bluuebunny/crossref_metadata_2025_split huggingface dataset:
RELATIVE EFFECTS OF TRACTOR WEIGHT AND WHEEL‐SLIP IN CAUSING SOIL COMPACTION
Authors: DAVIES D. B. , FINNEY J. B. , RICHARDSON S. J. 
Published: July 2006

SummaryThe results presented are from field studies in which soil compaction was measured under tractors working with different wheel loads and levels of wheel‐slip. Wheelslip proved to be more important in causing compaction than additional wheel loading, and this effect was more pronounced for more powerful tractors. In most agricultural circumstances the aim is to secure the best compromise between weight and slip as alternative means of achieving greater work output from tractors. The results indicate that in situations where there is a need to avoid compaction, particular attention should be given to providing sufficient wheel loading and the possibility of moving faster to take up more power at lower slip.For the range of soil moistures encountered sinkage was the most convenient and satisfactory method of assessing total reduction in porosity, and differentiated between treatments better than any of the other methods (see below) apart from water‐entry rates.Measurement of soil density at three levels to 15 cm depth accounted for less than 50 per cent of the loss of porosity estimated from sinkage and the method did not detect differences due to treatment.Shear strength measured at one depth (3.5 cm) differentiated between treatments, but penetration resistance at 7.5 cm did not. Water‐entry rates sensitively detected treatment differences but the method was too time‐consuming for comparison of all treatments.The efficiency of traction of four‐ and two‐wheel‐drive tractors was measured at intervals during the winter on a clay loam and the results related to surface moisture contents. After a steep reduction in efficiency, when the soil returned to field capacity, subsequent changes in efficiency were small.
ANION ADSORPTION BY GOETHITE AND GIBBSITE
Authors: HINGSTON F. J. , POSNER A. M. , QUIRK J. P. 
Published: July 2006

SummaryThe desorption of specifically adsorbed (ligand exchanged) anions, such as phosphate, selenite, and fluoride, from the surface of gibbsite and goethite has been studied by repeatedly washing the adsorption complex with solutions of constant pH and ionic strength but containing no specifically adsorbable anions. The desorption of the anions varies between complete reversibility and almost complete irreversibility. Measurements of surface charge by the uptake of Na+ and Cl‐ revealed that, on washing the adsorption complex, the surface charge returned to its value at the given pH in the absence of specifically adsorbed anions. Thus when the isotherm was irreversible, OH‐ was desorbed (or H+ adsorbed) in preference to the desorption of the specifically adsorbed anion, whereas when the isotherm was reversible the specifically adsorbed anion was desorbed.Irreversibility appears to involve the nature of the adsorption complex at the surface. Where only monodentate ligands form, for example fluoride adsorption, the isotherm is reversible, whereas bridging or multidentate ligands and the formation of ring structures at the surface favour irreversibility.
A METHOD FOR SOIL PARTICLE‐SIZE ANALYSIS USING ULTRASONIC DISAGGREGATION
Authors: PRITCHARD D. T. 
Published: July 2006

SummaryA method for routine particle‐size analysis of soils is described which is quicker than methods using peroxide. Organic matter is destroyed by ignition at 400°C and an ultrasonic bath is used for disaggregation.The efficiency of ultrasonic baths for this purpose is affected by the temperature, aeration status, and depth of water in the tank; the nature, size, and depth of immersion of the sample vessel; and also the ratio of solid to liquid in the sample vessel.Standardization is preferably based on the effect of treatment on standard materials, rather than the energy output of the apparatus used.It is difficult to differentiate between aggregates and primary particles, and to choose a method applicable to all soils.
A COMPARISON OF THE SORPTION OF INORGANIC ORTHOPHOSPHATE AND INOSITOL HEXAPHOSPHATE BY SIX ACID SOILS
Authors: ANDERSON G. , WILLIAMS E. G. , MOIR JACQUELINE O. 
Published: July 2006

SummaryA comparison has been made of the sorption of inorganic orthophosphate and inositol hexaphosphate by six acidic surface soils from arable land in north‐east Scotland. The sorption of inorganic P increased with increasing quantities added and tended towards a maximum, but was never complete. In contrast, the organic P was completely sorbed up to an added quantity which varied with the soil, and above this level the absolute sorption decreased, probably due to the formation of soluble complexes involving iron and aluminium. The sorption sites were apparently the same for the two P forms and, particularly at high levels of addition, the organic P depressed the sorption of inorganic P. Inorganic P did not depress the sorption‐of organic P, which was preferentially adsorbed. The results help to explain the extreme stability of inositol hexaphosphate in these soils.
SOME EFFECTS SUB‐SURFACE DRAINAGE AND PLOUGHING ON THE STRUCTURE and COMPACTABILITY A CLAY SOIL
Authors: STEINHARDT REUVEN , TRAFFORD B. D. 
Published: July 2006

SummaryIn a field experiment to determine the direct and indirect effect on soil structure, of sub‐surface piped drainage as compared with natural surface drainage only, in ploughed and unploughed soil, a factorial systematic design with four replicated blocks was used. Structural changes were monitored during 8 months of natural rain and finally irrigation, by measuring surface heights and soil strength (penetration resistance) in relation to moisture content and matric suction, at plough sole depth (27 cm). A compaction test using a tractor with differentially loaded wheels, was applied at various times after irrigation, measuring the resulting wheel sinkage and wet density of the soil.The effects of the drainage treatments were found to be temporary, except a ‘crusting’ effect during the drying of the unploughed surface drained soil. The ploughed soil with sub‐surface drainage showed greater frost heave than the undrained soil. The soil strength at 7.5‐22.5 cm. depth was linearly related to the matric suction within the range of –3 to 20 cm‐water. The compaction data for the unploughed soil suggested relationships between matric suction, sinkage, and wet density, but complicated interactions prevented any general conclusion. In the ploughed soil, compaction data established the beneficial effects of subsurface drainage in reducing damage from tractor traffic, decreasing wheel sinkage and reducing compaction both below and 16 cm from the track edge. A rise in matric suction of 10 cm‐water, in the range 2‐24 cm‐water was, on the average, as effective in reducing rutting as a wheel load reduction of 670 kg (0.54 kg/cm2 reduction of tyre inflation pressure). It was concluded that for clay soils having a temporary excess moisture, draining the water table to below 50‐60 cm depth should be recommended as a precautionary measure to minimize structural damage.
FIELD STUDIES OF THE SOIL ATMOSPHERE II. OCCURRENCE OF NITROUS OXIDE
Authors: DOWDELL R. J. , SMITH K. A. 
Published: July 2006

SummaryStudies were made of the seasonal changes in the occurrence of nitrous oxide in the atmosphere of two clay soils. During the winter of 1971‐2 the nitrous oxide concentrations at both sites were in the range 20‐50 ppm. Levels increased with rising soil temperatures in spring, the mean values reaching 50‐170 ppm in May; some individual samples contained 1500‐6500 ppm. The level of nitrous oxide was inversely related to the oxygen content of the soil atmosphere and was also correlated with the nitrate and nitrite concentration of the soil water, but could not be correlated with either the proximity of field drains, soil moisture content or rainfall.
THE NATURE OF ALKALI‐SOLUBLE SOIL ORGANIC PHOSPHATES
Authors: ANDERSON G. , MALCOLM R. E. 
Published: July 2006

SummaryFractionation of the phosphates in a sodium hydroxide extract of an arable soil has shown the presence of a number of esters of a type not previously detected in soils. These included several mono‐phosphorylated carboxylic acids with C to P ratios of approximately 7 or 8 to I and two esters each containing glycerol, myoinositol, chiroinositol and an unidentified component. Another ester, probably containing two phosphate groups, was also detected but was not completely separated from other compounds containing no P. These esters constituted only approximately 3 per cent of the total soil organic P but considerable losses of organic P occurred during the extraction and isolation procedures. The amounts of the inositol phosphates, nucleoside phosphates, and inorganic pyrophosphate in the extract were also measured.
A NOTE ON THE PLASTICITY LIMITS OF AGRICULTURAL SOILS
Authors: TOWNER G. D. 
Published: July 2006

SummaryThe plasticity limits of seventeen agricultural soil standards representing contrasting textures, were measured both by the standard methods and by the fall‐cone penetrometer method (Towner, 1973). The results are compared with the Casagrande A‐line in the plasticity chart. The plasticity limits obtained by the fall‐cone method are given for twelve other soils. The plasticity indices for the soils tended to lie about a single curve. They lay above the Casagrande A‐line at low values of liquid limit. There was some suggestion of an order according to texture along this curve.
THE EFFECT OF FREE AND CLAY‐BOUND HUMIC MATTER ON THE UPTAKE OF SULPHATE BY ROOTS
Authors: DELL'AGNOLA G. , FERRARI G. 
Published: July 2006

SummaryHumic substances stimulate the amount of sulphate actively transported by excised barley roots to an extent depending on the humification pattern of the original soil organic matter. Humic fractions separated on Sephadex differ in their effects on the active transportation of sulphate by roots; both the carboxyl‐to‐phenolic OH ratio and the molecular weight strongly affect the biological activity of the fractions. In contrast, the procedure used to extract the humic material (sodium hydroxide or sodium pyrophosphate) has little influence. When the humic material is complexed with montmorillonite, sulphate uptake is further enhanced.
IDENTIFICATION OF PHOSPHATE‐REACTIVE SITES OF HYDROUS ALUMINA FROM PROTON CONSUMPTION DURING PHOSPHATE ADSORPTION AT CONSTANT pH VALUES
Authors: RAJAN S. S. S. , PERROTT K. W. , SAUNDERS W. M. H. 
Published: July 2006

SummaryThe amounts of hydroxyl ions released from hydrous alumina during phosphate adsorption were measured at constant pH values and at different phosphate concentrations using an automatic titrator. The hydroxyl ions released were plotted against phosphate adsorbed and the equations that gave best fit to the data were differentiated. The variation in the differentials (dOH/dP) with increasing phosphate adsorption was consistent with the theory, proposed below, on the type of sites responsible for phosphate adsorption, by synthetic hydrous alumina containing bayerite and pseudoboehmite, at different concentrations.At low phosphate adsorption which corresponded to low phosphorus concentration, adsorption took place mainly by displacing aquo groups (Al‐H2O). With increase in phosphorus concentration hydroxo groups (Al‐OH) became the predominant sites of adsorption.At still higher concentrations, where phosphate adsorption displacing aquo and hydroxo groups was nearly completed, the hydroxyl bridges linking aluminium atoms (Al‐OH‐Al, ol groups) were broken. This created new sites which were responsible for additional adsorption of phosphate at these concentrations.
KINETICS OF ION EXCHANGE IN SOIL ORGANIC MATTER
Authors: BUNZL KURT 
Published: July 2006

SummaryThe rate of ion exchange reactions of humic substances (humic acid and peat) with lead ions was investigated at 25 °C. All experiments were carried out under finite solution‐volume conditions. To the well‐stirred aqueous suspensions of the above samples lead ions were added in such small amounts that, after attainment of the equilibrium, the initial equivalent fraction of lead in the humic substance had increased only by a small amount. The kinetics of such differentially small ion exchange processes were studied as a function of the initial lead content of the samples. The experiments showed that the absolute rates for the uptake of small amounts of lead ions decrease, if the initial lead content of the samples increase. The relative rates of ion exchange, i.e. the rates with respect to the extent of each reaction, showed a more complicated behaviour, as they can exhibit a minimum at a certain initial lead content of the sample. The rate‐determining step of the above ion exchange experiments was shown, by interruption tests, to be diffusion of the ions through the Nernst‐film surrounding the ion exchanger particles.Theoretical calculations of the rates of film‐diffusion controlled ion exchange processes were carried out and the results revealed that the rates of any differential ion exchange reaction should decrease with increasing initial content of the ion adsorbed, their exact magnitude depending, among other quantities, strongly on the separation factor. The relative rates for the attainment of the equilibrium, on the other hand, depend much less on the initial ionic composition of the ion exchanger. A comparison of the experimental and the calculated results yields satisfactory agreement if the experimentally determined dependence of the separation factor on the lead content of the samples is taken into account.
THE EFFECT OF LIGHT ON THE ESR SPECTRA OF HUMIC ACIDS
Authors: SLAWINSKA D. , SLAWINSKI J. , SARNA T. 
Published: July 2006

SummaryPhoto‐induced Electron Spin Resonance signals have been detected in basic aqueous solutions of humic acids from soil and from synthetic and commercial sources. Parameters of these signals under atmospheres of air, O2 and N2 were the same as or very similar to those of the already known ‘dark’ stable ESR‐signals of humic acids and melanins. The maximum increase of signal amplitude under the influence of 395–780 nm wavelength irradiation was one order of magnitude. The influence of microwave power on ESR‐signal amplitude was examined under different atmospheres. It has been found that oxygen strongly diminishes the saturability of signals. This indicates that oxygen has an influence upon relaxation properties of paramagnetic centres of humic acid. Photoinduced ESR signal is a newly discovered feature of humic acids, similar to that of melanin and may be expected to affect physico‐chemical processes occurring in soils.
MOLECULAR WEIGHT DISTRIBUTION OF SOIL ORGANIC MATTER AS AFFECTED BY ACID PRE‐TREATMENT AND FRACTIONATION INTO HUMIC AND FULVIC ACIDS
Authors: GOH K. M. , REID M. R. 
Published: July 2006

SummaryEffects of acid pre‐treatment and fractionation on the molecular weight distribution of OIM Na4P2O7 organic matter extracts were investigated in a chronosequence of weakly weathered soils developed on aeolian sand in New Zealand.Acid pre‐treatment of soils with OIM HCl followed by OIM HCI:03M HF was found to enhance the polydispersion in the nominal molecular weights of the extracts. The same treatment resulted in significant increases in yield and reduction in ash content. However, prolonged standing of extracts in the acids led to acid‐induced polymerization, resulting in a predominance of organic matter in the higher nominal molecular weight ranges.Fractionation of organic matter extracts by acid precipitation into humic and fulvic acids did not separate them according to molecular weight as commonly believed. Instead, fulvic acids from most soils were found to have similar nominal molecular weight distributions to those of their humic acid counterparts. A large proportion of soil fulvic acid compounds was in the > 100 000 nominal molecular weight range.
THE USE OF THE FREUNDLICH ISOTHERM FOR SOIL PHOSPHATE SORPTION DATA
Authors: FITTER A. H. , SUTTON C. D. 
Published: July 2006

SummaryPhosphate sorption data for twenty‐nine soils were found to fit the Freundlich adsorption isotherm better if a measure of native labile P was first added to the sorption data, and this sum plotted against intensity. The exponent from the isotherm thus obtained was closely related to exchangeable A1 (in acid soils) and exchangeable Ca (in neutral and calcareous soils), with a mole ratio of one P to 6 A1 or Ca.
DETERMINATION OF THE STRUCTURAL STABILITY CLASS OF ENGLISH AND WELSH SOILS, USING A WATER COHERENCE TEST
Authors: GREENLAND D. J. , RIMMER D. , PAYNE D. 
Published: July 2006

SummaryThe structural stability of samples of 180 soils of known composition was examined by the Emerson test. This test is based on the swelling, slaking, and dispersion behaviour of soil aggregates when immersed in water and under mechanical stress.In the surface soils investigated there appeared to be a critical level of organic matter, corresponding to 2 per cent organic carbon, below which soils were very liable to structural deterioration especially in the absence of calcium carbonate. Exceptions occurred and are discussed in relation to soil composition.A very few soils gave variable or indeterminate results and on these the tests were repeated on larger numbers of aggregates. Most soils were readily classified into one or other of the eight classes recognized by Emerson, and the test is a simple and convenient way of distinguishing soils likely to have structural problems in the field.
THE EFFECT OF THE EARTHWORM DENDROBAENA RUBIDA ON THE SOLUBILITY OF LEAD, ZINC, AND CALCIUM IN HEAVY METAL CONTAMINATED SOIL IN WALES
Authors: IRELAND M. P. 
Published: July 2006

SummaryThe quantities of lead, zinc, and calcium dissolved by various extraction techniques from soil, earthworm faeces, and decayed earthworm (Dendrobuena rubida, Savigny) corpses have been studied.A small proportion of the total metals was water soluble and the amount of lead in faeces was significantly higher than in soil. Putrefied earthworm extracts gave by far the highest concentrations of all three metals.Acetic acid extractable lead was higher in soil than faeces but putrified earthworm extracts gave the highest concentration of lead. The quantities of zinc and calcium extracted were lowest in soil, higher in faeces, and much higher in decomposed earthworms.This particular species of earthworm can therefore be considered as a possible source of lead and zinc contamination in heavy metal polluted, acid soil.
FIXED AMMONIUM IN NIGERIAN SOILS
Authors: OPUWARIBOI E. , ODU C. T. I. 
Published: July 2006

SummaryIn soil profiles from Nigeria native fixed ammonium was positively and significantly correlated with per cent silt, per cent clay, per cent silt plus clay, pH, exchangeable potassium and cation exchange capacity but not with exchangeable ammonium or organic matter. The results of multiple and partial regression analyses indicated that native fixed ammonium was most closely correlated with per cent clay, exchangeable potassium, and cation exchange capacity.
FIXED AMMONIUM IN NIGERIAN SOILS
Authors: OPUWARIBOI E. , ODU C. T. I. 
Published: July 2006

SummaryThe ability of the organic and inorganic soil components to fix added ammonium was assessed using 15N as a tracer. In surface soils between 20 and 90 per cent of the ammonium retained after four cycles of alternate wetting and drying was due to organic matter. In subsoils containing little organic matter ammonium was fixed almost exclusively by layer silicate minerals.
THE DETERMINATION OF DESORPTION ISOTHERMS FOR SOIL PHOSPHATE USING LOW VOLUMES OF SOLUTION AND AN ANION EXCHANGE RESIN
Authors: BREWSTER J. L. , GANCHEVA A. N. , NYE P. H. 
Published: July 2006

SummaryPhosphate desorption isotherms were determined (a) by shaking 1 g soil with 3 ml 0.01M CaCl2 solution plus different amounts of an anion exchange resin, and (b) by diluting soil with different volumes of 0.01M CaCl2 solution. Adsorption isotherms were determined using a soil to solution ratio of 1 g to 3 ml. In soils of intermediate P status adsorption isotherms appeared continuous with desorption by method (a), but not with desorption by method (b), which predicted lower buffer powers than did (a). Method (a) led to increases and (b) to decreases in pH. Additions of dissolved silica had no influence on P desorption by method (b).
RATIONALIZATION OF IONIC STRENGTH AND CATION EFFECTS ON PHOSPHATE SORPTION BY SOILS
Authors: RYDEN J. C. , SYERS J. K. 
Published: July 2006

SummaryThe amounts of inorganic phosphate (P) sorbed by four contrasting unfertilized soils during 40 h were influenced by the ionic strength and cation species of the contacting solution (support medium) used, as indicated by isotherms over the final P concentration range of 0 to 1 μg P/ml and 0 to 10 μg P/ml. An increase in ionic strength enhanced P sorption during 40 h but the species of cation also influenced the amount of P sorbed, as shown by the isotherms obtained in 10−2M Ca and 3 × 10−2M Na systems. Although pH affected the amounts of P sorbed, pH effects alone could not adequately explain the differences in P sorption. Kinetic studies indicated that within the range of P addition used for each soil, the equilibrium P concentration, at infinite time, was independent of ionic strength and cation species. Consequently, the composition of the solution affected only the rate at which equilibrium was attained. The results are attributed to the effects of ionic strength on the surface charge of retaining components and the thickness of the diffuse double layer, and the effects of specilic sorption of a divalent cation on surface charge, as they relate to the rate of P sorption.
THE HIGH‐ AND LOW‐ENERGY PHOSPHATE ADSORBING SURFACES IN CALCAREOUS SOILS
Authors: HOLFORDI I. C. R , MATTINGLY G. E. G. 
Published: July 2006

SummaryThe two‐surface Langmuir equation was used to study P adsorption by 24 calcareous soils (pH 7.2‐7.6; 0.8‐24.2 per cent CaCO3) from the Sherborne soil series, which are derived from Jurassic limestone. High‐energy P adsorption capacities (x″m) ranged from 140–345 μg P/g and were most closely correlated with dithionite‐soluble Fe. Hydrous oxides therefore appear to provide the principal sites, even in calcareous soils, on which P is strongly adsorbed (x″m 6–51 ml/μg P). The low‐energy adsorption capacities (x″m) ranged from 400–663 μg P/g and were correlated with organic matter contents and the total surface areas of CaCO3 but not with per cent CaCO3, pH, or dithionite‐soluble Fe. Total surface areas of CaCO3 in the soils ranged from 4.0 to 8.5 m2/g soil. Low‐energy P adsorption capacities agree reasonably with values (100 pg P/m2) for the sorption of phosphate on Jurassic limestones but phosphate was bonded much less strongly by soil carbonates (k″= 0.08–0.45 ml/μg P) than by limestones (k∼10.0 ml/μg P). Low‐energy P adsorption in these soils is tentatively ascribed to adsorption on sites already occupied by organic anions (and probably also by bicarbonate and silicate ions) which lessen the bonding energy of co‐adsorbed P.
A SIMPLE AND RAPID METHOD OF SOIL WATER DETERMINATION
Authors: AGGARWAL G. C. , TRIPATHI B. R. 
Published: July 2006

SummaryA wide‐mouthed pycnometer was employed for rapid determination of soil water. The principle involved is to weigh the pycnometer when filled with the soil sample and water. The particle density of soil needs to be known. There is no necessity to add exact volumes of water. For the 7 soils studied, the water content values obtained by the proposed method were similar to those by oven‐drying.