bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fuzzy mathematical methods for soil survey and land evaluation
Authors: BURROUGH P. A. 
Published: July 2006

SUMMARYThe rigid‐data model consisting of discrete, sharply bounded internally uniform entities that is used in hierarchical and relational databases of soil profiles, choropleth soil maps and land evaluation classifications ignores important aspects of reality caused by internal inhomogeneity, short‐range spatial variation, measurement error, complexity and imprecision. Considerable loss of information can occur when data that have been classified according to this model are retrieved or combined using the methods of simple Boolean algebra available in most soil and geographical information systems. Fuzzy set theory, which is a generalization of Boolean algebra to situations where data are modelled by entities whose attributes have zones of gradual transition, rather than sharp boundaries, offers a useful alternative to existing methodology. The basic principles of fuzzy sets, operations on fuzzy sets and the derivation of membership functions according to the Semantic Import Model are explained and illustrated with data from case studies in Venezuela and Kenya.
A rapid method for predicting the lime requirement of acidic temperate soils with widely varying organic matter contents. III. A lime‐quality correction model
Authors: BAILEY J. S. , STEVENS R. J. , KILPATRICK D. J. 
Published: July 2006

SUMMARYA correction factor for lime quality (F), is described, which can be used to convert CaCO3 requirements into recommendations for commercially available liming materials. A model is presented that relates values of F to the properties of both the liming materials and the soils to which the materials are applied. The results of independent tests demonstrate that the model is capable of predicting suitable values of F for a wide variety of different soil‐lime treatments.A procedure is described for estimating the amount of liming material required to adjust the pH in soils with widely varying organic matter contents. The procedure incorporates all the models and relationships developed in this study and appears to provide a more comprehensive method of evaluating the lime requirement of temperate acidic soils than any other method currently available.
Structure of soil carbohydrates resistant to periodate oxidation
Authors: CHESHIRE M. V. , LOMAX J. A. , MUNDIE C. M. 
Published: July 2006

SUMMARYPermethylation has been applied to the polysaccharide in soil, which has been oxidized with 0.2 m NaIO4 and treated with 0.1 m Na2B4O7. The amounts and types of methylated sugar obtained on hydrolysis have been compared with those from unoxidized soil.As well as a number of derivatives corresponding to 1 ‐3 linked glucose, arabinose and xylose, considerable proportions of 1‐4 linked glucose and xylose also persisted. The polysaccharides appear to persist for both chemical and physical reasons.
Electron paramagnetic resonance in humic substances
Authors: GUTSZE A. , PACEK M. , DZIADOWIEC H. 
Published: July 2006

SUMMARYElectron spin resonance (ESR) measurements of soil and its fractions (humic acids, fulvic acids, post‐extraction residues and bitumens) were performed and particular attention given to free radicals of organic origin. For such radicals in soil, two lines with g factors 2.004 and 2.002 were observed. For all four fractions one line was observed. To obtain more information on the radical structure, the samples were carbonized. This allowed the different chemical structures of each of the two organic radicals to be differentiated. However, it was not possible to ascribe any definite structure to these radicals. Heat‐treatment measurements indicated that the humification process shows some similarity to the process of carbonization at low temperature.
Labelled and native sugars in particle‐size fractions from soils incubated with 14C straw for 6 to 18 years
Authors: CHESHIRE M. V. , CHRISTENSEN B. T. , SØRENSEN L. H. 
Published: July 2006

SUMMARYFour soils of different texture (6% to 46% clay and 6% to 32% silt) were incubated with 14C‐labelled barley straw for periods ranging from 16 to 18 years. Incubations were either under laboratory (three soils, 20°C) or field conditions (one soil).Soil samples were separated into clay‐size (< 2 μm), silt‐size (2–20 μm) and sand‐size (20–2000 μm) fractions using ultrasonic dispersion and gravity sedimentation. Whole soils and size fractions were hydrolysed with 12 M sulphuric acid, the released neutral sugars isolated and their amounts and specific activities determined.The proportion of C present as carbohydrate decreased in the order clay, silt and sand, but the sugar compositions of the various fractions were similar. No relationship could be discerned between the soil particle‐size distributions and the persistence of sugars.The specific activity of xylose remained higher than that of any major sugar, indicating the persistence of straw polysaccharides. This was true for all soils and size fractions. Galactose and mannose retained a greater proportion of their initial activity than did arabinose, xylose or glucose. This was ascribed to synthesis of microbial polysaccharides.Total activity present in whole soils decreased in the order glucose, xylose and arabinose, galactose and mannose. The total activity of individual sugars in size fractions decreased in the order clay, silt, sand. The hexose to pentose ratio (galactose+mannose to arabinose + xylose) tended to be higher for silt than for clay, but the trend was not consistent for all soils.
Gel filtration chromatography of humic substances in soil solutions using HPLC‐determination of the molecular weight distribution
Authors: BERDÉN M. , BERGGREN D. 
Published: July 2006

SUMMARYThe molecular weight distribution of humic substances in soil solutions from a dystric cambisol and an orthic podzol were determined by high‐performance gel filtration chromatography (Toyo Soda TSKgel G2000 SWXL column). The retention volumes of humic substances were compared to those of narrow molecular weight distributed poly‐styrenesulphonates with known molecular weight.A change in mobile phase pH or ionic strength usually resulted in an almost identical change in retention volume for the polystyrenesulphonates and the bulk of humic substances. The possibility of using the former to calibrate the column is discussed. The molecular weight at peak maximum was 1120–1190 and 1800 for the cambisol and podzol samples, respectively, using polystyrenesulphonates as molecular weight standards. No pretreatment of samples was used, but ion exchange is recommended for samples with high Al concentrations.
Dual water flow pattern in the unsaturated zone under a gypsum‐amended soil
Authors: GVIRTZMAN H. , MAGARITZ M. , NADLER A. 
Published: July 2006

SUMMARYSediment samples were obtained from boreholes down to c. 20 m in a gypsum‐treated, saline‐water irrigated soil and from nearby uncultivated fields at two locations (Nir Oz and Nahal Oz). Measurements of tritium concentrations in the soil solution enabled the determination of water flow rates in the unsaturated zone. Two types of flow, fast and slow, were identified in the profiles. The slow component, the ‘piston‐flow type’ in the sandy loess section in Nir Oz and in the clayey loess section of Nahal Oz, had a vertical velocity of 0.16 and 0.23 m a−1, respectively. The faster component typically transported the solution through fractures and other preferred paths. The percentage of the slow component in the sandy and in the clayey loess was 40% and 60% respectively. A previous prediction of delayed transport of salts was verified and is related to the interaction between chemical composition of irrigation water and the agro technical practices of gypsum application.
Aspects of transport processes in aggregated soils
Authors: YOUNGS E. G. , LEEDS‐HARRISON P. B. 
Published: July 2006

SUMMARYThe way in which water and solutes move in aggregated soils depends on the mode of saturation of the pore space that is made up of the micropore region within the aggregates and the macropores surrounding them. When both regions are saturated, a hydraulic‐head gradient causes water to flow preferentially in the macropores with little flow within the aggregates, so that movement of solutes into or out of the aggregates is mainly by diffusion caused by the difference between the solute concentrations of the water in the two regions. When macropores full of water surround unsaturated aggregates, water is imbibed by the aggregates giving rise to convective movement of solutes with the moving water. When the macropores are empty, the aggregates become almost isolated so that redistribution of water and solutes occurs only within the aggregates with very little transport of water and solutes between them. The movement of water and solutes in the micropore region within the aggregates can be considered to behave as if in a continuum, and can be described by Darcy's law and the dispersion equation, with boundary conditions imposed by conditions in the macropores.These physical considerations of transport behaviour in aggregated soils can be used to give guidance on soil management practices concerning drainage and leaching.
Incorporation of natural hydrocarbons from plant residues into an hydromorphic humic podzol following afforestation and fertilization
Authors: JAMBU P. , AMBLÈS A. , DINEL H. , SECOUET B. 
Published: July 2006

SUMMARYThe content and composition of natural hydrocarbons from plant residues (Pinus maritima sp.) of a hydromorphic humic podzol were investigated following the addition of NPK and P fertilizers. L and F layers and the A, horizon from non‐fertilized and fertilized soil were analysed for total lipids and hydrocarbons, and non‐linear and linear hydrocarbons. The decrease in non‐linear hydrocarbons extracted following the addition of fertilizers was attributed to the incorporation of non‐linear hydrocarbons into humus, rather than to their biodegradation by soil micro‐organisms. Short‐ and medium‐chain linear hydrocarbons from plant residues or of microbial origin were rapidly biodegraded or fixed by soil micro‐organisms, resulting in a very low concentration in the A, horizon. In contrast, long‐chain linear hydrocarbons of plant origin accumulated in the non‐fertilized soil, while the addition of P fertilizer slightly stimulated their biodegradation. oration is needed before firm conclusions can be drawn.
Factors affecting the strength of undisturbed cores from soils with low structural stability
Authors: YOUNG I. M. , MULLINS C. E. 
Published: July 2006

SUMMARYUndisturbed core samples of two similar sandy clay loam soils (Big Ground and Plum Orchard) were equilibrated at matric potentials of −0.01, −0.1 and −1 MPa and tested for indirect tensile strength (ITS) and unconfined compressive strength (UCS). Rate of deformation was found to have significant and large effects on the measured ITS and UCS. In general, both ITS and UCS increased with increasing deformation rates although, particularly for UCS tests, the effect was variable. For ITS, the effect of rate of deformation was attributed to water having insufficient time to move towards any incipient failure plane. For UCS, the effect of rate of deformation was partly attributed to loss of moisture during loading, since samples strained at lower deformation rates generally had lower moisture contents; and partly to the different modes of failure seen. ITS and UCS of Big Ground were invariably higher than those of Plum Orchard at all matric potentials. This was attributed to Big Ground having been under an intensive management system for approximately 10 years longer than Plum Orchard.Simple pretreatment effects are also considered. In a comparison of measured and theoretically predicted ITS and UCS, theory provided good estimates of measured strengths of samples equilibrated at −0.1 MPa, although samples were considerably weaker than theoretically predicted at −1 MPa.
Aluminium contamination of acid soil solution isolated by means of porcelain suction cups: a reply to a paper by Hughes & Reynolds (1990) and an interpretation of aluminium release
Authors: RAULUND‐RASMUSSEN K. 
Published: July 2006

SUMMARYPossible aluminium contamination of acid soil solutions isolated by use of porous porcelain suction cups (‘P.80 type’) was reported by Raulund‐Rasmussen (1989). The aluminium release was explained by a proton‐induced dissolution of cup material. Hughes & Reynolds (1990) suggested that the aluminium release and proton consumption could be explained by an ion‐exchange reaction. In an attempt to understand the mechanism and thereby also the usefulness of suction cups, laboratory experiments were carried out to define mineralogical and chemical composition, stability under acid conditions, cation exchange capacity, and reactivity under conditions relevant to the field.The cups consisted of mullite and corundum (65% Al2O3) as shown by X‐ray diffraction analysis. The cation exchange capacity of the cups was too low (0.65 μmolc per cup) to explain the observed contamination of isolated soil solution. Ground cup material dissolved slowly in acid. Investigations on whole cups showed that aluminium release to acid test solutions depended on the time of exposure. It is concluded that porcelain suction cups may lead to contamination of isolated soil solution depending on: (i) the intake rate, (ii) the rinsing procedure before sampling, and (iii) the composition of the soil solution (pH and aluminium ion activity being important parameters).
Nitrous oxide production and denitrification in Scottish arable soils
Authors: ARAH J. R. M. , SMITH K. A. , CRICHTON I. J. , LI H. S. 
Published: July 2006

SUMMARYNitrous oxide (N2O) emissions and concentrations in the soil atmosphere were measured at a number of sites of differing soil type in south‐east Scotland between 1985 and 1988. Concentrations followed log‐normal distributions and were significantly affected by soil type, tillage treatment, and nitrate application rate. The shape of the profiles suggested significant consumption in the upper 5 cm, making calculations of emission rates using Fick's Law unsatisfactory. Emission rates measured using closed flux chambers were at least one order of magnitude smaller from heavier‐textured arable soils than from lighter ones.Denitrification fluxes measured by field application of the acetylene inhibition technique were lowest in a clay loam, and highest in an alluvial sandy loam; this was attributed to a failure to achieve a satisfactory distribution of acetylene in the heavier soil. Denitrification rates in soil cores generally exceeded measured surface fluxes; incubation at decreased oxygen concentrations typical of those measured in the field produced a further significant increase. Core incubation should be used as an alternative to in situ field measurement only if the oxygen concentration in the incubation vessels is adjusted to mimic that in the field; otherwise denitrification rates may be significantly underestimated.
Poorly ordered hydrous Fe oxides, colloidal dispersion and soil aggregation. II. Modification of silty soil aggregation with Fe(III) polycations and model humic macromolecules
Authors: BARTOLI F. , PHILIPPY R. , BURTIN G. 
Published: July 2006

SUMMARYPoorly ordered ferrihydrites, more or less associated with synthetic humic macro‐molecules, were added to a poorly structured temperate silty soil. Manipulation of the net soil charge through these additions was measured by potentiometric titration and cation exchange capacity. The consequences of anchoring positively charged Fe hydrous oxides on negative permanent clay surface charges were studied. Both cementation and aggregate water‐stability increased with increase in adsorbed iron. The aggregation process was studied by using micromorphology and ultramicromorphology, water retention curves, mercury porosimetry and a fractal approach. Aggregate water‐stability was studied when the soils were air‐dried, with some irreversible aggregation, and oven‐dried or wetted from – 1.5 MPa to – 1 kPa thereafter. Soils with added Fe(III) polycation–humic macro‐molecule associations were less positively charged, less cemented and less stable than soils amended with Fe(III) polycations alone. The effect of these treatments on slaking is discussed.
The effect of time on the competition between anions for sorption
Authors: BARROW N. J. 
Published: July 2006

SUMMARYSolutions of phosphate and of selenite were gently mixed with a soil, both separately and in combination, for periods ranging from 15 min to 30 days. For both anions, the solution concentration continued to decrease throughout the period, but the decrease was more marked for phosphate. Competitive effects were smallest after brief periods of mixing, and increased with time. Phosphate was a more effective competitor for sorption than selenite, and its competitive advantage increased with time.The observed effects were closely described by a mechanistic model. According to the model, competition was largely through changes in the electric potential of the surface rather than through decreases in the number of vacant adsorption sites. This explained why competition effects were initially small. This was especially so for phosphate, which was modelled as having a marked continuing diffusive penetration of the surface. The decrease in electric potential associated with that penetration decreased the surface concentration of selenite and so decreased the rate of penetration of selenite. By the end of the experiment this was the most important aspect of the competitive effect of phosphate on selenite.
Comparison of different models for phosphate sorption as a function of the iron and aluminium oxides of soils
Authors: FREESE D. , van der ZEE S. E. A. T. M. , van RIEMSDIJK W. H. 
Published: July 2006

SUMMARYPhosphate sorption on topsoil and subsoil samples from different soils located in the eastern part of Germany was studied. Two models were fitted to sorption data obtained after 4 and 40 d of gentle shaking. The models differ with respect to the fractions of iron and aluminium (hydr)oxides that are considered and whether the phosphate initially sorbed in the soil is taken into zccount. Oxalate‐extractable P, (Pox), appears to be a major part of the total soil P. The total P sorption measured, F, was predominantly related to the amounts of amorphous iron (Feox) and aluminium (Alox). A significant relation between crystalline iron (Fed– Feox) and total P sorption was not found. Reversibly adsorbed phosphate (Pi), measured after 40 d reaction time, was a function of clay content and content of amorphous iron and aluminium (hydr)oxides.
Microbial contribution to sulphate mobilization after liming an acid forest soil
Authors: MARSCHNER B. 
Published: July 2006

SUMMARYSulphate release from unsterilized and γ‐irradiation sterilized soil samples was studied in leaching funnels over a 22‐week incubation period. In unsterilized soil samples, lime addition to the acid forest topsoil caused an immediate increase in extractable sulphate, but enhanced sulphate release rates were detectable only during the first 4 weeks of incubation. Soil samples from an adjacent five‐year‐old limed plot displayed significantly higher sulphate release rates than the control throughout the experiment. The cumulative amount of sulphate extracted from the unsterilized treatments was modelled with parabolic functions and reached 4.6%, 6.8% and 8.2% of the initial total S‐contents of the control, the lime treatment and limed plot respectively. Mineral‐N release was also greatest in the samples from the old limed plot while fresh lime additions reduced net N‐mineralization due to microbial immobilization. In the sterilized samples, γ‐irradiation initially caused an increase in extractable sulphate and ammonium which is mainly attributed to the destruction of microbial biomass. After the second week, no further differences in extractable sulphate were detectable between the treatments. After 22 weeks, between 7 and 9 mg SO42− ‐S kg−1 soil was released from the sterilized samples which was 25–50% of the respective amounts in the unsterilized samples. A similar relationship was found for N. The data indicate that even 5 years after lime addition the observed increased sulphate concentrations in the soil solution can be attributed to enhanced microbial activity.
A modified biometer flask for the measurement of mineralization of 14C‐labelled compounds in soil
Authors: HAIGH S. D. 
Published: July 2006

SUMMARYThe Organisation for Economic Cooperation and Development (OECD)‐recommended biometer flask (OECD Guideline 304A) was modified to allow rapid and accurate sampling of large numbers of flasks during long‐term soil biodegradation experiments. Use of the OECD flask involves tedious manipulation each time the flasks are sampled. The transfer of alkali to and from the side‐arm reservoir, followed by dilution, is open to operator error and is time consuming. The new flask was found to give comparable or higher recoveries of CO2 compared to the OECD‐recommended apparatus whilst minimizing the manipulation of 14C‐loaded alkali. By avoiding dilution of the alkali trap, the sensitivity of the test is increased by an order of magnitude and the sampling time is reduced by two‐thirds.
Estimation of the diffusion coefficients of adsorbed and non‐adsorbed solutes in soil
Authors: COLLIS‐GEORGE N. , GEERING H. R. 
Published: July 2006

SUMMARYA method is proposed which follows Darrah's experimental procedure and takes advantage of a mathematical solution provided by Carslaw & Jaeger to estimate the diffusion coefficients of adsorbed and non‐adsorbed solutes in soil.The method requires only the values of the concentration of the solute at the input face of a uniform column of soil, Cs, and of the total amount, Qt, that has entered the soil after a specified time during which the surface of the block is in contact with a thin porous pad containing a known initial amount of solute, Q0, at concentration C0, expressed in the same units as Cs. In the Cs/C0 vs. Qt/Q0 space there is a unique relationship between the effective diffusion coefficient, De, of the solute in the soil and the contact conductance for this solute, h, between the pad and the soil surface.The proposed procedure is firstly to determine De, and h for a non‐adsorbed solute in the experimental soil using the experimental values of Cs/C0 and Q/Q for that solute. This value of De, gives the diffusion impedance factor for the solute in the soil, f, which is assumed also to apply to adsorbed solutes. A first estimate of the effective diffusion coefficient of an adsorbed solute, 1Dea, is then made using f and the diffusion coefficient of the free solute in water, DL, obtained from the literature (i.e. 1Dea= DLf). Only if the solute is weakly adsorbed will the values of Cs/C0, and Qt/Q0 lie in Cs/C0, vs. Qt/Q0, space as defined by 1Dea and the contact conductance, h. Instead a second space relating Cs/C0 and Qt/Q0, is now constructed from nominated values of h and De, where De, is defined in terms of 1Dea, the adsorption coefficient, F, and the volumetric moisture content of the soil, θ. The position of the experimental values of Cs/C0, and Qt/Q0 within this new space defines h and the actual De, and F of the solute as it diffuses and is adsorbed in the soil.The advantages and limitations of the method are discussed. In particular, the method assumes that the adsorption process is linear and reversible.