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Every year I cold-compost about 4-5 cubic yards of shredded yard waste in a chickenwire-encased cylinder. I aerate every few weeks by forcing air from a leaf blower down a pvc pipe in the center. It works great.
My question is, how long does completed compost last? The only answer I found online was "forever," which seems wrong to me. My amateur guess is that completed compost (or soil) is not a self-contained ecosystem, and that without adding anything more than air and water, it will eventually die and the nutrients will leech out. However, I've found no informed opinions on the matter.
It seems intuitive that for gardening, it is at its peak right after curing; and that gradually (in half-lives?) it loses its benefits.
Actually, if you want to get the best use out of compost, use it when you can get it through 1/4" screen rather than curing. The only think curing is really good for is if you have a thatch problem on your lawn, or you put weed seeds or something in it that you want to pick out of it before you spread it.
I don't know where you got the answer "forever". It is correct, but should have been better explained. Compost continues to be broken down farther and farther and farther to microscopic bits, feeding smaller and smaller creatures in the food chain and supporting plant life. Eventually they are broken down into elements. It's too complex to exlplain this late at night. The bottom line is that nature works in cycles. Since a circle has no beginning and end, they go on forever. In nature, this includes forever changing form, but yes, it goes on forever (not as compost). The hydrogen and oxygen atoms in your water are arguably made up of the same hydrogen and oxygen atoms that were in the water dinosaurs drank. Round and round, the cycles go on forever.
Thanks for responding, but what I wanted to know was how long compost's beneficial gardening properties last. I mean, at some point in process of breaking down into smaller and smaller pieces, isn't it less useful?
Many years ago we got ahold of some old wooden barrel planters. I filled them with compost intending to plant herbs in them, but never did. Those planters sat in our backyard for almost ten years before I decided to use them--but by then, nothing would grow in that soil.