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Cover Up: Cover crops improve soil fertility
by Julie Oudman Perkins - September 2015

If you have the space, planting a cover crop will improve soil fertility and reduce weeds.

What happens below the ground determines the health of plants above the ground. Most gardeners know this and apply fertilizers and compost to their soil during the planting and growing season. But what about throughout late fall, winter, and early spring? A typical garden is bare soil at least half the year, which creates a place of starvation for the good soil organisms needed for healthy plants and nutritive, delicious produce. Cover crops provide a solution to this problem.

Cover crops – also known as “green manure”– are defined by the National Resources Conservation Service (NRCS) as “crops including grasses, legumes, forbs, or other herbaceous plants established for seasonal cover and conservation purposes.” In most cases, farmers are the ones planting cover crops, but home gardeners have begun to take notice of these plants’ benefits as well.

Bruce Shephard poses in his field of crimson clover.

For instance, Bruce Shephard, a retired Nature Conservancy employee, has been vegetable gardening for the past 40 years at his home in Wheatfield, Ind. About three years ago, he started using cover crops in his 6,000 square-foot garden plot. Shephard was introduced to the idea of cover crops by Dan Perkins the certified crop advisor to the Jasper County Soil and Water Conservation District – or the Cover Crop Guy as he’s better known in the agricultural world. (Full disclaimer: I’m married to the “Cover Crop Guy.”) Perkins offers several reasons why cover crops are effective.

• First, they unlock nutrients. Unlike a tomato or pepper plant that’s taking nutrients from the soil in order to provide you with a juicy Brandywine slicer or crisp California Wonder bell, cover crops keep and put nutrients back into the soil. Cover crops are able to hold on to nutrients during the off-season since they work as a slow release fertilizer the following year as the plants and soil need them.

• Cover crops also increase the amount of organic matter in the soil, which in turn makes for a favorable environment for beneficial fungi and microorganisms. For example, the common fungi mycorrhizae can increase the rooting area of your plants by up to 200 percent. Let’s say you have a vegetable garden from May through October. During that time, the mycorrhizae are building up in your soil and benefitting your plants – but what happens at the end of the season? You take out your garden, the soil is bare, the mycorrhizae have nothing to feed on, and you’re starting from scratch again next spring.

• The same principle applies for other beneficial microorganisms. Cover crops provide the food and habitat these fungi need to survive and thrive all year long. Perkins describes it this way, “Cover crops restore a balance to the soil through living roots, which provides food and habitat for the ‘good guys’.” 

Cereal rye forms large masses of roots, which provide food and habitat for beneficial microorganisms.

• Cover crops also decrease disease and weed pressure. A recent three-year study by the University of Illinois showed a 90 percent reduction of rhizoctonia root rot and the lowest levels of septoria brown spot after cereal rye was grown. Shephard experienced a decrease in disease in his favorite variety of early beans. “Every year the beans would get blight real bad. This year – the only time it’s ever happened in 40 years – no blight, thanks to cover crops,” he noted. As for weeds, the most effective and least invasive method of weed control is shade, and a good thick stand of cover crops provides a lot of shade. The list of cover crops’ benefits goes on. Better drainage. Reduced soil erosion. Minimized soil compaction. Increased biodiversity.

So how do you get started using cover crops?

Begin by determining the cycles of your garden. Do you plant mostly summer vegetables? Or do you grow spring and fall plants too? Do you have enough space to keep a fallow plot and rotate your garden?

Shephard, for instance, switches his garden back and forth between plots every other year. In the fallow plot, he grows different varieties of cover crops all year long, while in his garden plot, Shephard uses cover crops for short periods of time between plantings.

Perkins says, “The general goal is to get four weeks of growth on a cover crop before you or cold/warm weather kills it. I say whenever you have an open space and window to plant a cover crop in your garden, then do it.” He suggests four ways to begin using cover crops:

• Plant oats, peas or radishes in early spring (March 15-April 15) if you have bare ground and you’re not going to use that space until summer or fall.

• Plant buckwheat anywhere you have a 30-40 day blank space between May 1-September 1.

• Plants oats and radishes after spring or summer vegetables are done (July 15-Sept 15).

• Plant cereal rye in the fall (Sept 15- Nov 30).

When using cover crops, you not only need to consider when to plant them, but also when and how to kill them. Some gardeners, like Shephard, use Round-up, while others till the cover crops under the soil. If you plant your cover crops in the fall, you may not need to spray or till; cover crops such as oats and radishes “winter kill” or simply die during the cold of winter.

You can purchase cover crops through seed companies such as the Indiana-based Urban Farmer or other seed companies such as Johnny’s and High Mowing Seeds. (If you don’t see a Cover Crop category in the catalog, look under Farm Seed.) Another option – and the one Shephard uses – is to purchase seed from a local grain co-op if there’s one nearby.

Not everyone has the space for a 6,000-square-foot garden. No matter how big or small your garden plot, you can use cover crops and reap the same benefits Shephard has been experiencing. As Perkins likes to say with a smile on his face, “Don’t garden naked. Use cover crops!”

Five Best Cover Crops for the Midwest

Buckwheat is the go-to cover crop for summer seeding between spring and fall crops.  It attracts multiple beneficial insects with its white blossoms. If allowed to go to seed, buckwheat may self sow over a large area of your garden. If tilled into the soil, allow 2-3 weeks for it to breakdown before planting your fall crops.

Cereal rye outperforms all other cover crops in infertile and sandy soil.  It’s the best cover crop for absorbing unused soil nitrogen, which will protect local water quality.

Crimson clover grows rapidly and sends out deep roots.  It does a good job providing nitrogen for the next crop.

Oats are low-cost, reliable, quick-growing, and good in any mix.

Radish, not a salad radish, but a forage/oilseed type that captures a lot of nitrogen and breaks soil compaction. 

Additional Resources


Book: Managing Cover Crops Profitably, 3rd edition – from Sustainable Agriculture Research and Education (SARE) – free download

Cover Crop Guy’s You Tube channel:


A version of this article appeared in print in Chicagoland Gardening Volume XXI Issue V. Photography by Julie Oudman Perkins.



Julie Oudman Perkins and her husband, Dan, are owners of Perkins’ Good Earth Farm in DeMotte, Ind.


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blenderbender - 09/23/2015

Roundup???? To kill cover crops? You are kidding, right?
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Frugal Foodie - 09/24/2015

My thoughts exactly. California is set to list glyphosate (Round Up) as a carcinogen. The World Health Org. already took similar action. Roundup Herbicide Carcinogenic
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