Vermicompost is an excellent source of organic matter and it actually comes from earthworms. Earthworms eat and digest organic matter in the soil and then it is their waste which provides benefits. Earthworm waste, or worm-castings, are an excellent source of nitrogen, phosphorus, and other nutrients, and you can make a very nutritious (for your plants) vermicompost tea to use as a liquid feed and a foliar spray for you plants. Science is still a bit in the early stages of understanding the full benefits of compost and vermicompost teas as foliar sprays, but they do seem to keep some of the foliar diseases at bay.
The nice thing about worms is that they seem to just show up in your compost pile. I think it’s just one of nature’s little miracles. You dump some kitchen scraps in a corner of your yard, add a few leaves, and voila! there they are. And you don’t really have to manage them in anyway after that, except to keep the compost pile nice and moist, which you’d be doing for a good compost heap anyway. As they crawl around to eat they’ll naturally distribute their casting for you throughout the garden or compost pile. They will also overwinter and reproduce on their own so you usually don’t need to continually add worms to your garden or compost pile. They will continue to add fertility to your garden for forever… as long as their population isn’t checked in any way.
That being the case, we need to talk about tilling. Tilling your garden with a mechanical or roto-tiller will kill earthworms. You’re less likely to kill earthworms if you turn the soil by hand with a shovel, but for large gardens that’s hardly practical. And it’s always best to leave the living soil system intact and avoid exposing more weed seeds to light.
If you have a large garden and you just really must till, you can spare as many of your earthworms in two ways: (1) Put a lot of earthworms in perennial gardens such as strawberries, rhubarb, asparagus, blueberries, raspberries, blackberries, fruit trees, etc. and then not worry so much about having a lot earthworms in annual gardens that will be tilled from time to time. In perennial gardens, where the plants live for several years at a time and therefore do not require regular tilling, earthworms can thrive unthreatened. (2) Put earthworms in your compost pile, but not in your garden. Adding vermicompost to the garden from a compost pile still contributes wonderfully while keeping a steady population of earthworms in the compost pile that will not be killed by a roto-tiller. When adding compost or vermicompost to your garden, leave behind a good portion of the pile so that some of the earthworms will also be left behind to continue creating vermicompost and to reproduce and re-colonize the compost pile as you add more compost to it with time.
Okay, I know these two suggestions sound a little ridiculous. That’s because they kind of are. Who is going to try and dig up and move their worms? I’m not. What’s the fastest, easiest solution. Just don’t till. Seriously. Why till at all? It exposes weed seeds (that means more weeds for you to pull this summer), it devastates the living soil system, it practically destroys the worm population (anyone who tells you different is delusional… I hit a worm practically every time I stick a spade in the soil, so I can only imagine what a tiller is going to do.
Some gardeners just feel like they have to till, and they’ll simply have to anticipate a drop in worm population in their gardens from tilling. You can try to replenish the population a bit by buying worms and adding them back to the soil. But that will be another expense to add.
As far as types of worms to get or use: red worms or red wrigglers are the best worms because they’re more active and thus produce more castings. But any earthworm will work just fine. You can dig them up yourself from different areas on your property and put them in your garden, buy them from fish bait shops, or wait to pick them up off the ground after it rains like I used to do as a kid. The best locations finding worms is under rotting plant material like leaves, in a compost pile, or on lawns after it rains.
When you get your worms, simply scatter them evenly by hand across your garden and they’ll bury themselves into your garden on their own. Keep in mind that birds love to eat worms so when adding worms to your garden or compost pile, make sure you standby and guard for a few minutes while your worms crawl under the soil surface, otherwise, you run the risk of creating feeding frenzy of birds that will quickly swoop in and capitalize on an easy meal of worms. If you’ve already put some organic matter in your garden, it’ll make it that much easier for your worms to get into your soil and be safe from predators.