bluuebunny/crossref_metadata_2025 huggingface dataset:
IRON AND ALUMINIUM AS CEMENTING SUBSTANCES OF SOIL AGGREGATES
Authors: GIOVANNINI G. , SZQUI P.
Published: July 2006

A method is described for extracting fractions of soil iron and aluminium without removing organic matter. The extraction is by acetylacetone in a non–polar solvent and is virtually complete in zoo h.

Similar amounts of iron and aluminium are extracted by acetylacetone in either benzene or water, but organic matter is extracted in detectable amounts only by acetylacetone in water. Extraction in aqueous solution after acetylacetone in benzene removes only organic matter, with no appreciable release of iron and aluminium. Metals extracted by acetylacetone in benzene are therefore considered to be bonded to that part of the organic matter which is extracted by acetylacetone. Water alone does not extract significant amounts of organic matter after removal of iron and aluminium by acetylacetone in benzene. The refolding of the hydrophilic surface units of the organic matter, caused by non–polar solvents, may hinder the extraction by water.
ADSORPTION OF ALIPHATIC ALCOHOLS BY SOIL MINERALS AS A METHOD OF EVALUATING THEIR HYDROPHOBIC SITES
Authors: TSCHAPEK M. , WASOWSKI C.
Published: July 2006

The density of hydrophobic sites on the surface of some soil minerals has been determined by adsorption of aliphatic alcohols from aqueous solution. The amount of alcohol adsorbed was evaluated by measurements of the surface tension of the solution.
DECODE—A COMPUTER PROGRAM FOR TRANSLATING CODED SOIL PROFILE DESCRIPTIONS INTO TEXT
Authors: WEBSTER R. , LESSELLS CHRISTINE M. , HODGSON J. M.
Published: July 2006

A computer program has been written in Fortran to translate coded soil profile data into conventional text. It reads data from 80‐column punched cards in fixed format. The data can be screened for their relevance to an inquiry, and the output can be adapted to the user's requirements. Standard codes, data specifications, and output layout are provided, but users who have special requirements can provide their own. One version of the program provides a more or less abbreviated translation with a tabular layout, the other gives complete descriptions in conventional text with punctuation.
SOIL NITROGEN
Authors: GASSER J. K. R. , KALEMBASAZ S. J.
Published: July 2006

Soils from experiments receiving various treatments in the field were used to investigate the effects of different amounts and forms of organic matter in a clay and a sandy soil on the inter‐correlations between several laboratory methods of measuring available‐N. The correlations between some of these measurements, and the growth and N uptake of ryegrass grown in the glasshouse with and without added fertilizer‐N were also investigated.

Seven clay soils and eight sandy soils were used, containing different amounts of organic matter of different kinds, as a result of various field treatments. For the sandy soils, one sample was taken from each plot of the experiment which allowed the effects of field variations on the values determined in the laboratory to be measured.

The correlations between methods of measuring available‐N showed that measurements obtained by aerobic incubation, anaerobic incubation, and nitrogen extracted by boiling water, correlated best with one another. These measurements also correlated best with the performance of ryegrass in the glasshouse.

N uptake by ryegrass from soils without fertilizer‐N always correlated better with measurements of available‐N than did dry matter produced. With added fertilizer‐N, dry matter correlated better with available‐N than did N uptake at the first cut but worse for the total of three cuts. Fertilizer‐N recovered in the grass at the first cut was significantly and negatively correlated with available‐N.

Values of available‐N from the individual samples of the sandy soil showed that those for aerobic incubation had the largest standard error and had the greatest range expressed as a per cent of the mean value, and those for nitrogen extracted by boiling water least error and range. All methods correlated similarly with the performance of ryegrass in the glasshouse. All three methods successfully identified the treatments giving most available‐N.
EFFECTS OF SOLUTION: SOIL RATIO ON PHOSPHATE SORPTION BY SOILS
Authors: HOPE G. D. , SYERS J. K.
Published: July 2006

Isotherms for the sorption of inorganic phosphate (P) by three contrasting soils during 40 h showed a dependence on solution: soil ratio. Above a final solution P concentration of 0.5 μg ml−1, more P was sorbed at a solution: soil ratio of 5:1 than at 40:1 for a given level of P in solution. With time up to 146 h, the effect of solution: soil ratio on P sorption was kinetically controlled.

Equilibrium solution P concentrations, estimated by extrapolation of the linear relationships between solution P concentration and the reciprocal of time to I/t= o (i.e. t=∞)appeared to be coincident for each solution:soil ratio at high and the low levels of added P. Consequently, sorption isotherms at equilibrium would be coincident, irrespective of the solution soil ratio used.

The kinetic control of solution: soil ratio on P sorption is interpreted in terms of the number of P sorbing sites and initial solution P concentration on the rate of P sorption by soils.
THE IDENTIFICATION AND DETERMINATION OF GLUCURONIC AND GALACTURONIC ACIDS IN SCOTTISH SOILS AND SOIL FRACTIONS USING ION‐EXCHANGE AND GAS‐LIQUID CHROMATOGRAPHY
Authors: MUNDIE C. M.
Published: July 2006

Two methods have been used for the identification and determination of uronic acids in soils and soil fractions. The uronic acids were released by hydrolysis with sulphuric acid. After partial purification by ion‐exchange chromatography they were separated either by further ion‐exchange or by gas‐liquid chromatography of derivatives. The latter method is preferable for determination of the specific activities of uronic acids in soil tracer work. Both galacturonic and glucuronic acids were detected in the four Scottish soils examined, the galacturonic acid being present in slightly greater amounts in each soil. Mannuronic acid was not detected. The total amount of uronic acids found ranged from about 4 mg to 6 mg/g soil.
A TOPOSEQUENCE OF ALPINE SOILS ON CALCAREOUS MICASCHISTS, NORTHERN ADULA REGION, SWITZERLAND
Authors: BUURMAN P. , VAN DER PLAS L. , SLAGER S.
Published: July 2006

On calcareous micaschists in the northern Adula Region, Switzerland, brown soils are formed under grasses and herbs at altitudes below 2000 m. Podzols occur below Ericaceae below 2000 m and are formed irrespective of vegetation above this altitude. Calcimorphic soils are not found.

Brown soils have a stable clay mineral association of chlorite and mica, while in the A horizons of podzols and in initial podzols alteration of chlorites to smectites occurs.
A COMPARISON OF FIELD ESTIMATES AND LABORATORY ANALYSES OF THE SILT AND CLAY CONTENTS OF SOME WEST MIDLAND SOILS
Authors: HODGSON J. M. , HOLLIS J. M. , JONES R. J. A. , PALMER R. C.
Published: July 2006

Field estimates of silt and clay contents were compared statistically with the silt (2‐60 μm) and clay (<2 μm) contents determined by the pipette method of 184 soil horizons from a large range of west Midland soils (clay contents 1–81 per cent and silt contents 3–71 per cent). Regression equations were calculated (a) for each of four surveyors using combined topsoil and subsoil data and (b) for surface and subsoils separately using combined data for the four surveyors. There is slight evidence of ‘operator bias’ and a tendency for all four surveyors to underestimate clay in surface horizons though these conclusions have limited significance because of the small number and the distribution of some of the sample populations. Single equations for the combined data from all operators and all horizons explained 75.5 per cent of the variation in field estimates of silt content and 85.4 per cent of the variation of clay estimates. For silt, the regression line almost passes through the origin with a slope not significantly different from unity, whilst for clay, the line intercepts the y‐axis close to zero and has a slope of 0.904. The results show that, with experience and adequate reference samples, surveyors can confidently estimate the particle‐size distribution of a wide range of soils. These studies were done during soil mapping in Staffordshire, Hereford and Worcester, and Salop using the newly introduced soil classification (Avery, 1973) and revised Handbook (Hodgson, 1974) of the Soil Survey of England and Wales.
VARIABILITY IN THREE AREAS OF THE DENCHWORTH SOIL MAP UNIT
Authors: BANFIELD C. F. , BASCOMB C. L.
Published: July 2006

This paper shows correlations between soil properties and uses multivariate techniques to investigate similarities between profiles in relation to substrata. It compares laboratory measurements and field observations as means of characterizing soils.

Correlations between two pH measurements and between fine clay and clay are large at all depths. Linear regressions indicate that close prediction of pH in water and fine clay content is possible from pH in CaCl2, and clay content respectively. Prediction of organic matter content from matrix Munsell colour value seems reliable within this limited range of soils. Field observation of carbonates correlates well with the laboratory measurement. Some indication of iron oxide content is given by matrix chroma.

Significance of observed horizonation is confirmed by two minimum spanning trees, based on field observations and on laboratory measurements, which each link the samples in a similar way. Mean similarities between depths show that depths 2 and 3 are most alike.

Inclusion of profiles on three different geological substrata under one series name is justified by the within‐ and between‐substrata similarities being alike, although profiles from each are not mixed at random.

Plots of the profiles relative to the axes obtained by principal coordinates analysis of laboratory measurements and field observations show remarkable agreement. Rotational fitting of these plots indicates little difference between the three substrata.
THE ADSORPTION OF POLYVINYL ALCOHOL ON GIBBSITE AND GOETHITE
Authors: KAVANAGH B. V. , POSNER A. M. , QUIRK J. P.
Published: July 2006

The neutral polymer, polyvinyl alcohol, has been shown to be adsorbed by the hydrated oxides gibbsite and goethite. A reduction in adsorption on gibbsite is observed when it is dried prior to the adsorption measurements. Evidence from electron microscopy suggests that this is caused by a reduction in the accessible surface area due to aggregate formation, rather than a change in the surface properties of the substrate. Changes in either the pH or the ionic strength of the medium do not significantly alter the amount of PVA adsorbed. Electrophoretic data indicate that the thickness of the adsorbed layer on both clays and oxides is in excess of 10 nm at high concentrations of polymer.
THE USE OF CATHODOLUMINESCENCE IN THE IDENTIFICATION OF SOIL MINERALS
Authors: DUDLEY R. J.
Published: July 2006

An apparatus, based on an optical microscope system, has been constructed for the subjective observation of cathodoluminescence, and the value of the technique has been determined for the examination of minerals and soils. The use of cathodoluminescence for the specific identification of minerals was found to be limited by the observation of different luminescent colours from the same minerals, and the same luminescent colour from different minerals. However, a sufficient variety of luminescent colours is believed to exist to allow the method to be used in conjunction with others for the identification of mineral grains. An examination of the trace element levels in a small group of mineral separates was found to be uninformative in trying to explain the variations in luminescent colours found.
RAINDROP IMPACT STRESS AND THE BREAKDOWN OF SOIL CRUMBS
Authors: GHADIRI H. , PAYNE D.
Published: July 2006

The stress produced by raindrop impact, calculated as the rate of change of momentum divided by area of contact, was found to be only partly satisfactory in studies of breakdown of paper tissue and soil crumbs. The calculated stresses for failure did not agree closely with values found by other methods, and varied systematically with raindrop size. The differences were related to the effect of duration of application of stress, and to the concentration of stress around the periphery of the drop.
ADSORPTION, DESORPTION AND SOLUBILITY RELATIONSHIPS OF LEAD AND CADMIUM IN SOME ALKALINE SOILS
Authors: SINGH BIJAY , SEKHON G. S.
Published: July 2006

In some alkaline soils of Punjab (India) the adsorption, desorption and solubility relationships of lead and cadmium were investigated and the results analysed by the Langmuir equation.

Both the metals are retained in soils by adsorption on mineral interfaces and interaction with organic matter and calcium carbonate. At high concentrations, these probably precipitate as hydroxides. Sequential desorption of Pb and Cd with 1 MKCI and 0.05 MCu(CH3COO)2 provided a measure of their exchangeable and chelated form.
ADSORPTION ON HYDROUS OXIDES. III. FULVIC ACID AND HUMIC ACID ON GOETHITE, GIBBSITE AND IMOGOLITE
Authors: PARFITT R. L. , FRASER A. R. , FARMER V. C.
Published: July 2006

Adsorption isotherms were obtained for fulvic and humic acids on synthetic gibbsite and goethite and on a natural imogolite. The results were interpreted with the help of spectra of the adsorption complexes, and measurements of hydroxyl displaced. The mechanism of adsorption involved ligand exchange with the surface hydroxyl groups and hydrogen bonding. The hydroxyl groups displaced included singly coordinated species on the (100) face of goethite and on the edge faces of gibbsite. The doubly coordinated hydroxyl groups on the (001) face of gibbsite were not replaced, and this face adsorbed only un‐ionized fulvic acid probably by a hydrogen bonding mechanism. Imogolite adsorbed most fulvic acid because of its high porosity. Only isolated places on its surface reacted with fulvic acid to form carboxylate groups.
ADSORPTION OF PHOSPHATE BY VARIOUS OXIDES: THEORETICAL TREATMENT OF THE ADSORPTION ENVELOPE
Authors: CABRERA F. , MADRID L. , DE ARAMBARRI P.
Published: July 2006

An explanation is put forward for the shape of adsorption envelopes found for phosphate adsorption by various metallic oxides. The equation xm= C1 (μH3PO4+μ∑anions) is proposed, where μH3pO4 is the chemical potential of undissociated H3PO4; μ∑anions is the chemical potential of all phosphate anions considered as one. component; C1 is a constant that includes influences of surface charge, chemical affinity of the metal for phosphate, specific surface area, etc., and xmis the calculated Langmuir maximum adsorption of P at each pH. The dependence of C1 on the metal present in the oxide is shown.
EFFECTS OF TILLAGE AND DIRECT DRILLING ON SOIL TEMPERATURE IN WINTER
Authors: HAY R. K. M.
Published: July 2006

Continuous records of soil temperature were collected at 1 cm and 5 cm depth during two winters (1972–4) in cultivated and uncultivated (direct drilling) soil. When solar radiation levels were low, the observed large and irregular fluctuations in soil surface temperature appeared to be associated with advective heat flow. The stubble mulch on the uncultivated soil insulated the surface layers from temperature variation, resulting in less soil freezing than cultivated soil and fewer hours above 5° C. Some implications of these findings for cultivations for cereals are discussed.
THE FRICTIONAL CHARACTERISTICS OF STEEL SLIDING ON SOIL
Authors: STAFFORD J. V. , TANNER D. W.
Published: July 2006

The frictional behaviour of soil‐steel interfaces has been investigated under controlled conditions in the laboratory. The description of the behaviour by a Coulomb‐type expression has been verified in the normal stress range 10–280 kPa. However the effect of normal stress on density and hence on adhesion must be considered. Soil moisture content can change interface friction by up to 50%, the effect increasing as sliding speed is reduced. These effects have been explained by considering inter‐particle cohesion.
A SIMPLE COMPUTER MODEL FOR LEACHING IN STRUCTURED SOILS
Authors: ADDISCOTT T. M.
Published: July 2006

A layer model for the movement of solutes in soil has been developed in which, as a working approximation, the soil solution is partitioned into mobile and retained phases. Only the mobile solution is displaced during water movement, and equilibrium is assumed to be established between the mobile and retained phases when flow ceases, giving holdback of solute. The model permits the displacement of the mobile solution through an indefinite number of layers when large amounts of rain fall. It can be assumed either that water and solute are stored in the bottom layer and can be withdrawn up the profile by evaporation or that they drain from the bottom layer. Predicted soil nitrate concentrations agreed reasonably well with those measured in a field experiment and indicated some sensitivity to layer thickness. The capacity of the model to predict concentrations in drainage is demonstrated.
CHEMICAL AND INFRARED SPECTROSCOPIC STUDIES OF FULVIC ACID FRACTIONS FROM A PODZOL
Authors: ANDERSON H. A. , FRASER A. R. , HEPBURN A. , RUSSELL J. D.
Published: July 2006

Infrared spectroscopy and chemical degradation indicated several fulvic acid fractions from an iron‐humus podzol capable of complexing and translocating metals. Acidic polysaccharides, some of them resembling pectic acid, were isolated in appreciable quantities. These are able to bind metals through carboxyl groups, but peptide components present in the polysaccharide fraction may provide alternative metal complexing centres. The high yield of acid‐extractable organic matter from the illuvial humus, together with its high content of carboxylic acid groups, make it likely that this fraction plays a major role in the translocation of metals. Phenolic compounds allegedly associated with this process were present in the fulvic acid solution in low amounts, and only in the extracts from the organic horizons.
FACTORS INFLUENCING THE RELEASE OF COPPER AND ZINC ADDITIVES FROM GRANULATED SUPERPHOSPHATE
Authors: GILKES R. J.
Published: July 2006

When copper sulphate and zinc oxide are granulated with ordinary superphosphate, insoluble copper phosphate and soluble zinc phosphate are formed. The copper phosphate has the approximate chemical composition NaCu6 H3 (PO4)5 Cl. 6H2O and a structure similar to that of the mineral sampleite. When such fertilisers are applied to soils the development of an acid phosphate solution within granules dissolves most zinc and some copper. Subsequently, diffusion and leaching release zinc and copper from within the granules.
VARIABILITY IN THREE AREAS OF THE DENCHWORTH SOIL MAP UNIT. III. SOIL GROUPING BASED ON CHEMICAL COMPOSITION
Authors: WILLIAMS C. , RAYNER J. H.
Published: July 2006

Data from a chemical determination of 21 elements plus seven Soil Survey routine laboratory measurements for three horizons of 30 soil profiles have been treated by multivariate techniques to find relationships and grouping of soil properties in soils mapped as Denchworth series.

The samples profiles were developed in parent materials of Oxford, Kimmeridge and Gault clay origin. The Oxford clay grouping was confirmed, but the Kimmeridge and Gault clay soils were better represented by three rather than two classes.
A REVIEW OF THE EFFECTS OF PESTICIDES ON MICROBIAL ACTIVITY IN SOILS
Authors: WAINWRIGHT M.
Published: July 2006

The paper reviews the recently published literature (mainly since 1970) on the effects of pesticides on the major biogeochemical cycles in soils, including transformations of carbon, nitrogen, phosphorus sulphur, trace elements and soil enzymes.

The main conclusion is that pesticides, with the exception of fumigants and some broad spectrum fungicides, have little deleterious influence on soil processes when applied at field rates.

Obvious gaps in our knowledge of pesticide‐soil interactions are pointed out and suggestions are made where future research is needed.

In the absence of effective biological control methods, the extensive use of pesticides in agriculture will continue. It is essential that the effects of these compounds on biochemical transformations in soils be determined, so that we can arrive at a balanced view of their effects on soil fertility.
CHLORIDE LEACHING IN THE ROTHAMSTED DRAIN GAUGES: INFLUENCE OF RAINFALL PATTERN AND SOIL STRUCTURE
Authors: ADDISCOTT T. M. , ROSE D. A. , BOLTON J.
Published: July 2006

Calcium chloride giving 253 kgClha−1 was applied to the 20‐inch and 40‐inch 1/1000 th acre drain gauges after drainage re‐started in 1974. It was tagged with 30Cl in the 40‐inch gauge. After two preliminary peaks in each gauge, chloride concentration was related to cumulative drainage in the 20‐inch gauge with an overall pattern of peak, decline and tail, interrupted by subsidiary peaks, whereas in the 40‐inch gauge it declined very slowly with marked fluctuations. Total chloride and 30Cl behaved similarly. A simple computer model simulated the main features of the relationship well for the 20‐inch gauge, but less satisfactorily in the 40‐inch gauge and only if water was assumed to move in a very small proportion of the clay in the lower half of the gauge. These simulations and some for model rainfall regimes suggested that the shapes of the relationships were greatly influenced by rainfall pattern and by retention of soil solution in fine pores during movement in larger pores. Possible effects of soil structure on leaching are discussed.
SOLUBILITY OF ALUMINIUM IN SOILS OF THE HUMID TROPICS
Authors: RHODES EDWARD R. , LINDSAY W. L.
Published: July 2006

Soil samples obtained from genetic horizons of an upland and acid sulphate soil of Sierra Leone, were equilibrated with 0.01 M CaCI using a 1:2 soil to solution ratio. Al3+ activity was estimated from total Al measured in the equilibrium extract, by accounting for hydrolysis and the formation of other complex species.

The Al3+ activity was pH‐dependent, but the Al(OH)3 ion product was I'airly constant throughout the upland soil profile; Al3+ activity was near that expected for equilibrium with kaolinite and quartz.

In the acid sulphate soil alunite appeared to control the activity of Al3+.
EFFECT OF TEMPERATURE AND SOIL DRYING ON THE TRANSFORMATION OF (14C) GLUCOSE IN SOIL
Authors: CHESHIRE M. V. , SPARLING G. P. , MUNDIE C. M. , SHEPHERD H. , MURAYAMA S.
Published: July 2006

Two different soils, either fresh, or dried and remoistened, were incubated with 1% labelled glucose for 28 days at about 20° or 5 °C and the transformation of the glucose to other sugars measured.

Xylose formed a much greater proportion of the sugars synthesized at low temperature in pre‐dried soil than in fresh soil, or at 20 °C in pre‐dried or fresh soil. Numbers of bacteria, fungi (including actinomycetes) and yeasts were determined for each type of incubation. Because the combination of conditions leading to xylose synthesis by yeasts in predried soil are unlikely in the natural state it is concluded that most soil xylose originates in the residues of plants.
EFFECTS OF CULTIVATION ON SOIL WATER RETENTION AND WATER USE BY CEREALS IN CLAY SOILS
Authors: GOSS M. J. , HOWSE K. R. , HARRIS W.
Published: July 2006

The effects are repotted of direct drilling and mouldboard ploughing on soil water retention and extraction in three soils over two to four years.

In the years 1972–75 when winter rainfall was close to or greater than the long‐term average the maximum soil water content of the upper 100 cm differed little between the cultivation treatments. In contrast, after the dry winter of 1975–76, about 10 per cent more water was stored in the direct‐drilled soil, especially below 50 cm. In the following dry summer, winter wheat extracted up to 22 mm more water from uncultivated soil and this was associated with better growth of the crop than after ploughing.

When simulated rain was applied, water infiltrated rapidly to a depth of 50–100 cm in direct‐drilled soil, whereas on ploughed land its movement was retarded below the plough sole even when cultivation had been carried out under conditions which minimized smearing. Water storage at depth was consequently greater under dry conditions in the direct‐drilled soil while excess water reached drain depth more rapidly in wet conditions.
PHENOLIC HYDROLYSIS PRODUCTS FROM GEL CHROMATOGRAPHIC FRACTIONS OF SOIL HUMIC ACIDS
Authors: TATE K. R. , ANDERSON H. A.
Published: July 2006

Humic acids extracted from the Bh horizon of a kauri (Agathis australis) podzol and the A horizon of a yellow‐brown earth under hard beech (Nothofagus truncata), both New Zealand soils, were fractionated by a ‘salt boundary’ technique using a dextran gel, and the fractions hydrolysed with 6 M hydrochloric acid. Lignin‐derived phenolic acids were analysed by gas chromatography of the ether‐soluble hydrolysis products of the humic acids.

The lignin derivatives from the kauri podzol humic acid are probably modern products derived from the present‐day scrub vegetation, whereas those from the yellow‐brown earth humic acid are derived from the deciduous vegetation.
THE RATE OF SOIL SURVEY IN BRITAIN
Authors: BECKETT P. H. T.
Published: July 2006

Typical rates of soil survey (area, length of boundary and number of observations per day or hour) are presented for routine surveys on 1:25,000 and 1:10,560 base maps by the Soil Surveys of Scotland, and of England and Wales, in five areas.

The distance a soil surveyor walks between observations sites each day is highly correlated with (Area surveyed x No. of observation sites).
PORE SPACE VARIABILITY IN A SUB‐SURFACE HORIZON OF TWO SOILS
Authors: MURPHY C. P. , BANFIELD C. F.
Published: July 2006

Image analysis was used to investigate the variability of pore space in soil thin sections. Two fine‐textured soil profiles (or pedons) were sampled by inserting eight Kubiena tins (7.5 × 6 × 4 cm) in ledges at 50 cm depth. From each soil block three horizontal thin sections (7.5 × 6 cm) were made and photographed. Each photograph was then divided into nine ‘frames’ so that the voids in each of these frames could be measured using the Quantimet 720 Image Analysing Computer.

The results show the variability of three specific pore‐space characters and the consequent need to sample a number of large thin sections from several sample blocks for each soil horizon to obtain estimates of sample means with suitable accuracy.
REACTIONS OF AMMONIA WITH SOIL II. SORPTION OF NH3 ON ENGLISH SOILS AND ON WYOMING BENTONITE
Authors: ASHWORTH J.
Published: July 2006

Sorption isotherms and heats of sorption of NH3 gas on soils, Wyoming bentonite and silica gel were measured at 27 °C after preliminary drying at 22°‐290 °C. Sorption of NMe3 was also measured on some of the materials.

Sorption on soils was not very sensitive to change in drying temperature, even though soil water content was markedly affected. Sorption on bentonite was dependent on drying temperature because this affected ease of lamellar separation.

The results suggest that under the conditions employed, NH3 sorption on the English soils studied is predominantly due to its protonation at pH‐dependent charge sites and partly to co‐ordination with exchangeable Mg or Ca (but not Na or K). Sorption through mechanisms involving hydrogen bonding is apparently negligible.
REACTIONS OF AMMONIA WITH SOIL, III SORPTION OF AQUEOUS NH3 BY HOMOIONIC SOIL CLAYS
Authors: ASHWORTH J. , PYMAN M. A. F.
Published: July 2006

Homoionic clay suspensions were equilibrated at 25°C with aqueous NH, (0.01 to 0.30 M) by agitating for several days. Using clays extracted from three different soils, sorption of NH3, measured by titration, followed the order Na > Ca > NH4 ‐clay. The difference in NH3 sorption between Na‐clay and NH4 ‐clay was matched by an increase in Na + ion concentration in the aqueous phase of suspensions of Na‐clay treated with NH3, but there was no such effect with Ca‐clay.

Sorption of NH3 on NH4 ‐clay in aqueous suspension is considered due to proton donation at sites of pH‐dependent charge, and the additional sorption on Na‐clay to displacement of Na + by NH4+ ions. The additional sorption on Ca‐clay seems largely due to co‐ordination of Ca2+ ions with molecular NH. Exchangeable cations affect NH3 sorption differently when an aqueous phase is present than when dried homoionic materials are treated with NH3 gas.
EFFECTS OF solUTION: SOIL RATIO AND VIGOUR OF SHAKING ON THE RATE OF PHOSPHATE ADSORPTION BY SOIL
Authors: BARROW N. J. , SHAW T. C.
Published: July 2006

The effects were measured of varying the solution: soil ratio, and the vigour of shaking on the rate of adsorption of phosphate. One soil appeared to break down with vigorous shaking, prior to adding phosphate, especially at low solution: soil ratio. As a result, subsequent phosphate adsorption was faster. With gentle shaking, there was no effect of solution: soil ratio with the soil. Another soil was more stable and there were only small differences due to vigour of shaking and no effect of solution: soil ratio with any method of shaking.

The change in phosphate concentration was not proportional to the reciprocal of time as reported by Ryden and Syers (1975) and Hope and Syers (1976). Hence the validity of extrapolating from short sections of reciprocal‐time graphs in order to estimate equilibrium is questioned.
EFFECTS OF BENOMYL ON IRON AND MANGANESE REDUCTION AND REDOX POTENTIAL IN FLOODED SOIL
Authors: PAL SUDHANSU S. , SUDHAKAR‐BARIK  , SETHUNATHAN N.
Published: July 2006

Benlate (50 per cent wettable powder), the commercial formulation of the systemic fungicide benomyl, was applied to a flooded alluvial soil at concentrations of 5 to 100 μg/g active ingredient. At about the field application rate (S μg/g), benomyl retarded the decrease in the redox potentials of the flooded soil and curtailed the accumulation of iron and manganese in solution, both without and with added rice straw (0.5 per cent).
COMPARISON OF MEASURED AND PREDICTED SOIL MOISTURE DEFICITS
Authors: HALL D. G. M. , HEAVEN F. W.
Published: July 2006

The moisture regimes of two fen soils and two chalk soils in Lincolnshire were investigated using a neutron probe moisture meter. Soil moisture deficits were calculated and compared with those predicted using meteorological data. Measured deficits were in fairly close agreement to those predicted by two separate models, the main variation seeming to depend upon the dryness of the year, the crop and the soil type.

Measured deficits were also compared with laboratory estimates of available water and it was found that the chalk soils dried to higher suctions than was at first expected.
OXYGEN CONCENTRATIONS IN A CLAY SOIL AFTER PLOUGHING OR DIRECT DRILLING
Authors: DOWDELL R. J. , BURFORD R.CREES.J. R. , CANNELL R. Q.
Published: July 2006

The concentration of oxygen at three depths (15, 30 and 60 cm) has been measured in a direct‐drilled or ploughed clay soil of low hydraulic conductivity (Evesnam series) which was cropped with winter wheat in three consecutive growing seasons (1972/73 to 1974/75). The mean oxygen concentrations between January and March varied with the seasonal rainfall; in the relatively dry winter of 1972/73they were 20 per cent (v/v) at 15 cm and 12 per cent (v/v) at 60 cm, but in the wetter winters of 1973/74 and 1974/75 they were less than 11 and 6 per cent (v/v) at 15 and 60 cms respectively. Direct drilling resulted in higher oxygen concentrations at 15 cm than ploughing in both wetter winters, the mean concentration being 10.2 and 7.2 per cent (v/v) in direct‐drilled and ploughed plots respectively. Frequency distributions of values obtained at individual sampling points showed that when the mean oxygen concentration of the soil at 15 cm decreased to its annual minimum (in January‐March), a significantly higher proportion of the sampling points under direct drilling continued to show concentrations of oxygen greater than 10 per cent (v/v).

The results are interpreted as indicating that the higher oxygen concentrations found in this soil after direct drilling are due to the development of a system of continuous large pores and channels which would otherwise be destroyed by annual ploughing.
STRUCTURAL STUDIES ON SOIL POLYSACCHARIDE
Authors: CHESHIRE M. V. , BRACEWELL J. M. , MUNDIE C. M. , ROBERTSON G. W. , RUSSELL J. D. , FRASER A. R.
Published: July 2006

The polysaccharide extracted by alkali from a Countesswells series soil has been fully methylated and the hydrolysis products identified by GC‐MS. The parent neutral sugars are galactose, glucose, mannose, arabinose, xylose, fucose and rhamnose and these constitute about 40 per cent of the polysaccharide. The analysis shows that hexose components are predominantly present in 1 → 3 and 1 → 4 linkages and pentose sugar in 1 → 4 linkages. About 20 per cent of the residues were in branching positions.

From the number of non‐reducing terminal groups present the average molecular weight of the methylated material has been calculated to be about 1460 compared with a value of 2700 obtained by vapour pressure osmometry. This contrasts with much higher values reported for unmethylated soil polysaccharides.

The mixture of derivatives obtained supports the concept that soil polysaccharide originates in both plants and microorganisms.
SYNTHETIC ALLOPHANE AND IMOGOLITE
Authors: WADA S.‐I. , ETO A. , WADA K.
Published: July 2006

In order to prepare allophane and imogolite in the laboratory, solutions containing l–2× 10–3 M orthosilicic acid and 4–0.5 × 10–3 M A1C13 (SiO2/Al2O3 molar ratio; 0.5, 1.0, 2.0, 4.0 and 8.0) were heated at 95–100°C for 113 hours after addition of NaOH (NaOH/Al molar ratio; 1.0, 2.0, 2.8 and 3.0). Boehmite was found in the precipitates from all solutions with initial SiO2/Al2O3 ratios of 0.5. Imogolite was found with allophane II in the products from solutions with SiO2/Al2O3 ratios of 1.0 or greater and with NaOH/Al ratios of 2.8 or less (final pH 5.0), whereas allophane I was found in the precipitates from solutions with the same SiO2/Al2O3 ratios but with the NaOH/Al ratio of 3.0 (final pH = 5.0–6.3). The mode of formation, chemical composition, infrared spectra, electron micrographs, electron diffraction patterns and differential thermal analysis curves of synthetic imogolite and allophanes (I and II) were compared with those of their natural counterparts.
A CRYSTALLINITY INDEX FOR SOIL KAOLINS AND ITS RELATION TO PARENT ROCK, CLIMATE AND SOIL MATURITY
Authors: HUGHES J. C. , BROWN G.
Published: July 2006

To sub‐divide the large group of kaolinitic soil clays a new empirical index of crystallinity was obtained from the X‐ray diffraction patterns of eight standard kaolins. The index used is the ratio of the intensity above background of the peak at 4.46Å to the intensity above background at about 2.43Å (43.2° 2θ CoKα) and ranges from 4.8 for halloysite to 83 for a well‐ordered triclinic kaolinite. For the kaolins from a group of soils from S.W. Nigeria, the ratio lies between 4.3 and 13.7 and can be tentatively related to the presence of weatherable minerals in the soil and/or the length of the dry season.
EFFECTS OF DIFFERENT METHODS OF CULTIVATION AND DIRECT DRILLING, AND DISPOSAL OF STRAW RESIDUES, ON POPULATIONS OF EARTHWORMS
Authors: BARNES B. T. , ELLIS F. B.
Published: July 2006

Numbers of earthworms collected from direct‐drilled or ploughed land were studied during successive years on contrasting soil types sown with cereals.

Samples were taken in autumn using a combination of chemical expulsion and hand sorting of soil. The population was consistently larger on direct‐drilled than on ploughed land, and the difference became greater in each successive year. Deep burrowing species were affected similarly to the population as a whole. Population differences on the two treatments were greater with spring — than autumn ‐ sown crops. After tine cultivation numbers were usually similar to those after ploughing.

On a direct‐drilled clay soil on which straw had been either burned, or chopped and spread, no differences were recorded in the overall population. However, significantly larger numbers of deep burrowing species were found on the chopped and spread areas, whereas on the burned areas numbers of Allolobophora chlorotica were significantly greater.
SELECTIVE EXTRACTION OF AMORPHOUS IRON OXIDES BY EDTA FROM A DANISH SANDY LOAM
Authors: BORGGAARD O. K.
Published: July 2006

EDTA extracts (pH 7.5–10.5) from a Danish sandy loam showed no significant (95% level) increase in amounts of aluminium, calcium, iron, and magnesium between three and nine months' shaking. The amounts were independent of the soil: solution ratio (1:10–1:50), the EDTA concentration (0.01 M–0.2 M), and crushing the soil (< 0.25 mm or < 2 mm). IR spectroscopy and X‐ray diffraction showed no change in the mineral composition of the soil during the extraction. The extracted iron was equal to that extracted after 2 h by ammonium oxalate at pH 3.0. EDTA extraction at pH > 7.5 seems to extract selectively iron oxides with solubility products > ∼ 10−41.
UV AND VISIBLE ABSORPTION SPECTROSCOPIC INVESTIGATIONS IN RELATION TO MACROMOLECULAR CHARACTERISTICS OF HUMIC SUBSTANCES
Authors: GHOSH KUNAL , SCHNITZER M.
Published: July 2006

Humic substances were investigated by both UV and visible absorption spectroscopic methods with special emphasis on their macromolecular characteristics. The spectral ranges examined were 200–350 nm and 350–700 nm. Conclusions were drawn on the basis of absorption intensities in optical density (O.D.) vs. wavelength (λ) curves, slopes of log O.D. vs. log λ plots, nature of shoulders in the 250–270 nm region, and E4/E6 ratios. As macromolecular characteristics are expected to be dependent on the medium, studies were carried out at different pH values as well as at different neutral salt concentrations, the two major parameters influencing the soil environment.

It was noted that with increasing neutral electrolyte concentrations, the particle size decreased, probably due to the coiling of the macromolecule.

On increasing the pH from 6.5 to 9.5, the particle size increased slightly, possibly because of partial association through homolytic bonding. At pH 3.5 (with FA only), the degree of association was greater than that at pH 9.5. However, here association occurred by a different mechanism, that of intermolecular hydrogen bonding. At pH 2.0 (with FA only), association was markedly pronounced because of the very dominant role played by intermolecular hydrogen bonding.
RELATION OF SEVERAL PEDOLOGICAL CHARACTERISTICS TO ENGINEERING QUALITIES OF SOIL
Authors: DE LA ROSA D.
Published: July 2006

An attempt to predict engineering qualities which are needed in soil evaluation and to enhance nonagricultural use of soil survey data was made. Data from a variety of soils were subjected to simple correlation and multiple regression analyses to relate three pedologic characteristics: clay content, cation‐exchange capacity (CEC), and organic matter content to two engineering qualitites: plasticity index, and optimum moisture. Simple correlation coefficients showed that clay content and CEC correlated significantly with the engineering determinations. The relationship between organic matter content and these engineering determinations was weaker. Multiple regression analyses showed that the three pedologic characteristics accounted for most of the variation in each of the engineering qualities, and that prediction was feasible.
THE PLASTIC LIMIT, AS DETERMINED BY THE DROP‐CONE TEST, IN RELATION TO THE MECHANICAL BEHAVIOUR OF SOIL
Authors: CAMPBELL D. J. , STAFFORD J. V. , BLACKWELL P. S.
Published: July 2006

The variation with water content is examined of soil cohesion, soil‐metal friction, susceptibility to soil compaction, implement draught and the slope and intercept of the virgin compression line of critical state soil mechanics theory. For a given soil, all these relations are shown to exhibit turning points at a similar water content which corresponds to the cone penetrometer plastic limit, as determined with a drop‐cone penetrometer, rather than the Casagrande plastic limit. The cone penetrometer plastic limit, which can also be more reliably determined than the Casagrande plastic limit, is the better indicator of soil behaviour in the field and of the water content at which the soil changes from the brittle to the plastic state.
A LYSIMETER STUDY USING NITROGEN‐15 ON THE UPTAKE OF FERTILIZER NITROGEN BY PERENNIAL RYEGRASS SWARDS AND LOSSES BY LEACHING
Authors: DOWDELL R. J. , WEBSTER C. P.
Published: July 2006

Perennial ryegrass growing in monolith lysimeters and treated with 400 kg N ha‐1 as calcium nitrate labelled with nitrogen‐15 (10.5 atoms per cent), during one growing season recovered between 43 and 54 per cent of the fertilizer nitrogen. In the following year without further nitrogen additions 4.6–9.5 per cent was taken up, whilst in the fifth year the recovery was less than 1 per cent. The contribution of non‐fertilizer sources of nitrogen to the total nitrogen taken up by the plants during the season that nitrogen was applied was estimated using tracer methods to be about 13–14 g N m‐2 year‐1. The estimate from measuring the nitrogen content of an unfertilized sward was 7 g N m‐2 year‐1. The residual effects of a fertilizer application are likely to be detectable for a period of between 6 and 9 years.

Losses of nitrogen to drainage in the winter after application represented 2–5 per cent of the fertilizer applied, whilst in subsequent years the amounts did not exceed 0.1 per cent. Mean concentrations of nitrate ranged between 4 and 16 mg N I‐1. Fertilizer contributed about 60–70 per cent of the total nitrogen lost in the first winter after nitrogen application and 45–60 per cent averaged over three winters.
THE EFFECTS OF GRINDING ON MICROBIAL AND NON‐MICROBIAL ORGANIC MATTER IN SOIL
Authors: POWLSON D. S.
Published: July 2006

Grinding more than doubled the respiration rate of two silt loam soils, one arable and one grassland. The increases were smaller when the grinding treatment was given to portions of soils that had previously been fumigated with CHCI3and incubated, a treatment that greatly decreased microbial biomass.

The results indicate that the flush of decomposition caused by grinding was in part derived from killed organisms and in part from enhanced decomposition of non‐biomass sections of the soil organic matter. Grinding killed about a quarter of the biomass in both soils. Carbon from killed organisms accounted for a quarter of the extra CO2–C evolved after grinding in the arable soil and almost half in the grassland soil. The extra non‐biomass organic matter decomposing after grinding amounted to about 0.5% of the soil organic carbon in both soils. This non‐biomass material rendered decomposable by grinding had a higher C/N ratio than the organic matter decomposing in unground soil.
CLAY AND SILT MINERALOGY OF SOME SOILS FROM QASIM, SAUDI ARABIA
Authors: MASHHADY A. S. , REDA M. , WILSON M. J. , MACKENZIE R. C.
Published: July 2006

Qasim, some 500 km north‐west of Riyadh, is one of the agriculturally important areas of Saudi Arabia. Silt fractions of the soils of the Wadi ar Rimah and side wadis, classified as Torrifluvents, are characterized by high quartz contents and the universal occurrence of kaolinite and felspar, generally with plagioclase predominant; mica, chlorite and hornblende also generally occur. The clay fractions contain mainly palygorskite and a smectite‐mica interstratification with smaller amounts of kaolinite, traces of quartz and occasionally chlorite. Palygorskite generally increases in content with depth. Variations in mineralogy probably reflect changes in depositional conditions rather than pedogenic processes; possible reasons for the high palygorskite content are discussed. Sedentary soils (Torriorthents) reflect the mineralogy of the rock from which they were derived. In clay fractions from salt‐marsh soils (Salorthids) calcite reacts strongly with smectite‐mica during DTA.
A SIMPLE MODEL FOR PREDICTING THE EFFECTS OF LEACHING OF FERTILIZER NITRATE DURING THE GROWING SEASON ON THE NITROGEN FERTILIZER NEED OF CROPS
Authors: BURNS I. G.
Published: July 2006

The model is based on the concept that there is an effective rooting depth above which all the inorganic N in the soil is equally available and below which all N is totally unavailable. The extent to which nitrate is leached below this depth is calculated from the excess rainfall over evapotranspiration and the water holding capacity of the soil.

The model was tested against the results of N fertilizer experiments with lettuce, French beans and overwintered onions which had been carried out in at least 2 years (and often more) on adjacent sites of the same field. The yields from all of the experiments with each crop were plotted against the level of fertilizer applied and against the difference between that applied and that lost by leaching. Comparison of these graphs showed that correcting for leaching in this way greatly reduced the variability between the response curves. The model was also tested against the results of similar experiments with Brussels sprouts grown on different sites with different combinations of base and top dressing. The results showed that the poor response to top dressing could be explained by the relatively small amounts of N in the base dressing which were leached from the rooting zone of this crop.

It appears that the model will enable worthwhile adjustments in N fertilizer dressings to be made for differences in rainfall, provided that leaching occurs during the early stages of crop growth when uptake is small.
A SIMPLE MODEL FOR PREDICTING THE EFFECTS OF WINTER LEACHING OF RESIDUAL NITRATE ON THE NITROGEN FERTILIZER NEED OF SPRING CROPS
Authors: BURNS I. G.
Published: July 2006

A model is described for predicting the amounts of nitrate residues remaining in the soil in the autumn and the extent to which these are lost by leaching during the winter. It is used to predict the effects of winter rainfall on the growth of spring crops. The model is based on the assumption that any nitrate which remains in the effective rooting zone of the spring crop after the winter will be equally available and any nitrate leached below it will be totally unavailable. The losses of nitrate were estimated from the excess rainfall and the water holding capacity of the soil.

The model was tested against the results of published N response experiments in the Netherlands and the UK. It predicted the differential effects of winter rainfall with reasonable accuracy, but tended to overestimate the spring nitrate contents observed in the Dutch experiments and underestimate those for the English data. These deviations appeared to be associated with errors in the estimation of the amounts of nitrate remaining in the soil in the autumn.

With certain reservations, the model would appear to provide helpful advice for adjusting spring fertilizer dressings for the effects of differences in winter rainfall.
THE WATER BALANCE OF AN AGRICULTURAL CATCHMENT II. CROP EVAPORATION : SEASONAL AND SOIL FACTORS
Authors: McGOWAN M. , WILLIAMS J. B.
Published: July 2006

Rates of evaporation, soil water deficits and extraction depths for spring cereals and grass were estimated from soil water measurements for a four year period. Estimates of evaporation were also compared with evaporation formulae and evaporimeter values.

Evaporation and soil water deficit were highly dependent upon weather, particularly rainfall. Evaporation from grass was noticeably restricted whenever deficits exceed 50 millimeters. Cereals extracted water from a slightly greater depth of soil but developed deficits, up to harvest, very similar to those under grass. Deficits developed in sand and clay soils were also very similar, because water held in large dense clay aggregates is not readily accessible to roots.

Although soil type had only minor influence on rates of evaporation, deficits and depths of drying, because of movement of water through fissures, slow drainage and delayed swelling effects soil type has a strong influence on stream behaviour.