摘要:

SUMMARYInterlayer materials of partially interlayered vermiculites (PIV) in 15 Dystrochrepts derived from Tertiary sediments were analysed by dissolution with hot 1/3M sodium citrate or 0.15 M oxalate‐oxalic acid in combination with XRD and IR spectroscopy. Both the citrate and oxalate treatments dissolved Al from all soil clays. The dissolution of Al by the citrate treatment paralleled the dissolution of Si and the interlayer collapse of PIV, whereas that by the oxalate treatment did not, indicating that the interlayer materials contain not only Al but Si. The materials dissolved by the citrate treatment had a molar Si/Al ratio ranging from 0.72 to 0.24 that decreased with the increasing interlayering of PIV. Differential IR spectroscopy indicated the dissolution of aluminosilicates possibly having Si‐O, Al‐OH and Si‐O‐Al bonds, but not Si‐O‐Si bonds. The extent of interlayering of PIV showed a good correlation with the amount of Al dissolved by the citrate treatment and increased with increasing soil pH (H2O) from 4.5 to 5.2 and with decreasing exchangeable Al in soil.Formation of a hydroxy‐Al sheet partially bonded with Si‐tetrahedra was suggested as a possible model of the interlayer structure of PIV. The differences between PIV in the studied Inceptisols and other so

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1988.tb01202.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

SUMMARYSoil samples from Germany, Israel and USA were moulded at water contents around the lower plastic limit and compacted with uniaxial pressuresc. 20‐200 kPa. The samples were stored at constant water content. At intervals after moulding, the strengths of sub‐samples were measured with a small penetrometer.The soils showed increases in strength with time. Two types of behaviour were observed and explained by a simplified theory for soil strength. With the German and Israel soils, penetrometer strength increased by the same absolute amount irrespective of compaction pressure. This indicates that new particle‐particle bonds were being formed at a rate which was not affected by compaction. With the USA soils, the ratio of penetrometer strength/initial strength increased with time and was independent of compaction pressure. This indicates that existing particle‐particle bonds were being reinforced by a cementation mechanism. Evidence is presented which suggests that age‐hardening by this second mechanism may be inhibited by soil organ

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1988.tb01203.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

SUMMARYDetailed observations of gley features in soils derived from grey Upper Greensand rocks have been compared with their moisture regimes as determined by water‐levels in dipwells. There was good correlation between the incidence of grey ped face and matrix colours of low chroma, prominent ochreous mottling within the matrix and duration of waterlogging. Careful examination of soil macromorphology can be used, despite inherent greyness, to assess the drainage status and Wetness Class of these soils.Physical and micromorphological analyses suggest that the wetness of some Upper Greensand soils is due to the combination of low vertical permeability in the underlying rock, and moderate horizontal permeability in the overlying horizons. Such circumstances allow perched water‐tables to form in wet weather, sustained by lateral flow when rainfall has cea

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1988.tb01204.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

SUMMARYLaboratory investigations of the dissolution of North Carolina phosphate rock (PR) in soil, as affected by soil texture, were conducted using soils created by mixing various proportions of the45 μm fractions of a lateritic soil. The dissolution of PR in soil, and the resulting changes in plant available P, were estimated by measuring increases in exchangeable Ca (ΔCa) and NaHCO3‐extractable P (ΔPb), respectively. The total fertilizer phosphate dissolved (ΔP) was calculated from δCa values based on the assumption that dissolution of PR released amounts of Ca and P in a constant ratio determined by the stoichiometry of the PR. δP increased with increasing content of<45 μm particles. APbalso increased with the percentage of<45μ fraction, with about 20% of AP being recovered as APb. A smaller proportion of dissolved P was soluble in NaHCO3for the soil comprising only the<45μ particles. The increase in δP with increased percentage of<45 μn soil was probably dueinter aliato the greater P‐sorption, Ca‐sorption and the pH buffering capacity of the fine grained

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1988.tb01205.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

SUMMARYTheQ/Icurves for Na in the Na–Ca system in some salt‐affected soils of Malaprabha and Ghataprabha river valleys lacked the curvature commonly seen in theQ/Icurve for potassium. The Malaprabha soils showed lowerAR0Na, NaLandBC0Navalues and higher energies of replacement of calcium by sodium than the Ghataprabha soils; the latter showed a higher affinity for Na than Ca. Two distinct linear parts of the quantity/ potential curves, with different slopes, indicated that Na is held in these soils in two characteristic types of exchange sites having different affinities for sodium. The intersection of the two linear parts corresponded to ESP values in the range of 13 to 64%. The change in the affinity at such a high degree of Na saturation was attributed to the presence of chloritized smectitic clays and sodium‐selective zeolite, such as analcite, reported in these

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1988.tb01206.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

SUMMARYSignificant increases in extractable ions resulted from air‐drying and grinding samples of two infertile Aquults. Effects of the sample preparation differed markedly between ions and between the two soils. Regression equations were calculated to predict extractable ions in dried, ground samples from extractable ions in fresh, unground samples and the relationships were compared between the two soil series. Regressions were significantly different between soils for extractable PO34, Mg++, and K+, but not for Ca++and Na+. Extractable NH+4and NO‐3in fresh, unground samples were not correlated with those in air‐dry, ground samples of either soil. Differences in response to preparation between soil types appeared to be related to the oxidative status of these soils in the field, wherein constituents of more poorly‐drained soils may be less stable to the oxidizing conditions of air‐drying and grinding. Such complexities suggest that effects of sample preparation should be considered when interpreting soil nutrient data for studies of forest nutrient cycling and forest soil

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1988.tb01207.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

SUMMARYA model to describe titration curves of mixed materials with variable and permanent charge surfaces is based upon published proposals, but includes the adsorption of potential‐determining ions on both kinds of surface, and the influence of the permanent charge. It also considers the interface formed by a system of capacitors in parallel and series. Some typical outputs of the model are given.The model was tested for mixtures of an iron oxyhydroxide and montmorillonite. The best fit of the model to titration data of the pure materials gave a set of values for the parameters that were used to predict the behaviour of the mixtures. It was concluded that most of the parameters estimated in this way reproduced the behaviour of the mixtures. However, the maximum density of sites on the oxide decreased when the latter was mixed with montmorillonite, and the binding constants of the clay mineral for the p‐d ions reached values, intermediate, between those of both minerals when the oxide was present in low proportion. These results suggested that some kind of association occurs between the solid surfaces, which would block part of the oxide surface. However, there is insufficient evidence to confirm this hypothe

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1988.tb01208.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

SUMMARYUniformly14C labelled straw and ryegrass leaf were incubated in soil in the proportions 0.5 and 1% w/w, respectively at 12°C for various periods up to 5 years.Samples were hydrolysed with 2.5mH2SO4under reflux for 20 min to release non‐cellulosic sugars and subsequently with 12 M/0.5mH2SO4to release glucose from cellulose‐like polymers. Total radioactivity was determined in whole soil and hydrolysates and in individual sugars.Fitting the data to simple exponential equations, total and 2.5mH2SO4hydrolysate radioactivity were best expressed by three part exponential functions, whereas radioactivity in 12M/0.5M H2SO4hydrolysates and sugars were best expressed by two part functions, except for arabinose from the straw, for which a three‐part function was better.A comparison of the fit was made with that using the single‐term exponential expressions devised by Janssen, 1984 and Weibull, 1951 and with a modification of the two part exponential expression by the substitution of one term by the Weibull expression. Apart from the Weibull expression on its own, there was no significant difference between the expressions.It is suggested that, even for well defined carbohydrate components of the substrate, the decomposability changes with time because of their increasing inaccessibility to microorganisms, rather than that several components are present each with a different constant rate of decom

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1988.tb01209.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

SUMMARYThe response of the soil microbial biomass to cereal straw incorporation was assessed for three sites in Eastern Scotland. Increases in the C:N ratio of the biomass, due to straw inputs, were greater for soil with a history of straw incorporation than soil with no previous incorporation history. The biomass C:N ratio response to straw inputs was associated with increases in the fungal component of soil microbial respiration, fungal plate count (total and cellulolytic) and FDA‐active lengths of fungal hypha

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1988.tb01210.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

SUMMARYThe protonation reactions of fulvic acids are described in terms of a model involving a mixture ofnmonoprotic acids HA, HB, HC … pH titration data were analysed by nonlinear least squares methods, using a model havingnindependent ‘titration’ (protonation) constants,Kii=1 ton, andn–1 independent acid concentrations. The best fit was obtained withn=4. The results for three fulvic acid samples were in the range logK16.5–6.7 (∼8% of total carboxyl acidity), logK25.3–5.6 (∼15%), logK33.9–4.8 (∼20–30%) and logK42.6–2.7 (∼50–70%).The results indicate a comparatively small proportion (∼ 10–20%) of polyprotic carboxyl moieties in the diverse fulvic acid structures. They give some support to the Wershaw model of fulvic acids as strongly associated aggregates of acids, each of com

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1988.tb01211.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY