摘要:

SummaryLangmuir adsorption isotherms are unlikely to be appropriate when applied to the adsorption of charged phosphate ions on charged oxide surfaces. It is more likely that the adsorption model proposed by Bowdenet al.(1973, 1974 and 1977) for adsorption on variable charge variable potential surfaces will be applicable. Theoretical isotherms were calculated from this model for a series of pH values and ionic strengths. It is shown that these isotherms can be split into two or more Langmuir isotherms in much the same way as has been done by various authors for experimental isotherms. The parameters of the Langmuir isotherms behave in the same way as those derived from the experimental isotherms. The charging characteristics of the theoretical isotherms are also similar to that observed experimentally.Because the model which is based on a single type of adsorption site is closely similar to the experimental isotherms, it is erroneous to split the isotherms into a series of Langmuir isotherms unless there are gooda priorireasons.

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1980.tb02059.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SummaryThe variation with water content is examined of soil cohesion, soil‐metal friction, susceptibility to soil compaction, implement draught and the slope and intercept of the virgin compression line of critical state soil mechanics theory. For a given soil, all these relations are shown to exhibit turning points at a similar water content which corresponds to the cone penetrometer plastic limit, as determined with a drop‐cone penetrometer, rather than the Casagrande plastic limit. The cone penetrometer plastic limit, which can also be more reliably determined than the Casagrande plastic limit, is the better indicator of soil behaviour in the field and of the water content at which the soil changes from the brittle to the plastic st

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1980.tb02060.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SummaryDrop‐cone measurements were made on undisturbed and remoulded samples of topand sub‐soil from two sites equilibrated at tensions between zero and 600 kPa (6 bar). All samples remained virtually saturated up to the highest tension. Within a few days after remoulding, cone penetration values had returned to those obtained on undisturbed samp

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1980.tb02061.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SummarySurface charge titration measurements, performed on goethite in the presence of absorbed herbicide ions, indicate that the result of adsorption is to cause an increase in the positive charge of the mineral surface. The titration results, used in conjunction with adsorption measurements to calculate the exchange coefficients for the adsorption reactions, show that there is a significant selectivity in adsorption of the herbicides over the indifferent counterion nitrate. This is believed to be due to the existence of favourable van der Waals interactions between the adsorbed herbicide ions.

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1980.tb02062.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SummaryUnder transient conditions, the precipitation of carbonates in a calcareous and a non‐calcareous soil was influenced by calcium, magnesium and bicarbonate ions from soil sources. These sources were: the soil solution, the soil exchange complex and the dissolution of aluminosilicates. There was no significant difference between the amount of carbonates which precipitated in the two soils when in contact with the same water. It was found that for small portions of water in contact with the two soils, precipitation of carbonates took place both from under‐saturated and the over‐saturated waters. As the cumulative amounts of water in contact with the soils increased, the amount of ions contributed by the residual soil solutions and the exchange complexes decreased, and the amount of precipitating carbonates decreased also. At very large cumulative amounts of water, the precipitation of carbonates in the soils was controlled by both the water and the ions released from the

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1980.tb02063.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SummaryThe effects of varying the pH and ionic strength, and the concentrations of organic matter, copper, calcium and phosphate upon the complexing of copper by extracts of humified organic matter from laboratory preparations, soil and peat were measured. The extent of complexing increased as pH increased and ionic strength decreased, and with increasing organic matter: copper ratios in a way consistent with the complexant being heterogeneous. Calcium competed with copper for organic matter, but the effect of phosphate was negligible. The extent of complexing at pH 7 by equal weights of colloidal and dialysable material from the same extract were usually similar. Weight for weight of organic carbon, alkali‐extracted humified organic matter complexed copper much more extensively than the corresponding water‐soluble mater

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1980.tb02064.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SummaryPerennial ryegrass growing in monolith lysimeters and treated with 400 kg N ha‐1as calcium nitrate labelled with nitrogen‐15 (10.5 atoms per cent), during one growing season recovered between 43 and 54 per cent of the fertilizer nitrogen. In the following year without further nitrogen additions 4.6–9.5 per cent was taken up, whilst in the fifth year the recovery was less than 1 per cent. The contribution of non‐fertilizer sources of nitrogen to the total nitrogen taken up by the plants during the season that nitrogen was applied was estimated using tracer methods to be about 13–14 g N m‐2year‐1. The estimate from measuring the nitrogen content of an unfertilized sward was 7 g N m‐2year‐1. The residual effects of a fertilizer application are likely to be detectable for a period of between 6 and 9 years.Losses of nitrogen to drainage in the winter after application represented 2–5 per cent of the fertilizer applied, whilst in subsequent years the amounts did not exceed 0.1 per cent. Mean concentrations of nitrate ranged between 4 and 16 mg N I‐1. Fertilizer contributed about 60–70 per cent of the total nitrogen lost in the first winter after nitrogen application and 45–60 per cent av

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1980.tb02065.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SummaryGrinding more than doubled the respiration rate of two silt loam soils, one arable and one grassland. The increases were smaller when the grinding treatment was given to portions of soils that had previously been fumigated with CHCI3and incubated, a treatment that greatly decreased microbial biomass.The results indicate that the flush of decomposition caused by grinding was in part derived from killed organisms and in part from enhanced decomposition of non‐biomass sections of the soil organic matter. Grinding killed about a quarter of the biomass in both soils. Carbon from killed organisms accounted for a quarter of the extra CO2–C evolved after grinding in the arable soil and almost half in the grassland soil. The extra non‐biomass organic matter decomposing after grinding amounted to about 0.5% of the soil organic carbon in both soils. This non‐biomass material rendered decomposable by grinding had a higher C/N ratio than the organic matter decomposing in ungrou

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1980.tb02066.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SummaryProposals are made for horizon designation of soils developed under mangrove vegetation and in polders in northern New Zealand. A model is presented for predicting the development of acid sulphate soils by field survey prior to reclamation.

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1980.tb02067.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SummaryQasim, some 500 km north‐west of Riyadh, is one of the agriculturally important areas of Saudi Arabia. Silt fractions of the soils of the Wadi ar Rimah and side wadis, classified as Torrifluvents, are characterized by high quartz contents and the universal occurrence of kaolinite and felspar, generally with plagioclase predominant; mica, chlorite and hornblende also generally occur. The clay fractions contain mainly palygorskite and a smectite‐mica interstratification with smaller amounts of kaolinite, traces of quartz and occasionally chlorite. Palygorskite generally increases in content with depth. Variations in mineralogy probably reflect changes in depositional conditions rather than pedogenic processes; possible reasons for the high palygorskite content are discussed. Sedentary soils (Torriorthents) reflect the mineralogy of the rock from which they were derived. In clay fractions from salt‐marsh soils (Salorthids) calcite reacts strongly with smectite‐mica dur

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1980.tb02068.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY