I am in the midst of preparing the garden for winter. The fact that each year I do it differently demonstrates what an evolutionary process gardening can be.
Forty years ago, I would have been out rototilling and getting rid of the last vestiges of greenery. I quickly learned that rototilling was not for me. I decided that intensively tending raised beds by hand would be more effective and less work than wrestling that blasted rototiller. I had never heard the term “soil quality," but common sense told me that the fine sandy loam in my garden was not in great shape. It fell apart easily in my hands, lacking the cohesive structure of a healthy soil where the myriad forms of life tie soil particles together.
As for getting rid of remnant plant material in the fall, I’ve turned 180 degrees. Now my objective is to keep something growing on the soil as much of the year as possible. When my early lettuce and spinach are done, I immediately plant a cover crop. Where I’m going to plant late carrots, I start with a cover crop as early in the spring as possible. I mulch wherever I can to keep the soil covered. This year, for the first time, I’ve allowed white clover to grow through the summer in various places, experimenting to see if I can manage it to provide nitrogen and soil cover without letting it take over and become a weed. I actually “harvested” it several times through the summer, cutting the tops way back and using that material as mulch.
Keeping the soil covered, whether with living cover crops or mulch of any kind, makes a dramatic difference. I have long decried the fact that wherever I have bare soil, a crust quickly forms on the surface, repelling water. This crust is formed by raindrops hitting the soil, each drop a tiny explosion throwing bits of silt or clay out of the crater. Those particles soon settle into any void they run across, rapidly sealing off those openings and locking out water trying to infiltrate. When a raindrop hits a leaf instead of soil, it loses its destructive velocity, drips harmlessy down to the soil surface, finds an open void, and disappears into the soil where roots can take it up.
My garden is on a slight slope, so the beds are terraced, with the lower sides reinforced by small rocks. Those same beds have been defined for many years, more or less unchanged. I’ve never regretted selling the rototiller and relying instead on a garden fork. And if the soil could speak, I’m sure it would be thanking me profusely. I revel in the experience of sinking the fork deep into the soil one-handed, with almost no effort. Over the last several years I have been experimenting with even less tillage, or no tillage at all, not even with the fork. This is not a new concept. More holistic gardeners than I have been experimenting with no-till gardening for decades.
Gardeners are locked in a constant struggle with weeds. Weed control is a prime motivator for tillage. Organic growers usually substitute tillage for chemical weed control (in the process burning fossil fuels and spewing carbon into the atmosphere). In the short run, that may be necessary, but no-till can be a powerful method of weed control. Tillage brings weed seeds to the surface and any exposed soil becomes a seedbed for new weed seeds. By making sure the soil is always covered, the no-till gardener prevents weed seeds from germinating. And any weeds that do manage to grow are easily pulled from the mellow soil.
I have achieved definite success with no-till for several crops. For instance, at the end of last August I seeded buckwheat as a cover crop in a bed where lettuce was done. It got lush and started to flower before being killed by frost in the fall. Rather than “cleaning it up” by removing the dead plants to the compost pile, I left the soil covered with the dead tops just as they were. In the spring, without doing any tillage at all, I pushed bean seeds into the soil with my finger. They sprouted and grew just fine, their roots developing those magical white nodules that are able to fix nitrogen from the air. I pulled precious few weeds in that bed; none at all in the months since the densely planted beans closed in.
Nitrogen is needed in quantity by all plants and thus is usually the limiting nutrient in the soil. Hence the usefulness of legumes, including peas, beans, and clover. Nitrogen is abundant in the air around us, but not in a form that most plants can use. Bacteria called rhizobia that are hosted by the roots of legumes have the ability to pull nitrogen out of the air and pass it along to the host plant. That nitrogen is used to grow new roots and leaves. When some part of the plant dies, or the leaves fall, the nitrogen in that organic matter is then available to other plants. My white clover experiment depends on my ability to keep the clover cut back. Plants tend to keep their roots and tops in balance, so when I cut back the tops of the clover some portion of the roots also dies. The cut-off tops become mulch and the dead roots become organic matter in the soil, releasing nitrogen (and other nutrients) to the roots of other plants. Over time surface mulch disappears as it rots and is pulled down into the soil by ants, worms, or other creatures.
My career in soil conservation convinced me of the importance of organic matter in soil. It can take many forms according to the type of detritus that is decomposing, but it all performs a host of functions. These days we think of organic matter in terms of carbon and our desire to sequester as much carbon as possible in the soil. Tillage, whether by rototiller or garden fork, releases carbon into the air and thereby reduces soil organic matter.
In my last column, I wrote of the fungal networks that connect trees in undisturbed forest soil. Fungal networks, otherwise known as mycorrhizae, also occur in your garden, but they have a tough time getting established in soil that is repeatedly disturbed by tillage. Just as in the forest, fungi in an undisturbed soil without trees (such as the prairie before the plow) form symbiotic relationships with the plants whose roots penetrate the fungal world. Different species of fungi intertwine with each other and the species of plants around them. Connections are made, nutrients exchanged, and probably some form of chemical communication happens. Knowledge on the subject is sketchy, but it makes sense that certain fungi relate best to certain plants with which they have evolved. As garden soil is tilled, those relationships are literally torn asunder. In a clean tilled garden, fungi have a hard time relating to anything. Even in a holistically managed garden, the plants keep changing as we grow our peas where our lettuce was last year, or marigolds where the tomatoes were, or any of the other rotations we practice. We know so little about fungi that we can only speculate on how best to garden with them.
My garden is covered and ready for the winter. Where no cover crop is growing, I have spread compost, leaving that layer of organic gold on top. And I’ve spread mulch wherever I can over the compost. Through the fall, winter and spring the critters below will pull most of that goodness down where next year’s roots can make good use of it. In April I’ll be back, disturbing as little as possible, making every effort to work in concert with the life in the soil.