You probably know that worms are good for the soil. Charles Darwin wrote in his final book that worms “have played a more important part in the history of the world than most persons would at first suppose.” From recycling organic matter into nutrients, to increasing beneficial microorganisms in the soil, worms are essential to a healthy soil food web. But did you know that the best worms for composting are different from those that burrow in your garden?
Redworms for Composting
Redworms Eisenia foetida are the species of worms that are best for composting. These are different from nightcrawlers, which have a deeper burrowing habit that is not suitable for shallow worm boxes. Other species are also sometimes called redworms, but are not as efficient or adapted for life in a worm bin.
Redworms live in decaying organic matter on the surface of the soil, and do not form permanent burrows like other worms. They eat dead organic matter (but not live plants or roots) and soil microorganisms, and digest these into castings that are full of beneficial microorganisms, nutrients, chitin, and plant growth hormones. They can digest up to half their body weight per day. Redworms prefer a dark, moist environment that is free from pesticides. Although they can survive soil or bin temperatures from 32 to 84°F, they are happiest and most active around 68 to 70°F.
Earthworms for Gardening
While you could “plant” redworms in your garden, and will inevitably relocate some worms and eggs every time you use worm castings, redworms are not the best worm species to choose for populating your soil. Earthworms are better suited to the conditions that exist outside of a worm compost bin.
There are hundreds of species of earthworms. These worms will burrow to depths of up to 6 feet, and will drag organic matter into their borrows to eat. Their burrows help aerate the soil, and the organic matter they incorporate into the soil helps improve its structure. Earthworm castings are full of the same beneficial nutrients and microorganisms as redworm castings. Earthworms also excrete mucous from their skins, which additionally helps improve the soil.
You can easily add earthworms to your soil with Vermipods, which are encapsulated earthworm cocoons, each of which contains up to 20 eggs. Give your new worms a good home, and encourage more worms to move in, by keeping the soil moist but not waterlogged, practicing no-till or low-till gardening, and not using harmful chemical fertilizers or pesticides in your garden. Like your vegetables, worms prefer neutral or slightly acidic pH, low salt, with plenty of organic matter such as mulch, compost, and green manure.
Learn more about earthworms from University of Nebraska – Extension.