摘要:

SummaryClod crushing resistance, bulk density, moisture content, and size distribution, together with fifteen bulk soil physical properties, were determined at thirty sites. Regression analyses indicated that the plasticity index of the soil is the principal property affecting both the clod crushing resistance and the yield of clods. Other less closely related properties are not always consistent in their effect between clod size ranges. A‘clod factor’ was derived from the product of the clod crushing resistance and the weight of clods in the ridge for each soil. The clod factor is linearly correlated with plasticity index (r= 0·587,P= 0·002) and a clod factor>1000 was found for soils with a plasticity index greater than about 5. Harvest observations suggest that where the clod factor exceeded 1000, the efficiency of a mechanical potato harvester was re

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1976.tb01969.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

SummaryThe Langmuir adsorption equation was found to describe Cd adsorption from dilute solutions at 5°C and 25°C for ten soils from Tuscany. The calculated Langmuir adsorption maxima (Q) and bonding energy coefficients (K) were well correlated with CEC and organic matter content.On the basis of the temperature effect onQandK, the mechanism of Cd adsorption is discusse

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1976.tb01970.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

SummaryWe studied the properties of the soluble and dispersed compounds of Cu, Mn, Co, Ni, Pb, Zn, and Cd formed by the action of aerobically decomposing plant matter on the respective metal oxides. The metals were mobilized partly in association with colloidal humified organic matter, and partly in true solution as complexes that seemed to be anionic.In the presence of a clay soil there was no net mobilization of colloidally bound Cu, but the dialysable Cu complex was not appreciably sorbed by the mineral colloids and was leached from the reaction mixture.The metals were not precipitated under alkaline conditions from the dialysable complex forms. Material with similar complexing properties was found in the dialysable fractions of a soil organic matter extract, of water squeezed from a raw peat, and of laboratory lysimeter solutions from a podzol underCalluna.Below about pH 6 the exchange of Cu on a soil clay was not affected by the presence of colloidal decomposition products of lucerne. With Co, Ni, and Zn the corresponding pH value was about 4, and the critical value for Cu in the presence of colloidal soil organic matter was also about 4. Below these values the metal and organic matter sorption curves were diametrically opposed so that under these conditions Cu is apparently not strongly bonded to colloidal organic matter.

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1976.tb01971.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

SummaryThe equilibria as well as the rates of adsorption and desorption of the ions Pb2+, Cu2+, Cd2+, Zn2+, and Ca2+by soil organic matter were determined in batch experiments as a function of the amount of metal ions added to an aqueous suspension of HCl‐washed peat. Simultaneous determination of the metal ions and hydrogen ions in the solution by atomic absorption spectrophotometry and pH‐measurements showed that the adsorption of one divalent metal ion by peat was coupled with the release of two hydrogen ions. Since this equivalent ion‐exchange process causes a corresponding increase of the electric conductivity of the solution, the rates of the adsorption and desorption processes were determined by an immersed conductivity electrode.The distribution coefficients show that the selective order for the metal adsorption by peat is Pb2+>Cu2+>Cd2+≌ Zn2+>Ca2+in the pH range of 3·5 to 4·5. The slope of ‐2, as observed in a double logarithmic plot of the distribution coefficients versus the total solution concentration confirms the equivalence of the ion‐exchange process of divalent metal ions for monovalent H3O+‐ions in peat. The absolute rates of adsorption, as well as the rates for the fractional attainment of the equilibrium, increase with increasing amounts of metal ions added. This behaviour is also observed for the subsequent desorption of the metal ions by H3O+‐ions. At a given amount of metal ions added, the absolute rates of adsorption decrease in the order Pb2+>Cu2+>Cd2+>Zn2+>Ca2+, while the rates for the fractional attainment of the equilibrium decrease in the order Ca2+>Zn2+≌ Cd2+>Pb2+>Cu2+. The half times for adsorption and desorption were in the r

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1976.tb01972.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

SummaryThe ion exchange equilibria involving the interaction of nicotine with Almontmorillonite was studied thermodynamically. The exchange isotherms at 30° and 60°C indicated a preference for Al ions by montmorillonite as compared with nicotinium ions. A separation factor supported the conclusion. The enthalpy gain indicated tighter binding of Al. The entropy gain indicated a diffused and disordered arrangement of nicotinium ions in the Goüy layer with Al forming a more ordered arrangement in the Stern lay

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1976.tb01973.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

SummarySoil properties were significantly related to the adsorption of aniline and p‐chloroaniline, greater adsorption always occurring with p‐chloroaniline. Multiple regression analysis indicated that the organic matter plus available water (or clay) was better than the simple linear relationship, with organic matter alone. The resulting equations accounted for most of the variability in aniline or p‐chloroaniline adsorbed (R2= 0·92 and 0·94, respectively). The contribution of organic matter to the adsorption was calculated as 79 and 77 per cent for aniline and p‐chloroaniline.Experimental data on partially oxidized soils emphasized the major role played by soil organic matter. The variability in adsorption was mainly due to the organic matter left after oxidation (R2= 0·72 and 0·64 for aniline and p‐chloroaniline). No other combinations of variables significantly improved these

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1976.tb01974.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

SummaryThe reaction of sodium fluoride solution with soils and soil minerals at constant pH has been assessed as a possible single‐value characteristic in the classification of soils, particularly those containing significant amounts of poorly ordered inorganic material. A suitable method involves reaction of the soil or clay at 25°C with 0·85 M sodium fluoride at pH 6·8, the amount of OH−released after 25 min being taken as the single‐value characteristic.There was a statistically significant correlation between the amount of OH−released and the amount of alumina extracted with cold 5 per cent sodium carbonate solution from both freely drained and poorly drained Scottish soils. The multiple correlation coefficients were improved for freely drained soils by including the dithionite‐extracted ferric oxide and the silica soluble in 5 per cent sodium carbonate solution. The procedure is not suitable for surface soils, because of interference by organic matter, or for carbonate‐containing soils unless carbon

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1976.tb01975.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

SummaryA peaty podzol developed on glacial drift derived from chlorite‐schists near Loch Awe, Argyll, contains up to 25 per cent titanium dioxide in the clay fractions after removal of organic matter and free iron oxides. Electron microscopy reveals that this titanium is almost entirely in the form of cryptocrystalline anatase which is amorphous to X‐rays and which is removed by the HF method normally used to concentrate anatase and rutile in soils. The anatase has probably formed as a result of the weathering of sph

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1976.tb01976.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

SummaryThe addition of 2.5 mg/l of polyacrylamide to 0.5M NaHCO3used as an extractant for ‘available’ phosphate overcame most of the analytical difficulties associated with the use of activated carbon which was recommended in the original procedure of Olsenet al.(1954). No significant differences in the amount of P extracted were found between polyacrylamide and carbon and with the former, technical problems were greatly reduced. Consequently, the modification of the original method to incorporate polyacrylamide has been adopted in the Agricultural Development and Advisory Service of the Ministry of Agriculture, Fisheries, and Food as a standard method for the determination of available phosphate in so

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1976.tb01977.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

SummaryWhen two different soils were incubated after the addition of [14C] glucose in the dark at winter temperatures or at 5°C in the laboratory and then hydrolysed, radioactivity was detected in all seven common soil sugars except arabinose. In contrast, in incubations at 20°C, little radioactivity was found in the xylose. Examination of the microflora showed that the number of viable bacteria was one‐tenth at the lower temperatures, whereas the numbers of yeasts, fungi, and actinomycetes were unaffected. Analysis of cultures of representative microbial isolates showed that none of the fungi or actinomycetes and only 3 per cent of the bacteria synthesized xylose, compared with 85 per cent of the yeasts.It is concluded that when these soils are incubated at low temperatures xylose is synthesized principally by yea

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1976.tb01978.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY