bluuebunny/crossref_metadata_2025 huggingface dataset:
ORGANO‐MINERAL FRACTIONS OF A CLIMOSEQUENCE OF SOILS IN NEW ZEALAND TUSSOCK GRASSLANDS
Authors: TATE K. R. , CHURCHMAN G. J.
Published: July 2006

The organo‐mineral fractions of seven New Zealand topsoils, which are members of a climosequence, were isolated by ultrasonic dispersion in water and separated into sand‐, silt‐ and clay‐size fractions. Several soils contained stable aggregates of mainly silt‐size, comprising cemented clay‐size particles. The tendency of one soil (McKerrow) to form larger aggregates of sand‐size was explained by its distinctive mineralogy.

Total organic carbon and total nitrogen were used to indicate the amounts of organic matter in the organo‐mineral fractions. The degree of humification of the organic matter was assessed by a pyrolysis‐gas chromatography technique, which proved superior to the more conventional C/N method.

In the sand‐size fractions the climate, and especially annual precipitation, strongly influenced the amounts of organic matter, whereas in the clay‐ and silt‐size fractions it was the composition of the organic matter that was influenced.
SOIL VARIABILITY AND RECONNAISSANCE SOIL MAPPING. A STATISTICAL STUDY IN NORFOLK
Authors: NORTCLIFF S.
Published: July 2006

The incorporation of measures of soil variability at the reconnaissance stage of soil survey is considered as a possible alternative to, or additional feature of, present procedures. A straightforward hierarchical sampling design based upon the major parent materials of the upland section of the study area and associated analysis of variance model are described. This allowed the estimation of scale components for five levels of the sampling design at separation distances from over two kilometers down to five meters. Principal components analysis is used to economise on the number of variables for further analysis. Analysis of the pattern of principal component scores shows the first six components to have distinctive variability patterns both within and between strata. It is concluded that present soil survey procedures take too little account of soil variability patterns, and that inclusions of such information at the reconnaissance stage would greatly improve the detailed survey.
MINERALOGY, GENESIS AND CLASSIFICATION OF FERRUGINOUS SOILS OF THE EASTERN MYSORE PLATEAU, INDIA
Authors: RENGASAMY P. , SARMA V. A. K. , MURTHY R. S. , MURTI G. S. R. KRISHNA
Published: July 2006

The relationship of geomorphic and climatic history and formation of the ferruginous soils, formed on the acidic Peninsular Gneiss, of the Mysore Plateau, India, is discussed. The profiles studied are found on two different land systems. The soils of the older, fairly smooth landscape are composed of colluvium over truncated laterite profiles, with a gravel layer and a prominent kaolin layer over the weathered rock. These soils show an accumulation of pedogenic haematite grains in the sand fraction and have considerable kaolinite and amorphous ferri‐aluminosilicate minerals in the clays.

The soils of the younger, rugged landscape have similar clay mineralogy, but do not have a gravel layer, or haematite grains. The influence of the coarse‐grained parent rock is seen in the large amounts of quartz gravel. The absence of granulation is attributed to lack of accumulation of iron.

The soils have been formed in an earlier, more humid climate than prevails today. The original laterite profiles were formed on a plane surface, and subsequent change in climate has led to change in the land forms and dissection. Truncation of the profiles was followed by deposition of red colluvium over the resistant ferruginous layer.

These ancient soils do not fit the criteria for Oxisols in the U.S. classification, but fit well in the French system as ‘Sols Ferrallitiques’, subclass ‘fiablement désatures en (B)’. The soil from a low lying area, formed from colluvium under hydromorphic conditions. is classified as‘Vertisols et Paravertisols'.
LEAD POLLUTION IN AGRICULTURAL SOILS
Authors: COLBOURN P. , THORNTON I.
Published: July 2006

High concentrations of lead, copper, zinc and cadmium, are reported in agricultural soils of the southern Peak District in association with mining and smelting sites. A reliable background range of lead concentrations in non‐contaminated soil was established and the relative topsoil enhancement (RTE) ratio was found to be a useful index of pollution. A wide range of amounts of lead was extracted from soils by dilute nitric acid; the higher end of the range may result from free lead oxides being present in some polluted soils. The amount of lead extracted also depended on the composition of the soil, a soil containing vermiculitic clay minerals maintained a very low lead concentration in solution. The effects of site history, weathering and redistributive processes are discussed.
THE IMPREGNATION OF WET PEAT FOR THE PRODUCTION OF THIN SECTIONS
Authors: FITZPATRICK E. A. , GUDMUNDSSON T.
Published: July 2006

A technique is described to replace the water in peat by acetone prior to impregnation with resin. The peat is exposed to the vapour of aqueous acetone of increasing concentration up to 100 per cent acetone. After impregnation with resin, high quality thin sections can be obtained.
THE SURFACE TENSION OF SOIL WATER
Authors: TSCHAPEK M. , SCOPPA C. O. , WASOWSKI C.
Published: July 2006

Because of their organic matter content, the surface tension of water of soils is about 8 to 9 erg cm ‐2 (8 to 9 × 10 ‐7 J cm ‐2) less than that of pure water. It is estimated that the surface tension of soil solution is 63–64 erg cm ‐2 in the surface soils studied.
TOWARDS AN OBJECTIVE CLASSIFICATION OF SOIL STRUCTURE
Authors: THOMASSON A. J.
Published: July 2006

A classification of structural condition in surface soils is proposed, based on the volumes of two categories of pore size, termed air capacity (pores greater than 60 μm diameter) and available water (pores of 60 to 0.2 μm diameter.

Relationships of pore volumes to particle size class, organic carbon content and soil water regime are examined. Soil structural conditions are mainly affected by water regime and organic carbon and, apart from the extremes of sandy or clayey textures, less influenced by particle size distribution.
INTERACTION OF SOIL AND MANKIND IN BRITAIN
Authors: BRIDGES E. M.
Published: July 2006

Man's initial occupation of the British landscape was subject to broad physical constraints which are still apparent from archaeological evidence and place‐name interpretation. The influence of soils in initial settlement establishment is seen to be difficult to interpret several thousand years later as environmental conditions, including soils, have changed. Conversely, man's effect on the soils surrounding his settlements is evident through agricultural and other activities. These activities have increased in their impact with the passage of time. A combination of historical geography and soil studies shows man's interaction with the country's most basic resource.
YTTRIUM AND ZIRCONIUM AS GEOCHEMICAL GUIDE ELEMENTS IN SOIL AND STREAM SEDIMENT SEQUENCES
Authors: MURAD ENVER
Published: July 2006

Yttrium and zirconium concentrations, taken as representative for the abundances of the heavy minerals xenotime and zircon in soils and stream sediments of the Schwarzach valley in eastern Bavaria, were found to be closely correlated, the Zr/Y ratio averaging 9.7 (r = 0.90 for 73 samples). The uniformity of this ratio ‐ despite considerable local variations of the individual concentrations—indicates its suitability for tracing back soils and sediments to the parent rocks.
SOIL LAYERS IN MIRES: FUNCTION AND TERMINOLOGY
Authors: INGRAM H. A. P.
Published: July 2006

Two recent North American soil classification schemes embodying criteria for distinguishing layers in mire soils are criticised as being artificial and unrelated to function. In these soils, the most important functional processes are hydrological. The two‐layer hypothesis of K. E. Ivanov, involving a set of hydrological differences and associated biological characteristics, is accordingly advocated as a basis for a natural scheme of layering, in which a surface layer, the ‘active layer’, is distinguished from the ‘inert layer’ below. Since both expressions are deemed inadmissible, it is suggested that the upper layer be termed the acrotelm and the lower layer the catotelm. A two‐layered mire soil should be termed diplotelmic and one without an acrotelm, haplotelmic. Basic definitions for all 4 terms are provided. Possible applications to eroded or reclaimed mires are briefly discussed.
THE EFFECT OF MOLECULAR SIZE ON DIFFUSION CHARACTERISTICS IN SOIL
Authors: BARRACLOUGH D. , NYE P. H.
Published: July 2006

Measurements of the apparent self‐diffusion coefficients of, poly(vinyl pyrrolidone) mol. wt. 40 000, polyethylene glycol) mol. wt. 4000, and chloride ion, were used to determine the effect of molecular size on diffusion characteristics in soil. The measurements were carried out on the same soil, at a range of moisture contents, and indicated that the mobility of large molecules in soils depends, to a large degree, on the inter‐aggregate pores. Any drop in moisture content which caused these pores to drain, produced a sharp decrease in the apparent self‐diffusion coefficient of the poly(viny) pyrrolidone) 40 000. Neither poly(ethylene glycol) 4000 nor chloride, which exhibited similar diffusion characteristics, were as sensitive to variation in moisture content. The results are interpreted in terms of certain parts of the pore volume being inaccessible to the diffusing molecule. Possible reasons are outlined.
PALEOsolS DEVELOPED ON CHALKY BOULDER CLAY IN ESSEX
Authors: STURDY R. G. , ALLEN R. H. , BULLOCK P. , CATT J. A. , GREENFIELD S.
Published: July 2006

Soils with paleosol features occur at the surface on the Chalky Boulder Clay in the Chelmsford area, Essex. Their particle size distribution, micromorphology and sand, silt and clay mineralogy indicate periods of weathering, clay illuviation and hydromorphism before deposition of loess in the Late Devensian. These periods are provisionally related to the Ipswichian and/or Hoxnian Interglacials.
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

This 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

Analysis 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

A 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

The 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

Mixtures 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

Amorphous 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

The 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

Two 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

A 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

Scottish 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

The 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

Soil 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

The 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

A 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

Scanning 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

Recent 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

Copper 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

The 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

Amounts 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

Changes 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

Synthethic 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

In 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.
Diffusion of coefficients of carbon dioxide, nitrous oxide, ethylene and ethane in air and their measurement
Authors: PRITCHARD D. T. , CURRIE J. A.
Published: July 2006

Binary diffusion coefficients were measured by a steady‐state method in which a gas was introduced at a constant rate into one end of a tube through which it moved by mass flow and diffusion into a semi‐infinite volume of air. The Stefan correction for mass flow was modified to allow for initial gas concentrations < 100 per cent, conferring four advantages: errors in the total flow rate are relatively unimportant; density gradients are small so that convection is inhibited; the gas analysis is more sensitive; and diffusion coefficients are measured at the small concentrations that are encountered in soils. Measured diffusion coefficients (cm2 s−1 at NTP) in air for carbon dioxide (0.139), nitrous oxide (0.143), ethylene (0.137) and ethane (0.128) are compared with measured and calculated values from other sources.
Ionic strength of soil solution and its effect on charge properties of some New Zealand soils
Authors: BLACK A. S. , CAMPBELL A. S.
Published: July 2006

Selected horizons from six New Zealand soils under permanent natural vegetation, four of which form a development sequence, were chosen to provide variations in organic matter, phyllosilicate clay mineral and short‐range ordered aluminosilicate (allophane) contents. The ionic strength of the soil solution (μ) extracted from the soils of the development sequence was low, being always less than 0.005. For all horizons of the six soils, the negative charge changes linearly with μ1/2 within the ionic strength range of 0.001 to 1. The change was negligible for the least weathered and leached soil, indicating that it contained mainly permanently charged colloids. As soil development increased and/or the components carrying variable charge increased in amount, the change in charge with ionic strength increased. A regression equation showed a strong relationship between change in negative charge with ionic strength and organic carbon and oxalate‐extractable A1 (R2=0.976). This equation was tested by predicting observed changes in charge with ionic strength for a second selection of soils. The change in positive charge with ionic strength was correlated with oxalate‐extractable A1 (r2=0.914). The results are discussed in relation to measurement of soil charge and iron movement in soils.
Potential role of soil density and clay mineralogy in assessing the suitability of soils for mole drainage
Authors: SPOOR G. , LEEDS‐HARRISON P. B. , GODWIN R. J.
Published: July 2006

The failure mechanisms causing mole channel deterioration or collapse, which are controlled mainly by the shear, swell/shrink and apparent viscosity properties of soils, are shown to be sensitive to the influence of soil density and clay mineralogy. These two properties have, therefore, a clear potential role in helping to assess the suitability of soils for mole drainage and in helping to define the particular failure mechanisms which are most likely to be active in given situations.
Chemical pools of cadmium, nickel and zinc in polluted soils and some preliminary indications of their availability to plants
Authors: SOON Y. K. , BATES T. E.
Published: July 2006

This study was conducted to determine the chemical distribution and plant availability of Cd, Zn and Ni in eight metal‐polluted soils in southern Ontario, Canada. There were altogether 30 different soil samples because two of the soils had received various sewage sludge treatments. The soils were sequentially extracted with 1 m ammonium acetate to remove soluble plus exchangeable metals, with 0.125 m Cu(II) acetate to remove complexed metals, and with 1 m HNO3 to dissolve chemisorbed or occluded metals and precipitates such as oxides and carbonates. Expressed as a percentage of the metal soextracted, exchangeable Cd and Zn and Ni; complexed Cd and Zn>Ni and Ni>Zn>Cd in the acid‐soluble pool. With a few exceptions (soils with high organic matter content or low pH) at least 50 per cent of the extracted metal was in the acid‐soluble pool. The percentage of metal complexed was significantly correlated with organic matter content. The percentage of metal in the acid‐soluble fraction was significantly correlated with soil pH. Preliminary findings based on the results with two soils suggested that for Cd and Zn plant availability was correlated with the concentrations of exchangeable, complexed or acid‐soluble pools of Cd and Zn.
High gradient magnetic separation of some soil clays from Nigeria, Brazil and Colombia.
Authors: HUGHES J. C.
Published: July 2006

High gradient magnetic separation was used to fractionate the clay from some tropical soils. Acid‐oxalate‐extractable iron (Feox) and aluminium (Alox) and total carbon were measured in the whole clay, the magnetic fraction and the tailings. The magnetic separation resulted in a wider range of concentrations of these elements than in the whole clays. In each of the clays Feox was greater in the magnetic fraction than in the tailings; Alox was more variable. Carbon was also concentrated in the magnetic fraction suggesting that it is associated more with Feox than Alox. The relationships between Feox, Alox and carbon depend on soil classification and soil age.
A new system for soil studies
Authors: BUTLER BRUCE E.
Published: July 2006

A new system for soil studies is presented. The proposed soil unit is the soil mantle, the pedoderm, as it occurs in the landscape. The soil mantle forms on the surficial sedimentary bodies in the landscape. These often have a diverse and intermittent history which is passed on to the soil mantles. The series of events in the development of each soil mantle is recognized as a ‘K cycle’, and buried soil mantles represent earlier K cycles subscripted K1, K2, etc. From the dating of these older mantles, based on included dateable material, there is an opportunity to test the major soil hypotheses, an opportunity which is lacking in the current soil working model.
A comparison of five instruments for measuring soil strength in cultivated and uncultivated cereal seedbeds
Authors: O'SULLIVAN M. F. , BALL B. C.
Published: July 2006

A torsional shear box, shear vane. cone penetrometer, drop‐cone penetrometer and pocket penetrometer were used to measure soil strength at several depths less than 150 mm in cultivated and uncultivated seedbeds in a loam and a sandy clay loam. From the shear box results, cohesion was higher and the angle of friction was lower in the sandy clay loam than in the loam. Angle of friction was independent of cultivation but cohesion was higher in uncultivated than in cultivated soil. Despite these differences cone resistance was similar in both soils above 70 mm depth. Vane shear strength and drop‐cone penetration, although empirical, indicated strength differences between soils and cultivations similar to those found with the torsional shear box. Vane shear strength, at 42 kPa, was about twice as high as cohesion in the sandy clay loam and, at 33 kPa, over four times as high as cohesion in the loam. These overestimates increased with increasing bulk density. The range of measurement of the pocket penetrometer was inadequate to cover the range of soil strengths encountered. The coefficient of variation within plots for cone resistance decreased from 76 per cent at 10 mm depth to about 22 per cent at 70 mm depth and below, and for vane shear strength it was 33 per cent near the soil surface. The drop‐cone penetrometer results were the most variable, reflecting the log‐normal distribution of penetrations. The cone penetrometer was the fastest method, followed by the shear vane, drop‐cone penetrometer and torsional shear box in that order.
Chemical and colloidal stability of sols in the Al2O3‐Fe2O3‐SiO2‐H2O system: their role in podzolization
Authors: FARMER V. C. , FRASER A. R.
Published: July 2006

Concentrations of dialysable silica in equilibrium with Al2O3‐SiO2‐H2O sols at pH 4.5–5.0 confirm the formation of a poorly ordered non‐dialysable proto‐imogolite species with an Al : Si ratio near 2, close to that of imogolite. Sols with Al : Si>2 give nearly constant levels of free silica in solution in the range 2–6 μg/cm3, indicating equilibrium between proto‐imogolite and aluminium hydroxide species. These findings indicate that imogolite‐like precipitates in acid soils will buffer silica in solution to within this range during leaching episodes. Imogolite is more stable than a previous estimate suggested, and a revised value for its free energy of formation is proposed: ΔG0f(298.15) = ‐2929.7 kJ/mol.

In Fe2O3‐SiO2‐H2O sols, the Fe : Si ratio of the non‐dialysable species varies smoothly from 11 to 3 as free silica in solution ranges from 4 to 35 μg/cm3. Such sols are much less colloidally stable than hydroxyaluminium silicate sols, but mixed Al2O3—Fe2O3—SiO2—H2O sols are almost as stable as iron‐free sols up to a Fe : Al ratio of 1.5. Thus migration of Al and Fe as mixed hydroxide sols can account for the almost constant ratio of Al to Fe with depth in oxalate extracts from Bs horizons of podzols.
The specific surface of soils determined by water sorption
Authors: NEWMAN A.C.D.
Published: July 2006

The hypothesis that the specific surface of soil can be measured by water sorption is tested with data for 62 subsoils of widely differing origins. Ethylene glycol and water sorption at p/p0=0.47 are found to be very closely related measurements and both are highly correlated with CEC. Both methods give a satisfactory measure of total specific surface for soils classed as smectitic and having a large CEC. However, the application of the multilayer theory to the sorption of water on external surfaces of clayey soils with small CEC suggests that both sorbates overestimate the specific surface of such soils. A better estimate of the errors would be obtained from isotherm measurements with water, which is more suitable for this purpose than ethylene glycol.
The variation of soil critical state parameters with water content and its relevance to the compaction of two agricultural soils
Authors: LEESON J.J. , CAMPBELL D.J.
Published: July 2006

Examination of the previously published results of laboratory compression tests on a loam and a sandy loam has shown that as the water content and degree of saturation of a soil increase, the gradient of the virgin compression line, expressed in terms of specific volume and log of spherical pressure, increases and its intercept decreases. The water contents of the soils ranged from 5% to 30% and the degrees of saturation ranged from 10% to 40%. For both soils the gradient of the recompression line for previously compressed soils was shown to decrease with decreasing initial specific volume (increasing density) and to approach zero at a specific volume of 1.5 (dry bulk density of 1750 kg/m3). It was deduced that the position of the critical state line also varies with soil water content and that the critical state theory can be extended to unsaturated soils and therefore be of use in predicting the mechanical behaviour of agricultural soil during cultivation and compaction.
An evaluation of some fluorescent and non‐fluorescent dyes in the identification of water transmission routes in soils
Authors: SMETTEM K. R. J. , TRUDGILL S. T.
Published: July 2006

Two fluorescent dyes, sulpho‐rhodamine B and lissamine yellow FF, and three non‐fluorescent dyes, chlorantine fast green, sirius red and Chicago blue are compared for use in the identification of water transmission routes in structured soils. Subsequent to the flow of labelled water, a microsampling and extraction technique is employed to identify dye distribution in relation to structural features. The desirable properties of the dyes tested include stability over a wide pH range, anionic character and high molecular weight, the latter to reduce lateral diffusion from the transmission route. In these aspects they provide suitable alternatives to fluorescein and pyranine used by previous workers. The fluorescent dye lissamine yellow FF was found to be the most suitable for tracing rapidly moving water under field conditions. The transmission routes identified in field soils were associated with structural features readily recognized by routine soil survey techniques.
Use of a three‐plane model to describe charge properties of some iron oxides and soil clays
Authors: MADRID L. , DÍAZ E. , CABRERA F. , DE ARAMBARRI P.
Published: July 2006

The pH‐dependence of surface charge density of three iron oxides and the clay fraction of five horizons of a variable‐charge soil has been studied by adsorption of potential‐determining ions (p.d.i.) and by adsorption of electrolyte ions. The general trend of results for iron oxides can be satisfactorily explained by a model which considers a three‐plane distribution of electric potential. When the model is applied to soil clays the outcome is less satisfactory and, although their charge properties seem to be largely determined by their high content of minerals with variable charge surfaces, the presence of minerals with a permanent charge (clay minerals) should be considered when explaining the particular data, even for those horizons where clay minerals are present in low proportions.
Effect of periodate treatment of soil on carbohydrate constituents and soil aggregation
Authors: CHESHIRE M. V. , SPARLING G. P. , MUNDIE C. M.
Published: July 2006

Soil from a field under long‐term grass was treated with 0.02m sodium periodate for various periods up to 1176 h, followed by 0.1 d sodium tetraborate for 6 h. This destroyed an increasing proportion of microaggregates >45 μm and carbohydrate. After periodate treatment for 6 h about 70% of the soil sugars remained in the residue as measured by reducing sugar content and about 67% as individual sugars measured by gas‐liquid chromatography. After 48 h the reducing sugar content was about 45%. An inverse linear relationship was established between the proportion by weight of microaggregates >45 μm and residual carbohydrate. The residual carbohydrate showed an enrichment in sugars commonly found in plant materials; glucose, arabinose and xylose, suggesting that the microbial carbohydrate had been preferentially destroyed. When the concentration of the periodate was increased to 0.05 m the residue contained about 50% of the original carbohydrate after 6 h treatment, and 25% after 48 h and an additional increase of about 10% in the proportion by weight of particles in the <45 μm range.

These results throw doubt on the validity of assumptions made in a number of studies about the limited extent to which soil polysaccharide is involved in aggregation.