bluuebunny/crossref_metadata_2025_split huggingface dataset:
COLLECTION AND EVALUATION OF LARGE SOIL MONOLITHS FOR SOIL AND CROP STUDIES
Authors: BELFORD R. K. 
Published: July 2006

SummaryA technique is described which allows collection and transportation of undisturbed soil monoliths in glass fibre casings 80 cm in diameter and 135 cm deep. The technique has been used to obtain 150 monoliths from a range of soil types in England and Wales, including soils with compact or chalky horizons.Measurements from lysimeters containing a non‐swelling sandy loam and a swelling clay showed that the hydraulic properties of both soils were not affected by encasement of the profiles, provided that supplementary drainage outlets at the depth of field mole drains were provided in the lysimeters containing the clay soil. Aeration of the clay monoliths was comparable with that of the same soil in the field.When winter wheat plants growing on the lysimeters were surrounded by a similar guard crop, yields were equivalent to those obtained in the field. Edge effects were not significant; plants grown adjacent to the lysimeter wall yielded the same weight of grain per unit soil area as those in the central area of the monolith.
ROTHAMSTED STUDIES OF SOIL STRUCTURE VII.
Authors: SKINNER F. A. 
Published: July 2006

SummaryNatural aggregates of topsoil samples of six British soils (Hanslope, Ragdale, Evesham, Denchworth, Flint and Salop) were incubated with added nutrients and changes in their stability to wet sieving determined. Under anaerobic incubation the type of nutrient added had little effect on stability. Aerobic incubation with glucose gave a larger proportion of stable aggregates than with water. With peptone stability usually decreased, and occasionally increased, which may indicate differences in the binding mechanisms of the soil particles. Both sterile and unsterile aggregates incubated with water became more stable than controls; the rapidity of this change suggested a physical, rather than microbiological cause. Very stable grassland aggregates changed little on aerobic incubation with water, but became more stable with solutions of glucose or peptone. Artificial aggregates made from the same soil developed considerable stability to water on aerobic incubation, but remained almost totally unstable when incubated anaerobically.
THE INFLUENCE OF MAGNESIUM IN SALINE AND SODIC SOILS: A SPECIFIC EFFECT OR A PROBLEM OF CATION EXCHANGE?
Authors: RAHMAN W. A. , ROWELL D. L. 
Published: July 2006

SummaryNa‐Mg and Na‐Ca exchange isotherms were determined at electrolyte concentrations of 500, 50, 5 and 1 meq per litre for illite, vermiculite and montmorillonite and for three soils containing illite and montmorillonite. This enabled comparisons to be made of clay swelling, dispersion and soil hydraulic conductivity changes between the Na‐Mg and Na‐Ca systems at known SAR, ESP and electrolyte concentration.Na‐Mg montmoriUonite and a montmorillonitic soil behaved identically to the Na‐Ca systems at the same ESP and electrolyte concentration: there was no specific effect. At the same SAR, the higher ESP in the Na‐Mg system caused greater changes than in the Na‐Ca systems. The Na‐Mg vermiculite, illite, illitic soil and mixed illite‐montmorillonitic soil showed greater changes than the Na‐Ca systems at the same ESP, and there was a specific effect. At the same SAR, the higher ESP in all the Na‐Mg systems apart from vermiculite increased the differences, but for vermiculite with a lower ESP, the differences were reduced. The lack of a specific effect for montmorillonite is probably related to the demixing of cations with the divalent ions concentrated on the non‐swelling (internal) surfaces of the crystals.
THE ALTERATION OF PLAGIOCLASES AND AUGITES UNDER DIFFERING PEDO‐ENVIRONMENTAL CONDITIONS
Authors: ESWARAN H. 
Published: July 2006

SummaryThe alteration of plagioclases and augites in lithorelicts were studied in thin sections of five selected profiles which differed in their mineralo‐chemical composition and stage of soil formation. The scanning electron microscope was employed to monitor the products of alteration of the pseudomorphs.In the base‐rich environment of the Eutropept and Tropudalf, both primary minerals alter to montmorillonite with small amounts of amorphous alumino‐silicates present on the plagioclases, and amorphous materials of undetermined composition on the augite. Local desiliciflcation of the feldspars results in gibbsite.In more acid environments, as in the Dystropept, the plagioclases alter to metahalloysite and some amorphous aluminosilicates, and the augite to amorphous iron hydrous‐oxide and goethite. In a freely drained environment as in the Tropudult, the alteration of plagioclases leads to kaolinite and locally to gibbsite; all the augite is converted to goethite. No rock relicts are present in the Oxisols.The differential alteration is a function of the pedo‐environment which is determined by the rate and amount of water percolating down the profile.
THE ERODIBILITY OF TWO SOILS FROM KENYA
Authors: BARBER R. G. , MOORE T. R. , THOMAS D. B. 
Published: July 2006

SummaryA portable rainfall simulator was used to measure the runoff rates and soil losses from a freshly ploughed luvisol at Katumani, and a nitosol at Kabete, on a 6° slope at varying rainfall intensities. The soil losses from storms of 50 and 100 mm/h intensities, in which a total of SO mm rain was applied to plots in the wet moisture state, varied from 0.8 to 1.4 metric tons/ha at Kabete and 8.5 to 13.9 metric tons/ha at Katumani. The percentage runoff from these storms was 15 to 17 per cent at Kabete and 67 to 71 per cent at Katumani. The much greater runoff rates from the Katumani soils were shown to be due to surface capping caused by degradation of the surface structure. It has been proposed that soil credibility K factors of 0.4 and 0.04 could be used for the Katumani and Kabete soils respectively in the Universal Soil Loss Equation
RAPID REPRESENTATIVE SAMPLING OF SOIL GASES AND THEIR DETERMINATION BY MASS SPECTROMETRY
Authors: ROBERTSON G. W. , BRACEWELL J. M. 
Published: July 2006

SummaryThe use of a portable field probe for sampling soil gas gives the degree of replication necessary to allow for the local variability of soil gas composition over short distances, and mass spectrometry provides a quick and efficient method of analysis for gases at concentrations above 0.1% by volume. These methods can conveniently be combined and their use is illustrated by the determination of N2, O2, Ar, CO2 and CH4 in two soils having impeded gaseous exchange with the atmosphere.
THE INFLUENCE OF MAGNESIUM AND OF EASILY WEATHERED MINERALS ON HYDRAULIC CONDUCTIVITY CHANGES IN A SODIC SOIL
Authors: ROWELL D. L. , SHAINBERG I. 
Published: July 2006

SummaryExchangeable Mg appears to have no specific effect on soil hydraulic conductivity of A and C horizons of a sodic sandy loam soil (montmorillonite and kaolinite clay minerals) leached with solutions which cause clay swelling to be the dominant mechanism reducing conductivity (SAR < 20, electrolyte concentration 10 meq per litre). There is some evidence of a specific effect when these soils are subsequently leached with water which causes clay dispersion to become important. Fresh loess in the A horizon dissolves in percolating rainwater, causing difficulties in the replication of experiments. It seems to give a small degree of ‘self protection’ to soil structure, a property likely to be operating in other soils affected by recent loess deposits.
CHANGES IN MOLECULAR WEIGHT DISTRIBUTION OF SOIL ORGANIC MATTER DURING SOIL DEVELOPMENT
Authors: GOH K. M. , WILLIAMS MARY R. 
Published: July 2006

SummaryTen different topsoils representing members of three soil chronosequences were pre‐treated with 0.1 M HC1 and extracted with neutral 0.1 M Na4P2O7 followed by 0.5 M NaOH. Extracts were purified and fractionated into five different nominal molecular weight fractions using gel filtration. With increasing soil development, the proportion of large molecules (>200 000) in the organic matter decreased with an increase in the proportion of intermediate size molecules (200 000 – 10 000). This effect was more evident in the mild Na4P2O7 extracts than in the subsequent NaOH extracts, and in soils of the Manawatu chronosequence than in those of the other two chronosequences and are attributed to changes in the nature and humification of soil organic matter during soil development.
AVAILABILITY OF POTASSIUM TO RYEGRASS FROM SCOTTISH SOILS II. UPTAKE OF INITIALLY NON‐EXCHANGEABLE POTASSIUM
Authors: SINCLAIR A. H. 
Published: July 2006

SummaryThe stable desorption parts of soil Quantity/Intensity isotherms were used to determine the contributions of initially exchangeable and non‐exchangeable potassium to plant uptake from ten soils. The activity ratio, ARK= aK/√aCa, Mg at which K was first taken up from non‐exchangeable sources varied from 3 × 10−3 to 8 × 10−3 M1/2 depending on the soil. Uptake rates of two categories of initially non‐exchangeable K were linearly related to √times;. The first category appeared to be close to equilibrium with the initially exchangeable K, and gave effective diffusion coefficients of 10−7 cm2 s−1 for four soils. The second category gave diffusion coefficients from 10−20 to 10−22 cm2 s−1, probably came from internal surfaces of micaceous clays, and began to be released at activity ratios below 3 × 10−4 to 6 × 10−4 M1/2 depending on soil type. The soils fell into three groups, broadly consistent with soil series, on their ability to release the second category of potassium.
EFFECT OF ADSORPTION OF PHENOXYACETIC ACID HERBICIDES ON THE SURFACE CHARGE OF GOETHITE
Authors: KAVANAGH B. V. , POSNER A. M. , QUIRK J. P. 
Published: July 2006

SummarySurface charge titration measurements, performed on goethite in the presence of absorbed herbicide ions, indicate that the result of adsorption is to cause an increase in the positive charge of the mineral surface. The titration results, used in conjunction with adsorption measurements to calculate the exchange coefficients for the adsorption reactions, show that there is a significant selectivity in adsorption of the herbicides over the indifferent counterion nitrate. This is believed to be due to the existence of favourable van der Waals interactions between the adsorbed herbicide ions.
THE INFLUENCE OF pH, IONIC STRENGTH AND REACTANT CONCENTRATIONS ON COPPER COMPLEXING BY HUMIFIED ORGANIC MATTER
Authors: SANDERS J. R. , BLOOMFIELD C. 
Published: July 2006

SummaryThe effects of varying the pH and ionic strength, and the concentrations of organic matter, copper, calcium and phosphate upon the complexing of copper by extracts of humified organic matter from laboratory preparations, soil and peat were measured. The extent of complexing increased as pH increased and ionic strength decreased, and with increasing organic matter: copper ratios in a way consistent with the complexant being heterogeneous. Calcium competed with copper for organic matter, but the effect of phosphate was negligible. The extent of complexing at pH 7 by equal weights of colloidal and dialysable material from the same extract were usually similar. Weight for weight of organic carbon, alkali‐extracted humified organic matter complexed copper much more extensively than the corresponding water‐soluble material.
AMINO ACIDS IN BURIED PALEOSOLS
Authors: LIMMER A. W. , WILSON A. T. 
Published: July 2006

SummaryA sequence of paleosols date at 80, 7 000, 20 000 and 41 000 years developed on similar parent material in the North Island of New Zealand have been used to study the fate of amino acids with time.Some amino acids were released by hydrolysis with 6M HC1 for 24 h at 110 °C while others were only released after the mineral matrix had been destroyed by HF.The mineral bound amino acids were hydrolysed from each paleosol and their composition analysed. The simplicity of the composition of the older paleosols confirms that the amino acids are fossil. This technique could be used for determining whether paleosol samples submitted for carbon dating are contaminated by more recent material. The differential disappearance of amino acids from a paleosol could be used as a dating system and if this was done quantitatively it may be possible to date paleosols beyond the range of carbon dating.
EFFECTS OF TILLAGE AND STUBBLE MANAGEMENT ON THE STRUCTURE OF A SWELLING SOIL
Authors: HEWITT J. S. , DEXTER A. R. 
Published: July 2006

SummaryA method, described previously, is used to quantify the macrostructure within the surface layers of swelling soil. Dissimilarity coefficients are defined and used to quantify soil structural differences resulting from different treatments. Structural differences over small increments in depth are resolved. Effects resulting from different tillage and stubble management practices are distinguished. Differences resulting from burning or retention of stubble had at least as great an effect as tillage practice on the void and aggregate size distributions. However, tillage increased the macro‐porosity.The structures of two mechanically‐prepared seed beds are compared with the structure of soil on tillage and stubble management trials where seed beds had not been prepared.It is shown in Appendix I that the structures measured on the two sections through each impregnated soil sample are essentially independent.A method is presented in Appendix II for converting the structural transition probabilities at unit spacing (e.g. 0.5 mm) to transition probabilities at double spacing (e.g. 1.0 mm). This enables results from different sources, which have been measured on the two scales, to be compared.
A MODEL OF THE EXTENT OF ANAEROBIC ZONES IN AGGREGATED SOILS, AND ITS POTENTIAL APPLICATION TO ESTIMATES OF DENITRIFICATION1
Authors: SMITH K. A. 
Published: July 2006

SummaryA model has been developed of the variation in the extent of anaerobiosis in aggregated soils with variations in gaseous diffusion coefficients, respiration rate and aggregate size. It extends previously published models of radial diffusion into individual aggregates to a log‐normally distributed population of aggregate sizes such as is known to occur in the field. It considers in particular the situation in which relatively better drainage and aeration occurs in the inter‐aggregate pores than within the aggregates. The model indicates that in most circumstances the effects of variations in the gaseous diffusion coefficients outweigh comparable variations in aggregate size. It is demonstrated how the model may be applied to calculation of rates of denitrification, and two alternative approaches are proposed: one based on the quantities of nitrogen and nitrous oxide diffusing out of partially anaerobic aggregates, the other on the disappearance of nitrate following diffusion into anaerobic zones.
AN INVESTIGATION OF WEATHERING IN SOME ARCTIC‐ALPINE SOILS ON THE NORTHEAST FLANK OF OKSSKOLTEN, NORTH NORWAY1
Authors: ELLIS S. 
Published: July 2006

SummaryMorphological, particle size and mineralogical analyses of three soils indicate that the degree of weathering during pedogenesis has been of a low order. Textural characteristics and mineral content variations arc attributed largely to inheritance from the till parent material, rather than to pedological processes. These observations suggest that frost action as a soil weathering process in this particular environment is minimal. Hydration and dissolution by chelation are discussed as possible alternative mechanisms, but their operation is probably impaired by restricted water availability resulting from the extensive duration of seasonally frozen ground conditions.
EVALUATION OF POTENTIAL SUBSTRATES TO MONITOR RESPIRATORY NITRATE REDUCTASE ACTIVITY IN SOILS
Authors: RODGERS G. A. 
Published: July 2006

SummaryDifferent inorganic ions were tested for their ability to replace nitrate as the terminal oxidant for bacterial respiration in anaerobic soils. Chlorate, bromate. selenate. tellurite and ferric ions were all unsuitable substitutes, lodate reduction in soils was similar to nitrate reduction because it required anaerobic conditions, was increased by glucose amendment and decreased by phenylmercuric acetate. Amendment of soils with iodate and measurement of iodide production can be used to measure nitrate reductase activity in a soil and so give a qualitative indication, and possibly a quantitative estimate, of the denitrification capacity of soils.
THE EFFECT OF SOIL COMPOSITION AND ENVIRONMENTAL FACTORS ON THE SHRINKAGE OF SOME CLAYEY BRITISH SOILS
Authors: REEVE M. J. , HALL D. G. M. , BULLOCK P. 
Published: July 2006

SummaryThe shrinkage potential of natural clods from a variety of clayey soils was measured and related to their physical, chemical and mineralogical properties. It is shown that the most important factors affecting shrinkage are initial bulk density, clay content, organic carbon content and cation exchange capacity of the peroxidised clay, and mica‐smectite content on a whole soil basis. Multiple regression equations involving the initial bulk density, clay content, organic carbon and cation exchange capacity accounted for 87 and 82 per cent of the variation in total shrinkage of topsoils and subsoils respectively.Because of restrictions on shrinkage imposed by factors such as climate, crops, ground‐water and moisture release characteristics of soils, soils with a high shrinkage potential may not behave very differently to soils with a much lower potential. On these grounds it is concluded that the shrinkage criteria used in US Taxonomy are not applicable in Britain.
COMPARISON OF THE CERAMIC PLATE AND THE PRESSURE MEMBRANE TO DETERMINE THE 15 BAR WATER CONTENT OF SOILS
Authors: WATERS PATRICIA 
Published: July 2006

SummaryVolumetric water contents of 17 mineral and 3 peat soils were measured at 15 bar pressure using the ceramic plate and the pressure membrane apparatus. There was no overall significant difference between the results from the two types of apparatus and both ranked the soils in essentially the same order. Although soils of high clay or organic matter content retained up to 13.5% more water on the ceramic plate than on the pressure membrane, available water capacity (AWC) of a clay soil would be decreased by only 1–2%, and that of a peat soil by 3–4%. Due to its greater reliability, the ceramic plate is an acceptable alternative to the pressure membrane when used to determine the 15 bar water content.
THE CONTENTS AND SORPTION OF CADMIUM IN SOME AGRICULTURAL SOILS OF ENGLAND AND WALES
Authors: JARVIS S. C. , JONES L. H. P. 
Published: July 2006

SummaryCadmium sorption was measured in 10 agricultural soils with pH ranging from 4.5 to 7.9, and total Cd content from 0.27 to 1.04 μg g−1 dry soil. With initial Cd concentrations of 0.5 to 100.0 μM, sorption from 0.002 M CaCl2 was described by the Freundlich adsorption equation but the gradients of the isotherms increased when the initial concentrations were below 0.5 μm. This indicates that there are specific sites of differing sorption energy; differences between soils in the gradients of the isotherms at low initial concentration could largely be accounted for by their contents of ‘free’ Fe2O3. When initial concentrations were below 0.5 μm there was a linear relationship between the quantity of Cd sorbed and the final concentration in solution. This relationship held with all soils except that of lowest pH from which there was a net loss of Cd to the solutions. Desorption was measured from three soils with contrasting pH. With the soil of lowest pH, over 80 per cent of sorbed Cd was desorbed to 0.002 m CaCl2 and up to 30 per cent to 100 or 500 μm solutions of heavy metal chlorides. In contrast, only very small proportions (<1.25 per cent) were desorbed from the other soils with pH 6.7 and 7.8.The results indicate that Cd is strongly sorbed by soils of pH of above 6.0 when added in amounts comparable to additions in sewage sludges or phosphatic fertilizers, and illustrate the importance of liming as a means of reducing the mobility of this metal in soils.
THE MONOSACCHARIDE COMPOSITION OF POLYSACCHARIDES IN ANDO SOILS
Authors: MURAYAMA SHIGETOSHI 
Published: July 2006

SummaryThe monosaccharide composition of Ando soils, which originate from volcanic ash and have high organic matter content (8–21% carbon), was quite different from that of non‐volcanic ash soils (1.2–1.9% carbon), being richer in mannose, fucose and ribose, whereas there was less glucose in cellulose‐like form, arabinose, xylose and rhamnose. The Ando soils were also characterized by a lower percentage of organic carbon in the form of saccharide (4.4–7.4%) in comparison with non‐volcanic ash soils (10.5%), though the former soils contain a greater amount of saccharides.The monosaccharide composition of Ando soils was unrelated to the vegetation, land usage, or climatic conditions, and is presumed to be a soil characteristic resulting from the preferential accumulation of microbial polysaccharides.
OPTIMAL INTERPOLATION AND ISARITHMIC MAPPING OF SOIL PROPERTIES III CHANGING DRIFT AND UNIVERSAL KRIGING
Authors: WEBSTER R. , BURGESS T. M. 
Published: July 2006

SummaryUniversal kriging is a form of interpolation that takes account of local trends in data when minimizing the error associated with estimation. The presence of such trends, or drifts as they are known, is identified qualitatively, and their form found quantitatively by structural analysis, which simultaneously estimates semi‐variances of the differences between the drift and actual data. The resulting semi‐variograms are then used for the interpolation.The method was applied to measurements of electrical resistivity made in the soil at 1 m intervals at Bekesbourne, Kent. Analysis showed that the data could be adequately represented as a series of linear drifts over distances of 4 m to 8 m and with negligible nugget variance. Semi‐variances of residuals from the drift were computed, and used to krige missing values and so complete an isarithmic map of the site.The method is by no means universally applicable in soil survey, mainly because of the large nugget variances usually encountered. These effectively prevent any distinction between constant and changing drift. They arise in part because measurements are made on small widely separated volumes of soil. Universal kriging is likely to be profitable only where measurements are made on contiguous volumes of soil or after substantial bulking.
THE POTASSIUM STATUS OF MALAWI SOILS
Authors: MAIDA J. H. A. 
Published: July 2006

SummaryTwenty surface soils from four main Soil Groups in Malawi and their sub‐soils were divided into three groups based on cation exchange capacity (group I, CEC < 50; group II, 50–100; and group III > 100μeq g–1). In each soil group the maximum amounts of K removed by successive extraction with 0.005 M CaCl2 solution were well related to the potassium potential pK–0.5p(Ca + Mg), exchangeable K, ‘step K’, and the quotient ‘step K’/CR.K, where CR.K is ‘constant‐rate’potassium. In Group III soils only, ‘step K’/CR.K values were significantly correlated with pH, clay, and CEC, and this suggested that the soils were relatively rich in K+ specific binding sites.In 27 soils from an NPK factorial experiment on tea, the rate of depletion of extractable K reserve increased with ammonium sulphate treatment, whereas K fertilizers tended to off‐set significantly (P= 0.001) the depletion of K reserve. The values for the change in free energy ΔG =RT In aK/ (a(Ca+Mg)) ½, ranged from –12 to –16 kJ mol–1, and field observations showed that tea plants growing on soils having ΔG values less than –15 kJ mol–1 responded to K fertilizers. The investigation has indicated that heavily cropped soils are likely to show crop responses if the intensive cropping system does not include supplementation of K.