A secret world beneath the surface of the soil

Nic Jelinski is standing at the bottom of a six-foot deep hole in the middle of a corn field in Waseca, Minnesota. “Can you see how the first two feet of soil is black?” he asks the group of conservation professionals gathered around him. “That’s where top soil with organic matter has built up over time. The gray soil underneath shows us that the soil here is usually saturated with water from this point on.”

Nic Jelinski (center in pit), Jodi DeJong-Hughes (right), and Matthew Lundberg (left) shared their insights about soil health during a conservation field seminar in southern Minnesota.

As we continue to stare at this somewhat unremarkable looking hole in the ground, Jelinski points to a dark grey circle in the soil horizon about four feet down. “That’s a crayfish burrow that was probably formed 100 years ago,” he explains. “Just from looking at the soil in this pit, I can tell that the land here was originally a wet meadow before it became a farm.”

Jelinski is an Associate Professor of Soil, Water and Climate at the University of Minnesota, and was one of several experts invited to speak at the 2022 Soil Health Nexus. The annual event offers hands-on training for conservation farming professionals, and brings in staff from Minnesota, Wisconsin, Michigan, Indiana, Iowa, and Nebraska.

Conservation farming professionals from Minnesota, Wisconsin, Michigan, Indiana, Iowa, and Nebraska gathered for the Soil Health Nexus.

The lakes, streams, rivers and rolling landscape of Minnesota were carved during a series of glaciations that occurred between 2 million and 10,000 years ago, and these same glaciers dragged in deposits of rock and soil from places as far away as northern Canada. Our state also lies at the intersection between four major biomes – deciduous forest, coniferous forest, prairie grasslands, and tallgrass aspen parkland.

Over time, as people have cultivated and developed the landscape, however, the geologic and ecologic history of our state has been buried underground. When working with farmers to improve soil health, soil scientists will sometimes begin by digging a soil pit. It is somewhat like an archaeological dig, except the focus is on finding geological clues to the past, as opposed to pottery or dinosaur bones.


Did you know there could be seashells underneath corn fields? 🐚 #soilscience #farming #minnesotafarming

♬ original sound – Angie Hong

Matthew Lundberg, a soil conservationist with the Natural Resources Conservation Service (NRCS) works with farmers in Dakota and Washington Counties. “Sometimes I find shells from aquatic organisms – snails, clams and mussels – 30 inches down below the surface of the soil in a corn or soybean field,” he says. “There could be a whole aquatic ecosystem underground but you wouldn’t know it from looking at the field.”

Though it might initially seem perplexing to find buried shells and crayfish burrows in the middle of a corn field, it makes sense once you consider that many farmers in southern Minnesota have constructed ditches and installed tile in order to cultivate wet meadows and seasonal wetlands.

On a meta scale, the use of drain tile has dramatically altered the natural hydrology of our river systems in southern and western Minnesota. Now, when it rains, the water rushes quickly into streams and rivers, causing soil erosion and downstream flooding. The Minnesota River runs brown like chocolate milk and this soil is carried onward to the Mississippi River as well.

Jennifer Hahn, a University of Minnesota agronomist working for the Lower St. Croix Partnership, notes that deep tillage (like what you see in the photo above) breaks up mycorrhiza and contributes to erosion and loss of soil fertility.

At a parcel level, soil scientists work with farmers to improve soil health, minimize erosion, and avoid compacting the soil. “We’ve surveyed ditches near farm fields in southern Minnesota and found that some are carrying away as much as 3200 tons of soil per year for a half-mile long by 20-foot wide ditch,” says Jodi DeJong-Hughes, a University of Minnesota Extension Educator who attended the Soil Nexus. “I’ve also been in places where I break my knife trying to dig into a farm field because the soil is so compacted.”

Through the Federal Conservation Reserve Program, farmers can receive payments of $225-300 per acre to establish prairie strips. These native plantings help to reduce erosion, provide habitat, and filter pesticides and nitrates out of water as it soaks into the ground.

To help keep the soil on the land and out of the water, crop farmers can implement a variety of best management practices, including planting cover crops during the winter; implementing no-till, strip-till, or conservation tillage; and restoring natural habitat in key locations such as within historic wetland basins, along steep hills, and in drainage pathways. If you own or rent farmland, contact your county’s Soil and Water Conservation District to learn more about financial and technical assistance for these practices.