bluuebunny/crossref_metadata_2025_split huggingface dataset:
BROWN PODZOLIC SOILS AND THEIR STATUS IN BRITAIN
Authors: BALL D. F. 
Published: July 2006

SummaryThe characteristics are outlined of freely drained soils, transitional in location, morphology and chemistry between modal Brown Earths and Peaty Podzols, which occur widely in western and upland Britain. They have been classified in a number of ways, which are discussed with reference to a review of American and European treatment of Brown Podzolic Soils. Although precise definition in terms of chemistry is not possible, evidence supports the continued distinction of such soils as Brown Podzolic Soils (or Sols Bruns Podzoliques) considered as a sub‐group of Podzolized Soils.
THE MECHANISM OF PHOSPHATE ADSORPTION BY KAOLINITE, GIBBSITE, AND PSEUDOBOEHMITE
Authors: MULJADI D. , POSNER A. M. , QUIRK J. P. 
Published: July 2006

SummaryThe adsorption isotherms of phosphate have been determined at pH 5 on acid‐washed K‐kaolinite and gibbsite, Na‐ and Al‐kaolinites, and K‐kaolinite in the presence of KCl at 20°C.An isotherm obtained for K‐halloysite did not support the suggestion made in Part I that any part of the adsorption was due to gross inter‐lamellar penetration in the kaolinite.It is concluded from the relative behaviour of these systems that adsorption occurs on an edge—Al(OH)2 and in some amorphous region of the clay surface.
THE EFFECT OF IRON OXIDE IMPURITIES ON THE POSITIVE AND NEGATIVE ADSORPTION OF CHLORIDE BY KAOLINITES1
Authors: SUMNER M. E. , REEVE N. G. 
Published: July 2006

SummaryIn the past, the effect of iron‐oxide impurities in kaolinites has been ignored when studying properties such as edge‐charge and Cl− adsorption. In this investigation, iron oxides were found to have a marked effect on the adsorption of Cl− by kaolinite. Cl− was positively adsorbed by some kaolinites at high pH values indicating that positive charges were present under alkaline conditions. A large part of this positive adsorption of Cl− was due to the iron oxide in the samples. The presence of small amounts of iron oxides gave rise to large errors in the measurement of edge‐charge on kaolinite. After deferrification, reasonable results were obtained.
THE RELATIONSHIP BETWEEN OXIDATION‐REDUCTION POTENTIALS AND OXYGEN‐DIFFUSION LEVELS IN SOME WATERLOGGED ORGANIC SOILS
Authors: ARMSTRONG W. 
Published: July 2006

SummaryIn valley and blanket‐bog peat, oxygen‐diffusion rates and corresponding oxidation‐reduction potentials have been measured, and the relationship between them expressed graphically.Oxygen‐diffusion rates were obtained ‘polarographically’, and the Pt cathode also served as the redox indicator‐electrode.Plateau‐shifts towards more positive potentials made it necessary to use the reduced voltage setting of −0.48 v for oxygen determinations. These plateaushifts correlate with a lowering of the oxygen content, and an increase in acidity, or, perhaps, with the type of buffer systems found in peat.The ratio redox potential/oxygen diffusion is not constant. At very low oxygen values there is a relatively large increase in redox potential per unit of oxygen, but, as oxygen approaches 2 × 10−8 g O2cm−2min−1, the ratio becomes much lower, while variations become more obvious.rH values calculated according to Jeffery (1961), show that, in peat of high iron content at pH 6, the first traces of oxygen correspond to an rH 1.10–1.20 (E6, 50–120; reduced and oxidized iron probably present), while above 2 × 10−8 g O2 cm−2min−1 the rH is greater than 1.20 and oxidized iron probably predominates. Thus oxidized soil, as defined by Jeffery, may be maintained at very low oxygen levels.It is suggested that oxygen diffusing from plant roots into these peats will oxidize reduced soil products, and thereby protect the plant.
POSITIVE ADSORPTION FROM MIXTURES OF THREE ELECTROLYTE SOLUTIONS
Authors: HELMY A. K. 
Published: July 2006

SummaryThe double layer theory was used for estimating the relative amounts of positively adsorbed cations when a mixture of three salts with mono‐, di‐, and trivalent cations is present in clay electrolyte systems. It is shown that the adsorbed cations are dominated by the trivalent cation when the salts are present at equal concentrations.
A SIMPLE AND INEXPENSIVE APPARATUS FOR AUTOMATICALLY CONTROLLING SOLUTION FLOW RATES THROUGH SOIL COLUMNS
Authors: GRAHAM‐BRYCE I. J. , DAVIES R. I. , AL‐RAWI A. A. H. 
Published: July 2006

SummaryAccurate control of rate of flow of solution through soil columns is important in laboratory studies of leaching, but is difficult to achieve because of fluctuations in permeability. A simple and inexpensive method of automatically maintaining a constant flow‐rate through several columns simultaneously is described. The apparatus comprises (i) a rotating delivery system which distributes the leaching solution equally to eight compartments, (ii) a system for automatically regulating the flow through each column to keep pace with the solution delivered, and (iii) an automatic fraction‐collector to collect the effluent from the columns. Using this apparatus the standard deviation of the volumes delivered to the eight individual columns was less than 2 per cent of the mean, provided the flow rate was faster than 10 ml/h.
STONE PAVEMENTS IN SOILS OF CAERNARVONSHIRE, NORTH WALES
Authors: BALL D. F. 
Published: July 2006

SummaryIn Caernarvonshire, North Wales, some soil profiles contain a concentration of stones as a layer, a single stone thick, which separates lower horizons of glacial drift from upper colluvial horizons. These layers, stone pavements, are believed to have formed as lag deposits (erosion pavements) on eroded drift surfaces which were then covered by colluvium. The formation and burial of the pavements may be attributed to periglacial and solifluction processes in the Late Glacial period. Local preservation of stone pavements suggests more widespread distribution of soils in which horizon differentiation results in part from depositional rather than pedological processes.
STUDIES ON SOIL POTASSIUM
Authors: BECKETT P. H. T. , NAFADY M. H. M. 
Published: July 2006

SummaryThe immediate Q/I relation of K in a soil relates the amount of labile K present to its chemical potential, measured relative to the chemical potential of (Ca+Mg) in the same soil.The present work shows that the form of the Q/I relation is almost unchanged either by large additions of K, up to 3750 kg K2O/ha, and the fixation of up to 1900 kg K2O/ha or by the depletion of the soil of both labile and some fixed K, equivalent to 5–20 years cropping.Release is shown to occur from a pool of non‐labile K, at a rate which decreases as the non‐labile pool is exhausted. The resulting increase in cation exchange capacity is greater than the amount of K released. Not all the K which is exchangeable to M NH4OAc solution is in exchange equilibrium with the soil solution.
A POLAROGRAPHIC TECHNIQUE FOR THE MEASUREMENT OF DISSOLVED SULPHIDE IN WATERLOGGED SOILS
Authors: ARMSTRONG W. 
Published: July 2006

SummaryThe polarographic oxidation of sulphide at the dropping mercury electrode reported by Revenda (1934), forms the basis of this technique for the assay of dissolved sulphide in soil solutions.Soil solution is expressed from cores removed from the soil in a Hiller‐type borer, and transferred to tubes containing pyrogallol and NaOH. A current‐voltage curve for each sample is then obtained using the dropping mercury electrode in conjunction with a saturated calomel electrode. The current in the plateau region of a curve is proportional to the sulphide concentration, and after volume and temperature corrections, the sulphide concentration in a sample can be read from a previously prepared calibration curve.The possibility of sulphide loss from the samples before analysis has been found to be slight.Details of construction, and calibration of the dropping mercury electrode using standard Na2S solutions, are included in the description of the technique and apparatus. The inclusion of such minor modifications as (a) the insertion of a condenser across the microammeter terminals to dampen the large current oscillations produced by the dropping mercury electrode, and (b) the inclusion of a switch to allow reversal of polarity at the microammeter, enabled a circuit of the type currently used for soil oxygen diffusion measurements to be used also for sulphide estimation.
THE EFFECT OF FARMYARD MANURE ON MATRIC SUCTIONS PREVAILING IN A SANDY LOAM SOIL
Authors: SALTER P. J. , BERRY G. , WILLIAMS J. B. 
Published: July 2006

SummarySoil matric suctions under a crop of ryegrass on farmyard manure‐treated and untreated plots were determined over a total period of 24 weeks from March to November. The soil moisture characteristic of each plot was determined five times throughout this period, and for each plot and on every occasion a linear relationship was found between moisture content and log matric suction. A formula was derived to account for the seasonal changes in moisture characteristic and it was then possible to obtain matric suction values from the soil moisture contents obtained from twice‐weekly sampling of each plot. Although differences between available‐water capacity of the manured and unmanured plots were small throughout the 6‐month period of sampling, the soil matric suctions of the manured plots were almost always lower than those of the unmanured plots. The lower suctions prevailing in the manured soil could be a factor contributing to the higher yields of ryegrass obtained from the manured plots as compared with those obtained from the unmanured plots.
THE MOISTURE RÉGIMES OF SOILS DEVELOPED ON KEUPER MARL
Authors: THOMASSON A. J. , ROBSON J. D. 
Published: July 2006

SummaryThe moisture régimes of several representative profiles of the Worcester series developed on Keuper Marl are described and interpreted using a simple field technique supplemented by determinations of pore space, moisture content, and moisture release characteristics. It is suggested that the textural B horizon of coarse blocky structure is the cause of waterlogging which occurs seasonally in the upper 61 cm of these soils. The C horizon, which has a fine blocky structure and a lower clay content, is more permeable, and determinations of pore space and moisture content showed an appreciable volume of air voids in it when the overlying horizons were fully saturated with water.After subsoiling to a depth of 76 cm at one site, the soil was waterlogged less often and then only for shorter periods than formerly.
THE INFLUENCE OF IONIC ENVIRONMENT ON THE NATURE OF IRON OXIDES IN SOILS
Authors: TAYLOR R. M. , GRALEY A. M. 
Published: July 2006

SummaryThe colour in a sequence of soils formed on basalt in the Burnie area of Tasmania changes from red to red‐brown near sea level to a yellow‐brown in the more elevated areas. This colour change reflects the variations in the goethite/haematite ratio which in turn has been positively correlated to the proportions of Ca plus Mg on the exchange complex. The results support the laboratory observations of Schellmann that the adsorption of Ca and Mg ions by freshly precipitated iron oxide gel directs the ageing towards haematite.
THE MEASUREMENT AND MECHANISM OF ION DIFFUSION IN SOILS
Authors: VAIDYANATHAN L. V. , DREW M. C. , NYE P. H. 
Published: July 2006

SummaryIntegral diffusion coefficients for K in two contrasting soils, containing different levels of exchangeable K, are calculated from measurements of diffusive flux to a hydrogen resin paper. The diffusion coefficients are larger, the higher the exchangeable K level or moisture content.Diffusive flux of K in these soils can be accounted for entirely by diffusion through the soil solution in the pores.Impedance factors calculated compare satisfactorily with values for similar soils reported by other workers.The concentration dependence of the diffusion coefficient is shown to be causally related to the nature of the sorption isotherm.A method for estimating the differential diffusion coefficient at any concentration is described. It can also be calculated from the slope of the sorption isotherm at the chosen concentration, if the value of the impedance factor at the relevant moisture content is known and if diffusion other than through solution only is negligible.
PEDOGENIC GRADIENTS OF THE POLAR REGIONS
Authors: TEDROW J. C. F. 
Published: July 2006

SummarySoils of the polar regions are divided into three zones—Arctic Brown, Polar Desert, and Cold Desert. The Arctic Brown soil coincides approximately with the arctic tundra belt, the Polar Desert zone is penecontiguous with the high arctic, and the Cold Desert zone is represented by the ice‐free sectors of Antarctica. The zones are broad and diffuse. Well‐drained soils of the southern sectors of the Arctic Brown soil zone have embryonic podzolic affinities whereas soils of the northern portions of this same zone exhibit a low temperature calcification process akin to a cold steppe condition. Vascular plants form a continuous mat in the Arctic Brown soil zone but within the Polar Desert soil zone they are patchy or at times completely lacking. In the Polar Desert soils algae and diatoms appear to be the main contributors of soil organic matter. The Cold Desert soils of Antarctica are virtually void of organic matter. The above three soil zones, in effect, are sectors of a pedogenic gradient. Progressing from the northern fringes of the forested land, to colder climates, precipitation decreases, organic matter content of the soil decreases, and soil pH values tend to increase. In the Polar Desert soils, alkaline reactions are common whereas the Cold Desert soils of Antarctica are usually saline. Polar Desert soils and Cold Desert soils have many morphologic affinities. Tundra and Bog soils dominate areally in the main tundra belt but are confined to the local swales and depressions in the high arctic. Both Tundra and Bog soils tend to have higher pH values as one progresses to colder, drier climates. Neither Tundra nor Bog soils have, as yet, been recorded in Antarctica.
A STUDY ON SOIL SERIES: THEIR CORRELATION WITH THE INTENSITY AND CAPACITY PROPERTIES OF SOIL POTASSIUM
Authors: BECKETT P. H. T. , NAFADY M. H. M. 
Published: July 2006

SummaryThe Intensity (I) or availability of soil K exhibits considerable variations within a Soil Series, presumably as a result of local differences in management and fertilization. The contrast is most marked between woodland and cultivated examples of the same Series. Earlier work had shown similar variations in the Quantities (Q) of labile K. Those Capacity properties (dQ/dI) of soils for labile K which derive from the planar surfaces of the clay crystals in the mineral skeleton of the soil show rather less variability. The Capacity properties of different samples of soil from one Series are not equal, but become increasingly so as the non‐clay fractions, the amphoteric oxides, and the organic matter held in the < 2μ fraction, are successively removed.It is inferred that the active surfaces available for K–(Ca + Mg) exchange in the soils studied are fundamentally similar for the soils in any one Series, but that they may be reversibly blocked by organic and amphoteric cations, to varying extents according to their previous management. The differences are greater than the differences commonly observed between different experimental plots in the same field. Duplicate samples of three Series out of the four examined showed close or moderate agreement in their K‐fixation properties.While soil organic matter has some influence on dQ/dI, the fraction with most effect is not that which makes the most substantial contribution to the CEC of the soil.
USE OF RADIOACTIVE59Fe FOR TRACING SOIL PARTICLE MOVEMENT
Authors: COUTTS J. R. H. , KANDIL M. F. , TINSLEY J. 
Published: July 2006

SummaryThe field studies reported in Part 1 were complemented by laboratory investigations on the labelling of soils and the movement of soil particles by simulated rainfall splash.Of various labelling techniques tested the most uniform absorption of59Fe, as shown by autoradiographs, was secured by adding DTPA chelating reagent to the FeCl3solution used for wetting soil peds under vacuum. Studies on the specific radioactivity of the Atterberg textural fractions, separated from clayloam, sandy loam, loam and peat soils before and after labelling, showed in all cases that the clay fraction was dominant in retention of59Fe.The radioactivity was so firmly absorbed that its movement could be used to trace both the horizontal and vertical displacements of labelled soil particles by scintillation counting or autoradiographic techniques. Tests with a rainfall simulator showed a close correlation between the weights and radioactivities of splashed soil particles.Gravimetric data obtained from unlabelled clay loam and sandy loam soils subjected to ‘rainfall’ of differing intensity, drop size and height of fall gave a linear relationship on a logarithmic scale between mass of particles and distance of splash. Calculation of the kinetic energy lost by water drops on impact with the soil and that imparted to the splashed soil particles show that the relationship depends principally on the rainfall intensity and the texture of the soil.
RATE‐CONTROLLING PROCESSES IN THE RELEASE OF SOIL PHOSPHATE
Authors: VAIDYANATHAN L. V. , TALIBUDEEN O. 
Published: July 2006

SummaryThe isotopic exchange of phosphate ions in a deep river gravel soil, maintained at different pHs from 3.5 to 6.7 in a field experiment, established by the N.A.A.S. at Shardlow, was governed initially (<20 h) by simultaneous ‘first‐order’ and ‘bulk diffusion’ kinetics, but later by ‘bulk‐diffusion’ kinetics only. The ‘bulk‐’ or ‘intracrumb‐’ diffusion coefficient was independent of phosphate manuring, was least at pH 5.5 and increased on either side of this critical pH. The rate constant for the phosphate component exchanging initially with ‘first‐order’ kinetics increased significantly with phosphate manuring at pH 3.5, 4.4, and 5.5, although the constants for unmanured and manured soils did not change with soil pH. But at pH 6.7, the rate constants for the unmanured and phosphate‐treated soils were greater than those in the more acid soils, although the constant for the manured soil was just significantly greater than that of the unmanured soil.Residual phosphate (i.e. the difference between manured and unmanured soils) adsorbed on the soil was greatest in the more acid soils but water‐soluble residual phosphate increased with soil pH to a maximum at pH 5.5. Residual phosphate, exchanging initially, decreased to nothing above pH 6.5.
FUNDAMENTAL OBJECTIONS TO THE 7TH APPROXIMATION
Authors: WEBSTER R. 
Published: July 2006

SummaryThe 7th Approximation suffers from three fundamental ills. It demands an unattainable degree of precision and its exactly defined, mutually exclusive classes lead to inconsistency or absurdity when the system is used. Logical division is used out of context to construct a hierarchical structure, while the dispersed nature of soil distribution does not lend itself to hierarchical arrangement in any form. Its search for genetically significant properties on which to define classes involves circular reasoning, since the genetic significance of a property can usually be discovered only after the soils have been classified.Mutual exclusion and rigid adherence to the hierarchy result in the system failing to serve adequately the requirements of soil survey. The 7th Approximation explores to the limit the potential of logical division for soil classification yet remains unsatisfactory. The nature of soil distribution and the requirements demanded of soil classification suggest that a co‐ordinate system would be more profitable, and a study of such systems is urged.
THE EFFECT OF HYSTERESIS OF PORE‐WATER ON THE HYDRAULIC CONDUCTIVITY
Authors: POULOVASSILIS A. 
Published: July 2006

SummaryIt is pointed out with the help of the Independent Domain Theory, that a fraction of the pore‐water constituting a volume ΔV is contained in pores not common to both the wetting and drying states and that this volume in a wetting state is contained in pores whose draining radii are greater than those of the pores containing the water volume ΔV in the drying state.On the above basis it is suggested that hysteresis may affect the hydraulic conductivity: firstly, through differences of the radii of the pores containing the water volume ΔV, which tend to endow a wetting state with a conductivity greater than that of an equally wet but drying state; secondly, through differences of the coordinates of the above‐mentioned pores, which may influence the paths of flow and consequently the hydraulic conductivity, and will have either a similar or opposite effect. It is concluded, therefore, that the conductivity in the wetting state can be greater, equal, or even less than that in the drying state, depending on the particular porous body.
RETENTION OF LOW LEVELS OF COPPER BY HUMIC ACID
Authors: DAVIES R. I. , CHESHIRE M. V. , GRAHAM‐BRYCE I. J. 
Published: July 2006

SummaryMost of the Cu previously added to humic acid derived from a sedge fen peat was easily removed by washing with acid, but the strength of binding increased as the Cu content decreased. The capacity to retain firmly bound Cu was reduced to about half by treating the humic acid to block either carboxyl or hydroxyl groups alone or to block both groups together. The retaining sites blocked therefore probably involve both carboxyl and hydroxyl groups acting together, but alternatively could be groups such as hydroxy‐quinone, affected by both types of treatment. Retention of Cu by peat differs from retention by the extracted humic acid.
LIMITATIONS IN ISOTOPIC MEASUREMENTS OF LABILE PHOSPHATE IN SOILS
Authors: AMER F. , MAHDI S. , ALRADI A. 
Published: July 2006

SummaryMethods used for measuring labile P and assessing the phosphate‐fertility status of soils by isotopic dilution as well as assumptions involved in applying the isotope dilution technique were critically evaluated.In the presence of high phosphate‐fixing compounds, e.g. reactive iron oxide, labile P may be erroneously overestimated; especially when carrier‐free 32P is used. At the end of the isotopic‐exchange reaction period, high phosphate‐fixing soils may have a higher specific activity in the solid phase than in the solution phase. Methods involving the use of a 0·2 ppm P carrier solution or the addition of an unlabelled carrier to a labelled soil may give satisfactory labile P measurements in low and in medium phosphate‐fixing soil. All the methods tried (carrier‐free, carrier, and inverse dilution), however, failed to give satisfactory results for the high phosphate‐fixing soils.
SULPHATE REDUCTION IN WATERLOGGED SOILS
Authors: BLOOMFIELD C. 
Published: July 2006

SummaryTo study the factors that influence the release of free H2S, flooded soils were incubated with plant material and either sodium sulphate or elemental sulphur. Residual sulphate, FeS and H2S were measured throughout the reaction.Less free H2S was evolved from a periodically waterlogged soil than from a well‐drained soil of comparable HC1‐ and dithionite‐soluble Fe content. With a readily soluble synthetic Fe2O3 as the source of Fe, a slight excess of Fe over the SO42– equivalent sufficed to prevent loss of H2S.The native organic matter in the well‐drained Rothamsted top‐soil seemed to have no effect in promoting loss of H2S, but the FeS:H2S ratio was strongly influenced by the nature of the plant material used as the source of energy. With either Na2SO4 or S, considerably more free H2S was evolved with lucerne than with rice blade. With S, the pH of the incubated mixtures was close to that of the nominally S‐free system, whereas with Na2SO4 the mixture became quite alkaline. More free H2S was evolved under the more alkaline conditions obtained with Na2SO4, which suggests that it is the initial mobilization of Fe that governs the distribution of the reduced S, rather than the pH‐solubility relations of FeS.An oxidized surface layer is very effective in retaining sulphur in the soil.