What to do with cover crops

As the number of Iowa farmers using cover crops continues to grow, it’s important to help make sure farmers have a successful experience. Iowa Secretary of Agriculture Mike Naig today shared a number of spring management tips for farmers using cover crops.  In case you were wondering about benefits, we're reminded that even during the cooler spring weather the roots were always working to prevent erosion and mellow the ground:

Cover Crop Root Mass

This was sent to us by Don, near Danville, Iowa.  That root mass looks pretty substaintial even though the crop isn't very tall.

Rye 1

The advice on what to do from Sec. Naig comes from information put together with the help of the Iowa Cover Crop Working Group, which includes representatives from the Iowa Department of Agriculture and Land Stewardship, Practical Farmers of Iowa, Iowa State University, Iowa Learning Farms and USDA Agriculture Research Service.

  • Evaluate for winter kill – The recent snow cover after some winter cover crop had broken dormancy has provided less than ideal conditions for cover crop growth and survival. Scout your cover crop fields and check the crown of the plant for green plant tissue. Even if the leaves of the plant are brown, double check whether the crown is brown or green. If the above ground cover crop is brown and near the soil surface and no green plant material is present, then your cover crop winter-killed. Cover crops such as oilseed, radish and oats typically winter kill and no additional spring management is needed. Other cover crops, such as winter cereal rye, winter wheat and winter triticale consistently over-winter in Iowa.
  • Termination options – Herbicides, tillage or a combination of the two can be used to effectively manage cover crops in the spring.

Herbicide (Rule of thumb: “Mow the yard once and then get ready to kill your cereal rye. It needs to be growing.”)

For successful herbicide termination, make sure the plant has "greened-up" and has enough living surface area for the herbicide to work. Experienced farmers suggest spraying during the middle of the day and, if possible, spray when day and night time temperatures add up to 100°F. Unless you have experience, separate nitrogen application from a "burndown" herbicide application or be sure not to dilute the herbicide effectiveness with too much nitrogen as the carrier.

Tillage: Terminating cover crops with tillage can be effective, but may take more than one tillage pass. Wet periods can delay tillage to terminate cover crops and wet conditions following tillage can allow cover crop plants to survive tillage operations. Also, tilling a cover crop to terminate eliminates the erosion prevention and potential weed control benefit that the cover crop would usually provide in the early part of the growing season. Lastly if spring tillage is a must make sure to fully bury cover crop root balls that will have dislodged. Double check planter setup to make sure good seed depth is achieved.

  • Consider nitrogen needs for corn – Winter cereal cover crops effectively scavenge nitrogen and reduce soil available nitrogen in the months of late April and May. To protect yield, farmers growing corn after a cereal rye cover crop may want to apply 30-50 lbs of nitrogen at or near corn planting. This is not additional nitrogen, but within the farmer’s total fertilizer program. Options like starter in a 2x2 placement, nitrogen as the carrier for a weed and feed operation or some form of available nitrogen over the top will be important to overcoming soil nitrogen that is tied up early in the season.
  • Planter Setup A field planted after a winter cereal cover crop will be in a different condition than a tilled or no-till field with no cover crop. Evaluate planter setup and make sure to double check that the seed slot/trench is properly closed at planting. An open seed slot can be especially damaging to corn seed while soybean seeds seem to rebound better.
  • Scout Insects – Although rarely an issue, sometimes true armyworm insects can emerge in corn fields following a winter cereal cover crop. These insects can only be treated once emerged. Plan to scout fields of corn where winter cereal cover crops biomass is thick.
  • Know crop insurance requirements – Crop insurance rules state that a cover crop in Zone 3 (western third of Iowa) must be terminated by the day of cash crop planting. A cover crop in Zone 4 (eastern 2/3rds of Iowa) must be terminated within five days of cash crop planting. If using no-till add seven days to either scenario. More information about insurance requirements can be found at www.rma.usda.gov/help/faq/covercrops2016.html.
  • Start planning now for cover crop needs this fall – Determine what cover crop(s) work with your current or planned crop protection program. Some residual herbicides have carryover restrictions for certain species of cover crops. Consult with your agronomist and/or cover crop seed representative to look at your specific management system with the integration of cover crops.
  • Consider assistance that may be available – Farmers should visit their local Soil and Water Conservation District to learn more about financial assistance that may be available. Also, Practical Farmers of Iowa invites farmers who sell soybeans into the ADM supply chain via its Des Moines plant or who sell corn to Cargill via the Eddyville plant to participate in a cover crop cost-share program. Farmers can reserve their place by signing up for a free, non-binding, one-hour phone consultation with a cover crop expert at Practical Farmers of Iowa.


“We understand cover crops are a brand new practice to many farmers and we want them to have a positive experience. Fortunately, there is a wide range of resources available to help farmers successfully manage their cover crops this spring,” Naig said.

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