I'm trying some different things around the base of some young trees and wonder if anyone knows how to positively influence the earthworm population. My thought is that I would like their presence in order to break-down organic matter and especially to move nutrients around, like phosphorous, boron, and other non-mobile elements. Somewhere I heard that they are happy underneath mints, so one tree has peppermint (and chives) under it; while a couple others are mulched with newspaper and shredded cedar mulch; and yet another has Sedum, wild strawberries, and crimson clover. I thought an organic fertiliser wouldn't harm them, so I used some Plant-tone (5-3-3, with all essential nutrients) last year, and I may buy a 20 lb. bag of Organic Choice garden fertiliser (3-2-3, derived from pasteurised poultry litter) from Miracle-Gro. Any thoughts on other plants or cultural practices to encourage earthworms?
Earthworms love dead organic plant matter. The population of worms will increase in soils that have been augmented with organic matter (both composted and uncomposted) and they really enjoy things like shredded leaves & other soft decaying stuff on the surface. On a still evening, you can hear the crinkling of leaves on the forest floor as the worms pull the plant matter down into the soil. Fertilizers shouldn't harm them too much as long as the application rate is fairly low. Too high and the natural soil fauna are impacted which indirectly impact the worm populations. Simon
Earthworms don't like light. It seems that if you remove light, add organic material, and avoid compaction, they will come. Incorporate used coffee grounds into the soil. Add layers of leaves, dampened newspapers, clean lawn clippings, etc. Aerified, dark, moist (not wet) conditions.
We have an old super productive apple tree and we tend to let its hundreds of apples simply rot right into the surrounding yard (smells like cider by late summer). But the soil in that part of the garden is not only a deep rich brown but it's also FULL of worms. We're talking so many worms that each hand-trowel scoop brings up at least 4-5 if not more. Some small but some huge ones too. And to confirm what yousatonmycactus said, that area's also very shady & rarely used. So, you see, the recipe really does work :)