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Composting wood ash  RSS feed

 
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I have a bit of an off the wall question. If I use wood ash as the primary brown layer in a compost, am I making effectively weed-killer compost? I have a lot of wood ash and I've recently learned that you can use ash as an effective weed killer against more difficult to kill invasive species. I'm thinking mixing it in with old gardening soil and scraps would result in a compost I could just smother some blackberry vines with (the low growing kind). Am I right or over thinking it?

Also how long do I wait after applying wood ash as weed killer before I start to neutralize that area in preparation for gardening? I do recognize it would leave behind a lot of salt but I know both that some plants like a higher salt content and that salt can be diluted in soil.
 
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Perry Tart wrote:I have a bit of an off the wall question. If I use wood ash as the primary brown layer in a compost, am I making effectively weed-killer compost? I have a lot of wood ash and I've recently learned that you can use ash as an effective weed killer against more difficult to kill invasive species. I'm thinking mixing it in with old gardening soil and scraps would result in a compost I could just smother some blackberry vines with (the low growing kind). Am I right or over thinking it?

Also how long do I wait after applying wood ash as weed killer before I start to neutralize that area in preparation for gardening? I do recognize it would leave behind a lot of salt but I know both that some plants like a higher salt content and that salt can be diluted in soil.



You cannot compost wood ash, it immediately stops the composting process.

But you should not have a problem with weed seeds anyway if the compost is cooking as it should. High temperatures will kill any weed seeds.

To kill the black berry, you could use sheep, My sheep have succesfully grazed out poison ivy and several patches of raspberries and blackberries. If you do not want to go with sheep, you could go with tillage. Berries typically like their roots protected, so any sunlight on them kills them.

I would think the reason why wood ash is so good at killing weeds is that it makes the soil really alkaloid rendering the soil hard to grow in. That will keep the weeds at bay, but it will also prevent desired plants from growing.

 
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I put some ash into my compost on occasion, it doesn't seem to do much in any direction, enough ash to kill a weed will also kill your plants. I put ash round my berry bushes, around a half spade each, this does NOT kill them or the weeds so I do not see how you could use it as weedkiller without putting it on so thick you would poison the soil for years in that are.
 
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Wood ash contains Lye otherwise known as potassium hydroxide a very strong base. A light sprinkling of ashes will not devastate plants but lay it on even 1/4 inch thick and you are going to change the pH by at least 2.0 full points (eg. a 6.8 becomes an 8.8).
Wood ash can be pre leached by placing it in a container like a trough that is tilted slightly to one end and gently running water through the ashes, this removes the KOH and leaves the other compounds which are not going to be harmful to plants or to compost microorganisms.
 
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