摘要:

SummaryAqueous leaf extracts were obtained at regular intervals during the 1967 growing season fromPopulusבNorthwest’ (Hort.). After lyophilization the samples were analysed for acidity and ash, sugar, phenol, and N contents. They were examined with thin‐layer chromatography and infra‐red spectroscopy.Simple phenolic compounds, present earlier in the growing season, made way for more complex phenols as the season progressed, and the extracted material became more acid. The increased loss of phenolic compounds and acids from the leaves toward the end of the summer continued during their first autumn on the ground. The polysaccharide content decreased during the season. The infra‐red spectra of the lyophilized material were useful in making comparisons. It was concluded that, for percolation and transformation studies of Chemozemic soils, aqueous leaf extracts obtained during late summer or autumn should be the mos

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1970.tb01157.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SummarySixteen soils and 4 soil preparations were cropped exhaustively with ryegrass in the glasshouse and monocalcium phosphate potentials (½pCa+pH2PO4=1) were measured after each of 6 consecutive harvests. The amounts of phosphorus (Q) removed from the soils by ryegrass accounted for 95·1–96·6 per cent of the variance in1for 3 soils and 2 soil preparations (P<0·001), for 88·4–93·7 Per cent of the variance for 6 soils and 2 soil preparations (0·001

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1970.tb01158.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SummaryMixtures of Woburn (non‐calcareous) and Barnfield (calcareous) soils, with and without added monocalcium phosphate, and of Woburn soil with added CaCO3, were stored moist in an incubator at 25 ± 2 °C. Equilibrium phosphate concentrations in 0·01M CaCl2and pH were measured on moist soils and mono‐calcium phosphate (½pCa+pH2PO4) and lime (pH–½pCa) potentials were calculated at intervals up to 670 days. Most of the mixtures remained under‐saturated with respect to CaCO3; values of ½pCa+pH2PO4and pH–½pCa changed during storage but remained close to the solubility isotherm for octacalcium phosphate (OCP). Mixtures which reached equilibrium with CaCO, remained undersaturated wit

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1970.tb01159.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SummaryIn an experiment on green manuring started at Woburn in 1936, farmyard manure (FYM) was applied in alternate years until 1954 and straw similarly from then until 1963. Various green manures were grown from 1936 to 1953. From 1954 to 1963 ryegrass and trefoil were grown either each year or in alternate years; in 1964 and 1965 they were grown each year.After annual cropping without organic manuring the organic‐C and total‐N decreased from 0·86 per cent and 0·091 per cent respectively in 1936 to 0·76 percent and 0·082 per cent in 1966. Ploughing in straw alone approximately halved the loss. FYM and green manures both maintained the original percentages of soil C and N. The effect of FYM and straw applied together was approximately the sum of the effects of FYM and straw applied separately.Of the green manures ploughed in, trefoil returned the most nitrogen to the soil. Trefoil increased and ryegrass decreased the mineralizable‐N in

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1970.tb01160.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SummaryMicromorphological studies were conducted on Orthic Black (chernozem), Orthic Dark Grey (degraded chernozem), and Orthic Grey Wooded (podzolic) soil profiles, developed on medium‐textured, moderately calcareous glacial till. The surface horizons ranged in characteristics from the plasma‐rich Ah horizon of the Orthic Black, which had chernozemic fabric, to the plasma‐deficient Ae of the Orthic Grey Wooded, which showed isoband fabric. The B horizons exhibited an increase in ped density, going from the Orthic Black to the Orthic Grey Wooded, with concomitant increase in cutan formation.The interpretation of micromorphological features led to the conclusion that many field‐observed characteristics are manifestations of the microfabric of the various horizons. It is suggested that physical disturbances such as freezing and thawing, wetting and drying, and root pressures play an active role in pedo

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1970.tb01161.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SummaryA study was made of the amounts and distribution of C, N, S, and organic P accumulated over a period of 10 000 years of soil development on wind‐blown sand. After initial rapid rates of accumulation of C, N, and organic P during the first 1000 years, subsequent rates of gain were slower, but steady states for C, N, and S had still not been reached after 10 000 years. Sulphur declined during the first 50 years of soil development but then increased in a parallel fashion to organic C. During 10 000 years, gains of organic C, total N, total S, and organic P were 204 000, 9800, 1180, and 1170 kg/ha m profile, respectively. Gains in total N and S in the older soils are readily accounted for by returns in precipitation. Pronounced changes in soil organic matter composition during 10 000 years are reflected in the widening of the C/N ratio (8 to 20) and the C/organic P ratio (39 to 159

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1970.tb01162.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SummaryIn a simple dry soil system in which erosion is taking place by virtue of the impact of saltating sand grains, the intrinsic variables affecting soil resistance can be investigated with the aid of a mathematical model. The soil erodibility depends on the cohesiveness of the soil which is indicated by the tensile strength. This is directly proportional to the packing density of the system, to the co‐ordination number of the particles, and to the inter‐particle bond strength. Tensile strength is inversely proportional to the cube of the particle diameter. In a cohesive material any decrease in the particle size produces a great increase in the tensile strength and hence the mechanical stability is improved, but because the particles are lighter they are easily eroded once they are distur

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1970.tb01163.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SummaryThe rapid soil mapping required in developing countries can only be done by relating soils to land form and geology. A usefulness classification of mapping units is suggested. The most useful contain the least soil variation. Units with regular soil variation within them are more useful than those with random variation. In the Nigerian Savanna the most useful units are on hill remnants and homogeneous sediments, particularly coarse siliceous sandstones and fixed dunes. The least useful are on dissected areas, heterogeneous sediments, igneous and metamorphic rocks. The least fertile soils often dominate the most useful units. Rapid soil mapping should be useful in the north and the lower Niger and Benue valleys.

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1970.tb01164.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SummaryPhosphate extracted by ion‐exchange resins in the chloride and sodium forms from a deep river‐gravel soil under widely varying conditions is always from the isotopically exchangeable or‘labile’ pool. At any reaction time, a constant fraction of this pool is desorbed by the chloride form of the anion‐exchange resin alone, irrespective of the pH and phosphate manuring of the soil. If, however, a sodium: cation exchange resin is included, increasing fractions of the‘labile pool’ are desorbed with decreasing soil acidity.Phosphate desorption by the anion‐exchange resin alone and with the cation exchange resin is shown to be‘particle‐diffusion’ controlled in the anion exchange resin and neither a‘chemical reaction’ nor a‘film‐diffusion’ mechanism. Over the pH range 4·5–8·5, values between 4·8 and 0·9 × 10‐9cm2sec‐1were calculated for the interdiffusion coefficient of the phosphate: chloride exchange process in the resin.The isotopically exchangeable phosphate in the soils seems to behave like sparingly soluble or weakly dissociating compounds towards ion‐exchange resins and its rate of desorption depends

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1970.tb01165.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SummaryOrientation diagrams are used to show differences in the orientation of birefringent domains in the S‐matrix, and in sub‐cutanic features of the vo‐insepic fabric of two West Indian soils. Such orientation diagrams could prove useful in helping to characterize plasmic fa

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1970.tb01166.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY