Starting with Cover Crops

 

 

 

 

 

What are Cover Crops?

Cover crops are vigorous growing plants most often seeded for the purpose of protecting bare soil from wind and water erosion, improving soil quality by adding nutrients such as nitrogen and adding organic matter. Cover crops grown to add organic matter are often referred to as green manure crops. But cover crops can provide many other benefits as well. They most often include different types of grasses, legumes and small grains.

According to James J. Hoorman, regional soil health specialist for the Northeast Region of the Natural Resources Conservation Service (NRCS), “In natural systems, live plants cover the soil nearly continuously. In a conventional agricultural cornsoybean crop rotation, the soil only has live plants and roots four months of the year, so this system has less total energy (1/3) to feed the soil organism. A cover crop with live roots increases the soil energy needed to keep the soil ecosystem active and healthy.”

Plants used for cover cropping have the ability to synthesize needed plant nutrients, recycle and make more readily available nutrients already in the soil, add organic matter, provide nourishment for beneficial soil fauna (bacteria, fungi, worms) and increase water absorption. “Nutrient efficiency improves when plants exist on the soil year round,” adds Hoorman.

In addition to enriching the soil, these crops can prevent erosion, reduce compaction, suppress weeds, increase crop yields, filter water, add temporary forage for livestock, and forage and cover for wildlife and pollinators, making them an extremely beneficial part of a habitat improvement plan.

Historically, farmers and gardeners used cover crops for centuries to improve and protect the soil. Modern farmers have become accustomed to the use of commercial fertilizers and other agricultural chemicals having replaced the use of cover crops. With growing environmental concerns in regards to use and overuse of many of these chemicals and the loss of topsoil to erosion, the benefits of a more natural approach such as growing cover crops is experiencing a resurgence. Cover crops have the potential to improve crop yields while reducing the amount of fertilizer needed to obtain good yields.

Success with Cover Crops

To find success using cover crops requires selecting the type and variety that best suit your needs and is adapted to your growing area. Most experienced cover crop growers will tell you to start small. Select small areas in your garden, farm fields or wildlife habitat to experiment with cover crops and the timing of planting that will work for you. While there are a variety of cover crop species that benefit in different ways, there is often no single cover crop that will do everything needed. If this is the case, consider using cover mixes.

Other important factors include the correct timing of seeding, preparing the seedbed and some management. While cover crops don’t require as much attention as a cash crop for them to grow successfully, they do require soil preparation prior to seeding. Over-wintering cover crops must also be terminated to prevent them from acting like weeds or using up nutrients meant for succeeding crops. The cost of seed should also be considered when planning. Simple cereal grains such as rye can be inexpensive while mixes with a variety of seed are more expensive.

When and What to Plant

In most cases, cover crops are planted in either the spring and, more often, in the fall. These two seasons provide the most rainfall, which is critical for good seed germination and growth. But we shouldn’t forget the summer months. Summer covers such as buckwheat, sorgum-sudangrass, peas and sunn hemp can be grown during the warm season with many benefits, and they die down when frost arrives, leaving a protective mulch over the winter. With its rapid growth, about 40 days from seed to bloom in moderate climates, and its profuse flowers loved by pollinators, buckwheat is a super summer cover crop that’s easy to grow.

Fall seeded cover crops help protect the soil from erosion and leaching during the winter months when the soil is often left bare and exposed to the elements. Fall cover crops also have the benefit of providing extra forage for wildlife during the lean months of winter.

 

Over-wintering cover crops, or those that are not killed by freezing temperatures but go dormant, take up extra nutrients at the end of the growing season.

This is called scavenging. These nutrients would otherwise be lost to leaching (when nutrients dissolve in rainwater and drain below the root zone, making the nutrients unavailable to plants). Over-wintering grasses like rye reduce nitrogen leaching by about 70 percent compared to bare soil. These scavenged nutrients are then released during decomposition of the cover crop after it’s been terminateNo $189d in the spring to make room for desired summer crops. After termination, cover crop mulch can reduce weed seedling emergence through the growing season.

The most popular cover crops include cereal grains like rye, oats, wheat, barley, millet and buckwheat. Legumes, which convert atmospheric nitrogen into plant-available nitrogen through nodules on the roots, include clovers, hairy vetch, peas, alfalfa and soybeans. There are grasses such as sorghum sudangrass, milo and Sorghum bicolor. The cereal grains and grasses are fast growing, and seed is less expensive. The legumes are slower growers but are valuable for fixing nitrogen in the soil into a form plants and microorganisms can use. When a legume decomposes, the fixed N nitrogen is released into the soil for use by plants.

Additional crops may include forage turnips, oilseed radishes, canola, lacy phacelia and sunflowers. If your interest is improving wildlife habitat, cover crop mixes are available specifically for use in wildlife habitat improvement and include additional plant varieties that provide supplemental forage for wildlife and cover for resting, nesting and rearing young. Cover crops often provide valuable resources (such as nectar and pollen and over-wintering habitat) for beneficial insects, including pollinators and natural enemies of insect pests.

Cover Mixes

Most cover crops tolerate a variety of soils and climates. Because each cover crop performs differently and provides different benefits, you may want to consider a mixture of two or more species. Mixtures of non-legumes and legumes often combine the benefits of both types of cover crops, and a mix of those that winter-kill and those that are winter hardy and continue to grow in the spring often works well. Because of these multiple benefits, many farmers and gardeners choose to grow a cover crop mix, or cocktail. Combining the fertilizing effects of legumes with the soil-building potential of grasses and grains is often a winning combination.

 

 

No-Till and Cover Crops

Most of us are familiar with the saying, “Out of sight, out of mind.” When it comes to soil health, we tend to think more about what’s happening above ground and not so much what’s going on below. But what’s going on below the surface is just as important, if not more so, when it comes to the health of your soil. There’s a growing block of scientific evidence and support for a no-till farming and gardening method done in conjunction with the use of cover crops.

“Nature does not till, it lets the living roots of plants do the tilling. No-till with cover crops is a way of growing that emulates and mimics nature,” says David Brandt of Walnut Creek Seeds in Carroll, Ohio.

 

Brandt has been farming using no-till and cover crops for almost 50 years. He and his family currently farm about 700 acres in a combination of rotational crops of corn, wheat, soybeans and cover crops. Their land is under continual cover year round. About five years ago, with the increase in interest in the use of cover crops, Brandt began growing, harvesting and selling seeds for cover cropping. “Those farmers that wanted to transition to using cover crops had a hard time finding seed, so we decided to start selling seed,” he says. About 50 percent of their operation is now seed production, and they hope to go to total seed production in the coming years.

It's Alive!

The soil beneath our feet is alive. One teaspoonful of healthy soil contains more organisms than the human population of the earth. Deep tilling destroys this delicate balance of soil life that works in conjunction with plant roots. Keeping the ground covered with plants and avoiding the disturbance of tilling allows mycorrhizal fungus and the many other soil organisms and beneficial relationships to form including the populations of earthworms. Most gardeners know that if a soil has an abundant earthworm population, it is usually rich, healthy and productive soil. The majority of soil microbes are located next to growing roots with 10,000 times more microbes located next to the root than in bare soil. “Plants feed the soil life, and, when the surface is left bare, we’re starving the soil organisms,” says Ann Brandt, David’s daughterin- law. Put simply, the plants feed the soil organisms, and the soil organisms feed the plants, and the plants feed us. Biologically rich soils produce plants that are higher in nutrition and beneficial minerals.

Time to Terminate

Whether a cover crop has to be terminated depends on whether a winter-hardy or a winter-killed crop was planted. A winter-killed cover crop is sensitive to cold temperatures and will be killed, usually by the first hard frost. A winter-hardy cover usually goes dormant as cold temperatures arrive, then begins growing again with warm spring temperatures. Winter-hardy covers need to be terminated to prevent them going to seed and acting like weeds in the following crop. Also, if cover crops are left to grow too long, they begin pulling nutrient and water reserves from the soil that were meant for the next crop. Cover crops should be allowed to grow as long as possible in the spring, but the goal is to terminate the cover crop in time to allow it to decompose, release the nutrients back into the soil, act as a weed suppressing mulch, and let soil moisture rebuild. If pollinator forage is desired from a cover crop, it must be left long enough to flower and not terminated until after peak bloom.

There are a variety of ways in which cover crops can be terminated. To add organic matter or green manure to the soil, cover crops can be shallow tilled. This incorporates the green cover into the topsoil where it can decompose, return nutrients and help hold moisture. Mowing is one of the easiest ways to terminate a cover crop. However, mowing too early can result in the cover crop re-sprouting, requiring it to be mowed again, which can be beneficial if you want to add more biomass. A cover crop can also be grazed with livestock, or baled into hay. Large-scale growers sometimes burn down their cover crop with herbicides in preparation of planting a succeeding crop. Many crops can also be rolled down. Small areas of cover such as garden beds can be cut down by hand with a weed eater, hand sickle or nippers. Ideally, cover crops should be terminated and the soil left for a week or two before planting the next crop.