Iowa Secretary of Agriculture Bill Northey shares tips to help producers manage cover crops this spring

As the number of Iowa farmers using cover crops continues to grow, it’s important to help make sure these farmers have a successful experience. Iowa Secretary of Agriculture Bill Northey today shared a number of spring management tips for farmers new to growing cover crops.

Northey also encouraged farmers that are using cover crops to share photos on social media.  The Iowa Department of Agriculture and Land Stewardship will be sharing photos on Facebook and Twitter using the hashtag #FarmersCoverIowa.

“We continue to see significant growth in the number of farmers using cover crops on their farm and also the total acreage of cover crops in the state. With the mild winter and good soil moisture this spring, we are seeing very good cover crop growth and it is a great opportunity for farmers to share why they are using cover crops through social media,” Northey said.  “Farmers using cover crops are seeing the benefits of reduced erosion, improved water quality, and soil health, and even better weed control.  But, spring management decisions remain critical to successful cover cropping.”

It’s important to allow the cover crop to grow as long as possible to maximize the benefits of reducing erosion, improving soil health and helping weed control. This is typically easier for soybeans after winter cover crops because of the later planting date and less potential impact on soybean yields. For corn following a winter cover crop, it’s important to fully terminate a cover crop and provide enough nitrogen at planting. If nitrogen at planting is not possible then plan to terminate a cover crop 10-14 days ahead of planting.  More experienced users may be  comfortable with  termination closer to planting if they are taking additional steps to manage nitrogen.

This information was 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. More information about incorporating cover crops into your farming operation can be found at, or at

1) Evaluate for winter kill – The mild winter, coupled with an early spring has provided near optimal conditions for cover crop growth.  Cover crop species that may normally winter-kill may have over wintered. 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 no green plant material is present then your cover crop winter-killed.  Cover crops such as oilseed radish and oats typically winter kill and then no additional spring management is needed. Other cover crops, such as winter cereal rye, winter wheat and winter triticale consistently over-winters in Iowa.

2) Termination options – Herbicides, tillage or a combination of the two can be used to effectively manage cover crops in the spring.  Keep in mind any tillage will reduce the effectiveness of the cover crop residue to protect against erosion and suppress weeds. Tillage termination could also create more difficult planting scenarios so be sure to check which implement you are using to reduce cash crop plant stands. Some additional considerations for both methods of termination follow:

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 100F. 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.

3) Consider nitrogen needs – 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, nitrogen as the carrier for a weed and feed or some form of available nitrogen over the top will be important to overcoming soil nitrogen that is tied up early in the season.

4) 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 be able to rebound better.

5) 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.

6) 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 5 days of cash crop planting. If using no-till add 7 days to either scenario. More information about insurance requirements can be found at

7) 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. Additional information can be found in the following documents: and

8) Consider participating in the Conservation Technology Information Center’s annual cover crop survey – The Conservation Technology Information Center (CTIC) conducts an annual cover crop survey of all farmers, whether they plant cover crops or not.  Farmers can take the 10-15 minute survey completely anonymously and it helps guide policy, research and education on cover crops nationwide. The survey is available at

“Hopefully these tips and the resources that are available statewide will help farmers have success as they manage their cover crops this spring. We want farmers to have a successful experience and be encouraged to try cover crops again in the future,” Northey said.