摘要:

SummaryZinc diffusion in goethite (α‐FeOOH) was examined theoretically and experimentally. Concentration profiles of zinc diffusion after various periods of time were determined in physically and chemically defined oxide pastes using a tracer technique. Apparent diffusion coefficients were calculated as a function of diffusible zinc concentration from these results and compared with values obtained indirectly from slopes of adsorption isotherms and experimentally determined impedance factors of the conducting media. To deal with a wide range of experimental conditions, a model for calculating zinc adsorption was applied and evaluated. Changes in pH across the diffusion profile due to zinc transport were postulated to account for some of the results. Where these effects were minimal, the agreement between the diffusion coefficients obtained by the direct and indirect methods was satisfactory. The contribution of surface diffusion to the total transport of zinc in the goethite paste was estimated to be very sma

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1975.tb01925.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SummaryChemical and mineralogical properties of five soil profiles of a catena in Iperu, Western State of Nigeria, are reported. The pH values of the subsoils are extremely acid. Acidity decreases with improved drainage in the subsoils (pH 4.0–5.8). The cation exchange capacity (C.E.C.) of the soils range from 3.0 to 16.2 me/100g of soil.The silt: silt+clay ratio, calcium: magnesium ratio and Fe2O3:Al2O3ratio are used as weathering indices. The low values of the silt: silt + clay index indicate that the soils must have undergone advanced weathering. The magnitude of the Ca: Mg ratio indicates that more calcium than magnesium is available in the soils. The values for sodium and potassium are extremely low. More iron than aluminium was extracted from the soils by the dithionite‐citrate method.Kaolinite is the most abundant clay mineral. Halloysite, interstratified clay materials, vermiculite, quartz, and mica are present in considerable amounts. The silt fraction in which quartz is the most abundant mineral, also contain some kaolinite and m

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1975.tb01926.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SummaryAn Elovich‐type equation has been used to describe the kinetics of isotopic exchange of phosphate adsorbed on the surface of gibbsite. The equation iswhereAandBare parameters; θ=bF/[b+a(I‐F];aandbare the molar concentrations of the phosphate on the crystal surface and in solution respectively and F is the fraction exchange of the radio‐isotope at time t. First‐order rate constants were obtained from the equation. The reference state for the first‐order rate constants, and the distribution of activation energies, for exchange can be related to the Elovich equation parameters. The kinetic results are consistent with SN1 dissociation or SN2 bimolecular solvolysis for the phosphate ligand. The eschange reaction is subject to an acid‐base catalysis the exact nature of which could not be determined from the av

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1975.tb01927.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SummaryHumus content, thickness of the accumulation horizon, soil texture, and depth of decalcification are all related to the slope of the soil surface in loess soils near Kraków.For example, humus content declines from 75 to 65 tonnes/ha as slope increases from 2 to 12°. Depth of decalcification which is about IOO cm on soils with slopes less than 2° is only about 50 cm on slopes of 12°.Such observations may prove helpful in the evaluation of the intensity of soil erosion processes on other loess areas physiographically similar to the region near Kra

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1975.tb01928.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SummaryThe concentration of nitrate‐N at 30 cm depth in a clay soil was 2–5 times greater (p<.05) after ploughing than after direct drilling during the winter and spring of 1972–3. However, by early May no significant differences could be detected between cultivation treatments. It is concluded that decreased mineralization of soil nitrogen in the direct‐drilled soil is the main factor responsible for the differences o

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1975.tb01929.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SummaryThe calculation of a discriminator between mull and mor humus types from the mass spectra of soil pyrolysis products, described earlier by Bracewell and Robertson (1973), used IIO normalized peak heights; these can be reduced to thirteen and the calculation simplified. Assumption of class for some soils, which was necessary in the previous method of obtaining the pattern classifier, has been obviated by the use of principal components analysis.

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1975.tb01930.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SummaryEighteen experiments were carried out in Wales and the West Midland Region, between 1966 and 1971 to compare granular basic slag with powdered basic slag and superphosphate (or triple superphosphate) as phosphatic fertilizers for rape and swede crops. At the swede sites additional comparisons involving ground mineral phosphates were also made.The fertilizer treatments were applied at sowing time and at rates supplying 28 and 56 kg P/ha for rape and 28 and 56, or 44 and 88 kg P/ha for swedes. Large increases in yield of rape and swedes to the lower rate of phosphate application were recorded at most sites but, in general, only very small additional responses were obtained to the higher dressing.For both rape and swede crops, the relative effectiveness of the different phosphatic fertilizers varied somewhat between sites. Comparisons of the superphosphate and basic slag treatments show that the former gave slightly higher yields at most sites. Granular basic slag was marginally inferior to powdered slag for swedes but in general the differences between the effects of superphosphate (or triple superphosphate) and the two forms of slag were small.The effects of the Gafsa phosphate treatments for swedes were variable, being as effective as superphosphate or basic slag at some sites and much less so at others. This inconsistency detracts from their over‐all usefulness. There was no definite advantage in the finely‐ground (80 per cent through 300 mesh (50 μm)) material over the relatively coarser (60 per cent through 100 mesh (150 μm)) product.Moroccan mineral phosphate was inferior to the Gafsa phosphates for swedes, particularly at the most responsive

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1975.tb01931.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SummaryLoss of fertilizer phosphate by adsorption on coal‐mine waste can increase the cost of reclamation schemes. Samples were taken from four typical coal‐mine tips in Central Scotland and the relationships between phosphate adsorption, Tamm A1 and Fe, pH, fraction less than 2 mm, and acetic soluble calcium and sulphate were studied. Only Tamm Fe was shown to be correlated with phosphate adsorption.Unburned (black) shale adsorbed more phosphate than burned (red) shale.Heat has also been shown to influence the levels of Tamm Fe and phosphate adsorption. This is of practical significance as high temperatures can be generated within the tips as a result of spontaneous burning of the waste mater

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1975.tb01932.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SummaryMost constituents of the adsorbing complex of the soil are cationic exchangers with variable exchange capacity: it is possible to study graphically exchanges involving the protons and two other cations. The representation developed here uses and generalizes the principle of the bicationic exchange isotherms in a square diagram. This helps to explain some experimental phenomena and enables the final equilibria of the exchange reactions to be forecast. The model seems useful for application in agronomy and physiology.

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1975.tb01933.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY