bluuebunny/crossref_metadata_2025_split huggingface dataset:
CHANGES IN SOIL ORGANIC SULPHUR FRACTIONS DUE TO THE LONG TERM CULTIVATION OF SOILS
Authors: MCLAREN R. G. , SWIFT R. S. 
Published: July 2006

SummaryThe 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

SummaryThe 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

SummaryThe 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

SummarySamples 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

SummaryMeasurements 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

SummaryMercury 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

SummarySodium 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

SummaryThe 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

SummaryA 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

SummaryThe 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

SummarySoil 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

SummaryThe 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

SummaryIn 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

SummaryA 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

SummaryContinuous 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

SummaryThis 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

SummarySoil 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

SummaryA 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

SummaryExtractions 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

SummaryAnalysis 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

SummaryThe 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

SummaryThree 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

SummaryUsing 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

SummaryPhosphorus 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.