bluuebunny/crossref_metadata_2025 huggingface dataset:
A VISUAL RECORD OF THE DECOMPOSITION OF 14C‐LABELLED FRAGMENTS OF GRASSES AND RYE ADDED TO SOIL
Authors: GROSSBARD ERNA
Published: July 2006

The decomposition of grasses and rye labelled with 14C was studied using ground material and also fragments cut from intact leaves or roots either placed on the soil surface or buried in the soil incubated under various conditions. Autoradiography was used to observe the changes in the decaying plant tissue with a minimum of disturbance. Autoradiograms prepared before incubation and subsequently at intervals reveal an over‐all fall in density of the images, a complete disappearance of 14C in small discrete sites, as well as a dispersion of 14C over distances of several cm from the plant residues.

A photoelectric technique was devised by which changes in density could be expressed quantitatively. The log density of autoradiographic images of pellets of ground grasses shows a predominantly, though not completely, linear regression on time of incubation. The method has shown that the process of decomposition is very slow, that in the first stages of decomposition ryegrass decays faster than cocksfoot, and that ground material tends to behave in a different manner to fragments cut from intact tissues. Changes in the area of autoradiographic images with time of incubation could be used as an additional but less sensitive measure of the rate of decomposition.

The participation of micro‐organisms (especially fungi) in the breakdown of the plant tissues has been demonstrated by the presence of labelled organisms in the vicinity of plant residues. Labelled fungi are more numerous in the first 3 months of incubation, during which a marked fall in image density of the plant residues occurs. A further decrease in image density is frequently associated with the appearance of fungal resting structures with a greater concentration of 14C than the surrounding plant fragments. Because of their longevity these structures contribute to the fixing of 14C in a different fraction of the biomass. Faecal pellets of soil mesofauna also concentrate 14C and resist decomposition for very long periods of time.
PHOSPHORUS TRANSFORMATIONS IN A CHRONOSEQUENCE OF SOILS DEVELOPED ON WIND‐BLOWN SAND IN NEW ZEALAND
Authors: SYERS J. K. , WALKER T. W.
Published: July 2006

The rate of loss of total P and accumulation of organic P were investigated in a chronosequence of weakly weathered soils developed on wind‐blown sand. The net loss of total P during 10 000 years of soil development was 1910 kg/ha m profile. This calculation assumes a constancy in the total P content of the parent material. An approximately straight‐line plot was obtained for the loss of total P between 500 and 10 000 years. The organic P content of the beach sands was very low but increased rapidly in the early stages of soil development. With increasing time, the rate of accumulation of organic P decreased. The net accumulation of organic P during 10 000 years was 1050 kg/ha m profile. A slow rate of formation of organic P, coupled with a rapid mineralization, has probably limited organic P build‐up. It is suggested that loss of phosphorus by leaching is a consequence of the low phosphate retention capacity of these weakly weathered soils.
THE NATURE AND GENESIS OF CERTAIN ARIDISOLS IN KENYA
Authors: MAKIN J. , SCHILSTRA J. , THEISEN A. A.
Published: July 2006

In the semi‐arid Kenya lowlands, strongly contrasting soil units associated with specific positions in the landscape have developed on various ancient alluvial deposits. The soil pattern may be explained by the differential truncation of a previously solodized plateau. These contrasting soil sequences give rise to associated vegetation catenas.

Necessary adaptations are applied to the 7th Approximation soil classification, thereby introducing one new Great Group (Halorthid) and several new subgroups (natric grumustert, natric grumaquert, and typic halorthid).
A VERSATILE METHOD FOR TREATMENT OF CLAY SOILS FOR THIN‐SECTION FABRIC STUDIES
Authors: SINGH R. B.
Published: July 2006

In an earlier investigation three different methods had to be used for the treatment of laboratory‐compacted clay soils prior to the preparation of thin sections for use in fabric studies. The three methods, viz., the Carbowax method, the Araldite‐resin impregnation method, and the Aquax method, had limited application depending on the degree of saturation and the clay‐mineral composition of the soil. A new method has been developed which can be applied to all clay soils irrespective of their mineralogy and degree of saturation. In this method, the pore water of the soil specimen is first replaced with monostyrene using a two‐step diffusion process. Then the specimen is impregnated with an Araldite‐resin mixture which can be cured at a temperature of 55°C. The method has yielded better thin sections than those obtained by any of the three previous methods. Pure montmorillonite soils can be treated with a greater degree of success than hitherto possible.
APPARENT AND PARTIAL MOLAL VOLUMES OF CATION‐SATURATED KAOLINS
Authors: HELMY A. K. , ASSAAD F. F. , HASSAN M. NAGUIB , SADEK H.
Published: July 2006

Apparent and partial molal volumes of K‐kaolin and K2SO4, Mg‐kaolin and MgSO4, and Ca‐kaolin and CaCl2 as a function of electrolyte and particle concentration were determined from density measurements at 30°C. The apparent (ø) and partial molal volumes (V) of the kaolin or the salts studied increase with concentration and are larger in salt‐clay mixtures. Kaolin saturated with electro‐strictive cations has lower volumes than that saturated with less strictive ones.
THE DETERMINATION OF THE SURFACE AREA OF SEPIOLITE FROM CARBON DIOXIDE ADSORPTION ISOTHERMS
Authors: DANDY A. J.
Published: July 2006

Sepiolite has a microporous structure the pores of which may be penetrated to differing extents by molecules of different gases. A study has been made of the adsorption of CO2 on outgassed sepiolite (from Amboseli, Tanzania) at 193°, 209·7°, 273·2°, and 298·2 °K using a gravimetric method. Values of the surface area of sepiolite were calculated from BET (Brunauer, Emmett, and Teller) and Kaganer plots of results, assuming molecular areas for CO2 based on extrapolated liquid densities. There were only relatively small deviations from a mean value of 279 m2/g. However, the values were much lower than those previously determined by adsorption of N2 and of other gases.

It is suggested that CO2 adsorbed at these temperatures should be assumed to be in the liquid state, but that the usual method of calculating the molecular areas of adsorbed CO2 from the liquid densities at these temperatures yields values which are too low. Molecular areas of 20·8 Å2 at 193 °K and 23·4 Å2 at 209·7 °K are preferred.

Isosteric heats of adsorption at different coverages were calculated from the isotherms. The results indicated heterogeneity of the surface, with decreases in the values of the heat of adsorption occurring at low coverages and in the‘monolayer region’. They compare well with values calculated from the BET equation.
TRACE‐ELEMENT CONTAMINATION OF PARKLANDS IN URBAN AREAS
Authors: PURVES D. , MACKENZIE E. JEAN
Published: July 2006

Evidence is presented that soils in urban parklands are markedly contaminated with Cu, B, Pb, and Zn. Herbage from the same areas contains significantly higher levels of Pb and Zn than herbage from permanent pastures in rural areas.
SEPARATION OF THE LIGHT FRACTION FROM SOILS BY ULTRASONIC DISPERSION IN HALOGENATED HYDROCARBONS CONTAINING A SURFACTANT
Authors: FORD G. W. , GREENLAND D. J. , OADES J. M.
Published: July 2006

Partially humified material can be separated from other soil material by flotation on a bromoform‐petroleum spirit mixture of density 2·0 g cm‐3. Maximum recovery of partially humified material requires ultrasonic dispersion and the addition of a surfactant to the suspension. For large‐scale work‘Nemagon’ may be used in place of the bromoform‐petroleum spirit mixture.
PHOSPHORUS TRANSFORMATIONS IN A CHRONOSEQUENCE OF SOILS DEVELOPED ON WIND‐BLOWN SAND IN NEW ZEALAND
Authors: SYERS J. K. , WALKER T. W.
Published: July 2006

The rate of transformation of inorganic phosphorus fractions and forms was investigated in a chronosequence of weakly weathered soils developed on windblown sand. The net decline of acid‐extractable Ca‐P during 104 years of soil development was approximately 2600 kg/ha m profile. This fraction was progressively removed from surface horizons and had virtually disappeared from the oldest soil. Residual inorganic P, considered to be included apatite which is not extracted by 0·5 and 1N HC1, was relatively constant in profiles of the chronosequence but decreased in the oldest soil. In the younger soils, the NH4F‐P fraction was low but, with increasing time, the weight of this fraction increased, initially in surface horizons. The net accumulation of non‐occluded secondary inorganic P during 104 years was 360 kg/ha m profile and this was largely due to an increase in the NH4F‐P, rather than the 1st NaOH‐P fraction. There was no net shift from non‐occluded to occluded secondary inorganic P. Although apatite is initially present as inclusions within primary minerals in the wind‐blown sand, an extensive loss of P has occurred during 104 years.
A RAPID METHOD FOR DETERMINING THE SURFACE AREA OF ALUMINOSILICATES FROM THE ADSORPTION DYNAMICS OF ETHYLENE GLYCOL VAPOUR
Authors: RAWSON R. A. G.
Published: July 2006

A new method is described for determining the surface area of soils and clays by adsorbing ethylene glycol vapour under continuous evacuation at c. 10‐2 cm of mercury. The adsorption of a monolayer of ethylene glycol is inferred from the dynamics of pressure changes in the adsorption chamber. The time at which monolayer adsorption is evaluated is proportional to the total weight of ethylene glycol required to form a monolayer on all samples in the adsorption chamber. This period ranged from 30 to 75 minutes when from 0·39 to 1·56 g of glycol was adsorbed in the experiments. A single 0·75 g sample of Wyoming bentonite required 0·195 & glycol.
ACIDIC PROPERTIES OF PLANT LIGNINS AND HUMIC MATERIALS OF SOILS
Authors: THOMPSON S. O. , CHESTERS G.
Published: July 2006

The acidic properties of lignins from the native vegetation of a virgin Ella loamy sand and the humic acids, the 1, 4‐dioxane extractable humic fraction and residual humic acids from the virgin and cultivated soils were investigated by determining solid‐state cation exchange capacities for Cu and Ca and by non‐aqueous potentiometric titration, using potassium methoxide in a benzene‐methanol mixture as titrant. The lignins and soil dioxane extracts were titrated in pyridine; the humic acids in dimethylformamide. Platinized Pt and CH3OH modified calomel electrodes formed the electrode combination.

The CEC of the humic acids were much higher than the CEC of lignins with both cations but the Cu: Ca absorption ratios were less for humic acids than for lignins. Titration curves of lignins showed two potential breaks with total acidities of 960 to 1,190 me/100 g. Titration curves of the humic acids showed three to six potential breaks while curves of the soil dioxane extracts showed three and four. The total acidities of the two types of humic isolates were 1,100‐1,200 me/100 g. The equivalent weights of most lignins and humic materials were very similar although the acid groups might be different with respect to types and acid strength. Lignins from other plant materials and humic isolates from other soils were also investigated by non‐aqueous titration to determine the general applicability of the results obtained with isolates from the Ella soils.
THE MEASUREMENT AND MECHANISM OF ION DIFFUSION IN SOILS
Authors: VAIDYANATHAN L. V. , NYE P. H.
Published: July 2006

Diffusion coefficients of soil phosphate calculated from flux to chloride form of anion‐exchange resin‐paper, assuming total depletion of the labile pool at the boundary, were too small and unrealistic. Thus not all the phosphate in the labile pool contributed to the diffusion process while being desorbed at constant pH in the presence of an indifferent anion—Cl—from the resin‐paper. Desorption relationships under these conditions, using CaCl2 at atmospheric CO2 pressure, were markedly different from the relationship between the long‐term 32P‐exchangeable phosphate and the corresponding pore‐solution concentrations. In the same soil containing different amounts of labile phosphate, a different desorption relationship was found for each phosphate level.

The constant proportionality between amount of phosphate diffusing into resin‐paper and square root of time was indicative of a constant concentration at the boundary. The resin‐paper: soil system was therefore considered as an infinite composite medium in which diffusion through both resin‐paper and soil were rate‐limiting. The constant boundary concentrations were estimated by the use of the diffusion coefficients in the resin‐paper, the phosphate adsorption isotherm for the resin‐paper and the desorption relationship for each phosphate level in the soil.

Diffusion coefficients, calculated using the boundary concentration appropriate to each phosphate level, were related to the slopes of the corresponding desorption relationships, resulting in values of the impedance factor similar to those found for K diffusion under similar conditions.

The resin‐paper method, however, does not provide an accurate enough measure of the diffusion coefficient of soil phosphate to be of any practical use. Until better and simpler methods are found, the diffusion coefficient may be calculated using the slopes of the desorption relationship and the separately determined value of the impedance factor.
THERMODYNAMICS AND THERMOCHEMISTRY OF THE EXCHANGE REACTION BETWEEN NH4+ AND Mn2+ IN A MONTMORILLONITE CLAY
Authors: GILBERT M. , VAN BLADEL R.
Published: July 2006

The exchange reaction between NH4+ and Mn3+ was studied on a montmorillonite clay at several temperatures and different ionic strengths.

Manganese was preferred to ammonium; this preference increased with the temperature and dilution of the dialysate. Comparison with published data concerning exchanges involving NH4+ and the alkaline‐earths showed that in the sequence of increasing selectivity: Mg2+ < Ca2+ < Sr2+ < Ba2+, Mn2+ lies between Mg2+ and Ca2+. The enthalpy change was measured calorimetrically and calculated by application of the van't Hoff law to the temperature coefficient of the equilibrium constants. Both values were in good agreement. The excellent recoveries of Mn2+ at the end of the exchange reaction and the constancy of the cation exchange capacity over the whole range of surface composition ruled out the possibility of significant adsorption in the MnOH+ form. The behaviour of manganese was very similar to that of the alkaline‐earth cations.
SEASONAL PATTERN OF WATER‐SOLUBLE CONSTITUENTS FROM LEAVES OF POPULUS×‘NORTHWEST’ (HORT.)
Authors: DORMAAR J. F.
Published: July 2006

Aqueous leaf extracts were obtained at regular intervals during the 1967 growing season from Populus×‘Northwest’ (Hort.). After lyophilization the samples were analysed for acidity and ash, sugar, phenol, and N contents. They were examined with thin‐layer chromatography and infra‐red spectroscopy.

Simple phenolic compounds, present earlier in the growing season, made way for more complex phenols as the season progressed, and the extracted material became more acid. The increased loss of phenolic compounds and acids from the leaves toward the end of the summer continued during their first autumn on the ground. The polysaccharide content decreased during the season. The infra‐red spectra of the lyophilized material were useful in making comparisons. It was concluded that, for percolation and transformation studies of Chemozemic soils, aqueous leaf extracts obtained during late summer or autumn should be the most relevant.
THE ASSOCIATION OF VANADIUM AND MOLYBDENUM WITH IRON OXIDES IN SOILS
Authors: TAYLOR R. M. , GILES J. B.
Published: July 2006

High concentrations of V and Mo in ironstone gravels have previously been reported. Examination of soils in which ironstone concretions have formed during pedogenesis indicates that Mo/Fe ratios are in fact higher in the finer fractions than in these gravels, whereas the V/Fe ratios tend to be independent of particle size. In the lateritic podzolic soils examined, the observed association between V and Fe in the iron oxides of the fine earth fraction (< 2 mm) is maintained during any solution of this fraction and any subsequent transportation and precipitation involved in the development of the gravels.

Differences in the degree of association with Fe shown by Mo and V are considered to be due to different modes of transport of these elements through the soil. It is suggested that V moves as a vanadyl cation whereas Mo is transported as a complex anion.
QUANTITATIVE PEDOLOGICAL STUDIES ON SOILS DERIVED FROM SILURIAN MUDSTONES
Authors: STEWART V. I. , ADAMS W. A. , ABDULLA H. H.
Published: July 2006

The soils in Cwmcadian, Merionethshire, have developed in uniform Silurian mudstones. This rock consists of fundamental primary particles of silt and clay size. These are released on weathering in the same ratio as they occur in the rock. Because of the simple mode of weathering, silt may be used as an internal standard against which to assess gains and losses of mobile soil constituents during pedogenesis.
A SEMI‐QUANTITATIVE HYDROLOGICAL CLASSIFICATION OF SOILS IN NORTH‐EAST ENGLAND
Authors: EDMONDS D. T. , PAINTER R. B. , ASHLEY G. D.
Published: July 2006

Multiple regression equations relating the times‐to‐peak of flood hydrographs on twenty‐six rivers in NE. England with the characteristics of causative rainfall and those of the relevant river basin, showed flood‐wave formation to be largely dependent on storm duration and the average, minimum, infiltration rate of the soil. Other significant factors were the initial flow in the river, temporal variation of rainfall during a storm, and main river channel length and slope.
THE ORIGIN AND DISTRIBUTION OF HYDROCARBONS IN AN UPLAND MOORLAND SOIL AND UNDERLYING SHALE
Authors: JONES J. G.
Published: July 2006

Investigations of plant and soil lipids at an upland moorland site revealed certain similarities in composition. In all lipid samples the polar compound fraction was the largest and the paraffinic the smallest. The range (C16–36) and pattern of alkanes in the soil were also similar to those of the surface vegetation, both demonstrating a definite predominance of Codd components. A slight peak in the alkanes identified was seen in the region C27–C30. The pattern of alkanes in the water running into the soil was quite different, and was not seen to influence the spectrum detected in the soil. Incubation of soil samples with and without added succinate, although causing a drop in lipid content, did not produce many significant changes in the soil alkanes. Plant‐derived alkanes in the soil appeared to be resistant to microbial alteration under the experimental conditions employed. The origin of alkanes in an ancient sediment, the underlying shale, was not so clear since the carbon preference index was around unity. It seemed possible that microbial activity might have altered the spectrum of alkanes in the sediment during ageing.
A COMPARATIVE STUDY OF NUMERICAL CLASSIFICATION AND ORDINATION OF SOIL PROFILES IN A LOCALITY NEAR OXFORD
Authors: DE LA C. H. E. CUANALO , WEBSTER R.
Published: July 2006

Data for 85 soil profiles, located at random within 17 physiographic units in a 1,000 km2 area near Oxford, and each characterized by 37 properties, were analysed by two sets of multivariate techniques. Principal component analysis yielded two components accounting for 44 per cent of the total variation, and the distribution of the profiles along these components is plotted as a scatter diagram (ordination). Similarity analysis and hierarchical grouping (classification) were performed using three different similarity indices, two different standardization techniques, and three different sorting strategies. Before analysis the profiles were classified by two pedologists, independently using their judgement.

For the Brown Earths there was moderately good agreement between the results of the two prior classifications and between them and those produced by the several numerical procedures. The degree of clustering was slight and much less than imagined prior to analysis. For the Gleys there was no evident clustering. Different numerical procedures gave different results, as also did the two prior classifications. Pedologists faced with difficult classificatory decisions cannot look to any hierarchical clustering strategy as arbiter, though they should get guidance from a principal component plot.
AGEING OF PHOSPHATE ADDED TO SOIL
Authors: LARSEN S. , WIDDOWSON A. E.
Published: July 2006

The ageing of phosphate added to suspensions of a calcareous soil was measured in terms of the solubility of the phosphate and the amount of isotopically exchangeable phosphate (E value). These both showed a decrease in reactivity of the added phosphate during a period of 5 months. A constant ratio of E values after 24 and 500 hours showed that no redistribution within different fractions of labile phosphate occurred.
THE MOBILIZATION OF IRON BY EXTRACTS OF EUCALYPTUS LEAF LITTER
Authors: ELLIS R. C.
Published: July 2006

When aqueous extracts of leaf litter from four closely related Eucalyptus species were reacted with soil material under aerobic conditions their iron mobilizing activity was found to be inversely related to the productivity of the sites on which the species grew. The activity of litter extracts of the four species grown in similar soils in the field was found to increase in the order E. regnans, E. obliqua, E. radiata, E. sieberiana. The results indicate that species‐soil interactions could be as important as inherent species characteristics in determining whether or not a species is a ‘podzol former’.

The effect on the activity of the extracts of altering their pH before reaction with either soil or with prepared iron oxides suggests that, whereas organic acids could be mainly responsible for mobilizing iron from soil and from anhydrous ferric oxide, polyphenols could be more important than organic acids in mobilizing iron from hydrous ferric oxide.

The pH and Eh curves obtained when litter extracts were titrated with a ferric chloride solution showed that iron from this source was strongly reduced by the extracts at low pH.
THE APPLICATION OF MULTIVARIATE ANALYSIS TO SOIL STUDIES
Authors: NORRIS J. M.
Published: July 2006

The assumption that the variation of soil can be characterized by the variation of a set of relatively few soil properties is examined. Different sets of properties describing the same soil profiles, in particular those measured in the field, and those measured in the laboratory, are used to group these profiles by principal components analysis. This numerical method is used so that each set is grouped by exactly the same procedure. Data from the Riverina plains of New South Wales and some Cotswold (Gloucestershire) beechwoods are examined in this way and a close correspondence found between grouping based on field and laboratory data separately. The results cannot be generalized, though the method is suitable for any area. In particular, the results are unlikely to hold if comparisons are made between single properties.
EFFECTS OF TEMPERATURE ON THE MEASURED CATION‐EXCHANGE CAPACITIES OF ANDO SOILS
Authors: WADA KOJI , HARADA YASUO
Published: July 2006

The CEC was measured by a method which eliminates washing for removal of excess saturating salt. The effect of temperature on the CEC of soils and clays varied and depended on their major cation‐exchange materials; the ratio of the CEC measured at 10–20 °C to that measured at 50–60 °C was 0.36 to 0.59 for allophane, imogolite, and/or humus, 0.62 to 0.75 for kaolin minerals, and 0.90 to 0.99 for montmorillonites. The CEC, increased at higher temperature in a neutral n acetate solution, was only partly reduced by lowering the temperature again. There was no evidence for an acceleration of cation diffusion with increasing temperature. A structural alteration in which some ‘bound’ functional groups are set free for ionization is proposed as a major cause of the large CEC increase observed for Ando soils at higher temperature.
SOME EFFECTS OF PARTIAL STERILIZATION ON MINERAL NITROGEN IN A LIGHT SOIL
Authors: DRAYCOTT A. P. , LAST P. J.
Published: July 2006

Field plots on loamy sand with and without the soil fumigant ‘D‐D’ (dichloropropane‐dichloropropene mixture) were sampled at 0–12, 12–24, and 24–64 cm depths during May 1966–8. All plots received 125 kg/ha nitrogen fertilizer early in March each year and were cropped with sugar beet. Fumigation increased the total amount of mineral (NH4++ NO3−) nitrogen to a depth of 64 cm by 67 kg/ha on average, largely by increasing NH4+‐nitrogen. In unfumigated plots some mineral nitrogen leached below 12 cm every year but there was at least 125 kg/ha in the surface 64 cm in 1966 and 1968; during the wet spring of 1967 much leached below 64 cm. Sequential sampling in 1968 confirmed that some of the fertilizer nitrogen moved down the profile during spring.

Plots partially sterilized either one or two years previously and not again, contained the same quantity of mineral nitrogen as plots that had never been fumigated. Fumigation increased the mineral nitrogen in plots by a similar amount whether or not they had been fumigated previously. Thus, on this soil, partial sterilization with ‘D‐D’ seemed to have little residual effect on mineral nitrogen.
A STATISTICAL EVALUATION OF THE INTER‐RELATIONSHIPS BETWEEN PARTICLE‐SIZE FRACTIONS, FREE IRON OXIDE, AND TRACE ELEMENTS1
Authors: PRABHAKARAN NAIR K. P. , COTTENIE A.
Published: July 2006

A statistical approach was adopted to study the association between particle‐size fractions and trace elements in soil, because conventional studies on the subject usually involve chemical methods of fractionation, which may lead to loss and upsets in natural distribution patterns. The results showed that both total and extractable contents of Zn, Al, Cu, Mn, Pb, and Fe are bound up either in clay or silt fractions, although variations as to the particular particle‐size diameter range did occur among the different elements. An attempt to resolve these relationships fitting a linear mathematical function, y=a+bx, based on the statistical association of individual particle‐size fractions with particular trace elements, gave satisfactory results. There was no evidence to indicate that certain size fractions could mobilize trace elements by virtue of their abundance in these soils. There was convincing statistical proof to show that amorphous Fe2O2, possibly by way of surface coating of finer particles, may retain a large proportion of the trace elements investigated.
THE ORIGIN OF THE PENTOSE FRACTION OF SOIL POLYSACCHARIDE
Authors: CHESHIRE M. V. , MUNDIE C. M. , SHEPHERD H.
Published: July 2006

Incubation of soil with monosaccharide for 224 days resulted in the evolution of about 80 per cent of the substrate carbon as CO2 and the transformation of 3 per cent to soil sugars whether the substrate was 14C‐glucose or xylose and whether the soil was pH 7.4 or pH 5.0. There was no detectable change in the total amounts of individual sugars in the soil during incubation.

14C‐glucose and xylose gave the same distribution of radioactivity among the soil sugars : hexoses and 6‐deoxy‐hexoses were initially well labelled, with glucose having twice the specific activity of the other sugars. As the incubation progressed some activity appeared in the pentoses (the activity in xylose became very low within the first 14 days of the 14C‐xylose incubation) and that in the hexoses slowly declined, with glucose no longer predominant. Nevertheless after 448 days the hexoses were still 3–4 times more radioactive than the pentoses. The activity in rhamnose did not decline with time so that eventually it became the most strongly labelled sugar.

Incubation of soil with glucose and 14C‐acetate showed very little transformation of the acetate to sugars indicating that glucose is not metabolized to C2 compounds before it is transformed to other sugars.

Ammo‐acids in soil incubated for 7 days with 14C‐glucose had much lower levels of radioactivity than hexoses or 6‐deoxy‐hexoses.

It is concluded that if soil pentose originates by microbial synthesis it must accumulate slowly by a long process of selective decomposition of a mixture of polysaccharides.
PHOSPHATE SOLUBILITY IN DANISH SOILS EQUILIBRATED WITH SOLUTIONS OF DIFFERING PHOSPHATE CONCENTRATIONS
Authors: JENSEN H. E.
Published: July 2006

In four out of ten Danish soils, varying in texture, pH, and forms of inorganic phosphate, phosphate solubility in dilute CaCl2 solution corresponded to the solubility of one or other of six phosphate minerals presumed to exist in soils. On adding moderate rates of phosphate, only one of the soils sustained phosphate activities corresponding to such a mineral (octocalcium phosphate). Consequently, removal of added phosphate from solution, as in the determination of the differential phosphate potential buffering capacity was the result of an adsorption type of mechanism rather than precipitation of crystalline phosphate compounds.
DARCY'S LAW AT SMALL POTENTIAL GRADIENTS
Authors: CHILDS E. C. , TZIMAS E.
Published: July 2006

Bondarenko and Nerpin have reported Bingham type plastic flow of water in a quartz capillary tube at small potential gradients, with a shear strength of about 5 × 10−2 dyne cm−2. If confirmed, this would greatly affect the theory of groundwater drainage. The experiments described here, using a granular porous material of glass spheres with pore sizes of the same order as the reported capillary radius, indicated conformity to Darcy's law (i.e. to Newtonian flow) down to one‐tenth of the threshold gradient reported by the Russian workers. Semi‐quantitative evidence confirms Darcy's law through zero potential gradient.
THERMODYNAMICS OF SINGLY CHARGED ION EXCHANGES IN THE TRACE REGIONS ON CAMP BERTEAU MONTMORILLONITE
Authors: ROBEYNS J. , VAN BLADEL R. , LAUDELOUT H.
Published: July 2006

Ion exchange equilibria for seven pairs of singly charged ions between aqueous chloride solutions and a montmorillonite clay have been studied at 25 °C for low values of the total normality of the equilibrium solution. Only the trace region for the preferred ion was investigated.

Since the analogue of Henry's law was found to be valid, the exchanges being almost ideal, standard free energies were calculated from experimental data in the region where the analogue of Henry's law is obeyed by extrapolating to half‐loading with one of the ions. The results satisfy the requirement of additivity and are in good agreement with known values.
THE RELATION BETWEEN COST AND UTILITY IN SOIL SURVEY (I–III)1
Authors: BURROUGH P. A. , BECKETT P. H. T. , Jarvis M. G.
Published: July 2006

A series of five papers compares the cost‐effectiveness of different procedures for soil survey at medium scale. The first three are presented here.

The whole trial area of 120 km2 in Berkshire, in south‐central England, was mapped in soil series by free survey at 1:25 000 for publication at 1:63 360. Three contrasting sample areas of 1.26 km2 were resurveyed to the same legend by free survey at 1:10 560, and by grid survey at a range of scales between 1:20 000 and 1:70 000, to both general purpose (soil series) and fifteen–twenty different single‐property legends. The direct costs of producing each map were recorded.

The study confirmed how much the free survey procedure depended on the external features of soil boundaries to locate them. The density of soil observations required to map soil series by free survey at the same map scale in different terrains was approximately proportional to the length of mapped boundary/km2, or to the number of separately mapped soil occurrences/km2. The density was least where the soil boundaries had the clearest external expression. Survey effort/km2 increased in proportion to the density of observations but was also affected by local differences in the ease of cross‐country access, or in the effort necessary (by spade or auger) to identify the soil at a point.

For soil series grid surveys there are approximately linear relations between log(cost) and log(map scale) with gradients between 1.3 and 1.7.

A map of soil series by grid survey is more expensive than a map of the same units, based upon the same density of observations by the same surveyor, by free survey. But a series map by grid survey by a scientific assistant is cheaper than a series map based on the same density of soil observations by free survey by a scientific officer (diplomate or graduate). The cost of an isoline map of a single soil property depends very much upon the cost of determining the property mapped, and to some extent upon the number of different isoline maps produced from a single set of samples or observations. Even at the unusually low costs of chemical analyses assumed here, an isoline map of one chemical property costs nearly twice as much as a series map by grid survey.
WATER MOVEMENT IN DRY SOILS
Authors: ROSE D. A.
Published: July 2006

hysteresis that occurs in the micro‐hydrological characteristics of a soil (conductivity and diffusivity) as functions of water content and water potential between sorption and desorption is examined for three soils (sand, loam, and clay) and sepiolite. These materials, all aggregated, are sufficiently dry that both the vapour and liquid components of water movement are important.

any water content or water potential the vapour conductivity is always bigger when wetting than when drying though differences may be small.

There is hysteresis in water (vapour+liquid) conductivity as a function of water content when vapour flow but not liquid flow is dominant. Conversely, there is hysteresis in water conductivity as a function of water potential when liquid flow but not vapour flow is dominant. Both forms of this hysteresis are small.

Hysteresis in diffusivity as a function of both water content and water potential exists, but is complicated.

Variations caused by hysteresis, though real, are likely to be negligible in practice, swamped by effects caused by changes in the soil environment (e.g. temperature) or by changes in soil management (e.g. structure).
A NEW TECHNIQUE FOR SOIL PIT ILLUSTRATIONS
Authors: WHITE L. P.
Published: July 2006

The difficulty of illustrating soil pit detail can be overcome by using selected grey density slices of original photographs. The technique of density slicing for illustrations involves the separate printing of a particular shade of grey from the original, which picks out the detail required.
SPECIFIC ADSORPTION OF SILICATE AND PHOSPHATE BY SOILS
Authors: OBIHARA C. H. , RUSSELL E. W.
Published: July 2006

The adsorption of silicate and phosphate from pure and mixed solutions by four soils known to fix phosphate strongly has been measured.

The adsorption at constant pH for each acid from its pure solution follows the Langmuir isotherm. The maximum adsorption of silicate by three of the soils from the pure solution occurs at pH 9.2, and the maximum adsorption curve for phosphate by two of the soils from its pure solution has a break in its slope at pH 6.4 and 11.6. These pHs are all just below the pK values for the dissociation of hydrogen ions from the undissociated silicic acid or the acid phosphate anions. The presence of silicate in a mixed solution, which is sufficiently concentrated in both silicate and phosphate to give maximum adsorption of either if in pure solution, does not affect the amount of phosphate adsorbed until the pH is over 6.5–7.0. At this pH the maximum adsorption curve for silicate crosses that for phosphate. The presence of phosphate in the mixed solution always depresses the adsorption of silicate. The maximum amount of silicate‐plus‐phosphate adsorbed from this mixed solution is either a little less than or equal to the amount of silicate adsorbed from the pure silicate solution if the pH is above 7. When silicate displaces phosphate, or phosphate displaces silicate, more moles of the displacing acid are adsorbed than moles of the displaced acid released.

These results for soils are similar to those of Hingston et al. for the adsorption of silicate and phosphate by goethite.
AEOLIAN ADDITIONS TO SOILS AND SEDIMENTS IN THE SOUTH PACIFIC AREA
Authors: MOKMA D. L. , SYERS J. K. , JACKSON M. L. , CLAYTON R. N. , REX R. W.
Published: July 2006

The particle‐size distribution of the whole sample and the content, particle‐size distribution, and oxygen‐isotope abundance (δ18O) in quartz were employed to determine the extent to which aeolian materials such as aerosolic dust (10 to I /μm) from Australia, loess (50 to 10μm) in New Zealand, and flöttsand (250 to 20 μm) in Australia have been accreted into soils and sediments in the South Pacific area. Although aeolian material from both local and more distant sources has been deposited on the Franz Josef, Fox, and Tasman glaciers, the extent to which aeolian materials have been added to soils in South Westland, New Zealand, could not be determined because the oxygen‐isotope abundance (12.9 to 13.5 0/00 in quartz from the soils was similar to that (13.1 to 13.9 0/00) in quartz from the dust samples.

The quartz from loess added to two basaltic soils in North Auckland, New Zealand, had an oxygen‐isotope abundance (12.9 to 13.9 0/00) slightly lower than that (15.0 to 15.4 0/00) in quartz from a greywacke‐derived soil and the underlying rock also in North Auckland. The oxygen‐isotope abundance (13.6 to 15.4 0/00) in quartz from a chronosequence of soils developed in basalt in Victoria, Australia, indicates that the quartz did not originate from the parent basalt, but probably was transported by aeolian processes from stranded beach ridges and dunes and added to the soils in the form of flöttsand, an aeolian material coarser than loess and finer than dune sand.

Most particles of the pelagic sediments fell within the aerosolic dust size range. The oxygen‐isotope abundance (12.1 to 15.1 0/00) in quartz isolated from several pelagic sediments between latitudes 35 and 45° S. was similar to that (12.9 to 15.4 0/00) in quartz from New Zealand and Australian soils located between these latitudes. An aeolian source of quartz explains the above relationship and also the decreasing delta values of quartz from sediments and soils with increasing latitude in the South Pacific area. Oxygen‐isotope abundance in quartz refutes a volcanic origin of quartz in pelagic sediments but supports the deduction of Griffin et al. (1968) from mineralogical analyses that the quartz and associated minerals were transported from lands to seas.
POTASSIUM‐ALUMINIUM EXCHANGE IN ACID SOILS I. KINETICS
Authors: SIVASUBRAMANIAM S. , TALIBUDEEN O.
Published: July 2006

A kinetic method is described and investigated for determining exchangeable Al in acid soils using M NH4Cl solutions the pH and leaching rate of which was critical for obtaining accurate and reproducible values. Molar concentrations of ammonium acetate displaced at least part of the Al chelated to functional groups in the soil organic matter.

The adsorption kinetics of K and Al from 10−3 M chloride solutions on the NH4‐saturated forms at the original soil pH of these, under leaching conditions similar to the ‘extraction’ method, showed that, when the atom ratio K/A1 > 1 in the equilibrating solution, initially more K was adsorbed than at equilibrium, although Al did not ‘over‐equilibrate’ when K/A1 < 1. At least 24 h were required for attaining equilibrium in K :A1 equilibria work with soils and clays.

The kinetics of desorption (extraction method) and adsorption of K and Al obeyed the first‐order and parabolic rate respectively. This is attributed to the large difference in anion concentrations in the two methods.
COMPUTER‐BASED SOIL MAPPING OF SMALL AREAS FROM SAMPLE DATA
Authors: WEBSTER R. , BURROUGH P. A.
Published: July 2006

A 1400 m × 600 m rectangular area of north Berkshire had been sampled at the intersections of a 100 m square grid, and seventeen properties of the soil profile measured. The eighty‐four sampling sites were classified numerically to produce a hierarchy, and the classes of the upper part of the hierarchy mapped. The mapped classes became increasingly fragmented as the number of classes increased. At the 3‐class level, the classes corresponded to character space clusters and class fragmentation was not serious. Principal‐component analysis of the sample data yielded a first component that accounted for 40 per cent of the total variance and well represented the field characters used for soil classification. An isarithm map of the first component shows how the soil changes gradually over the landscape in good agreement with a soil‐series map made by free survey.
COMPUTER‐BASED SOIL MAPPING OF SMALL AREAS FROM SAMPLE DATA
Authors: WEBSTER R. , BURROUGH P. A.
Published: July 2006

Two rectangular areas 1400 m × 600 m in south central England had been sampled at the intersections of 100 m square grids, and some 20 soil properties measured. Hierarchical numerical classifications gave classes which, when mapped, were very fragmented. Fragmentation was less when the geographic locations of the sampling sites were included in the classification. Linear functions of location and contiguity constraints produce maps that are smoother, i.e. less fragmented, but are unsatisfactory in other aspects. Inverse square and exponential functions of location produce smoother maps that are quite as good as those produced without taking location into account, in that the soil is no more variable within the classes mapped.
METAL‐COMPLEX FORMATION BY LICHEN COMPOUNDS
Authors: ISKANDAR I. K. , SYERS J. K.
Published: July 2006

The formation of soluble complexes, frequently coloured, when solid lichen compounds were shaken with water suspensions of biotite, granite, and basalt indicated that chemical weathering had occurred. The formation of colourless complexes and the adsorption of the dissolved lichen compound or complex by the silicate phase complicate the interpretation of the spectrophotometric analysis data. Lichen compounds invariably released greater amounts of Ca than of Mg, Fe, and Al from the silicates and, for each lichen compound, the release of Ca was usually greater from biotite than from granite or basalt. Release of cations from the silicate materials resulted largely from metal‐complex formation rather than from reactions directly involving hydrogen ions. Citric, salicylic, and phydroxy‐benzoic acids and EDTA, used as control organic acids, usually released considerably greater amounts of cations from the silicates than did the lichen compounds, consistent with the higher water solubility of the control organic acids. Similar amounts of Fe, Al, Ca, and Mg were released from the silicates by solutions of the lichen compounds and by solid lichen compounds. Lichen compounds are sufficiently soluble in water to form soluble metal complexes and to effect chemical weathering of minerals and rocks.
CALIBRATION OF GEL PERMEATION CHROMATOGRAPHY MATERIALS FOR USE WITH HUMIC ACID
Authors: CAMERON R. S. , SWIFT R. S. , THORNTON B. K. , POSNER A. M.
Published: July 2006

Three common gel‐chromatography materials have been calibrated for humic acid, using fractionated samples the molecular weights of which were calculated by combining sedimentation coefficients determined on the ultracentrifuge with diffusion coefficients.

The gel materials were found to have the following fractionation ranges for humic acid when tris buffer was used: Sephadex G‐100, 2500 to 100000; Bio Gel P‐150, below 1000 to 40000; Sepharose 6B, 1500 to 2500000. Borax buffer appeared to extend the range of Sephadex G‐100 to lower molecular weights.

A brief comparison is made of the retention behaviours of humic acid, proteins, and dextrans on the gel materials.
MOLECULAR WEIGHT AND SHAPE OF HUMIC ACID FROM SEDIMENTATION AND DIFFUSION MEASUREMENTS ON FRACTIONATED EXTRACTS
Authors: CAMERON R. S. , THORNTON B. K. , SWIFT R. S. , POSNER A. M.
Published: July 2006

Whole humic acid extracts are usually too polydisperse for reliable molecular‐weight measurement to be made in the ultracentrifuge by the sedimentation velocity technique. Consequently, the humic acid used in this study was fractionated with respect to molecular weight into fractions of low polydispersity by extensive use of gel‐permeation chromatography and other fractionation techniques.

The sedimentation and diffusion coefficients of the fractions were determined and molecular‐weight values calculated. These values ranged approximately from 2 × 103 to 1.5 × 106, the higher figure not necessarily representing the upper limit for these substances.

On the basis of the frictional parameters calculated from the experimental data, it is proposed that the molecule adopts the solution conformation of a randomly coiled polymer in which branching may be significant, particularly at higher molecular weights.
MIGRATION AND AGGREGATION OF Na AND Ca CLAYS BY THE FREEZING OF DISPERSED AND FLOCCULATED SUSPENSIONS
Authors: ROWELL D. L. , DILLON P. J.
Published: July 2006

The ability of clay to move ahead of an ice‐liquid interface depends on the rate of freezing, the particle size, the release of dissolved air from the water through its probable effect on local freezing rates, and on the electrolyte and its concentration through their effects on interparticle forces and particle mobility. A freezing‐rate of 1 cm per hour did not move flocculated clay in most cases, but moved dispersed clay up to 0.7 cm before being trapped in the ice with released air. Aggregates of clay (0.1 to 1 mm) were produced by freezing. After thawing they swelled and dispersed depending on the electrolyte and its concentration in a similar manner to aggregates formed by drying.
TWO METHODS FOR QUANTITATIVE DESCRIPTION OF SOIL PARTICLE SHAPE
Authors: DAVIS P. F. , DEXTER A. R.
Published: July 2006

It was required to be able to measure the shapes of soil particles in order that the influence of shape on soil mechanical properties could be investigated. Two methods were developed, both of which can be applied to particle cross‐sections or outlines. The first is a shape function which compares chord lengths with arc lengths around the particle outlines. The second method involves taking discrete Fourier transforms of the normalized curvatures of the outlines, and the production of curvature spectra. Both methods are illustrated with the use of the same data. The data were for three sizes of particle from a sandy soil. Both methods illustrate the greater asphericity or angularity of the smaller particles, which is consistent with the Griffith theory of comminution. Change in shape with particle size may be useful for classifying soils according to their methods of formation.
THE ORGANIC MATTER CONTENT OF THE SAVANNA SOILS OF WEST AFRICA
Authors: JONES M. J.
Published: July 2006

Published and unpublished data on the amounts of organic matter and nitrogen in the surface soils of the West African savanna are reviewed. In general, amounts are small; the mean carbon content of soils from 605 well‐drained sites was 0.68 per cent.

Two important factors governing amounts of organic matter in well‐drained soils appear to be the clay content and a moisture factor related to the length of the wet season and represented here by mean annual rainfall. Multiple linear regression on soil clay content and rainfall accounted for 46.5 per cent and 57.2 per cent, respectively, of the observed variability of soil carbon and nitrogen contents. These findings suggest that the low levels of organic matter in savanna soils arise from their predominantly sandy nature and from the relatively low rainfall. In poorly drained soils organic matter levels are higher but are less significantly related to clay content and rainfall. The influence of human interference and of parent material and altitude on organic matter is demonstrated in the context of geographically limited areas within the savanna for which more detailed information was available.