bluuebunny/crossref_metadata_2025_split huggingface dataset:
Diffuse reflectance infrared spectra of phosphate sorbed on alumina gel
Authors: NANZYO M. 
Published: July 2006

SUMMARYInfrared absorption spectra of phosphate sorbed on alumina gel were obtained by subtracting the diffuse reflectance infrared (DRIR) spectra of alumina gel from those of phosphated alumina gel. The positions of the absorption bands due to P·O stretching vibration were little affected by the change in pH and the amount of phosphate sorbed. These absorption bands were similar to those for aluminium phosphate gel. The sorption product of phosphate on alumina gel was amorphous by X‐ray diffraction. Na+ and Cl− adsorption properties of alumina gel tended towards those of aluminium phosphate gel with phosphate sorption. It was concluded that the state of phosphate sorbed on alumina gel is similar to that of aluminium phosphate gel.
The interaction of hydrazine hydrate with humic acid preparations at pH 4
Authors: ISAACSON P. J. , HAYES M. H. B. 
Published: July 2006

SUMMARYSorption isotherms were obtained by a continuous‐flow method for the interaction of hydrazine hydrate with freeze‐dried hydrogen‐, aluminium‐ and calcium‐exchanged humic acid preparations in aqueous suspensions at pH 4. The application of the continuous‐flow method is outlined and the fit of the isotherms to three sorption equations is examined. Microcalorimetry was used to measure directly the differential enthalpies of reaction as functions of sorptive concentrations. Exchange by hydrazinium ions of the exchangeable cations on the humates, chemisorption by interaction of hydrazine with humate carbonyl groups, and non‐specific sorption involving weakly‐ and strongly‐held hydrazinium ions and hydrazine molecules are shown to be the major sorption processes in these systems. The relative importance of each of these processes for the different hydrazine/humate systems is discussed, and the influence of the exchangeable cation on humate reactivity is considered.
Determination of CEC and exchangeable Ca and Mg in non‐saline calcareous soils
Authors: MISOPOLINOS N. D. , KALOVOULOS J. M. 
Published: July 2006

SUMMARYA method is proposed for determination of CEC and exchangeable cations in non‐saline calcareous soils. The saturating solution used, 0.5 d Lithium formate in 80% methanol at pH 8.2, does not dissolve CaCO3.The method is simple and less laborious than any other known method.
Modelling water flow through undisturbed soil cores using a transfer function model derived from 3HOH and Cl transport
Authors: WHITE R.E. , THOMAS G. W. , SMITH M.S. 
Published: July 2006

SUMMARYLarge undisturbed soil cores (20 cm diam. × 25–30 cm long) were irrigated at rates of 0.5–4 cm h−1 with 0.005 M CaCl2 solution labelled with 3HOH. The cores were used at varying initial water contents and flow in all cases was unsaturated. Breakthrough curves for Cl and 3HOH were markedly asymmetric and unlike those reported for columns of packed aggregates. The data could be satisfactorily described using a density distribution function of the logarithm of cumulative drainage D. The mean and standard deviation of In D were estimated by a curve‐fitting procedure from Cl and 3HOH effluent concentrations in each core. The mean pore water velocity and fraction of the soil water that participated in solute transport (the mobile volume) were also calculated.The apparent velocity of Cl movement was always greater than that of 3HOH which suggested that the mobile volume involved in convective and diffusive transport of Cl was less than that for 3HOH. We suggest that Cl and 3HOH diffused at different rates out of flowing water films in a relatively few large conducting channels into essentially immobile water within the surrounding soil matrix. The difference in mobile volume for Cl and 3HOH was used to calculate the perimeter of voids in any horizontal cross‐section of the soil through which water flowed, assuming a planar interface between the mobile and immobile water.
Fate of fertilizer nitrogen applied to grassland. II. Nitrogen‐15 leaching results
Authors: BARRACLOUGH D. , GEENS E. L. , MAGGS J. M. 
Published: July 2006

SUMMARYResults are presented from a 3‐year investigation into nitrate leaching from grassed monolith lysimeters treated with double (15NH415NO3) or single (15NH4NO3) labelled ammonium nitrate at three rates, 250, 500 and 900 kg N ha−1 a−1. Over the 3 years of the experiment, 0.14%, 3.1% and 18.1% of the applied fertilizer was recovered in the leachate at 250, 500 and 900kg N ha−1 respectively. This represented 9%, 39% and 75% of the overall nitrate leaching at the three application rates. A significant proportion of the fertilizer leached as nitrate at the three application rates was derived, via nitrification, from the fertilizer ammonium. Increasing fertilizer applications caused a rise in the leaching of both soil and fertilizer derived nitrogen, although whether the increase reflected a true priming effect was not clear.
Detection of aluminium coordination in soils and clay fractions using27 Al magic angle spinning n.m.r.
Authors: WILSON M. A. , BARRON P. F. , CAMPBELL A. S. 
Published: July 2006

SUMMARYPreliminary studies using 27Al n.m.r. of well characterized size fractions containing imogolite from an Andosol are reported. They demonstrate that 27Al n.m.r. is a useful complementary tool to X‐ray fluorescence methods for the detection of four‐and six‐fold co‐ordination of aluminium in soils. Whereas the X‐ray method depends on interpolating between standards, this is unnecessary in the n.m.r. method since four‐ and six‐fold coordinated aluminium are clearly resolved. The results demonstrate how aluminium co‐ordination changes in size fractions from the Andosol and confirm that all aluminium in imogolite is in six‐fold co‐ordination. It is also suggested that the Al‐O bond distance in imogolite is 1.82 A.
Fulvic acids: structure and metal binding
Authors: MURRAY K. , LINDER P. W. 
Published: July 2006

SUMMARYEquilibrium calculations have been carried out at 25°C and an ionic strength of 0.04 to determine the predominant metal binding sites on a well‐characterized fulvic acid for magnesium(ll), calcium(ll), manganese(ll), iron(lll), copper(ll) and zinc(II). Statistical estimates of the concentration of 14 sites are obtained from a random molecular model of fulvic acid. Protonation and metal formation constants are estimated from those of simple model ligands and corrected to the above conditions. Results indicate the importance of phthalate sites for all metals except iron(III), salicylate sites for iron(lll) and acetylacetonate sites for copper(ll). Iron (III) ions are found to form ML2 type complexes extensively. The affinity of the metal ions for fulvic acid as a whole is found to decrease in the order iron(III) > copper(II) > zinc(II) > manganese(Il) > calcium(II) > magnesium (II).
Calculation of the field volumetric water content of cracking clay soils from measurements of gravimetric water content and bulk density
Authors: HACK H.R. B. 
Published: July 2006

SUMMARYUncertainty in estimating water use in shrinking soils from changes in gravimetric water content arises from the difficulty in ensuring that samples are taken from comparable depths at different sampling times, and of identifying the correct bulk density for the conversion to volumetric water content.Equations which express the amount of water held by the same mass of soil solid matter during soil drying and shrinking are derived for two models. In one the soil properties vary continuously with depth and in the other the values are averages for layers. The models are applied to field water content measurements made in the Sudan Gezira. Systematic errors (biases) are examined and their magnitudes calculated. The maximum overestimate of gravimetric water content arising from ignoring vertical shrinkage on drying was 2.3%. The maximum overestimate of volumetric water content from ignoring volumetric contraction was 24%; this was corrected by using for all sampling times bulk densities of layers before contraction.
Seasonal variations in soil erodibility under different land‐use types in Luxembourg
Authors: IMESON A. C. , VIS M. 
Published: July 2006

SUMMARYSoil erodibility measurements for detachment by raindrop impact were made on samples collected at monthly intervals from forest, pasture and farmland sites. All sites exhibited strong seasonal variations in erodibility with maximum values occurring during the winter and minimum values in the summer. The relative erodibility of the different soils is described and the field and laboratory methods used are compared. The best time for sampling the soil for soil erodibility determinations is indicated.Erodibility is estimated from laboratory simulation experiments on undisturbed samples, from aggregate stability determinations and from field measurements with splash boards.
Proto‐imogolite allophane in podzol concretions in Australia: possible relationship to aluminous ferrallitic (lateritic) cementation
Authors: FARMER V. C. , FRASER A. R. , ROBERTSON L. , SLEEMAN J. R. 
Published: July 2006

SUMMARYProto‐imogolite allophane was found in amounts ranging from 1% to 5% in concretions and ortstein from several sandy podzols in Australia. Micromorphological observations on concretions in which allophane was the dominant clay component indicated that it had been deposited in layers during successive drying episodes to form a yellow, glassy, weakly anisotropic, fluorescent cement around sand grains. Iron oxides and organic matter were minor components of the cement. It is proposed that a proto‐imogolite sol is the mobile phase that deposits Al and Si in these concretions, and that the proto‐imogolite allophane could be a precursor of kaolinite in older concretions, and of gibbsite in leaching environments. Proto‐imogolite sols and allophane could play a similar role in the pedogenesis of kaolinite and gibbsite in concretions in freely drained ferrallitic soils.
Effect of metal toxicity on the size of the soil microbial biomass
Authors: BROOKES P. C. , McGRATH S. P. 
Published: July 2006

SUMMARYThe amount of soil microbial biomass was measured by the chloroform fumigation technique on agricultural soils which had been previously treated with different bulky organic manures. Amounts of soil microbial biomass in soils receiving sewage sludge or sludge‐containing composts were much smaller than in soils which received farmyard manure over the same period. This effect was attributed to the toxic metals present in the sludges and was readily detectable more than 20 years after the last sludge application.
The effect of mineral weathering and soil solution concentration on ESR—SAR relationships of arid and semi‐arid zone soils from Israel*
Authors: FRENKEL H. , ALPEROVITCH N. 
Published: July 2006

SUMMARYESR—SAR relationships of 623 soil samples from arid and semi‐arid zones in Israel were found to depend on soil salinity and cation exchange capacity as reflected crudely by the saturation percentage. The Gapon constant decreased as salinity increased and, for a given salinity level, it also decreased as the soil saturation percentage (SP) increased. There was no relationship between ESR and SAR for soils with low SP values (20–40) or low salinity levels (0.2–2 dSm−1). Regression equations are presented for different salinity and saturation percentage levels.
Charge properties of mixtures of minerals with variable and constant surface charge
Authors: MADRID L. , DÍAZ E. , CABRERA F. 
Published: July 2006

SUMMARYSurface charge of mixtures of lepidocrocite and illite determined by adsorption of potential‐determining and electrolyte ions is studied as a function of pH and NaCl concentration. Deviations between results obtained by both methods were a function of the illite content of the mixtures, and can be mainly attributed to coatings of hydroxyaluminium complexes on the constant charge surfaces of the clay mineral, which can react with H+ ions or release exchange sites by precipitation of well‐formed hydroxides. These coatings of aluminium complexes can cause H+ consumptions similar to those due to lepidocrocite.Some ideas are put forward for modelling charge properties of mixed systems.
Ammonium‐calcium exchange equilibria in soils and weathered pumices that differ in cationexchange materials
Authors: OKAMURA Y. , WADA K. 
Published: July 2006

SUMMARYThe retention of NH4+ and Ca2+ on soil and weathered pumice samples containing constant and/or variable charge components was measured in different NH4CI‐CaCl2 solutions. The NH4+/Ca2+ selectivity of each sample was evaluated using a quotient of the partition of NH4+ on the exchange sites and in the solution relative to that of Ca2+. It increased with decreasing pH and increasing NH4Cl‐CaCl2 concentration for a given equivalent fraction of NH4+ in the solution. These effects were quantitatively explained in terms of the changes of NH4+ and Ca2+ concentrations in the solution and in the diffuse double‐layer of the ion‐exchange material as predicted by the law of mass action and the electric double layer theory. The NH4+/Ca2+ selectivity of different exchange materials showed a similar variation among their exchange sites and increased in the order humus, allophane and imogolite (Si/Al ratio 0.5) < allophane (Si/Al ratio 1.0), montmorillonite < vermiculite, illite < halloysite. The origin of negative charge, the steric features around the exchange sites and clay‐humus interaction are suggested as being important in determining the NH4+/Ca2+ selectivity.
Thermodynamics of K‐Ca exchange in soils
Authors: GOULDING K. W. T. , TALIBUDEEN O. 
Published: July 2006

SUMMARYSurface soils from six ADAS long‐term experiments, including two on Andover series, were examined for K‐Ca exchange by exchange isotherm and calorimetric methods. Preference for K decreased in the order Worcester > Clwyd > Newport. The latter two acid soils showed ‘no preference’ and Ca preference respectively. Preference for K decreased with decreasing surface area and increasing surface charge density. The enthalpic factor favoured K preference in every soil, but the entropic factor favoured Ca preference in all but one soil. The magnitude of the enthalpic factor was greater than that of the entropic factor, resulting in K preference, in the Andover, Hanslope and Worcester soils, while the reverse was the case in the Newport soil. In the Clwyd soil, enthalpic and entropic forces were counterbalanced. These relative contributions were related to the interactions between clay mineralogy, pH and manurial history.Differential heat measurements, ‐d (ΔHx)/dx revealed exchange site heterogeneity in five of the soils. Five regions of constant ‐d (ΔHx)/dx were found, ranging from 6 to 12 kJ eq−1, a maximum of three occurring in any one soil. These were assigned to montmorillonite (two regions), mica, hydrous mica and vermiculitic mica surfaces. The 2: 1 phyllosilicate contents of the clay fractions of the whole soils calculated thus differed from those determined by XRD analysis of the clay fractions.Residual K decreased the cation exchange capacity of some of the soils but did not alter their surface areas. Its effect on K preference, K binding strength and the arrangement of the components of the system (the entropic factor) was complex.
The forms of occurrence of manganese in some acidic soils
Authors: JARVIS S. C. 
Published: July 2006

SUMMARYThe forms of occurrence of Mn were examined in some acidic surface and sub‐soils from areas of permanent grassland using chemical extractants. Despite high total contents of Mn in some of the soils and low pH, only minor proportions occurred as exchangeable Mn2+. Much larger proportions were present as reducible hydrous oxides, e.g. up to 38% and 54% of the total contents in surface and subsoils, respectively, were present as hydroquinone extractable, or easily reducible, Mn. Reducible forms of Mn were poorly correlated with other more mobile forms. Large proportions of the total Mn contents were accounted for when estimates of different fractions were calculated from differences in amounts extracted by different individual extractants, i.e. M NH4OAc, 0.2% hydroquinone, 0.1 M pyrophosphate, and ammonium oxalate. The distribution of Mn amongst the different fractions as determined by a sequential fractionation scheme differed markedly from the distribution calculated by differences. In particular, there was a marked change in form after extraction with pyrophosphate.
Mineralogical and chemical properties of weathered magnetite grains from lateritic saprolite
Authors: ANAND R. R. , GILKES R. J. 
Published: July 2006

SUMMARYMagnetite grains in lateritic saprolite have altered in situ to porous hematite (martite) grains. Hematite occurs as relatively large (∼ 1 μm) platy crystals, triangular arrays of small (0.01–0.05 μm) lathlike crystals and very small (< 100 Å) platy anhedral particles. Titanium increased in altered grains and may substitute for Fe3+ in hematite. Mn, V, Cr and Zn remained approximately constant whereas the Ni content decreased. Halloysite crystallized from soil solution within pores resulting in a marked increase in the Si and Al contents of grains.
Iron oxide mineralogy of placic horizons
Authors: CAMPBELL A. S. , SCHWERTMANN U. 
Published: July 2006

SUMMARYThe iron oxide mineralogy of 15 placic horizons from Germany, New Zealand, Belgium and U.K. was determined by differential X‐ray diffraction (DXRD). All samples examined contained ferrihydrite and goethite, lepidocrocite occurred in 10, and six contained non‐DCB‐reducible, lithogenic hematite. Ferrihydrite was most readily identified in ‘untreated minus oxalate‐treated’ DXRD patterns. Al‐substitution of goethites ranged from 4 to 13 mole %. Mean crystallite dimensions varied from 11 to 21 nm and from 6 to 21 nm for the goethite (110) and (111) lines respectively, from 7 to 51 nm for the lepidocrocite (020) line (lath thickness), and from 55 to 134 nm for the hematite (104) line. These values are typical for goethites from carbon‐rich environments with poor crystallization conditions, and for well crystalline lithogenic hematites. The DXRD method is ideally suited to the evaluation of the many selective dissolution techniques used in soil chemistry and mineralogy.
Total copper contents of Scottish soils
Authors: REAVES G. A. , BERROW M. L. 
Published: July 2006

SUMMARYThe distribution of the total copper contents of 4179 samples from 946 Scottish soil profiles is reported and the relation of copper content to some other soil variables is examined.The frequency distribution of copper contents is found to be approximately lognormal. The derived mean for the full set of data is 10 mg/kg and the normal range 0.93–110 mg/kg.The copper contents of basic and intermediate igneous rocks exceed those of acidic rocks by a factor of about 5 and among sedimentary rocks copper contents are higher in argillaceous than in arenaceous types.The general trend is for copper to increase with increasing depth and ash content and to decrease with increasing sand content.On the basis of total copper content the risk of copper deficiency is assessed to be high in 26 soil associations in Scotland and moderate in a further 10. Naturally occurring copper toxicity is unlikely to be encountered.
Soil development processes in an Aqualf‐Ochrept sequence from loess with admixtures of tephra, New Zealand
Authors: PARFITT R. L. , SAIGUSA M. , EDEN D. N. 
Published: July 2006

SUMMARYThe properties of contrasting soils occurring under a 1050–1600 mm rainfall gradient are described. The soils range, with increasing rainfall, from Typic Fragiaqualfs to Andic Dystrochrepts. Sand mineralogy of these soils indicates that they have formed in essentially similar parent materials consisting largely of quartzo‐feldspathic loess with admixtures of rhyolitic and andesitic tephra.The Fragiaqualfs have high bulk density, impeded drainage in winter, degraded chlorite, argillic horizons, halloysite and vermiculite. The Dystrochrepts have lower bulk density, free drainage, ferrihydrite, allophane, humus‐(Al, Fe) complexes and no argillic horizons.An hypothesis to explain differences between these soil groups proposes that the dense horizons in the Fragiaqualfs arise largely from hydraulic suctions exerted by roots during periods of high summer water deficits. The consequent loss of porosity leads to impeded drainage in winter causing gleying and enhanced clay formation. In the Dystrochrepts the summer deficits are lower, consequently the soils have lower bulk densities and remain free draining.
Quantitative determination of calcite and dolomite in soils by X‐ray diffraction
Authors: ULAS M. , SAYIN M. 
Published: July 2006

SUMMARYAn X‐ray diffraction method using CaF2 as internal standard was applied to the carbonate‐rich soils of the ukurova and Göksu plains in Southern Turkey. Soil samples, freed from carbonates, were used as matrices and a separate calibration curve was prepared by known carbonate additions for each soil series. Statistical tests showed that one calibration curve was sufficient to determine calcite and dolomite contents of seven soil series. Particle orientation was an important factor for accurate analyses and a test, using the known addition method, should be carried out before using a matrix material other than carbonate‐free soils.
Soil structure and potassium supply. I. The release of potassium from soil aggregates to Ca‐resin
Authors: HEMING S. D. , ROWELL D. L. 
Published: July 2006

SUMMARYPotassium release from saturated spherical aggregates of three clay soils to Ca‐resin was measured and compared with release in suspensions (Talibudeen et al., 1978). The diffusion coefficient for K was calculated from measurements of the tortuosity factor using 36Cl, volumetric water content and buffer power. Release of K is in the order: suspensions >2–3 mm > 6–8 mm aggregates. A computer model incorporating diffusion analysis and release of K shows that in the aggregates the rapidly diffusing exchangeable K, Kex, is best measured by the extrapolated intercept of a desorption isotherm (24 h equilibration), and is 8–55% less than that extracted by NH4OAc leaching. Release of K within the aggregates (Knex, a fraction approximating to Talibudeen's peripheral K) is delayed until after about 95% of Kex has been depleted which takes 1–2 days. The effective release rate of Knex inside the aggregates is ∼ 17% less than in soil suspensions. Diffusion imposes only small limitations on the release from aggregates of Knex. This rate of release depends on the frequency of resin changes.
Soil structure and potassium supply. II. The effect of ped size and root density on the supply to plants of exchangeable and non‐exchangeable potassium from a chalky boulder clay soil
Authors: HEMING S. D. , ROWELL D. L. 
Published: July 2006

SUMMARYA model based on measurements of potassium release from spherical aggregates (Heming & Rowell, 1985, Part I) has been used to predict release from larger aggregates, for longer times, drier soils and varying diffusion coefficients. The model has been adapted to predict supply to a single root from a soil cylinder and compared with measured uptake by onions. A ‘supply index’ shows likely restrictions in the availability of exchangeable K and in the rate of supply of non‐exchangeable K resulting from diffusion limitations over a 4 week period for (i) aggregates covered with a dense roots system, and (ii) roots growing at known densities. For this period diffusion alone should not limit exchangeable K uptake in the field if the root density is at least 3.5 cm/cm3: at 0.9 cm/cm3 about 50% may be unavailable. The supply rate of non‐exchangeable K increases with root density and may be important for high‐demanding crops in dry seasons.