Cover Crop Impact on Crop Yield and Water Quality: Single Species vs. Mixtures


Emily Waring

How do single species cover crops compare to mixtures when considering impacts to water quality and crop yield? On Wednesday, Emily Waring, Graduate Research Assistant at Iowa State University, presented results from a research project that has been carried out at six Iowa State University research farms from 2013 – 2018.

The research project compared oats and a mixture of oats, hairy vetch and radish before corn to a control site where no cover crops were used before corn. Before soybeans, the cover crops used were cereal rye and a mixture of cereal rye, rapeseed and radish, which were again compared to a site where no cover crops were used before soybeans.

Waring’s take home messages were:

  • Corn and soybeans are fundamentally “leaky” – cover crops can fill the void in the brown months (before cash crop planting and after cash crop harvest)
  • Nitrate concentrations were significantly reduced with the use of cover crops – with the highest reductions seen when using rye and oats
  • Corn and soybean yields were unaffected by the use of the cover crops
  • Rye and oats provide the best biomass return on seed investment

The research project results show that single species perform well, when when looking at water quality improvement and crop yield. The cover crop species mixtures were more expensive and did not perform better than the single species at reducing nitrate and improving water quality, however Waring stated that there are likely more benefits to diversifying mixtures that aren’t reflected in this study. Future research will look at the soil health benefits of using cover crops and will compare the use of single species vs. mixtures when improving soil health is the goal.

To learn more about the research results, watch the full webinar here.

Join us next month, on Wednesday, June 19 at noon, when Chris Hay, Senior Environmental Scientist at the Iowa Soybean Association, will present an Iowa Learning Farms webinar titled “Drainage Water Recycling: An Emerging Conservation Drainage Practice”.

Hilary Pierce

Are Cattle Really Wrecking the Planet?


Yesterday, Dr. Mark Rasmussen posed the question, “are cattle really wrecking the planet?” during his Iowa Learning Farms webinar. He went on to discuss ruminant nutrition and feeding practices, and how ruminant production can be linked with crop diversity, soil health, climate and sustainable agriculture.


Global atmospheric methane has increased steadily over the last decade, and while there are many sources of methane, ruminant livestock are usually linked to the increase in this greenhouse gas. Ruminants are able to break down coarse forage, such as corn stover or straw, due to microorganisms that live in their gut, but during this process methane is produced. Methane is an energy loss to the host animal, so ruminant nutritionists have been trying to figure out how to capture that energy and reduce the amount of energy lost.

Wolf et al 2017 Global Methane

Figure from Wolf et al. (2017): “Total livestock methane emissions in 2011, downscaled to 0.05 × 0.05° resolution, for the globe (a) and detail for the western US (b)”

Feeding cattle starch, such as corn, will result in the animal growing faster and there will be less methane produced, meaning less energy lost. Researchers have also found that different breeds of cattle produce different amounts of methane and are exploring the possibility of selective breeding to reduce methane production. Recently, better models have been produced that can be used to predict methane production in ruminants. Other research has explored the possibility that ruminants could be a net sink of carbon with proper management and the use of rotational grazing.

If you want to learn more about the effect ruminant nutrition can have on greenhouse gas production and the current research trends, watch the full webinar here.

Join us live for the next Iowa Learning Farms webinar on April 17 at 12:00 pm when Dr. Jerry L. Hatfield (Laboratory Director and Supervisory Plant Physiologist, USDA-National Laboratory for Agriculture and the Environment) will discuss the topic “Why Improving the Soil Will Pay Dividends”.

Hilary Pierce

March 20 Webinar: Are Cattle Really Wrecking the Planet?

ILFHeader(15-year)Join us on Wednesday, March 20th at noon, when Iowa Learning Farms will host a webinar with Dr. Mark Rasmussen, Director of the Leopold Center for Sustainable Agriculture, about the role of livestock in sustainable agriculture.

RasmussenM33This webinar will focus on ruminant nutrition and feeding practices, and how ruminant production can be linked with crop diversity, soil health, climate and sustainable agriculture. Rasmussen will also discuss the strengths and weaknesses of production practices and current economics.

“The role of livestock in sustainable agriculture is misunderstood,” said Rasmussen, whose expertise extends to many areas of agriculture, agricultural microbiology, animal health and nutrition. He hopes that webinar viewers will gain a better understanding of the many benefits of forage-based agriculture.

Don’t miss this webinar!
DATE: Wednesday, March 20, 2019
TIME: 12:00 p.m.
HOW TO PARTICIPATE: and click the link to join the webinar

More information about this webinar is available at our website. If you can’t watch the webinar live, an archived version will be available on our website:

Hilary Pierce

Farmed Prairie Potholes: Consequences & Management Options


Yesterday, during an Iowa Learning Farms webinar, Amy Kaleita discussed current research being carried out at Iowa State University on the hydrology, water quality implications and management options of prairie potholes in Iowa farm fields.

Prairie potholes are enclosed depressions with no natural drainage, until a spill point is reached, that retain water for some portion of the year. Forty-four percent of the Des Moines Lobe drains to potholes and they are a common feature in row crop fields. Potholes are a nuisance to farmers because they are usually the last places in the field to dry out and spring rains can cause ponding in the potholes, which can drown young row crops in as few as 3-5 days (for total yield loss).

feb webinar potholecloudy

Despite efforts to drain potholes using subsurface drainage systems (95-99% of potholes in Iowa are drained), there has been very little research done on the effectiveness of these drainage systems for potholes. In less than ideal conditions, water can actually enter the pothole through the drainage system instead of leaving the depression. Potholes also have water quality implications due to having higher soil nitrate stocks than uplands and studies have shown an increase in dissolved reactive phosphorus concentration in potholes over the course of an inundation event.

Management solutions that are being studied include conservation tillage, retirement of the pothole, planting the pothole with flood tolerant crops and improving pothole drainage. These solutions are being tested using a small watershed model, which is calibrated to reflect the monitored conditions and then changed to reflect the new management practices. Upcoming data results will show the effects of management changes on the studied potholes, some of which are being changed to grass, while others will remain in row crops. 

If you’re interested in learning more about the research being done at Iowa State on prairie potholes in farm fields, you can watch the full webinar here.

Join us live for the next Iowa Learning Farms webinar on March 20 at 12:00 pm when Dr. Mark Rasmussen (Director, Leopold Center) will discuss the topic “Are Cattle Really Wrecking the Planet?”.

Hilary Pierce

February 20 Webinar: Farmed Prairie Potholes – Consequences & Management Options

ILFHeader(15-year)On Wednesday, February 20th at noon Iowa Learning Farms will host a webinar with Dr. Amy Kaleita, Professor of Agricultural & Biosystems Engineering at Iowa State University about the consequences of farming prairie potholes and management options for these common Iowa landscape features.

feb webinar potholeskyIn Iowa, many of the features known as prairie potholes are actively farmed. Because of their position in the landscape and their topographic and soils characteristics, prairie potholes flood frequently after rain events, even with artificial drainage. Kaleita will explain this flooding behavior, and the effects it has on crops and watersheds. She will also discuss options for managing these features to decrease the frequency of negative impacts.

“Some research has shown that farmed prairie potholes lose money more often than they make a profit. Because they also have significant environmental impacts, conservation-minded management of these features may provide benefits at a lower cost than changes in more productive parts of the field,” said Kaleita, whose research on precision conservation focuses on how to use publicly available or low-cost data to improve conservation decision-making within production agriculture.

Don’t miss this webinar!
DATE: Wednesday, February 20, 2019
TIME: 12:00 p.m.
HOW TO PARTICIPATE: and click the link to join the webinar

More information about this webinar is available at our website. If you can’t watch the webinar live, an archived version will be available on our website:

Hilary Pierce

A Conservation Chat with Iowa Secretary of Agriculture Mike Naig

ILFHeader(15-year)Jacqueline Comito| Iowa Learning Farms Program Director

naig_comito_frame_webIowa’s Secretary of Agriculture Mike Naig joined me for a live Conservation Chat as a part of the monthly Iowa Learning Farms (ILF) webinar on January 16. Secretary Naig was elected to office in November 2018, but has been in the role since spring of 2018 when he was appointed to fill the post when Bill Northey was confirmed as the U.S. undersecretary for farm production and conservation.

Mike joined the Iowa Department of Agriculture and Land Stewardship five years ago as deputy secretary. He noted that the opportunity to get involved in the Iowa Nutrient Reduction Strategy from inception was one of the key reasons he moved from the private sector into government.

Mike grew up on a farm in Palo Alto county during the 1980s and saw the farm crisis firsthand. His parents and other farmers of their generation encouraged their children to find careers off the farm – so they would not have to experience the same challenges later in life. Mike took these sentiments to heart and continues to work to help ensure farmers in Iowa have the resources and opportunities to build successful and sustainable businesses.

When asked about his connection to the land, he expressed delight in the broad diversity of landscapes and natural settings across Iowa. He and his family love to explore the outdoors and enjoy everything Iowa has to offer. It also provides an opportunity to teach his three young sons about the importance of our natural resources and conservation.

Mike made it clear that it was time to significantly scale up implementation of the Nutrient Reduction Strategy. He noted “We are five years into implementation of the Nutrient Reduction Strategy. I am proud of what we’ve accomplished, but if we only do the same for the next five years, we will be seriously behind. This is the time to start scaling successful approaches so we can protect, preserve, and promote Iowa’s productivity and its most abundant natural resource – Texas has oil, Iowa has soil.”

We talked about urban and rural mindsets and how to bridge the understanding gap. “Pointing fingers and assigning blame does not move anyone in the right direction. Fostering mutual understanding of the impact any individual can have, regardless of whether they own a quarter acre lot in Ames or a quarter-section plot in northwest Iowa, is crucial to building a culture of conservation statewide.”

With new funding in the current budget year, the Department of Agriculture has hired additional employees to address conservation practices in several major watershed areas. They are also working with private-sector organizations and partners to expand conservation efforts, outreach and education. Iowa Learning Farms and Water Rocks! are examples of partners in conservation and education that help deliver these messages. “We partner and contract with organizations such as Iowa State University to take advantage of the innovation, skilled minds, and advanced research that isn’t available elsewhere. The allow us to do the most with what we have and continue to move toward our goals.”

Mike stressed that farmers needed to look at conservation practices with a broad lens. “You can’t just look at cover crops or tiling or bioreactors and saturated buffers as individual things, you must look at the full scope of improving soil health, employing edge of field practices in combination with tile, and ultimately maintaining or improving productivity and water quality.”

I noted that he had appropriated ILF’s Culture of Conservation tagline during his campaign and asked what that means to him. “It means thinking about conservation as priority. If Iowa wants to continue to be a global production leader, it’s crucial to protect and conserve what makes that leadership possible. And to do it through conservation, not regulation.” Mike agreed that youth education is an important piece of the culture of conservation puzzle, and changing the mindset and approach in Iowa will take a long time and must become inherent to the thinking of current and future generations. “You’re not going to reach everyone right away, just like in marketing any idea or product, there will be early adopters through late adopters. Our challenge is to build out a message to entice and encourage adoption of a lasting change over time.”

More Conservation Chats

Be sure to view the archive visit with Mike Naig on our website.

Our conversation will also be released as a Conservation Chat podcast available at the Conservation Chat website and here on iTunes. New Conservation Chat podcasts will be released every month. February’s Chat will be a conversation with Dr. Matt Helmers, Director of the Iowa Nutrient Research Center and Jamie Benning, Iowa State University Extension and Outreach water quality program manager.

Please join us live for next Iowa Learning Farms Webinar February 20 at 12:00 PM with Dr. Amy Kaleita, Iowa State University professor of agricultural and biosystems engineering. The topic will be: Farmed Prairie Potholes – Consequences and Management Options.


January 16 Webinar – A Conservation Chat with Secretary Naig

ILFHeader(15-year)Wednesday, January 16th at 12:30pm Iowa Learning Farms will kick off our 15th anniversary by hosting a webinar with Iowa Secretary of Agriculture Mike Naig.

Naig_Central Iowa Fair 2018The webinar will feature ILF program manager Dr. Jacqueline Comito and Secretary Naig discussing conservation, water quality and the Secretary’s vision for Iowa.  They will also discuss the Iowa Nutrient Reduction Strategy and how Iowans are working to meet the nitrogen and phosphorus loss reductions outlined in the Strategy. Webinar participants will be able to submit questions for Secretary Naig during the webinar through the Zoom Webinar software.

Don’t miss this webinar!
DATE: Wednesday, January 16, 2019
TIME: 12:30 p.m.
HOW TO PARTICIPATE: and click the link to join the webinar

More information about this webinar is available at our website. If you can’t watch the webinar live, an archived version will be available on our website:

Liz Juchems