bluuebunny/crossref_metadata_2025_split huggingface dataset:
ADSORPTION ON HYDROUS OXIDES: II. OXALATE, BENZOATE AND PHOSPHATE ON GIBBSITE
Authors: PARFITT R. L. , FRASER A. R. , RUSSELL J. D. , FARMER V. C. 
Published: July 2006

SummaryAdsorption isotherms, the infrared spectra of adsorbed species, and the amount of hydroxyl released when oxalate is adsorbed, all indicate that adsorption of oxalate, benzoate and phosphate at low solution concentrations occurs only on A1(OH)(H2 O) sites exposed on edge faces of the platy gibbsite crystals studied. This is confirmed by the finding that the vibrations of surface hydroxyl groups on the principal plate faces are unaffected when excess oxalate is present, and further supported by the low affinity for oxalate of imogolite, a tubular mineral with a very large gibbsite‐like surface, but with a very low concentration of edge sites.Infrared spectra indicate that oxalate is adsorbed in bidentate form. Near neutrality and at low solution concentrations, gibbsite adsorbs more oxalate than does goethite of comparable surface area.
THE MICROMORPHOLOGY OF GIBBSITE FORMS IN SOILS
Authors: ESWARAN H. , STOOPS G. , SYS C. 
Published: July 2006

SummaryUsing optical and scanning electron microscopy various forms of gibbsite are described in some tropical soils. In a lateritic soil from Zaire gibbsite occurs on argillans, in randomly oriented crystal sheets, as nodular aggregates infilling vughs and on ped faces. The mineral also surrounds quartz grains and kaolinite pseudomorphs after biotite. In other soils gibbsite occurs as silt‐size particles disseminated through the matrix, as large nodular aggregates, and as anatomizing sheets associated with crystal chambers. It is clear from these observations that alumina must be a mobile constituent and was probably translocated through the soil in solution.
SURFACE CHEMISTRY OF THE HYDRANDEPTS AND ITS RELATION TO NITRATE ADSORPTION AS AFFECTED BY PROFILE DEPTH AND DEHYDRATION1
Authors: BALASUBRAMANIAN V. , KANEHIRO Y. 
Published: July 2006

SummaryThe pH0 and ZPC of two Hydiandepts were determined by potentiomettic titiation in NaCl and by ion adsorption measurements from NH4NO3, respectively. The decrease of pH, pH0, and ZPC due to drying was explained by the hydrolysis reaction. Partial drying, high organic matter content, and low Al2 O3 concentration in the surface soil were responsible for its low pH, pH0 and ZPC. The high pH0 of subsoils was attributed to the presence of amorphous aluminosilicates and mixed polymeric gels of Fe(III) and A1 with high water content. The significant decrease of nitrate adsorption due to dehydration is discussed in relation to the change in pH, pH0, ZPC, and surface area on drying.
ROTHAMSTED STUDIES OF SOIL STRUCTURE II. MEASUREMENT AND CHARACTERISATION OF MACROPOROSITY BY IMAGE ANALYSIS AND COMPARISON WITH DATA FROM WATER RETENTION MEASUREMENTS
Authors: BULLOCK P. , THOMASSON A. J. 
Published: July 2006

SummaryMacroporosity (>60 μm) in the three pairs of soils described in Part I was measured and characterized by image analyses. There are significant differences in macroporosity between the soils in each pair, particularly in the subsoil horizons. The results show that the Ragdale, Denchworth and Salop soils are more impervious than those of the Hanslope, Evesham and Flint soils.Comparison of the image analysis results with those derived from air content at 0.05 bar suction shows that in most cases macroporosity by the former is larger. In image analysis the maximum diameter of each pore is measured whereas the water retention method measures the diameter of the smallest exit point of each pore. Differences between the two types of measurement will thus be at a maximum in soils containing many large pores with narrow exit necks.
ROTHAMSTED STUDIES OF SOIL STRUCTURE VI.
Authors: NORTH P. F. 
Published: July 2006

SummaryAn ultrasonic method has been used to measure the stability index, σ, for each horizon of six soils. They provided three soil series comparisons: Hanslope‐Ragdale, Evesham‐Denchworth and Flint‐Salop, in which the first‐named series in each pair is ‘rarely problematic’, and the second ‘commonly problematic’ in management.The results for the top soils are presented in terms of the relationship between σ and the concentrations of those soil constituents likely to contribute to stability of aggregates: organic matter, clay, iron and aluminium oxides, and calcium carbonate. Regression analysis indicates significant correlations for all except the iron and aluminium oxide components.For each soil pair, the ultrasonic measures of stability did not reflect soil management experience, either for surface or sub‐soil horizons. In general the commonly problematic soil appeared to have the same if not higher stability than its rarely problematic partner. Ultrasonic measurement of stability to dispersion, whilst indicating possible mechanisms of soil aggregate formation and breakdown, gives little help in identifying soil management potential.
MINERALISABLE ORGANIC NITROGEN IN SOIL FRACTIONATED ACCORDING TO PARTICLE SIZE
Authors: CAMERON R. S. , POSNER A. M. 
Published: July 2006

SummaryA sandy‐loam under wheat‐pasture‐pasture rotation was sampled both after legumeenriched and legumedepleted pasture leys and then fractionated according to particlesize using mainly sedimentation in water. The C/N ratios decreased from 18 to 7 with decreasing particle‐size and were similar for both pasture types, despite ratios of 13 and 31 respectively for organic material collected at the surface of the soil before sampling. Organic matter was most concentrated in fractions having mineral particle‐sizes between 0.3 and 4.0 μm e.s.d.Mineralisation of the N of high C/N fractions was much greater in incubations under waterlogged anaerobic conditions than under aerobic conditions, yet for low C/N fractions, there was little difference.Most of the readily mineralisable soil N resided in fractions of mineral e.s.d. less than 4 μm and much of this was probably recently formed microbial tissue or metabolites. An increasingly greater proportion of the N within size‐fractions was mineralised as the particle size decreased, the increase being greater for aerobic incubations. The proportion of N mineralised in the surface organic material was much greater for legume‐rich than for legume‐poor pasture, but in the soil fractions, a corresponding difference was established only for sand‐sized organic matter.
DESORPTION OF PHOSPHATE FROM GOETHITE
Authors: MADRID L. , POSNER A. M. 
Published: July 2006

SummaryThe reversibility of the adsorption of phosphate on goethite was measured by diluting suspensions of goethite on which phosphate was adsorbed with large volumes of phosphate‐free solution at the same ionic strength. The effect on the reversibility of various adsorption and desorption conditions was studied, particularly pH, temperature, ionic strength and time of reaction.The apparent irreversibility of the adsorption reaction seems to be due to a slow adsorption reaction of part of the phosphate after a very rapid initial adsorption, with a similar behaviour when the phosphate is desorbed. When the total adsorption plus desorption time is long enough, both adsorption and desorption points tend to lie on a single curve which corresponds to the isotherm calculated according to the Stern double‐layer theory.
ADSORPTION OF SELENITE, PHOSPHATE AND SULPHATE ON HYDROUS ALUMINA
Authors: RAJAN S. S. S. 
Published: July 2006

SummarySelenite was adsorbed on a positively charged hydrous alumina at a solution pH of 5.0, and the OH − released and changes in the surface charge were measured. The adsorption isotherm levelled off at high concentrations suggesting a definite adsorption maximum. The OH− released yielded a curvilinear relationship of increasing slope with the selenite adsorbed. The positive charge on the alumina surface was neutralized by the adsorbed selenite and the net charge became close to zero as the adsorption of selenite was near maximum.The molar ratio of the ligands (OH−+ OH2) displaced over selenite adsorbed was more than one at surface saturations of <0.5, but it was approaching one with increasing adsorption of selenite. The results are explained in terms of preferential adsorption of divalent (SeO23−) and monovalent (HSeO−3 selenite on a highly positively and less positively charged surface respectively, in agreement with the VSC− VSP model of Bowden et al. (1973; 1977). The supply of SeO23− for adsorption is considered to be favoured by an expected lower H activity in solution adjacent to the positively charged surface than that in the bulk solution.A general discussion is given on the ligand exchange adsorption of selenite, phosphate and sulphate on hydrous alumina.
USE OF THE DROP‐CONE PENETROMETER ON UNDISTURBED AND REMOULDED SOILS AT A RANGE OF SOIL‐WATER TENSIONS
Authors: MULLINS C. E. , FRASER A. 
Published: July 2006

SummaryDrop‐cone measurements were made on undisturbed and remoulded samples of topand sub‐soil from two sites equilibrated at tensions between zero and 600 kPa (6 bar). All samples remained virtually saturated up to the highest tension. Within a few days after remoulding, cone penetration values had returned to those obtained on undisturbed samples.
THE WATER BALANCE OF AN AGRICULTURAL CATCHMENT III THE WATER BALANCE
Authors: McGOWAN M , WILLIAMS J. B. , MONTEITH J. L. 
Published: July 2006

SummaryThe catchment of the Kingston Brook has an area of 57 km2, mainly under pasture (56%) and arable crops (36%). Changes of soil water content, measured with a neutron probe from April 1969 to March 1973, were analysed to determine evaporation (summer only) and drainage. From measurements of rainfall and runoff, supplemented by Penman estimates of evaporation (in winter), water storage is estimated month by month.Annual mean values (mm) were: rainfall (559), evaporation (398), runoff (157). During the summer, the measured decrease in soil water storage contributed ca 100 mm to evaporation and drainage and there is evidence of delayed recharge (about 30 mm) during the winter. A linear relation between annual rainfall and annual runoff is interpreted in terms of (i) a fixed catchment storage (125 mm); (ii) a small and nearly constant winter evaporation (ca 49mm); (iii) summer evaporation of 125 mm from storage plus a constant fraction (0.57) of contemporary precipitation.Summer evaporation was restricted by the supply of rain in every year from 1969 to 1976. By estimation, 500 mm of summer rain is needed to maintain potential evaporation, and the deficit at which actual evaporation falls below the potential rate was about 40 mm. Replacing the pasture by cereals would increase runoff by about 10% because of the shorter growing season.
THE VOLATILISATION, FROM SOILS AND MIXTURES OF SOIL COMPONENTS, OF IODINE ADDED AS POTASSIUM IODIDE
Authors: WHITEHEAD D. C. 
Published: July 2006

SummaryIodine, as potassium iodide in solution, was added to samples of 24 surface soils, 15 subsoils and 16 mixtures of sand with other materials representing soil components, at 10 μg iodine/g soil. The extent of volatilisation of the added iodine was measured after 30 days' exposure in a well‐ventilated room. With many of the surface soils volatilisation was negligible although with an acid sandy podsol it amounted to 57 per cent of the iodine added. Eleven of the subsoils induced volatilisation amounting to > 10 per cent of that added. With sand alone, having a pH of 5.7, volatilisation amounted to 100 per cent, and with the mixtures it ranged from nil to 100 per cent. Organic matter reduced volatilisation, probably by retaining the iodine in bound form. Montmorillonite, kaolinite and ferric oxide also reduced volatilisation in comparison with sand alone, but had less effect than did organic matter. Calcium carbonate, although in general reducing volatilisation, probably through its influence on pH and hence on retention by other materials, caused no reduction when added to sand alone.
The effect of pH and metal binding on the transport properties of humic acids
Authors: RITCHIE GERALDINE S. P. , POSNER A. M. 
Published: July 2006

SummaryThe molecular weight, shape and size of fractionated humic acids and their metal complexes were determined from sedimentation and diffusion measurements made at various pH values. For all the species studied, the molecular weight and size decreased as the pH became more alkaline. However, the shape of the molecule (approximately spherical) was unaffected by pH. The molecular weight and size of the metal humates depended not only on the type of cation but also on the degree of dissociation ofthe humic acid and the hydrolysis ofthe metal ion.
Eluvial/illuvial coefficients of major elements and the corresponding losses and gains in three soil profiles
Authors: MUIR J. W. , LOGAN J. 
Published: July 2006

SummaryThe major element compositions of three soil profiles from the north‐east of Scotland have been determined and from them losses and gains of major elements have been calculated. Eluvial/illuvial coefficients are also calculated and used to measure the intensities of soil processes. This information forms the basis of a discussion on the development of the profiles. The main process involves the decomposition of minerals, especially in the upper horizons, the loss of constituents to drainage and the translocation ofa few to the lower horizons.
Some fundamental aspects of the formation, stability and failure of mole drainage channels
Authors: SPOOR G. , LEEDS‐HARRISON P. B. , GODWIN R. J. 
Published: July 2006

SummaryThe various stresses are examined which can arise in the vicinity of a mole channel from its formation to ultimate collapse. Possible failure mechanisms contributing to channel collapse or deterioration are proposed, together with the major soil properties associated with them. Supportive evidence for the proposals, obtained from individual laboratory and field experiments, is presented.
Critical potassium potentials for crops: 2. Potentials for wheat, maize, peas, beans and sugar beet in their early growth on a sandy loam
Authors: PAGE M. B. , TALIBUDEEN O. 
Published: July 2006

SummaryWheat, maize, leafless peas, field beans and sugar beet were grown in a constant environment for 4 weeks after germination on a sandy loam containing initially a 70‐fold range of exchangeable K levels. The yield response curves to the mean soil K potential (ΔGK, ca+ Mg) for the growth period for each crop were divided into three linear sections, for positive, zero and negative response, by a numerical iterative method, and from these, exhaustion (Δ Gexh), optimum (ΔGopt) and toxicity (Δ Gtox) K potentials were derived.Values of ΔGexh were similar for all crops. The Δ Gopt values increased in the order legumes < cereals < sugar beet. High potassium potentials which produced decreases in yield were far greater than any likely to be encountered in a natural system. It is suggested that yield reductions at high K potentials were caused by inhibition of the uptake of other cations rather than by toxic levels of K in the plant tissue.At this early growth stage, seed K concentrations and K contents of the crops affected ΔGexh and Δ Gopt values in different ways and to different extents. The influence of the K requirements of the crop and the crop's ability to extract K from the soil are briefly discussed.
Studies of litter and acid insoluble soil organic matter fractions using 13C‐cross polarization nuclear magnetic resonance spectroscopy with magic angle spinning
Authors: WILSON M. A. , HENG S. , GOH K. M. , PUGMIRE R. J. , GRANT D.M. 
Published: July 2006

SummaryCross polarization carbon‐13 nuclear magnetic resonance spectroscopy with magic angle spinning (CP‐MASS) was used to analyse for various forms of carbon in soils, a moss peat, hydrochloric acid insoluble residues from soils and peat, and litter from beech and pine trees. The chemical composition of the litters was also investigated by conventional techniques.The results show that hydrolysis with hydrochloric acid extraction removes nearly all oxygenated alkyl carbon from the soils used. It is shown that humification pathways in which carbohydrates are incorporated into humic substances via nonhydrolysable linkages are not important for the soils investigated in this work.CP‐MASS data suggest that the percentage of aromatic carbon in pine leaves increases with increase in ageing time. The results for the beech leaves are not sharply defined.
Optimal interpolation and isarithmic mapping of soil properties
Authors: McBRATNEY A. B. , WEBSTER R. 
Published: July 2006

SummaryThe principle of optimal estimation using regionalized variable theory is extended from that of a single soil property to situations where there are two or more spatially interdependent ones. Auto and cross semi‐variograms express the spatial relations among the properties concerned. They can be estimated from data and can then be used to interpolate the values of a variable by co‐kriging from measurements of it plus data on one or more other properties that have been more intensively sampled. The technique of co‐kriging is described and illustrated by a case study of the particle size distribution at Woburn experimental farm. There was a strong co‐regionalization with common anisotropy between topsoil silt, subsoil silt and subsoil sand. This allowed topsoil silt to be estimated and mapped by co‐kriging more precisely than by kriging from data on topsoil silt alone.When the auto and cross semi‐variograms for a set of variables are known in advance or estimated from reconnaissance they can be used to plan an optimal sampling scheme. The main variable is sampled on a rectangular grid with finer grids for subsidiary variables. The maximum kriging variances are calculated for a range of sample spacings and relative sampling intensities. Those that match the maximum tolerable variance are potentially useful. The optimum scheme is the one that achieves the desired precision for least cost. For Woburn it is shown that measuring a main variable would need to cost at least 5 times that of a subsidiary variable to make a design for co‐kriging economically sound. Such differences are unlikely for particle size fractions. Nevertheless there are many other instances in soil research where there are large differences in cost. If there is also a strong co‐regionalization then savings should be possible by designing a sampling scheme that takes advantage of co‐kriging.
The structural improvement of damaged clay subsoils
Authors: McGOWAN M. , WELLINGS S. R. , FRY G. J. 
Published: July 2006

SummaryA manually damaged, smeared layer (pan) was created at plough depth in two clay soils. Soil physical properties, soil water regimes and plant responses were measured in panned and non‐panned soil from 1972 to 1975. Continuity of the pan was readily lost on drying by formation of shrinkage cracks which did not fully close unless the soil had been wet for a long time; thus the occurrence of perched water tables above the pan was rare. The pans had no effect on crop yields. Leaf water potential, effective rooting depth and subsoil water deficits all showed that the pans affected water uptake by roots, but these effects were transient. The results indicate that natural amelioration of pans in these clay soils occurs even after slight drying and that the degree but not duration of drying is important.
Multiscale sources of spatial variation in soil. I. The application of fractal concepts to nested levels of soil variation
Authors: BURROUGH P. A. 
Published: July 2006

SummarySoil variation has often been considered to be composed of‘functional’ or ‘systematic’ variation that can be explained, and random variation (‘noise’) that is unresolved. The distinction between systematic variation and noise is entirely scale dependent because increasing the scale of observation almost always reveals structure in the noise. The white noise concept of a normally distributed random function must be replaced to take into account the nested, autocorrelated and scale‐dependent nature of unresolved variations. Fractals are a means of studying these phenomena. The Hausdorff‐Besicovitch dimension D is introduced as a measure of the relative balance between long‐ and short‐range sources of variation; D can be estimated from the slope of a double logarithmic plot of the semivariogram. The family of Brownian linear fractals is introduced as the model of ideal stochastic fractals.Data from published and unpublished soil studies are examined and compared with other environmental data and simulated fractional Brownian series. The soil data are fractals because increasing the scale of observation continues to reveal more and more detail. But soil does not vary exactly as a Brownian fractal because its variation is controlled by many independent processes that can cause abrupt transitions or local second order stationarity. Estimates of D values show that soil data usually have a much higher proportion of short‐range variation than landform or ground water surfaces. The practical implication is that interpolation of soil property values based on observations from single 10 cm auger observations will be unsatisfactory and that some method of bulking or block kriging should be used whenever longrange variations need to be mapped.
A 31P nuclear magnetic resonance study of the phosphorus species in alkali extracts of soils from long‐term field experiments
Authors: HAWKES G. E. , POWLSON D. S. , RANDALL E. W. , TATE K. R. 
Published: July 2006

SUMMARYThe different forms of phosphorus (P) in 0.5 m sodium hydroxide extracts of soils from long‐term field experiments at Rothamsted were characterized by 31P‐nuclear magnetic resonance spectroscopy (NMR).The extract from an old grassland soil (pH 4.6) from a plot of the Park Grass Continuous Hay Experiment that had received no fertilizer or lime for at least 125 years contained the following forms of P: inorganic orthophosphate (22% of the extracted P), orthophosphate monoesters (49%), orthophosphate diesters (14%), phosphonates (3%), pyrophosphate (4%) and two unidentified forms of P (7%). The soil extract from a Park Grass plot given inorganic phosphate fertilizer (35 kg P ha−1) annually for 121 years contained the same forms of P and, in addition, a small amount of polyphosphate. There was also evidence of an increase in the orthophosphate monoester fraction.Another old grassland soil, of pH 6.1, contained more total and organic P than Park Grass but the extract contained fewer forms of P: inorganic orthophosphate (14% of the extracted P), orthophosphate monoesters (39%), orthophosphate diesters (34%) and an unidentified form (13%). An area of this grassland that had been ploughed up 20 years previously, and kept bare since, contained less organic P. The extract contained less of the phosphate diesters but the more stable monoesters remained relatively unchanged.
Soil organic matter maps by nuclear magnetic resonance
Authors: WILSON M. A. 
Published: July 2006

SUMMARYPreliminary studies are reported on a soil and a litter fraction which have the aim of exploring the potential of two‐dimensional 13C nuclear magnetic resonance spectroscopy for the analysis of soil organic matter structure. It has been shown that contour plots can be obtained in which one co‐ordinate gives chemical shift information and the other the magnitude of the dipolar interaction. For aromatic and oxygenated aliphatic carbon, the latter parameter is a measure of the degree of protonation. Hence the method is useful for distinguishing between soils containing highly substituted and condensed aromatic structures and those with protonated aromatic carbon. Likewise, it is possible to distinguish between soils containing dioxygenated carbon which is. protonated (e.g. ketal).