bluuebunny/crossref_metadata_2025_split huggingface dataset:
Use of 137Cs measurements to investigate soil erosion on arable fields in the UK: potential applications and limitations
Authors: WALLING D. E. , QUINE T. A. 
Published: July 2006

SUMMARYRecent awareness of the potential hazard of soil erosion on arable land in the UK has highlighted the lack of reliable data concerning actual rates of soil loss. This lack of information reflects both a low level of interest, and the lack of a simple and generally applicable method of documenting long‐term rates of soil loss. Existing methods involving the use of hazard classification procedures and direct measurement techniques, including erosion plots and field surveys, all possess significant limitations. The use of 137Cs measurements to provide information on rates of soil loss and deposition averaged over the past 30 years would appear to offer considerable potential. The results of applying this approach to three arable fields on contrasting soil types in Britain are reported. These results confirm the viability of the technique and its potential for providing information on patterns and rates of erosion and deposition within individual fields and their overall sediment budgets. Limitations include the restricted size of the areas that can be investigated and the need to take account of additional inputs of 137Cs derived from the Chernobyl accident.
Aggregation of soil particles by iron oxides in various size fractions of soil B horizons
Authors: BARBERIS E. , MARSAN F. AJMONE , BOERO V. , ARDUINO E. 
Published: July 2006

SUMMARYQuantitative relationships between aggregation of soil particles and the content of haematite and goethite were studied by removing iron oxides, with dithionitetrate‐bicarbonate (DCB) and oxalate reagents, from various sizes of soil separates which were stable to sodium hexametaphosphate, and then determining the particle‐size distribution. Significant quantitative relationships were found between DCB‐extractable oxides and particles obtained from the separates up to 20 pm, whereas oxalate‐extractable oxides were correlated only with < 0.2‐μm particles. Oxalate‐extractable oxides were observed to aggregate a greater quantity of fine clay and a larger surface area of particles per gram of oxide than DCB‐extractable oxides, A more efficient mechanism of aggregation was postulated for the oxalate‐extractable oxides than for the DCB‐extractable oxides. There were fewer aggregated particles in soils containing haematite and goethite than in soils containing only goethite. This was attributed to differences in pedoenvironment, rather than to a difference in the behaviour of the oxides. Although various clay minerals were identified in the soils studied, no preferential aggregation of any mineral was observed.
Two models for the leaching of a non‐reactive solute to a mole drain
Authors: SCOTTER D. R. , HENG L. K. , WHITE R. E. 
Published: July 2006

SUMMARYTwo models of solute leaching to a mole‐pipe drainage system are described. The first model is research‐oriented. It simplifies two‐dimensional water and solute flow to a mole drain by dividing the soil between the mid‐mole plane and the mole into notional compartments. Solute movement between compartments is assumed to occur by convection andmechanical dispersion. Within each compartment a mobile and immobile solute phase is defined, with diffusion occurring between them. Rainfall intensity (over approximately hourly intervals) and basic soil hydraulic data are needed as inputs. An explicit finite‐difference solution to the water and solute mass‐balance and flux equations is used.The second simpler model is management‐oriented. It uses daily time steps, and assumes the soil solution behaves as if it were well‐mixed system. It requires only daily rainfall and evaporation data, the drainage coefficient of the mole‐pipe system, and the soil macroporosity as inputs. In both models a source/sink term accounts for additions of solute in rainfall and fertilizer, and extraction by plant uptake.The models were used to simulate leaching losses of chloride to a mole‐pipe drainage system in a silt loam under pasture, following the application of potassium chloride to the soil surface. The first model simulated leaching better immediately after ertilizer application, and during bypass flow induced by heavy rain. However, both models were able to simulate the measured losses over a 2‐year period equally well.
Characteristics of membrane filters in relation to aluminium studies in soil solutions and natural waters
Authors: MENZIES N. W. , BELL L. C. , EDWARDS D. G. 
Published: July 2006

SUMMARYPotential vitiative effects of Millipore 0.45‐, 0.22‐, 0.05‐ and 0.025‐pm filter elements on aqueous samples were investigated. All the filter elements evaluated exhibited a cation exchange capacity (CEC); in the case of 0.025‐pm filter elements, the CEC increased with pH. Filtration of 20 μM AlCl3/1.65 mM CaCl2, solutions (I∼0.005 M) to 0.45, 0.22 and 0.05 pm resulted in no significant change in solution A1 concentration. Filtration through 0.025‐μm filter elements significantly reduced the total A1 present in solutions adjusted to pH 4.5 and 5.0; the A1 concentration of solution adjusted to pH 4.0 was not altered. The removal of A1 from pH 4.5 and pH 5.0 solutions was attributed to the retention of A1 hydroxide micro‐particulates formed during pH adjustment of the AlCl3/CaCI2, solution. Adsorption of A1 by the filter element was not significant.Soil solutions were analysed without filtering and after filtration to 0.45,0.22,0.05 and 0.025 pm. Filtration had no effect on the concentration of the major anions (Cl−, SO24 ‐, NO13) or cations (Ca++, Mg++, Na+, K+). However, filtration to 0.05 and 0.025 pm resulted in significant reductions in the concentration of Al, Fe, Si and organic C in some samples. In soil solutions for which filtration resulted in the removal of large amounts of particulate material, the solution appeared less coloured after filtration and exhibited lower absorbance in the visible spectrum (4O(MOO nm). However, the absence of colour did not preclude the presence of colloidal particles.
The effect of alternate freezing and thawing on aggregate stability and aggregate size distribution of some Prince Edward Island soils
Authors: EDWARDS L. M. 
Published: July 2006

SUMMARYThe effect of 1–15 daily freeze/thaw cycles on aggregate stability (S) and aggregate‐size distribution measured as mean‐weight diameter (MWD) was investigated for loam, sandy loam and fine sandy loam (FSL) soils; and two aggregate‐wetting procedures, spray‐wetting and vacuum‐wetting, were compared. Initially, S and MWD decreased rapidly until about the fifth freeze/thaw cycle, thereafter change occurred progressively less rapidly reaching a minimum value at about the 10th cycle. Sand MWD in the loam, which had the greatest content of clay and iron oxides, decreased significantly less rapidly than in the other soils. The sandy loam, with the least clay but the most organic matter, was intermediate in behaviour. Macro‐aggregate (>4.75 mm) content of the FSL decreased from 40% initially to 12% of total mass by the 15th cycle, while the micro‐aggregate (<0.5 mm) content increased from 19% to almost 70% of total mass. In contrast, the loam retained many macro‐aggregates, with a decrease from an 80% macro‐aggregate content to 60% of total mass by the 15th cycle. With an average of about 40 freeze/thaw cycles occurring during a Prince Edward Island winter, S and MWD in both the sandy loam and the FSL will reach minima by the end of winter. In contrast, Sand MWD in the loam will not have reached a minimum by the end of winter. These results are related to the erosive behaviour of the three soils.Data on S and MWD of samples exposed to the two wetting procedures followed similar trends with number of freeze/thaw cycles (r=0.84 to 0.99); but spray‐wetting gave less variable results than did vacuum‐wetting and was a simpler procedure.
Soil mechanical properties as influenced by exchangeable cations
Authors: DEXTER A. R. , CHANT K. Y. 
Published: July 2006

SUMMARYThe tensile strengths of dried, undisturbed aggregates and of dried, artificial aggregates and the shear strengths of freshly‐moulded, moist soils were investigated as functions of their contents of exchangeable cations.Tensile strength increased with increasing exchangeable sodium and decreased with increasing exchangeable calcium. Shear strength of moist soil, as assessed through the Atterberg limits, increased with increasing exchangeable calcium, potassium and sodium. The influence of exchangeable magnesium was variable in that it tended to increase the tensile strength of the soils when dry, whereas it tended to decrease the shear strength of one of the sets of soils in the moist state.It is concluded that the exchangeable cations which give rise to greater repulsion between, and dispersion of, clay particles in water also give rise to greater strength in the dried soil. It is proposed that this is because greater particle repulsion in the soil water during drying enables particle rearrangements to take place more readily and this results in denser packing arrangements and increased strength.
method for assessing the goodness of computer simulation of soil processes
Authors: WHITMORE A. P. 
Published: July 2006

SUMMARYAny satisfactory computer simulation model of a soil process must match actual behaviour in the laboratory or field; a model can be evaluated by how well it does so. This paper describes a method for assessing models using anion diffusion and nitrate leaching as examples. The method partitions the sum of squares of the differences between measurement and simulation into two components, one calculated from the differences between the simulation and the mean of replicate measurements (the ‘lack of fit’), and the other calculated from the variance within each set of replicate measurements (the ‘pure error’). If the former is not significantly larger than the latter than the data present no grounds for rejecting the model. Where a model simulates the change in a process with time the method can also take account of how experimental error in the initial measurements affects the goodness of fit of the simulation of subsequent measurements.The method is particularly valuable where it is difficult or costly to take many replicate measurements, such as often happens in soil science or agriculture; nonetheless, some replicates must be taken.
Effect of heating on phosphate sorption and availability in some north‐east Nigerian soils
Authors: KWARI J. D. , BATEY T. 
Published: July 2006

SUMMARYStudies on phosphate sorption and availability in some north‐east Nigerian soils showed that phosphate adsorption and inorganic‐P concentrations increased considerably after the soil was heated either in a furnace or during the field‐burning of straw. The increase in phosphate adsorption after heating was thought to be caused by an increase in free Fe and A1 oxides, whereas the high contents of exchangeable Ca and possibly carbonates and hydroxyl ions in the ash were probably responsible for the increase in phosphate sorption after field‐burning of straw.Investigations into the availability of P to maize over a 7‐d period of growth showed that there was no significant nutritional benefit from the P released after soil heating. The effect of heating was to increase P sorption and so reduce P in solution and P availability.
Empirical evaluation of the relationship between soil dielectric constant and volumetric water content as the basis for calibrating soil moisture measurements by TDR
Authors: ROTH C. H. , MALICKI M. A. , PLAGGE R. 
Published: July 2006

SUMMARYThe paper is addressed to soil scientists who use Time‐Domain Reflectometry (TDR) technology to measure soil moisture. The practical aspects of the measurement calibration are discussed, and an empirical approach to establishing the existence of a universal calibration function is presented.Samples of 11 mineral soil horizons and seven organic soil horizons with different chemical and physical properties (including magnetic properties) were selected with the aim of determining their dielectric constant‐volumetric water content relationship as calibration functions for TDR soil moisture measurements. These samples were supplemented by other, soil‐like, capillary‐porous reference materials (montmorillonite, glass beads, washed sand and a sand from a C horizon).The study showed that a unique calibration function for mineral soils and another distinct calibration function for organic soils can be established.
The influence of soil clay constituents on surface free energy of clay fractions
Authors: JAŃCZUK B. , BIALOPIOTROWICZ T. , ZDZIENNICKA A. , HAJNOS M. , JÓZEFACIUK G. 
Published: July 2006

SUMMARYMeasurements were made of the contact angle for glycerol, di‐iodomethane and cis‐decalin drops settled on the surface of pellets prepared from sodium forms of clay fractions of soils before and after successive removal of organic matter, iron and aluminium. On the basis of contact angles thus measured and a modified Young equation, the dispersive and non‐dispersive components of the surface free energy of the clay fractions were calculated. It was found that the non‐dispersive component decreased linearly with an increase in organic matter content, and with Fe and Al in the clay fractions of the soils studied. However, the dispersive component was not dependent on organic matter content, but decreased with increasing content of Fe and Al in the clay fractions studied.
A continuum approach to soil classification by modified fuzzy k‐means with extragrades
Authors: McBratney A. B. , de Gruijter J. J. 
Published: July 2006

SUMMARYThe need for a more continuous approach to soil classification is discussed, and methods based on the mathematical constructs known as fuzzy sets are considered most appropriate for this. A centroidal grouping method, fuzzy k‐means with extragrades, which quantifies the intragrading and extragrading of soil individuals is described. An example of the application of this technique to an area of 4800 ha at Wesepe in The Netherlands is presented. The results show that the technique could create a classification that reflects the main pedological features of the area in a continuous way. Although there may be problems in selecting the optimal number of groups and degree of fuzziness, we conclude that the method is most promising and worthy of consideration when any type of quantitative soil classification is required.
Fuzzy classification methods for determining land suitability from soil profile observations and topography
Authors: BURROUGH P. A. , MACMILLAN R. A. , van DEURSEN W. 
Published: July 2006

SUMMARYBecause conventional Boolean retrieval of soil survey data and logical models for assessing land suitability treat both spatial units and attribute value ranges as exactly specifiable quantities, they ignore the continuous nature of soil and landscape variation and uncertainties in measurement which can result in the misclassification of sites that just fail to match strictly defined requirements. This paper uses fuzzy classification to determine land suitability from (i) multivariate point observations of soil attributes, (ii) topographically controlled site drainage conditions, and (iii) minimum contiguous areas, and compares the results obtained with conventional Boolean methods. The methods are illustrated using data from the Alberta Agricultural Department experimental farm at Lacombe in Alberta, Canada. Data on site elevation and soil chemical and physical properties measured at 154 soil profiles were interpolated by ordinary block kriging to 15 m × 15 m cells on a 50 × 50 grid. The soil property data for each cell were classified by Boolean and fuzzy methods. The digital elevation model created by interpolating the elevation data was used to determine the surface drainage network and map it in terms of the numbers of cells draining through each cell on the grid. This map was reclassified to yield Boolean and fuzzy maps of surface wetness which were then intersected with the soil profile classes. The resulting classification maps were examined for contiguity to locate areas where a block of minimum size (45m × 45m) could be located successfully. In this study Boolean methods reject larger numbers of cells than fuzzy classification, and select cells that are insufficiently contiguous to meet the aims of the land classification. Fuzzy methods produce contiguous areas and reject less information at all stages of the analyses than Boolean methods. They are much better than Boolean methods for classification of continuous variation, such as the results of the drainage analysis.
Neoformed aragonite in clay soils on Keuper materials from east‐central Spain
Authors: LAYA H. A. , DE LA PEÑA J. A. , BENAYAS J. 
Published: July 2006

SUMMARYFibrous radial aragonite nodules occur in a toposequence developed in the Triassic (Keuper) in a subhumid mediterranean climate (Soria, Spain).Neoformation in situ of the nodules in these soils is proposed, on micromorphological and physico‐chemical grounds, such as their fragility, the inclusion of material from the groundmass, their occurrence along cracks and their high Mg: Ca ratio.
The effects of sulphate and fluoride on the sorption of aluminium by an oxisol
Authors: GIBSON J. A. E. , WILLETT I. R. , BOND W. J. 
Published: July 2006

SUMMARYThe sorption of aluminium by an Oxisol in the presence of sulphate or fluoride was studied to determine the effects of these co‐ordinating anions on the distribution of aluminium between the solid and solution phases. Addition of sulphate increased aluminium sorption, probably due to a sulphate‐induced increase in negative surface charge. In contrast, fluoride was found to depress sorption due to the decrease in the average charge of the aluminium‐containing species resulting from the formation of fluoro‐aluminium complexes.The pH of the equilibrium mixtures was linearly related to the pAl3+. This relationship held regardless of the concentrations of fluore or sulphato‐aluminium species. Equilibrium pH and pAl3+ appeared to be controlled by gibbsite.
Importance of proton supply and calcium‐sink size in the dissolution of phosphate rock materials of different reactivity in soil
Authors: ROBINSON J. S. , SYERS J. K. , BOLAN N. S. 
Published: July 2006

SUMMARYThe dissolution of a range of phosphate rock (PR) materials (Gafsa, GPR; Jordan, JPR; North Florida, NFPR; and Tundulu, TPR) was evaluated in three UK soils (Nercwys, Davidstow and Withnell) which differed in proton supply and P‐buffer capacity. The Ca‐sink size was adjusted by adding different amounts of a cation‐exchange resin (CER) to the soils. In the presence of a large proton supply (pHw 3.8–4.8, pH‐buffer capacity 52.5–36.5 mmol OH− kg−1 pH unit−1), the dissolution of GPR, JPR and NFPR in the Nercwys and Davidstow soil‐CER mixtures was strongly influenced by the size of the Ca sink. A twofold increase in Ca‐sink size in these two soils caused an increase in PR dissolution of 44–120%. Except for TPR, the increase in PR dissolution per unit increase in Ca‐sink size was the same for the three PR materials. In the Withnell soil‐CER mixtures, where the initial proton supply was relatively small (pHw 4.8–6.1, pH‐buffer capacity 23.7–21.4 mmol OH− kg−1 pH unit−1), the increase in PR dissolution with increasing Ca‐sink size was less (24–68%) than in the other two soils (44–120%). Also, for the Withnell soil, the increase in PR dissolution with increasing Ca‐sink size decreased in the order GPR (68%) > JPR (49%) > NFPR (24%), a trend consistent with the decrease in PR reactivity. The maximum dissolution of TPR was only 8–22% under favourable conditions of proton supply and Ca sink, and was little affected by Ca‐sink size.
The influence of humus fractionation on the chemical composition of soil organic matter studied by solid‐state 13C NMR
Authors: KROSSHAVN M. , KÖGEL‐KNABNER I. , SOUTHON T. E. , STEINNES E. 
Published: July 2006

SUMMARYFour samples of soil organic matter and their humic acids, fulvic acids and humin were studied with solid‐state 13CP MAS NMR. The whole soil samples were fractionated using NaOH and HCl in order to extract humic acids, fulvic acids and humin. This investigation indicates that conventional humus fractionation does not significantly change the content of different functional groups in soil.
The contribution of lignin to the composition of humic acids from a wheat‐straw amended soil during 3 years of incubation in pots
Authors: AMALFITANO C. , PIGNALOSA V. , AURIEMMA L. , RAMUNNI A. 
Published: July 2006

SUMMARYAn Andisol from the Vesuvian volcanic area, low in organic matter, was treated with wheat straw (20/1 w/w) and urea (500/1 w/w) in pots, and maintained at 60–90% of field capacity in an open greenhouse in order to study the yields and properties of humic acids after 30, 122 and 224 d, and 1, 2 and 3 years of incubation.During the first year the yields increased, but subsequently they showed a decrease. However, the chemical and spectroscopic properties of humic acids remained substantially constant.The chemical characteristics of modified lignin from added wheat straw were recognized in the properties of humic acids by UV‐visible, FT‐IR and 13C CP‐MAS NMR spectroscopic analysis. Evidence was obtained that these modifications included the microbial removal of carbohydrates, the oxidative destruction or transformation of the side chains of lignin units, the demethylation of mainly guaiacyl, and subsequent oxidation of catechol‐like structures to o‐quinone. The latter can be postulated to promote the nucleophilic addition of amino compounds with formation of aromatic amines in humic acids.
Laboratory experiments on surface seal development and its effect on interrill erosion processes
Authors: SLATTERY M. C. , BRYAN R. B. 
Published: July 2006

SUMMARYDespite extensive research, the processes involved in seal and crust formation are not yet fully understood. This paper provides detailed information on the dynamics of surface sealing and its effect on the erosion process. Seal development of an artificial soil mixture was investigated by measuring changes in splash detachment, soil bulk density and near‐surface soil strength, and by detailed observation and analysis of thin‐section photomicrographs taken at different sealing stages.Raindrop impact was found to be the principal force governing the formation of the surface seal. The sequence of seal development was as follows: (i) rapid disruption of surface aggregates by direct raindrop impact; (ii) rearrangement of disrupted fragments and textural separates; and (iii) compaction of surface material by continued drop impact. Eventually, an ‘equilibrium’ complete seal of the surface was established. Other micro‐morphological characteristics included (i) a mean seal thickness of 0.3–0.8 mm, (ii) a complex void structure dominated by compound packing voids and vughs, (iii) an absence of any ‘washing‐in’ of fine material, and (iv) development of miniature soil pedestals (micro‐hoodoos), micro‐depressions and micro‐knolls formed by drop impact. Measured changes in splash detachment and soil bulk density were consistent with the observed fabric changes. Splash detachment increased during the early seal stages but thereafter decreased rapidly with incorporation of material into the developing seal. The decrease was matched by an overall increase in soil bulk density. Contrary to expectations, soil shear increased only during the initial wetting phase, and subsequently decreased to give minimum values coincident with maximum seal development. After the initial wetting phase shear strength had a negative linear relationship with soil moisture content. It is concluded that soil shear strength may not be a reliable indicator of seal development.