bluuebunny/crossref_metadata_2025_split huggingface dataset:
The morphology and genesis of eight surface‐water gley soils developed in till in England and Wales
Authors: MURPHY C. P. 
Published: July 2006

SUMMARYThe morphology is described of eight surface‐water gley soils developed in til in Wales and central and northern England. Physical and chemical analyses as well as micromorphological observations are used to investigate processes affecting the genesis of the soils.The characteristic property of surface‐water gley soils, namely slowly permeable subsurface horizons, causes a degree of periodie waterlogging within the profile. Effects of gleying and shrink/swell processes are described.Three main aspects of weathering are shown to be operating: decalcification in two of the three calcareous profiles, the breakdown of coarse into finer particles and the alteration of the clay fraction, chiefly the formation of mixed‐layer minerals from mica.Argillic B horizons are present in some soils. In profiles developed in calcareous till the degree of decalcification relates strongly to the amounts of recognizable clay concentrations as seen in thin section. Of the other five profiles three clearly have argillic B horizons. Problems associated with the identification of argillic B horizons in surface‐water gley soils in till are discussed.
Drilling vegetables into autumn‐cultivated soil with a low ground pressure vehicle: effects on timeliness and soil compaction
Authors: ROWSE H. R. , GOODMAN D. 
Published: July 2006

SUMMARYSecondary cultivations for the spring‐sowing of vegetables are often delayed because they cannot be carried out until the soil to the depth of cultivation has dried to the plastic limit (i.e. it crumbles rather than smears). It is suggested that doing secondary cultivations in the autumn, and then drilling in the spring without further cultivation, would be less liable to delays because only the soil down to the depth of drilling need dry below the plastic limit. Simple models are derived to calculate soil water contents from weather data. They show that between 1960 and 1981 the 0–120 mm layer (representing a typical cultivation depth) dried beyond the plastic limit for an average of 36% of the days between 14 February and 9 May, compared with 68% for the 0–30 mm layer (proposed system). Wheel sinkage, bulk density and cone resistance measurements showed that a tractor would cause excessive compaction when only the surface 30 mm was drier than the plastic limit, but this could be minimized by using a low ground pressure vehicle.
An assessment of an approximate analytic method for predicting breakthrough curves for steady state longitudinal dispersion of solute in soil with non‐uniform water distribution
Authors: TOWNER G. D. 
Published: July 2006

SUMMARYBreakthrough curves have been determined using an analytic solution of the dispersion equation for constant water content—set equal to the mean water content—and compared with those obtained for the actual water distribution using an analysis developed by Wilson & Gelhar (1981). Numerical analysis of selected examples confirmed the validity and accuracy of the latter method.The error in using the mean water content could become unacceptably large when the water content range was large or changed abruptly with distance, but was other‐wise small and probably negligible for many applications. It was not possible to devise simple criteria, but the method of Wilson & Gelhar is simple to apply, and it is unnecessary to consider alternative approximate methods.
Thermodynamics of K‐Ca exchange in soils
Authors: GOULDING K. W. T. , TALIBUDEEN O. 
Published: July 2006

SUMMARYThe standard and differential thermodynamic properties of K‐Ca exchange in soils from the Broadbalk (Batcombe series) and Saxmundham Rotation I (Beccles series) Experiments were evaluated for selected manurial treatments, using exchange isotherms and calorimetric measurements. The Beccles soil had a greater preference for K than the Batcombe soil in all the comparable treatments (Nil, PK and FYM). In all the soils, enthalpic forces favoured K preference but entropic forces Ca preference; in all but two cases the magnitude of the enthalpic forces were greater, resulting in K preference (positive ‐ΔGo). The ‐ΔHo values of the soils did not vary greatly, and the main cause of variation in ‐ΔGo values was that in ‐TΔSo values. Residual fertilizer K and FYM residues decreased preference for K at both locations, but more so at Broadbalk than at Saxmundham, presumably because of the greater duration and amount of K manuring at Broadbalk. FYM residues had a very complex effect on the exchange characteristics of Broadbalk soil. It is suggested that these differences are caused by the different pH values of the surface soils before they came into arable usage, which reflect their contrasting parent materials and pedogenic histories, and by the different durations and extents of manuring in the two experiments.
On estimating the uptake of nutrients solubilized near roots or other surfaces
Authors: NYE P. H. 
Published: July 2006

SUMMARYThe additional nutrient absorbed by a surface releasing a solubilizing agent is predicted. The ‘solubilizing effect’ is defined. The nutrient solubilized may diffuse away from the surface as well as towards it. If the change in solution concentration of nutrient and solubilizing agent at the surface are abrupt, the fraction of nutrient solubilized that is absorbed at a planar surface equals 1/(1 +√DY/DX), where DY, DX are the diffusion coefficients of the solubilizing agent and the nutrient. At a spherical surface this fraction has to be multiplied by 1/(1 +√πDY/t2a), and at a cylindrical surface, appropriate for a root, by approximately 1/(1 +√πDY/t4a), where a is the radius.
Denitrification losses from 15N‐labelled calcium nitrate fertilizer in a clay soil in the field
Authors: COLBOURN P. , HARPER I. W. , IQBAL M. M. 
Published: July 2006

SUMMARYCalcium nitrate fertilizer containing 92.3 atoms % excess nitrogen‐15 was applied on 5 May 1981 at a rate equivalent to 100 kg N ha−1 to a clay soil in southern England cropped to winter wheat. Samples of the soil gases were collected frequently during the following 3 weeks. The soil oxygen concentration declined to 5% after 60 mm rain. A maximum of 1.5 ± 0.5 atom % N‐15 enrichment in labelled N2 gas (29N2) was detected in the soil atmosphere on 28 May. Total denitrification losses, calculated from air‐filled pore space and rates of gas loss from the soil estimated using a Fick's law approximation, were 9.5 kg N ha−1 with a daily rate of 0.30 ± 0.07 kg N ha−1. Estimated total losses were greater than 30 kg N ha−1, 93% in the form N2, but the estimation depends on several assumptions about the amount of double labelled gas (30N2), rates of gas diffusion and flux.
Characteristics of soil organic matter in temperate soils by Curie point pyrolysis‐mass spectrometry.
Authors: BRACEWELL J. M. , ROBERTSON G. W. 
Published: July 2006

SUMMARYThis series of papers examines some significant differences in the constitution of organic matter found amongst major soil groups and their genetic and morphological horizons, as determined by the dynamic pyrolysis‐mass spectrometry of whole soil samples. Multivariate methods of data analysis identify groups of co‐variant mass ions which successfully partition samples in terms of the above soil categories, and correlate with other major properties such as humification and hydromorphism.This first study covers the A horizons from a group of 22 Scottish soils chosen from the major temperate soil groups including brown forest soils, podzols, and noncalcareous, peaty and humic gleys (phaeozems, cambisols, podzols and gleysols). The principal components analysis of 52 mass ion intensities was found to partition the soils successfully in terms of two main factors which represented 62% of the total statistical variance.The first factor was found to correspond closely to the extent of hydromorphism, being high for highly gleyed A horizons, and depended chiefly on the presence of aromatic hydrocarbon ions. The second factor corresponded to the extent of mull humus formation, being high for brown forest soils (phaeozems, cambisols) and low for podzols, and depended chiefly on the abundance of polypeptide products relative to polysaccharide products. This second factor was evidently a more comprehensive expression of a humification factor found in previous studies.The relationships of these factors with C and N content and with base status properties were examined.
Interpretation of leaching under multiple fertilizer applications
Authors: BARRY D. A. , ROSE C. W. , SAFFIGNA P. G. , PARLANGE J.‐Y. 
Published: July 2006

SUMMARYSimple theory has been developed and illustrated elsewhere which allows estimation, firstly, of the mean depth of solute penetration from any sequence of infiltration and evapotranspiration events, and secondly, of the apparent dispersion about this mean depth used as a Lagrangian coordinate system. This theory was used to analyse and interpret the time patterns of leachate concentrations of NO3‐N and Cl of a field lysimeter with a potato crop receiving four fertilizer applications and numerous inadvertent N and Cl applications by irrigation with groundwater. The assumption of superposition of estimated solute concentrations was employed in the analysis, yielding results consistent with the data. The analysis has quantified the leaching loss from each fertilizer application.
Charge characteristics and exchangeable cation status of Korean Ultisols and Alfisols and Thai Ultisols and Oxisols
Authors: WADA S.‐I. , WADA K. 
Published: July 2006

SUMMARYThe charge characteristics of A1 or Ap and B2 horizon samples of total 23 Ultisols, Alfisols and Oxisols in Korea and Thailand were studied by measuring the retention of NH4+ and NO3− at different pH values (4–8) and NH4NO3 concentrations (0.1–0.005 m). The magnitude of their negative charge (σ−; meq/100g) was dependent on pH and NH4NO3 concentration (C; m) as represented by a regression equation: log σ−=apH +blogC +c. The values of the coefficient a (0.04–0.226), b (0.03–0.264) and c (–0.676–1.262) were correlated with the kinds of the soil and horizon and with the region where the soil exists. The retention of NO3− was less than 1 and 2–3 meq/100 g for the A1 or Ap and B2 horizon samples, respectively.The sum of exchangeable base and Al (‘effective’ CEC) was close to and higher than the magnitude of permanent charge (=σ− measured at pH = 4.3 and at C = 0.005 m) for one‐third and two‐thirds of samples, respectively. A σ− value of 16 meq/100 g clay at pH = 7 and C = 0.01 m was found appropriate to separate the B2 horizons of Thai Ultisols and Oxisols from those of Korean Ultisols and Alfisols. Korean Alfisols and Ultisols and Thai Ultisols were distinguished from each other on the status of exchangeable base and Al
Extractable copper concentrations in Scottish soils
Authors: BERROW M. L. , REAVES G. A. 
Published: July 2006

SUMMARYThe distribution of ethylenediaminetetraacetic acid (EDTA)‐extractable Cu concentration levels in 3653 samples from 725 Scottish soil profiles is reported. The derived mean for the full set of data is 0.86 mg kg−1 and the normal range 0.08–9.8 mg kg−1. The relation of extractable Cu concentration to that of total Cu and to some other soil variables is also examined. Extractable Cu contents decrease with increasing depth over the first 50 cm and are almost constant below this.The correlation between total and extractable copper (r=+ 0.453) is statistically highly significant (P<0.001). The extractability (i.e. the percentage of total Cu extractable by EDTA) has also been considered in relation to the other soil variables. Extractability is inversely related to ash content though the relationship is not linear. Extractability is enhanced under conditions of impeded drainage but there is no indication that it is related to clay or sand contents.Approximately 18% of the arable topsoil samples contain levels of extractable Cu which are inadequate to supply the nutritional requirements of cereal crops and approximately 79% contain levels inadequate to support herbage with a Cu content sufficient to supply the requirements of grazing cattle.
Describing the effect of time on sorption of phosphate by iron and aluminium hydroxides
Authors: BOLAN N. S. , BARROW N. J. , POSNER A. M. 
Published: July 2006

SUMMARYIron and aluminium hydroxides were precipitated both in the presence and absence of kaolinite. The reaction between phosphate and these hydroxides was measured for periods which ranged from 5 min to 72 h. The effect of time on phosphate sorption was examined by plotting the sorption data according to different, simple, kinetic equations such as the first order, second order, the parabolic diffusion equation, the Elovich equation and the modified Freundlich equation. The effect of time on sorption was also examined by the mechanistic model recently developed by Barrow (1983b) for the sorption and desorption of phosphate by soils.The sorption of phosphate by iron and aluminium hydroxides increased with time and the reaction continued through the period of observation without reaching a true equilibrium. Curvilinear relationships were obtained when the data were plotted according to the simple kinetic equations. These simple kinetic equations fail to describe the effect of time on sorption partly because the mechanism is different from that postulated and partly because they do not consider electrostatic effects when phosphate ions react with a charged surface. The mechanistic model of Barrow (1983b), which takes this effect into account, described effect of both concentration and time on phosphate sorption. According to this model, the increase in phosphate sorption with time was caused by a redistribution of adsorbed phosphate into the interior of the particles of iron and aluminium hydroxides by solid‐state diffusion.
A survey of clover and Lotus rhizobia in Northern Ireland pasture soils
Authors: WOOD M. , COOPER J. E. , CAMPBELL D. S. 
Published: July 2006

SUMMARY192 sites covering the main soil types in Northern Ireland were analysed for numbers and effectiveness of clover and Lotus rhizobia, and chemical properties. Peat sites were generally highly acid (pH <5.5) and mineral sites near neutral (pH 5.5–7.8). Clover rhizobia were generally absent from peat sites and present in mineral sites as large populations (> 106 g−1 dry soil). 79% of isolates were effective on T. repens var. Grasslands Huia. Lotus rhizobia were generally absent from peat sites, less often present than clover rhizobia in mineral sites, and as smaller populations. They were mainly effective on L. pedunculatus var. G4705 and were all of the slow‐growing type belonging to the genus Bradyrhizobium. Numbers of clover rhizobia were significantly correlated with soil pH, exchangeable Ca, base saturation and Al saturation, but effectiveness of clover rhizobia and numbers of Lotus rhizobia were not correlated with any soil chemical property.
The dissolution and dispersion of dicalcium phosphate dihydrate in soils.
Authors: KIRK G. J. D. , NYE P. H. 
Published: July 2006

SUMMARYA model of the dissolution of a planar source of dicalcium phosphate dihydrate (DCPD) in soil is developed, with which to predict the calcium, phosphate and pH profiles formed by DCPD dissolving in an acid soil. The model comprises numerical solutions of partial differential equations describing the diffusion and reaction of calcium, phosphate and base in soil. The concentrations of calcium, phosphate and hydrogen ions in the soil solution at the mineral/soil boundary are found from the ion activity product of DCPD and by equating the fluxes of calcium, phosphate and base across the boundary. The derivation of the equations, the other boundary conditions, and the simplifying assumptions necessary for the solution of the equations, are discussed. The sensitivity of the model to its input parameters is assessed. The model provides a basis from which to advance to more complex geometries, and more complex fertilizers.
Gas diffusion in structured materials: the effect of tri‐modal pore size distribution
Authors: CURRIE J. A. , ROSE D. A. 
Published: July 2006

SUMMARYCoefficients of gas diffusion (hydrogen through air) were measured on packings of Portland stone chips over a range of water contents. The chips were obtained by crushing blocks of Portland stone on which similar gas diffusion measurements had been previously made. The packings had a tri‐modal pore‐size distribution: pores between the stone chips; pores within the chips but between ooliths; pores within the chips and within ooliths. As the water content of the packings was progressively decreased, the diffusion coefficient for the packings increased in three steps corresponding to successive drainage of the three pore modes. The previous results for the blocks were used to give good theoretical prediction of the three steps obtained by measurement. These results support earlier speculation that a similar stepwise increase in diffusion coefficient in soils might have been caused by micro‐pedal structure within soil crumbs.
Simultaneous nitrification and diffusion in soil. III. The effects of the addition of ammonium sulphate
Authors: DARRAH P. R. , NYE P. H. , WHITE R. E. 
Published: July 2006

SUMMARYThe simultaneous nitrification and diffusion of NH4+, applied as ammonium sulphate to laboratory columns, was followed experimentally and with a simulation model. Ammonium was applied as a fertilizer band at levels equivalent to 69 kg N ha−1 to a 1 cm depth. The concentration profiles of NH4+, NO3−, SO2−4 and pH were measured in two columns for incubation times of 214 and 286 h. The simulation model provided for the precipitation and ion pair formation of CaSO4, the adsorption equilibria of NH4+ and soil acid with the soil solid phase, and nitrifier growth and activity. In general, good agreement was found between the experimental and simulated concentration profiles. The effect of CaSO4 precipitation on the diffusion of N was investigated using model simulations of the diffusion of NH4+ in the absence of nitrification. The simulations suggested that the reactions of SO2−4 in the soil could markedly affect the spread of NH4+ from a band of (NH4)2SO4.
Effect of liming levels and Ca:Mg ratios on yield, nitrogen content and nodulation of soyabeans grown in acid Cerrado soil
Authors: MUCHOVEJ R. M. C. , BORGES A. C. , NOVAIS R. F. , THIEBAUT J. T. L. 
Published: July 2006

SUMMARYThe effect of four lime levels and of five ratios of Ca: Mg on nodulation, nitrogen fixation and yield of soyabean var. UFV‐1 was studied under greenhouse conditions, using a Typic Haplorthox soil. Dry matter production of top growth was relatively constant for soil Ca: Mg ratios ranging from 0.26: 1 to 24: 1 and a similar production level was sustained for A1 saturation values from 0 to 43%. Nodulation (number and dry weight of nodules) increased with increasing A1 saturation from 0 to 43%. The greatest increase was observed when Al saturation was raised from 0 to 2 or 3%. The N accumulated in the shoots, decreased with the increase in the percent A1 saturation, showing that the largest number of nodules does not necessarily result in greatest accumulation of N in shoots.
The possible effect of soluble silicon on the lepidocrocite content of gley soils from England and Bangladesh
Authors: KARIM Z. , NEWMAN A. C. D. 
Published: July 2006

SUMMARYNine different gley profiles from England and Bangladesh were studied; out of these, four English soils contained variable amounts of lepidocrocite. The amounts of lepidocrocite present in various layers of these soils decreased with increasing concentrations of Si(OH)4 in the soil solution. The amount of lepidocrocite formed was negatively correlated (r= ‐0.78) with the atomic ratios of Si/Fe in the citrate/dithionite extracts.Lepidocrocite was absent from the other five profiles, including three surface water gley soils from Bangladesh. These soils contained relatively large concentrations of Si(OH)4 in soil solution, ranging between 0.7 mm and 1.0 mm. The atomic ratio of Sid/Fed in the citrate/dithionite extracts was higher in these soils. Enborne soil contained maximum amount of citrate/dithionite extracted silicon (2.30 mg g−1) with no X‐ray crystalline iron oxides in the profile.
Testing a mechanistic model. IV. Describing the effects of pH on zinc retention by soils
Authors: BARROW N. J. 
Published: July 2006

SUMMARYSamples of two soils were incubated at 60°C for 24 h with several levels of either calcium carbonate or hydrochloric acid. Zinc retention was then measured on subsamples of the treated soil over 24 h at 25°C. The results were compared with published experiments (Bar‐Yosef, 1979; Harter, 1983) in which zinc retention was also measured over a range of concentrations and pH values, but using different experimental conditions.Zinc retention increased as pH increased. In all cases, this effect could be described by assuming that the ZnOH+ ion was retained and the effect of pH was due to the increased proportion of this ion in solution. Over most of the pH range it was not necessary to assume any contribution from a decrease in the electrostatic potential of the reacting surfaces with increasing pH. This contrasts with the effects of pH on phosphate and fluoride retention and suggests that the materials that react with zinc differ from those that react with anions.The shape of plots of zinc retention against ZnOH+ concentration was reproduced using a model in which it was assumed that there was a range of values of electrostatic potential. A similar model had previously been used for anions. Zinc would tend to react with the most negative end of this range and phosphate with the least negative end. This further suggests that zinc and anions may react with different materials.
Simultaneous nitrification and diffusion in soil
Authors: DARRAH P. R. , NYE P. H. , WHITE R. E. 
Published: July 2006

SUMMARYA short‐term nitrification assay was used to investigate the relationship between pH and nitrification rate. The resulting pH relation was included in a model that simulated the time‐course of nitrification over a 16–day period. The predictions from this model corresponded closely with measured nitrate concentrations in contrast to a similar model that did not include the response of the nitrifiers to pH change.The simultaneous nitrification and diffusion of ammonium sulphate, applied as a band of fertilizer equivalent to 69 kg N ha‐1 to a 1 cm depth, was followed experimentally in a soil column incubated for 382 h. The measured concentration profiles of ammonium, nitrate and pH agreed well with those predicted by a simulation model that included the effect of pH on nitrification, while profiles predicted by a model that neglected the effect of pH agreed poorly with the experimental results.
The dissolution and dispersion of dicalcium phosphate dihydrate in soils
Authors: KIRK G. J. D. , NYE P. H. 
Published: July 2006

SUMMARYThe model developed in part I to describe the dissolution of a planar source of DCPD in soil is extended to deal with the dissolution of particles, allowing for diminution of the particles as they dissolve and the interaction of neighbouring particles. The model has nine input parameters: concentrations of calcium and phosphate in the unamended soil solution, unamended soil pH, phosphate and lime potential buffer capacities of the soil, volumetric moisture content, diffusion impedance factor, and rate of application and particle size of the DCPD. A sensitivity analysis of the model showed that the rate is particularly dependent on particle size, rate of application, and the pH and concentration of calcium in the soil solution. If the particles are so far apart that they do not influence each other, after the very early stages the rate of dissolution is independent of the soil buffer terms. But for typical rates and methods of application, neighbouring particles will influence each other, and the consequent interactions between the rate‐determining variables are complex.