Conservation Chat 38: Go Deep with Earthworms

WebEpisode 38 of the Conservation Chat digs in deep to talk about earthworms, why they matter, where they thrive and what they can tell us about soil health. The chat features two heavy-hitters of earthworm research related to cover crops: Ann Staudt who leads research on the relationship between night crawlers and cover crops with the Iowa Learning Farms and Dr. Tom Kaspar, a plant physiologist who is also considered to be “the grandfather of cover crop research” in Iowa.

To study earthworms, you must be able to count them. In the earthworm literature, there are four common ways that researchers have approached the counting of earthworms:

  1. Excavate an area of soil to find and count the earthworms
  2. Use a mustard solution or wasabi to chemically extract the earthworms, drawing them to the surface
  3. Apply an electrical current to the soil surface and electrically extract the earthworms, drawing them to the surface
  4. Count middens (well-defined clumpy mounds that an earthworm leaves behind on the soil surface). This is the only method of counting earthworms in which earthworms are not harmed!

Iowa Learning Farms took the latter route and decided to count middens (pictured on the left). Ann Staudt wanted to study whether there were observable differences in the population of nightcrawlers (a type of earthworm) in corn and soybean fields with and without a cereal rye cover crop. The research was completed in fields that had side-by-side cover crop and no cover crop strips. The research found that there were 38% more nightcrawlers in the strips that contained cover crops!

Results

RyeThis research is unique, as very little research has been done about earthworm populations within corn and soybean systems. And, there is much more research that can be done related to earthworms in a corn and soybean system. Future research could include looking at cover crop growth related to earthworm populations, how earthworm populations may respond to different types of cover crop species and mixes, and even nutrient ability in a crop field related to earthworm tunnels, which some literature cites as “hot spots of nutrients.”

The podcast gets down to the heart of why earthworms matter. We often talk about why soil health is important, but it can take many years to detect indicators of soil health with current tests and methods. Ann Staudt suggests that earthworms may be a “reverse canary in the coal mine” for soil health:

“In some ways, it’s like a reverse canary in the coal mine. It’s showing us some of the positive benefits perhaps earlier than we’re seeing it in a lot of the other parameters that we’re trying to measure.”

There is one particularly unique benefit of earthworms that is not commonly considered. Dr. Kaspar explains:

“In [a no-till system], earthworms are basically tilling the soil for you. They’re creating these burrows or holes . . . the nightcrawler in particular is the only worm that produces a relatively vertical hole that goes from the surface down as deep as five or six feet, depending on the soil. . . Those holes allow water and air to enter the soil, which is really important and they provide a pathway for roots to go deeper into the soil.”

This last point is particularly important in a corn and soybean cropping system with tight spacing between plants. In order for crop roots to grow and have a greater ability to access water and available nutrients deeper into the soil profile, they must grow down. Earthworm tunnels can help crop roots do just that.

Listen to the most recent episode of the Conservation Chat with Ann Staudt and Dr. Tom Kaspar! You can now listen in a variety of ways:

Like the podcast? You can help us out by sharing with a friend! Do you agree that earthworms could be a mascot for life in our soil?

Julie Winter

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.

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.

Midden Madness

The Faroe Islands honored the common earthworm, Lumbricus terrestris, on its postage stamp!

The Faroe Islands honored the common earthworm, Lumbricus terrestris, on its postage stamp!

Between collecting water samples, soil samples, and cover crop biomass, our Iowa Learning Farms team has spent the last several weeks hittin’ the old dusty trail (or should we say pounding the pavement?) as we travel to our field demonstration/research sites across the state. However, that’s not all that we’re sampling…  the amazing, aerating earthworm is on our radar, as well, thanks to a USDA-NRCS Conservation Innovation Grant.

Many farmers and gardeners quickly recognize the presence of earthworms as a good thing, aiding in fertilization and aeration of the soil. It’s true, earthworms are an excellent biological indicator of soil health!

The common nightcrawler, Lumbricus terrestris, is a deep-burrowing worm species, and it tends to live fairly permanently in one single tunnel or burrow. The earthworms come up to the soil surface at night or after a rain to feed, consuming things like corn stalks, bean stubble, and fresh cover crop residue. The earthworms then pull that plant material back into their tunnel, leaving a well-defined clumpy mound, or midden, on the soil surface.

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DSCN9147In general, one midden = one earthworm. Knowing this, we are able to count the middens to determine the presence and abundance of earthworms in different field plots across the state!

EarthwormCounts-MeganWe are especially interested in comparing earthworm counts in side-by-side strips with and without cover crops, so we’re visiting multiple sites across the state that are a part of the Iowa Cover Crop Working Group’s long-term cereal rye cover crop project. That study is currently looking at cover crop effects on crop yield and soil health, so the earthworm data will be one more piece of the puzzle.

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Stay tuned for further information and results of our earthworm counts as the season goes on!

Ann Staudt