My last newsletter spoke about how earthworms are an indicator of good soil health - the more worms, the better - and that excellent soils can have more than 100 worms per shovelful. One subscriber questioned this high number of worms, saying that he had been gardening for 60 years and had never seen that many in his soil. Here is the answer I gave him:
Hello Bob -
You raise a good question. I had gardened for more than 50 years (quite successfully, I might add) before discovering that there was another level of plant health/performance beyond what I had been obtaining. And let me assure you, 100 earthworms per shovelful is not unrealistic - although you don't get there overnight. I just read an article about a farmer who invited his skeptical neighbors to dig anywhere on his property to find more than 150 worms per shovel.
You didn't say how you've been gardening, which makes much more of a difference than how long you've been doing it. Do you rototill? What specific types of fertilizer do you apply? Do you add compost and how much? Do you use mulches and what types? These are all important issues as far as promoting populations of not only worms, but many other beneficial bio-organisms in your soil.
Try an experiment - don't rototill, just scatter a little dry organic fertilizer on top of the soil (I've found the best is fish pellets) and dump a couple large bags of potting soil mulch 4 inches deep and about 18 inches across on one part of your garden next season. Push the mulch aside to seed and/or transplant down the center line. When it comes time to harvest, see how many worms per shovelful are under that mulch layer, and compare the number to the rest of your garden. By providing that sort of constant forage, the worms will rapidly multiply (and the 4 inches of mulch will begin to disappear pretty fast as the worms feed on the bottom of it). Their tunnels and excretions underground will aerate and nourish the plants better than any commercial chemical fertilizer ever could.
As I said, I was surprised by the results after decades of thinking I knew a lot about gardening. Maybe you will be as well.
He said that he will try it next year.
You should note that the key points are to avoid destroying the existing worm tunnels (and killing them) by rototilling, and to provide an always-available source of food with a mulch cover.
I do not recommend blending organic matter directly into soils, as this can create chemistry problems. Also, it is very difficult to find decent compost. Most bagged products are best applied as mulch. As the worms multiply and feed on the decomposing bottom layer of the mulch, they will transport it down to the root zones and deposit it in digested form - an ummmmm treat to plants! The speed at which their populations can increase with mulch-feeding is amazing.
And if you are fighting heavy clay soil, add sand to the mulch cover - maybe a 50-50 mix of clean sand and bagged "compost" or potting soil. The sand will also end up being taken down into the soil to help permanently loosen it. I think this is one of the best and easiest methods of soil improvement - basically just dump stuff on top of the ground and then let huge numbers of worms do the tillage work for you. Push aside the mulch to seed or transplant, and be sure to add more as it disappears (which will happen quicker and quicker).
Larger farming operations will have a greater soil-improvement challenge than will home gardeners or smaller market growers, but employing minimum-tillage, leaving crop residues behind, and strategic use of cover crops can produce improved worm counts even in huge fields. A periodic survey of earthworm populations will show how healthy your soil is - just do a count from ten shovelfuls dug in different spots at the same times each year.
The worms are the visible indicators of soil health - what you won't see are all the billions of beneficial microorganisms that also result from this no-till mulch-cover approach.
Cheers, and good growing,
Don Chapman
President, BioOrganics