Cover crops have been used for ages to help in agricultural systems, but their use in a garden setting is on the rise as home and commercial vegetable growers realize their value on the smaller scale.
Unlike traditional crops, a cover crop is planted not for its harvest value, but for the enhancement it brings to the garden or soil. These amazing crops have a wide range of benefits depending on which species, or mix of species, is selected.
Globally, cover cropping has been going on for quite some time, with early records dating back to ancient times across Europe, the Middle East and Asia. On this continent, indigenous peoples used cover crops from ancient times to the present. Modern agriculture relied on cover crops as a means to boost soil nutrient levels until they were replaced with synthetic fertilizers in the mid-19th century. For centuries, people have recognized the benefits of these hardworking plants; now it’s time for more gardeners to embrace them.
At a smaller scale, vegetable growers can find the same benefits in their crop rotation by integrating cover crops. They are a relatively cheap way to gain the many benefits offered, and although they do add one more crop to manage each season, they can certainly reduce overall efforts when used effectively, saving time and money.
Perhaps the most sought-after benefit of cover cropping lies in their ability to boost soil health, although there are other paybacks as well depending on which cover crop are selected.
Increases in soil nutrient levels and retention of nutrients are likely the biggest factor driving past cover crop use in modern agriculture. Nitrogen-fixing cover crops, such as crimson clover or hairy vetch, actually increase the available soil nutrients. Beyond cover cropping, these nitrogen-adding plants can also be intercropped among fall plantings of certain vegetables to add nitrogen to soils naturally as the season progresses.
Other crops, such as winter rye, have an enhanced ability to help scavenge or retain nitrogen levels over the winter. The nitrogen cycle is incredibly volatile, with many cropping systems losing significant amounts of nitrogen over winter when fields (or garden beds) are bare. Cover crops that rapidly grow can tie up nitrogen in plant parts to be slowly released as the crop decomposes.
Physical improvements to soil structure are another huge benefit to gardeners since the roots of cover crops break up compaction and loosen soil. In extreme cases, such as with tillage radish, cover crops can dramatically increase water and air exchange deep into the soil profile as large roots decompose over the winter.
Crops with a denser root network that stay in place over winter time can greatly reduce erosion on sloping ground. By maintaining plant cover over winter, the plant canopy itself lessens the impact of rain drops, reducing their ability to dislodge and move soil particles.
Another benefit of dense plant cover is a reduction in weed pressure. Many cover crops work to suppress weeds by physically blocking them out, while certain species (such as winter rye or brassicas) have allelopathic effects, limiting a weed’s ability to grow.
Some cover crops even help with disease suppression as they release chemical compounds that are toxic to soil pathogens and pests. Brassicas and mustard cover crops are most noted for this effect, commonly described as “biofumigants” since their ability to control or suppress nematodes, fungi and some weeds is similar to synthetic soil fumigants. In addition, they are also noted as excellent nutrient scavengers with rapid fall growth and establishment.
If you are interested in the benefits of a fall or winter cover crop, now is the time to start planning. Many fall crops will need to be planted before Oct. 1 in our area to have enough time for establishment prior to freezing conditions, although some winter-hardy crops may be planted as late as November.
For more information on individual cover crop characteristics and planting dates for our area, please see the Selector Tools and other resources developed by the Midwest Cover Crop Council, available at mccc.msu.edu.
Ryan Pankau is horticulture extension educator with University of Illinois Extension serving Champaign, Ford, Iroquois and Vermilion counties.
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