Are Cover Crops a Part of Your Crop Rotation?
by Lyle D. Frees, Natural Resource Specialist
Many Kansas producers are starting to ask the question: Should I consider including a cover crop in my crop rotation? In fact, a few have started to include a cover crop in their farming operation by experimenting on a small acreage. This acreage is away from the nearest road so it does not draw much attention. The use of cover crops is not a new idea. Much of the existing university research was conducted in the 1920s and 30s and is still applicable today.
Most producers will ask why a cover crop should be included in their cropping system and thus use precious soil moisture that is needed for the next cash crop? To answer this, producers need to answer some questions about their cropland’s soil health, soil compaction, and crop diversity.
Is my soil healthy?
In order to answer this question, compare cropland soils with native rangeland soils. Early in the spring and late in the fall cool-season grasses and broadleaf plants thrive while warm-season native grasses and broadleaf plants thrive in the summer months. Good rangeland soils support a vast number of different plants. Dig up a spade full of range soil and observe the extensive root system and the appearance of the soil’s structure. The roots and soil structure appear to be designed to rapidly infiltrate rainfall.
Does my soil suffer from soil compaction?
Unfortunately, most Kansas cropland soils have some level of compaction which can limit infiltration for rainfall. As the size of farming operations increased so has the size of farm equipment. The need to plant and harvest when the cropland soils are too wet to support the larger equipment has resulted in the increased risk of soil compaction. Certain cover crop species can help in reversing the compaction issues.
Does my current crop rotation include a diversity of crop types?
Are the four crop types represented: cool-season grasses and broadleaf plants and warm-season grasses and broadleaf plants? An example of a cool-season grass is winter wheat, and a cool-season broadleaf is canola; a warm-season grass, corn and a warm-season broadleaf, soybeans. Most Kansas crop rotations do not contain all four crop types, and the inclusion of a cover crop can help fill this gap.
Now that you have looked at your soil’s health, compaction, and diversity, the next questions may be what are the benefits of a cover crop and when do you plant a cover crop.
What are the benefits of a cover crop?
The benefits provided by a cover crop are not new and provide many of the same benefits of the cover crops planted by your grandparents. The benefits would include fixing atmospheric nitrogen in soil to be used by the next cash crop, scavenging nitrogen remaining after the previous cash crop, reducing soil compaction, providing wind and water erosion protection, providing livestock forage, and suppressing weeds.
However, the last two benefits need further explanation. The grazing of cover crops by livestock is beneficial to improving soil health as long as some of the cover crop residue remains for the soil microbes to use. A general statement would be to use half of the cover crop for the above-ground livestock and half for the below-ground “livestock” or the microbes. Weed suppression is also a valuable attribute of some cover crop species such as annual rye, barley, buckwheat, or Sudangrass.
A mix of cover crop species can accomplish several of the above benefits. While it is still not completely understood, a mix of six to 12 different cover crop species seeded together can be used to improve soil health while using little or no additional soil moisture. Several crop producers in the Great Plains Region of the United States have documented this finding, and there appears to be no reason why it will not work in Kansas as well. This is of particular importance to the western Kansas producers where limited soil moisture can be a concern.
When should a cover crop be planted?
If you are considering adding a cover crop, the most obvious time to plant a cover crop in a crop rotation is after wheat harvest when the soil is fallow. Planting a cover crop after wheat harvest appears to be the safest time in the crop rotation to plant a cover crop and still have adequate soil moisture for a spring-planted cash crop.
If you want more information on cover crops, many publications are available. No single publication covers all facets of cover crops. To gain a better understanding of cover crops and their uses, the third edition of the book Managing Cover Crops Profitably is a good place to start. It is available free as a download from the Sustainable Agriculture Research and Education (SARE) organization at: http://www.sare.org/Learning-Center/Books.
I would encourage all Kansas producers to consider the use of a cover crop in their current crop rotation.
For more information about cover crops and natural resources conservation, call or stop by your local NRCS office or conservation district office. The office is located at your local U.S. Department of Agriculture (USDA) Service Center (listed in the telephone book under United States Government or on the internet at offices.usda.gov). More information is also available on the Kansas Web site at www.ks.nrcs.usda.gov. Follow us on Twitter @NRCS_Kansas. USDA is an equal opportunity provider and employer.
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Last Modified: 07/20/2012