bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE 40K and 214BI (FROM 238U) CONTENTS OF ROTHAMSTED SOILS DETERMINED BY GAMMA SPECTROMETRY
Authors: SMITH G. J. , TALIBUDEEN O. 
Published: July 2006

SummaryThe gamma spectra of 17 surface soils from the Rothamsted Classical Experiments, selected for contrasting potassium and phosphate fertiliser treatments, were obtained to measure their contents of K and 214Bi (from 238U accumulated from phosphate fertilisers) contents, using the 40K and 214Bi photopeaks. The fate of the fertiliser residues are discussed for each Experiment, related to differences in fertiliser treatment and period of application. In 1978, potassium fertilisers increased soil K content by about 20% in Hoosfield (since 1852) and Barnfield (since 1843), and by about 7% in Broadbalk (since 1843). The K contents of the P and PNaMg plots in Barnfield suggest that Na substituted significantly for K in crop uptake. In Hoosfield and Barnfield (except the PK and PNaMg plots) phosphate fertilisers increased 2l4Bi contents, but did not affect it in Broadbalk.A new method for the quantitative determination of the content of any radionuclide emitting gamma radiation, and whose photopeak can be clearly resolved in the gamma spectrum of the soil, is described. This involves measurements on the soil and on the calibration samples containing radionuclides other than those to be assayed, using the same ‘sample:detector’ geometry, and the establishment of a calibration curve with reference sources in an energy range suitable for interpolating the results for the energy of the radionuclide. The values thus obtained are shown to compare very favourably with a direct method in which standards containing various amounts of the test radionuclide are used to calibrate the equipment. By using 1 kg samples of < 2 mm soil non‐destructively, both methods avoid sampling errors and the need for finely ground (< 0.15 mm) soil inherent in conventional chemical analysis.
THE KINETICS OF STRAW DECOMPOSITION IN RELATION TO ITS POTENTIAL TO PRODUCE THE PHYTOTOXIN ACETIC ACID
Authors: HARPER S. H. T. , LYNCH J. M. 
Published: July 2006

SummaryThe losses of total weight and of the individual components of oat straw were followed under field conditions over one cropping season. Decomposition rates of cellulose and hemicellulose were closely similar, and together these polysaccharides accounted for most of the weight losses. Losses of lignin were small, and total weight loss can be calculated from the increase in percentage lignin in recovered samples. Straw retained the potential to produce phytotoxic concentrations of acetic acid only during the early stages of decomposition. Both the water soluble components and the readily available polysaccharides are probably substrates for the production of acetic acid. Early incorporation of straw minimised the potential for toxin production during winter.
SOIL KAOLINS AND THEIR GENETIC RELATIONSHIPS IN SOUTHEAST QUEENSLAND, AUSTRALIA
Authors: KOPPI A. J. , SKJEMSTAD J. O. 
Published: July 2006

SummaryKaolin clays from soils in southeast Queensland give diffraction patterns which vary, particularly in the shape and position of the 00l reflections. To identify reasons for this variability, the kaolins in samples from forty soils were analysed for type, crystallinity, crystal size, and interstratification. Instrumental techniques used include X‐ray diffraction, infrared spectroscopy, and electron microscopy. Tiron‐extractable material was also determined.Properties of the clays are related to factors of soil formation; poor crystallinity of the kaolin and different amounts of Tiron‐extractable material are related to parent material. Kaolin of very small particle size (<0. 1 μm), is the main cause of broad 00l peaks and high basal spacing.
Thermodynamics of K‐Ni and Ca‐Ni exchange reactions on kaolinite clay
Authors: BANSAL O. P. 
Published: July 2006

SummaryExchange equilibria involving nickel ions on potassium and calcium kaolinites were studied using exchange isotherms and derived thermodynamic parameters. The equilibrium was attained within 3 h and maximum adsorption occurred at pH 5.5. The exchange at pH 5.5 and an equilibrium time of 3 h yielded isotherms, equilibrium constants and standard fne energy values indicating a higher preference for nickel ions on the kaolinite surface. A stronger binding of nickel ions on the kaolinite surface was suggested by the enthalpy changes and the entropy changes indicate an increase in order of the system which may be due to changes in hydration states of nickel, potassium and calcium ions. The surface‐phase activity coefficients of the cations showed that with increasing nickel saturation, in the Ca‐Ni system fNi continuously increased while fCa decreased; in the K‐Ni system fK first increased and then decreased while fNi first decreased and then increasad, which may be attributed to differences in the distribution of ions in the Gouy‐Stem layer. The excess thermodynamic functions showed that the exchange reactions were non‐ideal: that is the mixture of cations oh the kaolinite surface was more stable and more tightly bound than the homo‐ionic forms.
Effect of barley plants on the decomposition of 14C‐labelled soil organic matter
Authors: SPARLING G. P. , CHESHIRE M. V. , MUNDIE C. M. 
Published: July 2006

SummaryThe effect of barley plants on the rate of decomposition of soil organic matter over a 6‐week period was studied using soil that had been previously labelled by incubation with 14C‐labelled ryegrass for 1 year. The plants reduced the loss of 14CO2, from soil by 70 per cent over 42 days. About half of the reduction was accounted for by the uptake of labelled C by the plant roots, very little 14C label being associated with the shoot. Chemical fractionation of the root showed that the 14C was chemically incorporated into cell wall materials such as cellulose and holocellulose. The reduction in organic matter decomposition in the presence of plants has been explained by earlier workers in terms ofa reduction in microbial activity as a result of a soil moisture deficit caused by plant transpiration. This explanation does not account for all the reduction in decomposition noted in the present experiments. Control soil (without a plant, but amended with glucose oryeast extract to simulate the effect of root exudates) showed a small positive priming effect, the release of 14CO2, being increased. Thus the mechanism by which plants conserve organic matter is complex and cannot be explained merely by analogy to an increased level of nutrients available for microbial metabolism.
Effects of acetylene on nitrification and denitrification in two soils during incubation with ammonium nitrate
Authors: RYDEN J. C. 
Published: July 2006

SummaryA loam from the Frilsham and one from the Wickham Series were incubated at 50 and 90 per cent of their water contents at saturation with 100 μg NH4NO3‐Ng−1 soil in the presence and absence of C2H2 (0.5 per cent, v/v). Acetylene inhibited nitrification in both soils, but had no effect on mineralization of N. No denitrification (measured as the production of N2O in the presence of C2H2) occurred during incubation at 50 per cent saturation. At 90 per cent saturation, denitrification resulted in a loss of 28.4 and 36.7 μg Ng−1 after 48 h from the Frilsham and Wickham soils, respectively. The concurrent inhibition of nitrification had no effect on the extent of denitrification at this time. In the Wickham soil, NO3− was exhausted after 168 h incubation in the presence of C2H2 and denitrification was underestimated by 13 μg Ng−. The data suggested that concurrent inhibition of nitrification during measurement of denitrification using the C2H2 inhibition technique is most likely to affect the estimate of denitrification loss when NO3−supply is limited by the inhibition of nitrification.
The use of land form‐soil associations in irrigation soil surveys in northern Nigeria
Authors: CHARTRES C. J. 
Published: July 2006

SummaryThe problems of soil mapping for irrigated agriculture on the savanna landscapes near Kano are discussed. Using data from a detailed soil survey, the possibility of establishing the major variations in soil properties relevant to irrigation by landform‐soil association mapping is considered. In the landform classes identified, some soil textural and colour properties have within‐class variances somewhat lower than their between‐class variances, and moderate interclass correlations. The magnitude of the between‐class differences in these properties is great enough to indicate whether the soils can be irrigated successfully and to help determine the irrigation method. Other soil properties including infiltration rate and topsoil available water capacity also differ significantly between landform classes, but their within‐class variabdity is still relatively high, indicating the need for further investigations. The variability of most soil chemical properties across the area is not successfully accounted for by landform‐soil association mapping. The results suggest that landform‐soil association mapping can be a useful means of establishing imgability a feasibility survey level.
Predicting bare soil temperature. III. Extension to single‐day variation
Authors: BUCHAN G. D. 
Published: July 2006

SummaryThe theory developed earlier to describe the averaged diurnal wave of bare soil temperature for a many‐day interval is extended to single‐day variation. This gives a new analytic model for the soil thermal ‘weather’(as opposed to ‘climate’) under typical temperate seedbed conditions, with input meteorological data in standard time‐series form. The model incorporates (i) a ‘ramp’ term to account for overall linear ascent or descent (i.e. non‐cyclic change) in the surface temperature, TO; and (ii) the actual initial condition, θ(z), of the temperature profile, which expresses its effect through a transient term. Soil temperature T(z, t) thus has three distinct components‐periodic, ramp, and transient.The model is tested against data from a field site for I day each in spring and autumn.
Relationship between the decreases in soil stability effected by the growth of maize roots and changes in organically bound iron and aluminium
Authors: REID J. B. , GOSS M. J. , ROBERTSON P. D. 
Published: July 2006

SummaryThe growth of maize roots decreased fresh soil aggregate stability. Chemical pretreatment with sodium periodate (to assess the importance of polysaccharides) and acetylacetone (to assess the importance of organically bound Fe and Al) before measuring stability suggested that destruction of (organic matter)‐(Fe or Al)‐(mineral particle) linkages largely accounts for the effect. Removal of the Fe and Al cations by chelating agents released in the rhizosphere is the most likely mechanism. Changes in soil particle size distribution and the concentrations of water‐extractable cations around maize roots did not appear to be implicated.Concentrations of water‐extractable Mg and K were sometimes greater in fresh soil which had supported maize than in fallow controls, which may reflect both release of bicarbonate or organic anions by the roots and the slaking of aggregates, reducing stability of the fresh maize soils.
The potentiometric measurement of stability constants of soil polycar boxy late‐Cu2+ chelates
Authors: YOUNG S. D. , BACHE B. W. , LINEMAN D. J. 
Published: July 2006

SummaryStability constants describing Cu2+ combination with three natural and one synthetic polycarboxylates were calculated from pH measurements alone, and using a Cu2+ ion selective electrode. Good agreement between the two methods justified the theory for polymer‐cation association. The results were consistent with the formation of a single complex CuL2 over a fairly wide range of metal‐ligand (L) ratios. The stability constant (βHCu) that was independent of polymer charge allowed the prediction of copper speciation in soil solution as a function of pH and soluble organic matter.
High gradient magnetic separation of some soil clays from Nigeria, Brazil and Colombia.
Authors: HUGHES J. C. , LE MARE P. H. 
Published: July 2006

SummaryPhosphate sorption characteristics of the tropical soil clays described in Part I were determined. Estimates of native labile phosphate in the clays were similar to those calculated from whole soil data but under similar experimental conditions clays tended to sorb more exchangeable and less non‐exchangeable phosphate than whole soils. This may imply that short‐term measurements in soil underestimate the proportion of added phosphate that is labile and hence underestimate potential residual responses to fertilizer.Relationships of sorbed phosphate with iron (Feox) and aluminium (Alox) extracted by acid‐ammonium oxalate and with carbon differed between clays from Nigerian soils and those from South America. Exchangeable phosphate was related to Alox in both groups and to Feox in the Nigerian clays. In both groups of clays non‐exchangeable phosphate was related positively to Alox but its relationship with carbon was negative in the South American clays and positive in those from Nigeria. These relationships are compared with those in whole soils in which the ratio of metal to carbon in organic‐metal complexes is important.
Microscopical aspects of garnet weathering in a humid tropical environment
Authors: EMBRECHTS J. , STOOPS G. 
Published: July 2006

SummaryA sequence of different weathering stages of garnet under humid tropical conditions (Yaounde area, Cameroon) is described micromorphologically and mineralogically. The fissures, already observed in ‘fresh’ garnet in the rock, increase in number and size in the saprolite, and tend to get filled with well crystallized goethite. In this way a boxwork structure is formed. The isolated garnet fragments undergo a congruent dissolution, and the created space may be filled by gibbsite and/or globular Fe‐oxihydrates. In the A and B horizons a further dissolution of garnet and gibbsite takes place and all available space is filled with microcrystalline Fe‐oxihydrates. In this way a nodule, pseudomorph after garnet and with still recognizable boxwork‐structure, is formed. Near the soil surface these nodules may be transformed to haematite and/or undergo physical decay.Fresh garnets entering directly into the soil environment mainly undergo a physical decay and transformation to amorphous or microcrystalline Fe‐oxihydrates, without formation of a pseudomorph.
Modification of soil physical properties by addition of Fe (III) polycations: influence on plant growth
Authors: SHANMUGANATHAN R. T. , OADES J. M. 
Published: July 2006

SummaryThe addition of 0.07 per cent Fe or more in the form of polycations decreased the total area of cracks and increased the number of transmissive pores of soils after simulated rainfall and drying. This resulted in increased per cent emergence and lower mean day of emergence of wheat plants. Per cent emergence (.v) was negatively correlated with penetrometer resistance (x).The increased germination was followed by greater plant growth, including increased plant height and yield. The Fe polycation treatments had no significant effect on root length measured at harvest.
Variability of selected soil micronutrients in a single soil series in Berkshire, England
Authors: KHAN MOHAMMAD AFZAL , NORTCLIFF STEPHEN 
Published: July 2006

SummaryThe spatial variability of the concentrations of readily extractable iron, manganese, copper and zinc was examined in three 1 ha grids in close proximity within a single soil series. Estimates are given for the number of samples required to reach predetermined levels of precision. There were large contrasts between the grids and between the micronutrients. Iron and manganese showed greatest spatial variability and hence require the largest sample sizes, copper and zinc are less spatially variable.
The contribution of physics to land drainage
Authors: YOUNGS E. G. 
Published: July 2006

SummaryThe physics of land drainage is developed from the application of Darey's law to the water movement produced as a result of the conditions at the boundaries of the groundwater region in a given drainage situation. The physical understanding of the groundwater problem so obtained allows land drainage to be considered as an engineering operation founded on rational scientific principles and allows recommendations to be made concerning the design of installations. However, for theory to be applied in many field situations, a greater understanding of the soil‐water physics of heterogeneous soils, of fissured soils and of swelling soils is required.
The nitrogen content of particle size fractions separated from peat and its rate of mineralization during incubation
Authors: WILLIAMS B. L. 
Published: July 2006

SummaryParticle size fractions, varying from 5 to 0.005 mm, were separated from samples of several peat types using a wet sieving technique. In all types, nitrogen content of fractions increased as particle size decreased, the fine fractions (0.15–0.005 mm) accounting for around 43–64% of the total nitrogen. During incubation, fractions from two blanket peats showed a net release of mineral nitrogen, whereas those from raised bog peats were characterized, for the most part, by net immobilization. Amounts of mineral nitrogen released in fractions from any one peat after 28 days incubation at 30°C did not always correlate with either total nitrogen content or C:N ratio. However, better correlations between mineral nitrogen production and total N were obtained for fractions of similar particle size. The proportion of the total nitrogen that was mineralized tended to be higher in coarse fractions > 0.15 mm, blanket peats giving much higher values than samples from raised bogs. Carbon dioxide release also varied with particle size, being highest in large particles and fibres and least in the size range 0.15–0.5 mm. Smaller particles < 0.15 mm, gave intermediate values that were higher in blanket than in raised bog peat.
Geochemical mapping in Oxfordshire: a comparison of stream sediment and soil sampling
Authors: KINNIBURGH D. G. , BECKETT P. H. T. 
Published: July 2006

Summary352 stream sediments and 429 topsoils were sampled from 1000 km2 of SW Oxfordshire. These were analysed by direct reading emission spectrometry, and simple geochemical maps were prepared for ten elements (Ca, Sr, Ba, V, Cr, Mn, Fe, Co, Cu and Pb). The maps showed that (i) the unsmoothed data were very ‘noisy’, (ii) there was a weak overall similarity between stream sediment and soil maps for some elements (Ca, Cu, Fe, Mn, Sr and Co) but little if any for the others; and (iii) removing some of the short‐range (less than 3 km) variability from the data by smoothing increased the overall similarity in some cases, but not in others.Stream sediment and soil maps based on a more detailed sampling (topsoil and subsoil) of the area covered by map sheet SP30 did not show better agreement. The stream sediment maps generally agreed better with the subsoil maps than with the topsoil maps. Of the elements studied, Ca consistently showed the best agreement between stream sediment maps and soils. The agreement shown by the other elements was variable and unpredictable so that stream sediment data are unlikely to be useful for predicting local element concentrations in soils of areas without mineralization such as Oxfordshire.
Chloride dispersion in packed columns during saturated steady flow
Authors: RAUNSØ JENS 
Published: July 2006

SummaryChloride transport was investigated in four columns packed with glass spheres, spheres of a cation exchange resin, a loamy sand and a sandy loam, respectively. Using step input, vertical downward flow and relatively high flow‐rates, 0.01 m KCl displaced water in the column packed with glass spheres, otherwise 3.33 × 10−4m CaCl2 displaced or was displaced by 3.33 × 10−3m CaCl2. The breakthrough curves of chloride were analysed to give dispersion coefficients and mobile volumes. It was found that (i) chloride exchanged between mobile and immobile region in the sandy loam, (ii) the dispersion coefficient (K) was linearly related to pore flow velocity (U) for the individual columns, and that (iii) the ratio of dispersivity (dK/dU) to median grain diameter increased with increasing standard deviation of the logarithmicnormal grain size distribution.
The self diffusion of sodium in a naturally aggregated soil
Authors: STAUNTON S. , NYE P. H. 
Published: July 2006

SummaryThe self diffusion coefficient, in a naturally aggregated soil, of a solute which exists in both liquid and sorbed phases, was measured using a pulse labelling technique. This technique could have given evidence of slow equilibration between the two phases, but none was found. The magnitude of the self diffusion coefficient indicated that the solute is mobile in the sorbed phase. The mobility in the sorbed phase is described by a ‘virtual mobile fraction’. Within the limits set by the heterogeneity of natural aggregates, this was independent of both the volumetric moisture content and the bulk density.
Measurements of aeration in waterlogged soils: some improvements of techniques and their application to experiments using lysimeters
Authors: BLACKWELL P. S. 
Published: July 2006

SummaryThe techniques of measuring oxygen concentrations, oxygen flux and redox potential have been adapted for use in lysimeters. The accuracy and precision of the measurements have been improved, as well as their convenience for use in the limited soil volume of lysimeters.Concentrations of dissolved and gaseous oxygen are measured with a membrane covered polarographic electrode. The analysis is made on samples of air or solution carefully extracted from collection vessels permanently in the soil.Oxygen flux is measured with bare platinum electrodes. Careful choice is made of effective voltage for the measurement of equilibrium oxygen related currents.Redox potential is measured by the same platinum electrode and the reproducibility of measurements from permanently installed electrodes was assessed.The effect of soil structure upon the three kinds of measurement was seen and attributed to differences between the volumes of soil sampled by the different instruments.
Estimation of microbial biomass and activity in soil using microcalorimetry
Authors: SPARLING G. P. 
Published: July 2006

SummaryRelationships between the rate of heat output from soil, the rate of respiration and the soil microbial biomass were investigated for 25 soils from northern Britain. The rate of heat output, measured in a Calvet microcalorimeter at 22°C, correlated well with the rate of carbon dioxide respiration. The average amount of heat evolved per cm3 of gas respired. 21.1 J cm−3, suggests that the biomass metabolism was largely aerobic.The rate of heat output per unit of total microbial biomass was remarkably uniform over a wide range of soils, but showed differences depending upon whether the soil had been stored or amended. Mineral soils that had been stored at 4°C had the lowest heat output, 12.0 mW g−1 biomass C, compared with a mean of 20.4 mW g−1 biomass C for freshly‐collected soils. Amendment with glucose (0.5% w/w) caused an immediate increase in respiration and heat output, up to 59.4 mW g−1 biomass C for stored soils and 188.2 mW g−1 biomass C for freshly collected soils.There was a consistent relationship between the biomass and the rate of heat output from freshly collected and amended mineral and organic soils which gave a linear fit using log transformed data: y= 0.6970+ 1.025x (r= 0.98, P < 0.001) (y=log10 biomass C, μgC g−1; x=log10 rate of heat output at 22°C, μW g−1).The overall relationship between biomass and the rate of heat output for all the amended samples was: 1 g biomass C= 180.05 ± 34.61 mW.