wood ash and the creep crawlies
If you follow the guidelines published by Extension Services, you will not harm soil organisms. There are some studies that indicate some microbial activity is increased with the use of wood ash. References indicate that earthworms prefer a soil pH about 7, and have a range they can tolerate of about 5-8. So, your primary concern is to not raise your pH such that it is higher than what naturally occurs. Too high or low a pH doesn’t benefit plants or the ‘critters’.
MSU Soil lab can test your soil pH, if you haven’t had a lab test recently.
Here is the wood ash recommendation from Penn State Extension
“Wood ashes are sometimes used as fertilizer material. They contain phosphorus, considerable potassium and calcium, and traces of minor elements. In an unleached form (directly from the stove or fireplace), wood ashes can often do more harm than good if not properly applied. The ash is alkaline; it may raise the soil pH to a point at which other elements are unavailable. A good guideline is to apply dry, unleached wood ashes at a maximum of 3 pounds per 100 square feet of soil surface in a single season.”
For more discussion see section 1.1.1 on PDF page 14 in this study-
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