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

Do cover crops reduce phosphorus loss?

Cover crops are proven to reduce nitrate loss and decrease soil erosion on our agricultural landscape, but field scale studies on phosphorus loss are still in their infancy. Drs. Antonio Mallarino, Matt Helmers, Rick Cruse, John Sawyer with Iowa State University and Dan Jaynes with National Laboratory for Agriculture and the Environment have completed two years of a long-term field study and have released their preliminary results.

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The Hermann farm site south of Ames allowed Mallarino’s team to observe the effects of cover crops on phosphorus in the runoff study funded by the Iowa Nutrient Research Center.

The study is located at south of Ames on Iowa State’s Hermann Farm. The study includes replication on 12 areas ranging from one to three acres in a field that tested very high in soil phosphorus and is managed with a corn and soybean rotation. The study compares the use of winter cereal rye cover crops with and without tillage.

After two years, Dr. Mallarino observed:

“It is confirmed that cover crops reduce soil loss with tillage or no-till but mainly with tillage. Results also show that with tillage a cover crop reduces phosphorus loss. But it is not so clear that with no-tillage management a cover crop reduces phosphorus loss,” Mallarino said. “With no-tillage, there seems to be a small reduction in particulate phosphorus loss, but an increase in dissolved phosphorus loss.”
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Surface runoff at the testing site is evaluated for total solids and several forms of nutrients.

Why the focus on dissolved phosphorus? The Iowa Nutrient Reduction Strategy is a technical, scientific and voluntary approach to reducing the loss of nitrogen and phosphorus to our waterbodies and the Gulf of Mexico that is home of a large hypoxic or dead zone.  Both particulate and dissolved phosphorus are part of the reduction goal, however dissolved phosphorus is responsible for algae blooms and has a visible impact on aquatic ecosystems.

Caution should be taken when drawing conclusions from only two years of data. Environmental factors play a role in nutrient dynamics with surface runoff, and during the two years of the study, major rain events at the test site had been minimal with very low runoff.

“We can’t make a strong conclusion from these two years of data. There needs to additional data collection from this site and better science-based projecting so we can encourage the addition of cover crops for the right reasons,” Mallarino said.

Click here to read the full article and learn more about project.

Questions about the project contact:

Antonio Mallarino, Agronomy, 515-294-6200, apmallar@iastate.edu

 

Liz Juchems

Can cereal rye cover crops suppress weeds?

A question recently arrived in my email inbox: What is the potential for weed suppression when using cereal rye cover crops?

To help answer the question, I reached out to Dr. Bob Hartzler, ISU Extension Weed Specialist and Professor of Agronomy, and Meaghan Anderson, ISU Extension Field Agronomist.


There is pretty good evidence that a thick, consistent Slide1stand of cereal rye can effectively suppress winter annual weeds.  In soybeans, rye with even cover and a lot of biomass (>4000 lb/ac) may provide some early season weed suppression, but generally the weeds will begin to emerge as the cereal rye breaks down.

Ann and I saw this first hand yesterday (photos below) when visiting our long term rye site in Page County to collection biomass samples. In the cereal rye strips only one or two field pennycress plants were found. However, in the neighboring strips without cover crops, the winter annual weed was thriving.

No evidence yet that cereal rye will help control perennial weeds, but it may help Slide2suppress perennial weeds germinating from seed or perennial rootstalks like dandelion, Canada thistle, field horsetail, etc.  Perennials normally develop from established root structures with a lot more energy reserves, so they are going to be tolerant of the competition from the cover crop.  If repeatedly used, cover crops could provide some suppression of things like dandelion and such.

Whether or not it provides some suppression or control of  resistant weeds would depend on whether those weeds fall into the categories listed above (early-season weeds or winter annuals) and whether the cover crop stand is consistent.

To keep up to date on weed issues, follow Dr. Hartzler on Twitter @ISUWeeds!

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.

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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.
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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.
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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.
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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.

Fields of Green: Fall Cover Crop Biomass Sampling

An unseasonably warm fall has made an excellent year for cover crop growth! The ILF team has been traveling across the state and has seen some beautiful, green cover crop fields. With more growing degree days this fall, it has been a good year for radishes in the southern portions of the state. Check out this growth on radishes at Crawfordsville!

If you have cover crops and are interested in measuring the amount of biomass growing in your fields, follow along with our methodology in this blog. Check out the end of the blog for a summary of how you can apply this research to your own farm.

As part of our National Conservation Innovation Grant/Cover Crop Mixtures demonstration project, we are interested in learning if more biomass can be generated by seeding a single species of cover crop in a plot versus a mixture of cover crop species. To see which treatment yields more biomass (pounds per acre), we collected biomass in the fall and spring from six research sites throughout the state.

To sample biomass, we start with a frame that we constructed out of PVC piping. Our frame measures 19.2 inches x 30 inches (about four square feet). We toss the frame randomly into our test plots. Wherever the frame lands, we sample the cover crop biomass to the soil surface within the frame. We use clippers to cut the cover crop biomass, and we do not include soil, cash crop residues, or weeds in the sample. We try to only capture cover crop biomass and then place it in a labeled paper bag that tells us which test plots the sample came from.

We walk to a different portion of the plot and repeat the process. We always use a different paper bag for each sample and make sure to close the bag after sampling so that sampled biomass cannot escape. We go through the same process in all of our cover crop plots.

We take our biomass samples back to a lab on campus at Iowa State University within the Department of Agricultural and Biosystems Engineering and immediately open the bags the allow them to start air drying. This can prevent sample degradation, like molding on wet samples, from occurring.

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We then sort our samples from each plot by species. For the mixture plots, sorting helps us separate the biomass generated by each cover crop species. For all plots, it ensures that crop residue and other items can be separated from the sample before it is dried and then weighed.

Sorted samples are then placed into their own paper bag and dried in a drying oven at low heat (104 degrees) for at least 48 hours to remove any remaining water. We weigh the samples to get the dry measurement of the biomass. For our demonstration project, the last stop for our samples is the ISU Soil Processing Lab in the Agronomy Department. The samples are analyzed for Total Carbon and Total Nitrogen of the plant.

On-farm Research: If you’re interested in measuring the biomass growing on your own farm, here’s a summary of steps you can follow to make it happen.

Step 1: Create your frame (as long as you know how many square feet are within your frame, the math will work).

Step 2: Take samples in your field and place the samples in separate paper bags. We recommend taking at least eight square feet of samples to get a representative average for the field.

Step 3: Dry the biomass (about 104 degrees for 48 hours). Regional ISU Research Farms may have facilities for you to dry your samples.

Step 4: Calculate total biomass. Weigh the sampled biomass with a scale with two decimal precision (ounce or gram). Also weigh the paper bag by itself.

 

biomass

Average the total biomass from all of your samples to get an average biomass for the field. Convert results to appropriate lbs/acre using unit conversions.  1lb = 16 ounces = 453.592 grams, 1 acre = 43,560 sq. ft.

And finally, always expect surprises! We found a few purple top turnips mixed into our mix of oats, radish, and hairy vetch.

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Julie Whitson

 

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.

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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.

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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 …

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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!

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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.