bluuebunny/crossref_metadata_2025 huggingface dataset:
NON‐EXCHANGEABLE AMMONIUM IN SOILS OF ISRAEL AND ITS RELATION TO CLAY AND PARENT MATERIALS
Authors: FEIGIN A. , YAALON D. H.
Published: July 2006

The occurrence of non‐exchangeable ammonium in the main soil groups of Israel and its relation to various factors were determined in 129 samples from thirty‐one profiles. In arid and semiarid soils the level ranged from 0·18‐0·53 me/100 g, with most values falling between 0·25 and 0·40 me/100 g. In the sub‐humid Mediterranean region the values ranged between 0·04 and 1·0 me/100 g, with most of them falling between 0·14 and 0·65 me/100 g. In most cases the percentage of non‐exchangeable ammonium‐N in the total soil nitrogen was in the range of 2–25 per cent.

The clay fraction is a significant factor influencing the amount of non‐exchangeable ammonium in the soils tested. The relatively low amounts of non‐exchangeable ammonium found are consistent with the predominant clay mineral in most of the soils being montmorillonite. A good correlation was obtained with the content of illite, which is the main carrier of the non‐exchangeable ammonium. The mean non‐exchangeable K/non‐exchangeable NH, ratio in the Israeli soil clays was 17. In soils derived from or affected by aeolian dust, the level of non‐exchangeable ammonium calculated for the clay fraction spans that of aeolian dust and is, in general, higher than in soils developed from limestone, dolomite, marl, tuff, or basalt.
SOIL PHYSICS: TWENTY‐FIVE YEARS ON1
Authors: CHILDS E. C. , YOUNGS E. G.
Published: July 2006

In comparison with the situation twenty‐five years ago, the analysis of soil‐water hysteresis has been transformed by the concepts of independent and non‐independent domains, and the analysis of the diffusion‐like movement of water in unsaturated soil has led to a theory of the development of water content profiles which was only vestigial at the time of the founding of the British Society of Soil Science. The theory of the control of ground water has greatly developed, mostly along established lines, as also have field methods of determining the hydraulic conductivity necessary for the application of this theory. In striking contrast, the debate about the assessment of soil texture pursues its course unchanged.
FULVIC ACID: I. PARTIAL FRACTIONATION1
Authors: MacCARTHY PATRICK , O'CINNEIDE S.
Published: July 2006

Fulvic acid extracted from peat was partially fractionated on anion and cation exchange resins. In the latter case the fractionation is attributed to the presence in fulvic acid of components possessing amine groups; this was confirmed by chemical means and by infrared spectroscopic evidence. The infrared and ultraviolet spectra of fulvic acid and its various fractions are discussed and the occurrence of carboxyl, phenolic, and amine groups in fulvic acid and the fractions obtained is considered. It was further established that nitrous acid can destroy the amine groups present in fulvic acid.
KINETICS OF ISOTOPIC EXCHANGE OF PHOSPHATE ADSORBED ON GIBBSITE
Authors: KYLE J. H. , POSNER A. M. , QUIRK J. P.
Published: July 2006

An Elovich‐type equation has been used to describe the kinetics of isotopic exchange of phosphate adsorbed on the surface of gibbsite. The equation is

image

where A and B are parameters; θ=bF/[b+a(I‐F]; a and b are the molar concentrations of the phosphate on the crystal surface and in solution respectively and F is the fraction exchange of the radio‐isotope at time t. First‐order rate constants were obtained from the equation. The reference state for the first‐order rate constants, and the distribution of activation energies, for exchange can be related to the Elovich equation parameters. The kinetic results are consistent with SN1 dissociation or SN2 bimolecular solvolysis for the phosphate ligand. The eschange reaction is subject to an acid‐base catalysis the exact nature of which could not be determined from the available data.
COMPARISON OF DIFFERENT FORMS OF PHOSPHATIC FERTILIZERS PART I: RAPE AND SWEDES
Authors: JONES EDRYD
Published: July 2006

Eighteen experiments were carried out in Wales and the West Midland Region, between 1966 and 1971 to compare granular basic slag with powdered basic slag and superphosphate (or triple superphosphate) as phosphatic fertilizers for rape and swede crops. At the swede sites additional comparisons involving ground mineral phosphates were also made.

The fertilizer treatments were applied at sowing time and at rates supplying 28 and 56 kg P/ha for rape and 28 and 56, or 44 and 88 kg P/ha for swedes. Large increases in yield of rape and swedes to the lower rate of phosphate application were recorded at most sites but, in general, only very small additional responses were obtained to the higher dressing.

For both rape and swede crops, the relative effectiveness of the different phosphatic fertilizers varied somewhat between sites. Comparisons of the superphosphate and basic slag treatments show that the former gave slightly higher yields at most sites. Granular basic slag was marginally inferior to powdered slag for swedes but in general the differences between the effects of superphosphate (or triple superphosphate) and the two forms of slag were small.

The effects of the Gafsa phosphate treatments for swedes were variable, being as effective as superphosphate or basic slag at some sites and much less so at others. This inconsistency detracts from their over‐all usefulness. There was no definite advantage in the finely‐ground (80 per cent through 300 mesh (50 μm)) material over the relatively coarser (60 per cent through 100 mesh (150 μm)) product.

Moroccan mineral phosphate was inferior to the Gafsa phosphates for swedes, particularly at the most responsive sites.
DENSIMETRIC FRACTIONATION OF SOIL ORGANO‐MINERAL COMPLEXES
Authors: RICHTER MARTIN , MIZUNO ICHIRO , ARANGUEZ SANTIAGO , URIARTE SUSANA
Published: July 2006

A rapid, simple, and precise density fractionation of soil mineral‐organic complexes, suitable for routine work, is described. Special features of the method are: low sample weight, use of glass‐fibre paper to collect the lighter fractions, and use of a modified Walkley‐Black procedure to determine the carbon content of the light fraction in test tubes. Density‐distribution curves of organo‐mineral soil complexes are shown to yield useful basic information on degradation processes of soil organic matter caused by cultivation. The results suggest that complexes between clay and organic matter tend to build up preferentially with a certain proportion between the components.
AN ASSESSMENT OF THE RELATIONSHIP BETWEEN THE SURFACE PROPERTIES OF CHALK SOILS AND SLOPE FORM USING PRINCIPAL COMPONENTS ANALYSIS
Authors: ANDERSON K. E. , FURLEY P. A.
Published: July 2006

Five line transects were sited over grass‐covered, convex‐concave slopes in the Berkshire and Wiltshire chalk downs, with the object of describing and interpreting the variation in selected surface soil properties. Previous work had concentrated upon the correlation between single variables and slope gradient and slope length, whereas the emphasis of the present paper lies in examining the interrelationships amongst the variables through the use of principal components analysis.

A consistent pattern of variation was established between the five sites. The first component derived from the analysis was interpreted as a combined organic matter and soluble constituents factor, which accounted for between 50 and 60 per cent of the total variance. The second component was identified as particle‐size variation and accounted for a further 13 to 18 per cent of the total variance.

Whereas the distribution of the component scores for the second component supported the original idea of a sharp junction effect in the pattern of soil properties on the slope, the first and most important component indicated a more diffuse transition from net erosion to net deposition conditions.
RECONNAISSANCE FOR SOIL SURVEY
Authors: BECKETT P. H. T. , BIE S. W.
Published: July 2006

The total length of soil boundary on a map can be measured by counting the number of intercepts between boundaries and a randomly distributed array of sampling lines. It is thus also possible to estimate the length of the same boundaries before survey by means of a similar array of field traverses. The per cent sampling error of estimates of boundary density (boundary per unit area), is approximately the reciprocal of the square root of the number of intercepts.
SOIL TRANSECT CORRELOGRAMS OF NORTH OXFORDSHIRE AND THEIR INTERPRETATION
Authors: WEBSTER R. , DE LA C H. E. CUANALO
Published: July 2006

In almost all soil surveys some attempt is made in the early stages to assess the scale on which the soil changes, and the information required is often obtained from transects. By recording soil properties at a constant close spacing on such transects methods of analysis, especially those devised for time series, data can be applied to reveal patterns of variation, and hence lead to rational mapping strategy. Correlograms, which show on average the relation of soil at one point to that at another, seem especially promising.

The potential of time series analysis in soil survey was explored by measuring soil properties in three horizons in profiles at 10 m intervals along a transect across the Lower Jurassic outcrop in north Oxfordshire. Correlograms were computed for clay, silt, pH, CaCO3, colour value, and stoniness in each horizon. They showed that, for all the properties, the relation between sampling points weakened steadily over distances from 10 m to about 230 m. The average spacing between geological boundaries on the transect was also about 230 m, and outcrop lithology was inferred as one of the main sources of soil variation. The effect of rock type was eliminated by computing deviations of the original values from the means of the outcrops in which they occurred. Correlograms of these showed almost no relation between points more than 10 m apart; i.e. the only other major source of variation occurred within 10 m.

In this instance mappable soil boundaries are likely to occur on average every 230 m, and sampling at a spacing closer than I15 m would be needed to detect them from profile inspection alone. Alternatively a map of the geological boundaries with descriptions of the soil for each map unit would constitute almost the best soil map that could be achieved in this area.
THE EFFECT OF PHOSPHATE APPLICATIONS ON THE DIFFUSION COEFFICIENTS AND AVAILABLE PHOSPHATE IN AN ACID SOIL
Authors: KUNISHI H. M. , TAYLOR A. W.
Published: July 2006

The apparent bulk phosphate self‐diffusion coefficient, resin extractable and isotopically exchangeable phosphate were measured on an acid Cecil sandy loam soil pre‐treated with calcium carbonate and monocalcium phosphate. Apparent diffusion coefficients increased four‐fold with a five‐fold increase in phosphate addition, but were not increased by liming. Resin extractable phosphate was greater than isotopically exchangeable after large phosphate additions. Calculated porous self‐diffusion coefficients did not change as a result of phosphate additions. The contribution of solid‐phase phosphate to diffusion was small and close to the limits of measurement.
THE OCCURRENCE AND PREDICTION OF CLODS IN POTATO RIDGES IN RELATION TO SOIL PHYSICAL PROPERTIES
Authors: CAMPBELL D. J.
Published: July 2006

Clod crushing resistance, bulk density, moisture content, and size distribution, together with fifteen bulk soil physical properties, were determined at thirty sites. Regression analyses indicated that the plasticity index of the soil is the principal property affecting both the clod crushing resistance and the yield of clods. Other less closely related properties are not always consistent in their effect between clod size ranges. A‘clod factor’ was derived from the product of the clod crushing resistance and the weight of clods in the ridge for each soil. The clod factor is linearly correlated with plasticity index (r= 0·587, P= 0·002) and a clod factor > 1000 was found for soils with a plasticity index greater than about 5. Harvest observations suggest that where the clod factor exceeded 1000, the efficiency of a mechanical potato harvester was reduced.
THERMODYNAMICS OF THE EXCHANGE OF NICOTINE ON ALUMINIUM‐MONTMORILLONITE
Authors: SINGHAL J. P. , SINGH R. P. , SINGH C. P. , GUPTA G. K.
Published: July 2006

The ion exchange equilibria involving the interaction of nicotine with Almontmorillonite was studied thermodynamically. The exchange isotherms at 30° and 60°C indicated a preference for Al ions by montmorillonite as compared with nicotinium ions. A separation factor supported the conclusion. The enthalpy gain indicated tighter binding of Al. The entropy gain indicated a diffused and disordered arrangement of nicotinium ions in the Goüy layer with Al forming a more ordered arrangement in the Stern layer.
A PYROLYSIS‐GAS CHROMATOGRAPHY METHOD FOR DISCRIMINATION OF SOIL HUMUS TYPES
Authors: BRACEWELL J. M. , ROBERTSON G. W.
Published: July 2006

Principles governing the choice of a pyrolysis‐gas chromatography method for work on soils and organic macromolecules are reviewed, and the method is applied to the discrimination of mull and mor humus in freely drained soils. Relatively undecomposed surface humus shorizons yield pyrolysis products characteristic of lignin, but these are not present in mineral horizons apart from traces persisting in some podzol A horizons. Mor humus incorporated in A horizons is characterized by a high pyrolysate content of furfurals and phenols whilst mull humus yields proportionately more pyrrole. Humus in B horizons yields a low furfural content with respect to pyrrole and a low content of polar heteroatomic molecules with respect to benzene, toluene, and light molecules of low polarity.
CHANGES IN THE CHEMICAL NATURE OF SOIL ORGANIC PHOSPHATE DURING PEDOGENESIS
Authors: BAKER R. T.
Published: July 2006

In two chronosequences of soils, total organic phosphate (P0) accumulated rapidly during the first 50 years of soil development, when organic matter increased and pH decreased. The rate of P0 accumulation then declined with age of soil until a ‘steady state’ was reached. The amounts of phospholipid, inositol phosphates and humic acid—P0 followed the same trends as the total P0.

Parent materials and very young soils contained largely citric acid‐soluble P0, but after less than 50 years, surface horizons accumulated sufficient organic matter to complex a considerable proportion of the P0. An upper limit of 20–5 per cent citric acid‐soluble P0 and 70–80 per cent NaOH‐soluble P0 was attained within 50 years of soil formation in the surface layers, and this slowly extended down the profile so that, after 10000 years, the soil had 20 per cent citric acid soluble‐P0 and 70 per cent NaOH‐soluble P0 to a depth of 1 m.
COMPUTED EFFECTS OF ADSORPTION KINETICS ON PESTICIDE MOVEMENT IN SOILS
Authors: LEISTRA M. , DEKKERS W. A.
Published: July 2006

For a model at high water fluxes, the inclusion of first‐order adsorption‐desorption rate constants leads to slower leaching of pesticide and increased spread than predicted using instantaneous equilibrium. The initial condition of the substance near the soil surface is also found to be important.

A model with simultaneous fast and slow adsorption‐desorption equilibria describes and explains published experimental data comparatively well. Under a pattern of intermittent rainfall, the effect of adsorption‐desorption kinetics on pesticide movement is comparatively small.
AMORPHOUS CONSTITUENTS OF SOME HIGH ALTITUDE SOILS OF THE SOUTH ISLAND OF NEW ZEALAND
Authors: MILESTONE N. B. , WILSON A. T.
Published: July 2006

Soils developed at high altitudes in the South Island, New Zealand have several pedological properties similar to the volcanic allophane soils of the North Island. Their clay fractions consist of finely divided parent material with some degree of ordering and some oxidation of ferrous to ferric iron, but because they are so finely divided they give no X‐ray diffraction patterns, and their IR spectra are typical of amorphous aluminosilicates. They are shown to have structure by electron microscopy and thermal analysis. It is suggested that the clays have been produced by the grinding together of stonesby frost action, and that similar material probably exists in other alpine areas and in polar regions where frost action is common.
TIME‐DEPENDENT SORPTION OF PHOSPHATE BY SOILS AND HYDROUS FERRIC OXIDES
Authors: RYDEN J. C. , McLAUGHLIN J. R. , SYERS J. K.
Published: July 2006

The sorption of inorganic phosphate (P) by soils and hydrous ferric oxides was studied at times up to 192h. An initially rapid decrease in solution P concentration was followed by a much slower decrease between 48 and 192h with soils, Fe gel. and natural goethite, whereas synthetic goethite gave a well‐defined equilibrium condition after only 48h. Resolution of the sorption isotherms showed that the increase in P sorption with time involved an appreciable shift of P from a more‐physically sorbed form to a chemisorbed form. This was supported by chemical fractionation which showed that NaOH‐extractable P was fairly constant with increasing sorption time, whereas the additional sorbed P was extracted by citrate‐dithionite‐bicarbonate from soils, and by HC1 from Fe gel and natural goethite. These sorbents contained short‐range (amorphous) material, whereas synthetic goethite, from which all sorbed P was NaOH –extractable. did not. It is proposed that the time‐dependent sorption of P and the associated shift of P to chemisorbed forms, involves the diffusion of P into “structurally porous”, short‐range order material.
EFFECTS OF IONIC STRENGTH ON CHEMISORPTION AND POTENTIAL‐DETERMINING SORPTION OF PHOSPHATE BY SOILS
Authors: RYDEN J. C. , SYERS J. K. , McLAUGHLIN J. R.
Published: July 2006

Amounts of inorganic phosphate (P) sorbed by two unfertilized soils, during times less than required to reach equilibrium, were affected by the ionic strength and cation species of the matrix solution. For non‐equilibrium conditions the amounts of P sorbed increased with increasing ionic strength and were greater with Ca2+ than Na+. For higher P additions, resulting in equilibrium solution P concentrations greater than 30 to 40μrnole 1−1, the effects of the matrix solution on P sorption were maintained at equilibrium, whereas at lower P additions the dependence of sorption on matrix solution composition was eliminated at equilibrium.

Equilibrium sorption isotherms for each soil and matrix solution were described by three Langmuir equations, which corresponded to distinct concentration ranges or regions (I, II, and III) on the overall isotherm. The free energies of sorption (ΔG) for each region, were essentially independent of the soil matrix solution. The sorption maxima for regions I and II of the isotherm for a particular soil were also virtually independent of the matrix solution used. The sorption maximum for region III, however, was markedly dependent on the matrix solution, implying a potential‐determining (p.d.) sorption mechanism.
THE MORPHOLOGICAL, PHYSICAL AND CHEMICAL PROPERTIES OF TWO MOUNDS OF MACROTERMES BELLICOSUS (SMEATHMAN) COMPARED WITH SURROUNDING SOILS IN SIERRA LEONE
Authors: MIEDEM A R. , VAN VUURE W.
Published: July 2006

The mounds are situated in the Makeni Area, Northern Province, Sierra Leone. Seventy five percent of this area consists of clayey upland soils that belong to the Makeni series (Typic Paleudult), which contain about 80 per cent of gravel‐sized hardened plinthite glaebules. The upland is dissected by numerous streams along which gravel‐free fine‐loamy terrace soils occur that belong to the Masuba series (‘Plin thic’Udoxic Dystropept) occupying about 15 per cent of the area. Mound 1 is a young inhabited mound on a Masuba soil, whilst mound II is an old abandoned mound on a Makeni soil.

A trench was dug from the centre of the mounds into the surrounding soils. Profiles were described and samples were analyzed for organic carbon, CEC, exchangeable Ca, Mg, K, Na, and pH, and for particle size analysis with 5 sand fractions.

The material used to build the mounds is derived from the subsoil (between 30 and 100 cm depth). Termite channels extended laterally for at least 10 m for mound I, but could not be traced so clearly for mound II.

Mound I and the nest of mound II contain a higher percentage of particles less than 250 μm than the surrounding subsoil. Material over 2 mm is not carried by termites.

Both mounds show a higher base saturation and higher values of exchangeable Ca, Mg and K, compared to the surrounding subsoil. Increased CEC and pH are noted in mound I and the nest part of mound II, the latter also showing increased values of exchangeable Na. Organic carbon values are equal to those of the surrounding subsoil.

Accumulation of mineral elements from organic matter collected as food, including small contributions from the fungus combs and termite bodies, is primarily responsible for the observed differences. In view of the water analyses no contribution is expected from the fluctuating groundwater table.
CHEMICAL DEGRADATION OF HUMIC AND FULVIC ACIDS EXTRACTED FROM MEDITERRANEAN SOILS
Authors: CHEN Y. , SENESI N. , SCHNITZER M.
Published: July 2006

Humic and fulvic acids were extracted from two Israeli and tour Italian soils and oxidized with alkaline permanganate solution after methylation. Following oxidation, the degradation products were separated by solvent extraction and chromatographic methods and identified by gas chromatography‐mass spectrometry.

Major oxidation products were aliphatic, phenolic and benzenecarboxylic acids. In toto, 33 oxidation products were identified. These were essentially the same compounds as those produced by the permanganate oxidation of methylated humic and fulvic acids extracted from soils formed under widely differing climatic and geologic conditions, except that yields of phenolic acids from Mediterranean humic and fulvic acids were lower than those produced under similar conditions from humic materials extracted from other soils. The information provided by chemical degradation suggests that humic and fulvic acids from widely differing soils have similar chemical structures.
POLYCARBOXVLIC ACIDS EXTRACTED BY WATER AND BY ALKALI FROM AGRICULATURAL TOP SOILS OF DIFFERENT DRAINAGE STATUS
Authors: LINEHAN D.J.
Published: July 2006

Water‐ex tractable poly carboxy lie acids and alkali‐extractable humic acids and fulvic acids, were isolated from agricultural top‐soils of two soil associations. Samples from four soil series from each association were selected with drainage status varying from well‐drained to very poorly‐drained. The amounts of atkali‐extractable humic acid and water‐ex tractable polycarboxylic acids were highest in the very poorly‐drained soils whilst the amounts of alkali‐extractable fulvic acid were generally similar in all the soils, although the fulvic acid accounted for a lower proportion of the total organic matter in the poorly‐drained soils. Oxalate‐extractable aluminium decreased with increased drainage impedance, whilst no such trend was observed for oxalate‐extractable iron. It is suggested that the fulvic acid‐like polycarboxylic acids are removed from the soil solution by adsorption onto sesquioxides; so that the lower content of aluminium oxides in the very poorly‐drained soils results in depressed levels of fulvic acid and increased concentrations of water‐extractable polycarboxylic acids.
STABILITY OF FERRIC PHOSPHATES
Authors: McLAUGHLIN J. R. , SYERS J. K.
Published: July 2006

Essentially congruent dissolution of colloidal ferric phosphate, metastrengite, and strengite was observed at pH 1.5 during 25 days. In contrast, preferential release of P to solution was obtained at pH 6.0. Dialysis of dried preparations of these three materials against hydrous ferric oxide gel (Fe gel) resulted in the loss of 9.0, 3.0, and 0.4 per cent of total P, respectively, during 20 days. A wet preparation of colloidal ferric phosphate released 17 per cent of total P during the same time. During dialysis, all ferric phosphates assumed a brownish colour. Electron microscopy revealed the presence of an appreciable quantity of short‐range order material surrounding crystals of strengite following dialysis. These observations, coupled with the decrease in type ratio, demonstrate that an Fe gel coating forms on the ferric phosphates during dialysis. The results are discussed in terms of the likely stability of ferric phosphates in soils.
USE OF A CHEMOSTAT TO STUDY DECOMPOSITION OF WHEAT STRAW IN SOIL SLURRIES
Authors: LYNCH J. M. , GUNN K. B.
Published: July 2006

The breakdown of wheat straw in slurries of soil was studied under controlled physical conditions. In the absence of oxygen there was a reduction in the redox potential and pH of the slurries and there were concomitant increases in the concentrations in solution of total carbon compounds, acetic acid, iron and manganese. The temperature coefficients (Q10) for these reactions and processes were between 2.5 and 2.9 but they did not take place in the presence of oxygen nor when nitrate was added. When no straw was mixed with the soil, similar changes took place but were much less pronounced and no acetic acid was formed.
MUCILAGES AT THE ROOT SURFACE
Authors: OADES J. M.
Published: July 2006

The mucilaginous material, which forms a layer several microns thick around plant roots, contains a glucan, a polyuronide, and heterogeneous polysaccharides. An assessment is given of the effects of the mucilage on ion and water uptake by plants, on soil chemical and physical properties including aggregation, and as an energy source for microorganisms. It is concluded that these effects are important but that more chemical and physical studies of plant mucilage are required.
SOIL ALKALINITY. I. EQUILIBRIA AND ALKALINITY DEVELOPMENT
Authors: MASHHADY A. S. , ROWELL D. L.
Published: July 2006

Theoretical relationships between pH, CO2 partial pressure and alkalinity (bicarbonate + carbonate concentrations) have been shown to apply to solutions and calcite and soil suspensions.

The exchange of Na onto three Ca clays shows that Ca is preferred but with negative free energies of exchange. With decreasing total electrolyte concentration, the preference for Ca increases, so that only when the concentration is above 10‐3M will significant amounts of exchangeable Na be found in soils. The preference for Ca is illite > montmorillonite > vermiculite.

Dilution of the mixed Na‐Ca clay suspensions causes exchange, desorption of Na and. in some cases Ca. This desorbed or ‘alkaline’ Na (and Ca) is replaced by H some of which attacks the clays. The apparent hydrolysis coefficient, KG = H adsorbed (Na)/Na adsorbed (H), varies between 5 and 9 × 105, increases with increase in electrolyte concentration and varies in the order vermiculite > illite > montmorillonite. The concentration of alkaline Na + Ca increases with increasing ESP, and with clay type in the same order as the KG values. The pH calculated from the alkaline Na + Ca, assumed equal to the alkalinity was equal to measured values except for montmorillonite where the calculated values were low. Magnesium release by acid attack of the montmorillonite may explain the differences.

Vermiculite rich soils will be most likely to accept exchangeable Na and to hydrolyse and develop alkalinity.
ETHER‐SOLUBLE HYDROLYSIS PRODUCTS IN HUMIC AND FULVIC ACIDS
Authors: ANDERSON H. A. , HEPBURN A. , SIM A.
Published: July 2006

The major ether‐soluble products from the hydrolysis of humic and fulvic acids include levulinic, succinic and fumaric acids, accompanied by more variable amounts of 4‐hydroxy‐, 3‐methoxy‐4‐hydroxy‐, and 3,4‐dihydroxybenzoic acid. 3,5‐Dihydroxy‐benzoic acid was not detected in the hydrolysates examined.
IODINE IN SOIL PROFILES IN RELATION TO IRON AND ALUMINIUM OXIDES AND ORGANIC MATTER
Authors: WHITEHEAD D. C.
Published: July 2006

The iodine content in successive 10 cm horizons of eighteen soil profiles from England and Wales was determined and correlated with contents of‘free’ aluminium and iron oxides (oxalate‐soluble) and organic matter.

The pattern of change in iodine content with depth varied considerably with soil type. In the rendzina soils, the content was relatively high in the surface 10 cm but declined markedly with depth. In the podsols, iodine was low at the surface but increased in the B horizon: in one of these soils an iron pan of about 1 cm thickness had an iodine content as high as 37.6 mg/kg. In two soils derived from Ordovician, and one from igneous, rock material, the iodine content was relatively high (up to 25 mg/kg) with maximum values at intermediate depths. In contrast, soils derived from river alluvium and from lowland clays generally had low iodine contents (< 6 mg/kg) which showed little variation with depth in the profile. In a peat soil the iodine content was relatively high in the horizons above 60 cm but was low (1. 3 mg/kg) in the underlying clay.

In all 154 samples from the eighteen sites, iodine content was closely correlated with oxalate‐soluble aluminium (r= 0.834***) but not with oxalate‐soluble iron (r= 0. 35) or organic matter (r= 0.37). However, in the five most acidic soils, with pH below 4. 8, the iodine content was more closely correlated with iron than with aluminium.
COMBINED EFFECTS OF MOISTURE CONTENT PRIOR TO COMPACTION, COMPACTIVE EFFORT AND RAINFALL QUANTITY ON SOIL CRUST STRENGTH
Authors: HEGARTY T. W. , ROYLE SHEILA M.
Published: July 2006

Four levels of mechanical compaction (C) and six levels of subsequent simulated rainfall (R) were applied in all combinations to soil samples at five levels of moisture content (M) in the laboratory. After treatment, the soils were air‐dried to give uniform surface moisture contents and the crust strength was determined with a downward‐acting penetrometer. Almost 90% of the variation in peak penetration force was accounted for by an equation containing terms in R, CR, CM and CM2.
DISTRIBUTION OF SOME CHEMICAL ELEMENTS IN THE SOILS OF NORTH WEST PEMBROKESHIRE
Authors: BRADLEY R. I. , RUDEFORTH C. C. , WILKINS C.
Published: July 2006

Total amounts of Mn, Fe, Ni, Cu, Zn, As, Bt, Rb, Si, Y, Zr and Pb were determined in soil samples from approximately 250 profiles. Examples of automatically plotted maps show the distribution of some of these elements in topsoils and subsoils. Element distribution in the soils is related to land units based on underlying rock‐type and air photograph interpretation; these units distinguish soils of different lithological and drainage status and many are dominated by a single soil subgroup. Agricultural and pollution aspects of the work are discussed. The survey indicates the present levels of the elements, and may be used as a comparison in future pollution studies.
SOIL SAMPLER WITH RETRIEVABLE LINER
Authors: BLACK J. H. , RAINES M. G.
Published: July 2006

A simple, hand‐operated soil sampler based on commercially available drainpipe is described. The sampler is robust, avoids cross‐contamination of samples and can penetrate to a depth of three metres. The detailed design of, and a procedure for using, the sampler are given.
A MÖSSBAUER SPECTROSCOPIC STUDY OF THE EFFECT OF pH ON THE REACTION BETWEEN IRON AND HUMIC ACID IN AQUEOUS MEDIA
Authors: GOODMAN B. A. , CHESHIRE M. V.
Published: July 2006

Mössbauer specttoscopy has been used to provide information on the effect of pH on the nature of the complexes formed between iron and humic acid. At an initial suspension pH greater than 3 the iron occurs in the ferric form, although it is difficult to assess to what extent it is in combination with organic matter. On lowering the pH, iron is reduced with a considerable proportion of the ferrous iron entering solution, partly as a solvated ion and partly as complex forms. Raising the pH leads to re‐oxidation and the precipitation of a considerable proportion of the iron in an inorganic form with Mossbauer parameters similar to those of β‐FeOOH. No evidence was obtained for Fe(III) in solution or for Fe(II) in any form at pH values greater than 4.
VARIABLE ATMOSPHERE DTA IN IDENTIFICATION AND DETERMINATION OF ANHYDROUS CARBONATE MINERALS IN SOILS
Authors: WARNE S. St. J. , MITCHELL B. D.
Published: July 2006

The value of modem commercial DTA equipment in the identification and determination of anhydrous carbonate minerals can be greatly improved by incorporating a controlled‐atmosphere (carbon dioxide) technique. The unproved peak definition and increased height enables the detection of carbonate minerals at concentrations of the order of 0.25 per cent by weight in a 50 mg sample. Further, the related changes in temperature of the decomposition reaction peaks provide additional information for the identification of carbonate mineral reactions. The method has particular application in mineralogical and pedological investigations.
THREE EFFECTS OF TEMPERATURE ON THE REACTIONS BETWEEN INORGANIC PHOSHATE AND SOIL
Authors: BARROW N. J.
Published: July 2006

Phosphate was added to soil, incubated at a range of periods and of temperatures, and the rate of desorption was measured at several solution: soil ratios at 25°C. One sample was incubated at a high temperature for several days and the rate of desorption was measured at 5, 15, 25 and 38 °C. A regression approach was used to describe the results which were interpreted in terms of a model in which phosphate was present (a) in solution, (b) adsorbed in equilibrium with the solution, and (c) firmly held.

When neither adsorption nor desorption occurred, the phosphate concentration in solution increased with temperature. This was interpreted as an effect of temperature on the position of the equilibrium between solution phosphate and adsorbed phosphate. The direction of the effect indicates that adsorption was exothermic. When either adsorption or desorption occurred the rate increased with temperature and to a similar extent. For both reactions, the change in heat content was small. Thus, while temperature affected the rate of interchange between adsorbed and firmly‐held forms it should not affect the position of the equilibrium between these forms.
ROTHAMSTED STUDIES OF SOIL STRUCTURE 1.: PURPOSE OF THE PROJECT, SOILS SELECTED, AND GENERAL CONCLUSIONS
Authors: CURRIE J. A. , BULLOCK P. , THOMASSON A. J.
Published: July 2006

The agricultural background, morphology, and classification of soils from the Hans lope, Ragdale, Evesham, Denchworth, Flint and Salop series are presented together with basic analytical measurements of particle size and chemistry and with some details of the field water regimes. This information serves as essential background to other studies of soil structural properties as they relate to management of the same soils.
ROTHAMSTED STUDIES OF SOIL STRUCTURE IV.
Authors: CURRIE J.A.
Published: July 2006

Porosity and gas diffusion have been measured within dry crumbs sieved from the horizons of one soil from each of the Hanslope, Ragdale, Evesham, Denchworth, Flint and Salop series. Crumb porosities, ɛc, ranged from 0.19 to 0.33, dimensionless gas diffusivities, Dc/D0, from 0.015 to 0.098, and the effectiveness of unit pore space for diffusion, given by αc= (Dc/D0)/ɛc, from 0.06 to 0.29. Values of ɛc and Dc/D0 were used to calculate complexity factors kc for the crumb pores. The results are discussed in terms of soil texture, pore size, ease of soil management, and the frequency and intensity of wetting and drying of the soil in each horizon. None of the results suggests why the soils of the Ragdale, Denchworth and Salop series should be more difficult to manage than the others.
THE MEASUREMENT OF SOIL‐WATER HYSTERETIC RELATIONSHIPS ON A SOIL MONOLITH
Authors: TZIMAS E.
Published: July 2006

Soil water properties of an undisturbed uniform soil monolith were studied under laboratory conditions. Water content, hydraulic conductivity and soil water suction were measured simultaneously on a full cycle starting from saturation, drying to a small water content and then wetting until saturation was reached again.

The results showed clearly the hysteretic nature of the relations between water content and suction and between hydraulic conductivity and suction, but not between hydraulic conductivity and water content.
THE EFFECT OF POLY(VINYL ALCOHOL) ON THE CRUST STRENGTH OF SILTY SOILS
Authors: PAGE E. R.
Published: July 2006

Fourteen samples of soils were collected from localities in England where crusting and consequent depression of seedling emergence had been recorded. Natural aggregates of these soils were sprayed with poly(vinyl alcohol) (PVA), subjected to simulated heavy rain, and dried under IR lamps. In most soils, aggregate stability was enhanced by increasing applications of PVA and crust formation was prevented. Some soils, however, were unresponsive to PVA and crusts formed whether or not it was applied.

Responsive and unresponsive soils did not differ in particle size distribution, or porosity characteristics. Removal of iron oxides and organic matter did not alter their adsorption characteristics towards PVA. Unresponsive soils, however, were found to have the mineral chlorite as a major component and it is suggested that PVA is unable to bind particles together when the surfaces presented for adsorption of PVA consist of gibbsite, the interlayer material of chlorite.
ADSORPTION ISOTHERMS: SHOULD THEY BE SPLIT?
Authors: POSNER A. M. , BOWDEN J. W.
Published: July 2006

Langmuir adsorption isotherms are unlikely to be appropriate when applied to the adsorption of charged phosphate ions on charged oxide surfaces. It is more likely that the adsorption model proposed by Bowden et al. (1973, 1974 and 1977) for adsorption on variable charge variable potential surfaces will be applicable. Theoretical isotherms were calculated from this model for a series of pH values and ionic strengths. It is shown that these isotherms can be split into two or more Langmuir isotherms in much the same way as has been done by various authors for experimental isotherms. The parameters of the Langmuir isotherms behave in the same way as those derived from the experimental isotherms. The charging characteristics of the theoretical isotherms are also similar to that observed experimentally.

Because the model which is based on a single type of adsorption site is closely similar to the experimental isotherms, it is erroneous to split the isotherms into a series of Langmuir isotherms unless there are good a priori reasons.
FREEZING AND MELTING TEMPERATURE HYSTERESIS OF WATER IN POROUS MATERIALS: APPLICATION TO THE STUDY OF PORE FORM
Authors: HOMSHAW L. G.
Published: July 2006

A theory is developed for the influence of pore form on the equilibrium freezing and melting temperatures of water in porous materials. This is supported by calorimetry and uses the hysteresis between freezing and melting temperatures for two clays and undried synthetic organic textile fibres in which the pore geometry is that of intersecting cylinders.

For most water‐saturated clay systems, analysis of the low temperature endotherms gives a better appreciation of the pore size distribution than analysis of the exothermic data, unless the width of rectangular pores is known.
FORMATION, COMPOSITION AND STRUCTURE OF HYDROXY‐ALUMINOSILICATE IONS
Authors: WADA SHIN‐ICHIRO , WADA KOJI
Published: July 2006

Formation of hydroxy‐Al (HA) and hydroxy‐aluminosilicate (HAS) ions was studied in solutions of A1C13, orthosilicic acid and NaOH. Evidence for incorporation of Si into HA is that HA retarded the development of silicomolybdate colour and Si was retained by a cation‐exchanger. The reaction is believed to be mainly a condensation reaction between the hydroxyl groups in Al–OH–Al and Si–OH groups. The HAS with Si/Al ratio 0.3–0.6 showed infrared spectra similar to allophane‐like constituents in Ando soils.
LONG‐TERM CHANGES IN SOIL MACRO‐ AND MICROMORPHOLOGICAL PROPERTIES UNDER THE INFLUENCE OF PEAT DEBRIS
Authors: COLLINS J. F. , COYLE E.
Published: July 2006

Field morphological examination and thin section observations were made to document the effects of varying additions of acid peat debris to a mineral topsoil after a period of 25–30 years. Additions up to 3 cm improved soil physical properties and faunal activity relative to the unamended topsoil. Additions of 5–8 cm caused acidification, structural alteration and iron mobilization. Further additions, ranging up to 30 cm, caused progressive increase in acidification, reduction, structural collapse, faunal inactivity, etc. The formation of thick humus coatings (organans) and diffuse subsurface impregnations in the mineral soil is highlighted.
A COMPARISON OF THE SUITABILITY OF TWO SOILS FOR DIRECT DRILLING OF SPRING BARLEY
Authors: PIDGEON J. D.
Published: July 2006

A long‐term tillage experiment near Edinburgh on two soils types, one suitable for direct drilling and the other not, allowed comparisons to be made of soil responses to tillage and traffic.

For all tillage treatments tests, bulk density was always higher and air capacity lower on the soil unsuitable for direct drilling. Cone resistance, while dependent on treatment, was independent of soil type, The results suggested that compactability influences soil suitability for direct drilling.

Differences between soils in compactability were greater under direct drilling than other tillage treatments or in laboratory tests, probably due to the interaction of traffic and drainage regime. Drainage was not impaired under direct drillingon either soil type, despite significant reductions in macro‐porosity. Crop yields and root distribution in relation to soil physical conditions suggested the increased importance of subsoil conditions in direct drilling compared with ploughing systems.
WATER FLOW IN SOIL MACROPORES II. A COMBINED FLOW MODEL
Authors: SEVEN K. , GERMANN P.
Published: July 2006

This paper presents a one‐dimensional model of bulk flow in a combined micropore/macropore system, which has been developed as a result of the experimental work described in Part I. The problems posed by the presence of macropores to model development and validation are discussed and one exploratory model formulation is described. The results of several simulations are presented and used to demonstrate the effect of macropores on infiltration rates in soils of different hydraulic conductivity.
CROSS POLARISATION 13C‐N.M.R. SPECTROSCOPY OF SOME GENETICALLY RELATED NEW ZEALAND SOILS
Authors: WILSON M. A. , BARRON P. F. , GOH K. M.
Published: July 2006

Cross polarisation 13C‐n.m.r. spectra of seven New Zealand soils have been determined. Some of the soils are genetically related. The results show that the aromaticity of a soil may vary widely from soil to soil even when the parent material and vegetation are similar. The youngest of the soils examined (Hokitika, 300 years), was highly aromatic, and the oldest soil (Okarito, 22,000 years) was more aliphatic.
PORE CHARACTERISTICS OF SOILS FROM TWO CULTIVATION EXPERIMENTS AS SHOWN BY GAS DIFFUSIVITIES AND PERMEABILITIES AND AIR‐FILLED POROSITIES
Authors: BALL B. C.
Published: July 2006

Gas diffusivity and permeability, and air‐filled porosity, were measured in undisturbed soil cores at six water potentials between ‐2 kPa and oven dryness. All increased as water potential fell. In silt loam at 30 to 80 mm depth, relative diffusivity and air permeability at ‐2 kPa were 0.0013 and 5 × 10−8cm2 after direct drilling, and were 6 and 15 times greater respectively after ploughing, presumably because of the larger volume of air‐filled large pores in the ploughed soil. These pores may also have been more continuous or less tortuous than in the direct drilled soil. However, at equal air‐filled porosities up to 0.18 v/v, the pores were apparently more continuous and less tortuous in the direct drilled than in the ploughed soil. In the direct drilled silt loam at any given matric potential, air‐filled porosity, gas diffusivity and permeability within and below the previously ploughed layer were isotropic. In clay loam at 30 to 80 mm depth gas diffusivity and permeability at ‐2 kPa were greater than in the silt loam irrespective of tillage but increased less on oven drying.
THE CORRECTION OF IN SITU TENSIOMETER READINGS FOR OVERBURDEN PRESSURES IN SWELLING SOILS
Authors: TOWNER G. D.
Published: July 2006

An outline is given of some basic concepts relevant to a proper understanding of overburden pressure. It is shown that for swelling soils the overburden pressure must be known in order to infer water contents from in situ tensiometer measurements, but that it need not be known for the determination of hydraulic potentials from tensiometer readings.
EFFECT OF LIVING ROOTS OF DIFFERENT PLANT SPECIES ON THE AGGREGATE STABILITY OF TWO ARABLE SOILS
Authors: REID J. B. , GOSS M. J.
Published: July 2006

The influence of root growth and activities on soil aggregate stability was investigated using five crop species and two soils. Single plants were grown in pots for 6 weeks or less to minimise any possibility of changes in aggregate stability caused by decomposition of dead roots. Planted soils were compared with fallow controls. Aggregate stability was estimated by a turbidimetric technique (used for fresh and air‐dried samples) and by wet sieving (used for air‐dried samples only).

Root growth of perennial ryegrass and of lucerne for 42 days was generally associated with increases in aggregate stability whether the soil was tested in a fresh or an air‐dried condition. These beneficial effects were associated with periodate‐sensitive (probably polysaccharide) materials produced in the rhizosphere.

Growth of maize, tomato and wheat roots for 25 days decreased the stability of fresh soil aggregates, although the effects of tomato and of wheat were not consistent. However, the deleterious effects of these three species on aggregate stability were not apparent after air‐drying. The restabilization of maize soils (relative to fallow controls) on air‐drying appeared to be caused by increased stabilization by periodate‐sensitive materials.

The results suggest that the growth and activities of living roots may be a major factor controlling the overall direction and magnitude of changes in aggregate stability under arable or ley crops.
THE DISTRIBUTION OF LABELLED SUGARS IN SOIL PARTICLE SIZE FRACTIONS AS A MEANS OF DISTINGUISHING PLANT AND MICROBIAL CARBOHYDRATE RESIDUES
Authors: CHESHIRE M. V. , MUNDIE C. M.
Published: July 2006

Soils of the Countesswells and Insch series incubated with 14C labelled glucose or plant materials have been separated into clay (< 2 μm), silt, (2–20 μm), fine sand (20–250 μm) and coarse sand (>250μm) fractions and the distribution of individual labelled and unlabelled sugars was determined in each fraction.

Both soils contained about 10–15 per cent clay, 18–23 per cent silt and about 60 per cent fine and coarse sand. For all soil samples the concentrations of sugars were usually greatest in the clay, slightly less in the silt, with values in the sand fractions being five or ten times lower, except when fresh plant material was present.

In 14C glucose amended Insch soil, 55 per cent of the radioactivity in sugars (predominantly hexoses) occurred in the clay, 36 per cent in the silt, 3 per cent in the fine sand and 6 per cent in the coarse sand after 28 days incubation. For the Countesswells soil the values were 55, 42, 2 and 1 per cent respectively. In 14C ryegrass amended soil before incubation. 77 per cent of the radioactivity in sugars (predominantly glucose, arabinose and xylose) was in the coarse sand. After one year's incubation this had fallen to 59 per cent. In soil amended with 14C cereal rye straw the distribution of radioactivity in sugars after four years incubation was: clay, 21 per cent; silt, 43 per cent; fine sand, 21 per cent; coarse sand, 4 per cent.

These distributions were compared with that of the naturally occurring sugars: clay, 31–42 per cent; silt, 40–43 per cent; fine sand, 3–11 per cent; coarse sand, 12–20 per cent.