Extension Agent, Henry County
Recent environmental and ecological awareness has started a resurgence in cover crop use. Although cover crops have been used for centuries, today's modern farmer has grown up in a generation which has replaced the use of cover crops with widespread use of fertilizers and herbicides. Now as some farmers are trying to use cover crops, they lack the information and experience to be successful. University and private researchers are going back to the basics and are experimenting with beneficial plants to determine how they can best be used in modern farming practices to supplement or replace purchased inputs. Cover crops have an important role in successful sustainable farming systems.
The main purpose of a cover crop is to benefit the soil and/or other crops, but is not intended to be harvested for feed or sale. Some of the primary benefits from cover crops include:
How do farmers get started with cover crops? First, they must determine how their farming system can accommodate cover crops.
Ideally, as soon as one type of crop is utilized (harvested, killed, or incorporated) the next is planted. In this way active plant growth occurs from March to November each year. Look for open periods in each field's rotation where a cover crop can be planted. The Rotation Timeline below illustrates opportunities for using cover crops in a corn, soybean and wheat rotation.
Selection of a cover crop depends on when it can be planted and the goal for its use. There are many cover crop species. Legume cover crops fix atmospheric nitrogen into a form plants and microorganisms can use. Non-legume species recycle existing soil nitrogen and other nutrients and can reduce leaching losses.
|Annual Medic||Forage Turnips|
A combination of 2 or more types of cover crops may be beneficial for quick establishment and improved nutrient utilization.
Seed cost, method of seeding, and method of killing the cover crop should also be considered. Often, farmers are able to grow their own cover crop seed and save on seed costs. Larger seeds, such as hairy vetch and winter peas can be planted through the normal hopper of a drill. Clovers may require a small-seeder attachment. Broadcasting cover crop seed can also be done with a fertilizer cart followed by light incorporation. If a legume is planted that has not been grown before, the proper inoculant should be added when seeding.
There are some drawbacks to using cover crops that farmers should be aware of. If the cover crop does not naturally winter-kill, then a farmer should have a method for killing the crop before it competes with the next cash crop. This can be done mechanically or by using herbicides. Cover crops can act as weeds if not controlled. Timing is important when killing a spring growing cover crop. Cover crops should be allowed to grow as long as possible in the spring to add additional nutrients to the soil and suppress weeds, but they can also use up soil moisture and hurt the following cash crop if dry conditions exist. More management time is required to determine how and when it would be best to control the cover crop. Hard seed that did not germinate may also require control later in the season. Like any other crop, moisture is needed to establish a cover crop. This is especially critical during July and August.
Failures may occur due to late establishment as well. Additional problems may occur if the cover crop harbors armyworm, grubs or cutworms that can attack the cash crop.
The economics of using cover crops can be calculated by the savings of purchased nutrients and herbicides versus the additional cost of using cover crops. There are also other factors that are not easily credited to cover crop use, such as improved soil tilth, enhancing soil biology, and improving organic matter content of the soil. Overall, as the cost of fertilizer and herbicides continue to increase, the benefits of using cover crops in a sustainable farming system will become more attractive to modern farmers. More research is needed to quantify the effects of cover crops so that research based recommendations can be given to producers.
More information on cover crops is available through the World Wide Web. A good source from the University of California Sustainable Agriculture Research and Education Program is located at:
Clark, Andy, 1998. Managing Cover Crops Profitably, Sustainable Agriculture Network.
Harwood, R. et al. 1998. Michigan Field Crop Ecology, Michigan State University Extension Bulletin E-2646.
Magdoff, F. 1998. Building Soils For Better Crops, Northeast Region, Sustainable Agriculture Research and Education (SARE).
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Keith L. Smith, Associate Vice President for Ag. Adm. and Director, OSU Extension.
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