Corn after a Cereal Rye Cover Crop in 2021

Original Post: Mark Licht , April 2021; Integrated Crop Management News, and Iowa State University Extension and Outreach

With cool weather conditions potentially causing delays in cover crop termination, what options are available? 

Cereal rye ahead of soybean is not nearly as problematic. While planting green may not be advised for beginning cover crop users, more experienced cover crop users have planted soybean into green cereal rye.

There are two main considerations. First, make sure the planter is setup properly for the seedbed conditions. This means making sure row unit down pressure is adequate to ensure proper seed placement depth, and the closing wheels are fully closing the seed furrow. Second, is to terminate the cereal rye soon after soybean planting. I am recommending cereal rye be terminated soon after soybean planting this year because, at present, dry conditions are prevailing across much of the state.

For cereal rye ahead of corn, terminating more than 10 to 14 days ahead of corn planting is preferable. There are reports ‘yellow’ cereal rye can cause wrapping in the residue cleaners. Whatever the termination timing, there will likely be increased implications associated with seedling disease, allelopathy, and nitrogen cycling.

Two recent blogs (blog 1blog 2) from Alison Robertson’s lab tell that temporal and spatial distancing of cereal rye and corn reduced the severity of Pythium seedling infection and mitigated yield loss. Lab studies have also demonstrated that allelochemicals may interact with Pythium to cause more severe seedling disease (Acharya et al. 2021). However, we have a poor understanding of the allelopathic affect in the field. It almost certainly can reduce corn seedling vigor and can be minimized by with more time between cereal rye termination and corn planting. There are also several potential impacts involving nitrogen availability for the corn seedling. We know that cereal rye will take up soil nitrate, and recycle soil nitrogen at some time throughout the growing season. The decomposition of cereal rye immobilizes soil nitrogen in the short-term, and more nitrogen is immobilized if the cereal rye had begun jointing at or before termination.

This year it is likely that corn will be planted green or the termination to planting timeframe will be narrow. Based on our experience, the amount of cereal rye biomass may make a difference. More biomass relates to more severe disease, allelopathy, and nitrogen implications. If the cereal rye is less than 8 inches the risk of nitrogen immobilization and disease infection should be minimal. If the cereal rye is greater than 12 inches consider increasing the corn seeding rate 5 to 10 percent to counteract potential stand loss due to Pythium seedling mortality. All corn seed is treated with fungicides; check your seed label to see what fungicides are on your seed. Mefenoxam, metalaxyl and ethaboxam are fungicides that have excellent efficacy against Pythium. Pyraclostrobin, azoxystrobin and trifloxystrobin also have some activity. Using Priaxor in-furrow could help minimize seedling disease. While Priaxor is labeled for in-furrow applications, there is no public research that we know of that has tested Priaxor under this type of situation. And finally, consider using starter nitrogen and/or applying the remainder of your nitrogen program at an early vegetative stage to ensure sufficient nitrogen supply. Keep in mind that John Sawyer and others have found that corn following cereal rye does not justify a higher nitrogen rate.

Kicking Off the 2021 Conservation Station Outreach Season With Soil and Water Conservation Week!

Happy Soil and Water Conservation Week! The Conservation Station season is just around the corner and our team has been busy getting the fleet ready to roll.

Each of our trailers houses a unique combination of highly visual and interactive Iowa-centric demonstrations that delve into the impacts of land management choices, both urban and agricultural, on water quality and the connections between our state’s water, soil, and wildlife. We are looking forward to the launch of our newest trailer this spring highlighting the importance of wetlands!

The 2021 Conservation Station experience will certainly be different from past years—just as all facets of our lives have changed with COVID-19. Conservation Station team members will wear face coverings and practice physical distancing, as per Iowa State University policy, and will include audio amplification for improved audio accessibility. All Conservation Station activities are being closely evaluated and adapted to ensure that they can be delivered safely and effectively.

We look forward to seeing you this summer at an event near you! The season kicks off on May 1st and we will be updating our calendar for summer events soon, so be sure to check back for updates.

Liz Ripley

To terminate or not to terminate?

Original Post: Bob Hartzler, April 15, 2021; Integrated Crop Management News, and Iowa State University Extension and Outreach

Current cool temperatures increase the risk of failures in terminating cover crops. While cereal rye continues to grow during these conditions, activity of herbicides is reduced. Translocation of glyphosate to growing points is reduced under cool temperatures, slowing activity and increasing the potential for control failures. It is generally recommended to avoid applications when nighttime temperatures fall below 40 F, and we prefer temperatures at application to be at least in the mid-50s with clear skies. Based on current forecasts, herbicide applications to terminate in many areas of the state should be delayed until more favorable conditions exist.

In situations where termination cannot be delayed, the following steps can reduce the risk of control failures:

1) Increase glyphosate rate from what is normally used.
2) Use appropriate rates of AMS and surfactants.
3) Evaluate the potential for tank-mix partners to reduce glyphosate activity such as preemergence herbicides with significant foliar activity. Also, the addition of UAN as a carrier can reduce the absorption and activity of glyphosate.

Successful termination of cover crops is critical due to their competitiveness with crops. Under ideal conditions the effectiveness of glyphosate allows considerable flexibility in application parameters. However, with current cool conditions make appropriate modifications to maximize the likelihood of success. In situations where there is significant survival, delay follow-up treatments until new growth is present. That delay may be more than 1-2 weeks during cool conditions. By the appropriate time for retreatment, temperatures should be favorable for better herbicidal activity.

Glyphosate effectiveness during less than optimum conditions is affected by many factors. In this field the sprayer tracks reduced rye control when applied during cool temperatures.

Congratulations to our Cyclone Soil Health Sweepstakes Winners!

Held during the spring 2021 semester, the Cyclone Soil Health Sweepstakes invited current students at Iowa State University to form a team of creative minds and produce an original 3 – 5 minute video that demonstrates the importance of soil health to a specified audience. The competition allowed teams to apply their soil health studies and take an innovative approach to soil health education and outreach. Be sure to check out their videos using the links below or by visiting our Facebook page.

1st Place: Abbie Van Raden – Senior in Animal Ecology, Kari Jeffrey – Junior in Animal Ecology, and Heather King – Junior in Animal Ecology; ISU Environmental Education Club

2nd Place and People’s Choice: Jacob Schultz – Senior in Agronomy and Meyer Bohn – Graduate Student in Soil Genesis and Morphology; ISU Soil Judging Team

3rd Place: Jacob Handel – Senior in Environmental Science, Robyn Byl – Senior in Agronomy, and Amber Anderson – Graduate Student in Agronomy; ISU Soil Judging Team

Liz Ripley

Algae: The Double-Edged Sword

Mark Rasmussen | Leopold Center for Sustainable Agriculture Director

We humans seem to have an affection and fascination with the color green—the green of money, the green grass of spring after a long winter, the green of a Christmas tree or the expanse of leaves in a deciduous forest.

Photo credit: Iowa Department of Natural Resources Beach Monitoring Program

But there are some forms of green that we look upon with suspicion or have grown to dislike—the green water of an algae bloom or the pond scum that covers the surface of our favorite beach.  We tend to lump different forms of life under the general term “algae” (including cyanobacteria, also referred to as blue-green algae, which are technically not algae at all!), so our relationship with algae can be confusing and somewhat complicated.

As photosynthetic organisms, algae use energy from sunlight to produce oxygen.  Over many eons of time, they are responsible for much of the oxygen in the atmosphere, and they are the original source of fossil carbon transformed deep in the earth into crude oil and natural gas. Algae are also the basis of many food chains in aquatic environments.

We look upon algae with favor when they are used to produce biofuels and nutrient rich dietary supplements. But then there are the “other” algae that are more suspect—blue-green algae.  (Remember, the blue-green algae are technically not algae at all, but early taxonomists used the term and it stuck.)  We especially need to be concerned with the blue-green algae that produce toxins as we enter another growing season here in Iowa.

Cyanobacteria, or blue-green algae, tend to do well in warm, slow-flowing, or stagnant water when both nitrogen and phosphorus are abundant and available. These nutrients, along with sunlight and temperature are the primary drivers of their growth. Some species can grow very rapidly in what is called a bloom.  In a pond they can be part of the natural process of turning a water body eutrophic when dense growth can cause a reduction in animal life due to the absence or limitation of oxygen.  In our agricultural world, blue-green algae growth can be the result of poor nutrient management when high levels of nutrients get into surface waters and stimulate growth.

Along with rapid growth, the production of harmful toxins from certain species of blue-green algae is of great concern. Children and small pets with less body mass are highly susceptible.  The toxins can also impact wildlife when they drink contaminated water.  Dried biomass on shore can also be toxic if inhaled as dust. Research has discovered that people who live or spend a lot of time near contaminated water have a greater risk of health effects just from being near this kind of water.

Toxin production in critical species is also stimulated by increased water temperature.  Therefore, we see more problems later in the summer as bodies of water warm.  Iowa began testing surface water in 2000, and every summer, beach closings and alerts are issued for water that has elevated levels of algae toxins. Climate change and hot summers which warm the water faster also stimulate toxin production and can be expected to increase the problem. 

It is difficult and expensive to purify water for drinking when water sources are contaminated, and most water treatment plants do not have that kind of purification capacity.  Last year the water in the Des Moines River in central Iowa was not useable for many weeks as a primary source due to the high level of toxins contained in the water.  Once contaminated, dilution with cleaner water is about the only solution. 

Given that we can expect this problem to get worse, we must redouble our effort to keep nutrients out of the water.  We can’t control the water temperature nor the hours of sunlight, but we can do something about the nutrient loading in our surface waters.  Unless we do more, we can expect there to be more problems with water quality in Iowa.

Mark Rasmussen

Does Cover Crop Biomass Impact Nitrate Loss Reduction?

To find the right combination of seeding method and date for cover crops for his operation, a farmer in southeast Iowa set up his own demonstration comparing three methods on four dates with 1-2 bushels of rye per acre. He recently shared photos of the cover crops taken April 12-13.

It is clear that the earlier seeded cover crops resulted in significantly more biomass than the November seeding date and that left him wondering if nitrate loss reduction is related to biomass production and if the less expensive method of broadcasting with fertilizer generated enough growth to have an impact on nitrate.

As it turns out, there has been some recent analysis shows nitrate reduction is correlated with cover crop biomass. More biomass – more nitrate reduction. More biomass can also provide weed suppression benefits, especially of early season annuals.

If utilizing a later seeding it is important to consider how long it will grow in the spring. If the cover crop is being used before corn and killed early (10-14 days before planting), there will be limited benefits. However, ahead of soybean there is additional spring growing days that can allow significant growth before that cover crop is terminated, about 7 days before planting for new cover crop users or after planting for more experienced cover crop users.

If you have photos you want to share or questions, email those to and we’ll get them up in our future postings.

-Liz Ripley

Virtual Field Day April 15: Conservation Learning Labs – Exploring the Impact of Cover Crops on Water Quality

Iowa Learning Farms, in partnership with the Iowa Nutrient Research Center, and Conservation Learning Group (CLG), is hosting a free virtual field day discussing spring cover crop management tips and the impact of cover crops on water quality as part of the Conservation Learning Labs project on April 15 at 1 p.m. CDT. Join us for a live discussion with Mark Licht, Iowa State University Assistant Professor and Extension Cropping Systems Specialist, and Matt Helmers, Iowa Nutrient Research Center Director.

Cover crops are one of the key practices of the Iowa Nutrient Reduction Strategy aimed at reducing nutrient losses from the landscape to our rivers and streams. Additionally, cover crops offer a wide range of benefits including reducing soil erosion, improving infiltration and soil health, weed suppression and grazing opportunities. Best management practices for spring management of cover crops are key to maximizing those benefits and reducing potential yield reductions.

The Conservation Learning Labs project, started in 2016, explores the water quality impact of high levels of cover crop and reduced tillage implementation on a small watershed scale. The project focused on watersheds between 500 and 1,300 total acres in size located in Floyd and Story County.  The watersheds have existing Conservation Reserve Enhancement Program (CREP) wetlands that provided baseline water quality monitoring data. The continued monitoring allows for the comparison of water quality before and after conservation practice implementation and to a similarly sized control watershed that did not implement conservation practices.

“Through three years of water quality monitoring we have not seen reduction in nitrate levels in the watersheds with conservation practices implemented possibly due limited growth of cover crops. This is a reason long-term water quality monitoring is critical,” noted Helmers. Be sure to tune into the live discussion for updated monitoring results.

To participate in the live virtual field day at 1:00 pm CDT on April 15 to learn more, click HERE or visit and click “Join Live Virtual Field Day”.

 Or, join from a dial-in phone line:

    Dial: +1 312 626 6799 or +1 646 876 9923

    Meeting ID: 914 1198 4892

The field day will be recorded and archived on the ILF website so that it can be watched at any time. The archive will be available at

Participants may be eligible for a Certified Crop Adviser board-approved continuing education unit (CEU). Information about how to apply to receive the credit (if approved) will be provided at the end of the live field day.

Liz Ripley

Spring Cover Crop Termination Tips & More!

Last spring the Whole Farm Conservation Best Practices Manual was released and offers some great tips for spring management of cover crops – from termination to planter settings and more!

Cover crops that survive the winter, like cereal rye, must be terminated in the spring ahead of planting, to avoid affecting corn and soybean crop yields. There are four methods of termination approved by RMA to fully insure the upcoming corn and soybeans. Their success rate and the confidence in that success is illustrated in the graphic below.

Timing is also an important factor in successful termination.

  • With corn, terminate the cover crop before it is 8 inches tall, and 10 to 14 days before planting corn.
  • With soybean, terminate the cover crop before it is 12 inches tall, and 3 to 7 days before planting soybean.
  • If spring weather conditions are abnormally dry, terminate cover crops earlier than otherwise recommended.

Planting corn or soybean after a cover crop requires minimal change. Follow best management practices for the corn or soybean crop, and the fundamental principles that maximize production efficiency:

  • Plant based on soil conditions, but realize that suitable soil conditions may be a day or two later than without cover crops.
  • Wait for conducive field conditions with a soil temperature at 50ºF and rising. At a soil temperature of 50ºF or warmer, there is robust seed germination, and vigorous seedling emergence, growth, and establishment.

Nitrogen management is also important to consider when corn is following cereal rye.

  • Move nitrogen application to the spring close to the time of corn planting.
  • Starter fertilizers may be beneficial to minimize impact of nitrogen immobilization due to cover crop root and residue decomposition.
  • There is no need to adjust nitrogen rates following winter cereal grain cover crops.

Four more tips for managing cover crops successfully.

Be sure to subscribe to our blog to keep up to date on the latest Cover Crop Corner posts and more great content.

Liz Ripley

Planter Settings Conversation with Nathan Anderson and Keaton Krueger

Are you curious what adjustments to make to your planter to deal with additional residue in a no-till or cover crop system? You’re in luck as the second half of our spring cover crop boot camp featured a great conversation with Nathan Anderson and Keaton Krueger and is now available to watch on demand.

The average planter can be used in a wide range of residue systems with proper adjustments. Here are some recommendations that Nathan shared when making adjustments:

  1. Maintenance is important to make sure everything works properly
  2. Take the time to index the row units – block up gauge wheels to make sure your disc openers are at a consistent height, adjust accordingly
  3. Test adjustments from the cab to see if they are consistent before hitting the field
  4. Use tape and make notes to make consistent adjustments across row units based on their unique quirks

For more great tips and discussion on nutrient applications and herbicide challenges, be sure to watch the full discussion here:

Nathan Anderson runs Bobolink Prairie Farms near Aurelia, Iowa. Nathan, Sarah and their family have grown their cattle herd while improving grazing management and incorporating cover crops. Nathan farms with his father and uncle and using a shared planter he plants cover crops into no-till, strip-till and sometimes worked ground in the spring.

Keaton Krueger farms with his wife, Angela, on her family farm near Ogden, Iowa. They are beginning farmers who currently raise corn and soybeans and have seeded cover crops for the second year this past fall. As a beginning farmer, Keaton currently custom hires his planting and conducts light spring tillage because the planter is not set up for no-till.

-Liz Ripley