Asked August 22, 2019, 8:25 AM EDT

Hello, I grow vegetables in my backyard. I do not use any chemicals in my garden soil including any fertilizers, I just use old chicken manure and the compost I make. Although I recycle everything by composting vegetable leftovers, sometime I have to trash them. For example when my tomatoes get the blite or when Beans are infested by viruses I have to dispose all the plants. Can I burn these -using a simple outdoor fireplace- and then use the ash in the garden? Is the ash beneficial to the soil? How/How much/When do I add the ash to the soil? What about half burned plants that look like charcoal, can these be used too? Thanks.

Montgomery County Maryland

3 Responses

Yes, you can use the ash of plants, including diseased plants. See page 7 of this pub:

As long as infected/infested plants are burned/scorched and do not show green, they should be safe to compost or recycle. in your garden.


Thanks for the info. Looking at PDF, all I see is this part:"Wood ashes*: analyses run from 1 to 2% phosphorus and from 4 to 10% potassium. Hardwood ashes are 45% carbonate equivalent and are half as effective as lime for raising soil pH. Softwood ashes are less effective than hardwood. Ashes are too fine to improve soil structure. The recommended yearly application rate is 25-50 lbs./1,000 sq. ft. At higher rates, test soil pH yearly.".

Per PDF, Ash would not improve soil structure and will lower the PH so maybe I use the ash in my compost?

Please advise.

Hi- that's correct, ashes do not improve soil structure. They add a small amount of nutrients and can potentially increase soil pH. Adding ash to the compost pile will not improve compost quality. Since the compost is presumably going to be applied to the garden soil it really doesn't matter where you apply it (soil or compost pile), especially since it's a relatively small amount.