bluuebunny/crossref_metadata_2025_split huggingface dataset:
INCREASES IN THE CARBON AND NITROGEN CONTENTS OF TROPICAL SOILS UNDER NATURAL FALLOWS
Authors: GREENLAND D. J. , NYE P. H. 
Published: July 2006

SummaryThe rate of increase of humus carbon in soils rested under natural fallows has been calculated, assuming that the rate of decomposition of the humus carbon is proportional to the amount present, and that the rate of addition, by humification of litter and roots, remains constant. The rate of decomposition has been derived from a knowledge of the maximum humus level the soil attains under the fallow vegetation, and the rate of addition has been estimated from data on litter production. The rate of increase of nitrogen has also been calculated assuming that the C/N ratio in the soil remains constant. Under the native practice of shifting cultivation in forest the alternation of cropping and fallowing leads to relatively small fluctuations in soil humus at about 75 per cent. of the maximum level. The rates of increase of soil nitrogen at this level are between 20 and 50 lb. per acre per annum in forest and 4 and 10 lb. per acre per annum in savannah. Rates at other levels for which the assumptions made are valid may readily be calculated from the data presented. It is shown that provided vegetation re‐establishes itself rapidly a crop: fallow ratio of about 1:3 should maintain the humus level in forest soils at the 75 per cent. of equilibrium level, a result which accords well with experience.
DETERMINATION OF ORGANIC CARBON IN SOIL AND PLANT MATERIAL
Authors: SHAW K. 
Published: July 2006

SummaryA wet‐oxidation technique for determining organic carbon in soil, plant material, and aqueous plant extracts is described. The oxidation is carried out by heating the soil or plant sample (containing 50–100 mg. carbon) with a mixture of potassium dichromate, sulphuric, and phosphoric acids for 10–15 min., and the carbon dioxide liberated is determined gravimetrically after absorption in soda‐lime. With slight modifications, the method has proved useful for the determination of carbon in plant extracts and would also appear suitable for a soil extract. A method is described for the removal of carbonates without loss of organic carbon. It is shown that heating a wet soil at 105° C. causes considerable loss of organic carbon. Inert carbonaceous material, such as coal or charcoal, is oxidized by this wet‐digestion method, thus producing erroneously high results for the carbon content of soil organic matter.The method is at least as accurate as the conventional dry‐ combustion technique, and is less time‐consuming, only one hour being required for a determination. The apparatus is of simple design and with the exception of the needle valve can be readily constructed from normal laboratory glassware. The method can deal with fairly large samples of materials, thus preserving an essential feature of established macro‐methods.This technique of determining carbon is convenient for the fairly rapid analysis of soils and plant materials where an accurate total‐carbon value is required.
THE STONY TABLELAND SOILS OF THE SOUTHEASTERN PORTION OF THE AUSTRALIAN ARID ZONE AND THEIR EVOLUTIONARY HISTORY
Authors: JESSUP R. W. 
Published: July 2006

SummaryThe stony tableland soils which are paleosols of Quaternary age have a clay profile, high proportion of exchangeable sodium, strong salinity, large amounts of stone in the upper few inches of the profile, a surface stone pavement, low carbonate but high gypsum contents and gypsum at shallower depths than carbonate. The surface of the soil layer has a gilgai micro‐relief.The soils formed on deposits of wind‐blown clays. Underlying the soil layer is a discontinuous layer of wind‐deposited gypsite. These wind‐blown materials (called lakulangite) were derived from lacustrine sediments; deflation of these sediments led to the formation of wind‐excavated hollows that are often of large extent.Stones originally buried beneath the clay deposit have been moved upwards and concentrated on or near the soil surface.
LATERITES AND LATERITIC SOILS IN SOUTH‐WESTERN AUSTRALIA
Authors: MULCAHY M. J. 
Published: July 2006

SummaryA short general account of the distribution and characteristics of the laterites of south‐western Australia is given in relation to past and present climates and to climatically controlled processes of landscape development.A number of erosional and depositional surfaces have been identified near York, Western Australia, the older of which are lateritic, and the characteristics of the laterites and the soils associated with them have been shown to vary with the age of the land surface on which they occur. Extensive sandy deposits derived by the weathering and stripping of the ferruginous horizons of the laterites have been recognized. It is suggested that the 'sand plains' of Western Australia, hitherto considered to be intact or only slightly modified fossil laterites, originated in this way.
COMPOSITION OF THE solUBLE AND EXCHANGEABLE IONS OF THE SALTY SOILS OF THE MIRROOL IRRIGATION AREA (NEW SOUTH WALES)
Authors: GROENEWEGEN H. 
Published: July 2006

SummarySalty soils of the Mirrool Area were found to be formed mainly by salt accumulation from lower soil layers. Under these conditions saline soils, or saline‐alkali soils containing gypsum, were generally formed. The exception was one profile in which precipitation of carbonates had resulted in the formation of a saline–alkali soil not containing gypsum.The soluble Na+ percentage increased and the soluble Ca++ percentage decreased with depth in all but one profile. A high variability of these percentages in the A and B, horizons was attributed to precipitation of divalent ions, and application of fertilizers.Some saline soils were base unsaturated. These soils had a high soluble Na+ percentage, but had absorbed only small amounts of Na+. Laboratory tests showed that permeability was reduced more in base unsaturated than in base saturated soils when exchangeable Na+ was 10 per cent or higher. The relevance of these findings to the classification of salty soils is briefly discussed.
LATERITE AT THE TYPE LOCALITY, ANGADIPURAM, ICERALA, INDIA
Authors: STEPHENS C. G. 
Published: July 2006

SummaryLaterite at the type locality, Angadipuram in south India, consists of a mottled, vermicular, and indurated horizon in a red‐earth type of soil associated with gneiss. The soil profile also contains deeper horizons of mottled and pale coloured clays and has a ground‐water table. The laterite is associated with a number of discrete land surfaces described in detail by Lake (1890).
A METHOD FOR THE MEASUREMENT OF THE CALCIUM DEFICIT IN SALINE SOILS
Authors: SCHOFIELD R. K. , TAYLOR A. WORMALD 
Published: July 2006

SummaryThe calcium deficit of a saline soil is defined as the amount of calcium which must be supplied to saturate the soil with divalent cations. A method is described whereby this amount can be measured in samples of unwashed saline soil and used to estimate the amount of gypsum needed in the field to prevent deterioration of the soil structure while it is being leached into a salt‐free condition.
THE SALT LAKE SYSTEMS AND THEIR ASSOCIATED AEOLIAN FEATURES IN THE SEMI‐ARID REGIONS OF WESTERN AUSTRALIA
Authors: BETTENAY ERIC 
Published: July 2006

summaryWind action has modified relics of river systems which drained the southern and central parts of Western Australia. Dunes of both coarse crystalline and fine floury gypsum and lunettes of sand, silt, or clay size material are common near to the leeward margin of salt lakes. Further removed, materials, blown out from the lake areas as aggregates of clay, silt, and sand, are deposited as sheets which are medium‐textured and have a high lime content. The latter deposits have been termed lake parnas.
THE SWELLING OF CA‐MONTMORILLONITE DUE TO WATER ABSORPTION
Authors: EMERSON W. W. 
Published: July 2006

SummaryStarting with orientated flakes of dry Ca‐montmorillonite (Wyoming bentonite) about 0·2 mm. thick, the swelling of the flakes when immersed in 2 M CaCl2 was measured with a travelling microscope. The further expansion when the flakes were brought into equilibrium with successively more dilute CaCl2 solutions was also measured. The swelling of the flakes in 2 M CaCl2 was equal to that of flakes equilibrated with saturated water vapour. As the CaCl2 concentration was reduced the flakes swelled progressively, with negligible increase in the (001) spacing. This swelling was independent of the pH of the CaCl2 solutions and could not be reversed by increasing the concentration of CaCl2. Flakes prepared from clay suspensions to which 1 per cent. of CTAB had been added did not swell in dilute CaCl2 solutions.Measurements were made of the swelling of flakes under an applied suction. Suction reduced the swelling as compared with free solution, and the swelling was less sensitive to CaCl2 concentration. There was some hysteresis in swelling between the wetting and drying cycles.The results are consistent with the swollen Ca‐montmorillonite being in the form of a tactoid, the arms of the tactoid consisting of the clay crystals aggregated end to end. Swelling is due to the development of double layers between crystals in the pores of the tactoid. The linkages at the joints of the tactoid arise because either there is perfect orientation between the crystals at these points or there is a small number of complex ions (≤ I m.e./100 g. clay) other than Ca‐ions present on the external surfaces of the crystals. CTA+ ions, being strongly absorbed by the clay, increase the number of such linkages, so inhibiting double‐layer swelling. Whether or not Ca‐montmorillonites in general exhibit double‐layer swelling will depend critically on how many ions other than Ca‐ions are present on the clay.
THE SOIL BELOW A TERMITE MOUND
Authors: WATSON J. P. 
Published: July 2006

SummayConcentric cones of whitened soil extend approximately 20 ft. below a termite mound in Southern Rhodesia. The pale colour is due to finely divided carbonates; the outer cone contains about 4 per cent. carbonates whilst the inner cone, riddled with termite galleries, has about 2 per cent. carbonates. The pH pattern shows highest values in the inner cone due to the presence of sodium salts. Termite activity thus gives rise to calcareous and sodium‐influenced soils in an area of leached ferrallitic soils.Physically, the soil below the mound has the same arrangement of horizons as the surrounding ferrallitic soils, namely, mineral material (M horizon), over a stone horizon (S horizon), over weathering granite (W horizon). The overlap of the inner cone and horizon W indicates that this arrangement of horizons has been brought about in part by termites carrying material up from the W horizon through the S horizon to the M horizon or mound at the surface.Termite activity has thus influenced both the pattern of salt distribution and mineral‐soil horizons.
SOIL AND IRRIGATION CLASSIFICATION OF SHALLOW SOILS OVERLYING GYPSUM BEDS, NORTHERN IRAQ
Authors: SMITH R. , ROBERTSON V. C. 
Published: July 2006

SummaryRecent reconnaissance soil surveys of proposed irrigation projects have revealed a belt of shallow soils overlying gypsum beds in the drier steppe zone of Northern Iraq.The soil profile consists of two sharply contrasting layers—upper layer of Mesopotamian Alluvium and a lower layer of highly gypseous material. The Mesopotamian Alluvium is a brown fine‐textured material, highly calcareous but very low in soluble salts, exchangeable sodium, and gypsum. The gypseous beds underlying this shallow soil mantle are relatively soft tertiary sediments (Fars beds) or their erosion products.Despite abundant evidence of the non‐toxicity of gypsum even in saturated solutions, observations on naturally occurring gypseous soil in steppe areas of Iraq and the U.S.S.R. show that root growth is inhibited where the gypsum content is 10 to 25 per cent, or higher, apparently because of poor transmission of air and water associated with bad structure.Agronomic and engineering problems were considered, together with U.S. data on rooting systems of climatically adapted irrigated crops, in arriving at a classification.
WEATHERING OF SOME SCOTTISH BASIC IGNEOUS ROCKS WITH REFERENCE TO SOIL FORMATION
Authors: SMITH WILMA W. 
Published: July 2006

SummaryThe weathering of several basic igneous rocks of Lower Carboniferous age has been studied by optical microscopy and X‐ray techniques. Although similar in mineralogy, the rocks have different textures and the fine‐grained ones are most resistant to physical disintegration. In every rock, olivine has been affected by hydrothermal alteration to produce layer lattice silicates. The weathering of these products and the other mineral constituents of the rocks is described.The fine‐sand fraction (0·2‐0·02 mm.) was selected for the purpose of determining relative stabilities of the primary minerals under weathering conditions. In order of increasing stability, the arrangement is labradorite, augite, magnetite, ilmenite, and hematite. The silt (0·02‐0·002 mm.) and clay (< 1.4 μ) fractions contain saponite and/or vermiculite depending mainly on the weathering conditions of augite and felspar. Kaolin is present in both size fractions but illite is scarce. The cation‐exchange capacity (c.e.c.) of both silt and clay fractions is consistent in most cases with the layer lattice silicate contents.
SOIL SURVEY AS RELATED TO AGRICULTURAL PRODUCTIVITY
Authors: VINK A. P. A. 
Published: July 2006

SummaryEven in early times not only the growth of the crops but also the costs of their production played a certain role. Also the suitability of soils for various crops has always been changing according to economic circumstances (prices of products) and changes in technology.Land‐use is greatly influenced by historical developments. These reflect the various economic and technical circumstances of the past. A survey of present land‐use can never be a basis for predictions on optimum land‐use. The Soil Survey is the only basis for these predictions.Present thought on land‐use is also very strongly influenced by the chemical schools of soil science which played such a dominant role in the recent past. The soil surveyor should co‐operate with experts on soil chemistry and soil fertility to stimulate optimum agricultural productivity under present conditions.In this changing world, land‐use is going to change rapidly, because economic and technical circumstances alter from day to day. The soil surveyor must demonstrate the different repercussions which these changes will have on his different soil types. He is the only man who can predict which surface areas are going to be affected by various changes of prices and of agricultural techniques. In this he must co‐operate with farm economists and with agricultural engineers.The soil surveyor cannot leave this work to others, because he is the only man who fully understands the terminology of the soil map and because he is also the only man who can handle his soil units as natural units. Furthermore, he should do this because it gives him a better understanding of the units which he is mapping and therefore the quality of his soil maps will also be improved.
THE MICROBILOGY OF ROCKS AND WEATHERED STONES
Authors: WEBLEY D. M. , HENDERSON MOIRA E. K. , TAYLOR IRENE F. 
Published: July 2006

SummaryA study has been made of the microbiology of rock surfaces and weathered stones. Increasing numbers of micro‐organisms were found with increasing degree of colonization by lichens, for example, of rock surfaces. The highest numbers were generally found in‘raw’ soil in rock crevices where the organic‐matter content was high. Bacteria, actinomycetes, and fungi were also found in the interior of porous weathered stones but not in unweathered stones. A high proportion of the organisms isolated were able to render silicates soluble when tested in pure culture in the laboratory.
MICROMETEOROLOGICAL OBSERVATIONS IN AN AFFORESTED AREA IN ABERDEENSHIRE: RAINFALL CHARACTERISTICS
Authors: ARANDA J. MARTIN , COUTTS J. R. H. 
Published: July 2006

SummaryRainfall was measured at an open site and under spruce, pine, and heather. Between 50 and 60 per cent. of the rain penetrated each of the canopies. Variations in the percentage penetration are associated with the area of foliage to be wetted and with the aggregate amount and the intensity of the rainfall.
TRACE ELEMENTS IN SOME WELSH UPLAND SOILS
Authors: ARCHER F. C. 
Published: July 2006

SummaryUpland Welsh soils of rhyolitic origin contained less total Co, Cr, Cu, Ti, and V, more total La and Rb, and less acetic‐acid‐extractable Co and Cr than soils derived from dolerite, pumice tuff, and mixed drifts. Except for the surface enrichment of Pb, pedological factors appear to have had little effect on the distribution of total or extractable trace elements within these immature soils.
DIRECT DETERMINATION OF INORGANIC SOIL PHOSPHATE
Authors: PARTON D. J. 
Published: July 2006

SummaryMany limitations of conventional methods for determining inorganic soil phosphate have been overcome by employing an isotopic dilution technique. Mobilization of soil inorganic phosphate fractions was achieved by using a solution buffered to pH 1·0 and containing orthophosphate labelled with phosphorus‐32. The inorganic phosphate thus mobilized was determined after the attainment of equilibrium between the applied and soil phosphate. Good correlation was obtained between values determined as above and those by difference between total and organic soil phosphorus. Factors influencing equilibration rate were studied: temperature, soil particle size, and soil: solution ratio.
A METHOD OF STUDYING TRACE ELEMENTS IN SOIL FRACTIONS
Authors: LE RICHE H. H. , WEIR A. H. 
Published: July 2006

SummaryA method is described for dividing soils into iron oxide, sand, silt, and clay fractions suitable for trace‐element analysis. The oxides are extracted under ultra‐violet light by ammonium oxalate (pH 3·3), which dissolves goethite and other iron oxides but not gibbsite or boehmite; it also extracts some soil organic matter and, probably, trace elements associated with it.Two horizons of two brown earths were analysed spectrochemically for Ba, Co, Cr, Cu, Ga, Mn, Ni, Pb, Sr, Ti, V, and Zr. The extracted oxides were the fractions richest in trace elements and contained large proportions of the total Co, Cu, Mn, Pb, and V. Except for Sr, Ti, and Zr, the amounts of trace elements in the sands were small and were distributed between the silicate‐mineral fractions in the order: sand > silt > clay. About half of the total Zr was in the sand fractions but appreciable amounts were in the extracts and clays. Increases of iron oxide and clay in the illuvial B horizons were paralleled by increases in the amounts of Ba, Cr, Co, Ga, Ni, and V.
THE RELEASE OF METALLIC AND SILICATE IONS FROM MINERALS, ROCKS, AND SOILS BY FUNGAL ACTIVITY
Authors: HENDERSON MOIRA E. K. , DUFF R. B. 
Published: July 2006

SummaryThe decomposition of silicate minerals and related substances by fungi has been investigated using two techniques: (a) the incorporation of the mineral material in agar medium, when its breakdown is indicated by the formation of clear zones round the fungal growth; (b) the determination of the metal and silicate ions, derived from the insoluble materials and brought into solution as a result of fungal activity in liquid medium. Strains of fungi which produced citric and/or oxalic acid proved to be effective in decomposing certain natural silicates, while an oxalic acid‐producing strain also released metallic ions and silica from rocks and soils. A possible role of fungi in biological weathering is discussed.
THE USE OF VAPOUR‐PRESSURE AND MOISTURECONTENT MEASUREMENTS TO DEDUCE THE INTERNAL AND EXTERNAL SURFACE AREA OF SOIL PARTICLES
Authors: FARRAR D. M. 
Published: July 2006

SummaryA procedure for calculating both the external and total areas of soil particles from the relation between vapour pressure and moisture content is tested experimentally for four British clay soils. The calculated surface areas are compared with those obtained by the standard procedure from measurements using both water vapour and nitrogen, and their relation with the mineralogy of the clay fraction of the soil (as determined by X‐ray analysis) is examined. It is concluded that this new method is sufficiently accurate to be used as an indication of the clay mineralogy.
TOXICITY AS A CAUSE OF THE INEFFICIENCY OF UREA AS A FERTILIZER. I. REVIEW
Authors: COURT M. N. , STEPHEN R. C. , WAID J. S. 
Published: July 2006

SummaryThe causes and mechanisms of phytotoxicity that can bring about poor or adverse crop responses to applications of solid urea to soil are reviewed. Compounds which may cause phytotoxicity are urea, transformation products of urea formed during manufacture (biuret), and transformation products produced in the soil or in plants (cyanate, carbamate, ammonia, and nitrite). Of these, ammonia and nitrite are considered to be the most likely causes of phytotoxicity when urea of low biuret content is used.
ALUMINIUM AND IRON PHOSPHATE STUDIES RELATING TO SOILS
Authors: BACHE B. W. 
Published: July 2006

SummaryThe determination of ion activities in solution during the sorption of phosphate on to gibbsite and hydrous ferric oxide has shown three stages to the reaction: (i) a high energy chemisorption of small amounts of phosphate; (ii) precipitation of a separate phosphate phase; (iii) a low energy sorption of phosphate on to the precipitate. The values of ion activity products for the precipitation reaction do not correspond with the solubility constants of variscite and strengite. Ion activity products are not likely to be useful for indicating the existence of separate A1 and Fe phosphate phases in soils. The variation of solution phosphate activity with phosphate sorbed is suggested as a basis for a ‘phosphate characteristic’ curve for phosphate‐reactive heterogeneous systems.
CATION‐EXCHANGE EQUILIBRIA WITH VERMICULITE
Authors: WILD A. , KEAY J. 
Published: July 2006

SummaryThe exchange of Na, Mg, Ca, Sr, and Ba ions has been studied in the temperature range 25° C‐70° C.Vermiculite shows a preference for divalent ions over Na ions at 25° C and the preference increases very greatly at higher temperatures. The preference is largely determined by the increase in entropy which accompanies the replacement of monovalent ions by divalent ions in the vermiculite. Preference is less marked between divalent ions. These ions are similarly hydrated in vermiculite, which differs in this respect from resins and most other clay minerals. The greater affinity of Mg ions compared with other divalent ions is explained by their closer approach to the silicate surfaces.
THE MOBILIZATION OF IRON BY AQUEOUS EXTRACTS OF PLANTS
Authors: MUIR J. W. , MORRISON R. I. , BOWN C. J. , LOGAN J. 
Published: July 2006

SummaryAs a first step in identifying the agents responsible for the mobilization of ferric iron by an aqueous extract of pine needles, the extract is divided into three fractions, an amino‐acid fraction, an organic‐acid fraction, and a neutral fraction. The principal constituents of the amino‐acid and organic‐acid fractions are then identified and their contents determined by means of paper and column chromatography.
THE INFLUENCE OF TEXTURE ON THE MOISTURE CHARACTERISTICS OF SOILS
Authors: SALTER P. J. , WILLIAMS J. B. 
Published: July 2006

SummaryWhen the 1/3 and 15 atm. percentages were used as the upper and lower limits of available‐water, respectively, the values for the available‐water capacities (AWC's) of the soils studied were smaller than those obtained by using the direct sampling technique for the upper limit, and the permanent wilting percentage (determined on soil cores) for the lower limit of available‐water; the differences varied from 9 to 76 per cent with a mean of almost 40 per cent for the eleven soils studied. The importance of techniques for the determinations of the AWC of soils is discussed. The moisture characteristic of a soil could be considerably influenced by the structure of the soil sample on which the determination was made, and it is concluded that the moisture characteristic should be determined on undisturbed soil cores.