摘要:

SummarySoil water studies involve physical quantities, units and symbols, and these are discussed in terms of the International System of Units (SI) and the soil physics terminology (1976) of the International Society of Soil Science.The author particularly examines(i)the relation of SI units to the familiar but superseded cgs units;(ii)the effect of the frame of reference on the expression of water potential and hydraulic conductivity;(iii)the different interpretation of hydraulic conductivity in soil physics and in biophysics; and(iv)methods of avoiding ambiguity in presenting data.

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1979.tb00960.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

SummaryHomoionic clay suspensions were equilibrated at 25°C with aqueous NH, (0.01 to 0.30 M) by agitating for several days. Using clays extracted from three different soils, sorption of NH3, measured by titration, followed the order Na>Ca>NH4‐clay. The difference in NH3sorption between Na‐clay and NH4‐clay was matched by an increase in Na+ion concentration in the aqueous phase of suspensions of Na‐clay treated with NH3, but there was no such effect with Ca‐clay.Sorption of NH3on NH4‐clay in aqueous suspension is considered due to proton donation at sites of pH‐dependent charge, and the additional sorption on Na‐clay to displacement of Na+by NH4+ions. The additional sorption on Ca‐clay seems largely due to co‐ordination of Ca2+ions with molecular NH. Exchangeable cations affect NH3sorption differently when an aqueous phase is present than when dried homoionic materials are

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1979.tb00961.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

SummaryMeasurements of the apparent self‐diffusion coefficients of, poly(vinyl pyrrolidone) mol. wt. 40 000, polyethylene glycol) mol. wt. 4000, and chloride ion, were used to determine the effect of molecular size on diffusion characteristics in soil. The measurements were carried out on the same soil, at a range of moisture contents, and indicated that the mobility of large molecules in soils depends, to a large degree, on the inter‐aggregate pores. Any drop in moisture content which caused these pores to drain, produced a sharp decrease in the apparent self‐diffusion coefficient of the poly(viny) pyrrolidone) 40 000. Neither poly(ethylene glycol) 4000 nor chloride, which exhibited similar diffusion characteristics, were as sensitive to variation in moisture content. The results are interpreted in terms of certain parts of the pore volume being inaccessible to the diffusing molecule. Possible reasons are out

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1979.tb00962.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

SummaryThe concentration gradient of soil acid neutralised when a block of moist soil was placed in contact with a source of HCO3‐ was predicted from an equation for diffusion of HCO3‐, and its simultaneous reaction with the soil. The reaction was defined by empirical rate constants describing the changes of pH with time in a soil: M/100 CaCl2+ KHCO3solution, suspension system. Values of these constants, determined independently, were too large resulting in prediction of steeper and leas extensive concentration profiles of soil acid neutralised than measured in the diffusion system. The true pH of the soil pore solution in the block would have been considerably greater than a predicted ‘equilibrium’ pH. The consequences for rhizosphere processes are di

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1979.tb00963.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

SummaryThe effects of cations on desorption of phosphate previously added to soil were studied by mixing phosphated soil with solutions of chloride salts at a range of solutionitoil ratios and for periods which ranged from 1 to 96 h. Phosphate desorbed was then related to the experimental variables by a pair of simultaneous equations. In calcium chloride, the rate of desorption of phosphate was inversely proportional to the calcium concentration. Desorption was faster in 0.01 M magnesium chloride than in 0:01 M calcium chloride, and faster in 0.03 M sodium chloride than in either magnesium or calcium chloride. Addition of a further supply of the cation on an exchange resin increased the rate for both sodium and magnesium but decreased it for calcium. A range of monovalent cations formed a sequence from fastest to slowest of: Li+>Na+>NH4−>K+, Rb+>Cs+. The identity and concentration of the cations had a large effect on the concentration of phosphate when the solution: soil ratio was small. There were also large effects in the amount of phosphate desorbed when the solution: soil ratio was large and the concentration of phosphate approached zero. This suggested that the escaping tendency of the phosphate was decreased when the cations which balanced the negative charge on the adsorbed phosphate were close to the surfac

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1979.tb00964.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

SummaryThe effects were measured of varying the solution: soil ratio, and the vigour of shaking on the rate of adsorption of phosphate. One soil appeared to break down with vigorous shaking, prior to adding phosphate, especially at low solution: soil ratio. As a result, subsequent phosphate adsorption was faster. With gentle shaking, there was no effect of solution: soil ratio with the soil. Another soil was more stable and there were only small differences due to vigour of shaking and no effect of solution: soil ratio with any method of shaking.The change in phosphate concentration was not proportional to the reciprocal of time as reported by Ryden and Syers (1975) and Hope and Syers (1976). Hence the validity of extrapolating from short sections of reciprocal‐time graphs in order to estimate equilibrium is questione

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1979.tb00965.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

SummaryA study of the A horizons of cultivated soils from Saskatchewan, Canada showed that the organic carbon contents were in the sequence semi‐arid Dark Brown soils (1.7 per cent),

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1979.tb00966.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

SummaryMössbauer specttoscopy has been used to provide information on the effect of pH on the nature of the complexes formed between iron and humic acid. At an initial suspension pH greater than 3 the iron occurs in the ferric form, although it is difficult to assess to what extent it is in combination with organic matter. On lowering the pH, iron is reduced with a considerable proportion of the ferrous iron entering solution, partly as a solvated ion and partly as complex forms. Raising the pH leads to re‐oxidation and the precipitation of a considerable proportion of the iron in an inorganic form with Mossbauer parameters similar to those of β‐FeOOH. No evidence was obtained for Fe(III) in solution or for Fe(II) in any form at pH values greater t

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1979.tb00967.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

SummarySimple, rapid and non‐destructive measurements of magnetic properties (magnetic susceptibility, saturation isothermal remanent magnetization and coercivity of isothermal remanence) coupled with more time consuming and sophisticated analyses such as thermomagnetic and Mössbauer effect studies, provide a basis for identifying forms of iron oxide present in the soil.At two of the sites studied, Caldy Hill, Merseyside, and Llyn Bychan, N. Wales, the secondary ferrimagnetic oxide formed in surface soil as a result of recent forest fires is shown to be non‐stoichiometric magnetite approximating to the formula Fe2.904. No evidence for the presence of maghemite was found in any of the soil samples from these sites or in soils from the Annecy region of S.E. Fr

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1979.tb00968.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

SummaryThe value of modem commercial DTA equipment in the identification and determination of anhydrous carbonate minerals can be greatly improved by incorporating a controlled‐atmosphere (carbon dioxide) technique. The unproved peak definition and increased height enables the detection of carbonate minerals at concentrations of the order of 0.25 per cent by weight in a 50 mg sample. Further, the related changes in temperature of the decomposition reaction peaks provide additional information for the identification of carbonate mineral reactions. The method has particular application in mineralogical and pedological investigation

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1979.tb00969.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY