摘要:

SUMMARYThe shear moduli of the<2 μm size fraction of three soils have been measured for samples of 10–35% w/w solid. Samples were thixotropic, the shear modulus increasing with time. This increase can be described by simple models and visualized in terms of the formation of links between particles. For a given soil the shear modulus increases with ionic form in the order Ca2+∼Mg2+

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1987.tb02117.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYDifferential heats and isotherms for K‐Ca exchange and CEC values show that simulated weathering by grinding and NaTPB treatment of the coarse clay fraction of a rice‐growing marsh soil exposed vermiculitic layers to reaction with ions in solution, and also created more montmorillonitic layers and uncharged clay. Calcium selectivity was also increased, especially at K saturations>50%. Changes in the CEC values of the fine clay, fine silt and coarse silt by such treatment, compared with that in the coarse clay fraction, were used to predict changes in the layer charges of their component phyllosilica

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1987.tb02118.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYSamples from six ash soils were chosen with a range of Fe and C contents. Stabilities over the aggregate size‐range from2 mm were measured by selectively removing aggregating agents from fresh soil samples. Wet‐sieving was also carried out on both field‐moist and air‐dried 3.4–2.0 mm macroaggregates.Macroaggregate stabilities were closely related to C contents and were also enhanced by high contents of allophane and/or Feox. High water contents decreased the stability of field‐moist macroaggregates.Clay‐sized material was most readily dispersed with Na resin after pretreatment with hydrogen peroxide; removing the latter alone was usually ineffective in d

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1987.tb02119.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYThe adsorption of sulphate and fluoride by three variable charge soils was studied. Adsorption increased with increase in the amount of sulphate added at constantpH, and decreased with increase ofpH.The ratios of the amount of released OH−to that of the adsorbed SO2‐4at pH 5–0 were 0.12, 0.14 and 0.20 for the three soils, respectively, much lower than the corresponding OH−/F−ratios which ranged from 0.3 to 1.0. For a ferric acrisol the OH−released accounted, on average, for only 15% of the SO2‐4adsorbed, leaving more than 60% to be explained by the decrease in positive charge and the increase in negative charge carrie

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1987.tb02120.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYThirty‐one soil solutions were extracted by immiscible displacement with CCl4under high speed centrifugation from sub‐horizons of three podzolic soils from north‐eastern Ontario, Canada. The solutions were analysed for major cations and anions and a speciation of dissolved Fe and Al was attempted to distinguish ‘free’, ‘organically bound’ and ‘inorganically bound’ species. Results indicated that the Ae (E) horizon solutions were of low pH and contained mainly organically bound Fe and Al. With depth,pHs increased, ionic strengths decreased and the relative proportion of inorganically bound Fe and Al increased. Although application of phase diagrams permitted only a semi‐quantitative interpretation of the data, all horizon solutions, with the exception of some Ae solutions, appeared supersaturated with respect to likely occurring crystalline and amorphous aluminosilicates [kaolinite, halloysite, allophane (Al:Si=l) and imogolite]. Of the phases considered, reactions involving imogolite‐allophane, gibbsite‐halloysite, gibbsite‐allophane and gibbsite‐imogolite all appeared reasonable in controlling the content of Al3+and H4SiO4in solution, although the presence of gibbsite and imogolite could not be definite

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1987.tb02121.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYUptake of K was measured using a single onion root technique with four soil cylinder diameters, and measuring changes in exchangeable K in the soil. Baldwin's model fitted the measured uptake when only exchangeable K was taken up, but that of Heming&Rowell allowed predictions of uptake of both exchangeable and non‐exchangeable K (Knes) after fitting the necessary parameters. Release of Knexoccurred in both 3 mm and 6 mm cells (root densities of 14cm cm”−3and 3.5 cm cm−3) in 10 days. Predictions were made for longer times and differing soil water contents: after four weeks at a water content midway between field capacity and wilting point the contribution of Knexto total uptake was significant (up to 60%) for plants with high root de

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1987.tb02122.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYMeasurements and predictions of uptake of non‐exchangeable K have been made for three soils. Exchangeable K is important in controlling the extent to which non‐exchangeable K is used; rate of diffusion of exchangeable K seems less important. Rate of release of non‐exchangeable K did not vary much between soils, but critical release concentrations in solution varied from 33 to 85 μM with little obvious effect on the extent of use of non‐exchan

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1987.tb02123.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYStability changes during ageing (sterile) or incubation (non‐sterile) of both natural field aggregates and remoulded aggregates from five soils were studied for periods up to 30 days. Growth of fungal hyphae, estimated by ergosterol measurement, corresponded to temporary stability increases in both types of aggregates during the first 15 days. Thereafter, fungal hyphae disappeared and were replaced by actinomycetes and bacteria. Increased stability due to entanglement by hyphae was comparable to that due to thixotropy in remoulded aggregates. Bacterial growth accompanied the fall in stability associated with fungal decline, but had little direct effect in stabilizing soil aggregates. Destruction of polysaccharides by periodate oxidation greatly diminished aggregate stability. The role of bacterial polysaccharides in soil aggregate stability is discusse

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1987.tb02124.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYTorus‐shaped features 1–7 urn in diameter were found on the smooth surfaces of the structural units of a Red Podzolic Soil (Udic Haplustalf) B horizon and on the smooth surfaces within the columnar structures of a Solodized Solonetz (Typic Natrustalf)‐SEM&EDS were used to characterize these features, and to determine their probable pedogenesis. The size range was bimodal in the Red Podzolic B horizon, being either ∼5 μm or ∼2.0 um. In the Solodized Solonetz all tori were ∼ 1.5 μm in diameter. The larger tori consisted of fine‐clay coated collapsed fungal spores, whilst the smaller tori were fine‐clay coated collapsed bac

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1987.tb02125.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYEleven horizons of acidic soils in mid‐Wales developed from Lower Palaeozoic sedimentary rocks were examined. Selective extraction of Al and Si provided evidence against the occurrence of significant quantities of poorly ordered Al‐silicates. Fe0was weakly correlated with Al0, but very closely correlated with Al0minus Al extracted by cold 5% Na2CO3, implying that poorly ordered Al occurs in part as a substituent in Fe oxide and in part in a form unassociated with Fe oxide. Support for this was obtained by analysis of oxide fractions concentrated from aqueous suspensions by sequential ultracentrifugation and through the examination of synthetic Al‐substituted Fe oxides. Fe oxide containing Al substituted at an almost constant level was the dominant constituent of the poorly ordered fraction in four of the five Bs horizons examined. The occurrence of Al in this form is an important mechanism by which Al is retained in aerobic but highly acidic Bs hor

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1987.tb02126.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY