The experimentIt has been a year since I started composting with worms and I have found it to be very low maintenance... until I want to harvest the vermicompost. I have found that it can take a few hours to pick out the worms in a large bin and move them to a new bin. The best idea that I have found so far to do this is the Turbo Light Harvesting method, but this can still take quite some time. (There are several good videos on YouTube which explains how to do this effectively)
I decided to experiment this summer with an idea that has been kicking around for a while to get the vermicompost into the garden without having to pick out the worms, without just throwing the worms out in the garden. I wanted to try making a couple of small outdoor worm bins that I could bury in the garden. The hope was that even though my garden soil has a lot of clay, as long as there was enough light soil around the bin, the worms would crawl in and out of the bucket and spread their vermicompost naturally with only my adding food scraps occasionally. From what I understand, red wigglers will naturally stay in the upper few inches of soil and compost where they have a food source, unlike the common soil earthworms that will go down several feet and travel longer distances. I didn't think that the worms would travel very far because of the heavy soil nearby.
To make these bins, I took two clean 5 gallon buckets and drilled 3/4 inch holes in the bottom and sides. In order to keep the bins from getting excess water from the garden sprinklers and rain, I kept the original lids on the buckets and only made a few small holes in the lid using a screwdriver to let air escape. I added damp shredded newspaper and cardboard, several handfuls of worms and vermicompost from my overflowing worm bin, and some food scraps. In general, it is best to let a new worm bin age before adding worms, but since I was adding a good portion of the existing bin contents, I took my chances.
In the garden, I dug two holes deep enough to bury the buckets with just the lid exposed. The holes were wide enough to hold the buckets and have about an inch gap all the way around. I added loose soil and compost into this gap.
Three months later...
Now that our summer garden season is over, I wanted to see how these bins turned out. One was at the very edge of the garden and didn't get wet from the sprinkler. The bedding was very dry and most of the newspaper and cardboard was still intact, even though the food scraps were gone. I found few living worms in this bin, so I added enough water to this bin to make sure that any remaining worms wouldn't dry out any more. There didn't seem to be any difference in the nearby garden plants because of this bin. (Apparently I should have been more careful about adding more water and food, especially in the heat of the summer)
The second bucket which was about 10 feet away from the first bucket seemed to be doing quite well. I noticed that during the summer when the garden got flooded, this bucket was completely full of water, but the worms seemed to have survived and most of the bedding was replaced with worm castings. Even though I gave both bins practically no attention during the summer except for the occasional addition of food scraps, one did well and the other dried out. Even so, the one that was doing well didn't seem to contribute much benefit to the surrounding garden plants. I suspect that it is possible for this to work, but this technique probably requires very fluffy soil surrounding the bins. A healthy population of regular garden worms would probably also help to spread the castings from the bins out to the surrounding soil.