wood ash for compost?

Asked November 26, 2018, 5:04 PM EST

Currently, I compost coffee grounds and filters, fruit and vegetable waste with enzymes. Can I add our fireplace ash to the mixture?

Ingham County Michigan

3 Responses

Wood ash is highly alkaline (pH usually around 10-13) and can change the pH of the soil and the composition of the bacterial community in the soil. if your soil is fairly acid using compost made with fireplace ash may be beneficial. If it is only slightly acid (pH 6.5) ,neutral (7.0) or already alkaline (above 7.0) adding fireplace ash to your compost may not be such a good idea. 6.5 is close to the optimum pH for growing most vegetables. Get your soil tested to find out what the current pH is and whether applying wood ash amended compost would be a good idea- or not. Wood ash is a significant source of calcium and potassium. As an example of the amount of wood ash used to amend composts, a study done in 2009 to amend tropical acid soils with composts prepared with wood ash found the best results with compost prepared with 8% wood ash. if you do decide to use wood ash- handle it carefully- with protection for your eyes, skin and lungs. It is highly alkaline and can cause burns.

Our "soil" composition is clay. Does that impact the situation? Our lawn becomes waterlogged and is not suitable for growing vegetables. The only things we grow here are grass and flowers in the beds that abut our home.

Clay is the texture of the soil. Adding wood ash, won't change the texture of the soil. Adding compost to the soil increases organic matter, which can help improve the porosity and drainage of the soil. Clay soils can vary in pH. I still suggest that you check the pH of your soil. It may or may not be a benefit to use wood ash in your compost, depending on what the current pH is. Straight wood ash acts much like lime in neutralizing acid soils.