Webinar highlights cover crop, water quality connections

In case you missed it, this past week’s Iowa Learning Farms webinar offered an excellent overview of the research findings related to the potential of winter cover crops to reduce nitrate leaching in corn and soybean cropping systems. Dr. Tom Kaspar, plant physiologist with the USDA-Agricultural Research Service, shared results from numerous studies that show the ability of cover crops to reduce nitrate concentrations and loads in tile drainage water.

The press headlines about nitrates and water quality are seemingly ubiquitous, and Kaspar provided solid data that help to paint a complete picture of the challenges and opportunities. Our land uses have changed dramatically, and over the past 60-70 years, our cropping systems have likewise changed dramatically with significant reductions in small grains, hay and perennial vegetation.  With corn and soybeans having a 7-month brown gap when they are not actively uptaking nutrients, that leaves a significant amount of time with nutrients vulnerable to leaching.

However, Kaspar’s research clearly demonstrates that cover crops help transition that brown gap to a green gap, providing the ability to “capture” nutrients in the soil that would otherwise be vulnerable to leaching loss. One of Kaspar’s long-term research studies in central Iowa found that rye cover crops in a corn-soybean cropping system reduced nitrate concentrations in tile drainage water by 57%. Additional studies by Kaspar and collaborators around the state found nitrate reductions of anywhere from 20% to 40%. This variability is expected, with different amounts of cover crop growth, weather, rainfall, soil types, tile systems, and field histories.

Kaspar also pointed out that it takes quite some time for nitrate to move through the system – there is a noticeable lag effect.  For instance, Kaspar and collaborators found that nitrate concentrations in subsurface tile drainage continued to decrease through the summer, long after spring cover crop termination.

Check out the full webinar, Lessons Learned from Using Cover Crops to Reduce Losses of Nitrate for 15 Years, on the Iowa Learning Farms webinar archives page.  And to hear more perspectives from Dr. Kaspar, tune in to Episode 06 of the Conservation Chat podcast!

Ann Staudt

Reducing Soil Erosion with Cover Crops: New Infographic

Iowa Learning Farms is pleased to announce the release of a new infographic publication titled Reducing Soil Erosion with Rye Cover Crops.

This visually engaging document highlights one of the biggest benefits of cover crops — the ability to significantly reduce soil erosion. Based upon long-term cover crop work conducted by Korucu, Shipitalo, and Kaspar, colleagues at the USDA-ARS National Laboratory for Agriculture and the Environment here in Ames, this study looks specifically at one of Iowa’s most popular cover crops, winter cereal rye.

The USDA-ARS team conducted in-field simulated rainfall studies on plots with and without cereal rye cover crops, and their findings are powerful in terms of quantifying erosion reduction – 68% less sediment in surface runoff water with a rye cover crop. Further, the amount of surface runoff water decreased, while the amount of water infiltrating was found to increase with the cover crop.

This study was conducted in central Iowa, in the heart of the Des Moines Lobe, on land with a 2% slope. Substantial erosion reductions were found here with rye cover crops — consider the benefits of cover crops to reduce erosion on more sloping lands across the state!

The full infographic is available as a free PDF download on the Iowa Learning Farms website. Clicking on the image below will also take you right there.

Ann Staudt

Cover Cropping on the Lobe

Last evening, a group of 40 area farmers, Soil & Water Conservation District commissioners, and a nice delegation of ISU students from the Ag & Biosystems Engineering department gathered up at Gilmore City, Iowa for a conservation field day hosted by Iowa Learning Farms. Located between Humboldt and Pocahontas, in the heart of the Des Moines Lobe, the Gilmore City research site is home to some of the longest running research in the state on nutrient management and drainage water quality. Last evening’s field day focused on conservation practices that could be utilized in-field (emphasis on cover crops) as well as edge-of-field (bioreactors, saturated buffers, and wetlands).

Kicking things off were father-son duo Bob and Jay Lynch, who farm just outside of Gilmore City. The Lynchs have been long-term ridge tillers, and in recent years, have largely transitioned to strip tillage. In addition, they began integrating cover crops into their corn and soybean operation in 2012, and they have continued to increase cover crop usage since then. With five plus years of cover crop experience under their belts, Bob and Jay shared some words of wisdom and lessons learned with field day attendees.


Benefits of Cover Crops
Bob and Jay Lynch see soil health as the biggest reason to use cover crops. Bob commented, “To see the real benefits of cover crops, you need to go below the ground surface. I go out in my fields where I had rye, and take a shovel out there – the biologicals in the soil are a big deal. I hope I get an earthworm in EVERY handful of my soil! The cover crop roots give them something to eat for much more of the year. In addition to the earthworms, you have all of the other beneficial microbes, too.”

The “feel” of the soil is improved with cover crops, as well. The Lynchs spoke about cover crops giving their soil “a really nice spongey-ness.” The benefits of soil aggregation are there, too, with a cover crop – Bob referenced that the ground would come apart just like cottage cheese with a rye cover crop!

While the Des Moines Lobe is known for its rich, fertile soils, cool temperatures can pose a challenge. The Lynchs commented that cover crops help to moderate soil temperatures, and those results are consistent with data collected from the research plots at Gilmore City, as well.

The Lynchs have also seen some weed suppression benefits with cover crops – when the rye gets knee high in the spring, they’ve seen its potential for blocking out/reducing the abundance of some competing spring weed species.


Fall — Cover Crop Seeding
Aerial application of the rye cover crop has resulted in the best cover crop stand for the Lynchs. They emphasized that fall growth is a function of light availability, so the amount of crop canopy cover will be a big factor with the cover crops starting out.

With adequate moisture, rye cover crops will germinate quickly and begin their fall growth. Here is some emerging rye at the Gilmore City research site, just five days old!


Spring – Cover Crop Termination
With rye and other overwintering cover crop species, spring termination is necessary ahead of planting your row crops. The Lynchs prefer to terminate their rye via chemical in the spring. For the greatest effectiveness, Bob and Jay have found success in separating out herbicide application into two passes – even on the same day — applying glyphosate first to begin the rye termination process, then following with the pre-emergence residual herbicide.

While rolling, roller crimping, and tillage are also possibilities for cover crop termination, they require very particular conditions for success, and as Bob puts it, “It you try to till rye, you’re just making it mad … and then it comes back with a vengeance!”


Spring – Planting into Cover Crop Residue
When rye is growing ahead of corn, the Lynchs presented two options for termination timing: plant your crop the same day you terminate your rye, OR it needs to be dead for 14 days before planting corn.

With abundant cover crop growth, they emphasized that planter settings should definitely be taken into consideration. When planting soybeans into rye residue, the Lynchs recommend that your soybean seeds be planted using similar settings as if you were planting corn. If you use the same bean setting as you would without cover crops, you run an increased risk of the bean seeds sitting on top of the surface.


Management Matters
Bob and Jay concluded, “With cover crops, it all comes down to management. What works with YOUR individual farm?


Wetlands in the Spotlight
The evening field day concluded out at a CREP wetland just a few miles from Gilmore City, sited specifically for nitrate removal. It was a stunning end to the field day as the sun dropped lower and lower on the horizon!  The beauty of the wetland and its ability to benefit water quality clearly piqued people’s interest, as the questions and conversations continued even after the sun went down.

Ann Staudt

Exploring whether cover crop mixtures make sense on Iowa farmland

Last week I had the opportunity to attend the Soil and Water Conservation Society’s 72nd Annual Conference in Madison, Wisconsin.  In addition to attending some great sessions, meeting fellow conservationists, and exploring Madison, I participated in the Conservation Innovation Grant Showcase poster exhibition.  On display were early results from our cover crops mixtures project that began in 2013.


 Some preliminary observations from the study: 

  • Achieved more biomass from the single species (oats or rye) than mixtures
  • Oats and rye resulted in the majority of biomass from the mixtures
  • Cereal rye was the only species to over-winter consistently
  • Generally lower pore water nitrate concentrations following rye and mixture of rye, radish and rapeseed

As we continue to analyze the data collected, the project indicates:

  • Cereal rye and oats establish readily and provide the most biomass growth when seeded on their own.
  • Cover crops can offer some water quality benefits, reducing nitrate concentration in pore water.
  • Rye and oats provide the best biomass return on seed investment! Single Species are the way to go in Iowa for corn and soybean producers.

Be sure to subscribe to our blog and check back for updates on the project, including analysis on crop yields.

Liz Juchems



Cover crop researcher Tom Kaspar receives Spencer Award

Congratulations to our friend and collaborator, Dr. Tom Kaspar, on receiving the Spencer Award for Sustainable Agriculture yesterday!

Long regarded as the grandfather of cover crops here in the state of Iowa, USDA-ARS plant physiologist Tom Kaspar is certainly one of the leading voices on cover crops across the Midwest.  He was one of the “founding fathers” of the Midwest Cover Crops Council, and his collaborative work over the years has investigated and documented the benefits and challenges of cover crops in corn and soybean cropping systems, ranging from impacts on water quality, soil health, nutrient cycling, and more.

We are grateful to Tom for serving as a guest speaker at countless Iowa Learning Farms field days and workshops over the years, sharing his findings with farmers, landowners, and other ag partners across the state. We are also grateful for his efforts in guiding the work of the Iowa Cover Crop Working Group, including our long-term on-farm rye study and our study of earthworms and cover crops.

Kaspar has amassed years of experience investigating not only soil health and cover crops, but also connections with no till, minimum tillage, climatic variations, disease, pathogens, and more. To hear some great perspectives from the man himself, check out Episode 6 of the Conservation Chat podcast, in which host Jackie Comito talks cover crops with Dr. Tom Kaspar.

Kaspar was also featured in our August 2015 Iowa Learning Farms webinar, presenting on Reaching the Full Potential of Cover Crops in Iowa.  Stay tuned to the blog, as well — we’ll be highlighting some of Kaspar’s cover crop findings here in the next week or so.

In the meantime, congratulations to Tom for an honor that is very well deserved!

Ann Staudt


5 Lessons Learned with Rye Cover Crops

Here at Iowa Learning Farms, we’ve been working with cereal rye cover crops since 2008. That’s not nearly as long as our good friend and colleague Tom Kaspar with USDA-ARS, but we can certainly say that, with our partners in the Iowa Cover Crop Working Group, we’ve been exploring and promoting cover crops long before they were cool!

Our longest ongoing study involves the use of cereal rye as a winter cover crop in on-farm trials within corn/soybean cropping systems across the state of Iowa. Over the years, twelve farmers have participated as partners in this project, with each demonstration site featuring field-length replicated strips with a cereal rye cover crop as well as replicated strips without a cereal rye cover crop.


In our eight years of on-farm cover crop demonstrations, what have we learned?  Here are our Top 5 takeaways regarding cereal rye cover crops:

1. Rye cover crops are largely yield neutral.
In the vast majority of this study (55 of 59 site-years), farmers found that a properly managed cereal rye cover crop had little to no negative effect on corn and soybean yields. Soybean yield actually increased in 7 site-years and corn yield increased in 2 site-years. There can be a learning curve up front, but in the long run, this study’s findings dispel the myth that rye negatively impacts crop yields (especially corn yields) in the following season.

2. Cover crops require active management.
Additional considerations/management factors when using a rye cover crop include seeding rate and method in the fall, and then cover crop termination and adjusting planter settings to accommodate additional residue in the spring. In the few cases of this study where crop yields were negatively impacted, farmers identified insufficient cover crop termination and improper planter settings as reasons for the few years where there were crop yield reductions.

3. Spring growth is key to realizing rye’s benefits.
Unlike winter wheat, oats, radishes and turnips, cereal rye survives over winter and continues its growth into the spring months. Large amounts of spring over crop biomass can be produced – variable to location and termination date.

4. Soil health is hard to define and even harder to measure.
Five years into the study, we found no measurable differences in soil health variables (soil organic matter, total carbon, total nitrogen, pH, infiltration and runoff) between the strips with and without the cereal rye cover crop at individual locations. A much greater intensity of sampling and additional time (years) may be required to quantify significant changes. Plus many of Iowa’s soils have relatively high levels of organic matter to begin with, so detecting very small changes can be challenging.

5. Earthworm numbers have increased with a cereal rye cover crop. Looking at the common nightcrawler (Lumbricus terrestris), our 2016 midden count data indicate a statistically significant difference of 38% more earthworms with a cereal rye cover crop. Earthworms can serve as tangible, early biological indicators of soil health.

These findings and more will be highlighted at ISU’s Soil Health Conference coming up later this week. Stop by and see our poster, and let’s talk cover crops – we hope to see you there!

Ann Staudt


Additional information on our work with rye cover crops:

ILF Cover Crop Research webpage
Additional ILF Cover Crop Resources
Earthworms, Cover Crops and Soil Health

The Iowa Cover Crop Working Group is a collaboration of Iowa Learning Farms and the following organizations:

  • Practical Farmers of Iowa
  • Iowa State University Extension and Outreach
  • Iowa Dept. of Agriculture and Land Stewardship
  • USDA-Agricultural Research Service, National Laboratory for Agriculture and the Environment
  • USDA-Natural Resources Conservation Service
  • Midwest Cover Crops Council

Funding for this demonstration project has been provided by Iowa’s State Soil Conservation Committee, Iowa Department of Agriculture and Land Stewardship, Leopold Center for Sustainable Agriculture, Iowa State University Extension Water Quality Program, and NRCS Conservation Innovation Grant 69-6114-15-005.

Earthworms serve as Indicator of Soil Health

A friend of the farmer, gardener, and angler alike, the earthworm may help to unlock the secrets of the soil by serving as an early indicator of soil health!  Anecdotally, farmers have expressed benefits to using cover crops and noted improvements to their soil, but quantifying changes in soil health can be complex to measure (and require years of intensive sampling). That’s where earthworms come into play!

Thanks to funding from a USDA-NRCS Conservation Innovation Grant, the Iowa Learning Farms team is studying the common nightcrawler, Lumbricus terrestris, and investigating its population dynamics in agricultural ecosystems.


In particular, we are conducting midden counts at seven sites across the state (6 on-farm demonstration sites, 1 research site), all managed as a no-till corn/soybean rotation.


Within that system, we are evaluating earthworm populations on side-by-side strips with and without cereal rye cover crops.  Read more about the study in our earlier blog posts Guest Blog: Digging for Worms and Midden Madness.

What have we found?

The midden counts conducted in June 2016 indicate that on each site, strips with a cereal rye cover crop have comparable or higher earthworm counts than those without a cereal rye cover crop …


Looking at all sites together across the board, we see statistically significant differences between the strips with a cereal rye cover crop and those without. Based upon this preliminary data set, we are seeing 38% more earthworm middens with a cereal rye cover crop!


If you’d like to learn more, I just gave a webinar earlier in the week on this topic. The archived webinar can be viewed on the Iowa Learning Farms webinar page (along with all of our previous webinars). Click on the November 16 webinar to view Earthworms and Cover Crops: Unlocking the Secrets in Soil!

Ann Staudt

This material is based upon work supported by the Natural Resources Conservation Service, U.S. Department of Agriculture, under NRCS Conservation Innovation Grant 69-6114-15-005.