bluuebunny/crossref_metadata_2025_split huggingface dataset:
Concentration of phosphorus and sulphur at soil ped surfaces
Authors: QURESHI R. H. , JENKINS D. A. 
Published: July 2006

SUMMARYPedogenesis involves reorganization of a soil's components and thus relocation of nutrients within the microfabric. This has particular relevance to P which, being relatively immobile, is needed within the immediate root environment. The spatial distribution of P and S in four profiles (haplaquepts, eutrochrept, ochraqalf) with well developed prismatic structure has been investigated at the 1 mm scale, by physical sampling of successive ped surface zones, and at the 1 μm scale by electron probe microanalysis. Results reveal distinct though variable patterns of concentration of P and S at ped surfaces (0.1–3 mm depth) in certain profile horizons; correlation with extractable Ca, Al & Fe proved obscure by macroanalysis, but microanalysis showed specific associations variously interpreted as detrital grains (apatite, monazite, etc.), organic debris or adsorbed phosphate. Such heterogeneity in distribution is mostly consistent with the microfabric seen in thin‐section, although some remains cryptic. This is important since plant roots selectively sample the differentiated ped surfaces and not the bulk homogenized soil analysed in the routine assessment of nutrient availability.
Design of a database for Scottish soils
Authors: BROWN K. W. M. , GAULD J. H. , SMITH B. F. L. , BAIN D. C. , BURRIDGE J. C. , INKSON R. H. E. 
Published: July 2006

SUMMARYThe factors involved in the design and structure of a database for Scottish soils are described. Codes were extensively used for data entry, which though restrictive, minimized entry errors, reduced file space and make subsequent statistical analysis easier. The database contains records of soil profile descriptions, systematic chemical and physical analyses for all profiles sampled, as well as mineralogical and spectrochemical trace element analyses for a limited number of selected soils. Query and report writer facilities are described and were used for the production of reports, tables and maps.
Causes of crop patterns in eastern England
Authors: EVANS R. , CATT J. A. 
Published: July 2006

SUMMARYGrowth and yield of cereals were measured at four sites in eastern England where crop patterns have been repeatedly observed on aerial photographs. The patterns were related to archaeological features, infilled river channels, interbedding of lithologically diverse pre‐Quaternary sediments, periglacial disturbance of shallow loamy soil over Chalk, and the occurrence of minor valleys incised into chalky till. They resulted from differential germination and growth rates, which were in turn related to differences in (a) available water in the soil, (b) the inhibition of root extension by hard chalk, (c) soil temperature and (d) the workability of soils during drilling of spring‐sown crops. Yield losses resulting from the patterns ranged from 15 to 51 %.
Predicting the rate of dissolution of lime in soil
Authors: NYE P. H. , AMELOKO A. Y. 
Published: July 2006

SUMMARYA disc of CaCO3 was brought into contact with a column of moist acid soil, incubated for 6 days, the soil cut into thin sections, and the pH measured. The pH profile suggested that the rate of dissolution was controlled by the rate of acid‐base diffusion in the soil near the interface of the soil and the CaCO3 disc.A mechanistic model was developed, containing no arbitrary assumptions or fitting parameters, to predict the rate of neutralization of acid soil by CaCO3 particles of different size grades and at different application rates. The course of neutralization of soil at pH 3.0 and 4.9 with fine, medium and coarse grades of CaCO3 was measured and compared with the model predictions. The agreement was satisfactory within the limits imposed by experimental difficulties.
Distribution of 14C between particle size fractions and carbohydrates separated from a peat incubated with 14C‐glycine
Authors: WILLIAMS B. L. , CHESHIRE M. V. , SPARLING G. P. 
Published: July 2006

SUMMARYSamples of fresh Sphagnum peat from a raised bog were amended with 14C‐labelled glycine. The distribution of 14C between particle size fractions obtained by wet sieving (sieve sizes 1, 0.5, 0.25, 0.15 and 0.05mm) was determined immediately on control (unincubated) samples and after 1, 6 and 12 months incubation at 10°C. The recovery of glycine in solution was almost 100%. During the incubation with 14C‐glycine, 14CO2 was released within the first 20 weeks, equivalent to 51.5% of the added 14C, but thereafter very little 14CO2 was evolved. After 26 weeks a substantial amount of 14C was distributed amongst all the fractions, but the greatest incorporation (4.47%) occurred in the finest fraction (0.005–0.05 mm). Labelling of the other particle size fractions was <2.3% of added 14C. Carbohydrate accounted for 23% of 14C in the finest fraction and the sugars, rhamnose, arabinose, xylose, mannose, galactose and glucose all became labelled. Rhamnose showed the greatest, and arabinose, galactose and xylose the least, increase in specific activity; glucose and mannose had intermediate values. It was concluded that the finest fraction in peat contains a significant proportion of the microbially‐synthesized material.
The importance of exchangeable cations and resin‐sink characteristics in the release of soil phosphorus
Authors: CURTIN D. , SYERS J. K. , SMILLIE G. W. 
Published: July 2006

SUMMARYThe significance of exchangeable cations in the release of phosphorus by sequential extraction with water was evaluated in 11 acid (pH 5.0–6.3) New Zealand soils contrasting in P status and P retention. The release of P from Na‐saturated soil exceeded that from the original Ca‐dominated soils by up to four‐fold. Possible explanations for the larger P release in the Na system include: (i) desorption of P induced by increased surface negative potential associated with the exchange of Na for Ca/Mg, and/or (ii) accelerated dissolution of Ca phosphate compounds or complexes resulting from the creation of a sink for Ca.The potential of a series of anion‐ and cation‐exchange resin systems (AER and CER, respectively) as sinks for labile soil P was also examined. For all soils studied, P extracted by AER‐HCO3 <AER‐OH/CER‐Na< AER‐OH/CER‐H. The success of the AER‐OH/ CER‐H system in extracting P is attributed to its ability to remove exchangeable Ca and Mg, and to reduce the ionic strength of the equilibrating solution. A high correlation (r= 0.99**) was obtained between P extracted by AER‐HCO3 and that removed by sequential extraction with water. Also, the amounts of P extracted by AER‐OH/CER‐H and NaCl/ H2O were closely correlated (r= 0.95**), suggesting similar release mechanisms. The results obtained indicate that charge‐balancing cations, particularly Ca which is the predominant exchangeable cation in the majority of soils, exerts a more significant control on soil P equilibria in acid soils than is commonly recognized.
Total and extractable trace element contents of soils in England and Wales
Authors: ARCHER F. C. , HODGSON I. H. 
Published: July 2006

SUMMARYSoil samples taken by soil auger to a depth of 150 mm from randomly selected agricultural fields throughout England and Wales were analysed for total As, B, Cd, Co, Cr, Cu, Hg, Ni, Pb, Se and Zn, acetic acid‐extractable Cd, Co, Cu, Ni, Pb and Zn, EDTA‐extractable Cd, Co, Cu, Ni, Pb, Se and Zn, ammonium oxalate extractable Ni and Mo and hot water‐extractable B. Median, log‐derived mean and range data are given for each element. Median values are given also by parent material and textural grouping.
Effect of water content on the fabric of a soil material: an experimental approach
Authors: BRUAND A. , PROST R. 
Published: July 2006

SUMMARYTo characterize the fabric of a wet soil sample two sets of experiments were performed. In one, water retention and shrinkage curves were determined with samples stored at the field water content, and in the other, pore size distribution curves and microscopic observations were made as samples progressively dried. The experiments were performed with soil samples of different aggregate sizes to determine the contribution of each class of pores to porosity.Data were analysed by comparing (i) the amount of water extracted from the sample, (ii) the air‐filled porosity of the sample and (iii) the accumulated pore volume by mercury injection, each in relation to the equivalent pore radius. This gives information on the geometry of pores developed during the drying process. It has shown that micrometric cracks in dried soils are not artefacts but the result of a more severe drying never reached by the material in the field.
Denitrification in drained and undrained arable clay soil
Authors: COLBOURN P. , HARPER I. W. 
Published: July 2006

SUMMARYEmissions of nitrous oxide (N2O) and nitrogen gas (N2) from denitrification were measured using the acetylene inhibition method on drained and undrained clay soil during November 1980‐June 1981. Drainage limited denitrification to about 65% of losses from undrained soil. Emissions from the undrained soil were in the range 1 to 12 g N ha–1 h–1 while those from the drained soil ranged from 0.5 to 6 g N ha–1 h–1 giving estimated total losses (N2O + N2) of 14 and 9 kgN ha–1.Drainage also changed the fraction of nitrous oxide in the total denitrification product. During December, emissions from the drained soil (1.8±0.6 gN ha–1 h–1) were composed entirely of nitrous oxide, but losses from the undrained soil (2.7 ± 1.1 g N ha–1 h–1) were almost entirely in the form of nitrogen gas (the fraction of N2O in the total loss was 0.02). In February denitrification declined in colder conditions and the emission of nitrous oxide from drained soil declined relative to nitrogen gas so that the fraction of N2O was 0.03 on both drainage treatments. The delayed onset of N2O reduction in the drained soil was related to oxygen and nitrate concentrations. Fertilizer applications in the spring gave rise to maximum rates of emission (5–12g N ha–1 h–1) with the balance shifting towards nitrous oxide production, so that the fraction of N2O was 0.2–0.8 in April and May.
The reactions of cadmium with calcium carbonate surfaces
Authors: PAPADOPOULOS P. , ROWELL D. L. 
Published: July 2006

SUMMARYThe reaction of cadmium with calcite was studied with 10−6–10−2M Cd2+ using 4g CaCO3 and 50 ml solution. The calcite‐water suspension was equilibrated for 2 d before adding Cd(NO3)2. The CaCO3 surface has a high affinity for Cd and at < 1 μmol g−1 a linear adsorption isotherm (C‐type) describes the reaction, whereas precipitation of CdCO3 on calcite predominates at higher Cd additions. In the latter case pH decreased and solutions were undersaturated with respect to CaCO3 indicating that CdCO3 prevented the CaCO3 surface from reacting with the acidity generated from CdCO3 precipitation. The data for low Cd additions suggests that an ideal surface solid solution is formed between CdCO3 and CaCO3 and the Thorstenson and Plummer equation expressing the pIAP values of surface solid solutions is valid. Equilibrium was attained for low Cd additions in several minutes, whereas precipitation was a slow process; at the changeover point distinction between the two processes is difficult. The reacting surface area calculated from the maximum adsorption of Cd is 0.5‐1.0 times that measured by the BET method.The Cd‐reacting surface areas of four natural calcareous minerals were much less than those found by the BET method which includes the surfaces of other minerals present. The Thorstenson and Plummer equation may be a useful way to relate solution composition and carbonate‐adsorbed Cd in contaminated soils.
Reaction kinetics of the adsorption and desorption of nickel, zinc and cadmium by goethite. I. Adsorption and diffusion of metals
Authors: BRUEMMER G. W. , GERTH J. , TILLER K. G. 
Published: July 2006

SUMMARYThe reactions of Ni, Zn and Cd with goethite were studied over a range of initial metal concentrations (10−6 to 10−4M), pH values (4 to 8), reaction times (2h to 42d) and temperatures (5 to 35°C). The adsorption of metals increased with pH, reaction time and temperature. Adsorption of Ni increased relative to Zn and Cd with increasing time and temperature. The initially rapid adsorption of metals within a few hours was followed by a much slower reaction linearly related to time1/2, interpreted as diffusion–controlled penetration of goethite. The pH–dependent relative diffusion rates (Ni > Zn > Cd) were influenced by both affinity for goethite surfaces and by ionic radius. Diffusion coefficients of the three metals ranged from about 10−19to 10−20cm2s−1. The corresponding activation energies of diffusion were also calculated (Ni 35, Cd 55, Zn 90 kJ mol−1). Our view about the reactions of heavy metals with goethite involves (i) adsorption of metals on external surfaces, (ii) solid–state diffusion of metals from external to internal binding sites, and (iii) metal binding and fixation at positions inside the goethite particles. The general parameters of these processes are related to the hydrolytic properties (pK values) and the ionic radii of the metals. The results show that goethite may be an efficient sink for trace metals.
The determination of the macroporosity of impregnated blocks of a clay soil and its relation to volumetric water content
Authors: MACKIE‐DAWSON L. A. , MULLINS C. E. , KIRKLAND J. A. , FITZPATRICK E. A. 
Published: July 2006

SUMMARYThe bulk density of slices cut from resin impregnated soil blocks was obtained by immersion in paraffin. Total porosity was then calculated using measured density of soil solids and the density of the resin. Macroporosity (> 350 μm) was obtained by image analysis and microporosity was derived as the difference between total porosity and macroporosity. On four separate sampling occasions throughout the year, there was a good agreement between values of microporosity obtained in this way and volumetric water contents measured at the time of sampling.
Transformation of poorly‐crystalline oxides during boiling with NaOH to concentrate iron oxides from soils
Authors: GOODMAN B. A. , BERROW M.L. , RUSSELL J. D. 
Published: July 2006

SUMMARYThe effect of boiling 5 M NaOH on the nature of poorly crystalline iron oxides in some iron pans from Scottish soils has been investigated by IR and Mössbauer spectroscopy in conjunction with XRD. In samples that contained goethite and other crystalline oxides there was substantial production of goethite from the less well‐defined phases as a result of the alkali treatment. Neither kaolinite nor humic acid, when added to the samples, was effective in preventing this transformation, although some inhibition was observed. There was, however, no goethite production with a pan that had no crystalline iron oxides, although this could be stimulated by the addition of small amounts of either goethite or haematite. The practice of using the boiling alkali method routinely for the concentration of crystalline iron oxides in soils should, therefore, be considered carefully, since any co‐existing crystalline and non‐crystalline phases are likely to lead to the transformation of the latter to goethite.
The genesis and classification of soils on wet terraces and moraines in New Zealand
Authors: MEW G. , LEE R. 
Published: July 2006

SUMMARYSix soils on glacial outwash terraces and one on moraine are discussed; four are formed partly in loess of unknown age. Evidence of podzolization is apparent in all profiles, but the vertical drainage under very high rainfall is insufficient to remove surplus water. Gley processes appear to dominate, in a perched‐water environment.Podzolic B horizons were identified in the same five profiles following both the Canadian system and that used by the Soil Survey of England and Wales. However, only three of these profiles could be allocated to existing podzolic subgroups in the latter system. Spodic horizons were identified in a different group of five profiles. Differences in classification are discussed with reference to the criteria used and in relation to proposals for revision of the New Zealand Soil Classification.
Interlayer materials of partially interlayered vermiculites in Dystrochrepts derived from Tertiary sediments
Authors: MATSUE N. , WADA K. 
Published: July 2006

SUMMARYInterlayer materials of partially interlayered vermiculites (PIV) in 15 Dystrochrepts derived from Tertiary sediments were analysed by dissolution with hot 1/3M sodium citrate or 0.15 M oxalate‐oxalic acid in combination with XRD and IR spectroscopy. Both the citrate and oxalate treatments dissolved Al from all soil clays. The dissolution of Al by the citrate treatment paralleled the dissolution of Si and the interlayer collapse of PIV, whereas that by the oxalate treatment did not, indicating that the interlayer materials contain not only Al but Si. The materials dissolved by the citrate treatment had a molar Si/Al ratio ranging from 0.72 to 0.24 that decreased with the increasing interlayering of PIV. Differential IR spectroscopy indicated the dissolution of aluminosilicates possibly having Si‐O, Al‐OH and Si‐O‐Al bonds, but not Si‐O‐Si bonds. The extent of interlayering of PIV showed a good correlation with the amount of Al dissolved by the citrate treatment and increased with increasing soil pH (H2O) from 4.5 to 5.2 and with decreasing exchangeable Al in soil.Formation of a hydroxy‐Al sheet partially bonded with Si‐tetrahedra was suggested as a possible model of the interlayer structure of PIV. The differences between PIV in the studied Inceptisols and other soils are discussed.
Protonation reactions of fulvic acids
Authors: GREGOR J. E. , POWELL H. K. J. 
Published: July 2006

SUMMARYThe protonation reactions of fulvic acids are described in terms of a model involving a mixture of n monoprotic acids HA, HB, HC … pH titration data were analysed by nonlinear least squares methods, using a model having n independent ‘titration’ (protonation) constants, Ki i=1 to n, and n–1 independent acid concentrations. The best fit was obtained with n=4. The results for three fulvic acid samples were in the range log K1 6.5–6.7 (∼8% of total carboxyl acidity), log K2 5.3–5.6 (∼15%), log K3 3.9–4.8 (∼20–30%) and log K4 2.6–2.7 (∼50–70%).The results indicate a comparatively small proportion (∼ 10–20%) of polyprotic carboxyl moieties in the diverse fulvic acid structures. They give some support to the Wershaw model of fulvic acids as strongly associated aggregates of acids, each of comparatively low molecular weight.
The soil solution in a soil treated with digested sewage sludge
Authors: CAMPBELL DUNCAN J. , BECKETT P. H. T. 
Published: July 2006

SUMMARYToxic trace metals may percolate to the ground water from sewage sludge disposed onto land. Analyses are presented of the soil solution from a slightly acid loamy soil treated 7 years earlier with single applications of digested sewage sludge in amounts equivalent to 0, 150 & 330 t dry matter ha−1These very heavy dressings correspond to 2 & 4.5 times the recommended 30–year limit. Samples of soil and soil solution from four depths to 80 cm were analysed for Al, B, Ba, Ca, Cl, Cu, Fe, K, Li, Mg, Mn, Na, Ni, P, S, Sr, V, Zn, together with the OM of the soil, and the pH, alkalinity, dissolved organic carbon, and absorbance at 350 nm of the solutions.These very heavy sludge applications were apparently still releasing substantial quantities of NO3, and some SO4 even after 7 years. Nitrate, SO4, Mg, Ca, Sr, B, and possibly Ba are still moving through the profile, possibly to the ground water. Solution concentrations of Cu and Zn are considerably higher at all depths than those in the untreated plot, but they fall off sharply with depth. It is unlikely that any Cu or Zn is now reaching the ground water.The paper also presents a set of published solution analyses for soils, sludge–treated soils and digested sludge, as a basis for further studies.
The topology of pore structure in cracking clay soil. II. Connectivity density and its estimation
Authors: SCOTT G. J. T. , WEBSTER R. , NORTCLIFF S. 
Published: July 2006

SUMMARYPores in soil, especially in cracking clays, interconnect in more or less complex patterns. The complexity of the pattern can be represented by its connectivity. The connectivity of a network of cracks is the number of loops in it, and the number of loops per unit volume of soil is the connectivity density (Gv).The patterns of cracks wider than 60 μm were exposed in parallel sections 50 μm apart, photographed and skeletonized. Loops were tracked from one section to another and counted. Other loops completed in three dimensions but not apparent in horizontal sections were recognized and added to the count. The counts were linearly related to the number of sections examined, and by regression analysis stable and precise estimates of Gv were obtained for the clay subsoils of Windsor and Swanwick soil series from as few as eight sections. The connectivity density of the crack pattern in the Windsor subsoil was approximately 300 cm−3 and that of the Swanwick series about 195 cm−3.
Calculation of gross nitrogen immobilization and mineralization in soil
Authors: BJARNASON S. 
Published: July 2006

SUMMARYIn a laboratory experiment, soil was treated with 15NH4‐ and 15NO3‐N compounds at various times during the incubation. Several approaches in the calculation of gross immobilization and gross mineralization between two sampling dates were compared and a new method was developed. It is based on a dynamic simulation model designed to interpret isotopic data and an optimization procedure used to determine the best fit between model output and experimental data. This flexible method was used to examine the validity of the assumptions usually made when calculating the gross transformations.The results indicate that seriously erroneous estimates of the gross transformations can follow if it is assumed that remineralization of immobilized N does not occur. Less serious errors can result from the assumption that both opposing processes occur at a constant rate during the interval between sampling dates.The combined use of the model and the optimization procedure has several advantages over traditional methods and some of the gross transformation estimates reported would not have been obtainable using older methods.
Effect of liming and phosphate additions on sulphate leaching in soils
Authors: BOLAN N. S. , SYERS J. K. , TILLMAN R. W. , SCOTTER D. R. 
Published: July 2006

SUMMARYThe effect of lime (CaCO3) and phosphate additions on surface charge characteristics and their effect on the leaching of sulphate were examined for two soils (Patua loam and Tokomaru silt loam) which differed in their adsorption capacities for sulphate.Incubation of soils with either CaCO3 (0–600 mmol kg−1) or phosphate (0‐208 mmol kg−1) resulted in a two‐ to five‐fold increase in the net negative charge and a similar decrease in the adsorption of sulphate. The effect of either lime or phosphate addition on both the surface charge and sulphate adsorption was more pronounced for the allophanic Patua soil than for the Tokomaru soil containing mainly vermiculite.In a column experiment, liming induced the leaching of sulphur either by the desorp‐tion of adsorbed sulphate or by the mineralization of organic sulphur. During a miscible displacement study, addition of either CaCO3 or phosphate resulted in an early breakthrough of sulphate in the leachate. In a pulse experiment, in which soils were incubated with sulphate (3.12 mmol kg−1) for 1 week and subsequently leached with water, more added sulphate was lost in the leachate of the soils previously incubated with either CaCO3 or phosphate.