Total Potential Soil Acidity

So lOOg soil has total potential acidity Thus, total potential acidity [2(B-S)1 meq/100 g. 

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Phenolic compounds have also been oxidatively polymerized to humic substances by clay minerals (29) and by the mineral fraction of a latasol (66). After a 10-day equilibration period, montmoril-lonite and illite clay minerals yielded 44 to 47% of the total added phenolic acids as humic substances whereas quartz gave only 9%. Samples of a latasol yielded over 63% of the total amount, from mixtures in varied proportion, of mono-, di- and trihydroxy phenolic compounds as humic substances (66). Extractions of the reaction products yielded humic, fulvic, and humin fractions that resembled soil natural fractions in color, in acid-base solubility, and in infrared absorption spectra. Wang and co-workers (67) further showed that the catalytic polymerization of catechol to humic substances was, enhanced by the presence of A1 oxide and increased with pH in the 5.0 to 7.0 range. Thus the normally very reactive products of Itgnin degradation can be linked into very stable humic acid polymers which will maintain a pool of potentially reactive phytotoxins in the soil. 

Hird, A. B., Rimmer, D. L., and Livens, F. R. (1995). Total caesium-fixing potentials of acid organic soils. J. Environ. Radioact. 26, 103-118. 

The ions in the soil solution constitutes the active acidity and are measured directly as soil pH values. On the other hand the adsorbed H+ ions held on exchange sites are not subject to pH measurements are termed as reserve acidity , both the forms contribute to soil acidity. Thus soil pH does not reflect the total acidity. However a suitable index which takes into account the reserve acidity of soil is the lime potential, which is calculated as follows ... 

The present chapter has described the presence of EMF where soil minerals occur and their formation of intimate contact with soil minerals. It seems clear that EMF can dissolve at least some of these minerals when exposed to them in laboratory conditions. Furthermore, EMF obtain large amounts of carbon from their host trees and convert much of it to organic and carbonic acids, making them potentially important in dissolving minerals in natural ecosystems. The main questions for future research are to quantify the contribution of EMF to total weathering of minerals in the soil and to determine whether this contribution will change as a result of more intensively managed forest ecosystems and increased... 

Heterotrophic nitrification has been studied in terrestrial systems, especially acid forest soils, where it has been difficult to document autotrophic nitrification. Experiments using isotopes to differentiate production of N03 from inorganic and organic substrates in a forest system found that heterotrophic nitrification accounted for less than 10% of the total nitrification rate (Barraclough and Puri, 1995). No information of this sort is available on the occurrence or significance of heterotrophic nitrification in aquatic systems. The potential for NH3 and N02 oxidation by heterotrophic bacteria in aquatic systems warrants further exploration, and the capability may be present in many strains already in culture. If heterotrophic nitrification is common in nature, then a focus on autotrophic nitrification as the... 

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