摘要:

SummaryThe micropore (<100 Å) size distributions of compacted clay mineral systems have been examined by means of low‐temperature N2sorption isotherms to saturation. The calculation of pore sizes was based on the application of the Kelvin equation, corrected for the adsorbed film thickness, to the parallel plate model.Clay‐mineral systems have been shown to exist with a high degree of parallel alignment of the plate‐shaped crystals. This results in a high proportion of microporosity and in relatively discrete pore sizes.In montmorillonite clays much intercrystalline overlap area in the dry matrix is inaccessible to N2sorption. The structure of these systems may be governed partly by the effect, in suspension, of electrostatic interaction between the charged particles on crystal size, but largely by mechanical interaction on sedimentation and the size of the exchangeable cations p

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1967.tb01481.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

SummaryThe area in the Rift Valley, Kenya, within which soils are deficient in Cu for wheat crops has been delineated. Deficiency is associated with soils, derived from pumice and ash from the Menengai caldera, which contain less than 3 ppm Cu by analysis withAspergillus niger(M). In pot tests the yields of tomato as indicator crop for Cu deficiency were found to correlate closely with yields of wheat.Copper sulphate and copper oxychloride when broadcast were both effective in eliminating the deficiency in wheat and resulted in a marked increase in Cu content of the grain. Spraying with either compound, or applying oxychloride as a seed dressing, significantly increased the grain yields but did not result in maximum yield.

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1967.tb01482.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

SummaryIn valley and blanket‐bog peat, oxygen‐diffusion rates and corresponding oxidation‐reduction potentials have been measured, and the relationship between them expressed graphically.Oxygen‐diffusion rates were obtained ‘polarographically’, and the Pt cathode also served as the redox indicator‐electrode.Plateau‐shifts towards more positive potentials made it necessary to use the reduced voltage setting of −0.48 v for oxygen determinations. These plateaushifts correlate with a lowering of the oxygen content, and an increase in acidity, or, perhaps, with the type of buffer systems found in peat.The ratio redox potential/oxygen diffusion is not constant. At very low oxygen values there is a relatively large increase in redox potential per unit of oxygen, but, as oxygen approaches 2 × 10−8g O2cm−2min−1, the ratio becomes much lower, while variations become more obvious.rH values calculated according to Jeffery (1961), show that, in peat of high iron content at pH 6, the first traces of oxygen correspond to an rH 1.10–1.20 (E6, 50–120; reduced and oxidized iron probably present), while above 2 × 10−8g O2cm−2min−1the rH is greater than 1.20 and oxidized iron probably predominates. Thus oxidized soil, as defined by Jeffery, may be maintained at very low oxygen levels.It is suggested that oxygen diffusing from plant roots into these peats will oxidize reduced soil prod

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1967.tb01483.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

SummaryThe double layer theory was used for estimating the relative amounts of positively adsorbed cations when a mixture of three salts with mono‐, di‐, and trivalent cations is present in clay electrolyte systems. It is shown that the adsorbed cations are dominated by the trivalent cation when the salts are present at equal concentrati

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1967.tb01484.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

SummaryAccurate control of rate of flow of solution through soil columns is important in laboratory studies of leaching, but is difficult to achieve because of fluctuations in permeability. A simple and inexpensive method of automatically maintaining a constant flow‐rate through several columns simultaneously is described. The apparatus comprises (i) a rotating delivery system which distributes the leaching solution equally to eight compartments, (ii) a system for automatically regulating the flow through each column to keep pace with the solution delivered, and (iii) an automatic fraction‐collector to collect the effluent from the columns. Using this apparatus the standard deviation of the volumes delivered to the eight individual columns was less than 2 per cent of the mean, provided the flow rate was faster than 10 m

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1967.tb01485.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

SummaryThe permeability of glacial till soils having mainly montmorillonite in the clay fraction was negligible when the exchangeable sodium percentage (ESP) exceeded 15 to 20. Relatively higher permeability values were obtained in soils containing gypsum, but water transmission through such soils was negligible above ESP of 30 to 35. The relative decrease in permeability with increase in exchangeable sodium depends not only on the ESP and electrolyte concentration in the soil solution but is affected by the types of clay minerals.

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1967.tb01486.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

SummaryDispersion of soil particles is achieved without use of oxidants, acids, or peptizing reagents, by subjecting an aqueous suspension of the soil sample (10 g soil, 25 ml water) to sonic vibration at 13 to 15°C using a Raytheon (9 kc, 50 w) vibrator. Studies using soils of widely different textures and organic matter contents showed that the dispersion caused by sonic vibration for 30 min, as evaluated by pipette analysis for<2 μ material, was similar to that obtained by chemical methods currently used for dispersion of soils. The dispersion effected by ultrasonic vibration of soil‐water suspensions using a probe‐type vibrator (18–20 kc, 60 w) is comparable to that achieved by sonic vibration. The vibration method of dispersing soil particles yields stable suspensions and is effective with highly calcareous soils and with soils containing large amounts of montmorillonite and organic matter. It permits dispersion of soil particles without dissolution of more than trace amounts of organic or inorganic material and does not significantly affect the pH or conductivity of the soil sus

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1967.tb01487.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

SummaryStudies of the dispersion of compound soil particles by sonic vibration and cation‐exchange resin techniques indicate that the difficultly dispersible particles in mineral soils of high base status are microaggregates (<250μ diam) consisting largely of clay and humified organic material linked by polyvalent metals. The inter‐particle bonds in these microaggregates can be disrupted by application of mechanical energy (sonic vibration or prolonged shaking with water), the amount of energy required for dispersion of clay‐size mineral material being reduced by treatments that weaken or destroy these bonds (e.g. treatments leading to replacement of polyvalent metals by monovalent metals or to destruction of organic matter). A theory is proposed depicting microaggregate formation as a solid‐phase reaction involving linkage of electrically neutral clay mineral and organic matter particles by polyvalent metals on exchange sites, and microaggregate disruption by sonic vibration as a reversal of this reaction. Experiments to evaluate this theory are d

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1967.tb01488.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

SummaryA study has been made of the colonization by soil fungi of kaolin pellets in which was incorporated either a lignin preparation extracted fromPhragmitesor the lignin‐related substances, vanillic acid or α‐conidendrol. Fungi isolated from the lignin pellets by the dilution method were grown in liquid culture containing thePhragmiteslignin. Subsequent analysis by UV absorption spectrometry indicated up to 40 per cent loss of this material. IR analysis of the residual lignin showed that it was little altered.Fungi from the pellets containing vanillic acid and α‐conidendrol were isolated by direct transfer of spores and mycelium from the pellets to agar plates. The range of soil fungi already known to metabolize vanillic acid in pure culture was extended by this method and includedStilbumspp.,Humicolasp., and two unidentified species. Dry‐weight determinations of mycelia combined with UV absorption spectrometry and paper chromatography of culture filtrates indicated that, with the exception ofAcremoniellasp., all isolates metabolized vanillic acid when it was supplied as sole C source. Growth‐promoting substances present in yeast extract were required byVolutellaspp. before the vanillic acid was metabolized.The pellet technique offers many possibilities for studying the microbiological degradation of soil substances and in addition enables the soil micro‐habitats to be explored in greater detail than has previously

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1967.tb01489.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

SummaryClay‐with‐flints rests on remnants of the exhumed sub‐Eocene surface, which is shown to be an important geomorphological feature of the West Sussex Downs. Mineralogical and other soil profile studies indicate that the deposit has developed by the action of cryoturbation and soil‐forming processes on a thin cover of Reading Beds clay left on the sub‐Eocene surface during the southward recession of a small Eocene escarpment. Two horizons corresponding to Clay‐with‐flintssensu strictoof Loveday (1962) are recognized. The basal horizon is composed partly of insoluble Chalk residue, but mainly of clay moved down from overlying horizons into the spaces left on dissolution of the Chalk at the junction of the Chalk with the base of the Clay‐with‐flints. The upper horizon is composed of material from weathered remnants of Reading Beds clay, thoroughly mixed by cryoturbation with flints, other insoluble Chalk residue and clay from former basal horizons. The surface horizons of the soils often include a

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1967.tb01490.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY