bluuebunny/crossref_metadata_2025_split huggingface dataset:
DARCY'S LAW AT SMALL POTENTIAL GRADIENTS
Authors: CHILDS E. C. , TZIMAS E. 
Published: July 2006

SummaryBondarenko and Nerpin have reported Bingham type plastic flow of water in a quartz capillary tube at small potential gradients, with a shear strength of about 5 × 10−2 dyne cm−2. If confirmed, this would greatly affect the theory of groundwater drainage. The experiments described here, using a granular porous material of glass spheres with pore sizes of the same order as the reported capillary radius, indicated conformity to Darcy's law (i.e. to Newtonian flow) down to one‐tenth of the threshold gradient reported by the Russian workers. Semi‐quantitative evidence confirms Darcy's law through zero potential gradient.
THERMODYNAMICS OF SINGLY CHARGED ION EXCHANGES IN THE TRACE REGIONS ON CAMP BERTEAU MONTMORILLONITE
Authors: ROBEYNS J. , VAN BLADEL R. , LAUDELOUT H. 
Published: July 2006

SummaryIon exchange equilibria for seven pairs of singly charged ions between aqueous chloride solutions and a montmorillonite clay have been studied at 25 °C for low values of the total normality of the equilibrium solution. Only the trace region for the preferred ion was investigated.Since the analogue of Henry's law was found to be valid, the exchanges being almost ideal, standard free energies were calculated from experimental data in the region where the analogue of Henry's law is obeyed by extrapolating to half‐loading with one of the ions. The results satisfy the requirement of additivity and are in good agreement with known values.
THE RELATION BETWEEN COST AND UTILITY IN SOIL SURVEY (I–III)1
Authors: BURROUGH P. A. , BECKETT P. H. T. , Jarvis M. G. 
Published: July 2006

SummaryA series of five papers compares the cost‐effectiveness of different procedures for soil survey at medium scale. The first three are presented here.The whole trial area of 120 km2 in Berkshire, in south‐central England, was mapped in soil series by free survey at 1:25 000 for publication at 1:63 360. Three contrasting sample areas of 1.26 km2 were resurveyed to the same legend by free survey at 1:10 560, and by grid survey at a range of scales between 1:20 000 and 1:70 000, to both general purpose (soil series) and fifteen–twenty different single‐property legends. The direct costs of producing each map were recorded.The study confirmed how much the free survey procedure depended on the external features of soil boundaries to locate them. The density of soil observations required to map soil series by free survey at the same map scale in different terrains was approximately proportional to the length of mapped boundary/km2, or to the number of separately mapped soil occurrences/km2. The density was least where the soil boundaries had the clearest external expression. Survey effort/km2 increased in proportion to the density of observations but was also affected by local differences in the ease of cross‐country access, or in the effort necessary (by spade or auger) to identify the soil at a point.For soil series grid surveys there are approximately linear relations between log(cost) and log(map scale) with gradients between 1.3 and 1.7.A map of soil series by grid survey is more expensive than a map of the same units, based upon the same density of observations by the same surveyor, by free survey. But a series map by grid survey by a scientific assistant is cheaper than a series map based on the same density of soil observations by free survey by a scientific officer (diplomate or graduate). The cost of an isoline map of a single soil property depends very much upon the cost of determining the property mapped, and to some extent upon the number of different isoline maps produced from a single set of samples or observations. Even at the unusually low costs of chemical analyses assumed here, an isoline map of one chemical property costs nearly twice as much as a series map by grid survey.
WATER MOVEMENT IN DRY SOILS
Authors: ROSE D. A. 
Published: July 2006

Summaryhysteresis that occurs in the micro‐hydrological characteristics of a soil (conductivity and diffusivity) as functions of water content and water potential between sorption and desorption is examined for three soils (sand, loam, and clay) and sepiolite. These materials, all aggregated, are sufficiently dry that both the vapour and liquid components of water movement are important.any water content or water potential the vapour conductivity is always bigger when wetting than when drying though differences may be small.There is hysteresis in water (vapour+liquid) conductivity as a function of water content when vapour flow but not liquid flow is dominant. Conversely, there is hysteresis in water conductivity as a function of water potential when liquid flow but not vapour flow is dominant. Both forms of this hysteresis are small.Hysteresis in diffusivity as a function of both water content and water potential exists, but is complicated.Variations caused by hysteresis, though real, are likely to be negligible in practice, swamped by effects caused by changes in the soil environment (e.g. temperature) or by changes in soil management (e.g. structure).
SPECIFIC ADSORPTION OF SILICATE AND PHOSPHATE BY SOILS
Authors: OBIHARA C. H. , RUSSELL E. W. 
Published: July 2006

SummaryThe adsorption of silicate and phosphate from pure and mixed solutions by four soils known to fix phosphate strongly has been measured.The adsorption at constant pH for each acid from its pure solution follows the Langmuir isotherm. The maximum adsorption of silicate by three of the soils from the pure solution occurs at pH 9.2, and the maximum adsorption curve for phosphate by two of the soils from its pure solution has a break in its slope at pH 6.4 and 11.6. These pHs are all just below the pK values for the dissociation of hydrogen ions from the undissociated silicic acid or the acid phosphate anions. The presence of silicate in a mixed solution, which is sufficiently concentrated in both silicate and phosphate to give maximum adsorption of either if in pure solution, does not affect the amount of phosphate adsorbed until the pH is over 6.5–7.0. At this pH the maximum adsorption curve for silicate crosses that for phosphate. The presence of phosphate in the mixed solution always depresses the adsorption of silicate. The maximum amount of silicate‐plus‐phosphate adsorbed from this mixed solution is either a little less than or equal to the amount of silicate adsorbed from the pure silicate solution if the pH is above 7. When silicate displaces phosphate, or phosphate displaces silicate, more moles of the displacing acid are adsorbed than moles of the displaced acid released.These results for soils are similar to those of Hingston et al. for the adsorption of silicate and phosphate by goethite.
AEOLIAN ADDITIONS TO SOILS AND SEDIMENTS IN THE SOUTH PACIFIC AREA
Authors: MOKMA D. L. , SYERS J. K. , JACKSON M. L. , CLAYTON R. N. , REX R. W. 
Published: July 2006

SummaryThe particle‐size distribution of the whole sample and the content, particle‐size distribution, and oxygen‐isotope abundance (δ18O) in quartz were employed to determine the extent to which aeolian materials such as aerosolic dust (10 to I /μm) from Australia, loess (50 to 10μm) in New Zealand, and flöttsand (250 to 20 μm) in Australia have been accreted into soils and sediments in the South Pacific area. Although aeolian material from both local and more distant sources has been deposited on the Franz Josef, Fox, and Tasman glaciers, the extent to which aeolian materials have been added to soils in South Westland, New Zealand, could not be determined because the oxygen‐isotope abundance (12.9 to 13.5 0/00 in quartz from the soils was similar to that (13.1 to 13.9 0/00) in quartz from the dust samples.The quartz from loess added to two basaltic soils in North Auckland, New Zealand, had an oxygen‐isotope abundance (12.9 to 13.9 0/00) slightly lower than that (15.0 to 15.4 0/00) in quartz from a greywacke‐derived soil and the underlying rock also in North Auckland. The oxygen‐isotope abundance (13.6 to 15.4 0/00) in quartz from a chronosequence of soils developed in basalt in Victoria, Australia, indicates that the quartz did not originate from the parent basalt, but probably was transported by aeolian processes from stranded beach ridges and dunes and added to the soils in the form of flöttsand, an aeolian material coarser than loess and finer than dune sand.Most particles of the pelagic sediments fell within the aerosolic dust size range. The oxygen‐isotope abundance (12.1 to 15.1 0/00) in quartz isolated from several pelagic sediments between latitudes 35 and 45° S. was similar to that (12.9 to 15.4 0/00) in quartz from New Zealand and Australian soils located between these latitudes. An aeolian source of quartz explains the above relationship and also the decreasing delta values of quartz from sediments and soils with increasing latitude in the South Pacific area. Oxygen‐isotope abundance in quartz refutes a volcanic origin of quartz in pelagic sediments but supports the deduction of Griffin et al. (1968) from mineralogical analyses that the quartz and associated minerals were transported from lands to seas.
POTASSIUM‐ALUMINIUM EXCHANGE IN ACID SOILS I. KINETICS
Authors: SIVASUBRAMANIAM S. , TALIBUDEEN O. 
Published: July 2006

SummaryA kinetic method is described and investigated for determining exchangeable Al in acid soils using M NH4Cl solutions the pH and leaching rate of which was critical for obtaining accurate and reproducible values. Molar concentrations of ammonium acetate displaced at least part of the Al chelated to functional groups in the soil organic matter.The adsorption kinetics of K and Al from 10−3 M chloride solutions on the NH4‐saturated forms at the original soil pH of these, under leaching conditions similar to the ‘extraction’ method, showed that, when the atom ratio K/A1 > 1 in the equilibrating solution, initially more K was adsorbed than at equilibrium, although Al did not ‘over‐equilibrate’ when K/A1 < 1. At least 24 h were required for attaining equilibrium in K :A1 equilibria work with soils and clays.The kinetics of desorption (extraction method) and adsorption of K and Al obeyed the first‐order and parabolic rate respectively. This is attributed to the large difference in anion concentrations in the two methods.
COMPUTER‐BASED SOIL MAPPING OF SMALL AREAS FROM SAMPLE DATA
Authors: WEBSTER R. , BURROUGH P. A. 
Published: July 2006

SummaryA 1400 m × 600 m rectangular area of north Berkshire had been sampled at the intersections of a 100 m square grid, and seventeen properties of the soil profile measured. The eighty‐four sampling sites were classified numerically to produce a hierarchy, and the classes of the upper part of the hierarchy mapped. The mapped classes became increasingly fragmented as the number of classes increased. At the 3‐class level, the classes corresponded to character space clusters and class fragmentation was not serious. Principal‐component analysis of the sample data yielded a first component that accounted for 40 per cent of the total variance and well represented the field characters used for soil classification. An isarithm map of the first component shows how the soil changes gradually over the landscape in good agreement with a soil‐series map made by free survey.
COMPUTER‐BASED SOIL MAPPING OF SMALL AREAS FROM SAMPLE DATA
Authors: WEBSTER R. , BURROUGH P. A. 
Published: July 2006

SummaryTwo rectangular areas 1400 m × 600 m in south central England had been sampled at the intersections of 100 m square grids, and some 20 soil properties measured. Hierarchical numerical classifications gave classes which, when mapped, were very fragmented. Fragmentation was less when the geographic locations of the sampling sites were included in the classification. Linear functions of location and contiguity constraints produce maps that are smoother, i.e. less fragmented, but are unsatisfactory in other aspects. Inverse square and exponential functions of location produce smoother maps that are quite as good as those produced without taking location into account, in that the soil is no more variable within the classes mapped.
METAL‐COMPLEX FORMATION BY LICHEN COMPOUNDS
Authors: ISKANDAR I. K. , SYERS J. K. 
Published: July 2006

SummaryThe formation of soluble complexes, frequently coloured, when solid lichen compounds were shaken with water suspensions of biotite, granite, and basalt indicated that chemical weathering had occurred. The formation of colourless complexes and the adsorption of the dissolved lichen compound or complex by the silicate phase complicate the interpretation of the spectrophotometric analysis data. Lichen compounds invariably released greater amounts of Ca than of Mg, Fe, and Al from the silicates and, for each lichen compound, the release of Ca was usually greater from biotite than from granite or basalt. Release of cations from the silicate materials resulted largely from metal‐complex formation rather than from reactions directly involving hydrogen ions. Citric, salicylic, and phydroxy‐benzoic acids and EDTA, used as control organic acids, usually released considerably greater amounts of cations from the silicates than did the lichen compounds, consistent with the higher water solubility of the control organic acids. Similar amounts of Fe, Al, Ca, and Mg were released from the silicates by solutions of the lichen compounds and by solid lichen compounds. Lichen compounds are sufficiently soluble in water to form soluble metal complexes and to effect chemical weathering of minerals and rocks.
CALIBRATION OF GEL PERMEATION CHROMATOGRAPHY MATERIALS FOR USE WITH HUMIC ACID
Authors: CAMERON R. S. , SWIFT R. S. , THORNTON B. K. , POSNER A. M. 
Published: July 2006

SummaryThree common gel‐chromatography materials have been calibrated for humic acid, using fractionated samples the molecular weights of which were calculated by combining sedimentation coefficients determined on the ultracentrifuge with diffusion coefficients.The gel materials were found to have the following fractionation ranges for humic acid when tris buffer was used: Sephadex G‐100, 2500 to 100000; Bio Gel P‐150, below 1000 to 40000; Sepharose 6B, 1500 to 2500000. Borax buffer appeared to extend the range of Sephadex G‐100 to lower molecular weights.A brief comparison is made of the retention behaviours of humic acid, proteins, and dextrans on the gel materials.
MOLECULAR WEIGHT AND SHAPE OF HUMIC ACID FROM SEDIMENTATION AND DIFFUSION MEASUREMENTS ON FRACTIONATED EXTRACTS
Authors: CAMERON R. S. , THORNTON B. K. , SWIFT R. S. , POSNER A. M. 
Published: July 2006

SummaryWhole humic acid extracts are usually too polydisperse for reliable molecular‐weight measurement to be made in the ultracentrifuge by the sedimentation velocity technique. Consequently, the humic acid used in this study was fractionated with respect to molecular weight into fractions of low polydispersity by extensive use of gel‐permeation chromatography and other fractionation techniques.The sedimentation and diffusion coefficients of the fractions were determined and molecular‐weight values calculated. These values ranged approximately from 2 × 103 to 1.5 × 106, the higher figure not necessarily representing the upper limit for these substances.On the basis of the frictional parameters calculated from the experimental data, it is proposed that the molecule adopts the solution conformation of a randomly coiled polymer in which branching may be significant, particularly at higher molecular weights.
MIGRATION AND AGGREGATION OF Na AND Ca CLAYS BY THE FREEZING OF DISPERSED AND FLOCCULATED SUSPENSIONS
Authors: ROWELL D. L. , DILLON P. J. 
Published: July 2006

SummaryThe ability of clay to move ahead of an ice‐liquid interface depends on the rate of freezing, the particle size, the release of dissolved air from the water through its probable effect on local freezing rates, and on the electrolyte and its concentration through their effects on interparticle forces and particle mobility. A freezing‐rate of 1 cm per hour did not move flocculated clay in most cases, but moved dispersed clay up to 0.7 cm before being trapped in the ice with released air. Aggregates of clay (0.1 to 1 mm) were produced by freezing. After thawing they swelled and dispersed depending on the electrolyte and its concentration in a similar manner to aggregates formed by drying.
TWO METHODS FOR QUANTITATIVE DESCRIPTION OF SOIL PARTICLE SHAPE
Authors: DAVIS P. F. , DEXTER A. R. 
Published: July 2006

SummaryIt was required to be able to measure the shapes of soil particles in order that the influence of shape on soil mechanical properties could be investigated. Two methods were developed, both of which can be applied to particle cross‐sections or outlines. The first is a shape function which compares chord lengths with arc lengths around the particle outlines. The second method involves taking discrete Fourier transforms of the normalized curvatures of the outlines, and the production of curvature spectra. Both methods are illustrated with the use of the same data. The data were for three sizes of particle from a sandy soil. Both methods illustrate the greater asphericity or angularity of the smaller particles, which is consistent with the Griffith theory of comminution. Change in shape with particle size may be useful for classifying soils according to their methods of formation.
THE ORGANIC MATTER CONTENT OF THE SAVANNA SOILS OF WEST AFRICA
Authors: JONES M. J. 
Published: July 2006

SummaryPublished and unpublished data on the amounts of organic matter and nitrogen in the surface soils of the West African savanna are reviewed. In general, amounts are small; the mean carbon content of soils from 605 well‐drained sites was 0.68 per cent.Two important factors governing amounts of organic matter in well‐drained soils appear to be the clay content and a moisture factor related to the length of the wet season and represented here by mean annual rainfall. Multiple linear regression on soil clay content and rainfall accounted for 46.5 per cent and 57.2 per cent, respectively, of the observed variability of soil carbon and nitrogen contents. These findings suggest that the low levels of organic matter in savanna soils arise from their predominantly sandy nature and from the relatively low rainfall. In poorly drained soils organic matter levels are higher but are less significantly related to clay content and rainfall. The influence of human interference and of parent material and altitude on organic matter is demonstrated in the context of geographically limited areas within the savanna for which more detailed information was available.
K‐ACTIVITY RATIOS AND THE UPTAKE OF POTASSIUM BY RYEGRASS IN THE FIELD
Authors: BECKETT P. H. T. , CLEMENT C. R. 
Published: July 2006

SummaryA model (based on the short‐ and long‐term Q/I relations of K in a soil, on graphs of K‐uptake by crop against post‐uptake K‐activity ratios, and the exhaustion value of K‐activity ratios below which K can no longer be taken up) is presented by means of which to estimate the amount of labile K in a soil, and to compare the contributions of labile and fixed K to plant uptake. The application of the model was partially explored in a field experiment. Relative values for the magnitudes of the pools of labile and fixed K developed by 4 years’build‐up treatments were calculated on the basis of the model. Their relative contributions to the K taken up by a ryegrass test crop in the following year were calculated from the soil Q/I relations, and the measured uptakes of K. While the data were incomplete and so could not provide conclusive evidence for the model, the values produced were sensible and apparently consistent.
A FLOTATION METHOD FOR THE RAPID MEASUREMENT OF THE WET BULK DENSITY OF SOIL CLODS
Authors: CAMPBELL D. J. 
Published: July 2006

SummaryA flotation method for the rapid measurement of the wet bulk density of soil clods is described in which the clods are sprayed with a waterproof coating of a resin and then immersed sequentially in liquids of different specific gravity. It is compared with the wax coating method for a selection of soil textures and moisture contents and shown to be ten times as rapid when used to measure wet bulk density with an accuracy of ± 0.05 g cm‐8. The flotation method was used to show that, for three contrasting soils, clod wet bulk density is independent of clod size.
SOIL STRUCTURE AND CROP YIELD
Authors: LOW A. J. 
Published: July 2006

SummaryRelatively little has been published in Great Britain relating yields with quantitative assessments of the structure of soils. This paper gives examples of the kind of correlations found, a selection from many years' observations. Where the quantity of soil nutrients or disease was not a limiting factor, the yields of cereals, peas, and red beet were related to the stability of the structure which in turn depended on the number of years the soil had been out of grass.On a soil of weak structure it was found that stabilizing, with a conditioner, the structure developed by cultivation at a moisture content below field capacity resulted in a marked increase in both yield and size grade of cauliflowers.
THERMODYNAMICS OF COBALT(I1)‐SODIUM EXCHANGE ON MONTMORILLONITE CLAY
Authors: SINGHAL J. P. , SINGH RISHI PAL 
Published: July 2006

SummaryAn attempt has been made to predict the mechanism of Co(I1)‐Na exchange on montmorillonite with the help of thermodynamic parameters derived from the experimental results. The exchange isotherms indicated a preference of Co ions for the clay phase, a fact in accordance with the separation factor. The reaction was accompanied by a decrease in the free energy, enthalpy, and entropy of the system revealing a tighter and more orderly structure of Co ions on the montmorillonite surface.
SOME ASPECTS OF THE HYDRODYNAMIC DISPERSION OF SOLUTES IN POROUS MATERIALS
Authors: ROSE D. A. 
Published: July 2006

SummaryThe paper reviews some quantitative aspects of the hydrodynamic dispersion of solute that occurs under the combined influence of molecular diffusion and convection when a solution flows through a porous material. In particular, the paper (i) describes several methods of analysing the breakthrough curve of one solution as it displaces another from‐ a column of porous material to yield a coefficient of hydrodynamic dispersion (K); (ii) discusses the form of K as a function of particle size and fluid velocity in granular beds composed of solid particles or of aggregates; (iii) discusses the effect of K on the dispersion observed in a column of porous material, as fluid velocity and particle size vary, as an aid in assessing the efficiency of leaching.
MICROBIAL POPULATIONS AND NITROGEN IN SOIL GROWING CONSECUTIVE CEREAL CROPS INFECTED WITH TAKE‐ALL
Authors: BROWN MARGARET E. , HORNBY D. , PEARSON VIVIENNE 
Published: July 2006

SummaryAnnually, for the past 12 years, a consecutive cereal‐cropping sequence was begun. During 1969–72 soil was collected from plots with similar fertilizer treatments, but with different sequences of crops. In 1971 and 1972 wheat seedling bioassays showed that take‐all disease became miximal after two or three crops, decreased to the fifth or sixth crop and then remained fairly constant in the‘take‐all decline’state.The sequence with maximum disease had most NH4+ ‐N and least NO3‐ ‐N in the rhizosphere soil in spring 1972, but there were no similar relationships in bulk soil in either of 2 years. Soil and rhizoplane populations of ammonifying and denitrifying bacteria were notably smaller in autumn 1970 and 1971 in short cereal sequences (2‐5 yr.) than in the longer sequences. After γ‐irradiating or autoclaving irradiated soils, all sequences contained much NH4+ ‐N and although disease developing from added inoculum differed among soils, it did not follow the take‐all decline pattern. Diffusate from sterilized soil favoured growth of the pathogen (Gaeumannomyces graminis var. tritici) least when it originated from the sequence that supported maximum disease.