Working with Nature to Build Organic Soil, Part 2: Cover Crops

Reader Contribution by Mary Lou Shaw
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In the previous article on Working with Nature, we saw how plants take carbon from the air to create sugars. These carbon-based sugars are feed to soil microbes through root exudates. The microbes then transform the carbons of sugar into organic topsoil. This and the next article discuss how we can work with nature to facilitate this carbon-sequestering and as a result get more nutritious and tasty food.

Prioritize Cover Crops

When we purchased our 13 acre homestead, it included a large potato and tomato garden whose clay soil had been plowed annually by a tractor. Insecticides and fungicides were used routinely and the soil was left bare during the long Ohio winters. As a result of these farming methods, the soil had become compacted and could not absorb much rain during downpours or hold water during hot, dry summers. We saw few earthworms and probably were correct in assuming that the soil’s microbes were largely depleted.

As is often the case, I wish I knew then what I’m learning now! We’ve composted the garden routinely, but I now believe we should have consistently coupled composting with cover crops to bring the garden soil more rapidly back to life. Since using cover crops year-round for the past three years, we’ve seen amazing improvement in the soil’s tilth, an increased number of earthworms, less disease in crops and better control of weeds.

Role of Cover Crops

Keeping soil covered with living plants rapidly improves the health of all soil life and ameliorates climate change. Cover crops;

1. Protect the soil surface from sun and heavy rains, thus serving as mulch

2. Smother weeds

3. Avoid mechanical disturbance of soil

4. Feed soil microbes a diverse diet when a variety of plants are used

5. Leave living roots in the ground for as long as possible to nurture soil microbes

6. Break up soil compaction

7. Transform CO2 into humus, thus slowing down climate change

Suggestions for Types of Cover Crops

The following are the cover crops that I have found most successful in our large garden. The characteristics favor are those that allow me to manage the garden with hand-tools.

For example, I no longer use winter rye despite the fact that it grew well, kept the ground covered all winter, and suppressed weeds. In retrospect, removing it in late spring was quite a comedy routine as I first used the scythe, then the little bush-hog and finally succumbed to using the rototiller. It would be a lovely cover crop for large fields worked with tractors.

The list below is what I would instead recommend for gardeners. You’ll also find excellent categories and suggestions in seed catalogs like “Johnny’s Seed Catalog.”

• Winter season hairy vetch
• Austrian winter peas
• Annual clover
• Sunflowers
• Buckwheat
• Cow peas
• Kale
• Oilseed radishes (like Daikon radishes)
• Turnips

The benefits of cover crops can be increased with certain combinations. For example, annual clover, growing between rows of sweet corn, will fix nitrogen for the corn, smoother weeds and armor the soil. Legumes work synergistically with grasses, so annual clover and oats serve as a “green manure” to enrich the soil.

How to Use Cover Crops

Multiple benefits are derived from cover crops. You might plant them for one reason such as weed suppression, but they also protect the soil, nourish the soil microbes and rapidly build topsoil. The following are ways we use them on our homestead and what benefits I’m aware of:

1. Keep the soil covered. Just as seedlings appear out of nowhere when there is bare soil (we often call these plants weeds), we should mimic nature and keep soil covered. Does your garden lie bare in the winter? Instead plant cold-hardy crops about six weeks ahead of heavy frost. Winter-season hairy vetch or Austrian winter peas are good winter crops. Do you have several weeks between harvesting garlic in summer and planting autumn brassica? Think buckwheat! This fast growing crop will provide nectar for bees, suppress weeds and provide mulch for your autumn crops.

2. Continually enrich your soil by increasing the variety of plants in your garden. The space between brassica and tomato plants can be filled with deeply rooted Daikon radishes or insect-repelling marigolds. The more variety of plants present, the more variety of soil microbes available.

3. Suppress weeds with the “allelopathic” properties of winter rye or sunflowers, depending on the season. Instead of using herbicides, let these plants do the work for you.

4.Use edible cover crops. There’s no reason not to use kale, turnips or radishes between other crops to shade the ground, suppress weeds and to eat!

Cover Crops on Larger Farms

Although I have based these ideas about cover crops mainly my gardening experience, cover crops should be an integral part of larger scale agriculture. Fields left bare in winter result in precious topsoil being lost to wind and water while the soil microbes starve. Cover crops can not only protect the soil, but also provide feed for livestock.

The additional benefit of combining ruminants with forage crops is that when plants are grazed, there is an exponentially increase in their root exudates. This, in turn, greatly increases the amount of topsoil built and the amount of carbon sequestered from the atmosphere.

In the next article, I will discuss two other ways to work with nature to build organic soil—compost and compost tea.

Cattle grazing on crimson clover photo.

Mary Lou Shaw, a retired family practitioner who emphasized preventive medicine, is now homesteading with her husband in Ohio. Besides growing their own food, the pair help preserve genetics and knowledge needed by others to foster rare breeds. They have a large garden and orchard, Dorking chickens, Narragansett turkeys, Dutch Belted cows and bees. Read Mary Lou’s book Growing Local Food, and find all of her MOTHER EARTH NEWS posts here.

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