bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE MECHANISM OF SURFACE NITRATE ACCUMULATION ON A BARE FALLOW SOIL IN UGANDA
Authors: SIMPSON J. R. 
Published: July 2006

SummaryIn a red latosol loam under bare fallow at Kawanda, Uganda, nitrate accumulates to as much as 70 p.p.m, nitrate nitrogen during short periods of dry weather. Nitrate accumulation appears to be a microbiological process involving nitrifying bacteria similar to Nitrosomonas and Nitrobacter. Nitrate accumulation in an isolated topsoil, 3 in. deep, ceased when the moisture content fell below 10 per cent. Accumulation continued on plots which were in contact with the subsoil and which remained at 10 per cent. moisture.It was concluded that under the conditions of these experiments, transport of ions to the surface by capillary transport or diffusion does occur, but is not responsible for the major nitrate accumulation, which seems to depend on progressive drying of the topsoil during which nitrate, as formed, becomes protected by the dry conditions from microbial reduction, assimilation, and leaching. Any process which prevents the progressive drying, e.g. shading, mulching, and watering, can be expected to favour nitrate removal and so to prevent nitrate accumulation.
POST‐GLACIAL SEDIMENTS AS A RECORD OF REGIONAL SOIL DRIFTS
Authors: PEARSALL W. H. , GAY JOYCE , NEWBOULD JOSEPHINE 
Published: July 2006

SummaryAnalytical data are given for deep‐water sediments from Esthwaite Water in the English Lake District representing different depths below the mud surface and sediments of ages back to and including the late‐glacial, of which the pollen status is known. Nitrogen content and loss on ignition increase steadily in muds laid down during the time of post‐glacial forest development, showing also a small previous rise which represents the temporary late‐glacial climatic amelioration (Allerad). Nitrogen remains approximately constant in muds representing the stage of post‐glacial alder‐oak‐birch forest. Deforestation, as shown by increases in grass pollen in the muds, is associated with falls in the values for nitrogen and loss‐on‐ignition. These decreases occur in two stages, believed to represent two stages of human settlement and land use.Analyses for elements such as sodium, potassium, magnesium, calcium, and iron, show signs of increasing solubility in the muds representing the time of forest development. Thereafter the amount of calcium diminishes progressively in later muds, while the Ca/Fe ratio falls, changes which could be correlated with the leaching effects of a rainfall of 170‐zoo cm. per annum on the soils in the lake basin. Similar data are recorded for a core from Rydal Water.The results are interpreted as records of the regional changes in soils from the lake drainage systems during the post‐glacial period.
AN INTRODUCTION T O THE SOILS OF THE SOUTH‐EASTERN PORTION OF THE AUSTRALIAN ARID ZONE
Authors: JESSUP R. W. 
Published: July 2006

SummarySeven soil regions, each of which is dominated by soils belonging to one or two great soil groups, are defined and mapped. The outstanding feature is the presence of a variety of soils with widely differing characteristics. The soils are deeper, have more profile differentiation and are finer‐extured than those in most‐arid regions and are frequently overlain by currently‐forming deposits of wind‐transported materials. Because the vegetative cover is better developed and there are only small areas of rocky hills and bare rock pediments, water erosion and deposition are not as prominent as in other arid areas.
EVOLUTION OF THE TWO YOUNGEST (QUATERNARY) SOIL LAYERS IN THE SOUTH‐EASTERN PORTION OF THE AUSTRALIAN ARID ZONE
Authors: JESSUP R. W. 
Published: July 2006

SummaryThe calcareous materials in the deposits, on which the Bookaloo soils developed, were transported by wind. They were derived through deflation of older soils that occurred both within the region and in an area lying to the west. Wind erosion in the region was confined to a zone in which the climate became arid. Beyond the arid zone there was a sufficient cover of vegetation for landscape stability. In some localities deposits of wind‐blown materials accumulated in the beds of relic streams. The present drainage lines are incised in these deposits.The soils, whose profiles are characterized by only weak horizon differentiation, developed following the onset of wetter climatic conditions.
MISCIBLE DISPLACEMENT IN POROUS MATERIALS
Authors: BIGGAR J. W. , NIELSEN D. R. 
Published: July 2006

SummaryMiscible displacement has been studied in several porous materials under saturated and unsaturated conditions at different average flow velocities. The tracer appeared at the end of the soil column sooner than would be expected, had no mixing occurred at the boundary of the tracer and tracer‐free water. Physical differences between porous materials were manifested by changes in shape and position of break‐through curves owing to ionic diffusion. One of the more important physical features was the magnitude of the volume of water not readily displaced at saturation and its increase when the soil was desaturated. Because the total flux of water moving through field soils is generally small, the role played by hydrodynamic dispersion and diffusion in transporting dissolved solutes must be included in the theory of most soil‐water processes.
EXCHANGEABLE BASES OF MATURE, WELL‐DRAINED SOILS IN RELATION TO RAINFALL IN EAST AFRICA
Authors: SCOTT R. M. 
Published: July 2006

SummaryAt low levels of annual rainfall, leaching of bases with falling percentage saturation follows a simple physical pattern, but as rainfall rises above a level sufficient for reasonable plant growth, intrusion of the biological factor leads to a recirculation of bases and even to an accumulation in the solum with the result that percentage saturation rises once more to an optimum at about 46 in. rainfall and falls away with further increase in rainfall.These changes in percentage saturation are independent of the base‐exchange capacity of the parent material, and the total exchangeable bases in a soil are determined by the base‐exchange capacity of the parent material and the rainfall régime to which it has been subjected.
THE SWELLING OF CA‐MONTMORILLONITE DUE TO WATER ABSORPTION
Authors: EMERSON W. W. 
Published: July 2006

SummaryThe increase in thickness of dry orientated flakes of Ca‐montmorillonite about 0·2 mm. thick, prepared from Wyoming bentonite, when brought into vapour equilibrium with solutions of increasing relative vapour pressure has been measured with a travelling microscope. The three solutions used were sat. NH4H2PO4 (P/P0= 0·92), sat. Ba(NO3)2 (p/p0= 0·985), and water (p/p0= 1·0). X‐ray and water‐absorption measurements were also made on separate portions of the flakes at these values of p/p0. The density of the dry clay and the apparent density of the dry flake were determined. As the lateral swelling of the flakes was found to be very small compared with the swelling perpendicular to the general plane of orientation of the crystals, the distribution of air and water in the flakes could then be calculated at each value of p/p0.Up to p/p0= 0·985, 80 per cent. of the water absorbed by the flake was accounted for by the increase in the thickness of the water films on the clay crystals, the remaining water filling about half the pore space. On the basis of the total volume of the flakes, the total pore space was reduced by 12 per cent. at p/p0= 0·92 compared with the dry flake, due to expansion of the crystals, but then remained the same up to p/p0= 0·985. Between p/p0= 0·985 and 1·0, the pore space in the flake was filled and a further small expansion of the flake occurred, but the (001) spacing did not increase beyond 18·9 Å. Swelling in the vapour phase was unaffected by addition of I per cent. CTAB to the clay. The relation between macroscopic swelling and increase in water‐film thickness is consistent with the crystals being in the form of a tactoid.The swelling as p/p0→ 1·0 was much lower than that of a flake immersed in liquid water (see Part 2). It is suggested that this arises from the formation of polymolecular layers of water on the surfaces of the clay crystals, due to the influence of the exchangeable‐Ca ions which differ in structure from that of bulk water.
UPWARD MOVEMENT OF NITRATE IN A BARE SOIL IN UGANDA
Authors: STEPHENS D. 
Published: July 2006

SummaryThe levels of added chloride and nitrate in the topsoil of a well‐drained red clay loam have been measured throughout two dry seasons and evidence obtained that a small upward movement of dissolved salt can occur. The extent of this movement was not, however, sufficient to account for the observed accumulation of nitrate in the surface soil and it is concluded that the greater part of this nitrate was produced by some other process, such as microbial activity.
A STUDY OF ORGANIC SOIL HORIZONS USING ELECTROPHORETIC TECHNIQUES
Authors: MACKENZIE A. F. , DAWSON J. E. 
Published: July 2006

SummarySaturated sodium‐pyrophosphate extracts were obtained from samples of Sphagnum‐moss peat, sedimentary peat, fibrous peat, disintegrated peat, and muck and were subjected to electrophoretic separation and analysed for organic matter, polysaccharides, and coloured material. The resulting patterns indicated a marked difference between the muck samples and the peat samples. The high exchange‐capacity values obtained for muck samples were associated with the amount of highly charged material rather than with an increase in the charge density of this material. The muck and the fibrous‐peat samples appeared to be end members in a disintegration and oxidation sequence involving many intermediate stages.
AN EXAMINATION OF CATION BALANCE AND MOISTURE CHARACTERISTIC METHODS OF DETERMINING THE STABILITY OF SOIL AGGREGATES
Authors: COLLIS‐GEORGE N. , SMILES D. E. 
Published: July 2006

SummaryFor artificially reconstituted aggregates of soils low in organic matter the definitions of the stability of structure in terms either of cation balance and cation concentration of the ambient solution or of the drainage moisture contentsuction relationship characteristic after slow wetting are consistent.Identified factors of organic matter and of heating and drying (or drying alone) confer a structural stability on aggregates which can be detected by the moisture characteristic method. There is circumstantial evidence to suggest that the organic matter must be in equilibrium with vegetation.Since more than one factor affect structural stability, and since any particular method of distinguishing between different degrees of this stability may not necessarily suit the range of stabilities presented, the independent identification of soils, known to behave with differing aggregate structural stability in the field, is not necessarily possible with any laboratory method which describes changes in structural stability.
THE INFLUENCE OF IRON ON THE STABILITY OF SOIL ORGANIC MATTER DURING PEROXIDATION
Authors: OADES J. M. , TOWNSEND W. N. 
Published: July 2006

SummaryThe oxidation of soil organic matter by hydrogen peroxide is shown to be incomplete, the resistant organic materials causing sharp exothermic reactions at 300–340°C. during differential thermal analysis in an atmosphere of oxygen. Removal of the materials responsible for these exothermic reactions by treatments with sodium dithionite, sodium pyrophosphate, and acetylacetone followed by determination of iron in the acetylacetone extracts shows that iron is responsible for the stability of the organic materials, which are probably artefacts produced during the oxidative degradation of the soil organic matter.
THE DETECTION OF FERROMAGNETIC MINERALS IN SOILS AND CLAYS
Authors: OADES J. M. , TOWNSEND W. N. 
Published: July 2006

SummaryA method is described to measure the magnetic susceptibility of soils and clays using an analytical balance and a small magnet. Small amounts of ferromagnetic iron oxide occur in most soils and are concentrated in the clay fractions of surface horizons. Ignition of soil samples is shown to cause large increases in the magnetic susceptibility.
SELF‐DIFFUSION OF IONS IN SOIL
Authors: GRAHAM‐BRYCE I. J. 
Published: July 2006

SummarySelf‐diffusion coefficients for I‐ and H2PO‐4 in soils have been measured by determining the movement of radioactive tracers of these ions from a cylindrical section of labelled soil to a similar section initially without tracer. DI varied with the composition of the equilibrium soil solution used, both concentration and nature of cation affecting the value. These results may be explained by variations in the extent of negative adsorption of diffusing anions in the presence of negatively charged soil particles, and the consequent variation in the size of pore from which the anions are excluded.Phosphate diffusion was measured in the natural soil. The low values of DH2PO4 are attributed to adsorption and fixation of phosphate ions. Results obtained using different methods of phosphorus extraction and treatments designed to investigate effects of microbial activity are discussed.
SOLUBILITY STUDIES OF PHOSPHORUS IN SOME CALCAREOUS MANITOBA SOILS
Authors: WEIR C. C. , SOPER R. J. 
Published: July 2006

SummaryThe concept of chemical potential was applied in studying the form of soil phosphate present in some Manitoba soils. Generally for all the soils studied, the soil phosphates were more soluble than hydroxyapatite but less soluble than dicalcium phosphate dihydrate. Evidence was obtained for the existence of octocalcium phosphate in most of these soils. The effect of phosphate fertilization and per cent calcium carbonate on the form of native soil phosphate was also evaluated.
AN EXAMINATION OF SOME FACTORS AFFECTING THE MOVEMENT OF CLAY IN AN ARTIFICIAL SOIL
Authors: HALLSWORTH E. G. 
Published: July 2006

SummaryA preliminary study has been made of the extent to which clay can be moved by percolating solutions through various mixtures of sand and clay. The variations studied have been quantity of clay present, type of clay mineral, size distribution of the mineral skeleton, pH of the leaching solution and the nature of the cations present. The movement of the clay was restricted as the proportion present increased, and appeared to cease when the quantity exceeded 40 per cent for kaolinite clay or 20 per cent for montmorillonite clay. At these levels, however, a significant migration was found to occur down the cracks which develop when the soil is dried out. The movement of kaolinite increased continuously with increase in pH. The movement of montmorillonite increased to pH 10 or pH 11, and then rapidly diminished. The effects of the cations showed an interaction with the pH of the leaching solution.
STUDIES ON SOIL POTASSIUM
Authors: TINKER P. B. 
Published: July 2006

SummaryThe method of determining the activity ratio
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(AR) described by Beckett in Part II of this series was applied to a range of moderately to intensely acid Nigerian soils. With the highly acid soils it was necessary to add aluminium ions to the solution to obtain equilibrium. A method for obtaining the true equilibrium solution composition for K, (Ca±Mg), and A1 is described, and a series of typical results given. It was necessary to add benzene to prevent biological activity during sedimentation at 33° C. Altering the total concentration of the solution did not affect the activity ratio. A minority of soils showed evidence of transfer of potassium to non‐exchangeable forms during equilibrium. The slopes of the (exchangeable K)‐AR curves in a single soil were dependent on the amounts of soil Ca±Mg present. In comparisons between several soils, exchange capacity also had an effect. The Gapon equation was approximately correct for these soils over limited ranges.
INFLUENCE OF ORGANIC MATERIALS ON THE DETERMINATION OF THE SPECTFIC SURFACE AREAS OF SOILS
Authors: BURFORD J. R. , DESHPANDE T. L. , GREENLAND D. J. , QUIRK J. P. 
Published: July 2006

SummaryThe surface areas of a number of soils have been determined before and after removal of organic matter by treatment with hydrogen peroxide. The external area as determined by low‐temperature nitrogen adsorption increased after peroxidation. The total area derived from the nitrogen area and cetyl pyridinium bromide (CPB) adsorption generally decreased. Part of the clay‐organic complex was separated from some soils, and the external and total surface areas of this material before and after peroxidation determined similarly. Both the external and total areas increased after peroxidation. These results indicate that soils contain organic materials which are not part of the clay‐organic complex and which adsorb large amounts of CPB on surfaces not accessible to nitrogen molecules. A sample of peat showed a correspondingly high CPB adsorption and low nitrogen area. The large differences that occur in the nitrogen and CPB areas after peroxidation show the importance of removal of organic matter prior to the determination of the surface areas of soil clays. The surface areas were only slightly greater when carbon was completely removed by 30 per cent peroxide than when it was partly removed by 6 per cent peroxide. Organic compounds associated with the clay in the clay‐organic complex are apparently able to prevent access of nitrogen molecules to many of the clay surfaces, and also probably exclude CPB from some of these surfaces.
POLYPHENOLS IN PLANT, HUMUS, AND SOIL
Authors: DAVIES R. I. , COULSON C. B. , LEWIS D. A. 
Published: July 2006

SummaryThe leuco‐anthocyanin and tannin contents of green leaves of several species collected at mull sites have been compared with those collected at mor sites. Species growing under mor conditions usually contain greater amounts of both than the same species under mull. By growing a number of plants in sand it has been shown that this high content of polyphenolic substances can be associated with lack of nitrogen or of phosphorus.
THE DESCRIPTION OF RELIEF IN FIELD STUDIES OF SOILS
Authors: CURTIS L. F. , DOORNKAMP J. C. , GREGORY K. J. 
Published: July 2006

SummaryLandscape information relevant to site description is discussed. It includes surface form (in plan and profile), micro‐relief, aspect, height above sea level, and relative relief of the site in the local setting. Techniques for description of surface form are described which require the recognition and mapping of breaks and changes of slope bounding morphological units of the landscape. These units consist of ‘flats’ and ‘slopes’ that make up the facets of the landscape and may possess characteristic angles. The regional setting of the site is described by morphological map, values for drainage density and stream frequency, location with respect to drainage lines of a particular order, and the directional pattern of facets. Methods for the record of surface profiles by observation and measurement of small‐scale morphological units are described. A slope classification appropriate to British conditions is put forward.
THE MICROFLORA OF PEAT‐PODZOL TRANSITIONS
Authors: HOLDING A. J. , FRANKLIN D. A. , WATLING R. 
Published: July 2006

SummaryBacteria made up an average of 90 per cent of the microbial populations of twenty‐four soil samples, mainly of the A0H horizon, from four peat‐podzol transitions. Bacillus spp., which averaged 67 per cent of these bacteria, were usually the predominant group. Gram‐negative non‐spore‐forming organisms (15 per cent), Streptomyces (8 per cent), and Gram‐positive cocci (5 per cent) occurred irregularly and Arthrobacter and Nocardia strains rarely. A large proportion of the strains utilized glucose and malate, and a smaller proportion starch, citrate, and protein. A few strains liquefied pectin but none decomposed cellulose or xylan. In eight populations examined, 80 per cent of the bacteria required yeast extract for growth. Fungi usually formed only a small proportion of the populations. All the species, except Penicillium nigricans and Trichoderma viride, were isolated from only one transition. Yeasts occurred irregularly, usually in small numbers. Whilst no microbial group responded to the addition of glucose, nitrate, and phosphate to two soil samples, bacterial numbers increased after the addition of peptone and yeast extract.
EFFECTS OF AIR‐DRY, REFRIGERATED AND FROZEN STORAGE ON ACTIVITIES OF ENZYMES HYDROLYSING SUCROSE AND STARCH IN SOILS
Authors: ROSS D. J. 
Published: July 2006

SummaryActivities of enzymes hydrolysing sucrose and starch were lowered significantly in all air‐dried soils, except some naturally arid soils, stored at room temperature by more than 20 per cent and 50 per cent respectively, compared with values for fresh soils. These reductions in activities resulted mainly from the initial drying which also appreciably reduced the numbers of viable bacteria. Activities of enzymes hydrolysing sucrose generally decreased on storage at −20° C but changes were slight over long periods. Inactivation of enzymes hydrolysing starch was greater and tended to increase with length of storage. Inactivation was due partly to the effects of freezing and thawing and was greater in dry than in moist samples of soils. Activities were changed least by storage at 4° C and a significant decrease from fresh values was found occasionally in only two of the thirteen soils. Starch‐hydrolysing activity was significantly increased in two very moist soils stored for 41 weeks, probably due to germination of a few seeds. Although different soils can differ in their storage behaviour, storage in a refrigerator is most suitable and air‐drying least suitable for subsequent assays of these enzymes.
SOLUBLE AND EXCHANGEABLE CATION RATIOS IN SOME SOILS OF ISRAEL1
Authors: LEVY RACHEL , (MURAVSKY) E. MOR 
Published: July 2006

SummarySodium‐absorption ratio–exchangeable sodium ratio relationship was tested on some Israeli profiles. Two approaches were used: firstly, a survey on existing relationship in about 250 soil samples representing twenty soil types, and secondly, a comparison of the exchange isotherms of five soil types obtained by a batch equilibrium procedure. The results of the survey extended over a small range of S.A.R., a fact which was an obstacle for making any conclusions. By the second approach it was found that the examined soil types showed a difference in their exchange properties. Determination of the exchange isotherms and calculation of the parameters for each soil separately gave a better insight into their exchange behaviour.
THE INFLUENCE OF TEXTURE ON THE MOISTURE CHARACTERISTICS OF SOILS
Authors: SALTER P. J. , WILLIAMS J. B. 
Published: July 2006

SummaryThe available‐water capacity of the top 2 ft of twenty‐seven soils of different texture has been determined, together with the moisture release characteristics of twenty of the soils. The moisture contents at field capacity and at the permanent wilting point increased as the soils became finer in texture but the medium‐textured soils held the greatest volume of available‐water. The available‐water capacities of the soils ranged from 0.77 in./ft depth in a sand to 3.12 in./ft in a silt loam and 3.13 in./ft in a peat. Clay soils held approximately 1.95 in./ft. The effects of soil texture and other factors affecting the available‐water capacities and moisture release characteristics of soils are discussed.
CLASSIFICATION OF SOILS BY NUMERICAL METHODS
Authors: RAYNER J. H. 
Published: July 2006

SummaryTwenty‐three profile descriptions of soils in Glamorganshire and the laboratory measurements on soil samples of the ninety‐one horizons into which they were divided by the surveyor were examined by the methods of numerical taxonomy. The similarities between the horizons calculated by these methods were reduced to a table of similarities between profiles by averaging the similarities of those horizons that matched best, judged by their similarity and order in the profile. The soil‐similarity matrix was sorted to give a dendrogramme. Calculation of the latent roots and vectors of the matrix gave a two dimensional representation of the relationships between the soils. The Great Soil Groups to which the surveyor assigned his profiles can be picked out in this diagram.