Find out about ash as a soil amendment.
It takes a lot of research looking at ash as part of a compost pile or soil amendment. It's fairly alkaline, so you have to be careful about using much of it directly on soil. Ash is quite variable depending on what the parent material was, how hot it was burned, and for how long. Thus, there are not any really good guidelines except to be moderate. You should use a rule of thumb of no more than 20% ash by volume in your compost pile, and I would probably not use it directly on top of soil. You could, however, put it on top of a wood chip mulch, as the acidity of that mulch would help neutralize the ash alkalinity.
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