Soil Health Improvements in the Red River Watershed

Project Date: April 2025 - Ongoing

Location: Robertson County, Tennessee

Waterway improved: Red River

Restoration methods: Cover crops

Supporting the use of cover crops by farmers

In Robertson County, Tennessee, many farmers are embracing cover crops to improve soil health and benefit the Red River. Cover crops like oats, barley, and clover protect and enrich the soil during seasons when a field would otherwise lie fallow (empty). Farmers don’t harvest them, but instead fold them into the soil at the end of a season to increase its nutrient content. While they’re planted, they prevent erosion, preserving fields and keeping silt out of nearby waterways.
In 2024, the Cumberland River Compact purchased a 41-foot roller crimper—a necessary piece of specialized equipment that mechanically terminates cover crops and leaves behind beneficial mulch. The Compact loans the roller crimper to Robertson County farmers free of charge. This equipment loan program reduces labor and expense for farmers using cover crops and was used on over 1,700 acres in the spring of 2025.

Water Friendly Farming in Robertson County

Robertson County, Tennessee, has a rich agricultural heritage, with many large tobacco, corn, soybean, and wheat farms operating commercially today. However, its limestone bedrock and shallow soils are prone to erosion, which can create problems for farmers; storms can easily erode their fields, sometimes even creating sinkholes.

That’s why many Robertson County farmers have been experimenting with cover crops. A cover crop is one (or more) species of plant seeded between “cash crops,” (i.e., crops grown to sell) to keep the soil covered so it doesn’t erode. They are not harvested for profit, but rather, serve to reduce erosion and replenish nutrients and carbon stores in the soil. When it comes to soil health, cover crops are a gold standard and an old standby.

One common and easily recognizable cover crop is crimson clover. Seeded in the fall, this clover will keep the soil covered during the wintertime instead of lying fallow in the off-season. It also has the ability to “fix” nitrogen from the air into the ground and will add an abundance of carbon to the soil once it dies and degrades, readying the soil for spring planting. An additional bonus to crimson clover is that beneficial pollinator insects are attracted by the flower nectar. Ideally, crimson clover is planted alongside complementary cover crops, like oats, rye, hairy vetch, and peas, creating a multi-species cover crop mix. In general, the greater the number of species in a cover crop mix, the more beneficial it will be for the soil: species diversity creates natural pest resistance, nutrient cycling, and resilience against disease.

A Cover Cropping Pioneer

One Robertson County farmer, T.C. Groves, became a true advocate for cover crops after years of following traditional farming practices passed down through generations. After planting his first cover crop, he saw firsthand how it improved the soil health, reduced erosion, and even boosted his yields. He won the Robertson County Soil & Water Conservation District’s Conservation Farmer of the Year award in 2023, joined the Soil & Water Conservation District (SWCD) board to advance conservation practices, and set out to help other farmers make the most of cover crops.

A man standing in an open field under a blue sky. — T.C. Groves on his farm, Corn Silk Farm.

In T.C.’s early years of experimenting with cover crops, he ran into a problem: Although the cover crops he grew were big and healthy, terminating the cover crops (i.e., killing them before planting the next crop) with his existing equipment was tough. He and his farm team spent many frustrating hours cutting plant matter off of his equipment by hand. For a large, fast-paced farm business, this kind of tedious labor was a deterrent.

What T.C. and farmers like him needed was a specialized piece of equipment called a roller crimper that could easily handle the mass of living plant matter. A roller crimper is essentially a long, metal drum pulled behind a tractor. The drum rolls the crops down and blunt steel blades criss-cross the drum and crimp the plants. It turns plants into mulch to cool the soil, retain moisture, and protect the soil from erosive forces. The plant roots slowly die, leaving behind carbon, food for soil microorganisms, and pathways for moisture to circulate. This piece of equipment allows farmers to mechanically terminate cover crops in fewer passes and without using herbicides.

Partnering with the Cumberland River Compact

The Cumberland River Compact assists farmers in maximizing conservation benefits on their land, thereby enhancing water health in the Red River watershed, a subwatershed of the Cumberland River basin. Seeing a need arise among farmers who use cover crops, the Compact consulted with Groves and subsequently purchased a 41’ roller crimper in the fall of 2024. It was put to use the following spring on three farms in Robertson County, including T.C.’s farm.

T.C. flattens cover crops with the Compact’s roller crimper.

Why the Red River Watershed Matters

The Cumberland River Compact focuses on the Red River Watershed because it’s especially vulnerable to water pollution and plays a major role in carrying nutrients downstream to the Gulf. The watershed spans 1,453 square miles across parts of Kentucky and Tennessee, and agriculture takes up over 60% of its land. It also includes about 371 miles of polluted waterways; common pollutants in the area include bacteria, excess nutrients, and sediment.

When fertilizers—whether natural or synthetic—are applied to fields, rain can wash them into nearby streams, raising nutrient levels in the water. Practices like traditional plowing and grazing cattle near streambanks increase erosion, leading to more sediment in the water.

The Red River Watershed has less natural vegetation than other nearby watersheds, which makes it harder for the land to filter out pollutants before they reach waterways. Additionally, its karst landscape—full of sinkholes, caves, and underground streams—allows pollution to move quickly into both groundwater and surface water.

To address these issues, the Cumberland River Compact supports projects that improve soil health and promote sustainable farming methods, like planting cover crops. These practices help reduce nutrient runoff, protect water quality, and prevent low-oxygen “dead zones” in downstream waters.

Credit: Ohio Department of Natural Resources

Scientists track nutrient flows to determine which regions are contributing to the infamous Gulf Hypoxia Zone (shown above). One such group, the Freshwater Network, has determined that the Red River watershed is in the 97th percentile of sub-basins contributing nutrients to the Gulf Hypoxia Zone.

The Cover Crop Solution

According to research compiled by Sustainable Agriculture Research & Education (SARE), cover crops can accomplish the following water quality benefits:

Reduce erosion on farms by 1.2 tons per acre
Reduce nitrogen losses by 48%
Reduce phosphorus loads to water by 15-92% (More research on phosphorus load reduction is needed.)

Field Results and Next Steps

Learning to use a new piece of farm equipment often requires a bit of trial and error, and weather can be a significant factor in its usage and efficacy. In this case, the species mix T.C. chose didn’t grow well in the dry spring of 2025, and so the cover crop stand was not as robust as it might have been with more consistent rain. Still, T.C. was able to utilize a cover crop on 1,000 acres. His neighbors were eager to utilize cover crops on their land as well, so the roller crimper was used on an additional 500 acres that same season.

Project Sponsors

This project was funded by Google.