ISSN:0010-3624    

DOI:10.1080/00103628809367974

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

This overview outlines some conceptual and practical problems associated with the important variables in soil acidity research, and makes some suggestions for improvement where appropriate.

ISSN:0010-3624    

DOI:10.1080/00103628809367975

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Studies conducted on the major characteristics of podzolic soils from northeastern Ontario, Canada, have shown that these soils are highly acidic, show intense weathering of minerals and considerable redistribution of both Al and Fe. Approximately 60% and 80% respectively of the accumulated Al and Fe in Bf horizons is in inorganically‐bound forms and secondary minerals formed during podzolization include an expandable 2: 1 clay mineral in the albic horizons and Al‐rich allophanes and ferrihydrite in spodic horizons. Studies on displaced soil solutions indicate significant contents of organically‐bound Al, the amounts of which decrease with depth as the proportion of inorganically‐bound Al increases. The application of phase diagrams and model calculations indicates that amorphous and/or poorly crystalline minerals may control the activity of Al3+in the soil solutions, and that the content of organically‐bound Al in solution could be described adequately by assuming complexation with relatively simple organic acids, such as salicylic acid.

ISSN:0010-3624    

DOI:10.1080/00103628809367976

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

A semi‐empirical model for predicting soil response to acid deposition which was developed at the University of Minnesota was applied to determine possible impacts on Alberta soils. The model predicts changes in pH, base saturation, and soluble Al content over time for given inputs of wet and dry deposition. It is based on relationships among pH, base saturation, and Al solubility of the soil and is applicable only to undisturbed soils. Simulations using the model provide an effective means of quickly predicting response over time and for comparing responses among different soil types. Simulations were carried out on selected Chernozemic, Luvisolic and Brunisolic soils. At an acid input level of 0.1 kmol(H+)ha‐1yr‐1, pH, base saturation and Al had not changed significantly within 100 years, except in the most sandy soils. Most of the soils changed notably within 100 years in response to acid loadings of 1 kmol(H+)ha‐1yr‐1. Various assumptions were made in this modeling exercise and the simulations must be considered as representing worst case scenarios.

ISSN:0010-3624    

DOI:10.1080/00103628809367977

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The objectives of this study were to establish the amount of soil acidification caused by nitrogen fertilizer; and to ascertain whether banding, “nest” placement, or using nitrification inhibitors lessened the effect. Field experiments were placed at 10 sites and were conducted for 1 or 3 years. Barley was grown after annual fertilizer application, and in the fall the crop was harvested, the soil cultivated and the soil sampled. The main experiment was at 3 sites: a Gray Luvisol, a Dark Brown Solod and a Black Chernozem. Fertilizers were ammonium nitrate (A.N.), ammonium sulphate (A.S.) or urea. Soil pH (0–15 cm depth) was lowered 0.2 to 0.3 units after 3 years on the Luvisol with the annual rate of 67 kg N/ha A.N. or urea. The effect was greater with A.S. The 202 kg N/ha rate resulted in marked pH depression with incorporation of A.S. or urea on soils (average pH reduction of 0.9 and 0.5 units, respectively). Banding resulted in only half as much pH depression. In the second experiment 56 kg N/ha of urea were applied annually at 2 sites. By the third year, soil pH was decreased by incorporated urea (only 0.1 to 0.2 units) but the band effect was not significant. A final year‐long experiment was conducted at 8 sites with 56 kg N/ha of urea, and on the average soil pH was decreased by 0.13 units with incorporated urea. In some instances, the decrease was nearly overcome by banding, nests (2.5 g of urea placed at points), or nitrification inhibitors. Considering all the experiments, soil acidification was slowed by more than half with banding, nesting or nitrification inhibitors as compared to incorporation.

ISSN:0010-3624    

DOI:10.1080/00103628809367978

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

At the time, rediscovery of exchangeable aluminum in the mid 1950's seemed to be a simplifying and unifying concept. That has not turned out to be the case. Rather, as more studies have been made we have come to know less what to expect in any given soil. Examples are polymer formation, interlaying of clay minerals with hydroxylated aluminum species and the reactions of aluminum with organic substances in soil. Viewed with the hindsight of 30 years, the exchangeable aluminum concept is still of great practical importance, but includes only one of the many fates of aluminum in soils. This paper discusses the findings made on aluminum since the 1950's and makes an attempt to rank their importance according to the opinion of the author.

ISSN:0010-3624    

DOI:10.1080/00103628809367979

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Three equations for estimating the concentration of free aluminium, [Al3+], from the activity of free fluoride, (F‐), were compared to assess their suitability for estimating [Al3+] in acid soil solutions and in competition studies. We then studied the ability of humic acids to compete with F for Al by comparing the behaviour of the humic acids in the presence of F and Al with that of several carboxylic acids under the same conditions. All three methods of estimating [Al ] were limited in their applicability to acid soil solutions but were uitable for estimating [Al3+] in competition studies when equimolar quantities of AlTand FTwere used. Humic acids extracted by NaOH and by Na2H2P2O7decreased the amount of Al complexed with F by 21 ‐100% at pH 4 and 6 and ratios of Cmoles of humic acid: F>l. The Al humate complex precipitated when the Al: humic acid ratio was >1. Both humic acids appeared to be more effective than simple carboxylic acids at competing with F for Al.

ISSN:0010-3624    

DOI:10.1080/00103628809367980

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Zinc sorption‐desorption and Zn fractions in three soils, a Dalhousie clay (DT: Eutric Brunisol), a St Bernard loam (ST: Melanic Brunisol) and an Uplands sand (UT: Ferro‐Humic Podzol), were studied with and without added P at different pH values. Phosphate addition increased Zn sorption (Zns) in the order: DT clay > ST loam > UT sand. A positive correlation was noted between Znsand pH for soils treated with and without P. Phosphate addition reduced Zn desorption (ZnD) especially at low pH and was attributed to P induced pH effect. At high pH values, the P effect was less important. An increase in pH value resulted in less 0.5 M KNO3‐extractable Zn (ZnKNO3) and more 0.5 NaOH‐Zn (ZnNaOH) and HNO3extractable Zn (ZnHNO3). Compared with zero P treatments, P addition reduced ZnKNO3at low pH value but increased ZnNaOHat all pH values.

ISSN:0010-3624    

DOI:10.1080/00103628809367981

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Acid sulphate soils from central Alberta were analyzed for mineralogical composition, pore water chemistry, and content of arsenic in order to determine the stability and weathering of minerals and the form, distribution, and mechanisms involved in the accumulation of native arsenic within the soil solum and acid shale parent materials. Weathering of pyrite in the soil solum resulted in strong acidity (pH values near 3) and formation of natrojarosite, selenite, and iron oxyhydroxides. Analyses for total As in soil and segregated mineral samples indicated the element partitioned into iron rich phases. Content of As in some samples of iron enriched soil were as high as 500 mg/kg. Use of selective extradants for estimation of Ca‐, Al‐, and Fe‐arsenate forms provide limited information in this study. Results of thermodynamic modeling of pore water chemistry using the MINTEQ computer code were compared to the empirical data on mineral association of As and mineral alteration during the genesis of the acid sulfate soil. The thermodynamic analyses indicated arsenate precipitates would not be stable under present soil solution conditions.

ISSN:0010-3624    

DOI:10.1080/00103628809367982

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Soil pH measurements are often used in land use planning, litigation of damage claims and environmental regulation in the energy industry. Lengthy explanations of the nature of soil acidity to audiences without a scientific background, such as judges, quasi‐judicial bodies, farmers and professionals are often required. Involvement requires a command of soil acidity measurement and testing procedures, correct application and extension of ‘state of the art’ soil acidity and acidic deposition research, and the ability to overcome sceptical or preconceived notions. Spatial and temporal variability in pH is sometimes a factor overlooked in these situations. Data is presented for a wide range of Alberta soils in the last decade, based on observations of soil pH in monitoring plots and programs across the province.

ISSN:0010-3624    

DOI:10.1080/00103628809367983

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor