Inorganic reactions
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I just wanted to ask if burning a plant would change the pH of the soil, as in would soil in a burnt forest become more acidic/alkali or remain the same.
The traditional source of potassium fertiliser was wood ash. The source of 'potash'.
Wood ash (potassium hydroxide) and stale urine (ammonia) were the only sources of alkali before industrial chemistry began. Soap makes used wood ash to make soap from fat.
So the answer is that wood ash (burnt plants) contains soluble alkalis. The effect on soil pH depends on the soil. A sandy soil would definitely get more alkaline with wood ash. A very peaty soil might not because of the large amount of organic acids in peat.
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updated: 17 February 2005
