bluuebunny/crossref_metadata_2025_split huggingface dataset:
SIGNIFICANT PARTICLE SIZE VARIATION AND WEATHERING IN ORTHIC PODZOL PROFILES1
Authors: VALENTINE K. W. G. , MILLETTE J. F. G. 
Published: July 2006

SummaryPhysical analyses of 15 Orthic Podzols of south‐eastern Quebec, Canada, showed that the extent of the breakdown of the gravel, sand, and silt and the accumulation of clay was dependent on the porosity of the parent material and the type of rocks in the gravel. There was no clay accumulation in the B horizon when the results were expressed on a percentage weight per unit volume basis. The sand was fractionated into five grades. The specific gravity of the gravel was smaller than that of any sand fraction and that of the sand increased towards the finer fractions. The specific gravity of the gravel also increased down the profile; that of the sand did not. These changes were also related to the type of parent material.A value for each horizon, calculated as follows:
image
was used as an index of weathering to show the degree of weathering intensity.
CHANNELLING OF ALLUVIAL DEPRESSION SOILS IN IRAQ AND SUDAN
Authors: WHITE L. P. , LAW R. 
Published: July 2006

SummaryDistinctive channel patterns in the floors of alluvial clay depressions in Iraq and Sudan as well as in other parts of the arid zone have been described as gilgai in the past though their morphology differs from examples of gilgai as originally described in Australia. The soils on which the channels develop vary considerably and do not always contain large proportions of expanding lattice clay. The formation of the micro‐relief may not necessarily involve heaving of the subsoil as in the Australian gilgai. It is formed rather by a process of uneven settling and compaction, the patterns of channelling being controlled by pre‐existing surface irregularities. If the formation of the micro‐relief does not involve heaving, it is probable that the channels will not reform after reclamation. The term‘tabra channels’ is suggested for the feature.
THE CONSTRUCTION OF CALIBRATION CURVES FOR DETERMINING WATER CONTENT FROM RADIATION COUNTS
Authors: HOLLAND D. A. 
Published: July 2006

SummaryThe application of regression theory to the construction of calibration curves for the estimation of water content from an observed radiation count is possible only when the relationship between count and water content is linear, a homogeneous error applies to the dependent variate, count, whatever its value, and the independent variate, water content, is determined free of error. Determination of the errors of estimation is further complicated by the necessity to fit the regression of count, as the dependent variate, on water content and then to invert the equation in order to estimate moisture content from count. It is shown that these requirements can be fulfilled by an initial transformation of the data and by repeated sub‐sampling for the determination of water content. A method is given for calculating errors of estimation.Experimentally, it was found that a transformation (logarithmic) was necessary when calibrating a beta‐gauge for leaf moisture measurement. When calibrating a neutron probe for soil‐moisture measurement no transformation was required, but it was necessary to take repeated sub‐samples for water content determinations.
A NATURAL SYSTEM OF SOIL CLASSIFICATION
Authors: MUIR J. W. 
Published: July 2006

SummaryDefinitions of natural classification are given which emphasize the importance of theory and concept in the construction of natural systems. The proposed system is based on two principles of soil formation. The first principle emphasizes the three‐dimensional nature of soil bodies. The second principle, known as the Principle of Developmental Sequences, is concerned with stages of soil development. The many developmental sequences identified by pedologists are correlated by means of a small number of constituents which are lost and gained during soil formation. These constituents, in an order of eluviation/illuviation, are used to rank the properties on which the proposed system is based. Soil horizons are defined according to the ranked properties and the classes of the system are, in turn, defined in terms of the horizons, with the result that the central statement of the system is the Principle of Developmental Sequences.
ERODED SOILS OF THE LOWER SWANSEA VALLEY
Authors: BRIDGES E. M. 
Published: July 2006

SummaryThe investigation attempts to ascertain rates and amounts of soil erosion from a small unvegetated area (120m×15m). Measurements from markers embedded in the soil indicate a removal of 10 mm per annum on 5°C slopes, 32 mm per annum on 45°C slopes, and 43 mm per annum on 62°C slopes. A sediment trap indicated that in a week when there was 56·8 mm rain, approximately 60 g/sq m was eroded. Results of the work are used in an explanation of the eroded soils of a much larger area, known as the Lower Swansea Valley.
GENESIS AND MORPHOLOGY OF SOME ALPINE PODZOL PROFILES
Authors: BOUMA J. , HOEKS J. , VAN DER PLAS L. , VAN SCHERRENBURG B. 
Published: July 2006

SummarySome representative podzol profiles from an Alpine region are described. Their genesis is mainly a function of vegetation and drainage and is analysed by morphological, chemical, and mineralogical methods. The effect of soil management on profile development as governed by recent economic advances has been discussed. When meadows with brown soils that are preserved by careful management are abandoned, heather and bilberries start growing and podzolization processes begin. Illuviation horizons are formed that have a friable consistency when formed in these meadows, but that may be hard and brittle when developed in sandy till with only heather or bilberries. Soil physical processes lead only to a fragmentation of parent rock, whereas pronounced chemical weathering occurring in these soils—decreasing in intensity with depth—produces an active clay fraction, the composition of which is discussed. Chemical weathering was most pronounced under poor vegetation. The higher content of silt in the topsoil can be partly attributed to sedimentation of wind‐blown particles. Frost action leads to sedimentation of fine soil particles on top of larger mineral fragments lying at some depth in a profile.
DISPERSION, MECHANICAL COMPOSITION, AND FRACTIONATION OF WEST INDIAN VOLCANIC YELLOW EARTH SOILS (ANDEPTS)
Authors: AHMAD N. , PRASHAD S. 
Published: July 2006

SummaryMethods of dispersion used in Japan and New Zealand for soils formed on recent volcanic ash (Andepts) which involved adjusting the pH of organic matterfree soil suspensions to 4 or 10·5 were not effective on similar soils in the Caribbean. Partial dispersion was obtained by adjusting the pH to between 2 and 3 but lower (down to pH 1) and higher (up to pH 11·1) pH values were ineffective. Substantial amounts of Al dissolved at pH 1–3 probably as a result of some disintegration of the allophanoid minerals. Zirconium nitrate solutions were very efficient in causing dispersion, a concentration of 12 me Zr being necessary for complete dispersion of 20 g samples of soil. Excess Zr did not adversely affect dispersion but resulted in depression of pH of the suspensions. The high ionic charge, small atomic radius, and low ionization potential of Zr apparently resulted in saturation of the cation exchange capacity and some isomorphous substitution of Al leading to a net positive charge of the clay and an increase in anion exchange capacity. This was considered to be responsible for dispersion.
ACCUMULATION OF ORGANIC MATTER IN A CHRONOSEQUENCE OF SOILS DEVELOPED ON WIND‐BLOWN SAND IN NEW ZEALAND
Authors: SYERS J. K. , ADAMS J. A. , WALKER T. W. 
Published: July 2006

SummaryA study was made of the amounts and distribution of C, N, S, and organic P accumulated over a period of 10 000 years of soil development on wind‐blown sand. After initial rapid rates of accumulation of C, N, and organic P during the first 1000 years, subsequent rates of gain were slower, but steady states for C, N, and S had still not been reached after 10 000 years. Sulphur declined during the first 50 years of soil development but then increased in a parallel fashion to organic C. During 10 000 years, gains of organic C, total N, total S, and organic P were 204 000, 9800, 1180, and 1170 kg/ha m profile, respectively. Gains in total N and S in the older soils are readily accounted for by returns in precipitation. Pronounced changes in soil organic matter composition during 10 000 years are reflected in the widening of the C/N ratio (8 to 20) and the C/organic P ratio (39 to 159).
COHESION OF SOIL PARTICLES AND THE INTRINSIC RESISTANCE OF SIMPLE SOIL SYSTEMS TO WIND EROSION
Authors: SMALLEY IAN J. 
Published: July 2006

SummaryIn a simple dry soil system in which erosion is taking place by virtue of the impact of saltating sand grains, the intrinsic variables affecting soil resistance can be investigated with the aid of a mathematical model. The soil erodibility depends on the cohesiveness of the soil which is indicated by the tensile strength. This is directly proportional to the packing density of the system, to the co‐ordination number of the particles, and to the inter‐particle bond strength. Tensile strength is inversely proportional to the cube of the particle diameter. In a cohesive material any decrease in the particle size produces a great increase in the tensile strength and hence the mechanical stability is improved, but because the particles are lighter they are easily eroded once they are disturbed.
VARIATIONS IN THE USEFULNESS OF RAPID SOIL MAPPING IN THE NIGERIAN SAVANNA
Authors: TOMLINSON P. R. 
Published: July 2006

SummaryThe rapid soil mapping required in developing countries can only be done by relating soils to land form and geology. A usefulness classification of mapping units is suggested. The most useful contain the least soil variation. Units with regular soil variation within them are more useful than those with random variation. In the Nigerian Savanna the most useful units are on hill remnants and homogeneous sediments, particularly coarse siliceous sandstones and fixed dunes. The least useful are on dissected areas, heterogeneous sediments, igneous and metamorphic rocks. The least fertile soils often dominate the most useful units. Rapid soil mapping should be useful in the north and the lower Niger and Benue valleys.
RE‐SORPTION OF SOIL PHOSPHATE DURING FRACTIONATION
Authors: RAJENDRAN N. , SUTTON C. D. 
Published: July 2006

SummaryStudies with 32P on six soils showed that considerable re‐sorption of phosphate occurred during the Chang and Jackson fractionation procedure. This re‐sorption resulted in an underestimate of the NH4Cl‐extractable phosphate and an overestimate of‘occluded’ phosphate, with less consistent but significant changes in the other fractions. The corrections necessary to allow for re‐sorption varied between soils.
THE SIMULATION OF GASEOUS DIFFUSION IN SOILS
Authors: RADFORD P. J. , GREENWOOD D. J. 
Published: July 2006

SummaryComputer simulation techniques are presented as a means of applying diffusion theory to two problems concerning the dynamics of oxygen and carbon dioxide distributions in soils. It is demonstrated that these techniques facilitate both problem formulation and solution, and require less mathematical skill than the equivalent analytic techniques. For problems with no analytic solution, simulation can still yield results with an accuracy equal to other numerical methods. Using simulation techniques, it was computed that stationary state conditions for carbon dioxide in a 0·7 cm layer of soil were established 24 hours after waterlogging. Similarly it was computed that for oxygen diffusing through a 0·4 cm layer of soil, equilibrium was attained within six minutes. These data were useful in that they justified the assumptions regarding equilibrium conditions which had necessarily been made in previous experiments. Simulation techniques may be of widespread use, not only for solving diffusion problems, but also for applying other fundamental laws to specific situations.
DISTRIBUTION OF CARBON DIOXIDE IN THE AQUEOUS PHASE OF AEROBIC SOILS
Authors: GREENWOOD D. J. 
Published: July 2006

SummaryTheory predicts that in the aqueous phase of aerobic soils carbon dioxide concentration/distance gradients are 1·35 times as large as those for oxygen. Because of differences in solubility, the partial pressure/distance gradients of carbon dioxide should be less than one‐twentieth of the gradients of oxygen partial pressure. Experiments were carried out to test this prediction.In some experiments oxygen partial pressures were measured directly by means of a micro‐electrode and carbon dioxide indirectly by methods involving microelectrode determinations of specific conductance in agar‐CaCO3 gel. Measurements were made in models of water‐saturated soil consisting of yeast cells embedded in agar‐CaCO3 gel, around plant roots in agar‐CaCO3 gel and within water‐saturated soil. Oxygen partial pressures fell by 5–15 per cent of an atmosphere over distances of 0·2–0·4 cm whereas carbon dioxide partial pressures increased by less than 0·3 per cent of an atmosphere over the same distance.In other experiments different thicknesses of water‐saturated soil were incubated with their upper surfaces exposed to air. The mean oxygen partial pressure fell by 7–13 per cent of an atmosphere with increasing the thickness from 0·2 to 0·4 cm whereas the carbon dioxide partial pressure never increased by more than 0·2 per cent of an atmosphere.Both sets of evidence confirm the theoretical prediction. It is concluded that the partial pressure of carbon dioxide in the aqueous phase of soils containing no oxygen‐free zones, would never, even at the surfaces of roots, be more than 1 per cent of atmosphere greater than in the gas phase.
EFFECT OF SOIL CLAY TYPE ON THE ‘AVAILABILITY’ OF ZINC IN SOME MEDITERRANEAN RENDZINA SOILS
Authors: NAVROT J. , GAL M. 
Published: July 2006

SummaryThe influence of soil clay type on the ‘availability’ of zinc was studied in six rendzina soils from Israel. The quantities of zinc extracted by EDTA—(NH4)2CO3, were higher in the soils with a lower total of zinc content. Values of extracted zinc calculated on the basis of soil minus CaCO3 were higher in soils with attapulgite than in soils with montmorillonite as the predominant mineral. Thus, it appears that zinc is more strongly bound to montmorillonite. This was confirmed by a greenhouse experiment in which total zinc uptake after zinc fertilization was higher from rendzinas containing attapulgite than from montmorillonitic rendzinas.
OPALINE SILICA OF RECENT VOLCANIC ASH SOILS IN JAPAN
Authors: SHOJI SADAO , MASUI JUN‐ICHI 
Published: July 2006

SummarySoil samples were investigated from three different climatic regions of Japan. The soil profiles were well drained and consisted of a number of buried soils. Organic matter and free iron oxides were removed from the samples which were then fractionated. Laminar opaline silica particles occurring in the 0.2 to 5 μm fractions were examined electron‐optically following ultrasonic and cold 5 per cent sodium carbonate treatment.Four types of opaline silica particles were distinguished: circular, elliptical, rectangular, and rhombic. The opaline silica particles are extremely thin. They show fine‐grained uneven surfaces and weathered and alkali‐treated opaline silica particles appear to be very porous suggesting that the particles are actually composed of extremely fine silica spheres. Opaline silica panicles occur only in the 0.2 to 5 μm fractions and are most abundant in the 0.4 to 2 μm fractions. Of the four types the circular and elliptical types predominate. The elliptical type is the most common in the fine fraction and the circular type in the coarse fraction.Compared with B‐ or C‐horizons, the A‐horizon of a profile tends to be relatively rich in opaline silica. Opaline silica particles are abundant in recent volcanic ash soils, particularly in Hokkaido soils < 500 years old. Soils of this area more than 7000 years old contain opaline silica particles whereas they are rare in Kanto soils > 6000 years old and in Kyushu soils > 4000 years old.Hokkaido has much lower mean annual temperatures and rainfall than Kanto or Kyushu. This may have caused slower weathering of opaline silica in the Hokkaido soils.Conditions for formation of opaline silica may be less favourable in subsoils because supersaturation of silica and concentration of bases is less likely to occur in subsoils than in surface soils.
A PHOSPHATE SORPTION INDEX FOR SOILS
Authors: BACHE B. W. , WILLIAMS E. G. 
Published: July 2006

SummaryPhosphate sorption isotherms covering a wide concentration range (10−6 to 5 × 10−3m phosphate) were determined for 42 soil samples at 20 °C by a standardized technique. The slope of a plot of the sorption, x, against the logarithm of the equilibrium solution phosphate concentration, log c, measured at c= 10−4M, proved a suitable reference index to characterize the phosphate sorbing properties of the soils. Several single‐point methods were tested by statistical correlation against this reference index. Of these, the sorption, x, from one addition of 150 mg P/100 g soil gave r= 0.951, but r= 0.974 when the equilibrium concentration was also taken into account in the quotient x/log c. This quotient is therefore suggested as a simple yet adequate way of indicating a fundamental soil property, its phosphate sorption isotherm.
LEACHING OF EUPHRATES SALINE SOIL IN LYSIMETERS
Authors: AL‐NAKSHABANDI G. A. , ALZUBAIDI A. , ISMAIL H. N. , AL‐RAYHANI F. , AL‐HADITHY E. 
Published: July 2006

SummaryA saline soil from Euphrates alluvium at Abu‐Ghraib was leached in two lysimeters with river water and the changes in composition of the soils and of the leachates were measured as well as the hydraulic conductivity. The results show that the presence of gypsum prevents the soils becoming sodic as leaching with irrigation water of favourable composition proceeds.
THE APPLICATION OF MULTIVARIATE ANALYSIS TO SOIL STUDIES. III. SOIL VARIATION
Authors: NORRIS J. M. 
Published: July 2006

SummaryThree stages in the study of soil variation are recognized: the identification of major soil types and gradients, the establishment of the location of types on the ground and on a map, and the understanding of the causes of soil variation. Evaluation of the causes of variation may be hindered if the stages are not kept separate and a strategy is suggested to achieve this separation. Principal components analysis and numerical classification are used first to produce a rigorous description of soil variation which is presented in map form. This description is a basis for the generation of hypotheses about the causes of soil variation. This strategy is used to examine soil variation in some beech woods and farmland of the mid‐Cotswold Hills, Gloucester shire, and a hypothesis is suggested that variation in soil moisture is most important in this area.
NUMERICAL ANALYSIS OF SOILS: A COMPARISON OF THREE SOIL PROFILE MODELS WITH FIELD CLASSIFICATION
Authors: MOORE A. W. , RUSSELL J. S. , WARD W. T. 
Published: July 2006

SummaryFourteen field and laboratory attributes of 49 south‐east Queens land soils were examined by numerical analysis. Three different models were used for description: the soils were viewed (1) as arrays of layer‐attributes, (2) as sets of depth functions (orthogonal polynomials) each of which describes an attribute, and (3) as sequences of layers of soil material. Dendrograms derived from Euclidean distance similarity matrices were constructed for the 49 profiles. Very similar dendrograms were obtained using (a) layer‐by‐layer comparisons (with layers weighted by an exponential depth function) and (6) orthogonal polynomials, with equal weight given to profile mean (size parameter) and five coefficients (shape parameters). The dendrogram derived from sequential analysis differed markedly from the others and seemed less meaningful; the divisive approach that had to be adopted to delineate groups of profile‐layers may have resulted in a sub‐optimal classification.An independent field study which related the soils to geomorphic units and to differences in parent material provided a further, separate classification. The groups derived by numerical analysis, using models I and 2, agreed well with the field classes even though the strategies used were different and independent. It is concluded that existing techniques of numerical analysis can provide immediate useful support in field surveys.
TRENDS OF SOIL CLASSIFICATION IN TANZANIA I. THE EXPERIMENTAL USE OF THE 7TH APPROXIMATION
Authors: KESSEBA A. , PITBLADO J. R. , URIYO A. P. 
Published: July 2006

SummaryA review is made of the trends in soil classification in Tanzania, indicating the need for an alternative to the traditional catena concept. An attempt to use the 7th Approximation is reported, in view of the demand for high category soil classification, using forty‐three typical soil profiles and discussing the particular problems related to placing three intimately studied profiles into the orders Alfisol, Ultisol, and Oxisol. An unrevised version of the 7th Approximation is not recommended for use in Tanzania. However, by using the central concepts of the system and further defining the soil classes at all levels, the use of the 7th Approximation could greatly assist in the assessment of the nation's soil resources and the ultimate development of agriculture in this country.
HYSTERESIS OF FLUX‐GRADIENT RELATIONS FOR SATURATED FLOW OF WATER THROUGH CLAY MATERIALS
Authors: NOVÁK V. 
Published: July 2006

SummaryThe relation between flow velocity (v) and hydraulic gradient (7) was studied for two porous materials. The volume of the sample was allowed to change during experiment. For the kaolinite, the relation between v and I is non‐linear, the hydraulic conductivity k becomes dependent on time and varies for both increasing and decreasing 7. After some time, k tends to some constant value. For bentonite, k remains constant as 7 increases. However, when I starts to decrease, k decreases accordingly. Hysteresis in the relationship between v and 7 remains unchanged with time. The observed deviations from Darcy's law may be due to deformation of the voids.
VERTICAL DISTRIBUTION OF EXTRACTABLE IRON AND ALUMINIUM IN SOIL PROFILES FROM A BROWN EARTH‐PEATY PODZOL ASSOCIATION
Authors: BALL D. F. , BEAUMONT P. 
Published: July 2006

SummaryFe and Al extractable by 3 per cent oxalic acid and by 0.1M potassium pyrophosphate at pH 10 have been determined in horizon samples of two soil profiles of each of three subgroups (Brown Earth, Brown Podzolic Soil, and Peaty Podzol) developed in North Wales on parent materials derived from Silurian shales. The vertical distribution of Fe and Al together with the relationship between pyrophosphate‐extractable (‘fresh’ hydrous oxides) and oxalic‐extract‐able Fe or Al (‘fresh’+‘aged’ hydrous oxides) can assist classification and interpretation of the course of podzolization in these soils. If podzolization is defined as sesquioxide transport, then its degree of development in the soils studied differs according to whether Al or Fe are used as the index element. The evidence supports continued recognition of soils of Brown Podzolic type as an intergrade subgroup.