摘要:

SummaryThe time taken for a tensiometer to reach equilibrium with the soil‐water pressure is a function not only of the tensiometer characteristics but also of the soil‐water transport properties. When. in an appropriate system of units. the numerical value of the conductance of the tensiometer cup is small compared with that of the hydraulic conductivity of the soil, and the sensitivity of the pressure ‘gauge’ is large compared with the differential water capacity of the soil. then the precision of the measurements is such that the observed response may be indistinguishable from that of a tensiometer in bulk water. referred to as ‘tensiometer limited’.The theory developed in this paper for a hemispherical tensiometer cup shows that tensiometer‐limited conditions can be achieved in practice. Moreover. such conditions would often correspond to a rapid response system. It is suggested that it might be advantageous in the design of a field recording system to choose a tensiometer‐limited system even if it is not the fastest realisable one in order that its response is completely predictable from the known tensiometer characteristics. independent of the unknown soil properties. which

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1980.tb02108.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SummaryThe structure of a humic acid from a New Zealand pasture topsoil has been investigated by conventional solution13C n.m.r. spectroscopy and by the cross polarisation technique. Relaxation results showed that a pulse spacing of about 0.2 s was optimum for n.m.r. of the humic acid dissolved in 0.5 M aqueous NaOH. Aromatic rings accounted for 26 per cent of the total carbon. Cross polarisation n.m.r. is a viable method for obtaining13C spectra of solid humic acids, although aromaticity cannot be estimated as accurately as for coals.

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1980.tb02109.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SummarySamples of humified organic matter were extracted from several sources by water or alkali, and divided into colloidal and dialysable fractions. The variation of the concentration of complexed copper with that of added copper was determined for these fractions using a cupric ion‐sensitive electrode. A computer program fitted five equations often used to describe adsorption of ions on soil surfaces to the results. The data did not fit Langmuir or Temkin equations very well, probably because of the heterogeneity of adsorption sites of the organic matter; they fitted double Langmuir, Gunary and Freundlich equations almost equally well, leaving very small residual sums of squares. The Freundlich isotherm is preferred as it has only two parameters and the values of these are fairly stable to changes in the range of copper concentrations considered, or to doubling of the complexant concentratio

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1980.tb02110.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SummaryThe concentration of iron(II), manganese(II), ethylene, volatile fatty acids (VFAs) and hydrogen sulphid have been determined in peaty forest soils subject to waterlogging. Although VFAs would merit further investigation, iron(II) seems to be the only toxin likely to accumulate in sufficiently large quantities to cause root damage.The use of the ion selective electrode for sulphide measurements is criticized.

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1980.tb02111.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SummaryThe effect of infection by vesicular‐arbuscular mycorrhiza on the predictive value of soil analysis for available P was tested in a glasshouse experiment. Leeks (Allium porrum) were grown on ten Rothamsted soils with a wide range of initial NaHCO3‐soluble P, each of which also received 5 levels of added P. Soils were partially sterilized with 1 Mrad of γ‐radiation, or left untreated; plants on sterilized soil were infected with yellow‐vacuolate endophyte (Glomus mosseae) or left non‐mycorrhizal. The NaHCO3‐soluble P in the soils was measured 5 days after phosphate addition.Yields from all P levels on all soils were plotted against soil NaHCO3‐soluble P content and separate smooth response curves were obtained for non‐infected and artificially‐infected plants. Infection increased yield only on soils with less than 100 mg P kg−1. In contrast, naturally‐infected plants gave no clearly defined response curve to P, and on three soils the yields were consistently low. These soils gave very low natural infections and had low spore densities probably due to the cropping history of the sites.Artificially‐infected plants had much higher shoot P concentrations than did uninfected plants of similar dry weight, over a large range of soil phosphate levels; this effect was also noted with the endophyteG. fasciculatus. Naturally‐infected plants showed a poor relationship between shoot

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1980.tb02112.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SummaryExamination by infrared spectroscopy and electron microscopy of the fine clays (<0.5 μm) dispersed at pH 3.5 from H2O2‐treated soil indicates that imogolite and proto‐imogolite allophanes are concentrated in podzolic B2and B3horizons, and make up at least 6 percent of one B2horizon soil, which contains virtually no layer silicate clays. It is argued here that imogolite‐type components are the principal source of extractable aluminium and silicon in such horizons, that they may act as cementing agents in indurated horizons, and that proto‐imogolite, a soluble aluminium‐silicate complex, is the predominant mobile form in which aluminium is transported to B2and lower horizons of podzols. Comparison of the amounts of aluminium extracted by acetic acid with those extracted by EDTA indicates that extractable aluminium in Bhg, Bh, and organic‐rich A2horizons is present principally in organic complexes. It is proposed that the aluminium fulvates concentrated in these horizons are f

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1980.tb02113.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SummaryCarbon dioxide evolution from soil is generally considered to be an indication of actively metabolising biomass. This paper describes a method for studying carbon dioxide evolution from intact soil cores. It also introduces the possibility of using the method in studies of biomass using fumigation techniques.

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1980.tb02114.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SummaryThe State of Bahrain lies in the arid zone on the southern side of the Arabian Gulf. The factors influencing soil formation on the Islands are examined and an account given of the soils. These can be placed in four groups: Solonchaks, Regosols, Yermosols and Fluvisols. The Solonchaks of the northern plain contain unprecedented amounts of gypsum which, in the absence of leaching, give rise to a variety of morphological features. The distribution of Regosols, Yermosols and Fluvisols can be related closely to physiographical location throughout the country.

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1980.tb02115.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1980.tb02116.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY