Worm Towers: Vermicomposting directly in the soil


The Living Force
If my impression based on what I've read is accurate, worm castings (poop) are generally the best form of compost for plants (due to high bioavailability and microbial diversity and concentration), and the second best is (ideally thermophilic - "hot") compost made from tree leaves due to the fact that they contain trace minerals drawn from deep in the soil as well as supporting a very diverse and potent microbial culture.

Many people keep worm farms or bins containing compost worms (most commonly "red wrigglers" aka "tiger worms" - species: Eisenia foetida) to which they feed kitchen scraps, and later harvest the castings. The difficulty with this - aside from needing to ensure that the worm habitat is maintained at the right moisture, aeration, and temperatures (mileages vary based on different setups and users) - is that it can be somewhat involved or time consuming to separate the worms from the castings, as they are often mixed together. There are various methods and setups for this shared on youtube. Overall, it has seemed like a lot of additional effort, or at least more than I'd like, which is why I was interested when I learned about "worm towers".

I worm tower is basically a pipe or chute dug down into the soil, with holes drilled in the underground part for worms to move freely in and out. You lay down bedding (like slightly damp shredded paper) first as in a normal worm bin, and then begin adding kitchen scraps at intervals. The worms, if all goes well, will eat the material as it decomposes and then deposit their castings throughout your soil, fertilizing plants at the root level while helping build soil structure, or at least that is the claim. I wonder how much the typical red wriggler composting worms will be interested in crawling through the soil since they are said to prefer the compost-type environment with lots of decaying material. Anyway, the idea is the your worms may survive more easily than in a worm bin because they can retreat into the soil to escape excess heat, cold, moisture, dryness, etc. and then return at their leisure.

So I built one, very basic. Just a few 6 inch by 3/4 inch boards nailed together in a square, with 1 inch holes drilled in the underground part (about a foot). It came up out of the ground about one foot, and I topped it with a flower pot that just happened to nestle in the top perfectly.

Here is the outcome (typed separately and pasted):

My first worm tower was a partial success. My garden contains what seems to be mostly clay soil, maybe some silt.

It did gradually absorb all the veggie scraps I put in (remember that most of the compaction is just water leaching out or evaporating). Not having any red wrigglers and not knowing where to find them, I just dug in the yard near a fruit tree that has fairly good soil underneath from decomposing leaves and found some local worms (yeah, I know they aren't composters, but I figured regular worms with a food source would also improve the garden).

After a while, when the tower was filled with a lot of moist material, a different organism took over on its own: short, fat grub-like grey "worms" with a ridge down either side. Researching, I discovered that they were Soldier Fly larvae, which are actually decent composters in their own right. They apparently have a preference for more moisture than red wrigglers. (As an aside, they can supposedly make a good nutritious chicken feed if you have enough).

At some point before or after the soldier fly larvae moved in, I added some red wrigglers (just a few from a bait package), but I think they died pretty early on for some reason. Some algae or mold formed on the top of the soil where I had added some into dug up soil right next to the tower, and I've never seen any since. Maybe they just couldn't make it thrugh the soil, and the tower might have been too damp for the ones I dropped directly in due to some of the scraps going in.

This year, upon pulling up the tower to inspect the result, it was a bit disappointing in that the bottom of the tower seemed to have basically just filled up with the clay soil. I didn't scoop out the soil to see what it was like further into the tower, but I did find some of those regular soil worms living down there, some in and some out of the tower, so it is a partial success.

For what it's worth, the tomato plant next to the tower was my most successful plant, virtually bug free although it did lose a few lower branches to yellowing (nothing major).

One unfortunate aspect; the wood brought termites up to the surface to feed on it, and they made little dirt tunnels both inside and out side the thing at various times. Eventually they retreated deeper again. Anyone know how to deal with these guys? They're worryingly close to the house. I've done some research about nematodes that prey on termites. If I tackle them aggressively in one go with three different kinds of nematodes (because different nematodes prey on different subterranean termites), I wonder if I could take out the colony. However, I've read that these termites are very difficult to eliminate. Maybe it would be better to just make sure the house is adequately protected (a given either way, really), maybe with the help of a pest control professional or someone with experience.

So, that's that. I would like to make a tower that is not wood in the meantime, but I'm not sure what to use. I'm wary of using any plastics, but I'm considering those long plastic bread storage canisters or something similar and food-grade. Something clay might be neat if I could find it.



The Living Force
Here's a video of Will Allen's set up for growing worms I thought was interesting.



The Living Force
Nancy2feathers said:
Here's a video of Will Allen's set up for growing worms I thought was interesting.

Wow, that is impressive, especially when you watch some of the other videos related to him and what he's accomplishing. It is encouraging to see that in his farm system they are raising fish and animals in addition to the veggie aspect - so often these food movements seem to have a strong vegetarian slant (or so it appears from what little I've seen).

He seems to back up the notion that it is a bit tricky to worm farm on a smaller scale. I would prefer not to have to babysit a bin for temperature and moisture too closely, yet a really large bin doesn't fit my circumstance right now, so a worm tower is an interesting idea that seems to work. I like the idea of having many species of worms. As far as I have seen (and I know there's a whole world down there with who-knows-what that I won't see) we have just one dominant type of worm around here. I'm very curious to find out what specifically this species is, but online resources I've found have been limited.

Another potential option is a hybrid open-bottom system, or to simply inoculate my finished thermal compost with worms which should be able to digest any remaining organic matter and further improve the microbial and nutrient profile. Ideally, compost needs to sit and "cure" for at least a little while anyway after it cools down somewhat. At least, this is my understanding of "best practices" based on what I've read online.
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