bluuebunny/crossref_metadata_2025_split huggingface dataset:
Diffusion of coefficients of carbon dioxide, nitrous oxide, ethylene and ethane in air and their measurement
Authors: PRITCHARD D. T. , CURRIE J. A. 
Published: July 2006

SummaryBinary diffusion coefficients were measured by a steady‐state method in which a gas was introduced at a constant rate into one end of a tube through which it moved by mass flow and diffusion into a semi‐infinite volume of air. The Stefan correction for mass flow was modified to allow for initial gas concentrations < 100 per cent, conferring four advantages: errors in the total flow rate are relatively unimportant; density gradients are small so that convection is inhibited; the gas analysis is more sensitive; and diffusion coefficients are measured at the small concentrations that are encountered in soils. Measured diffusion coefficients (cm2 s−1 at NTP) in air for carbon dioxide (0.139), nitrous oxide (0.143), ethylene (0.137) and ethane (0.128) are compared with measured and calculated values from other sources.
Ionic strength of soil solution and its effect on charge properties of some New Zealand soils
Authors: BLACK A. S. , CAMPBELL A. S. 
Published: July 2006

SummarySelected horizons from six New Zealand soils under permanent natural vegetation, four of which form a development sequence, were chosen to provide variations in organic matter, phyllosilicate clay mineral and short‐range ordered aluminosilicate (allophane) contents. The ionic strength of the soil solution (μ) extracted from the soils of the development sequence was low, being always less than 0.005. For all horizons of the six soils, the negative charge changes linearly with μ1/2 within the ionic strength range of 0.001 to 1. The change was negligible for the least weathered and leached soil, indicating that it contained mainly permanently charged colloids. As soil development increased and/or the components carrying variable charge increased in amount, the change in charge with ionic strength increased. A regression equation showed a strong relationship between change in negative charge with ionic strength and organic carbon and oxalate‐extractable A1 (R2=0.976). This equation was tested by predicting observed changes in charge with ionic strength for a second selection of soils. The change in positive charge with ionic strength was correlated with oxalate‐extractable A1 (r2=0.914). The results are discussed in relation to measurement of soil charge and iron movement in soils.
Potential role of soil density and clay mineralogy in assessing the suitability of soils for mole drainage
Authors: SPOOR G. , LEEDS‐HARRISON P. B. , GODWIN R. J. 
Published: July 2006

SummaryThe failure mechanisms causing mole channel deterioration or collapse, which are controlled mainly by the shear, swell/shrink and apparent viscosity properties of soils, are shown to be sensitive to the influence of soil density and clay mineralogy. These two properties have, therefore, a clear potential role in helping to assess the suitability of soils for mole drainage and in helping to define the particular failure mechanisms which are most likely to be active in given situations.
Chemical pools of cadmium, nickel and zinc in polluted soils and some preliminary indications of their availability to plants
Authors: SOON Y. K. , BATES T. E. 
Published: July 2006

SummaryThis study was conducted to determine the chemical distribution and plant availability of Cd, Zn and Ni in eight metal‐polluted soils in southern Ontario, Canada. There were altogether 30 different soil samples because two of the soils had received various sewage sludge treatments. The soils were sequentially extracted with 1 m ammonium acetate to remove soluble plus exchangeable metals, with 0.125 m Cu(II) acetate to remove complexed metals, and with 1 m HNO3 to dissolve chemisorbed or occluded metals and precipitates such as oxides and carbonates. Expressed as a percentage of the metal soextracted, exchangeable Cd and Zn and Ni; complexed Cd and Zn>Ni and Ni>Zn>Cd in the acid‐soluble pool. With a few exceptions (soils with high organic matter content or low pH) at least 50 per cent of the extracted metal was in the acid‐soluble pool. The percentage of metal complexed was significantly correlated with organic matter content. The percentage of metal in the acid‐soluble fraction was significantly correlated with soil pH. Preliminary findings based on the results with two soils suggested that for Cd and Zn plant availability was correlated with the concentrations of exchangeable, complexed or acid‐soluble pools of Cd and Zn.
High gradient magnetic separation of some soil clays from Nigeria, Brazil and Colombia.
Authors: HUGHES J. C. 
Published: July 2006

SummaryHigh gradient magnetic separation was used to fractionate the clay from some tropical soils. Acid‐oxalate‐extractable iron (Feox) and aluminium (Alox) and total carbon were measured in the whole clay, the magnetic fraction and the tailings. The magnetic separation resulted in a wider range of concentrations of these elements than in the whole clays. In each of the clays Feox was greater in the magnetic fraction than in the tailings; Alox was more variable. Carbon was also concentrated in the magnetic fraction suggesting that it is associated more with Feox than Alox. The relationships between Feox, Alox and carbon depend on soil classification and soil age.
A new system for soil studies
Authors: BUTLER BRUCE E. 
Published: July 2006

SummaryA new system for soil studies is presented. The proposed soil unit is the soil mantle, the pedoderm, as it occurs in the landscape. The soil mantle forms on the surficial sedimentary bodies in the landscape. These often have a diverse and intermittent history which is passed on to the soil mantles. The series of events in the development of each soil mantle is recognized as a ‘K cycle’, and buried soil mantles represent earlier K cycles subscripted K1, K2, etc. From the dating of these older mantles, based on included dateable material, there is an opportunity to test the major soil hypotheses, an opportunity which is lacking in the current soil working model.
A comparison of five instruments for measuring soil strength in cultivated and uncultivated cereal seedbeds
Authors: O'SULLIVAN M. F. , BALL B. C. 
Published: July 2006

SummaryA torsional shear box, shear vane. cone penetrometer, drop‐cone penetrometer and pocket penetrometer were used to measure soil strength at several depths less than 150 mm in cultivated and uncultivated seedbeds in a loam and a sandy clay loam. From the shear box results, cohesion was higher and the angle of friction was lower in the sandy clay loam than in the loam. Angle of friction was independent of cultivation but cohesion was higher in uncultivated than in cultivated soil. Despite these differences cone resistance was similar in both soils above 70 mm depth. Vane shear strength and drop‐cone penetration, although empirical, indicated strength differences between soils and cultivations similar to those found with the torsional shear box. Vane shear strength, at 42 kPa, was about twice as high as cohesion in the sandy clay loam and, at 33 kPa, over four times as high as cohesion in the loam. These overestimates increased with increasing bulk density. The range of measurement of the pocket penetrometer was inadequate to cover the range of soil strengths encountered. The coefficient of variation within plots for cone resistance decreased from 76 per cent at 10 mm depth to about 22 per cent at 70 mm depth and below, and for vane shear strength it was 33 per cent near the soil surface. The drop‐cone penetrometer results were the most variable, reflecting the log‐normal distribution of penetrations. The cone penetrometer was the fastest method, followed by the shear vane, drop‐cone penetrometer and torsional shear box in that order.
Chemical and colloidal stability of sols in the Al2O3‐Fe2O3‐SiO2‐H2O system: their role in podzolization
Authors: FARMER V. C. , FRASER A. R. 
Published: July 2006

SummaryConcentrations of dialysable silica in equilibrium with Al2O3‐SiO2‐H2O sols at pH 4.5–5.0 confirm the formation of a poorly ordered non‐dialysable proto‐imogolite species with an Al : Si ratio near 2, close to that of imogolite. Sols with Al : Si>2 give nearly constant levels of free silica in solution in the range 2–6 μg/cm3, indicating equilibrium between proto‐imogolite and aluminium hydroxide species. These findings indicate that imogolite‐like precipitates in acid soils will buffer silica in solution to within this range during leaching episodes. Imogolite is more stable than a previous estimate suggested, and a revised value for its free energy of formation is proposed: ΔG0f(298.15) = ‐2929.7 kJ/mol.In Fe2O3‐SiO2‐H2O sols, the Fe : Si ratio of the non‐dialysable species varies smoothly from 11 to 3 as free silica in solution ranges from 4 to 35 μg/cm3. Such sols are much less colloidally stable than hydroxyaluminium silicate sols, but mixed Al2O3—Fe2O3—SiO2—H2O sols are almost as stable as iron‐free sols up to a Fe : Al ratio of 1.5. Thus migration of Al and Fe as mixed hydroxide sols can account for the almost constant ratio of Al to Fe with depth in oxalate extracts from Bs horizons of podzols.
The specific surface of soils determined by water sorption
Authors: NEWMAN A.C.D. 
Published: July 2006

SummaryThe hypothesis that the specific surface of soil can be measured by water sorption is tested with data for 62 subsoils of widely differing origins. Ethylene glycol and water sorption at p/p0=0.47 are found to be very closely related measurements and both are highly correlated with CEC. Both methods give a satisfactory measure of total specific surface for soils classed as smectitic and having a large CEC. However, the application of the multilayer theory to the sorption of water on external surfaces of clayey soils with small CEC suggests that both sorbates overestimate the specific surface of such soils. A better estimate of the errors would be obtained from isotherm measurements with water, which is more suitable for this purpose than ethylene glycol.
The variation of soil critical state parameters with water content and its relevance to the compaction of two agricultural soils
Authors: LEESON J.J. , CAMPBELL D.J. 
Published: July 2006

SummaryExamination of the previously published results of laboratory compression tests on a loam and a sandy loam has shown that as the water content and degree of saturation of a soil increase, the gradient of the virgin compression line, expressed in terms of specific volume and log of spherical pressure, increases and its intercept decreases. The water contents of the soils ranged from 5% to 30% and the degrees of saturation ranged from 10% to 40%. For both soils the gradient of the recompression line for previously compressed soils was shown to decrease with decreasing initial specific volume (increasing density) and to approach zero at a specific volume of 1.5 (dry bulk density of 1750 kg/m3). It was deduced that the position of the critical state line also varies with soil water content and that the critical state theory can be extended to unsaturated soils and therefore be of use in predicting the mechanical behaviour of agricultural soil during cultivation and compaction.
An evaluation of some fluorescent and non‐fluorescent dyes in the identification of water transmission routes in soils
Authors: SMETTEM K. R. J. , TRUDGILL S. T. 
Published: July 2006

SummaryTwo fluorescent dyes, sulpho‐rhodamine B and lissamine yellow FF, and three non‐fluorescent dyes, chlorantine fast green, sirius red and Chicago blue are compared for use in the identification of water transmission routes in structured soils. Subsequent to the flow of labelled water, a microsampling and extraction technique is employed to identify dye distribution in relation to structural features. The desirable properties of the dyes tested include stability over a wide pH range, anionic character and high molecular weight, the latter to reduce lateral diffusion from the transmission route. In these aspects they provide suitable alternatives to fluorescein and pyranine used by previous workers. The fluorescent dye lissamine yellow FF was found to be the most suitable for tracing rapidly moving water under field conditions. The transmission routes identified in field soils were associated with structural features readily recognized by routine soil survey techniques.
Use of a three‐plane model to describe charge properties of some iron oxides and soil clays
Authors: MADRID L. , DÍAZ E. , CABRERA F. , DE ARAMBARRI P. 
Published: July 2006

SummaryThe pH‐dependence of surface charge density of three iron oxides and the clay fraction of five horizons of a variable‐charge soil has been studied by adsorption of potential‐determining ions (p.d.i.) and by adsorption of electrolyte ions. The general trend of results for iron oxides can be satisfactorily explained by a model which considers a three‐plane distribution of electric potential. When the model is applied to soil clays the outcome is less satisfactory and, although their charge properties seem to be largely determined by their high content of minerals with variable charge surfaces, the presence of minerals with a permanent charge (clay minerals) should be considered when explaining the particular data, even for those horizons where clay minerals are present in low proportions.
Effect of periodate treatment of soil on carbohydrate constituents and soil aggregation
Authors: CHESHIRE M. V. , SPARLING G. P. , MUNDIE C. M. 
Published: July 2006

SummarySoil from a field under long‐term grass was treated with 0.02m sodium periodate for various periods up to 1176 h, followed by 0.1 d sodium tetraborate for 6 h. This destroyed an increasing proportion of microaggregates >45 μm and carbohydrate. After periodate treatment for 6 h about 70% of the soil sugars remained in the residue as measured by reducing sugar content and about 67% as individual sugars measured by gas‐liquid chromatography. After 48 h the reducing sugar content was about 45%. An inverse linear relationship was established between the proportion by weight of microaggregates >45 μm and residual carbohydrate. The residual carbohydrate showed an enrichment in sugars commonly found in plant materials; glucose, arabinose and xylose, suggesting that the microbial carbohydrate had been preferentially destroyed. When the concentration of the periodate was increased to 0.05 m the residue contained about 50% of the original carbohydrate after 6 h treatment, and 25% after 48 h and an additional increase of about 10% in the proportion by weight of particles in the <45 μm range.These results throw doubt on the validity of assumptions made in a number of studies about the limited extent to which soil polysaccharide is involved in aggregation.
Non‐destructive separation of discrete pedogenic features from soils
Authors: KANE P. , MOTT C. J. B. 
Published: July 2006

SummaryA general method for the non‐destructive separation of discrete pedogenic features that is suitable for use with a wide range of soil types is presented. Controlled slaking of soil peds is used to achieve separation between structurally coherent features and less organized matrix material. A slaking, stabilization and sieving sequence is repeated a number of times until the matrix material has been removed. The advantages and limitations of the method are outlined and a number of applications illustrated.
Electric charge characteristics of horizons of Ando (B) and Red‐Yellow B soils and weathered pumices
Authors: OKAMURA YUTAKA , WADA KOJI 
Published: July 2006

SummaryThe electric charge characteristics of five Ando (B) and two Red‐Yellow B horizon soils and two weathered pumices were studied by measuring the retention of NH4+ and Cl− at different pH values and NH4Cl concentrations. The magnitude of their negative charge (CEC; meq/100g) was dependent on pH and NH4Cl concentration (C; m) as represented by a regression equation: log CEC =apH +blog C +c. The values of the coefficient a (0.017 to 0.342), b (0.031 to 0.274) and c (1.41 to − 1.26) were correlated and depended on the kind of clay minerals present. A similar equation: log AEC =a’ pH +b’ log C+c’ was also found for the positive charge in the Ando soils, but there was little difference in the values of a’(−0.204 to −0.251), b’(0.181 to 0.253) and c’(2.06 to 2.46) between the soils. It was shown that the equations generally hold for soils with constant and/or variable charges and describe adsorption equilibria in which NH4+ and H+, and Cl− and OH− compete for cation‐ and anionexchange sites, respectively. The significance and utility of the coefficients is discussed.
The effect of pH on the total and free ionic concentrations of mnganese, zinc and cobalt in soil solutions
Authors: SANDERS J. R. 
Published: July 2006

SummarySamples of five soils whose pH in the field had been adjusted to between 5.0 and 7.5 were incubated with water or 0.01 m CaCl2 at 90% field capacity. Additional samples of the most acid soil were limed to various pH values immediately before incubation.Manganese, zinc and cobalt concentrations in the soil solutions, collected by displacement, decreased as the pH increased; the concentrations in calcium chloride solutions were higher than those in water solutions. The free divalent ions Mn2+, Zn2+ and Co2+ were the major metal species in solution at pH 5 but the proportion of the metals present as the free ion decreased as the pH increased.Differences in the manganese and zinc concentrations in the solutions were due not only to the pH of these solutions but also to the original pH of the soil in the field.
Kinetics and temperature relationships of mineralization and nitrification in Rothamsted soils with differing histories
Authors: ADDISCOTT T. M. 
Published: July 2006

SummaryMineralization of soil organic nitrogen measured in laboratory incubation experiments on Rothamsted soils with contrasting histories was most appropriately expressed by the simple zero‐order relationship Nt=kt in which Nt is the amount of N mineralized in time t. The rate constants (k) were well related to the absolute temperature by the Arrhenius equation. The approach in which ‘potentially mineralizable N’ (N0) is mineralized with first‐order kinetics could not be applied to these data.When the soils were incubated with added ammonium chloride, the increase in nitrate‐N and the decline in ammonium‐N were both linear with time, but were equal to each other in only one of the soils. These linear relationships did not reflect true zero‐order kinetics because the rates of ammonium‐N decline and nitrate‐N production both depended on the initial ammonium concentration. The Arrhenius relationships showed no significant difference between mineralization and nitrification in their sensitivity to temperature.
Variation in yield between two similar sandy loam soils. II. Causes of yield variation in cabbage and lettuce crops
Authors: COSTIGAN P. A. , McBURNEY T. 
Published: July 2006

SummaryThree experiments were conducted to discover the causes of difference in yields of cabbage and lettuce when grown on two similar sandy loam soils.In a glasshouse experiment the growth of lettuce was the same on both soils provided the soil was moist and had sufficient thoroughly incorporated fertilizer. Sowing the seeds of cabbage in small pockets of compost in the seedbed increased growth on both sites by about 25%. Placement of a large amount of extra fertilizer about 10cm below the drill line imporved growth on the poor site only.A third experiment followed the development of the yield difference in a lettuce crop. An 86% difference in potassium concentration was recorded even before emergence. This was followed by a reduction in lateral root growth on the poor site and subsequently by a lower relative growth rate from emergence until about 40 days from sowing.In conclusion, the growth on the poor site was limited because the amount of native soil potassium was madequate for the needs of the developing seedlings and the fertilizer granules could supply potassium to only a small proportion of seedlings.
Gas diffusion through soil crumbs: the effects of compaction and wetting
Authors: CURRIE J. A. 
Published: July 2006

SUMMARYSamples of 1–2 mm crumbs from a clay loam under permanent pasture were equilibrated at ‐5 kPa water potential then compacted to varying degrees. Gas diffusion coefficients D, (hydrogen through air), were measured immediately on compaction, again after re‐equilibration at ‐5 kPa, then at other water contents between saturation and dryness. The relationship between diffusion coefficient and air content, was, as elsewhere, in two parts (dD/d small for drainage of pores within crumbs; large for pores between crumbs), but the transition from one part to the other occurred at smaller air contents with increased compaction. The air content at which D approached zero as the samples wetted was greatest in the loosest soil. Compaction from a bulk density of 0.86–1.29 g cm−3 decreased the relative diffusion coefficient, D/D0 (D0 is the diffusion coefficient without impedance), from 0.35 to 0.22 (by 38%) at complete dryness, but from 0.19 to 0.035 (by 82%) in the soil initially at ‐5 kPa. On re‐wetting and re‐equilibrating at −5 kPa, D/D0 decreased further to 0.008 (total 97%) because of extra water held in the now smaller pores of the compacted soil.No single relationship between D/D0 and fitted the results for even this one soil.
Estimation of the total gaseous nitrogen losses from clay soils under laboratory and field conditions
Authors: COLBOURN P. , IQBAL M. M. , HARPER I. W. 
Published: July 2006

SUMMARYAcetylene blockage was evaluated as a method for measuring losses of N2O + N2 from two Denchworth series clay soils. The denitrification potential in anaerobic, dark incubations at 20°C with nitrate (equivalent to 100 kg N ha−1 0–20 cm depth), maximum water holding capacity, and acetylene (1%), was equivalent to 32 ± 11 and 39 ± 6 kg N ha−1 per day for the two 0–20 cm soils and was positively correlated with carbon content (r= 0.98). After 4 days N2O was reduced to N2 in the presence of C2H2.In April 1980 following irrigation (24 mm) and applications of ammonium nitrate (70 kg N ha−1) and acetylene, the mean nitrous oxide flux from soil under permanent grass was 0.05 ± 0.01 kg N2O‐N ha−1 per day for 8 days.In June 1980, the losses of nitrogen from cultivated soils under winter wheat after irrigation (36 mm) and acetylene treatment were 0.006 ± 0.002 and 0.04–0.07 ± 0.01 kg N ha−1 per day respectively before and after fertilizer application (70 kg N ha−1). The nitrous oxide flux in the presence of acetylene decreased briefly, indicating that nitrification was rate determining in drying soil.
Use of alkaline soil extracts for 13C n.m.r. characterization of humic substances
Authors: NEWMAN R. H. , TATE K. R. 
Published: July 2006

SUMMARYPrevious solution 13C n.m.r. studies of soil organic matter have been confined to isolated humic or fulvic acid fractions. A study of 10 crude alkaline extracts from five New Zealand topsoils has now shown that such purification is unnecessary. Spectra were not noticeably broadened by co‐extracted iron in concentrations up to 2 mg cm−3. Optimized pulse parameters were similar to those reported for a solution of a purified humic acid. Relaxation results support a generalized model for humic material, in which aromatic structures, carbohydrates, amino acids and polymethylene chains are linked together to form flexible macromolecules. Relative contributions from each component varied from soil to soil.