GEOG 317 Lecture Notes - Ph Meter, Soil Ph, Humus
16 Dec 2012
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Document Summary
Soil ph controls the environment of microorganisms and plants ph is a measure of the concentration of h+ and oh- ions in soil solution. Under 6, more than 50% of h+ is acidic- , alkaline is oh-, over 8. 1 unit change in ph means 10 times change in h+ or oh-, if less than 7 then increase in h, if more than 7 then change increase in oh. At ph of less than 5, al ions become soluble. Aluminum ions are released into soil during mineral weathering: Active acidity- due to h+ and al3+ ions in soil solution. Exchangeable acidity- exchangeable h and al ions on exchange sites. Residual acidity- associated with h and al ions that are bound (non exchangeable) on soil particles (clays+humus) Acid forming factors organic matter decomp- organic and inorganic acids are formed. Sulfuric and nitric acids formed in atmosphere from combustion of coal gas and other fossil fules.
