bluuebunny/crossref_metadata_2025_split huggingface dataset:
A BASIS FOR THE CLASSIFICATION OF SOIL
Authors: MACVICAR C. N. 
Published: July 2006

SummaryConsidering the nature of soil and the ends which a classification must serve, principles are stated whereby a soil classification may be devised for application over extensive areas of varied soil composition.Naturally occurring bodies of soil, each with a high degree of homogeneity, are apparent rather than real individuals as their properties overlap to form a continuum. This continuum is multi‐dimensional because soil is characterized by numerous properties. The procedure of devising a classification is one of subdividing the continuum such that class boundaries accommodate, as far as possible, apparent individuals rather than of grouping like apparent individuals together.A classification may be used to locate the position of a profile in the continuum and so define its relationship with other profiles. It may also be used to indicate the soil composition of land by using soil classes on a map to show differences in the soil mantle. The latter procedure may best be regarded as land classification or soil mapping rather than soil classification; a class of land or mapped area seldom contains profiles belonging exclusively to a single class, whereas a soil class never contains profiles of another class.The soil form, a specific arrangement of diagnostic horizons, is introduced as a category above the series to facilitate the identification of soil profiles. Member series of a form are defined according to property variations within the diagnostic horizons of the form. It is suggested that a binomial system of profile nomenclature, using the form and the series, would have much to commend it.
THE EFFECT OF THE CONCENTRATION AND MOVEMENT OF SOLUTIONS ON THE SWELLING, DISPERSION, AND MOVEMENT OF CLAY IN SALINE AND ALKALI SOILS
Authors: ROWELL D. L. , PAYNE D. , AHMAD N. 
Published: July 2006

SummaryChanges in permeability of a soil containing montmorillonite, and the swelling of orientated aggregates of extracted clay have been measured for a range of exchangeable sodium percentages and electrolyte concentrations. The concentrations at which clay moved out of the soil in the percolates have been found and compared with the concentrations at which aggregates dispersed in stationary solutions, and the concentrations at which soil suspensions dispersed when shaken.The results indicate that: (a) permeability begins to decrease at the same concentration as the clay begins to swell, (b) the changes in permeability are directly controlled by the swelling of clay until clay dispersion and movement begins, (c) the concentration at which clay disperses depends on the mechanical stress applied, (d) when small mechanical stresses are applied, the proportion of the clay which swells and disperses depends directly on the exchangeable sodium percentage, and (e) large mechanical stresses may disperse most of the clay even at low exchangeable sodium percentages.
THE TIMES REQUIRED FOR THE ATTAINMENT OF AIR‐WATER EQUILIBRIUM IN CLAY SOILS
Authors: SIDES G. R. , BARDEN LAING 
Published: July 2006

SummaryThe coefficient of diffusion of air through the pore water of clay soils has been measured directly and has been shown to be markedly less than for free water and to decrease with water content.It has been shown that these low coefficients of diffusion are not accounted for by the sinuosity of the flow channels, or by any important departure from Henry's law of solution at curved air‐water interfaces. The main factors appear to be constrictions in the flow channels and the reduced viscosity of the adsorbed water. It is concluded that air‐water equilibrium in partly saturated soils will be attained much more slowly than is generally assumed.
INORGANIC SOIL PHOSPHORUS
Authors: WEBBER M. D. , MATTINGLY G. E. G. 
Published: July 2006

SummarySixteen soils and 4 soil preparations were cropped exhaustively with ryegrass in the glasshouse and monocalcium phosphate potentials (½pCa+pH2PO4=1) were measured after each of 6 consecutive harvests. The amounts of phosphorus (Q) removed from the soils by ryegrass accounted for 95·1–96·6 per cent of the variance in 1 for 3 soils and 2 soil preparations (P < 0·001), for 88·4–93·7 Per cent of the variance for 6 soils and 2 soil preparations (0·001 < P < 0·01), for 71·6–82·6 per cent of the variance for 3 soils (0·01 < P < 0·05) and for insignificant amounts of the variance for 4 soils. Values of ΔI/ΔQ ranged from 7 × 10–4 to 431 × 10–4½pCa+pH2PO4/ppm P removed from soil.ΔI/ΔQ tended to decrease (i.e. the soils were more buffered) with increasing clay contents and with increasing amounts of NaHCO3‐soluble P and to increase (i.e. the soils were less buffered) with increasing amounts of CaCO3. Variations in organic C did not significantly affect ΔI/ΔQ. The following equation accounts for 81 per cent of the variance in ΔI/ΔQ for all soils except those in equilibrium with octacalcium phosphate:ΔI/ΔQ× (104) = 225·9–4·17(% clay)+8·01(% CaCO3)–1·38(ppm NaHCO3‐soluble P).
INORGANIC SOIL PHOSPHORUS
Authors: WEBBER M. D. , MATTINGLY G. E. G. 
Published: July 2006

SummaryMixtures of Woburn (non‐calcareous) and Barnfield (calcareous) soils, with and without added monocalcium phosphate, and of Woburn soil with added CaCO3, were stored moist in an incubator at 25 ± 2 °C. Equilibrium phosphate concentrations in 0·01M CaCl2 and pH were measured on moist soils and mono‐calcium phosphate (½pCa+pH2PO4) and lime (pH–½pCa) potentials were calculated at intervals up to 670 days. Most of the mixtures remained under‐saturated with respect to CaCO3; values of ½pCa+pH2PO4 and pH–½pCa changed during storage but remained close to the solubility isotherm for octacalcium phosphate (OCP). Mixtures which reached equilibrium with CaCO, remained undersaturated with respect to OCP.
EFFECTS OF GREEN MANURING, FARMYARD MANURE, AND STRAW ON THE ORGANIC MATTER OF SOIL AND OF GREEN MANURING ON AVAILABLE NITROGEN
Authors: CHATER MARGARET , GASSER J. K. R. 
Published: July 2006

SummaryIn an experiment on green manuring started at Woburn in 1936, farmyard manure (FYM) was applied in alternate years until 1954 and straw similarly from then until 1963. Various green manures were grown from 1936 to 1953. From 1954 to 1963 ryegrass and trefoil were grown either each year or in alternate years; in 1964 and 1965 they were grown each year.After annual cropping without organic manuring the organic‐C and total‐N decreased from 0·86 per cent and 0·091 per cent respectively in 1936 to 0·76 percent and 0·082 per cent in 1966. Ploughing in straw alone approximately halved the loss. FYM and green manures both maintained the original percentages of soil C and N. The effect of FYM and straw applied together was approximately the sum of the effects of FYM and straw applied separately.Of the green manures ploughed in, trefoil returned the most nitrogen to the soil. Trefoil increased and ryegrass decreased the mineralizable‐N in the soil.
CONTENT OF INOSITOL PHOSPHATES IN SOME ENGLISH AND NIGERIAN SOILS
Authors: OMOTOSO T. I. , WILD A. 
Published: July 2006

SummaryThe mono‐, di‐, tri‐, tetra‐, penta‐, and hexaphosphates of inositpl accounted for between 11·2 and 30·4 per cent of the organic P in three English and four Nigerian soils. M yoinositol hexaphosphate was the component present in greatest amount in all soils. The lower esters (mono‐, di‐, and triphosphates) accounted for less than 3 per cent of the organic P in all soils, with the lowest amounts in the soils from Nigeria. For the penta‐ and hexaphosphates the ratio of myo‐ plus dl‐ isomers to scyll oinositol varied from 2·9 to over 10, the highest ratio occurring in the soils from Nigeria.Examination of the techniques showed that they gave approximately correct estimates of the inositol phosphates. The organic P in soil which was not estimated as inositol phosphate occurred in other forms.
QUANTITATIVE PEDOLOGICAL STUDIES ON SOILS DERIVED FROM SILURIAN MUDSTONES
Authors: STEWART V. I. , ADAMS W. A. , ABDULLA H. H. 
Published: July 2006

SummaryConsiderable variations in the apparent density of the fine earth fraction were recorded in stony soils in Cwmcadian, Merionethshire. A highly significant relationship between fine earth apparent density and stone content was observed which was not caused by disturbance during sampling. The relationship could be predicted by assuming that the bulk volume of a stony soil approximates to the sum of the self‐packing volumes of the separated stone and fine earth components. It is suggested that in natural soils there is a similar relationship between soil apparent density and organic matter content, namely that the bulk volume of a soil containing organic matter approximates to the summed self‐packing volumes of the mineral and organic components.
SOIL WATER MEASUREMENT BY A LOW‐RESOLUTION NUCLEAR MAGNETIC RESONANCE TECHNIQUE
Authors: PREBBLE R. E. , CURRIE J. A. 
Published: July 2006

SummaryA low‐resolution nuclear magnetic resonance analyser was used to measure soil water. The physical principles of the method are outlined to enable the non‐linearity of the response to water to be discussed. Two sands, five soils, and vermiculite were tested in the Laboratory. The instrument readings for all were depressed below the values that might have been expected from absolute water contents. In sands the depression increases with water content, that is, as pores of progressively larger size fill with water. In clay soils an initial depression is attributable to the rigidity with which the first small amounts of water are adsorbed on to the clay lattice: with more water the depression, as in sand, reflects the size distribution of the macropores.‘Relaxation’, a condition needed to ensure accuracy, can be induced by adding iron compounds and salts, but there is evidence that where these substances are present naturally in the soil they may cause different degrees of relaxation from soil to soil. When many soil samples of known type, structural state, and chemical status have to be analysed, a good calibration curve can be obtained and used to give water contents to a fraction of a per cent. A moisture characteristic was measured on a sand to assess the ability of the instrument to scan moisture profiles in long columns.
EDAPHOIDS AND PALEOSOLS OF BASALTIC ORIGIN IN THE GALILEE, ISRAEL
Authors: SINGER ARIEH 
Published: July 2006

SummaryRed soil‐like layers intercalated amid basaltic flows from the Miocene‐Pleistocene in the Galilee, Israel, were examined. Micromorphological features which can be related to (a) translocation of materials, and (b) biological activity, and are therefore of distinct pedological origin, identify two of the layers as paleosols. Absence of these features and preservation of the fabric of the parent basalt serve to identify the third layer as an edaphoid. A fourth layer consists of an edaphoid superimposed on a paleosol. The edaphoids are composed almost entirely of a dioctahedral smectite. In two of the paleosols dioctahedral smectites predominate. In the third kaolinite and haematite are present also in considerable amounts. The presence of quartz in the paleosols is attributed partly to precipitation from Si‐rich solutions percolating the upper basalt layer and partly to aeolian contamination. In all the layers the free iron is predominantly in an anhydrous form. Similarity in the clay mineral composition of the Plio‐Pleistocene paleosols with that of contemporaneous basaltic soils is taken to indicate similarity in climatic conditions of formation. Differentiation between paleosols and edaphoids cannot be made by the use of a single criterion but must be based on corroborative evidence derived from micromorphological and mineralogical examinations.
THE STABILITY OF DICALCIUM PHOSPHATE DIHYDRATE IN SOIL
Authors: PROBERT M. E. , LARSEN S. 
Published: July 2006

SummaryThe rate of dissolution of labelled dicalcium phosphate dihydrate (DCP) of different particle sizes was measured by crop uptake and by extraction with phosphate solution.Powdered DCP (< 0·18 mm) behaved similarly to monocalcium phosphate (MCP) throughout but larger particles dissolved more slowly and their availability increased with time. The 0·18–0·35, 0·35–0·7, and 0·7–1·4 mm fractions became more available than the equivalent rate of MCP during the growing period of 103 days. Such behaviour is predictable on the basis of a dissolutionimmobilization mechanism.
DETERMINATION OF THE CONTENTS OF CLAY‐SIZED PARTICLES IN SOILS
Authors: EMERSON W. W. 
Published: July 2006

SummaryEdwards and Bremner's (1967) technique of dispersing soils by Bonification to form stable suspensions for particle‐size analysis without the addition of dispersant has been tested on a range of soils and a chalk. Carbonate soils or acid soils, containing a suite of minerals which normally form flocculated suspensions in water, yielded stable suspensions in water if the soil organic matter content was sufficiently high. With similar soils, low in organic matter, dispersant had to be added to stop partial flocculation of the test suspensions. Any gypsum present in soils has to be removed to prevent flocculation. For soils very strongly aggregated by organic matter, all the < 2 μm particles present can be released only by sonic vibration in dispersant rather than water.On four soils studied in detail, the maximum amounts of < 2 μm particles obtained by sonic vibration, vigorous shaking, and the I.S.S.S. method have been compared. On three of the four soils, the values were in close agreement.
A MINERALOGICAL CHARACTERIZATION OF SOME VERTISOLS IN THE GEZIRA AND THE KENANA CLAY PLAINS OF THE SUDAN
Authors: FADL A. E. 
Published: July 2006

SummaryExamination of the clay fraction of the Gezira and Kenana soils of the Sudan revealed montmorillonite as the dominant clay mineral, accompanied by kaolinite. The presence of illite and vermiculite is questionable. Quartz was found as an accessory mineral. Most of the kaolinite is concentrated in the ‘coarse clay’ (2–0.2 μm), whereas more than 90 per cent of the ‘fine clay’ consists of montmorillonite.
THE EFFICIENCY OF AGGREGATION INDICES IN THE COMPARISON OF SOME ENGLISH AND CANADIAN SOILS
Authors: BRYAN RORKE B. 
Published: July 2006

SummaryThe efficiency of indices of aggregation was tested by assessing the accuracy with which they reflected observed differences between selected samples from a variety of Albertan and Derbyshire soils. The most efficient indices were shown to be the percentage‐weight of water‐stable aggregates > 3 mm, > 2 mm, > 1 mm, > 0.5 mm, the coefficient of aggregation, and the mean‐weight diameter. Indices also showed highly significant variations in aggregation between fourteen soil groups, ranging from humus‐iron podzol to brown solodized‐solonetz. The Derbyshire soils showed significantly higher aggregate stability than those from Alberta. These differences may be the result of variations in clay mineral type, sodium content and climatic factors.
GEL CHROMATOGRAPHY OF HUMIC ACID
Authors: SWIFT R. S. , POSNER A. M. 
Published: July 2006

SummaryGel‐solute interactions have been reported in the application of gel chromatography to humic acid. The origins and nature of these interactions are discussed with particular reference to the behaviour of ‘Sephadex’ with compounds which are aromatic, heterocyclic, phenolic, or charged. Such structural units are known to be present in humic acid and could account for its observed interactions with ‘Sephadex’gel.The behaviour of humic acid on ‘Sephadex’and a number of other gel materials in a variety of eluants is examined. The observed deviations of these systems from that of an ideal gel chromatography system are explained in terms of charge and adsorption effects.The results indicate that a fractionation based solely on molecular weight differences can be achieved by using an alkaline buffer containing a large ammo cation as eluant together with ‘Bio‐gel’, ‘Sephadex’ or an agar based gel. Systems in which gel‐solute interactions occur should not be used for molecular weight fractionations.
WILKS'S CRITERION: A MEASURE FOR COMPARING THE VALUE OF GENERAL PURPOSE SOIL CLASSIFICATIONS
Authors: WEBSTER R. 
Published: July 2006

SummaryWilks's Criterion, the ratio of the determinants of the within‐class and total dispersion matrices, is described. It can measure the relative goodness of a general purpose soil classification, and can be used to determine how many clusters are present in a population, and hence how many classes can reasonably be recognized. Its use is illustrated with two examples. In the first, three soil maps of the same area, but at different scales, are compared. In the second, classifications of a set of profiles are shown to have recognized only three clusters.
ON THE POSSIBILITY OF CHARACTERIZING CALCIUM PHOSPHATES IN CALCAREOUS SOILS BY ISOTOPIC EXCHANGE
Authors: AMER FATHI , RAMY A. 
Published: July 2006

SummaryCharacterization of calcium phosphates depended upon the nature and the amount of phosphate used to react with reagent‐grade CaCO3. Formation of octa‐calcium phosphate (OCP) was inferred from the solubility equilibria after reacting CaCO3 with KH2PO4 solutions. Isotopic exchange measurements confirmed the presence of OCP, when the amount of P retained exceeded 44 μrnoles/g CaCO3. The determined surface‐Ca to surface‐P molar ratios were close to the theoretical Ca/P ratio of 1.33 in OCP. As P retained on CaCO3 decreased the surface Ca/P ratio markedly increased because of interference from surface Ca of the CaCO3. When CaCO3 was reacted with monocalcium phosphate (MCP), solubility equilibria indicated the formation of dicalcium phosphate dihydrate (DCPD). Isotopic exchange measurements, however, showed an average Ca/P ratio of only 0.375. This value corresponds to the composition of the metastable triple point solution (MTPS) formed on MCP dissolution rather than to the Ca/P ratio in DCPD.MCP application decreased the measured surface‐Ca (exchangeable Ca) either for soil or Ca‐resin, because of blocking of the exchange sites by the MCP reaction products and, consequently, a lower rate of isotopic exchange. Surface phosphorus of the two investigated calcareous soils proved to be proportional to the lowering in pH initiated by MCP application. Characterization of MCP reaction products in calcareous soils may thus prove infeasible, in view of the unexpected reduction in surface‐Ca and the pH dependency of surface P.
EXCHANGEABLE SODIUM AND YIELDS OF COTTON ON CERTAIN CLAY SOILS OF SUDAN
Authors: ROBINSON GLENN H. 
Published: July 2006

SummaryWithin Sudan there are extensive areas of Vertisols in the Nile River valley south of Khartoum. These soils have clay contents ranging from 40 to 60 per cent, very slow permeability, exchangeable sodium percentages up to 35 or more in the upper 60 cm, and pH values between 8.0 and 9.6. Under present management, satisfactory yields of long staple cotton are obtained under irrigation on soils having exchangeable sodium percentage (ESP) of up to 35 in the upper 60 cm. It is proposed that soil characteristics such as type of clay, cracking and exchangeable sodium in the hot, dry climate of Sudan influence soil structure and water availability and thus the yields of cotton.
THE APPLICATION OF MULTIVARIATE ANALYSIS TO SOIL STUDIES
Authors: NORRIS J. M. , LOVEDAY J. 
Published: July 2006

SummaryAllocation of a profile to a predetermined group is normally made by the surveyor in the field but alternatively a computer can be programmed to process data and make the allocation. Differences arising from these procedures may be due to differences in either the information used by computer and surveyor or the rules used to analyse the data. There is a third method, in which the surveyor, using the same data as the computer, provides a link between the other two. Comparison, in general terms, of possible results from these three methods is supported by a study on profiles from the Riverina, N.S.W. Using data for a standard set of variables and allocating into one of three groups, misallocation of 4 per cent of a test sample of forty‐six profiles resulted from both the computer method and the surveyor in the laboratory as compared with the surveyor's allocation of the same profiles on morphological properties in the field. This concurrence between the surveyor and the computer method allows the skill of the surveyor to be extended by way of the computer to technicians.
QUANTITY‐INTENSITY RELATIONSHIPS FOR LABILE SODIUM IN FIELD SOILS1
Authors: BOLTON J. 
Published: July 2006

SummaryExchange isotherms for Na with Ca+Mg in ten unfertilized soils show smaller buffer capacities for Na than K, larger Na than K activity ratios at equilibrium, and curvatures of the graphs at small Na activity ratios that could indicate larger exchange energies on about 0.5 per cent of the exchange sites.Since equilibrium Na activity ratios in the soils were similar to those in rain, the latter ratios could be most important in controlling Na activity ratios in soils and the percentage saturation of exchange complex with Na. The geochemical significance of these ratios is discussed.
THE OCCURRENCE OF ETHYLENE IN ANAEROBIC SOIL
Authors: SMITH K. A. , RESTALL S. W. F. 
Published: July 2006

SummaryThe production of ethylene and other hydrocarbon gases by soils under anaerobic conditions was measured by gas chromatography. Ethylene was the only hydrocarbon gas which occurred in physiologically significant concentrations; more than 20 ppm was found in several soils after 10 days at 20°C. These concentrations were considerably higher than those which were known to cause severe reductions in the extension of root axes of some plant species.Experiments with sterilized and unsterilized soil indicated that ethylene was produced by enzyme activity and not by chemical action. The gas was found in soil when the oxygen concentration fell below 2 per cent; total evolution was correlated with organic matter content, and was affected by drying and rewetting and by the growth of plant roots. The rate of production was increased by raising the temperature and by addition of glucose or peptone; high concentrations of nitrate depressed the rate, but sulphate and phosphate had little effect.It is concluded that ethylene may be a significant factor in causing injury to crop plants under waterlogged conditions and also in situations where anaerobic pockets occur within a mainly aerobic soil structure, provided that escape of the gas from the soil is impeded sufficiently to allow inhibitory concentrations to build up in the vicinity of plant roots.
THE OXIDATION OF IRON SULPHIDES IN SOILS IN RELATION TO THE FORMATION OF ACID SULPHATE SOILS, AND OF OCHRE DEPOSITS IN FIELD DRAINS
Authors: BLOOMFIELD C. 
Published: July 2006

SummaryAerating pyritic soils causes acidification and the forrnation of acid sulphate soils, or cat‐clay. The Oxidation of pyrite in soils is associated with the deposition in tile drains of a form of ochre quite distinct from that formed by the action of filamentous iron bacteria. Pyrite‐derived ochre results from the action of Thiobacillus ferrooxidans, which, below pH 3.5–4.0, catalyses the Oxidation of Fe2+ and pyrite. In soils less acid than c. pH 4, pyrite oxidizes relatively slowly by chemical reactions to Fe2+ and SO24−. Under these conditions iron enters the drains as Fe2+ and is there oxidized by T. ferrooicidans and deposited as hydrated ferric oxide. Once the soil becomes acid enough for T. ferrooxidans to multiply, the rate at which pyrite oxidizes increases several‐fold, and at c. pH 3 iron appears in the drainage water in the ferric form. Liming seems to decrease the rate of Oxidation.