Cover crops are not just for large, commercial farming operations. Even on small farms and home garden plots, this regenerative technique works wonders on the soil.
In the commercial agricultural realm, cover crops are planted in rotation with the main crop, either before spring planting or after harvest in the fall.
The deal with cover crops
Specific plants, such as Austrian peas, clovers, or vetches, are grown for several reasons, among them to add nutrients to the soil and improve soil structure, then are cut or tilled under before they go to seed.
While this practice might seem challenging for people working with limited space, it is completely feasible.
The trick is to determine which cover crop best suits your garden’s needs. Many cover crops are champions at fixing nitrogen in the soil, reducing erosion, and attracting insect pests away from the main crop (often called trap cropping).
When planted correctly, cover crops are excellent at suppressing weeds. The deep roots on plants such as daikon-type radishes and forage turnips help improve soil texture and reduce compaction.
A number of plants, such as mustards and other brassicas, pull nutrients from the soil and, when they are mowed or turned under, make those nutrients available to the vegetable crop.
Improving the soil with cover crops
Several years ago, I decided to plant cover crops because our soil is heavy clay. No matter how much compost I added, it didn’t seem to improve the soil’s tilth.
When the weather cooperates in our north-central Montana climate, I typically plant fast-growing crops such as mustard, hairy vetch, or ryegrass as early as possible in the spring. They might have only four to six weeks of growth before I turn them into the soil but are able to work their magic.
If there’s too much happening in the spring and I don’t plant the cover crop early enough, I might opt for one that thrives in cooler temperatures—perhaps buckwheat, Austrian peas, or radishes—and plant it after my sugar peas, greens or other early crops are done.
If they’re seeded early enough in the summer, so they begin to flower, I cut them before they go to seed. Or, if it’s later in the season, I simply let the frost stop their growth.
Buckwheat is one of my favorites because it pulls double duty. It grows quickly, creating a fast source of organic material, attracts beneficial insects and our bees love the nectar, which makes their honey dark and rich.
One of the more intriguing ways to incorporate cover crops into your garden is to plant a “living mulch” that grows alongside your vegetables.
Instead of turning it under prior to planting, the cover crop is cut before it seeds, and the cuttings are left in place to act as a mulch while the cover crop continues to grow and creates more organic matter. The result is soil teeming with life.
The appearance of living mulch is a challenge because we are so accustomed to seeing tidy plant-free ground in and around our vegetables. Nature abhors bare ground. When nothing is growing, the soil is vulnerable to wind and water, and its fertility diminishes.
Weeds are Mother Nature’s way of remedying the situation, but planting a cover crop is a better option: It suppresses weeds as it protects soil from erosion and improves its health and our vegetables’ growth potential.
Planting living mulch was one of my gardening experiments this past season. Besides constantly fighting weeds, one of my biggest battles is mitigating water loss, particularly in a season like last year that heated up in early June and remained in record-breaking territory throughout the summer.
Having the cover crops growing in between the vegetables was difficult for me visually (the garden looked messy), but it felt good to drop the tops off the peas, hairy vetch, and ryegrass as a mulch alongside the plants. The cuttings kept the soil cooler, so it retained more moisture.
Living mulch works the best with vegetable plants, not seeded crops. In general, I seeded the entire area with a combination of Austrian peas, hairy vetch, and ryegrass as soon as the weather permitted in the spring.
This included some of the blocks where I eventually planted carrots, beets, beans, or other seeds. I turned under the cover crop where it was going to seed, and some seeds sprouted and outcompeted the tiny plants. For those areas, I’ll stick with fall seeding the cover crop, so the seeded vegetables don’t compete with the cover crop.
Great cover crops to consider
Best planted in the late summer, barley is drought tolerant and does well in poor, even alkaline, soils. Like Austrian peas, it will not survive winter and can be left in the ground until spring.
There are a number of forage or oilseed radishes (Daikon are one type) that are fantastic late-season cover crops. Not only do they provide a considerable amount of biomass, but their large roots also break up compacted soil. When they suffer winter kills, the spaces where their roots exist improve soil filtration. Plant an edible variety if you want to enjoy a few in the fall.
Besides having pretty purple flowers that beneficial insects love, hairy vetch fixes nitrogen in the soil, making it an excellent choice for a living mulch. Cut it while it’s flowering; as long as there is sufficient moisture, it will grow again.
This grass grows quickly and vigorously, adding a substantial amount of biomass to the soil. It grows best in moderate temperatures and is a good choice to plant as part of a living mulch. If left in the ground over winter, it typically dies in colder regions but remains in place, protecting the soil.
This grows quickly and tolerates poor soil. Buckwheat is known to pull phosphorous from the soil, which makes it more available to crops. In most climates, seed buckwheat for a summer crop or during the latter half of the season. Turn it under before it reseeds, for it can grow out of hand.
There are a number of clover varieties used for cover crops, in particular for living mulches, and all fix nitrogen in the soil. Choose the right variety for your specific needs. For example, white clovers tend to tolerate frequent mowing, while crimson clover is usually grown because its flowers encourage pollinators.
These are classic nitrogen-fixers that grow well during cooler periods. Ideally, plant them toward the end of summer. There’s no need to worry about them overstepping their bounds as winter-kill will do the job. Leave them in place until spring.
Besides growing quickly and producing substantial biomass, one interesting aspect of using mustard is that it’s a biofumigant. Brassicas, including mustard, contain sulfur compounds that potentially thwart pathogens, such as fungal diseases.
If you don’t like it in a salad, consider using arugula as a cover crop. It provides plenty of organic matter and shares the biofumigant qualities of mustard. Plant it in the fall and turn it under in the spring at least 10 days prior to planting vegetables.
Living mulch on a larger scale
Utilizing living mulch is a strategy that David, my neighbor, employs to greatly improve soil health. He plants a combination of barley, hairy vetch, and ryegrass between asparagus as well as other vegetables.
David and his family began farming over a decade ago and now raise roughly 18,000 pepper and tomato plants to sell in the spring, along with other vegetable crops.
“We’re trying to build the soil through this biological process. It’s like an ecosystem right on the farm,” says David. “We started off with pretty good soil, but it has definitely improved over the past 11 years.
After spring seeding the cover crop among the 30 rows of asparagus, 300- feet long, David allows the seeds to grow until the plants are roughly 12 to 16 inches tall and flowering, which attracts beneficial insects.
At this point, he mows the rows to break the seeding cycle, then irrigates the field and lets the crop grow back. Depending on the season, he may cut the crop back several times, each time dropping more valuable organic matter on the ground.
For other crops, such as his enormous pumpkin patch, David says, “I like to let the main crop get established before over-seeding with the cover crop to give it a head start and minimize competition from the cover crop.”
David cautions people to pay attention to the amount of cover-crop seed used. “I have found by experience that it’s easy to overdo seeding in the rows. This can lead to competition against the main crop itself. Sometimes, less is more when it comes to overseeding the cover crop into an established crop.”
Hairy vetch is good for the soil and local wildlife. It also has pretty purple flowers. This cover crop, in particular, is a good nitrogen-fixing agent, plus, David says, the deer love it. While most people do everything in their power to dissuade these rodents with hooves, David discovered a way to work with them.
“After the fall harvest, I let the deer into the area,” he says. “They’re going to move in and eat the vetch, and they’re fertilizing our vegetables at the same time.” He notes that the asparagus plants are typically over 6 feet tall, so the deer don’t bother them, and the deer certainly don’t hurt anything in the spent vegetable garden. The result is free fertilizer.
“We’re not going just for the initial crop. We’re growing for a wider perspective,” says David. “We’re seeing great results.” The results are evident when he lifts a shovel full of soil that is teeming with earthworms and has the textbook appearance of soil with perfect tilth.
Like anything in gardening, there is no single correct way to utilize cover crops. There are many that work well, so it’s simply a matter of choosing those that are the most suitable for your garden.
This article was submitted by Jill J. Easton.
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