摘要:

SummaryShallow friable red soils (euchrozems) and shallow cracking clays (black earths) occur in close proximity on basalt hills of the Darling Downs of Queensland. The euchrozems are mainly restricted to fiat hill crests and are associated with lithosols; the shallow black earths occur on upper pediment slopes, on small convex crests and on depressions on flat crests. The euchrozems are moderately leached and contain kaolin minerals and hematite with minor montmorillonite, while the black earths are dominantly montmorillonite with minor kaolin and hematite. It is proposed that the euchrozems have developed by long continued weathering under stable well‐drained conditions while the black earths have formed in sites prone to erosion and in situations with less water available for weathering. The weathering products produced in each situation have ensured continuation of the processes. The presence of two red soils in anomalous positions have been ascribed to (a) soil formation on exposed ‘bole’ (compacted red clay) layers and (b) local peculiarities of parent material controlling the course of weath

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1974.tb01123.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SummaryFractionation of the phosphates in a sodium hydroxide extract of an arable soil has shown the presence of a number of esters of a type not previously detected in soils. These included several mono‐phosphorylated carboxylic acids with C to P ratios of approximately 7 or 8 to I and two esters each containing glycerol,myoinositol, chiroinositoland an unidentified component. Another ester, probably containing two phosphate groups, was also detected but was not completely separated from other compounds containing no P. These esters constituted only approximately 3 per cent of the total soil organic P but considerable losses of organic P occurred during the extraction and isolation procedures. The amounts of the inositol phosphates, nucleoside phosphates, and inorganic pyrophosphate in the extract were also measure

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1974.tb01124.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SummarySoil texture is usually assessed by either the manipulation of the field soil in the hand or by a particle size analysis of the dispersed soil. These two methods are often regarded uncritically as alternatives, and this paper stresses the point of view that the hand manipulation method is the preferred one, because the particle size analysis method depends on the establishment of relevant correlations. However, the subjective nature of the first method is admitted, and the paper describes an attempt to devise an objective test based on the elements of the hand assessment. From the observation that one senses the reaction of the soil to compressive and shearing forces during an assessment by hand it is suggested that some measure of soil strength might be used as an index of texture.The strength of twenty‐three soils was measured over a range of water contents using the fall‐cone penetrometer. The curves representing the relationship between the strengths and the water contents were all of a similar shape and tended to form a regular array, with the lighter soils at the low water content end of the scale and the heavier soils at the higher end. They showed that the strength of a given soil was very sensitive to water content.It was concluded that the separation of the soils into the broad textural classes was made mainly from measurements of the strengths of the wetted soils, but that the more detailed descriptions, including for example, specification of the grade of the sand, required in addition an estimation of the sizes of the particles obtained by feeling them between the fingers. As a corollary, these finer divisions are not related to soil strength, and thus are dubious indications of heaviness or lightn

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1974.tb01125.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SummaryThe plasticity limits of seventeen agricultural soil standards representing contrasting textures, were measured both by the standard methods and by the fall‐cone penetrometer method (Towner, 1973). The results are compared with the Casagrande A‐line in the plasticity chart. The plasticity limits obtained by the fall‐cone method are given for twelve other soils. The plasticity indices for the soils tended to lie about a single curve. They lay above the Casagrande A‐line at low values of liquid limit. There was some suggestion of an order according to texture along thi

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1974.tb01126.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SummaryNubian sandstone exposures in sub‐humid, semi‐arid, and arid environments have given rise to red, sandy but in other respects very different soils. Soils have a fairly well developed profile only in the sub‐humid zone, including a textural B horizon and are free of soluble salts and carbonates. In the semi‐arid and arid zones, profile differentiation is weak or non‐existent. Soils are shallow and contain carbonates, and in the arid zone also soluble salts, including gypsum. Kaolinite is the only clay mineral which is common to all the nubian sandstone parent materials. It is the major clay mineral in the sub‐humid zone soil. In the semi‐arid soils smectite is a second major clay component. In the arid zone both smectite and palygorskite, in minor amounts, accompany kaolinite. Both smectite and palygorskite are probably pedogenic neoformation products. Material of aeolian origin has probably been introduced into the silt and fine sand fractions of both the semi‐arid and arid soils. Some contamination of the clay fractions may hav

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1974.tb01127.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SummaryMeasurements of pH and A1 concentration were made on 10‐2M CaCl2, suspensions of a number of acid soils that had been limed to give 3 range of pH values, and exchangeable A1 and Ca+Mg were determined in 1.0 M NH4Cl extracts. The variation of pH with A1 concentration did not support the theory that pH is controlled by the solubility of Al(OH)3. For some of the soils, proton release on hydrolysis of A13+ions in solution accounted for the pH values, and explained quantitatively the variation of pH with the Ca:Al balance of the exchange complex, taking account of the selectivity coefficient for exchange, Kca→A1Although Kca→A1was smaller for soils containing more humus, their pH values were also less than those predicted by the hydrolysis of A13+in solution, indicating that they contained other sources of protons, presumably the carboxyl groups in

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1974.tb01128.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SummaryThe best reagent for displacing adsorbed NH, for the measurement of cation exchange capacity of soils is a mixed ZN nitrate solution of potassium and calcium. The equivalent ratio of K to Ca should be in the range from 1 to 3. This mixture is better than simple solutions of Li, Na, K, Mg, Ca, Sr, and Ba nitrates and mixtures of KNO3with any one or two of these other nitrates.

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1974.tb01129.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SummaryHumic substances stimulate the amount of sulphate actively transported by excised barley roots to an extent depending on the humification pattern of the original soil organic matter. Humic fractions separated on Sephadex differ in their effects on the active transportation of sulphate by roots; both the carboxyl‐to‐phenolic OH ratio and the molecular weight strongly affect the biological activity of the fractions. In contrast, the procedure used to extract the humic material (sodium hydroxide or sodium pyrophosphate) has little influence. When the humic material is complexed with montmorillonite, sulphate uptake is further enhan

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1974.tb01130.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SummaryThe rate of ion exchange of humic substances (humic acid and peat in the hydrogen form) with lead ions was investigated. As in processes occurring in nature, the lead solution was added in all our experiments slowly and continuously at a constant feed rate to the well‐stirred water‐suspended humic substances. Control experiments were also performed with a well‐defined synthetic ion‐ exchange resin (carboxylic acid type). The uptake of divalent lead ions by the humic substance and by the ion‐exchange resin, which is coupled with the release of an equivalent amount of hydrogen ions, proceeds as a function of time according to a characteristic sigmoidal curve. During the initial phase, the rate of ion exchange increases continuously with time, even though the humic substances become more saturated with lead ions.Theoretical calculations, based on a film diffusion process as the rate‐determining step, show that this behaviour should indeed be observed if any solution, containing exchangeable counter ions, is added continuously to an ion exchanger suspended in a solvent.The theory predicts further, in agreement with the experimental results, that in the initial phase of the ion‐exchange reaction, the uptake of the counter ions is proportional to the square of the time. If experiments are performed with different rates of addition of the counter ions, the time required to exchange a certain amount of counter ions should be proportional to α‐1/2, where α is the rate at which the ions are added. This prediction is also in accordance with the exp

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1974.tb01131.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SummaryThe surface properties of soil carbonate were related to its distribution in thirteen profiles of a catenary sequence of calcareous soils from Azerbaijan.When carbonate surfaces were contaminated by Mg2+,45Ca was used as a tracer for Mg2+as well as Ca2+, thus enabling the carbonate surface areas to be estimated. These were shown to be inversely and curvilinearly related to soil carbonate contents, but with some abnormality for the three extremely saline/alkaline soils. Na+ does not appear to be specifically adsorbed on carbonate surfaces in the latter.The specific and the total surface areas of carbonate in the surface soils are very sensitive indices of profile development, and are combined with the content and particle‐size distribution of carbonate in the profiles to show the variation in soil development along the catenary sequenc

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1974.tb01132.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY