Episode 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:
- Excavate an area of soil to find and count the earthworms
- Use a mustard solution or wasabi to chemically extract the earthworms, drawing them to the surface
- Apply an electrical current to the soil surface and electrically extract the earthworms, drawing them to the surface
- 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!
An earthworm midden
ILF interns counting earthworm middens at a project site
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!
This 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:
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