bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interference by organic complexation of Fe and A1 on the SO2‐4 adsorption in Spodic B horizons in Sweden
Authors: KARLTUN E. , GUSTAFSSON J. P. 
Published: July 2006

SUMMARYThe relations between pH, different fractions of Fe and A1 and Na4P2O7‐soluble C and the amount of adsorbed SO2‐4 were assessed by analysing 63 soil samples from 14 podsolized soils in Sweden. The amount of adsorbed SO2‐4 was significantly better correlated with the calculated amount of the inorganic fraction of Fe and A1 oxides obtained by subtracting Na4P2O7‐soluble Fe and A1 from oxalate‐soluble Fe and Al than with the oxalate extraction alone. There was a close correlation between C and organically‐bound S in the Na4P2O7 extract which shows that the C:S ratio of the extracted fulvic acids is about constant in the soils studied. It was found that, as the proportion of organically‐complexed Fe and Al increases, the ability of the soil to adsorb SO2‐4 decreases. The amount of adsorbed SO2‐4 expressed on the basis of the amounts of oxalate‐soluble Fe and Al was generally smaller in areas with low S deposition (< 60 mmol m‐2 a‐1). The ratio between pyrophosphate‐soluble C and oxalate‐extractable Fe and Al was negatively correlated with pH in water. It was concluded that Fe and Al associated with organic matter cannot adsorb SO2‐4 and that the degree of this association is pH dependent. These observations have important implications regarding the effects of anthropogenic acidification.
Simple determination of nitrate in soils by second‐derivative spectroscopy
Authors: SEMPERE A. , OLIVER J. , RAMOS C. 
Published: July 2006

SUMMARYA new and simple method for nitrate analysis in soil extracts and soil solution is described. The method uses the second derivative of the direct ultra‐violet (UV) spectrum, available from most microprocessor‐controlled spectrophotometers with a UV source. Results with the proposed method were similar to those obtained by the cadmium‐reduction column and ion‐chromatographic methods. The main advantages of the proposed technique are that it is simple, rapid, accurate and requires no sample pre‐treatment, making it useful for routine analysis of large numbers of samples.
Fragipan formation in argillic brown earths (Fragiudalfs) of the Milfield Plain, north‐east England. III. Micromorphological, SEM and EDXRA studies of fragipan degradation and the development of glossic features
Authors: PAYTON R. W. 
Published: July 2006

SUMMARYThe micromorphology of eluvial and glossic areas with weak soi1, strength from the upper fragipan, and the upper parts of grey polygonal zones, in some argillic brown earths (Glossic Fragiudalfs) from north‐east England shows unstable void walls stripped of clay with remnants of ferri‐argillans, pale grey grainy clay coatings and darker grainy coatings. These occur alongside loose surface residues of skeleton grains and thin grey fine silt coatings of quartz and muscovite. SEM and EDAX studies of coating surfaces, and optical microscopy, SEM and EDXRA of very thin polished sections, show that some grainy clay coatings form as alteration rims of ferri‐argillans through localized waterlogging, iron oxide loss and micro‐erosion leading to micropitting and disoriented fabrics. The inclusion of coarse clay to fine silt‐sized quartz, feldspar and muscovite in other grainy coatings suggests either alteration of impure ferri‐argillans or accumulation of degradational products derived from elsewhere on void walls. This is more certainly the case for dark grainy coatings in layered compound illuviation coatings adjacent to glossic areas. These fragipans are degrading from the top downwards by processes which are partly a consequence of the effects that the fragipan has on water percolation and root penetration. The destabilization of void walls, the degradation of ferri‐argillans and the remobilization of clay to form glossic features did not begin until seasonal waterlogging in parts of the upper pan was sufficient to mobilize iron.
Measurement of soil gas diffusivity in situ
Authors: BALL B.C. , GLASBEY C.A. , ROBERTSON E.A.G. 
Published: July 2006

SummaryAssessment of gas diffusivity in situ gives a direct measure of the ability of soils to exchange gas with minimal soil disturbance. A versatile, readily portable probe for measuring the diffusion of a tracer gas through soil in situ is described. The radioactive tracer 85Kr is injected into a cell located at the end of the probe. The change in activity within the cell as the gas diffuses out is measured by a Geiger‐Muller tube in the cell. The probe can be used by insertion either directly into an auger hole (buried‐probe mode) or into a chamber pushed into the soil surface. A method to simulate diffusion numerically using Fick's equation for both methods of insertion is presented. In the tests reported, diffusivity was estimated by expanding or contracting the time axis of the simulation until it matched the observed count rates. A goodness‐of‐fit was attached to each diffusivity estimate. The probe was generally effective, giving diffusivities comparable to those measured in the laboratory on cores taken near the cell (buried‐probe mode) or linked to the surface chamber. Poor fits were found for some diffusivities measured in the buried‐probe mode on coarsely structured soils. These were attributed to non‐uniform distribution of porosity and possible upward leakage of tracer when used at shallow depths in the buried‐probe mode. However, thein situ diffusivities may be more representative than those measured in cores in the laboratory because of the greater sample volume. We show how the probe can be used to detect soil layers that restrict gas diffusivity and differences in aeration status between tillage treatments.
Structural collapse and strength of some Australian soils in relation to hard setting: I. Structural collapse on wetting and draining
Authors: GUSLI S. , CASS A. , MACLEOD D.A. , BLACKWELL P.S. 
Published: July 2006

SummaryThe surface structure of many Australian red and red‐brown earths frequently collapses (slakes) when dry, disturbed aggregates are wetted by rain or irrigation. The resulting fine matrix sets, on drying, to a strong, cohesive layer of up to 200 mm thick (hard setting). We investigated the mechanism of collapse and the extent to which the structure of aggregate beds Iron hard setting and non‐hard setting soils collapsed when wetted by quick flooding or slowly with water at a suction of 200 mm, then drained in sequential steps of increasing suction and finally dried at 40°C. After flood wetting, but before draining, no collapse was observed due to the small effective stress prevalent in the flooded beds.After suction wetting, some collapse was measured owing to the effective stress (approximately 1.4 kPa) from the applied suction. On draining, flood‐wetted beds collapsed extensively (volume strain >0.20), largely due to the disappearance of large pores (>75 μm diameter). Suction‐wetted beds collapsed less (volume strain <0.16) and retained more large pores. Hard setting soils collapsed more following both flood and suction wetting (volume strain >0.20 and 0.10, respectively), while non‐hard setting soils did not collapse as extensively (volume strain <0.16 and 0.09, respectively). Results indicate that the mechanism causing collapse was independent of wetting method and involved two steps: (i) slaking of aggregates on wetting, and (ii) collapse of the aggregate bed on draining as a result of development of effective stress within the beds.
Effect on Colwell soil‐test P of storing air‐dry soil samples at room temperature for up to seventeen years
Authors: BOLLAND M.D.A. , DHALIWAL J. , BOWDEN J.W. , ALLEN D.G. 
Published: July 2006

SummaryWe wished to determine whether soil‐test P was affected by storing air‐dry soil samples at room temperature. The soil samples had been collected from field experiments and air‐dried (<40°C) before measuring soil‐test P (bicarbonate‐extractable P). The samples were from field plots that had been treated with different applications of fertilizer P (superphosphate, rock phosphate) one or more years previously. Soil‐test P was measured on two different sub samples of the same sample: either A, in the year the sample was collected; or B, after the sample had been stored at fluctuating room temperatures either from 2 to 8 years (four field experiments) or 17 years (59 field experiments). The room temperature ranged from 10 to 30°C, and averaged 17°C. The aim was to test whether soil‐test P was systematically and consistently different between sub samples A and B.Differences between A and B were mostly small, and there were no consistent or systematic differences. For the Colwell soil test, applied to a range of south‐western Australian soils, possible decreases in soil‐test P due to continued reaction with the soil could not be detected using bicarbonate‐extractable soil P, and storage of air‐dry samples at room temperature did not significantly affect soil‐test P measured up to 17 years later. We conclude that, provided fertilizer P has had time to react with soil in the field, no further changes in Colwell soil‐test P occur during air‐dry storage for up to 17 years at room temperature.
Evidence of biogenic greigite (ferrimagnetic Fe3S4) in soil
Authors: STANJEK H. , FASSBINDER J. W. E. , VALI H. , WÄGELE H. , GRAF W. 
Published: July 2006

SummaryThe occurrence of greigite (Fe3S4) in soils is reported for the first time. It forms irregularly‐shaped aggregations within plant cells in the Gr2 horizon of a gley soil developed from colluvial material. Greigite was identified by X‐ray diffraction and magnetic measurements and was investigated by optical and transmission electron microscopy. Biogenic formation is proposed, based on the elongated shape of single greigite crystals, and sulphur isotope analyses, which showed a depletion in 34S relative to the soil‐water sulphate. The cell‐edge length of 0.98639±0.00003 nm is significantly smaller than values reported for sedimentary greigite. The mean coherence length of 27 nm agrees with TEM observations and indicates that the single greigite crystals lie in the superparamagnetic region. However, the fine aggregates show magnetically single‐domain behaviour. Greigite is the only carrier of a stable magnetic remanence in the soil profile studied.
The effect of energy peak drift on the calibration of a high resolution gamma‐ray soil density gauge
Authors: HENSHALL J.K. 
Published: July 2006

SummaryHigh spatial resolution is obtained from a gamma‐ray transmission density gauge by restricting the measured counts to a narrow band of the energy spectrum, close to the emission energy peak. The effect on measurement accuracy of any movement of this measurement window relative to the energy peak was investigated. The findings were related to anticipated energy peak movements in a proposed LED‐based gain‐stabilization system.Movements of the energy peaks during recording of unstabilized spectra prevented direct comparisons of spectra at different positions. A simulation procedure was, therefore, developed in which movements of the measurement window relative to sets of stable calibration spectra were examined.When analysing spectra, recorded using a gauge with a different gain‐stabilization system, accuracy was found to be unaffected by simulated peak movements of up to 0.03 MeV in the direction of increasing energy. However, movements of stabilized spectra in the direction of decreasing energy, and of unstabilized spectra in either direction, increased measurement errors to twice the level of inherent measurement errors within 0.02 MeV, with errors in bulk density of up to 0.7 Mg m−3 for movements of 0.1 MeV. The spectra of the new LED‐based stabilization system are expected to behave in a manner similar to the unstabilized system, therefore requiring regular monitoring of the peak position.
Applications of fertilizer cations affect cadmium and zinc concentrations in soil solutions and uptake by plants
Authors: LORENZ S.E. , HAMON R. E. , McGRATH S.P. , HOLM P.E. , CHRISTENSEN T.H. 
Published: July 2006

SummaryA pot experiment was conducted to study changes over time of Cd and Zn in soil solution and in plants. Radish was grown in a soil which had been contaminated with heavy metals prior to 1961. Constant amounts of a fertilizer solution (NH4NO3, KNO3) were added daily. Soil solution was obtained at intervals by displacement with water.The cumulative additions of small amounts of fertilizers were made equal to the plants' requirements at the final harvest but were found to exceed them during most of the experiment. Excess fertilizers caused substantial increases of major (K, Ca, Mg) and heavy‐metal (Cd, Zn) ions in soil solutions and a decrease in soil pH, probably due to ion‐exchange mechanisms and the dissolution of carbonates.Uptake of Cd and Zn into leaves was correlated with the mass flow of Cd (adjusted r2= 0.798) and Zn (adjusted r2= 0.859). Uptake of K, Ca and Mg by the plants was independent of their concentrations in solution.It is concluded that, in order to study effects of plants on heavy‐metal availability and obtain soil solution that has not been altered by fertilizer ions, nutrients must be added according to the needs and growth of the plants. This could be achieved by linking fertilizer additions to the rate of transpiration, as nutrient uptake and transpiration were closely correlated in this experiment.
Calculating the annual input of organic matter to soil from measurements of total organic carbon and radiocarbon
Authors: JENKINSON D.S. , COLEMAN K. 
Published: July 2006

SummaryMeasurements of total organic C, δ13C and δ14C are given for topsoils taken from six experimental sites in southern England. At each site, some of the samples were collected before and some after the thermonuclear tests of the early 1960s, so that pre‐ and post‐bomb samples could be compared for radiocarbon content. The current Rothamsted model for the turnover of organic C in soil gave an acceptable fit to the data from five of the sites, apart from one aberrant radiocarbon measurement. The annual input of C to the topsoil was calculated for the five sites from these fits; the values obtained were: 0.15 t C ha−1 a−l for a site on silty clay loam, kept bare by hand weeding since 1870; 0.2 for unmanured spring barley growing on a sandy loam; 2.95 for a fertilized all‐arable rotation on a loamy sand; 1.9 for the same fertilized all‐arable rotation on a silty loam and 2.5 from this rotation on a calcareous silty loam. The corresponding values for Net Primary Production at the five sites were 0.15, 0.76, 5.16, 5.71 and 5.46 t C ha−1 a−l. In fitting the model to the radiocarbon data it was necessary to postulate that all these sites contained substantial quantities of biologically‐inert organic matter, ranging from 2.2 to 10.0 t C ha−1.
Incorporation of natural monoacids from plant residues into an hydromorphic forest podzol
Authors: AMBLÈS A. , JAMBU P. , PARLANTI E. , JOFFRE J. , RIFFE C. 
Published: July 2006

SummaryThe monoacid part of soil lipids was studied in a hydromorphic sandy podzol under pine trees (Pinus maritima sp.). The undecomposed forest‐litter layer (L), the fragmented mycelium‐invaded litter layer (F) and the A1 soil horizon were sampled, and analysed for total lipid and total monoacid contents. Total monoacids were separated into straight‐chain components and terpenic components.Straight‐chain monoacids were determined as free acids and esters of fatty alcohols and of glycerol. Among these components, branched alkanoic acids occurred in the A1 soil horizon. Alkenoic acids were mainly determined as glycerides. Free n‐alkanoic acids were mainly produced in soil from terminal oxidation of plant n‐alkanes and plant n‐alkanols. Free alkanoic acids with the longest carbon chains and alkanoic acids esterified as glycerides were concentrated in the A1 soil horizon.Terpenic monoacids were mainly diterpenic components from pine resin. Their concentration decreased markedly during the decomposition of plant debris.
The effect of spruce (Picea abies Karst.) on soil development: an analytical and experimental approach
Authors: RANGER J. , NYS C. 
Published: July 2006

SummaryChanges in soil and biogeochemical processes following the replacement, 60 years ago, of part of a deciduous forest by a coniferous stand were evaluated by (i) a balance‐sheet approach using soil and biomass element content analyses and the mineral flux, and (ii) the inclusion of test‐mineral and resin bags in an integrative experimental approach.The comparison of soils under different stands shows that the change to spruce is inducing physical, chemical and biological modifications in soil properties. Changes in the humus layers lead to a reduction in mineralization and the mobilization of active organic acids in the system. Under spruce, the soil structural stability is reduced as fine clay is dispersed. Soil acidification is increased, linked to a decrease in soil pH and desaturation of the soil exchange complex. Soil mineralogy also indicates this tendency, particularly with an increase in the stability of Al intergrades. The biogeochemical cycle is modified especially for N, S and Al. with large changes in the internal fluxes between the ecosystem components, but the modification of the input‐output balance due to spruce introduction is large only for S.The acidification is partly due to a change in litter quality, which inhibits biological activity, and partly because, during the dormant season, evergreen species intercept ‘dry and occult’ depositions from the atmosphere containing acidic or potentially acidic components.Use of test‐mineral bags improves understanding and interpretation of the current soil mechanisms. The test mineral, a vermiculite, introduced into the soil or placed in the lysimeter flux very quickly undergoes measurable transformation characterized by desaturation and fixation of non‐exchangeable Al in the interlayer zone, easily identified by Al speciation. The acidifying effect of spruce is clearly demonstrated by the experimental approach used, including the characterization of soil solutions by resin bags.All the techniques are complementary and could be used together or individually, depending on the aim of the study.
Choosing models for soil chronofunctions and fitting them to data
Authors: SCHAETZL R.J. , BARRETT L.R. , WINKLER J.A. 
Published: July 2006

SummaryThe effectiveness and utility of soil chronofunctions is examined in the light of existing pedogenic theory. Statistical treatments applied in chronofunction research are reviewed, including linear transformations of raw data, which may improve the utility of the chronofunction. We advocate using a particular statistical model only if it can be justified based on our current understanding of the functioning of the pedologic system. We emphasize the potential difficulties of using linear chronofunction methods; simple linear and logarithmic functions are not always the best option for chronofunctions. Hyperbolic, polynomial or nonlinear functions might improve not only the fit of the chronofunction but also advance our understanding of the pedologic system.When the chronofunction explaining the most variance is not best suited to a process‐based understanding of pedogenic theory, other functions with slightly smaller r2 values that have been judged suitable by a priori reasoning or theory might better reflect the functioning of the pedologic system. We justify limited extrapolation of some chronofunctions to time zero and discuss how this can be useful in the identification of pedogenic thresholds and ‘step functions’. Interpretation of the Y‐intercept of chronofunctions can, at times, aid our understanding of the soil system near time zero and be useful in the identification of the existence and timing of thresholds.
Conservation of mineral nitrogen in restored soils at opencast coal mine sites: I. Results from field studies of nitrogen transformations following restoration
Authors: JOHNSON D. B. , WILLIAMSON J. C. 
Published: July 2006

SummaryOne of the characteristics of soils located within the cores of stockpile storage mounds at opencast mine sites is their accumulation of ammonium‐nitrogen. Two areas of restored land were constructed from soil stockpiled for 3 years; one consisted of mound‐surface (‘aerobic zone’) soil, and the other of deeply buried (‘anaerobic zone’) soil. In that constructed from mound‐surface soil, concentrations of both ammonium‐ and nitrate‐nitrogen remained fairly stable throughout the first 6 months of restoration at about 12–20 μg g−1, but in the site constructed from deeply buried soil, concentrations of ammonium‐N decreased from an initial high of 160 to 14 μg N g−1 soil after 14 weeks, and increased again to 42 μg N g−1 soil by week 29. In contrast, concentrations of nitrate‐nitrogen at the latter site increased from an initial 9 μg to a maximum recorded level of 77 μg N g−1 soil by week 14, before subsiding to 9 μg N g−1 soil by week 29. Nitrate was considered to have been lost from the restored soils by a combination of leaching and denitrification, as no vegetation was established at these sites. After a short‐term stimulation following restoration, soil microbial biomass levels remained fairly constant, though soils (up to 3 years after restoration) were characterized by a very small ratio of biomass C: organic C.
Identification of free amino acids in peat by gas chromatography and mass spectrometry
Authors: KUNNAS A.V. , ERONEN M. 
Published: July 2006

SummaryThe qualitative and quantitative composition of free amino acids in a typical Finnish peat bog at various depths down to 5.3 m below the surface was studied using capillary gas chromatography and mass spectrometry.Sixteen amino acids were identified at each depth: α‐alanine, β‐alanine, glycine, valine, leucine, proline, isoleucine, serine, threonine, glutamic acid, aspartic acid, phenylalanine, tyrosine, γ‐aminobutyric acid, ornithine and lysine. Their amounts decreased markedly at a depth of 40–100 cm. The total amount of amino acids varied between 0.6 and 5.6 g kg−1 dry matter (i.e. 0.06–0.56%) depending on the depth. The proportion of neutral amino acids was greatest at all depths studied, except at the surface layer where it ranged between 41 and 72% by mass. The acidic amino acids decreased with depth from 56 to 23% of the total. The proportion of aromatic amino acids was very small, 3.2–5.5% by mass.In samples from aerobic conditions, where the microbial production of free amino acids was the greatest, α‐ala, gly, glu and asp were most abundant. In peat from anaerobic conditions, where the microbiological activity was low, the proportion of the most chemically stable amino acid was exceptionally high. This may have been because glycine was a degradation product of other amino acids or peptides.Peat type and degree of decomposition had a strong influence on the total amount of free amino acids and their qualitative composition.