摘要:

SummaryThe amounts of P applied cumulatively to a neutral arable soil (pH 7.1–7. in 0.01M CaCl2) at Rothamsted, as farmyard manure, alone or with superphosphate, which were converted to organic P in 100 years ranged from 18 to 44 μg P/g of soil (0–23 cm). Superphosphate alone (3300 kg P/ha) slightly lessened the total organic P in the soil. Neither farmyard manure nor super‐phosphate significantly changed the amounts (38 to 42 μg P/g) of inositol penta‐ and hexaphosphate in these soils. In the surface layers (0–7.5 cm) of soils from permanent grassland at Rothamsted, superphosphate (3370kg P/ha) increased organic P by 134 μg P/g at pH 4.5 and 19 μg P/g at pH 6.5, about 6 and 1 per cent respectively of the P remaining from superphosphate applied cumulatively since 1858. In the sub‐surface layers (7.5–23 cm) superphosphate increased organic P by 93 μg P/g at pH 4.5 and 62 μg P/g at pH 6.2, about 18 and 10 per cent respectively of the P remaining from superphosphate. The sum of inositol penta‐ and hexaphosphates accounted for 32 per cent at pH 4.5 and 21 per cent at pH 6.5 of the increases in organic P in the surface layers and 45 per cent and 26 per cent in the sub‐surface layers at pH 4.5 and 6.5 respectively.Superphosphate (1260–2100 kg P/ha) applied intermittently or cumulatively increased total organic P by 19 to 52 μg P/g and inositol penta‐ and hexaphosphates by 13 to 17 μg P/g in acid tea soils (pH 3.2–3.4) from Georgia, U.S.S.R. Rock phosphate (510–1020kg P/ha) applied cumulatively had no effect on either the total organic P or the inositol P in acid t

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1973.tb00736.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

SummaryOrganic matter content was found to have a dominant effect on both the bulk and true densities of soil in the organic and eluvial horizons of the podzolic soils examined. The soils were stone‐free, structureless, and of similar texture. The effects of organic matter on bulk density were described by the equation:A similar equation was devised for true density. Use of these equations indicated that, in the soils examined, total pore space could be predicted from organic matter content measured as per cent loss on ignitio

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1973.tb00737.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

SummaryThe effect of pH on the incorporation of six14C‐labelled amino acids and a dipeptide into humic acid extracted from a podzolic soil was examined. Maximum incorporation was found to occur at a pH which coincided with the apparent dissociation constants of their α‐amino groups. Incorporation took place, into forms which were both acid‐hydrolysable and non‐hydrolysable, the latter accounting for between ten and twenty per cent of t

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1973.tb00738.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

SummaryThe clay mineralogy of thirty‐two profiles located mainly in the Vale of Strathmore and developed on glacial till derived from Lower Red Sandstone sediments and lavas has been investigated by X‐ray diffraction. The soils were selected so that the parent material was related predominantly to one of the rock types common in the Lower Old Red Sandstone succession—namely, marl, sandstone, lava, or conglomerate. Comparison of the<1.4μm fractions separated from fresh rock samples with those separated from the C horizons of the soils clearly established the dominant influence of parent rock on the soil‐clay mineralogy. The clay minerals inherited by the soil often include unusual trioctahedral expansible minerals such as saponite, interstratified vermiculite‐chlorite, and smectite‐vermiculite, as well as more common types like mica, montmorillonite, and chlorite. Kaolinite is also found but it is not certain that it is only of inherited origin. Weathering of the clays during soil formation brings about complete degradation of the expansible trioctahedral minerals, a process usually well advanced in the B or even at the top of the C horizon, and vermiculitization of mica. The latter process occurs mainly in the A horizon, with concomitant precipitation of interlayer aquohydroxy‐aluminium ions thereby forming a vermiculite‐chlorite intergrade. Chlorite and kaolinite appear to be little affected by weathering. The weathering transformations are most pronounced in freely drained acid soils (pH

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1973.tb00739.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

SummaryPublished and unpublished data on the amounts of organic matter and nitrogen in the surface soils of the West African savanna are reviewed. In general, amounts are small; the mean carbon content of soils from 605 well‐drained sites was 0.68 per cent.Two important factors governing amounts of organic matter in well‐drained soils appear to be the clay content and a moisture factor related to the length of the wet season and represented here by mean annual rainfall. Multiple linear regression on soil clay content and rainfall accounted for 46.5 per cent and 57.2 per cent, respectively, of the observed variability of soil carbon and nitrogen contents. These findings suggest that the low levels of organic matter in savanna soils arise from their predominantly sandy nature and from the relatively low rainfall. In poorly drained soils organic matter levels are higher but are less significantly related to clay content and rainfall. The influence of human interference and of parent material and altitude on organic matter is demonstrated in the context of geographically limited areas within the savanna for which more detailed information was availa

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1973.tb00740.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

SummaryIncubation of soil with14C‐rye straw for 448 days resulted in the evolution of about 50 per cent of the carbon of the substrate as CO2The two main sugars of the straw, glucose and xylose, were degraded to approximately the same extent (70 per cent). The same results were obtained whether the soil was derived from granitic or basic igneous parent material.There was very little transformation of the substrate to galactose, mannose, arabinose, rhamnose, or fucose, and a much slower rate of degradation than with soil incubated with14C‐glucose over a similar period.Hydrolysis of the soil samples by a preliminary treatment with 5 N H2SO4, before treatment with 24 N H2SO4, followed by heating with N H2SO4did not release significantly greater amounts of sugar than treatment with 24 N H2SO4and N H2SO4alone. Separate analysis of the hydrolysates showed that 90 per cent of each of galactose, mannose, arabinose, xylose, rhamnose, or fucose had been extracted by 5 N H2SO4, but only 50 per cent of the glucose.Fractionation of the straw‐soil mixture after 224 days incubation showed that the specific activity of the glucose was higher in the humin fraction than in the fulvic acid, as would be expected if the remaining14C were still in the form of unchanged plant material.This evidence that plant polysaccharide persists in soil could explain the presence of much of the xylose in the soil organic m

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1973.tb00741.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

SummaryThe residua system of chemical weathering is here defined as the chemical sink towards which the bulk of earth's surface materials (i.e. the silicate rocks) trend during weathering. Chemically the system is defined in terms of four major components, SiO2–Al2O3–Fe2O3–H2O, evidence being derived from relative solubilities of components under earth‐surface conditions; from experiments in which weathering environments have been simulated in the laboratory; and from field studies of rocks and their weathered mantle. The residua system can be used as a framework to construct mineral facies diagrams showing assemblages of the commonest earth‐surface minerals that occur within it: quartz, gibbsite, goethite, kaolinite, halloysite. In a qualitative manner the facies diagrams can then be interpreted in terms of the partial pressure of water (PH4O) and the temperature, T. The usefulness of this approach in systematizing studies of soil genesis is illustrated with reference to the weathering o

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1973.tb00742.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

SummaryA model (based on the short‐ and long‐term Q/I relations of K in a soil, on graphs of K‐uptake by crop against post‐uptake K‐activity ratios, and the exhaustion value of K‐activity ratios below which K can no longer be taken up) is presented by means of which to estimate the amount of labile K in a soil, and to compare the contributions of labile and fixed K to plant uptake. The application of the model was partially explored in a field experiment. Relative values for the magnitudes of the pools of labile and fixed K developed by 4 years’build‐up treatments were calculated on the basis of the model. Their relative contributions to the K taken up by a ryegrass test crop in the following year were calculated from the soil Q/I relations, and the measured uptakes of K. While the data were incomplete and so could not provide conclusive evidence for the model, the values produced were sensible and appare

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1973.tb00743.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

SummaryThe chloride‐exclusion volume of calcium‐saturated specimens of two bentonites and seven soils were determined over a range of electrolyte concentrations. These systems are believed to approximate the flocculated condition of most Manitoba soils. The montmorillonite was found to be arranged in tactoids or crystallites having an approximate 19Å basal spacing. The assumption of complete chloride exclusion from the interlayer volume over most of the concentration range combined with exclusion according to Gouy theory by the external surfaces provided a reasonable explanation of the experimental data. The number of montmorillonite layers comprising a tactoid, as calculated from the negative absorption determinations, was found to be strongly dependent upon the particle size of the montmorillo

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1973.tb00744.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

SummaryHeats of adsorption and adsorption isotherms of ammonia gas were measured at 300K(27 °C) on outgassed soil saturated with Na+, K+, NH4+, Ca2+, or Mg2+ions. The Ca and Mg soils adsorbed apparently one more NH2molecule per exchangeable ion than the Na and K soils, mostly in the relative pressure range o to 0.005, but not much more than the NH4soil. The initial heat of adsorption was c. 75 kJ mol‐1on the Ca and Mg soils and c. 60 kJ mol‐1on the other soils. The results suggest that most NH, is sorbed on these soils through reactions not involving exchangeable cat

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1973.tb00745.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY