The Practical Gardener

Local permaculture guru Chuck Marsh introduced me to the term “biological tillage.” It’s one of those phrases that conveys more than the sum of its parts. It certainly sounds agricultural, and an organic approach is part of it as well. But the part I like best is that it suggests that work is being accomplished on my behalf without any effort on my part.

Worms are the tillers I am speaking of. Darwin wondered “if there are any other animals which have played such an important part in the history of the world.” Aristotle called them the “intestines of the earth,” and there’s no question that worms do remarkable work in turning organic matter into rich “castings,” producing a quantity that matches their own body weight each day.

Something synergistic happens to common organic matter when it gets processed into castings. When it exits a worm’s body, it contains five times as much nitrogen, 11 times as much potassium, and 50 percent more bacteria than would be found in wormless soil. But the double benefit of worms is the tunnels they create as they eat their way through your garden. This is what Chuck Marsh calls biological tillage.

Beneficial micro-organisms are present in healthy soil, but you can’t see them. Worms, though, are the international visual indicator of healthy soil. Who among us has not said: “Wow! Look at those worms!” when digging into healthy soil and uncovering a subterranean habitat teeming with wriggling life. Indeed, it’s what we look for in our soil.

Around here, there are two types of worms. The common night crawler and the typical field worm enjoy cooler temperatures and will often be found at the bottom of the compost pile where there is lots of new compost. The smaller, more active red wigglers and the less lively red worms are very hardy. They can live in the hotter temperatures of semi-active compost piles, and their eggs can be exposed to air. Their eggs are hardy enough, in fact, that they are often shipped frozen to gardeners who want to increase worm populations in their soil. Fortunately for those of us who follow the Way of the Garden, all four types of worms live in healthy soil here in WNC, and they are all mad tillers of the soil.

Both types of worms have the same sort of fantastic body mechanics. An earthworm’s sleek body is well adapted to subterranean travel. Each of its many segments (the continuous rings that make up its body) has four pairs of “setae” — bristly structures that project from the swellings on their bodies and are controlled by muscles. With each movement, the worm extends its body — using its most forward setae to hold fast — alternately releasing its rear setae and allowing the body to pull itself along in a ballet of forward-humping motion. Mucus glands between the segments keep the earthworm’s skin moist.

Worms are also admirably adapted to be tillers of the soil. A powerful muscular gizzard grinds soil and organic matter into finer particles that are digested with the help of symbiotic bacteria and protozoans that live in an earthworm’s gut. Some estimates show that a worm in healthy soil can produce as much as 700 pounds of castings in its lifetime.

Worm castings greatly enhance the quality of soil. They provide refined organic matter and also serve as a highly nutritious plant food.

So how can a gardener make effective use of the tilling capabilities of earthworms? Since I first heard Chuck Marsh talk about this concept about eight years ago at a gardening workshop sponsored by the now-defunct nonprofit MAGIC, I’ve been experimenting with his low-effort, permaculture-based strategies. Using biological tillage to establish high-performance garden beds is much easier than relying on mechanical tillage, though it does take more time. Now’s the time to start new beds, and here’s how to create low-effort garden beds that truly rock.

First, lay out the beds. If they’re veggie beds, you’ll probably want to make them 3 feet by 12 feet. Perennial beds can be any size you want. Lay out the perimeter with a hose, and cut the weeds or grass back to a height of a couple of inches.

Add rock phosphate, greensand and lime at a rate of one coffee can of each per 100 square feet of bed. All of these amendments can be found at local garden shops, and all are critical for adding important base nutrients to your soil. They should be added every other year at the same rate.

Cover the entire area with 2 inches of fresh horse or cow manure, or 4 inches of composted cow manure (which can be purchased in bags). Wet the manure thoroughly.

Cover the whole pile with unwaxed cardboard (you can get it at the recycling center on Riverside Drive). Don’t mess around with the little, flattened-out boxes. Choose big sheets of cardboard — the kind that once covered large appliances. Wet the cardboard to keep it from blowing away.

Cover the wet cardboard with straw or leaves from the municipal leaf dump.

Now you need to relax. Better yet, forget about your garden for a while. Read that mindless novel you’ve been meaning to get to; spend some time with a loved one. You can afford to chill because, while you’re doing so, the little wriggling ones are hard at work attacking the manure hid in the dark beneath the cardboard. The grass and/or weeds that were there before are dying, because the cardboard is blocking out the light; that dying organic matter is becoming food for the worms. And while the worms are homing in on that organic matter from below, they’re also creating a beautiful network of tunnels filled with castings.

Let the worms do their work for at least four months. At this time of year, it might mean leaving the beds alone until next spring. You could possibly get it together earlier, but if you don’t, it doesn’t matter. The cardboard is keeping any weeds at bay, and the bed is in a holding pattern, simply waiting while the worms till the soil as they continue to process the manure.

When you’re ready to plant, don’t use seeds at first. Clear the straw from an area 12 inches in diameter, exposing the half-rotted cardboard. Cut out the cardboard and dig a 15-inch-deep planting hole. Put the soil in a wheelbarrow, mix it with more compost, then return the amended soil to the hole. The soil will be surprisingly easy to work, because the worms have created soil that is saturated with tunnels.

Cut similar holes in the bed 2 feet on center, and plant one plant per hole. With each hole, you’ve just double-dug a small portion of the bed. At the same time, you’ve left the straw and cardboard on the rest of the bed to suppress weeds and mulch the soil around the veggies you’ve just planted.

The second season, dig new planting holes in the undisturbed sections of the bed, and make sure you add straw to the holes that held plants the first year.

By the third season, 80 percent of the bed will have been double-dug. The cardboard will be mostly rotted, and you’ll be able to turn over the soil without a whole lot of effort. The worms will have done a good part of the job for you, and you’ll have done the rest in easy increments. Turn over the whole bed and add more organic matter to further enhance the quality of the soil.

It’s taken a couple of years to get your bed to the point that you can seed directly, but the soil is now fertile and the weeds have been suppressed. And you’re hardly tired from the exertion.