bluuebunny/crossref_metadata_2025 huggingface dataset:
WEATHERING OF SOME SCOTTISH BASIC IGNEOUS ROCKS WITH REFERENCE TO SOIL FORMATION
Authors: SMITH WILMA W.
Published: July 2006

The weathering of several basic igneous rocks of Lower Carboniferous age has been studied by optical microscopy and X‐ray techniques. Although similar in mineralogy, the rocks have different textures and the fine‐grained ones are most resistant to physical disintegration. In every rock, olivine has been affected by hydrothermal alteration to produce layer lattice silicates. The weathering of these products and the other mineral constituents of the rocks is described.

The fine‐sand fraction (0·2‐0·02 mm.) was selected for the purpose of determining relative stabilities of the primary minerals under weathering conditions. In order of increasing stability, the arrangement is labradorite, augite, magnetite, ilmenite, and hematite. The silt (0·02‐0·002 mm.) and clay (< 1.4 μ) fractions contain saponite and/or vermiculite depending mainly on the weathering conditions of augite and felspar. Kaolin is present in both size fractions but illite is scarce. The cation‐exchange capacity (c.e.c.) of both silt and clay fractions is consistent in most cases with the layer lattice silicate contents.
SOIL SURVEY AS RELATED TO AGRICULTURAL PRODUCTIVITY
Authors: VINK A. P. A.
Published: July 2006

Even in early times not only the growth of the crops but also the costs of their production played a certain role. Also the suitability of soils for various crops has always been changing according to economic circumstances (prices of products) and changes in technology.

Land‐use is greatly influenced by historical developments. These reflect the various economic and technical circumstances of the past. A survey of present land‐use can never be a basis for predictions on optimum land‐use. The Soil Survey is the only basis for these predictions.

Present thought on land‐use is also very strongly influenced by the chemical schools of soil science which played such a dominant role in the recent past. The soil surveyor should co‐operate with experts on soil chemistry and soil fertility to stimulate optimum agricultural productivity under present conditions.

In this changing world, land‐use is going to change rapidly, because economic and technical circumstances alter from day to day. The soil surveyor must demonstrate the different repercussions which these changes will have on his different soil types. He is the only man who can predict which surface areas are going to be affected by various changes of prices and of agricultural techniques. In this he must co‐operate with farm economists and with agricultural engineers.

The soil surveyor cannot leave this work to others, because he is the only man who fully understands the terminology of the soil map and because he is also the only man who can handle his soil units as natural units. Furthermore, he should do this because it gives him a better understanding of the units which he is mapping and therefore the quality of his soil maps will also be improved.
THE MICROBILOGY OF ROCKS AND WEATHERED STONES
Authors: WEBLEY D. M. , HENDERSON MOIRA E. K. , TAYLOR IRENE F.
Published: July 2006

A study has been made of the microbiology of rock surfaces and weathered stones. Increasing numbers of micro‐organisms were found with increasing degree of colonization by lichens, for example, of rock surfaces. The highest numbers were generally found in‘raw’ soil in rock crevices where the organic‐matter content was high. Bacteria, actinomycetes, and fungi were also found in the interior of porous weathered stones but not in unweathered stones. A high proportion of the organisms isolated were able to render silicates soluble when tested in pure culture in the laboratory.
MICROMETEOROLOGICAL OBSERVATIONS IN AN AFFORESTED AREA IN ABERDEENSHIRE: RAINFALL CHARACTERISTICS
Authors: ARANDA J. MARTIN , COUTTS J. R. H.
Published: July 2006

Rainfall was measured at an open site and under spruce, pine, and heather. Between 50 and 60 per cent. of the rain penetrated each of the canopies. Variations in the percentage penetration are associated with the area of foliage to be wetted and with the aggregate amount and the intensity of the rainfall.
TRACE ELEMENTS IN SOME WELSH UPLAND SOILS
Authors: ARCHER F. C.
Published: July 2006

Upland Welsh soils of rhyolitic origin contained less total Co, Cr, Cu, Ti, and V, more total La and Rb, and less acetic‐acid‐extractable Co and Cr than soils derived from dolerite, pumice tuff, and mixed drifts. Except for the surface enrichment of Pb, pedological factors appear to have had little effect on the distribution of total or extractable trace elements within these immature soils.
DIRECT DETERMINATION OF INORGANIC SOIL PHOSPHATE
Authors: PARTON D. J.
Published: July 2006

Many limitations of conventional methods for determining inorganic soil phosphate have been overcome by employing an isotopic dilution technique. Mobilization of soil inorganic phosphate fractions was achieved by using a solution buffered to pH 1·0 and containing orthophosphate labelled with phosphorus‐32. The inorganic phosphate thus mobilized was determined after the attainment of equilibrium between the applied and soil phosphate. Good correlation was obtained between values determined as above and those by difference between total and organic soil phosphorus. Factors influencing equilibration rate were studied: temperature, soil particle size, and soil: solution ratio.
A METHOD OF STUDYING TRACE ELEMENTS IN SOIL FRACTIONS
Authors: LE RICHE H. H. , WEIR A. H.
Published: July 2006

A method is described for dividing soils into iron oxide, sand, silt, and clay fractions suitable for trace‐element analysis. The oxides are extracted under ultra‐violet light by ammonium oxalate (pH 3·3), which dissolves goethite and other iron oxides but not gibbsite or boehmite; it also extracts some soil organic matter and, probably, trace elements associated with it.

Two horizons of two brown earths were analysed spectrochemically for Ba, Co, Cr, Cu, Ga, Mn, Ni, Pb, Sr, Ti, V, and Zr. The extracted oxides were the fractions richest in trace elements and contained large proportions of the total Co, Cu, Mn, Pb, and V. Except for Sr, Ti, and Zr, the amounts of trace elements in the sands were small and were distributed between the silicate‐mineral fractions in the order: sand > silt > clay. About half of the total Zr was in the sand fractions but appreciable amounts were in the extracts and clays. Increases of iron oxide and clay in the illuvial B horizons were paralleled by increases in the amounts of Ba, Cr, Co, Ga, Ni, and V.
THE RELEASE OF METALLIC AND SILICATE IONS FROM MINERALS, ROCKS, AND SOILS BY FUNGAL ACTIVITY
Authors: HENDERSON MOIRA E. K. , DUFF R. B.
Published: July 2006

The decomposition of silicate minerals and related substances by fungi has been investigated using two techniques: (a) the incorporation of the mineral material in agar medium, when its breakdown is indicated by the formation of clear zones round the fungal growth; (b) the determination of the metal and silicate ions, derived from the insoluble materials and brought into solution as a result of fungal activity in liquid medium. Strains of fungi which produced citric and/or oxalic acid proved to be effective in decomposing certain natural silicates, while an oxalic acid‐producing strain also released metallic ions and silica from rocks and soils. A possible role of fungi in biological weathering is discussed.
THE USE OF VAPOUR‐PRESSURE AND MOISTURECONTENT MEASUREMENTS TO DEDUCE THE INTERNAL AND EXTERNAL SURFACE AREA OF SOIL PARTICLES
Authors: FARRAR D. M.
Published: July 2006

A procedure for calculating both the external and total areas of soil particles from the relation between vapour pressure and moisture content is tested experimentally for four British clay soils. The calculated surface areas are compared with those obtained by the standard procedure from measurements using both water vapour and nitrogen, and their relation with the mineralogy of the clay fraction of the soil (as determined by X‐ray analysis) is examined. It is concluded that this new method is sufficiently accurate to be used as an indication of the clay mineralogy.
TOXICITY AS A CAUSE OF THE INEFFICIENCY OF UREA AS A FERTILIZER. I. REVIEW
Authors: COURT M. N. , STEPHEN R. C. , WAID J. S.
Published: July 2006

The causes and mechanisms of phytotoxicity that can bring about poor or adverse crop responses to applications of solid urea to soil are reviewed. Compounds which may cause phytotoxicity are urea, transformation products of urea formed during manufacture (biuret), and transformation products produced in the soil or in plants (cyanate, carbamate, ammonia, and nitrite). Of these, ammonia and nitrite are considered to be the most likely causes of phytotoxicity when urea of low biuret content is used.
ALUMINIUM AND IRON PHOSPHATE STUDIES RELATING TO SOILS
Authors: BACHE B. W.
Published: July 2006

The determination of ion activities in solution during the sorption of phosphate on to gibbsite and hydrous ferric oxide has shown three stages to the reaction: (i) a high energy chemisorption of small amounts of phosphate; (ii) precipitation of a separate phosphate phase; (iii) a low energy sorption of phosphate on to the precipitate. The values of ion activity products for the precipitation reaction do not correspond with the solubility constants of variscite and strengite. Ion activity products are not likely to be useful for indicating the existence of separate A1 and Fe phosphate phases in soils. The variation of solution phosphate activity with phosphate sorbed is suggested as a basis for a ‘phosphate characteristic’ curve for phosphate‐reactive heterogeneous systems.
CATION‐EXCHANGE EQUILIBRIA WITH VERMICULITE
Authors: WILD A. , KEAY J.
Published: July 2006

The exchange of Na, Mg, Ca, Sr, and Ba ions has been studied in the temperature range 25° C‐70° C.

Vermiculite shows a preference for divalent ions over Na ions at 25° C and the preference increases very greatly at higher temperatures. The preference is largely determined by the increase in entropy which accompanies the replacement of monovalent ions by divalent ions in the vermiculite. Preference is less marked between divalent ions. These ions are similarly hydrated in vermiculite, which differs in this respect from resins and most other clay minerals. The greater affinity of Mg ions compared with other divalent ions is explained by their closer approach to the silicate surfaces.
THE MOBILIZATION OF IRON BY AQUEOUS EXTRACTS OF PLANTS
Authors: MUIR J. W. , MORRISON R. I. , BOWN C. J. , LOGAN J.
Published: July 2006

As a first step in identifying the agents responsible for the mobilization of ferric iron by an aqueous extract of pine needles, the extract is divided into three fractions, an amino‐acid fraction, an organic‐acid fraction, and a neutral fraction. The principal constituents of the amino‐acid and organic‐acid fractions are then identified and their contents determined by means of paper and column chromatography.
THE INFLUENCE OF TEXTURE ON THE MOISTURE CHARACTERISTICS OF SOILS
Authors: SALTER P. J. , WILLIAMS J. B.
Published: July 2006

When the 1/3 and 15 atm. percentages were used as the upper and lower limits of available‐water, respectively, the values for the available‐water capacities (AWC's) of the soils studied were smaller than those obtained by using the direct sampling technique for the upper limit, and the permanent wilting percentage (determined on soil cores) for the lower limit of available‐water; the differences varied from 9 to 76 per cent with a mean of almost 40 per cent for the eleven soils studied. The importance of techniques for the determinations of the AWC of soils is discussed. The moisture characteristic of a soil could be considerably influenced by the structure of the soil sample on which the determination was made, and it is concluded that the moisture characteristic should be determined on undisturbed soil cores.
THE RATE OF IMMOBILIZATION OF APPLIED PHOSPHATE IN RELATION TO SOIL PROPERTIES
Authors: LARSEN S. , GUNARY D. , SUTTON C. D.
Published: July 2006

The fate of superphosphate applied at 500 and 1,000 Ib P2O5 per acre in a field experiment with twenty‐four sites was followed by measuring changes in the L‐value over 5 years. The L‐value decreased exponentially at a rate that was expressed as the time in years for half the applied phosphate to become non‐labile (the half‐life). The two fertilizer rates gave similar values in most of the experiments and half‐life values were satisfactorily measured for nineteen soils; the values ranged from 1 to 56 years.

Some relationship between half‐life values and a number of soil properties was sought. The only significant correlation was with the hydrogen‐ion concentration, from which it is suggested that the decrease in labile phosphate could be the result of the formation of a crystalline basic calcium phosphate at a rate that increases with soil pH.
THE RETENTION OF AMORPHOUS, COLLOIDAL ‘FERRIC HYDROXIDE’ BY KAOLINITES
Authors: FOLLETT E. A. C.
Published: July 2006

The sorption and distribution of amorphous colloidal ‘ferric hydroxide’1 particles on the surfaces of kaolinite flakes were studied by electron microscopy. The sorption reaction was crystallographically specific with particles observed only on basal plane surfaces and was unaffected by the presence of excess NH4+, Ca++, or Al+++ ions. Cationic surface‐active agents prevented the reaction. Differences observed in colloid distribution and density on the introduction of a competing surface indicated that only one surface of a flake was attracting colloid particles and similar experiments with quartz and gibbsite suggested the silicatetrahedra surface of kaolinites as the probable site of colloid fixation. The distribution of colloid was unaffected by pH variation, saturation with ammonium acetate, prolonged washing, or ultrasonic vibrations. The colloid was removed only by extraction with sodium dithionite.
OBSERVATIONS ON THE BIOLOGICAL DEVELOPMENT OF MACROPORES IN SOILS OF ROMNEY MARSH
Authors: GREEN R. D. , ASKEW G. P.
Published: July 2006

Many of the soils developed on Recent alluvium in Romney Marsh have abundant interconnecting pores, holes, and cavities in their subsurface horizons formed by the activity of roots, ants, and earthworms. Ants are considered to be the dominant agents in forming highly developed underground systems of galleries and chambers. These features are apparently continuous over large areas and are not restricted to any particular soil, but occur on differing soils with a considerable range of pH, salinity, texture, and fluctuations of water‐tables. Consequently, many of the soils have drainage and other characteristics that cannot be deduced from a consideration of texture or structure (pedality) alone. The characteristics of these macropores, as revealed by the infiltration into the soil of cast‐forming materials such as plaster of Paris, are described, and their origin, distribution, and significance in relation to land use are discussed.
THE HUMIC ACIDS EXTRACTED BY VARIOUS REAGENTS FROM A SOIL
Authors: POSNER A. M.
Published: July 2006

Solutions of o.5N NaOH, o.1M pyrophosphate (pH 7), and o.5N Na(CO2−3/HCO−3) [2:1] extract humic acid and organic matter from a soil with decreasing effectiveness.

Pre‐treating the soil with o.1N HC1 increased the yield of humic acid obtained with the alkaline extractants. An additional pre‐treatment with a mixture, which was normal with respect to HC1 and HF, gave a slight reduction in yield.

Increasing the temperature of extraction increased the yield of humic acid.

The total C extracted was usually in excess of the humic acid recovered. The difference was obtained as ‘humins’.

The sum of the Fe2O3, SiO2, and A12O3 contents of the humic acids was always less than 2 per cent. Where the extraction was carried out at room temperatures the SiO2/Al2O3 ratio suggested that they might be present as clay mineral. When extraction was carried out at an elevated temperature this ratio was altered.

Humic acids of low ash content (0.1–0.5 per cent) could be obtained by the use of hot reagents. Of all the extractants used at room temperature, pyrophosphate produced the humic acid of lowest ash content (∼ 0.2 per cent).

The Fe2O3 content of the humic acids was not correlated with their SiO2 or A12O3 content.

The N‐content of the humic acids was substantially independent of the method of extraction.

The cation‐exchange capacities (C.E.C.), average pK values and range of pK values, have been determined from the titration curves of the humic acids. These quantities vary with the method of extraction.

There are good correlations between cation exchange capacity and both average pK values and the range of pK values.

The within‐molecule variation of pK values appears to be greater than the between‐molecule variation.

No correlation exists between C.E.C. and Fe, Al, Si, and N content of the humic acids.
ISOTOPIC EXCHANGE OF FIXED AMMONIUM
Authors: NEWMAN A. C. D. , OLIVER S.
Published: July 2006

The isotope 15N was used to study the rate of exchange between unlabelled NH4‐hydrobiotite and labelled solution NH4.

Most of the isotopic dilution occurred within 10 minutes of adding the solution to the solid, but even after 13 days less mineral‐NH4 had exchanged with isotope than was removed by several extractions with KC1 solution.

NH4 remaining in the mineral after extraction with KC1, conventionally named ‘fixed ammonium’, contained some isotope which was sorbed without release of unlabelled NH4; the fixed ammonium was, therefore, not isotopically exchangeable. The sorption was shown to result from incomplete ammonium saturation of hydrobiotite, isotope slowly replacing interlayer cations trapped by lattice collapse.

The rate of sorption was initially controlled by a temperature‐dependent diffusion process for which the activation energies were between 9 and 13 kcal/ mole. In the later stages of the reaction the rate became progressively slower than predicted by the diffusion equation, and analysis of the kinetics suggested that, ultimately, exchange of cations at the sorption sites was the rate‐limiting process.
STUDIES ON THE DECOMPOSITION OF PLANT MATERIAL IN SOIL
Authors: JENKINSON D. S.
Published: July 2006

Soil samples taken during an experiment on the decomposition of 14C‐labelled ryegrass in soil under field conditions (see Part I) were air‐dried, irradiated, exposed to CHCl3 or CH3Br vapours, oven‐dried or autoclaved. After these treatments the soils were inoculated, incubated, and the output of CO2 measured. All these methods of partially (or, in some cases, completely) sterilizing soil rendered a small heavily labelled fraction of the soil organic matter decomposable. This fraction is postulated to be the soil biomass. Treatments involving heat or irradiation rendered small additional amounts of the soil organic matter decomposable (by processes other than the killing of organisms).

Incubating unsterilized soil with partially sterilized soil did not decrease evolution of CO2. This suggests that partial sterilization does not increase mineralization by destroying toxic substances that inhibit microbial growth, or by disturbing a host: predator balance in the unsterilized soil.

The longer the labelled ryegrass was allowed to decompose in the field, the less labelled‐CO2 was evolved after partial sterilization. In contrast, the same amount of unlabelled‐CO2 was evolved from a soil that had been incubated 1 or 4 years with ryegrass. The labelled part of the biomass is considered to be largely zymogenic (with a half life of approximately 1.5 years), the unlabelled part largely autochthonous, remaining almost constant over the 3‐year period.

It is suggested that the size of the soil biomass can be roughly estimated from the size of the flush of CO2 after CHCl3 vapour treatment. Calculated on this basis, 2.3–3.5 Per cent the unlabelled‐C in these soils (i.e. the C present in the soil before the labelled ryegrass was added) was in the biomass. Of the original ryegrass C added, 10–12 per cent was in the biomass after 1 year, decreasing to 4 per cent after 4 years.
QUANTITATIVE DETERMINATION OF CALCITE AND DOLOMITE IN SOILS
Authors: PETERSEN G. W. , CHESTERS G. , LEE G. B.
Published: July 2006

Soil carbonates were differentiated into calcite and dolomite and determined quantitatively by a method based on their differential solubilities in 0.30 M Na citrate—0.14 M Na dithionite. Calcite dissolution was favoured by the acidic and chelating nature of the citrate. Prior destruction of iron‐oxide coatings on soil carbonates and/or iron oxide‐carbonate complexes by the citrate‐dithionite iron‐removal process was necessary for complete calcite dissolution. This method consisted of a total carbonate determination, selective dissolution of calcite with a citrate‐dithionite extraction, and determination of dolomite by difference.

Citrate‐dithionite soluble calcite and dolomite are calculated from the quantities of extracted Ca and Mg. Soil exchangeable Ca and Mg may interfere and should be removed prior to citrate‐dithionite extraction on soils of high exchange capacity and/or low carbonate content. Interferences arising from dissolution of non‐carbonate Ca‐ and Mg‐containing soil minerals were considered negligible.

Replicate analyses of a broad spectrum of samples suggest that the method is highly satisfactory for the determination of calcite and dolomite contents of soils and sediments of very variable composition. The occurrence of dolomite appears to be related to dolomitic source areas and is detritial whereas calcite is primarily reprecipitated (secondary) carbonates, although some calcite may be of detritial nature, e.g. shell materials or calcitic limestone drift.
THE CORRELATION OF SURFACE AREA WITH OTHER PROPERTIES OF NINETEEN BRITISH CLAY SOILS
Authors: FARRAR D. M. , COLEMAN J. D.
Published: July 2006

The total and external surface areas of nineteen British clay soils were determined from measurements of their water and nitrogen adsorption respectively. In addition, four physical and chemical properties of these soils were determined; liquid limit, plastic limit, cation exchange capacity, and clay content.

The correlation between these six measured properties was examined. Total surface‐area, liquid limit, and cation exchange capacity, had correlation coefficients of 0.90 or greater. This is sufficiently high to enable an indication of these three properties to be obtained from measurements of any one of them.

The correlation between these three properties and the rest was slightly lower for the plastic limit, and considerably lower for the clay content and external surface‐area, although all were significant at the 5 per cent level.
ION EXCHANGE IN SOILS FROM THE ION PAIRS K–Ca, K–Rb, AND K–Na1
Authors: DEIST J. , TALIBUDEEN O.
Published: July 2006

Isotopic exchange of 43K, 24Na, 86Rb, and 45Ca was used to measure the equilibria between some arable soils and mixed chloride solutions of the ion pairs, K–Ca, K–Rb, and K–Na; the results were interpreted by a thermodynamic treatment of the exchange isotherm (Gaines and Thomas, 1953). The cation exchange capacities of the soils were not constant for the three ion pairs and decreased appreciably with K‐saturation in the K–Ca systems because Ca ions were trapped inside the interlayer spaces. That soils preferred K to Na in the K–Na systems and Rb to K in the K–Rb systems, was explained in terms of the standard free‐energy changes of the exchange reactions.

The activity coefficients of the adsorbed ions, f, changed with K‐saturation differently for the three ion pairs: fNa and fCa decreased continuously with increasing K‐saturation whereas fRb remained almost constant. However, with increasing K‐saturation, fK increased in the K–Na systems, remained unchanged in the K–Rb systems, and first increased and then decreased in the K–Ca systems. These changes are interpreted in terms of the effect of the various ions on the interlayer space of 2 : 1 type clay minerals and the possible distribution of adsorbed ions between the Gouy and Stern layers.
MEASUREMENT OF SOIL MOISTURE IN THE FIELD BY NEUTRON MODERATION
Authors: LONG I. F. , FRENCH B. K.
Published: July 2006

Design, calibration, working precautions and field use of a soil‐moisture meter are described. The probe carries a source 241Am‐Be and a detector 10BF3 in an Al case, 3.4 cm diam and 17 cm long. Source and detector are as close to each other as possible, so giving a desired linear relationship between thermal neutron count and the volumetric water content around the probe. The portable sealer incorporates some new features of circuit design that lead to ease of operation and small size: it weighs 5 kg. Factors involved in calibration or the interpretation of a calibration curve are: resolving time of the sealer, the volume of soil explored by the neutrons, the effect of a moisture gradient, and the possible effect of elements other than hydrogen.

Field trials were in two groups. In 1962 and 1963 frequent measurements were made in bare clay soil and under a nearby barley crop: from the profiles, the extraction of water from the bare soil was limited to the top 30 cm, but the barley roots took water out at least as deeply as the maximum depth of measurement then possible, 90 cm. In 1964 similar measurements under first‐year Timothy and Meadow Fescue, irrigated and non‐irrigated, showed that the total water abstracted by each was nearly the same, but the Timothy took most of its water from the top 40 cm of the profile, whereas the Fescue took more water from the lower depths. Combining the estimated deficits with known rainfall gives values of periodic evaporation in good agreement with aerodynamic estimates based on temperature, humidity, and wind profiles above the crop, and in fair agreement with potential evaporation‐rates calculated from routine weather records.
THE INFLUENCE OF TEXTURE ON THE MOISTURE CHARACTERISTICS OF SOILS
Authors: SALTER P. J. , WILLIAMS J. B.
Published: July 2006

The available‐water capacity (AWC) of soil profiles in the field may be estimated by (a) measuring the thickness of each soil horizon; (b) assessing its texture; and (c) summing the products of the thickness of each horizon and the mean values of AWC for the relevant textural classes. (This mean value of AWC was calculated from the average particle‐size composition and from a relationship between particle size composition and AWC.) Estimates of AWC using this method were compared with measured values for each of 39 soils. When a 21 textural‐class system was used to describe the soils, the mean error (the error of the estimated AWC value relative to the measured value) was ±10 per cent and with a 12 class system the mean error was ±17 per cent.
DIRECT MEASUREMENTS OF THE DISTRIBUTION OF OXYGEN IN SOIL AGGREGATES AND IN COLUMNS OF FINE SOIL CRUMBS
Authors: GREENWOOD D. J. , GOODMAN D.
Published: July 2006

The micro electrode of Evans and Naylor was modified to permit measurements of oxygen concentration in soil and was used to determine the distribution of oxygen in (a) agar which contained yeast and glucose and served as a model of a respiring water‐saturated soil; (b) saturated spherical soil aggregates; (c) partly saturated columns of fine soil crumbs. Measurements in (a) and (b) but not in (c) agreed closely with predictions by diffusion theory. The disagreement appeared to result from water being unevenly distributed in the columns.
EVALUATION OF METHODS FOR DETERMINING AVAILABLE SOIL POTASSIUM BASED ON POTASSIUM UPTAKE BY PLANTS1
Authors: FEIGENBAUM SALA , HAGIN J.
Published: July 2006

Measurements of exchangeable K, percentage of exchangeable K in the total exchange capacity, K extracted in a CaCl2 solution, and the change in free energy of exchange of K for Mg and Ca (ΔF) were compared as methods for the evaluation of available K in soils. The evaluation was based on the K uptake of plants in a pot exhaustion experiment. The ΔF value was best correlated with the K uptake of the plants. A good correlation was found between the logarithms of the exchangeable K expressed as a percentage of the cation exchange capacity and ΔF values.
GENESIS, MINERALOGY, AND RELATED PROPERTIES OF WEST INDIAN SOILS
Authors: AHMAD N. , JONES R. L. , BEAVERS A. H.
Published: July 2006

The Montserrat series is one of the most fertile of tropical soils. Substantial amounts of exchangeable K, available P, and favourable organic matter content and distribution contribute to its unique properties. P occurs in amounts ranging from 0.4 to 0.6 per cent, about 75 per cent of which is inorganic with Fe phosphates making up the bulk. Truog's reagent almost quantitatively extracts Ca phosphate and Bray's and Olsen's reagents extract mainly Al phosphate. Exchangeable K is derived from glauconite. High exchangeable Ca and Mg contents derived from weathering of carbonates impart a favourable pH to the soil for plant growth. Exceptional structural stability to 120 cm depth is associated with high free iron oxide, organic matter, and Ca contents.

The outstanding feature in mineral weathering is the rapid transformation of glauconite through vermiculite to kaolinite and the formation of goethite. Considerable interlayering occurs between vermiculite with sesquioxide coatings and mica‐vermiculite interlayers. Much of this weathering occurs in the calcareous, oxidized, friable parent rock.

The features of the Montserrat series described above substantiate its classification as a Brown Earth (Mollisol).
SULPHATE DISTRIBUTION IN SOLONETZIC SOIL WITH A WATER TABLE
Authors: KHAN S. U. , WEBSTER G. R.
Published: July 2006

Soil columns were used to study sulphate distribution in Thin Duagh Loam soil as influenced by the presence of a water table. The concentration pattern showed that retention was greater in the surface soil than at lower depths. The data suggest that sulphate tends to move more slowly than water in soil.
SOIL SUCTION BY THE RAPID METHOD: AN APPARATUS WITH EXTENDED RANGE
Authors: DUMBLETON M. J. , WEST G.
Published: July 2006

In the rapid method of measuring soil suction the sample is placed on a porous plate attached to a capillary flow tube containing water. A suction is applied to the flow tube and rapidly adjusted to equal the suction of the soil, without change of soil‐moisture content. A form of the apparatus is described which has provision for very convenient and rapid adjustment of the applied suction by the use of either a vacuum pump or an air piston. The range of the apparatus is extended from the usual limit of pF 3 up to pF 3.35 by applying air pressure to a chamber enclosing the sample, using a hand pump. Suction curves for a sand, a silty clay, and a heavy clay illustrate the application of the apparatus, which can readily be constructed in a form suitable for field use.
CHANGES IN SOIL PROPERTIES ASSOCIATED WITH THE REMOVAL OF IRON AND ALUMINIUM OXIDES
Authors: DESHPANDE T. L. , GREENLAND D. J. , QUIRK J. P.
Published: July 2006

Red soils representing the major groups in which iron oxides are thought to exert a favourable effect on physical properties, have been treated with Na‐dithionite and citrate, or Na‐dithionite and 0.05 n HC1. These treatments removed the free iron oxides and some aluminium oxides and silica. Changes in the physical properties of the soils were measured by permeability, wet‐sieving, mechanical dispersion, and swelling methods. These were compared with the changes induced by corresponding control treatments in which the soils were treated with Na2SO4 and Na‐citrate, or Na2SO4 and 0.05 n HC1. The control treatments extracted some aluminium oxide and minor amounts of iron oxides and silica. In general, the control treatments decreased the stability of aggregates, increased the proportion of clay and silt but had little effect on the swelling. The treatments, which removed all the free iron oxide, caused no changes in excess of those due to the controls. The specific surface areas of samples treated with dithionite and acid, or sulphate and acid were determined by nitrogen adsorption methods. Removal of free iron oxides led in all but one instance to a reduction in the specific surface area, whereas sulphate and acid invariably increased the specific areas of the samples. The results show that most of the free iron oxides in these soils are present as small particles having little effect on the physical properties of the soil. The changes in physical properties brought about by dilute acid treatment indicate that the ‘active’ oxides in these soils are composed partly or wholly of the aluminium, iron, and silicon oxides which are readily soluble in dilute acid.
BASALTIC SOILS OF SOUTH‐WEST ICELAND. II
Authors: HELGASON BJARNI
Published: July 2006

Data for mechanical and chemical analyses are presented with tabulated mean and median values based on fifty‐five freely drained and ten poorly drained soils.

The soils are relatively coarsed textured. The sand content of the mineral fraction is about 70 per cent (mean value) for freely drained and about 45 per cent (mean value) for poorly drained soils.

Organic C is generally high in freely drained soils but relatively low in poorly drained soils, because of accumulating aeolian matter in the latter group, mean values are 8.2 in freely drained and 16.5 per cent in poorly drained soils. The C/N ratio is about 15 for each soil group.

The cation exchange properties including pH seem to be dominated by organic matter, which may contribute to the total CEC of the soils about 165–300 me/100 g C. CEC of soils is usually 40–50 me/100 g. For some selected soils CEC of the separated mineral fractions was confirmed experimentally through ammonia retention.

The pH level, especially of the freely drained soils, is relatively high (mostly 5.4–6.3) in spite of low degree of base saturation (mostly 10–30 per cent), a characteristic probably derived from the parent material. A highly significant correlation exists between pH and organic C.

Proportionally exchangeable Ca seems low, while Mg and Na may be abundant. In some soils exchangeable Mg may exceed Ca.
USE OF RADIOACTIVE 59Fe FOR TRACING SOIL PARTICLE MOVEMENT
Authors: COUTTS J. R. H. , KANDIL M. F. , NOWLAND J. L. , TINSLEY J.
Published: July 2006

59Fe appeared to be a suitable tracer for investigating soil particle movements and experimental results have demonstrated quantitatively that, when a dilute radioactive FeCl3 solution is applied to soils of varied texture, this isotope is firmly absorbed, and shows little tendency to downward movement by leaching. Addition of the chelating compound di‐ethylene triamine penta‐acetic acid (DTPA) greatly improves the uniformity of absorption.

The surface movement of labelled soil particles was readily detected by direct scintillation counting of grid reference points over trays of soil exposed in the field or of core samples transported to the laboratory, and less sensitively by autoradiographs on X‐ray film applied to the surface of ground plots.

Under the summer and winter weather conditions prevailing at Aberdeen, the displacement of soil from bare surfaces by rain splash is markedly affected by wind speed and direction. Even with light showers, relatively low wind speeds and slopes not exceeding 6°, some of the labelled soil particles migrated distances of 60 cm from the treated areas in the centre of ground plots 2 m square.
SIGNIFICANT PARTICLE SIZE VARIATION AND WEATHERING IN ORTHIC PODZOL PROFILES1
Authors: VALENTINE K. W. G. , MILLETTE J. F. G.
Published: July 2006

Physical analyses of 15 Orthic Podzols of south‐eastern Quebec, Canada, showed that the extent of the breakdown of the gravel, sand, and silt and the accumulation of clay was dependent on the porosity of the parent material and the type of rocks in the gravel. There was no clay accumulation in the B horizon when the results were expressed on a percentage weight per unit volume basis. The sand was fractionated into five grades. The specific gravity of the gravel was smaller than that of any sand fraction and that of the sand increased towards the finer fractions. The specific gravity of the gravel also increased down the profile; that of the sand did not. These changes were also related to the type of parent material.

A value for each horizon, calculated as follows:
image
was used as an index of weathering to show the degree of weathering intensity.
CHANNELLING OF ALLUVIAL DEPRESSION SOILS IN IRAQ AND SUDAN
Authors: WHITE L. P. , LAW R.
Published: July 2006

Distinctive channel patterns in the floors of alluvial clay depressions in Iraq and Sudan as well as in other parts of the arid zone have been described as gilgai in the past though their morphology differs from examples of gilgai as originally described in Australia. The soils on which the channels develop vary considerably and do not always contain large proportions of expanding lattice clay. The formation of the micro‐relief may not necessarily involve heaving of the subsoil as in the Australian gilgai. It is formed rather by a process of uneven settling and compaction, the patterns of channelling being controlled by pre‐existing surface irregularities. If the formation of the micro‐relief does not involve heaving, it is probable that the channels will not reform after reclamation. The term‘tabra channels’ is suggested for the feature.
THE CONSTRUCTION OF CALIBRATION CURVES FOR DETERMINING WATER CONTENT FROM RADIATION COUNTS
Authors: HOLLAND D. A.
Published: July 2006

The application of regression theory to the construction of calibration curves for the estimation of water content from an observed radiation count is possible only when the relationship between count and water content is linear, a homogeneous error applies to the dependent variate, count, whatever its value, and the independent variate, water content, is determined free of error. Determination of the errors of estimation is further complicated by the necessity to fit the regression of count, as the dependent variate, on water content and then to invert the equation in order to estimate moisture content from count. It is shown that these requirements can be fulfilled by an initial transformation of the data and by repeated sub‐sampling for the determination of water content. A method is given for calculating errors of estimation.

Experimentally, it was found that a transformation (logarithmic) was necessary when calibrating a beta‐gauge for leaf moisture measurement. When calibrating a neutron probe for soil‐moisture measurement no transformation was required, but it was necessary to take repeated sub‐samples for water content determinations.
A NATURAL SYSTEM OF SOIL CLASSIFICATION
Authors: MUIR J. W.
Published: July 2006

Definitions of natural classification are given which emphasize the importance of theory and concept in the construction of natural systems. The proposed system is based on two principles of soil formation. The first principle emphasizes the three‐dimensional nature of soil bodies. The second principle, known as the Principle of Developmental Sequences, is concerned with stages of soil development. The many developmental sequences identified by pedologists are correlated by means of a small number of constituents which are lost and gained during soil formation. These constituents, in an order of eluviation/illuviation, are used to rank the properties on which the proposed system is based. Soil horizons are defined according to the ranked properties and the classes of the system are, in turn, defined in terms of the horizons, with the result that the central statement of the system is the Principle of Developmental Sequences.
ERODED SOILS OF THE LOWER SWANSEA VALLEY
Authors: BRIDGES E. M.
Published: July 2006

The investigation attempts to ascertain rates and amounts of soil erosion from a small unvegetated area (120m×15m). Measurements from markers embedded in the soil indicate a removal of 10 mm per annum on 5°C slopes, 32 mm per annum on 45°C slopes, and 43 mm per annum on 62°C slopes. A sediment trap indicated that in a week when there was 56·8 mm rain, approximately 60 g/sq m was eroded. Results of the work are used in an explanation of the eroded soils of a much larger area, known as the Lower Swansea Valley.
GENESIS AND MORPHOLOGY OF SOME ALPINE PODZOL PROFILES
Authors: BOUMA J. , HOEKS J. , VAN DER PLAS L. , VAN SCHERRENBURG B.
Published: July 2006

Some representative podzol profiles from an Alpine region are described. Their genesis is mainly a function of vegetation and drainage and is analysed by morphological, chemical, and mineralogical methods. The effect of soil management on profile development as governed by recent economic advances has been discussed. When meadows with brown soils that are preserved by careful management are abandoned, heather and bilberries start growing and podzolization processes begin. Illuviation horizons are formed that have a friable consistency when formed in these meadows, but that may be hard and brittle when developed in sandy till with only heather or bilberries. Soil physical processes lead only to a fragmentation of parent rock, whereas pronounced chemical weathering occurring in these soils—decreasing in intensity with depth—produces an active clay fraction, the composition of which is discussed. Chemical weathering was most pronounced under poor vegetation. The higher content of silt in the topsoil can be partly attributed to sedimentation of wind‐blown particles. Frost action leads to sedimentation of fine soil particles on top of larger mineral fragments lying at some depth in a profile.
DISPERSION, MECHANICAL COMPOSITION, AND FRACTIONATION OF WEST INDIAN VOLCANIC YELLOW EARTH SOILS (ANDEPTS)
Authors: AHMAD N. , PRASHAD S.
Published: July 2006

Methods of dispersion used in Japan and New Zealand for soils formed on recent volcanic ash (Andepts) which involved adjusting the pH of organic matterfree soil suspensions to 4 or 10·5 were not effective on similar soils in the Caribbean. Partial dispersion was obtained by adjusting the pH to between 2 and 3 but lower (down to pH 1) and higher (up to pH 11·1) pH values were ineffective. Substantial amounts of Al dissolved at pH 1–3 probably as a result of some disintegration of the allophanoid minerals. Zirconium nitrate solutions were very efficient in causing dispersion, a concentration of 12 me Zr being necessary for complete dispersion of 20 g samples of soil. Excess Zr did not adversely affect dispersion but resulted in depression of pH of the suspensions. The high ionic charge, small atomic radius, and low ionization potential of Zr apparently resulted in saturation of the cation exchange capacity and some isomorphous substitution of Al leading to a net positive charge of the clay and an increase in anion exchange capacity. This was considered to be responsible for dispersion.
ACCUMULATION OF ORGANIC MATTER IN A CHRONOSEQUENCE OF SOILS DEVELOPED ON WIND‐BLOWN SAND IN NEW ZEALAND
Authors: SYERS J. K. , ADAMS J. A. , WALKER T. W.
Published: July 2006

A study was made of the amounts and distribution of C, N, S, and organic P accumulated over a period of 10 000 years of soil development on wind‐blown sand. After initial rapid rates of accumulation of C, N, and organic P during the first 1000 years, subsequent rates of gain were slower, but steady states for C, N, and S had still not been reached after 10 000 years. Sulphur declined during the first 50 years of soil development but then increased in a parallel fashion to organic C. During 10 000 years, gains of organic C, total N, total S, and organic P were 204 000, 9800, 1180, and 1170 kg/ha m profile, respectively. Gains in total N and S in the older soils are readily accounted for by returns in precipitation. Pronounced changes in soil organic matter composition during 10 000 years are reflected in the widening of the C/N ratio (8 to 20) and the C/organic P ratio (39 to 159).
COHESION OF SOIL PARTICLES AND THE INTRINSIC RESISTANCE OF SIMPLE SOIL SYSTEMS TO WIND EROSION
Authors: SMALLEY IAN J.
Published: July 2006

In a simple dry soil system in which erosion is taking place by virtue of the impact of saltating sand grains, the intrinsic variables affecting soil resistance can be investigated with the aid of a mathematical model. The soil erodibility depends on the cohesiveness of the soil which is indicated by the tensile strength. This is directly proportional to the packing density of the system, to the co‐ordination number of the particles, and to the inter‐particle bond strength. Tensile strength is inversely proportional to the cube of the particle diameter. In a cohesive material any decrease in the particle size produces a great increase in the tensile strength and hence the mechanical stability is improved, but because the particles are lighter they are easily eroded once they are disturbed.
VARIATIONS IN THE USEFULNESS OF RAPID SOIL MAPPING IN THE NIGERIAN SAVANNA
Authors: TOMLINSON P. R.
Published: July 2006

The rapid soil mapping required in developing countries can only be done by relating soils to land form and geology. A usefulness classification of mapping units is suggested. The most useful contain the least soil variation. Units with regular soil variation within them are more useful than those with random variation. In the Nigerian Savanna the most useful units are on hill remnants and homogeneous sediments, particularly coarse siliceous sandstones and fixed dunes. The least useful are on dissected areas, heterogeneous sediments, igneous and metamorphic rocks. The least fertile soils often dominate the most useful units. Rapid soil mapping should be useful in the north and the lower Niger and Benue valleys.
RE‐SORPTION OF SOIL PHOSPHATE DURING FRACTIONATION
Authors: RAJENDRAN N. , SUTTON C. D.
Published: July 2006

Studies with 32P on six soils showed that considerable re‐sorption of phosphate occurred during the Chang and Jackson fractionation procedure. This re‐sorption resulted in an underestimate of the NH4Cl‐extractable phosphate and an overestimate of‘occluded’ phosphate, with less consistent but significant changes in the other fractions. The corrections necessary to allow for re‐sorption varied between soils.
THE SIMULATION OF GASEOUS DIFFUSION IN SOILS
Authors: RADFORD P. J. , GREENWOOD D. J.
Published: July 2006

Computer simulation techniques are presented as a means of applying diffusion theory to two problems concerning the dynamics of oxygen and carbon dioxide distributions in soils. It is demonstrated that these techniques facilitate both problem formulation and solution, and require less mathematical skill than the equivalent analytic techniques. For problems with no analytic solution, simulation can still yield results with an accuracy equal to other numerical methods. Using simulation techniques, it was computed that stationary state conditions for carbon dioxide in a 0·7 cm layer of soil were established 24 hours after waterlogging. Similarly it was computed that for oxygen diffusing through a 0·4 cm layer of soil, equilibrium was attained within six minutes. These data were useful in that they justified the assumptions regarding equilibrium conditions which had necessarily been made in previous experiments. Simulation techniques may be of widespread use, not only for solving diffusion problems, but also for applying other fundamental laws to specific situations.