ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1965.tb01430.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

SummaryHumic acids from seven different cultivated irrigated soils of the semi‐arid and arid regions were extracted with N/2 NaOH and were analysed for their elementary composition and cation exchange capacity. The methoxyl contents of the cids were determined before and after methylation. There were marked differences in the carbon and nitrogen and in the ash constituents of the acids obtained from different soils. The humic fractions obtained from three darkgrey soil types had higher carbon and lower methoxyl contents than the others. The nitrogen contents of the fractions from three of the soils were comparatively high, being about 8 per cent. These results show that the humic acids of the darkgrey soils are of a more condensed nature than the others. The hydrogen content varied only a little and was less characteristic of the fractions. The high ash contents of all the humic acids is interesting, the figures ranging from 5.8 to 10.6 per cent. Of the ash 31.7 to 39.5 per cent occurs as silica, 19.7 to 24.6 per cent as alumina, 17.5 to 29.0 per cent as iron oxide, 8.3 to 14.5 per cent as phosphorus pentoxide, and 0.54 to 1.88 as the oxides of calcium and magnesium together. The presence of silica is possibly the result, partly at least, of its dissolution during alkali extraction of the soils so that it is held up by humic‐acid particles on acidification of the extracts. The oxides of iron and aluminium, forming about 50 per cent of the ash, appear to be partly present chelated with the humicacid molecules. The methoxyl content varied with the soil type from 0.3 to 1.6 per cent and was increased by methylation of the humic acids by between 5.3 and 7.8 per cent. Methylated humic acids had a much smaller cation exchange capacity than the unmethylated ac

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1965.tb01431.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

SummaryThe soils of two cuestas developed on ferruginous sandstones, one of Cretaceous, and the other of Eocene/Pliocene age, were studied in relation to the slopes and planation surfaces with which they were associated. The processes involved in the retreat of hardened plinthite breakaways are shown to account for the principal morphological features of the soils, especially the lower diagnostic horizons, and thus throw light upon the mode of formation of the ‘Acid Sands’ of southern Nigeria, and the ‘terre de barre’ of the ‘Continental Terminal’ of southern Dahomey. A distinction is made betweensheet plinthitesandflanking plinthitesaccording to their mode of occurrence, both being related to periods of stillstand in the evolution of

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1965.tb01432.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

SummaryThe study is primarily concerned with the very extensiveloamy podzolsshowing imperfect drainage in the eluvial horizon (Crampton, 1963a). The preferential preservation ofPolypodiumspores and the less complete floristic sequence recorded by pollen grains in podzols on warm slopes with W. or S. aspect, and greater prominence of Ericaceae and birch in the vegetational history of podzols on cold slopes with N. or E. aspect, suggest that those soils on the colder slopes were both the wetter and more acid in the past. Gleying and the development of associated structures in the eluvial horizon probably began under Ericaceae during early medieval times, and are continuing. In the spoil tips occurring across the north crop of the Coal Measures, where undisturbed for over 100 years, these structures and gleying have developed only in cold, damp pockets associated with Ericaceae on slopes with NW., N., or E. aspect. A similar but less rigid relationship occurs in places of high relief outside the spoil tips. The essential elements of these structures may develop remarkably quickly, and can be seen on opencast sites fifteen years after restoration under pastures which have become impoverished through neglect.

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1965.tb01433.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

SummaryAn indurated horizon occurs in soils developed in a parent material of drift in Fforest Fawr and the South Wales Coalfield. The variety of soils showing induration, and the depth of induration in some, preclude any specific pedological processes as an explanation of its formation. Fitzpatrick (1956) has suggested that induration and associated structures are relict features of perma‐frosting, induration arising from compression by ice‐crystal growth. Cementation may arise through pedological processes later. Illuviation of clay has occurred in one soil where, also, sesquioxide determinations suggest there has been a little differential downward movement of iron and aluminium in the manner described by Romans (1962) for podzolized soils containing an indurated horizon. The restricted pore space of the indurated horizon has now been mostly infilled with translocated clay. Percolation of water is normally very slow through an indurated horizon, and in this profile has, presumably, been totally deflected by cementation of the indurated horizon. A morphological discontinuity between the podzol profile and indurated horizon has probably been produced by the resulting lateral flow. Where podzolization or illuviation of clay has not occurred, a plane of discontinuity is replaced by a narrow transition z

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1965.tb01434.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

SummaryIn a study of some aspects of the rate and type of decomposition of leaf litter ofAbies grandisLindley,Picea sitchensis(Bongard) Carrière, andPinus sylvestrisL., the external features of the needles at different stages of decay have been recorded, together with the micro‐fungi appearing on the needles and cultured from them. A regular sequence of colour changes was demonstrated, from the original green to grey‐green, brown, grey to black. Unless conditions were very favourable, the litter ofPicea sitchensischanged colour much more slowly than that of the other species. The proportion of collapsed leaves increased progressively with time, although in the earlier stages of decay reversion to the non‐sunken condition could occur by water uptake. A definite succession of fungi was recorded as the litter decomposed. Needles remaining affixed to the tree were commonly colonized byFusicoccum bacillare, accompanied on needles ofPinusbyLophodermium pinastri. On freshly fallen needles,Haplographium penicilloides, Aspergillus fumigatus, andPenicillium frequentansoccurred frequently, together with white hyphal ‘cushions’ in the stomatal apertures, and a sterile net‐forming surface mycelium. Older litter was colonized byTrichoderma viride, Oidiodendron fuscum, andVerticicladium trifidum. Mucor hiemalisandAposphaeriasp. were present throughout the period of decay, together with a number of less co

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1965.tb01435.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

SummaryThe soil‐sectioning technique was used to allow microscopic examination of fungal populations in relatively undisturbed samples of soil from the horizons of an iron‐humus podzol at Delamere, Cheshire. The technique was also applied to a seasonal study of the quantitative changes in the fungal populations in the A0h layer of the organic horizon and the five mineral horizons of the podzol. For these quantitative assessments, measurement of length of mycelium per unit amount of soil was the most sensitive method, being superior to measurement of density of mycelium or measurement of percentage frequency of occurrence of mycelium.Considerable evidence was obtained during the seasonal study of an increase in mycelium production during the autumn–winter period of the year, clearly demonstrated in the A0h and A1horizons. This increase in mycelium production appeared to be correlated with the period of maximum leaf fall (and with the corresponding down‐wash of nutrients into the mineral soil).An attempt was made to classify (on morphological grounds) types of mycelium observed, and to relate the morphological groups to the dominant organisms previously isolated from this soil.The data obtained from this study point to the value of microscopic examination of soil in providing essential supplementary data to those obtained from cultural

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1965.tb01436.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

SummaryHypothetical mechanisms for charge blocking on the surfaces of kaolinitic minerals are presented to account for the anomalous behaviour of ferrallitic soils on deferrification. On iron oxide removal, the following situations can arise where positive and negative charges (i) both increase, or (ii) both decrease, or (iii) increase and decrease concomitantly. These variations in charge after deferrification can adequately be explained on the basis of blocking which affects both the basal planes and edges of the clay minerals.

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1965.tb01437.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

SummarySchofield's lime and phosphate potentials were determined on four soils using CaC12solutions varying in strength from 0.002 to 0.05 M. The lime potential, pH–½pCa, was found to be independent of the CaCl2concentration. The phosphate potential, ½pCa+pH2PO4, of the neutral and alkaline soils decreased when the CaC12molarity was increased from 0.002 to 0.05. When allowance was made for the formation of a soluble calcium phosphate complex, CaHPO4, the phosphate potential became independent of the calcium chloride concentration in all four so

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1965.tb01438.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

SummaryTo estimate the diffusion coefficient of gases,Dc, within soil crumbs gaseous diffusion was measured first on a packing of dry 1–2 mm crumbs, then again after the crumb pores, but not the inter‐crumb pores, had been rendered nonconducting by saturating with an inert liquid. Using equations for analogous electrical properties of heterogeneous materials, the range of values ofDc/Dowas from 0.025 to 0.156 for eight soils with crumb porosities in the range 0.25 to 0.41. For each soil, single value parameters for soil complexity were calculated fromDc/Doand the appropriate crumb porosity, and these were in accord with known behaviour in the field: the better the structure, the smaller is the complexity parameter. The validity of the method was checked by measuring the diffusion coefficient,D, by standard methods on blocks of soil and also by the indirect method on crumbs obtained by crushing the block. Comparison of these values forDandDc, ideally the same, confirmed the adequacy of the met

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1965.tb01439.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY