By: Brooke Sonnek Extension ANR Intern, Blue Earth & Le Sueur Counties, Shane Bugeja, Extension Educator, Blue Earth & Le Sueur Counties (reviewer), Liz Stahl, Crops Extension Educator (reviewer)
Adding a cover crop into your existing rotation may address some concerns you have about soil health, etc., but it can also bring up important questions. Network with other farmers who are already growing cover crops you are thinking of adding. You can find some at UMN Extension events such as small grains plot tours and the Soil Management Summit. These resources can give you an idea of how a cover crop could fit into your operation. This also applies if you are thinking about planting a newly emerging crop such as Kernza® or winter camelina. Finding out the little things that come with growing experience is valuable when deciding to invest in a new rotation.
Herbicide carryover and toxicity
Additionally, before adding in a cover crop to an established rotation, you must consider herbicide rotational restrictions and potential pest risks, especially in the context of livestock foraging or hay production. There are important restrictions for herbicide carryover and rotational options. Herbicide carryover could result in unexpected injury to a cover crop, and rotational restrictions could render a cover crop unusable as a forage crop, depending on what is stated on the herbicide label. Complicating matters, some cover crops may not be listed on an herbicide label, so the most restrictive limits will need to be followed if you wish to use the cover crop for feed or forage.
If you are using the cover crop for soil health purposes and it will not enter the food or feed market, you can address herbicide carryover concerns by checking the herbicide label (note restrictions for close relatives if the specific crop is not listed), conduct a bioassay, or learn from other growers. Whatever you do, please read the label. If you wish to use the cover crop for feed or forage, you must follow any restrictions listed.
When using a cover crop for forage, also pay attention to nitrate and cyanide poisoning potential especially in drought-stressed areas or after the fall frost as these compounds can seriously harm livestock. In addition, different pests which come along with different crops may require different scouting needs. Some pests could have alternative hosts on other crops in your current rotation or in other fields such as armyworms or fusarium head blight.
Cover crops have been shown to provide soil health benefits, like reduced runoff and increased water infiltration, and they have been shown to provide weed control benefits. Certain cover crops have also been shown to increase pollinator availability which may benefit yields for some crops7.
Soil health case studies from the Minnesota Office of Soil Health demonstrate some real-life instances of producers realizing soil health benefits by using cover crops2-3. Research also supports using certain (and/or longer) cover crop rotations on weeds and insect pests as an effective management tool which interrupts life cycles, which could reduce the need and overall costs of normal herbicide and pesticide applications4-6.
Remember that cover crops can also possibly lead to increased risk of issues with pests such as true armyworm, black cutworm, common stalk borer. This is especially true when they are not terminated in a timely fashion. Scouting for insects, disease, and weed pressure is critical no matter what your rotation is.
Asking these agronomic questions before investing in a cover crop rotation can help you make the best decisions for your current and future operations. Whether you want to improve soil health, increase crop yields, or produce hay for your livestock, expanding your crop rotation can bring ecological benefits to your land and potentially even lower the cost of your operation over time. To set yourself up for success, understand your farm’s priorities and consider what investments are right for your operation before adding a cover crop to your rotation.
Questions to ask when adding a cover crop to your rotation
Cover crops can be used in a crop rotation to improve environmental conditions including soil health attributes. They can also be utilized more like a second cash crop. The University of MN has been developing and testing popular cover crops and developing new ones for farmers to utilize. While there are valid agronomic considerations for including a cover crop in your rotation, before adding them it is important to ask the following questions.Purpose and priorities for your operation
When deciding whether to add a cover crop into your cropping rotation, you should first create a plan and understand the priorities of your operation and ask the question, “why?” Considerations could include:- Soil health/reducing erosion
- Nutrient management/water quality priorities
- Supplemental grazing/hay
- Weed or pest control
Fitting into your existing rotation
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| Kernza® (intermediate wheatgrass) research plot at the University of Minnesota. Photo: Brooke Sonnek |
Herbicide carryover and toxicity
Additionally, before adding in a cover crop to an established rotation, you must consider herbicide rotational restrictions and potential pest risks, especially in the context of livestock foraging or hay production. There are important restrictions for herbicide carryover and rotational options. Herbicide carryover could result in unexpected injury to a cover crop, and rotational restrictions could render a cover crop unusable as a forage crop, depending on what is stated on the herbicide label. Complicating matters, some cover crops may not be listed on an herbicide label, so the most restrictive limits will need to be followed if you wish to use the cover crop for feed or forage.
If you are using the cover crop for soil health purposes and it will not enter the food or feed market, you can address herbicide carryover concerns by checking the herbicide label (note restrictions for close relatives if the specific crop is not listed), conduct a bioassay, or learn from other growers. Whatever you do, please read the label. If you wish to use the cover crop for feed or forage, you must follow any restrictions listed.
When using a cover crop for forage, also pay attention to nitrate and cyanide poisoning potential especially in drought-stressed areas or after the fall frost as these compounds can seriously harm livestock. In addition, different pests which come along with different crops may require different scouting needs. Some pests could have alternative hosts on other crops in your current rotation or in other fields such as armyworms or fusarium head blight.
Equipment considerations
To add a cover crop for feed or forage, you may need to purchase specialized equipment to seed the cover crop or to fence in livestock. Even with some sort of cost-sharing or grant, these costs can be a large investment. You may be able to offset these costs by selling your cover crops as hay, advertising them for pasture, using equipment sharing agreements, or even investing in carbon markets if that is applicable. Still, there really is not any way to sugar-coat that it can (and likely will) increase your input costs when adding a cover crop into the rotation for most farmers. There may also be a lack of technical support due to a much smaller demand for resources due to the small number of growers/grazers in the area. However, many farmers who advocate for cover crops are outspoken about long-term benefits and returns to your land in the long run, which some research supports1.Pests and positive impacts
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| Soybeans were planted into a cereal rye cover crop that was terminated the same day at the Southwest Research and Outreach Center by Lamberton. Photo: Liz Stahl, UMN Extension |
Soil health case studies from the Minnesota Office of Soil Health demonstrate some real-life instances of producers realizing soil health benefits by using cover crops2-3. Research also supports using certain (and/or longer) cover crop rotations on weeds and insect pests as an effective management tool which interrupts life cycles, which could reduce the need and overall costs of normal herbicide and pesticide applications4-6.
Remember that cover crops can also possibly lead to increased risk of issues with pests such as true armyworm, black cutworm, common stalk borer. This is especially true when they are not terminated in a timely fashion. Scouting for insects, disease, and weed pressure is critical no matter what your rotation is.
Market availability for dual use crops
One of the biggest issues when it comes to turning a cover crop into a dual-use crop is market availability. A simple profitable solution as previously mentioned could be to produce hay, straw, or forage for livestock if you have animals or a neighbor that could use the forage or feed. Species such as oats or rye have greater grain marketing opportunities in some areas of Minnesota compared to newer emerging crops—but for the time being, even small grain markets can be underdeveloped and unavailable on the local level. Researchers and corporations are currently working on avenues of market availability for new species such as Kernza® or winter camelina. Employing a dual-use (forage and grain harvest) system could be a viable alternative when expanding your rotation as markets develop.8 Farmers are advised to ensure they have a place to market any new crop being added to the rotation.Crop insurance
Like market availability, cash crop insurance coverage that also includes cover crops can be complicated. This is particularly true if the cover crop is harvested, grazed, or sown during another cash crop’s active growth (such as aerial seeding a cover crop into standing corn). Check with your crop insurance agent well before making any major changes to your rotation to find out what is covered and whether your cover crop would be considered a second cash crop.Asking these agronomic questions before investing in a cover crop rotation can help you make the best decisions for your current and future operations. Whether you want to improve soil health, increase crop yields, or produce hay for your livestock, expanding your crop rotation can bring ecological benefits to your land and potentially even lower the cost of your operation over time. To set yourself up for success, understand your farm’s priorities and consider what investments are right for your operation before adding a cover crop to your rotation.
Additional Resources:
- Midwest Cover Crop Council
- USDA Natural Resources Conservation Service - Minnesota
- Minnesota Soil Health Coalition
- Forever Green Initiative
- Perennial Promise Grower’s Cooperative
- Sustainable Farming Association
- Land Stewardship Project
- Practical Farmers of Iowa - Cover Crops
- USDA Farm Service Agency
- USDA Risk Management Agency
Sources
- Carlson, S., Liu, F., Miguez, F., Sharma, B., Sawadgo, W., Marcillo, G., & Bower, A. (2017). Economic Evaluation of Cover Crops in Midwest Row Crop Farming. Sustainable Agriculture Research and Education. https://projects.sare.org/project-reports/lnc15-375/.
- Luhman, J. (2020). Soil Health Case Studies, Vol. III. Sustainable Farming Association. Retrieved from the University of Minnesota Digital Conservancy, https://hdl.handle.net/11299/216961.
- Butler, M. (2021). Soil Health Case Studies, Vol. IV. University of Minnesota Extension Regional Sustainable Development Partnership. Retrieved from the University of Minnesota Digital Conservancy, https://hdl.handle.net/11299/225216.
- Baraibar, B., Hunter, M. C., Schipanski, M. E., Hamilton, A., & Mortensen, D. A. (2018). Weed Suppression in Cover Crop Monocultures and Mixtures. Weed Science, 66(1), 121–133. https://doi.org/10.1017/wsc.2017.5.
- Gómez, R., Liebman, M., Sundberg, D. N., & Chase, C. A. (2013). Comparison of crop management strategies involving crop genotype and weed management practices in conventional and more diverse cropping systems. Renewable Agriculture and Food Systems, 28(3), 220–233. https://doi.org/10.1017/S1742170512000142
- Zimbric, J. W., Stoltenberg, D. E., & Picasso, V. D. (2020). Effective weed suppression in dual‐use intermediate wheatgrass systems. Agronomy Journal, 112(3), 2164–2175. https://doi.org/10.1002/agj2.20194.
- Bryan, C. J., Sipes, S. D., Arduser, M., Kassim, L., Gibson, D. J., Scott, D. A., & Gage, K. L. (2021). Efficacy of Cover Crops for Pollinator Habitat Provision and Weed Suppression. Environmental Entomology, 50(1), 208–221. https://doi.org/10.1093/ee/nvaa159.
- Hunter, M. C., Sheaffer, C. C., Culman, S. W., Lazarus, W. F., & Jungers, J. M. (2020). Effects of defoliation and row spacing on intermediate wheatgrass II: Forage yield and economics. Agronomy Journal, 112(3), 1862–1880. https://doi.org/10.1002/agj2.20124
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