bluuebunny/crossref_metadata_2025 huggingface dataset:
KINETICS OF ION EXCHANGE IN SOIL ORGANIC MATTER. IV. ADSORPTION AND DESORPTION OF Pb2+, Cu2+, Cd2+, Zn2+ AND Ca2+ BY PEAT
Authors: BUNZL K. , SCHMIDT W. , SANSONI B.
Published: July 2006

The equilibria as well as the rates of adsorption and desorption of the ions Pb2+, Cu2+, Cd2+, Zn2+, and Ca2+ by soil organic matter were determined in batch experiments as a function of the amount of metal ions added to an aqueous suspension of HCl‐washed peat. Simultaneous determination of the metal ions and hydrogen ions in the solution by atomic absorption spectrophotometry and pH‐measurements showed that the adsorption of one divalent metal ion by peat was coupled with the release of two hydrogen ions. Since this equivalent ion‐exchange process causes a corresponding increase of the electric conductivity of the solution, the rates of the adsorption and desorption processes were determined by an immersed conductivity electrode.

The distribution coefficients show that the selective order for the metal adsorption by peat is Pb2+ > Cu2+ > Cd2+≌ Zn2+ > Ca2+ in the pH range of 3·5 to 4·5. The slope of ‐2, as observed in a double logarithmic plot of the distribution coefficients versus the total solution concentration confirms the equivalence of the ion‐exchange process of divalent metal ions for monovalent H3O+ ‐ions in peat. The absolute rates of adsorption, as well as the rates for the fractional attainment of the equilibrium, increase with increasing amounts of metal ions added. This behaviour is also observed for the subsequent desorption of the metal ions by H3O+‐ions. At a given amount of metal ions added, the absolute rates of adsorption decrease in the order Pb2+ > Cu2+ > Cd2+ > Zn2+ > Ca2+, while the rates for the fractional attainment of the equilibrium decrease in the order Ca2+ > Zn2+≌ Cd2+ > Pb2+ > Cu2+. The half times for adsorption and desorption were in the range of 5 to 15 sec.
INFLUENCE OF SOIL PROPERTIES ON ADSORPTION OF PESTICIDE‐DERIVED ANILINE AND p‐CHLOROANILINE
Authors: MOREALE A. , VAN BLADEL R.
Published: July 2006

Soil properties were significantly related to the adsorption of aniline and p‐chloroaniline, greater adsorption always occurring with p‐chloroaniline. Multiple regression analysis indicated that the organic matter plus available water (or clay) was better than the simple linear relationship, with organic matter alone. The resulting equations accounted for most of the variability in aniline or p‐chloroaniline adsorbed (R2= 0·92 and 0·94, respectively). The contribution of organic matter to the adsorption was calculated as 79 and 77 per cent for aniline and p‐chloroaniline.

Experimental data on partially oxidized soils emphasized the major role played by soil organic matter. The variability in adsorption was mainly due to the organic matter left after oxidation (R2= 0·72 and 0·64 for aniline and p‐chloroaniline). No other combinations of variables significantly improved these relationships.
A TITANIUM‐RICH SOIL CLAY
Authors: BAIN D. C.
Published: July 2006

A peaty podzol developed on glacial drift derived from chlorite‐schists near Loch Awe, Argyll, contains up to 25 per cent titanium dioxide in the clay fractions after removal of organic matter and free iron oxides. Electron microscopy reveals that this titanium is almost entirely in the form of cryptocrystalline anatase which is amorphous to X‐rays and which is removed by the HF method normally used to concentrate anatase and rutile in soils. The anatase has probably formed as a result of the weathering of sphene.
RECONNAISSANCE FOR SOIL SURVEY. II. PRE‐SURVEY ESTIMATES OF THE INTRICACY OF THE SOIL PATTERN
Authors: BECKETT P. H. T. , BIE S. W.
Published: July 2006

The best procedure for mapping the soils of an area, and the effort this will require, depend upon the intricacy of its soil pattern.

This paper presents one way of describing such intricacy‐by a graph of variance against area sampled‐and an exploratory attempt to determine its form for OM, N, coarse and fine sand, silt, clay, gravel, available P and K, CEC, exch. Ca, Mg and K, in areas in the Northern Territory of Australia. This confirmed that there are considerable differences between the graphs for different properties and that areas differ very much in the short‐ and long‐range contributions to the total variability of their soil. It demonstrated the inevitable sampling problems in determining the form of variance‐area graphs.
CHANGES IN THE STRUCTURE OF MARSH SOILS FOLLOWING DRAINAGE AND ARABLE CULTIVATION
Authors: Dent D. L. , Downing E. J. B. , Rogaar H.
Published: July 2006

Measurements of apparent density (dry bulk density) have been used to monitor structural change in gleyed alluvial soils in Norfolk following drainage and cultivation. In Waveney series silty clay loam, drained for 9 years, soil ripening has been the dominant pedological process. Apparent density has increased throughout the drained profile due to loss of water and consequent structural rearrangement. In silty clay loam alluvium, reclaimed from the Wash over a 120‐year period, soil ripening appears to be terminated after 40 years but, under continuous arable use, apparent density continues to increase in, and immediately below, the plough layer. This increase in density is accompanied by a decline in the organic‐matter content of the plough layer.
SULPHUR, CARBON, AND NITROGEN CONTENTS OF ORGANIC FRACTIONS FROM ACETYLACETONE EXTRACTS OF SOILS
Authors: SCOTT N. M. , ANDERSON G.
Published: July 2006

Ultrasonic dispersion of acid‐pretreated soils in aqueous acetylacetone at pH 8, and at a solvent: soil ratio of about 45: I, extracted from 61 to 97 per cent of the organic sulphur from five Scottish soils. Narrowing the ratio to about 9:1 reduced the proportion extracted but was more convenient for the subsequent isolation of the organic components. Gel permeation chromatography of the extracts yielded materials containing from 14 to 60 per cent of the soil organic sulphur. Most of the soils gave four distinct fractions which contained from 21 to 38 per cent carbon, 0.2 to 2.1 per cent nitrogen, and 0.1 to 0.8 per cent sulphur. There was no consistent similarity between corresponding fractions of the various soils. Considerable amounts of iron and aluminium were extracted, presumably incorporated in organic complexes. Since they were obtained under very mild conditions, the fractions should provide useful starting materials for qualitative investigations on the nature of soil organic sulphur.
THE OCCURRENCE OF COPPER‐PORPHYRIN COMPLEXES IN SOIL HUMIC ACIDS
Authors: GOODMAN B. A. , CHESHIRE M. V.
Published: July 2006

Electron paramagnetic resonance (e.p.r.) spectroscopy has been used to show that humic acids, which were isolated from a range of soils and from which most of the iron was removed by boiling with hydrochloric acid, contain copper in the form of porphyrin complexes. The amounts of porphyrin‐bound copper in the acid‐boiled humic acids were estimated to be ≤ 20 mg/kg (equivalent to 0.05‐0.9 mg/kg in the soils). The acid‐boiled humic acids from cultivated mineral soils showed no great capacity for further uptake of copper as copper porphyrin when treated with CuSO4, most of this additional copper being held by groups not involving N‐donor groups. In contrast, copper treatment of the acid‐boiled humic acid from a raised bog peat produced a large increase in copper‐porphyrin signal strength, indicating that in the peat there are considerable amounts of porphyrin by which added copper could be complexed. It is suggested that porphyrin groups may be involved in the fixation of copper by organic matter in soils.
THE PEDOGENESIS OF SOME GIBBSITIC SOILS FROM THE SOUTHERN UPLANDS OF SCOTLAND
Authors: WILSON M. J. , BOWN C. J.
Published: July 2006

The mineralogy of ten profiles developed from hornfelsic rocks on the summit areas of the Merrick and Kells Hills has been investigated by X‐ray powder diffraction, thermal, infra‐red, and optical methods.

The soil clays of the C horizons of all profiles contain 6 to 37 per cent of gibbsite but this mineral is not found in the A horizons. Optical observations reveal that gibbsite is associated with hematitic rock fragments which are considered to represent older soil material–i.e. are pedorelicts. It is suggested that the Merrick soils are polygenetic and consist of two soil stratigraphic units, recent pedogenic effects being superimposed on a basal horizon that has been strongly influenced by preglacial or interglacial weathering.
THE IDENTIFICATION OF A BURIED PALEOSOL DEVELOPED IN PLACE AT PITSTONE, BUCKINGHAMSHIRE
Authors: VALENTINE K. W. G. , DALRYMPLE J. B.
Published: July 2006

A small scarp foot valley cut in blocky Coombe rock contained three layers of calcareous material which had been washed into it, the middle one of which was soil material. Mineralogical analyses showed that there was a lithological discontinuity immediately beneath the soil material but not above it. It seemed possible that there had been a complete inversion of soil horizons by successive erosion phases upslope and deposition in the valley bottom.

Micromorphological analyses showed that the particular arrangement of soil fabric in three profiles due to decalcification, gleying, and the reorganization of clay plasma varied logically according to slope position and inferred water regimes. The soil, although thin, had been developed in place. Charcoal flakes from the soil gave a radiocarbon date of 3910±220 years BP. The material that buried the soil is a combination of slopewash and ploughwash initiated by man's clearance and cultivation of the land begun in the late Neolithic or early Bronze Age.
IMPROVING A RECONNAISSANCE SOIL CLASSIFICATION BY MULTIVARIATE METHODS
Authors: BURROUGH P. A. , WEBSTER R.
Published: July 2006

An initial reconnaissance classification was difficult to use in soil survey in south‐west Sabah, East Malaysia, because the most commonly occurring classes of soil (subdivisions of Orthic Acrisols in the FAO/UNESCO Soil Map of the World Legend) could not be distinguished consistently. Principal component, similarity, and canonical variate analyses showed that the classes that were originally thought to be desirable overlapped almost completely with respect to profile characters and chemical properties determined by routine analysis. New guidelines for classification were devised, and class overlap was minimized by reallocating profiles using multiple discriminant analysis. The final classification of the Orthic Acrisols represented a gradation from profiles containing fresh rock fragments and weatherable minerals to those containing none. Some of the last occurred on strongly pre‐weathered sandstone; elsewhere they provided the main evidence for the remnants of a Pliocene land surface. To use the new classification consistently, estimates of total magnesium, potassium and phosphorus had to be included in routine chemical analyses. The revised classification was used successfully in subsequent reconnaissance survey work in south‐west Sabah.
MAGNETIC SUSCEPTIBILITY OF THE SOIL AND ITS SIGNIFICANCE IN SOIL SCIENCE – A REVIEW
Authors: MULLINS C. E.
Published: July 2006

The magnetic susceptibility of soil minerals is discussed, and in particular that of the ferrimagnetic minerals, maghemite, magnetite, and the titanomagnetites since one or more of these usually dominates soil magnetic properties. The magnetic susceptibility of soil depends on the shape, size, and concentration of these minerals as well as on the method of measurement. Measurements performed in a weak alternating magnetic field are the most reliable.

The identification, formation, and occurrence of soil maghemite is considered in detail since it is usually of pedogenic origin and occurs in (magnetically) detectable amounts in most soils. Moderate concentrations (>1 per cent) of magnetite or titanomagnetite in soils may be accurately measured if some of the material is first magnetically separated and its susceptibility determined. An example is given of the use of susceptibility measurements. Pedogenic maghemite may be determined in soils developed from parent materials of low susceptibility. A very rough value of 8.8 × 10−4 m3 kg−1 is suggested for the mass susceptibility of such maghemite (excluding magnetic concretions).

Although susceptibility has been suggested as an indicator of soil forming processes, this is only possible within an area containing fairly uniform parent material.
COMPUTER SIMULATION OF LOSS OF FERTILIZER NITROGEN THROUGH CHEMICAL DECOMPOSITION OF NITRITE
Authors: LAUDELOUT H. , GERMAIN L. , CHABALIER P. F. , CHIANG C. N.
Published: July 2006

An estimate is given of nitrogen losses which could occur through chemical decomposition of nitrite formed by nitrification of ammonium in acid tropical soils. Experiments on the rate of disappearance of nitrite were carried out in acid buffers as well as in soil samples. Numerical solutions of a system of differential equations describe the nitrification process and the chemical denitrification reaction. Up to 50 per cent of added ammonium nitrogen may be lost in an acid soil when nitrification occurs at temperatures prevailing in the humid tropics.
A COMPARISON OF THE POLYCARBOXYLIC ACIDS EXTRACTED BY WATER FROM AN AGRICULTURAL TOP SOIL WITH THOSE EXTRACTED BY ALKALI
Authors: LINEHAN D. J.
Published: July 2006

Humic and fulvic acids were isolated from an agricultural soil by conventional means. The same soil was extracted with water and the organic matter freed of inorganic and low molecular weight substances. The usual chemical differences between humic acid and fulvic acid were confirmed and the water extract was shown to resemble fulvic acid quite closely. Further fractionation of the fulvic acid and water extract showed that the elemental composition, carboxyl and acidic hydroxyl contents, molecular weights, and infrared spectra of the purified polycarboxylic acids were virtually identical. Both promoted the same growth response in cultured isolated tomato roots.

It is suggested that the qualitative similarity of fulvic acid to the polycarboxylic acid extracted by water justifies the use of the more easily isolated fulvic acid in physiological experiments on the direct effects on plants of soil organic matter.
STUDIES ON THE DECOMPOSITION OF PLANT MATERIAL IN SOIL. V. THE EFFECTS OF PLANT COVER AND SOIL TYPE ON THE LOSS OF CARBON FROM14C LABELLED RYEGRASS DECOMPOSING UNDER FIELD CONDITIONS
Authors: JENKINSON D. S.
Published: July 2006

Ryegrass uniformly labelled with 1
4C was allowed to decompose for 10 years under field conditions in a range of contrasting soils. The amount of organic matter already in a soil had no effect on the retention of labelled C by that soil, nor had a variation in soil pH of from 4.9 to 8.1. Decomposition was initially slower in a strongly acid soil (pH 3.7) but by the end of 5 years the difference between this soil and the others had almost disappeared. The more clay in a soil, the greater the retention of labelled C over the whole 10 year period; this was true of both strongly acid and near‐neutral soils. More labelled organic matter was leached from a soil containing 7.6% clay than from one with 17.5% clay, but the amount thus lost was insufficient to account for the difference in retention of C by the two soils. The decomposition of labelled plant material was faster in bare soil than in soil growing grass but the ‘protection’ thus given to the labelled C by the growing grass ended when the grass was removed.

In bare soil about one third of the labelled ryegrass C was left after one year but thereafter decomposition became very much slower and about one eighth of the labelled C still remained in the soil after 10 years. The decay curve can be represented by a two compartment model, in which about 70% of the ryegrass C decomposed by a first order process of half life 0.25 years and the remainder by a similar process of half‐life 8 years.
THE COMPLEXING OF COPPER BY HUMIFIED ORGANIC MATTER FROM LABORATORY PREPARATIONS, SOIL AND PEAT
Authors: BLOOMFIELD C. , SANDERS J. R.
Published: July 2006

The metal complexing properties of the colloidal and non‐colloidal fractions of water extracts of peat and aerobically composted lucerne, and of chelating resin and alkali extracts of peat and soil organic matter were compared.

The contributions of the non‐colloidal fractions to the complexing properties of the whole extracts are considerable, and on a weight‐for‐weight basis are somewhat greater than that of the corresponding colloidal material. No one compound is preponderantly responsible for the complexing action. The complexing activity of the non‐colloidal fractions is confined almost entirely to the acidic constituents. On the basis of the enhancement of the visible range of optical absorbance of the various preparations, Cu2+ is more extensively complexed than Mg2+, Mn2+, Cd2+, Zn2+, Co2+, Ni2+, and Pb2+.
CHANGES IN SOIL ORGANIC SULPHUR FRACTIONS DUE TO THE LONG TERM CULTIVATION OF SOILS
Authors: MCLAREN R. G. , SWIFT R. S.
Published: July 2006

The amount and chemical nature of soil organic sulphur was determined in several pairs of soils taken from long‐term pasture and adjacent, continuously cultivated sites. Similar determinations were also carried out on organic matter extracts obtained from the soils. The lower levels of sulphur in the arable soils compared with pasture soils were assumed to have resulted from the mineralisation of organic matter brought about by cultivation. Losses of sulphur caused by this mineralisation were found to occur in all three organic fractions examined.

A high proportion (75%) of the sulphur lost consisted of carbon‐bonded sulphur with only 25% derived from HI‐reducible forms. Despite this, it is suggested that, of the two forms, HI‐reducible sulphur has a more transitory nature and is possibly of greater importance in the short‐term mineralisation of sulphur whereas carbon‐bonded sulphur passes through an HI‐reducible form prior to release as inorganic sulphur. It is suggested that the sulphur present in the fulvic acid pool could, likewise, be most important for short‐term mineralisation.
SOIL CORROSIVENESS IN SOUTH OXFORDSHIRE
Authors: CORCORAN P. , JARVIS M. G. , MACKNEY D. , STEVENS K. W.
Published: July 2006

The potential corrosiveness of four soil series was studied in south Oxfordshire by measuring soil properties (resistivity, pH, sulphate content, moisture content and redox potential) thought to be closely connected with ferrous metal corrosion. Fifty random points were located in areas of the soil series map units. Paired measurements of resistivity were made at each sampling point.

Analysis of variance over all groups (soil map units) showed that, for all properties except redox potential, between group variance exceeded within group variance. The amount of variance contributed from within the pairs of resistivity measurements was small suggesting little short range variation in this property.

There was good association between the properties measured and the soil map units. The kinds of soil identified and the delineations on the soil map therefore represents a useful partitioning of the areas studied in terms of corrosion risk.
RENDZINA FORMATION ON BATHURST ISLAND11
Authors: TEDROW J. C. F. , WALTON G. F.
Published: July 2006

The identification of a Rendzina soil on Bathurst Island at 75° G45′ N, 99°30′ W, is believed to mark its northernmost known occurrence. The Rendzina soil is quite shallow, usually no more than 5 to 10 cm on for‐like limestone structures, but on the debris apron surrounding the base of the tor, the soil may be as much as 30 cm or more in depth.
STRUCTURAL FEATURES OF AGGREGATES IN SOME EAST ANGLIAN SILT SOILS
Authors: HAMBLIN A. P.
Published: July 2006

Samples from field plots of silty soils in East Anglia, which were high and low in organic matter, were subjected to mild ultrasonic vibration. In soils high in organic matter particles in the 2–20 μm or 20–50 μMm size range contained most humified organic matter, whereas in soils low in organic matter, most was present in the clay sized fraction. Scanning electron micrographs of the ultrasonically separated particles showed that those from the high organic matter soils had more extensive surface coatings. Clean fragments were left after peroxide and calgon dispersion treatment.
EFFECT OF pH ON PHOSPHATE ADSORPTION AND ISOTOPIC EXCHANGE IN ACID SOILS AT LOW AND HIGH ADDITIONS OF SOLUBLE PHOSPHATE
Authors: WHITE R. E. , TAYLOR A. W.
Published: July 2006

Measurements of equilibrium phosphate concentrations, adsorbed phosphate and isotopically exchangeable phosphate (Et) were made on suspensions of acid soils at initial P concentrations ranging from 1–1000 μM and pH values between 4.2 and 6.8. At low P concentrations (1–100 μM), the affinity of the adsorption reaction was greatest at pH 5.2–5.5. This result, which was inconsistent with the ligand‐exchange hypothesis of Kingston et al. (1967, 1972, 1974), was interpreted in terms of the formation of basic aluminium phosphates of varying composition that depended on the OH/P ratio in solution. At the highest P concentrations (1000 μM), when the affinity of adsorption was least at pH 5.2–5.5, it appeared that basic calcium phosphates were precipitating at pH values > 5.5.

In suspensions containing 1–100 μM P initially, values of Et did not change consonantly with values of adsorbed P over the pH range 4.8 to 5.5. It is suggested that the Et values were underestimated due to the presence of labelled complexes in solution which were detected by scintillation counting but not by the analysis for orthophos‐phate. Evidence from solution studies (White et al., 1976) suggested that as much as one‐third of the phosphate could be complexed with aluminium in solutions between pH 4.7 and 5.4 at P/A1 mole ratios of 0.075 to 7.5. It was apparent that the interpretation of the physical significance of E values in acid soils is complex and requires careful appraisal of the experimental techniques used.
STABILITY OF SOIL PORES DURING MERCURY INTRUSION POROSIMETRY
Authors: LAWRENCE G. P.
Published: July 2006

Mercury intrusion porosimetry is one of the techniques used to measure pore size distributions of dry soil samples. It is known that incorrect pore size distributions can be obtained for some porous materials due to sample damage occurring during mercury intrusion, but little evidence relating to soil samples has been published. The pore size distributions of aggregates from three soils, differing in texture, strength and porosity, were measured after heating to 300 °C by mercury intrusion porosimetry. After the first intrusion, all of the intruded mercury was removed from each sample by heating under vacuum. Samples were then re‐intruded. The pore size distribution curves for both intrusions were very similar, indicating an absence of sample damage during the first intrusion run.
SOIL ALKALINITY. II THE EFFECTS OF Na2CO3 ON IRON AND MANGANESE SUPPLY TO TOMATOES
Authors: MASHHADY A. S. , ROWELL D. L.
Published: July 2006

Sodium carbonate added to nutrient solution in sand culture depressed the growth of tomatoes both by the influence of high pH and HCO3− causing chlorosis and by the effect of Na+. Foliar sprays of iron and manganese removed chlorosis and increased growth but did not remove the effect of Na. In a sandy soil Na2CO3 did not cause chlorosis but Na+ depressed yield. Chelated Fe and Mn in the soil solutions (up to 7.3 × 10−4 M Fe and 2.6 × 10−5 M Mn at pH 9.0) were sufficient to supply the crop needs as shown by a second sand culture experiment where plants were fed with nutrient solution plus extracted soil solution.
THE DESCRIPTION OF PHOSPHATE ADSORPTION CURVES
Authors: BARROW N. J.
Published: July 2006

The two main motivations for studying equations which describe adsorption of phosphate are to understand the processes involved, and to summarize many results by a few numbers. If more than one hypothesis about the process is tenable, appropriate statistical procedures should be used both to choose between them and to obtain the best summary of the results with a given equation. Equations most likely to be successful in describing adsorption are those in which the affinity for adsorption decreases as the amount of adsorption increases. This effect is inherent in the process of phosphate adsorption and occurs because specific adsorption of anions increases the negative charge on the adsorbing surface. It is included in the complex equations of Bowden, and in simpler fashion in the Freundlich equation. Because the simpler equation can only approximately describe the true situation, a perfect fit over a wide range of concentrations should not be expected. Equations for which the affinity for adsorption is constant — such as the Langmuir equation — are not consistent with our knowledge of the adsorption process. This difficulty is not avoided by the multi‐surface Langmuir equations: such equations may also be difficult to justify on statistical grounds.
HYDRODYNAMIC DISPERSION IN COLUMNS OF PUMICE PARTICLES
Authors: CALVET R. , LERENARD J. , TOURNIER C. , HUBERT A.
Published: July 2006

A study was made of hydrodynamic dispersion in columns of pumice particles of different equivalent diameters and over a range of flow velocities. Dispersion is described by the first and second order moments of the elution curves. Two models are used to give a numerical analysis of the dispersion: a model using an apparent hydrodynamic dispersion coefficient and one using mixing cells with exchange (MCE). The part played by the stationary phase is described, and the molecular diffusion coefficient within the porous particles is calculated.
PHYSICO‐CHEMICAL STUDIES ON ENZYME‐DEGRADED FULVIC ACID
Authors: MAJUMDAR S. K. , RAO C. V. N.
Published: July 2006

The enzyme pronase released seven amino acids and also galactose and arabinose from fulvic acid. Hemicellulase released sugars and some amino acids. Removal of the amino acids lowered the molecular weight and gave a lower value for the C. E. C. Differential enzymic removal of carbohydrate and amino acids from the fulvic acid molecule reduced its viscosity. From this evidence it is concluded that the sugar and amino acids are linked to the aromatic core of fulvic acid.
RADIOCARBON DATING OF PALEOSOLS USING SOIL ORGANIC MATTER COMPONENTS
Authors: GOH K. M. , MOLLOY B. P. J.
Published: July 2006

Soil organic matter components of classical humic acid and humic fractions were extracted from two paleosols using 0.1 M Na4 P3 O2:0.1 M NaOH. These fractions were subjected to chemical treatment with 6 M HC1 or 70 per cent HNO, before radiocarbon assay, and their radiocarbon dates were compared with those of similar but untreated fractions, untreated buried soils, and previously published charcoal dates.

Hydrolysis of humic acid and humin fractions with mineral acids, particularly 70 per cent HNO3 led to older radiocarbon dates, comparable to, though slightly older than, those of charcoal derived from the same buried layers. In contrast, the dates of soils and their humic acid and humin fractions before acid hydrolysis were younger and therefore less reliable.

The application of this procedure to studies of paleosols in New Zealand is discussed.
STUDIES OF SOME CRACKING CLAY SOILS IN THE LAKE CHAD BASIN OF NORTH EAST NIGERIA
Authors: BEAVINGTON F.
Published: July 2006

The pedological characteristics, and physical, chemical and mineralogical properties are investigated for soils developed in a 1 m to 1.5 m layer of lacustrine clay material deposited on a former sand plain in the Lake Chad basin in north east Nigeria. (These soils are being developed for intensive production of rice, wheat and other crops under irrigation.) The surface layer of these soils has about 60 per cent clay, a pH of about 7.9, and a coarse, strong prismatic structure. The sub‐soil is often notably higher in clay content, pH and exch. Na. The smectite content of the clay fraction (surface soil) is 35 to 45 per cent and the CEC 350 meq kg‐1. The levels of montmorillonite and CEC, and the size of the cracks in dry soil, although the latter are appreciable, are all notably less than the values reported for the clay soils of the Sudan Gezira. The Lake Chad basin clay soils are not considered to be vertisols according to the FAO Soil Map of the World, on grounds of profile morphology, though it seems the French pedologists would regard them as paravertisols.
INACTIVATION OF CLAY pH‐DEPENDENT CHARGE IN ORGANO‐MINERAL COMPLEXES
Authors: GESSA C. , MELIS P. , BELLU G. , TESTINI C.
Published: July 2006

In 24 soils the CEC of untreated samples, of samples treated with hydrogen peroxide, and of samples treated with dimethyl sulphate, was determined at pH 3, S and 8. The CEC of clay and organic matter was calculated from multiple regression equations and compared with values after treatment with peroxide and after methylation. At pH 3 and pH 5 the CECs of clay by the three methods were similar, whereas at pH 8 they were significantly lower on untreated samples.

The results are interpreted in relation to the formation of organo‐mineral complexes and to the interaction of the acid functions of the clay and organic matter.
A STOCHASTIC MODEL FOR THE GROWTH OF ROOTS IN TILLED SOIL
Authors: DEXTER A. R.
Published: July 2006

A method of defining soil macrostructure, based on observations of the distribution of aggregates and voids along horizontal transects, is combined with a model for the probability of a root either penetrating, or being deflected by an aggregate, after passing through a void. The latter is based on the strength of the aggregate, the angle of incidence, the length of the preceding void, and root properties. Effects of soil macro‐structure, aggregate strength and plant species are discussed.

A good correlation was obtained between the predicted nutrient uptake per unit length of root and the measured uptake per plant from beds of different‐sized aggregates.

The inclusion of the effect of aggregate strength on root elongation rate removed all effects of aggregate size on the rate of uptake of non‐mobile nutrients. In order to reconcile this result with the correlation mentioned above, it is hypothesized that greater root branching occurs in beds of smaller aggregates so that the nutrient uptake remains the same as it would have been in the absence of rate effects.

It is shown that an optimum' soil macro‐structure exists for the maximum growth of roots of a given plant species. This optimum structure depends on the strength of the soil aggregates.
THE EFFECTS OF TILLAGE, DIRECT DRILLING AND NITROGEN FERTILISER ON SOIL TEMPERATURE UNDER A BARLEY CROP
Authors: HAY R. K. M. , HOLMES J. C. , HUNTER E. A.
Published: July 2006

Continuous hourly records of soil temperature were collected at 1, 5 and 20 cm, throughout two growing seasons, 1973 and 1974, under crops of spring barley in the east of Scotland. Measurements were obtained from three cultivation treatments, deep ploughing, normal ploughing and direct drilling, at two nitrogen fertiliser levels, 0 and 150kg/ha. Compared with ploughed soil, direct‐drilled soil had a higher surface reflection coefficient and a higher thermal diffusivity between 5 and 20 cm; overall, this resulted in lower heat sums (°C hours/day over 5 °C and 10 °C) in direct‐drilled soil at 1 cm and 5 cm during the first 20 days after sowing. The thermal regimes of normally and deeply ploughed plots were very similar. Nitrogen fertiliser caused significant lowering of soil temperature at all three depths in the latter half of the growing season, due to increased shading of the soil surface by the crop canopy. Some implications of these findings for cultivations for cereals are discussed.
SOME CHARACTERISTICS OF THE BROWN FOREST SOILS OF SCOTLAND
Authors: RAGG J. M. , BRACEWELL J. M. , LOGAN J. , ROBERTSON L.
Published: July 2006

This paper considers the constitution of the freely drained brown forest soils both as a whole and divided on the basis of their field properties into podzolic and non‐podzolic groups, and their relationship to classes within the soil taxonomies used by other soil surveys. A study of 86 profiles collected in Scotland and regarded as brown forest soils, shows that, of the various physical, chemical, and environmental characteristics examined, those relating to temperature, altitude, base status, pyrolysis ratio, and the ratio of pyrophosphate to dithionite‐extractable iron show the most significant ‘between‐group’ differences; these also distinguish the podzolic group from the podzols. The ratio of extractable sesquioxides to clay content which has been used as a criterion in some soil taxonomies is an ineffective discriminant because of the low clay content of many of these soils.
SOIL WATER: QUANTITIES, UNITS AND SYMBOLS
Authors: ROSE D. A.
Published: July 2006

Soil water studies involve physical quantities, units and symbols, and these are discussed in terms of the International System of Units (SI) and the soil physics terminology (1976) of the International Society of Soil Science.

The author particularly examines

the relation of SI units to the familiar but superseded cgs units;

the effect of the frame of reference on the expression of water potential and hydraulic conductivity;

the different interpretation of hydraulic conductivity in soil physics and in biophysics; and

methods of avoiding ambiguity in presenting data.
PROCESSES OF HUMUS FORMATION AND TRANSFORMATION IN SOILS OF THE CANADIAN GREAT PLAINS
Authors: ANDERSON D. W.
Published: July 2006

A study of the A horizons of cultivated soils from Saskatchewan, Canada showed that the organic carbon contents were in the sequence semi‐arid Dark Brown soils (1.7 per cent), < Black soils (2.55–2.8 per cent), < sub‐humid Dark Gray soils (4.5 per cent). The relative proportions of humic acids and the ratios of humic acid: fulvic acid increased in a similar sequence. There were accompanying increases in extinction values at 280 nm, and in levels of nonhydrolyzable nitrogen suggesting more extensive polycondensation of humic materials. These observations are discussed in terms of a working hypothesis for humus formation and transformations, that gives particular emphasis to the soil environment and to interactions between organic and inorganic components.
THE USE OF ACETYL ACETONE AS A SELECTIVE EXTRACTANT OF ORGANICALLY BONDED METALS IN SOILS
Authors: HAMBLIN A. P. , POSNER A. M.
Published: July 2006

Extractions of Fe(III) and Al(III) from hydrolyscd metal polymers, hydrous metal oxides, kaolinite, metal humates and soil were made using acetyl acetone in both polar and non‐polar solvents. Amounts of metal ions removed from inorganic materials were similar in both solvents, but from metal humates and soil more metal ions were removed in the aqueous system. The hydration state of the organic material was considered responsible for the difference. The results demonstrate that caution should be taken in ascribing metals extracted by selective dissolution techniques to particular soil components when non‐polar solvents are used.
VARIABILITY OF ORGANIC MATTER AND EXCHANGEABLE CATIONS WITHIN THE A2 HORIZON OF AN IRON PODZOL
Authors: BRACEWELL J. M. , ROBERTSON G. W. , LOGAN J.
Published: July 2006

Analysis of variance has been carried out between soil samples separated by distances of 0.5 m, 10 m and 0.5–8 km. The samples were taken from the A2 horizon of the Countesswells series iron podzol, thus maintaining the same pedological feature, profile class and parent material. The organic matter has been examined by the pyrolysis characteristics, total carbon and nitrogen, and the cations by exchangeable Ca2+, Mg2+, Na+, K+ and H+, whilst pH and total phosphorus have also been determined. The analysis of variance with respect to distance between the samples shows that all the properties examined exhibit considerable variation over short distances, many showing the major proportion of their total variance at a distance of 0.5 m. This markedly limits the interpretation of data from single samples. Those properties reflecting base status and humus type show, in addition, a variation of similar size over distances of the order of a kilometre.
ROTHAMSTED STUDIES OF SOIL STRUCTURE III
Authors: NEWMAN A. C. D. , THOMASSON A. J.
Published: July 2006

The response of three pairs of soils having contrasting management behaviour to changes in water content was investigated by measuring moisture characteristics, shrinkage, and pore size distributions by mercury porosimetry. Sample preparation for mercury porosimetry was by direct drying, or water replacement by methanol and liquid CO2 followed by evaporation above the critical temperature. In heavy textured horizons, water release on shrinkage between ‐0.05 and ‐15 bar matric potentials occurs when pores of 10–200 nm equivalent plate separation contract. Structure development is dependent on the stability and regeneration of pores in the size range 200 nm‐30 μm during cycles of wetting and drying. Soils with little stable porosity in this size range show nearly normal shrinkage and have coarse structural units, whereas soils with stable or regenerating porosity depart more from normal shrinkage and structure in the profile tends towards a finer per unit. The application of mercury porosimetry shows promise for determining possible porosity limitations in soil profiles.
ROTHAMSTED STUDIES OF SOIL STRUCTURE V.
Authors: WILLIAMS R. J. B.
Published: July 2006

Three pairs of soils were chosen, each with one difficult and one easily manageable soil with similar texture. Mechanical composition and organic matter content greatly affected the measured physical properties some of which related to the field behaviour of each pair. Soils from all horizons were stable to water slaking except some subsoils on the Ragdale, Hanslope, Salop, and Flint series. Dry and total mechanical slaking were less and breaking strengths more for the Denchworth, Evesham, Ragdale and Hanslope series than for the Salop and Flint soils. Water‐holding capacity was largest for the Denchworth and Evesham soils, but slow penetration of water into their dense clods could influence regeneration of tilth.
PORE SIZE DISTRIBUTION IN CRITICAL POINT AND FREEZE DRIED AGGREGATES FROM CLAY SUBSOILS
Authors: LAWRENCE G. P. , PAYNE D. , GREENLAND D. J.
Published: July 2006

Using aggregates from 2 clay soils over a range of water contents from pF 1 to oven dry, shrinkage and water release curves were measured and pore size distributions found by mercury porosimetry after critical point and after freeze drying.

Freeze drying caused less shrinkage, the maximum being 6 cm3 100 g−1 from pF 1, but gave a large increase, up to 10 cm3 100 g−1, of pores in the 0.1–10 μm size range.

Critical point drying produced more shrinkage from pF 1, more than half of which was attributed to loss of interlamellar water and the rest to the collapse of pores larger than 10 μm.

In these clays the volume of pores of over 3 μm diameter was very small (<3 cm3 100 g−1) and most of the plant available water was released by collapse of narrower pores and not by pore emptying.
INTERPRETATION OF PHOSPHORUS UPTAKE BY BARLEY FROM ACID SOILS USING A DIFFUSION MODEL
Authors: KUNISHI H. M. , TAYLOR A. W. , VICKERS J. C.
Published: July 2006

Phosphorus uptake by bailey (per cent of dry tissue) grown on four acid soils, each treated with four amounts of lime and P, correlated equally well with EPC (equilibrium P concentration = concentration of P supported in solution at field capacity) and with diffusion supply of P to root cylinder surfaces calculated from the soil indices including EPC, a soil capacity factor maintaining that concentration, and a diffusion coefficient. Calculated rates of P supplied by diffusion to primary root cylinder surfaces were too low to account for P found in plants. If the remainder of the observed P uptake was assigned to root hairs, the ratios of calculated root hair surface area to estimated root cylinder surface areas necessary to account for the difference were in reasonable agreement with ratios for barley reported by other workers.
SOILS AND QUATERNARY GEOLOGY IN BRITAIN
Authors: CATT J. A.
Published: July 2006

The succession of Quaternary deposits in Britain records only small, fragmentary parts of a very complex history of Quaternary events resulting from many climatic fluctuations. Deep sea sediments provide a more continuous record, but correlation between the oceanic and terrestrial successions is at present extremely difficult, mainly because of the lack of absolute dates for older parts of the latter. The often conflicting evidence provided by indirect methods of dating and long‐distance correlation is illustrated by reference to the chalky tills of East Anglia and the English Midlands, and the importance of soil studies in elucidating regional Quaternary stratigraphy is emphasised.

The scanty history of pedogenesis in various parts of Britain is tentatively related to the provisional succession of Quaternary stages. Important changes in soil development processes occurred in mid‐Flandrian times as well as in earlier cold and temperate (inter‐glacial) stages, Many features of unburied soils are probably early Flandrian or older relicts, and difficulties consequently arise over use of the word ‘palaeosol’. Interglacial relict features in soils on pre‐Devensian deposits (paleoaigillic subgroups) are distinguished from Devensian and Flandrian soil characters, but it is difficult at present to differentiate pedogenesis of successive interglacials.

More than two‐thirds of England is covered by Quaternary deposits, mainly of cold periods, and these generally provide better agricultural soils than pre‐Quaternary sediments. Some relict features of both cold and temperate Quaternary stages also seem to be significant in determining the agricultural capability of British soils, but their effects need evaluating more precisely.
DIFFUSE DOUBLE LAYER THEORY APPLIED TO Na‐Ca EXCHANGE EQUILIBRIA IN TEMPERATE AND SEMI‐ARID TROPICAL SOILS
Authors: POONIA S. R. , PAL RAJ , TALIBUDEEN O.
Published: July 2006

A cation exchange equation based on diffuse double layer (DDL) theory was tested on 26 surface and sub‐surface soils from 6 field experiments in temperate and semi‐arid tropical regions. Sodification (the fraction of total charge on the surface neutralised by the excess of Na+ plus the deficit of Cl−), or the exchangeable Na percentage, ESP, of these soils in relation to SAR, the molar ratio (Na]/[Ca + Mg] 1/2, was evaluated from the observed data on Na:Ca exchange in two ways, using the DDL equation: (1) by multiplying the surface charge density of the soil with a mean correction factor f (based on the whole isotherm) assuming no interaction between adjacent clay platelets; this predicted the sodification of the soils satisfactorily between 0–30 ESP, though at the highest SAR values (i.e. > 60), predicted ESP values were significantly smaller than the experimental values for 23 of the 26 soils; (2) by assigning values to the extent of interaction Yd (directly related to the electric potential Ψd midway between adjacent clay platelets) over the whole isotherm; Yd was found to increase by varying degrees in different soils with SAR and ESP. Also in 12 of the 15 pairs of soils compared, the mean value, d, over the whole Ca‐Na exchange isotherm was appreciably larger for surface soils (which had higher surface charge densities) than for the subsoils from the same sites.

The suggestion that the Yd parameter provides a better criterion than the f parameter for characterising and comparing Na:Ca exchange equilibria in contrasting soils is discussed in relation to the effects of soil components.
PRECIPITATION OF CARBONATES IN SOILS IN CONTACT WITH WATERS UNDERSATURATED OR OVERSATURATED IN RESPECT TO CALCITE*
Authors: LEVY RACHEL
Published: July 2006

Under transient conditions, the precipitation of carbonates in a calcareous and a non‐calcareous soil was influenced by calcium, magnesium and bicarbonate ions from soil sources. These sources were: the soil solution, the soil exchange complex and the dissolution of aluminosilicates. There was no significant difference between the amount of carbonates which precipitated in the two soils when in contact with the same water. It was found that for small portions of water in contact with the two soils, precipitation of carbonates took place both from under‐saturated and the over‐saturated waters. As the cumulative amounts of water in contact with the soils increased, the amount of ions contributed by the residual soil solutions and the exchange complexes decreased, and the amount of precipitating carbonates decreased also. At very large cumulative amounts of water, the precipitation of carbonates in the soils was controlled by both the water and the ions released from the soils.
ACID SULPHATE SOILS: MORPHOLOGY AND PREDICTION
Authors: DENT D.
Published: July 2006

Proposals are made for horizon designation of soils developed under mangrove vegetation and in polders in northern New Zealand. A model is presented for predicting the development of acid sulphate soils by field survey prior to reclamation.
THE ORIGIN OF THE RED MEDITERRANEAN SOILS IN EPIRUS, GREECE
Authors: MACLEOD D. A.
Published: July 2006

To determine the contribution of limestone weathering to soil formation the insoluble residues of six samples of the Pantokraton limestone were separated by treatment with 2M acetic acid at pH 3. The mean insoluble residue content is only 0.15% and to produce a soil depth of 40 cm it has been calculated that about 130 m of limestone would have to be weathered. No correspondence was found between the particle size distribution of the residues and of the overlying red soils, and the high siltrclay ratios of the soils do not indicate prolonged subtropical weathering. The particle size distribution of the soils is akin to that of aerosolic dusts. The dust loading of the atmosphere in the eastern Mediterranean is among the highest recorded, and it is proposed that the soils have developed on dust blown by sirocco winds from the deserts of N. Africa.
SOME CONTRASTS IN SOIL DEVELOPMENT BETWEEN GRASSLAND AND DECIDUOUS WOODLAND SITES
Authors: GRIEVE I. C.
Published: July 2006

Soil profile and structural development were compared under two land‐use types on acid and calcareous soils. The grassland soils were found to have better developed and more stable structures in the A horizon, but unchanged bulk density and infiltration capacity. In the B horizons the direction of difference was reversed. Profile development was deeper under woodland on the softer parent materials. The differences were primarily related to root density, penetration and more intimate incorportion of organic matter under grass.
A NEW HAND‐HELD RECORDING PENETROMETER FOR SOIL STUDIES
Authors: ANDERSON G. , PIDGEON J. D. , SPENCER H. B. , PARKS R.
Published: July 2006

This paper describes and evaluates a new solid‐state recording hand‐held cone penetrometer developed for in‐situ soil studies. Force is measured by a strain‐gauged transducer, and depth by an accurate optical system. Data for up to 20 penetrations per plot are stored and processed within the instrument in the field.

The new penetrometer has been evaluated in field and soil tank experiments in comparison with three widely contrasting existing penetrometers ranging from a simple hand‐held penetrometer to a trailer‐mounted power‐driven instrument.

The results indicated that the simple hand‐held penetrometer gave appreciably different cone resistance profiles from the other instruments. In particular, spurious ‘treatment effects’ obtained from the tillage experiment were shown to be due to inadequate instrument performance. The new solid‐state recording hand‐held penetrometer gave results comparable with those obtained from the more complex trailer‐mounted instrument and another hand‐held recording penetrometer.