bluuebunny/crossref_metadata_2025_split huggingface dataset:
STABILITY OF FERRIC PHOSPHATES
Authors: McLAUGHLIN J. R. , SYERS J. K. 
Published: July 2006

SummaryEssentially congruent dissolution of colloidal ferric phosphate, metastrengite, and strengite was observed at pH 1.5 during 25 days. In contrast, preferential release of P to solution was obtained at pH 6.0. Dialysis of dried preparations of these three materials against hydrous ferric oxide gel (Fe gel) resulted in the loss of 9.0, 3.0, and 0.4 per cent of total P, respectively, during 20 days. A wet preparation of colloidal ferric phosphate released 17 per cent of total P during the same time. During dialysis, all ferric phosphates assumed a brownish colour. Electron microscopy revealed the presence of an appreciable quantity of short‐range order material surrounding crystals of strengite following dialysis. These observations, coupled with the decrease in type ratio, demonstrate that an Fe gel coating forms on the ferric phosphates during dialysis. The results are discussed in terms of the likely stability of ferric phosphates in soils.
USE OF A CHEMOSTAT TO STUDY DECOMPOSITION OF WHEAT STRAW IN SOIL SLURRIES
Authors: LYNCH J. M. , GUNN K. B. 
Published: July 2006

SummaryThe breakdown of wheat straw in slurries of soil was studied under controlled physical conditions. In the absence of oxygen there was a reduction in the redox potential and pH of the slurries and there were concomitant increases in the concentrations in solution of total carbon compounds, acetic acid, iron and manganese. The temperature coefficients (Q10) for these reactions and processes were between 2.5 and 2.9 but they did not take place in the presence of oxygen nor when nitrate was added. When no straw was mixed with the soil, similar changes took place but were much less pronounced and no acetic acid was formed.
MUCILAGES AT THE ROOT SURFACE
Authors: OADES J. M. 
Published: July 2006

SummaryThe mucilaginous material, which forms a layer several microns thick around plant roots, contains a glucan, a polyuronide, and heterogeneous polysaccharides. An assessment is given of the effects of the mucilage on ion and water uptake by plants, on soil chemical and physical properties including aggregation, and as an energy source for microorganisms. It is concluded that these effects are important but that more chemical and physical studies of plant mucilage are required.
SOIL ALKALINITY. I. EQUILIBRIA AND ALKALINITY DEVELOPMENT
Authors: MASHHADY A. S. , ROWELL D. L. 
Published: July 2006

SummaryTheoretical relationships between pH, CO2 partial pressure and alkalinity (bicarbonate + carbonate concentrations) have been shown to apply to solutions and calcite and soil suspensions.The exchange of Na onto three Ca clays shows that Ca is preferred but with negative free energies of exchange. With decreasing total electrolyte concentration, the preference for Ca increases, so that only when the concentration is above 10‐3M will significant amounts of exchangeable Na be found in soils. The preference for Ca is illite > montmorillonite > vermiculite.Dilution of the mixed Na‐Ca clay suspensions causes exchange, desorption of Na and. in some cases Ca. This desorbed or ‘alkaline’ Na (and Ca) is replaced by H some of which attacks the clays. The apparent hydrolysis coefficient, KG = H adsorbed (Na)/Na adsorbed (H), varies between 5 and 9 × 105, increases with increase in electrolyte concentration and varies in the order vermiculite > illite > montmorillonite. The concentration of alkaline Na + Ca increases with increasing ESP, and with clay type in the same order as the KG values. The pH calculated from the alkaline Na + Ca, assumed equal to the alkalinity was equal to measured values except for montmorillonite where the calculated values were low. Magnesium release by acid attack of the montmorillonite may explain the differences.Vermiculite rich soils will be most likely to accept exchangeable Na and to hydrolyse and develop alkalinity.
ETHER‐SOLUBLE HYDROLYSIS PRODUCTS IN HUMIC AND FULVIC ACIDS
Authors: ANDERSON H. A. , HEPBURN A. , SIM A. 
Published: July 2006

SummaryThe major ether‐soluble products from the hydrolysis of humic and fulvic acids include levulinic, succinic and fumaric acids, accompanied by more variable amounts of 4‐hydroxy‐, 3‐methoxy‐4‐hydroxy‐, and 3,4‐dihydroxybenzoic acid. 3,5‐Dihydroxy‐benzoic acid was not detected in the hydrolysates examined.
IODINE IN SOIL PROFILES IN RELATION TO IRON AND ALUMINIUM OXIDES AND ORGANIC MATTER
Authors: WHITEHEAD D. C. 
Published: July 2006

SummaryThe iodine content in successive 10 cm horizons of eighteen soil profiles from England and Wales was determined and correlated with contents of‘free’ aluminium and iron oxides (oxalate‐soluble) and organic matter.The pattern of change in iodine content with depth varied considerably with soil type. In the rendzina soils, the content was relatively high in the surface 10 cm but declined markedly with depth. In the podsols, iodine was low at the surface but increased in the B horizon: in one of these soils an iron pan of about 1 cm thickness had an iodine content as high as 37.6 mg/kg. In two soils derived from Ordovician, and one from igneous, rock material, the iodine content was relatively high (up to 25 mg/kg) with maximum values at intermediate depths. In contrast, soils derived from river alluvium and from lowland clays generally had low iodine contents (< 6 mg/kg) which showed little variation with depth in the profile. In a peat soil the iodine content was relatively high in the horizons above 60 cm but was low (1. 3 mg/kg) in the underlying clay.In all 154 samples from the eighteen sites, iodine content was closely correlated with oxalate‐soluble aluminium (r= 0.834***) but not with oxalate‐soluble iron (r= 0. 35) or organic matter (r= 0.37). However, in the five most acidic soils, with pH below 4. 8, the iodine content was more closely correlated with iron than with aluminium.
COMBINED EFFECTS OF MOISTURE CONTENT PRIOR TO COMPACTION, COMPACTIVE EFFORT AND RAINFALL QUANTITY ON SOIL CRUST STRENGTH
Authors: HEGARTY T. W. , ROYLE SHEILA M. 
Published: July 2006

SummaryFour levels of mechanical compaction (C) and six levels of subsequent simulated rainfall (R) were applied in all combinations to soil samples at five levels of moisture content (M) in the laboratory. After treatment, the soils were air‐dried to give uniform surface moisture contents and the crust strength was determined with a downward‐acting penetrometer. Almost 90% of the variation in peak penetration force was accounted for by an equation containing terms in R, CR, CM and CM2.
DISTRIBUTION OF SOME CHEMICAL ELEMENTS IN THE SOILS OF NORTH WEST PEMBROKESHIRE
Authors: BRADLEY R. I. , RUDEFORTH C. C. , WILKINS C. 
Published: July 2006

SummaryTotal amounts of Mn, Fe, Ni, Cu, Zn, As, Bt, Rb, Si, Y, Zr and Pb were determined in soil samples from approximately 250 profiles. Examples of automatically plotted maps show the distribution of some of these elements in topsoils and subsoils. Element distribution in the soils is related to land units based on underlying rock‐type and air photograph interpretation; these units distinguish soils of different lithological and drainage status and many are dominated by a single soil subgroup. Agricultural and pollution aspects of the work are discussed. The survey indicates the present levels of the elements, and may be used as a comparison in future pollution studies.
SOIL SAMPLER WITH RETRIEVABLE LINER
Authors: BLACK J. H. , RAINES M. G. 
Published: July 2006

SummaryA simple, hand‐operated soil sampler based on commercially available drainpipe is described. The sampler is robust, avoids cross‐contamination of samples and can penetrate to a depth of three metres. The detailed design of, and a procedure for using, the sampler are given.
A MÖSSBAUER SPECTROSCOPIC STUDY OF THE EFFECT OF pH ON THE REACTION BETWEEN IRON AND HUMIC ACID IN AQUEOUS MEDIA
Authors: GOODMAN B. A. , CHESHIRE M. V. 
Published: July 2006

SummaryMössbauer specttoscopy has been used to provide information on the effect of pH on the nature of the complexes formed between iron and humic acid. At an initial suspension pH greater than 3 the iron occurs in the ferric form, although it is difficult to assess to what extent it is in combination with organic matter. On lowering the pH, iron is reduced with a considerable proportion of the ferrous iron entering solution, partly as a solvated ion and partly as complex forms. Raising the pH leads to re‐oxidation and the precipitation of a considerable proportion of the iron in an inorganic form with Mossbauer parameters similar to those of β‐FeOOH. No evidence was obtained for Fe(III) in solution or for Fe(II) in any form at pH values greater than 4.
VARIABLE ATMOSPHERE DTA IN IDENTIFICATION AND DETERMINATION OF ANHYDROUS CARBONATE MINERALS IN SOILS
Authors: WARNE S. St. J. , MITCHELL B. D. 
Published: July 2006

SummaryThe value of modem commercial DTA equipment in the identification and determination of anhydrous carbonate minerals can be greatly improved by incorporating a controlled‐atmosphere (carbon dioxide) technique. The unproved peak definition and increased height enables the detection of carbonate minerals at concentrations of the order of 0.25 per cent by weight in a 50 mg sample. Further, the related changes in temperature of the decomposition reaction peaks provide additional information for the identification of carbonate mineral reactions. The method has particular application in mineralogical and pedological investigations.
THREE EFFECTS OF TEMPERATURE ON THE REACTIONS BETWEEN INORGANIC PHOSHATE AND SOIL
Authors: BARROW N. J. 
Published: July 2006

SummaryPhosphate was added to soil, incubated at a range of periods and of temperatures, and the rate of desorption was measured at several solution: soil ratios at 25°C. One sample was incubated at a high temperature for several days and the rate of desorption was measured at 5, 15, 25 and 38 °C. A regression approach was used to describe the results which were interpreted in terms of a model in which phosphate was present (a) in solution, (b) adsorbed in equilibrium with the solution, and (c) firmly held.When neither adsorption nor desorption occurred, the phosphate concentration in solution increased with temperature. This was interpreted as an effect of temperature on the position of the equilibrium between solution phosphate and adsorbed phosphate. The direction of the effect indicates that adsorption was exothermic. When either adsorption or desorption occurred the rate increased with temperature and to a similar extent. For both reactions, the change in heat content was small. Thus, while temperature affected the rate of interchange between adsorbed and firmly‐held forms it should not affect the position of the equilibrium between these forms.
ROTHAMSTED STUDIES OF SOIL STRUCTURE 1.: PURPOSE OF THE PROJECT, SOILS SELECTED, AND GENERAL CONCLUSIONS
Authors: CURRIE J. A. , BULLOCK P. , THOMASSON A. J. 
Published: July 2006

SummaryThe agricultural background, morphology, and classification of soils from the Hans lope, Ragdale, Evesham, Denchworth, Flint and Salop series are presented together with basic analytical measurements of particle size and chemistry and with some details of the field water regimes. This information serves as essential background to other studies of soil structural properties as they relate to management of the same soils.
ROTHAMSTED STUDIES OF SOIL STRUCTURE IV.
Authors: CURRIE J.A. 
Published: July 2006

SummaryPorosity and gas diffusion have been measured within dry crumbs sieved from the horizons of one soil from each of the Hanslope, Ragdale, Evesham, Denchworth, Flint and Salop series. Crumb porosities, ɛc, ranged from 0.19 to 0.33, dimensionless gas diffusivities, Dc/D0, from 0.015 to 0.098, and the effectiveness of unit pore space for diffusion, given by αc= (Dc/D0)/ɛc, from 0.06 to 0.29. Values of ɛc and Dc/D0 were used to calculate complexity factors kc for the crumb pores. The results are discussed in terms of soil texture, pore size, ease of soil management, and the frequency and intensity of wetting and drying of the soil in each horizon. None of the results suggests why the soils of the Ragdale, Denchworth and Salop series should be more difficult to manage than the others.
THE MEASUREMENT OF SOIL‐WATER HYSTERETIC RELATIONSHIPS ON A SOIL MONOLITH
Authors: TZIMAS E. 
Published: July 2006

SummarySoil water properties of an undisturbed uniform soil monolith were studied under laboratory conditions. Water content, hydraulic conductivity and soil water suction were measured simultaneously on a full cycle starting from saturation, drying to a small water content and then wetting until saturation was reached again.The results showed clearly the hysteretic nature of the relations between water content and suction and between hydraulic conductivity and suction, but not between hydraulic conductivity and water content.
THE EFFECT OF POLY(VINYL ALCOHOL) ON THE CRUST STRENGTH OF SILTY SOILS
Authors: PAGE E. R. 
Published: July 2006

SummaryFourteen samples of soils were collected from localities in England where crusting and consequent depression of seedling emergence had been recorded. Natural aggregates of these soils were sprayed with poly(vinyl alcohol) (PVA), subjected to simulated heavy rain, and dried under IR lamps. In most soils, aggregate stability was enhanced by increasing applications of PVA and crust formation was prevented. Some soils, however, were unresponsive to PVA and crusts formed whether or not it was applied.Responsive and unresponsive soils did not differ in particle size distribution, or porosity characteristics. Removal of iron oxides and organic matter did not alter their adsorption characteristics towards PVA. Unresponsive soils, however, were found to have the mineral chlorite as a major component and it is suggested that PVA is unable to bind particles together when the surfaces presented for adsorption of PVA consist of gibbsite, the interlayer material of chlorite.
ADSORPTION ISOTHERMS: SHOULD THEY BE SPLIT?
Authors: POSNER A. M. , BOWDEN J. W. 
Published: July 2006

SummaryLangmuir adsorption isotherms are unlikely to be appropriate when applied to the adsorption of charged phosphate ions on charged oxide surfaces. It is more likely that the adsorption model proposed by Bowden et al. (1973, 1974 and 1977) for adsorption on variable charge variable potential surfaces will be applicable. Theoretical isotherms were calculated from this model for a series of pH values and ionic strengths. It is shown that these isotherms can be split into two or more Langmuir isotherms in much the same way as has been done by various authors for experimental isotherms. The parameters of the Langmuir isotherms behave in the same way as those derived from the experimental isotherms. The charging characteristics of the theoretical isotherms are also similar to that observed experimentally.Because the model which is based on a single type of adsorption site is closely similar to the experimental isotherms, it is erroneous to split the isotherms into a series of Langmuir isotherms unless there are good a priori reasons.
FREEZING AND MELTING TEMPERATURE HYSTERESIS OF WATER IN POROUS MATERIALS: APPLICATION TO THE STUDY OF PORE FORM
Authors: HOMSHAW L. G. 
Published: July 2006

SummaryA theory is developed for the influence of pore form on the equilibrium freezing and melting temperatures of water in porous materials. This is supported by calorimetry and uses the hysteresis between freezing and melting temperatures for two clays and undried synthetic organic textile fibres in which the pore geometry is that of intersecting cylinders.For most water‐saturated clay systems, analysis of the low temperature endotherms gives a better appreciation of the pore size distribution than analysis of the exothermic data, unless the width of rectangular pores is known.
FORMATION, COMPOSITION AND STRUCTURE OF HYDROXY‐ALUMINOSILICATE IONS
Authors: WADA SHIN‐ICHIRO , WADA KOJI 
Published: July 2006

SummaryFormation of hydroxy‐Al (HA) and hydroxy‐aluminosilicate (HAS) ions was studied in solutions of A1C13, orthosilicic acid and NaOH. Evidence for incorporation of Si into HA is that HA retarded the development of silicomolybdate colour and Si was retained by a cation‐exchanger. The reaction is believed to be mainly a condensation reaction between the hydroxyl groups in Al–OH–Al and Si–OH groups. The HAS with Si/Al ratio 0.3–0.6 showed infrared spectra similar to allophane‐like constituents in Ando soils.
LONG‐TERM CHANGES IN SOIL MACRO‐ AND MICROMORPHOLOGICAL PROPERTIES UNDER THE INFLUENCE OF PEAT DEBRIS
Authors: COLLINS J. F. , COYLE E. 
Published: July 2006

SummaryField morphological examination and thin section observations were made to document the effects of varying additions of acid peat debris to a mineral topsoil after a period of 25–30 years. Additions up to 3 cm improved soil physical properties and faunal activity relative to the unamended topsoil. Additions of 5–8 cm caused acidification, structural alteration and iron mobilization. Further additions, ranging up to 30 cm, caused progressive increase in acidification, reduction, structural collapse, faunal inactivity, etc. The formation of thick humus coatings (organans) and diffuse subsurface impregnations in the mineral soil is highlighted.
A COMPARISON OF THE SUITABILITY OF TWO SOILS FOR DIRECT DRILLING OF SPRING BARLEY
Authors: PIDGEON J. D. 
Published: July 2006

SummaryA long‐term tillage experiment near Edinburgh on two soils types, one suitable for direct drilling and the other not, allowed comparisons to be made of soil responses to tillage and traffic.For all tillage treatments tests, bulk density was always higher and air capacity lower on the soil unsuitable for direct drilling. Cone resistance, while dependent on treatment, was independent of soil type, The results suggested that compactability influences soil suitability for direct drilling.Differences between soils in compactability were greater under direct drilling than other tillage treatments or in laboratory tests, probably due to the interaction of traffic and drainage regime. Drainage was not impaired under direct drillingon either soil type, despite significant reductions in macro‐porosity. Crop yields and root distribution in relation to soil physical conditions suggested the increased importance of subsoil conditions in direct drilling compared with ploughing systems.
WATER FLOW IN SOIL MACROPORES II. A COMBINED FLOW MODEL
Authors: SEVEN K. , GERMANN P. 
Published: July 2006

SummaryThis paper presents a one‐dimensional model of bulk flow in a combined micropore/macropore system, which has been developed as a result of the experimental work described in Part I. The problems posed by the presence of macropores to model development and validation are discussed and one exploratory model formulation is described. The results of several simulations are presented and used to demonstrate the effect of macropores on infiltration rates in soils of different hydraulic conductivity.
CROSS POLARISATION 13C‐N.M.R. SPECTROSCOPY OF SOME GENETICALLY RELATED NEW ZEALAND SOILS
Authors: WILSON M. A. , BARRON P. F. , GOH K. M. 
Published: July 2006

SummaryCross polarisation 13C‐n.m.r. spectra of seven New Zealand soils have been determined. Some of the soils are genetically related. The results show that the aromaticity of a soil may vary widely from soil to soil even when the parent material and vegetation are similar. The youngest of the soils examined (Hokitika, 300 years), was highly aromatic, and the oldest soil (Okarito, 22,000 years) was more aliphatic.
PORE CHARACTERISTICS OF SOILS FROM TWO CULTIVATION EXPERIMENTS AS SHOWN BY GAS DIFFUSIVITIES AND PERMEABILITIES AND AIR‐FILLED POROSITIES
Authors: BALL B. C. 
Published: July 2006

SummaryGas diffusivity and permeability, and air‐filled porosity, were measured in undisturbed soil cores at six water potentials between ‐2 kPa and oven dryness. All increased as water potential fell. In silt loam at 30 to 80 mm depth, relative diffusivity and air permeability at ‐2 kPa were 0.0013 and 5 × 10−8cm2 after direct drilling, and were 6 and 15 times greater respectively after ploughing, presumably because of the larger volume of air‐filled large pores in the ploughed soil. These pores may also have been more continuous or less tortuous than in the direct drilled soil. However, at equal air‐filled porosities up to 0.18 v/v, the pores were apparently more continuous and less tortuous in the direct drilled than in the ploughed soil. In the direct drilled silt loam at any given matric potential, air‐filled porosity, gas diffusivity and permeability within and below the previously ploughed layer were isotropic. In clay loam at 30 to 80 mm depth gas diffusivity and permeability at ‐2 kPa were greater than in the silt loam irrespective of tillage but increased less on oven drying.
THE CORRECTION OF IN SITU TENSIOMETER READINGS FOR OVERBURDEN PRESSURES IN SWELLING SOILS
Authors: TOWNER G. D. 
Published: July 2006

SummaryAn outline is given of some basic concepts relevant to a proper understanding of overburden pressure. It is shown that for swelling soils the overburden pressure must be known in order to infer water contents from in situ tensiometer measurements, but that it need not be known for the determination of hydraulic potentials from tensiometer readings.
EFFECT OF LIVING ROOTS OF DIFFERENT PLANT SPECIES ON THE AGGREGATE STABILITY OF TWO ARABLE SOILS
Authors: REID J. B. , GOSS M. J. 
Published: July 2006

SummaryThe influence of root growth and activities on soil aggregate stability was investigated using five crop species and two soils. Single plants were grown in pots for 6 weeks or less to minimise any possibility of changes in aggregate stability caused by decomposition of dead roots. Planted soils were compared with fallow controls. Aggregate stability was estimated by a turbidimetric technique (used for fresh and air‐dried samples) and by wet sieving (used for air‐dried samples only).Root growth of perennial ryegrass and of lucerne for 42 days was generally associated with increases in aggregate stability whether the soil was tested in a fresh or an air‐dried condition. These beneficial effects were associated with periodate‐sensitive (probably polysaccharide) materials produced in the rhizosphere.Growth of maize, tomato and wheat roots for 25 days decreased the stability of fresh soil aggregates, although the effects of tomato and of wheat were not consistent. However, the deleterious effects of these three species on aggregate stability were not apparent after air‐drying. The restabilization of maize soils (relative to fallow controls) on air‐drying appeared to be caused by increased stabilization by periodate‐sensitive materials.The results suggest that the growth and activities of living roots may be a major factor controlling the overall direction and magnitude of changes in aggregate stability under arable or ley crops.