRON OXIDES, AND SOIL SOLUTION PHOSPHORUS, IN RELATION TO PHOSPHORUS TAKEN UP BY MAIZE
Authors: Le MARE P. H. 
Published: July 2006

SummaryAmounts of phosphorus taken up by maize plants during 23 days from an Entisol, two Alfisols and an Ultisol from Nigeria, each with three histories of management, were related to the concentration of soil phosphorus extracted in 0.01 mCaCl2; but the relationships differed between kinds of management. Phosphorus in plants 51 days old was not related to concentration. Relationships of plant phosphorus with isotopically exchangeable phosphorus, and with phosphorus extracted from the soils by anion exchange resin, were poor in young plants but were good in the older plants, irrespective of field management. Amounts of phosphorus in the older plants were also well related to estimates of exchangeable phosphorus computed from P in solution and amounts of amorphous iron oxides extracted by ammonium oxalate from the soils, using equations derived in an earlier investigation with a larger group of soils. Thus estimates of exchangeable phosphorus made from simple measurements of the soil constituents that largely control it, and from extraction by resins, are potentially useful to indicate the ability of soils to supply phosphate to crops, and hence to guide fertilizer policies.
AGE HARDENING OF AGRICULTURAL TOP SOILS
Authors: UTOMO W. H. , DEXTER A. R. 
Published: July 2006

SummaryChanges in the strength of remoulded agricultural top soil with ageing are studied for two sandy loam soils from South Australia and a clay soil from Queensland. There is evidence of significant thixotropic behaviour in these soils around the water contents at which tillage is usually performed.For the Urrbrae soil, in which the dominant clay minerals are illite and kaolinite. the maximum thixotropic strength ratio was obtained at a water content just below the plastic limit. For the Strathalbyn soil, which contains illite and actinolite. and for the Waco soil which contains montmorillonite. the maximum thixotropic strength ratios occurred at water contents between the plastic and liquid limits.The age hardening for these soils was investigated using probe penetration, tensile strength and compression resistance measurements. The effect was still apparent after sterilization and after removal of organic matter.
MÖSSBAUER SPECTRA OF ALUMINOUS GOETHITES (α‐FeOOH)
Authors: GOODMAN B. A. , LEWIS D. G. 
Published: July 2006

SummarySynthethic goethite specimens have been prepared by a variety of experimental methods, and it has been possible to incorporate large quantities of Al ( 30 mol %) into the structure. A range of particle sizes also obtained and these were dependent upon both experimental conditions and the extent of aluminium substitution. Mössbauer spectra have been recorded for a large number of samples and show that high levels of A1‐substitution combined with small particle sizes have a dramatic effect on the magnetic properties of the mineral. The application of Mössbauer spectroscopy to the identification of secondary iron oxide phases in soils is thus complicated by aluminium substitution and some of the difficulties are discussed.
Interactions between soil drying due to plant water use and decreases in aggregate stability caused by maize roots
Authors: REID J. B. , GOSS M. J. 
Published: July 2006

SummaryIn a sandy loam soil the stability of freshly sampled aggregates, determined by turbidimetry, showed a net decrease following the growth of maize that was partly offset when the plants dried the soil over a period of 9 days. The cause of this restabilization on drying may be the adsorption onto soil surfaces of polysaccharide materials produced in the rhizosphere.