2026 October Stewardship Advocate

2026 October Stewardship Advocate

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Cover Crops are an Effective Tool to Reduce Nitrogen Loss

Nitrates and water quality are receiving increased attention across Iowa. To effectively address the problem, it's important to understand where and why nitrogen loss is occurring. A study by Rogovska et al. examined how tillage, cover crop, and in-situ bioreactors affected nutrient loss at the USDA Long-Term Agroecosystem Research Experiment near Ames. ¹

One key finding was that eliminating nitrogen fertilizer did not eliminate nitrogen loss. After 10 years of crop production without nitrogen fertilizer, nitrogen loss to drainage was not statistically different than plots receiving N fertilizer. Plots receiving about 175 pounds of N per acre lost an average of 13.86 pounds of nitrogen per acre per year through tile drainage. Plots receiving no nitrogen fertilizer lost 10.72 pounds per acre annually*. This suggests that fertilizer is not the only source of nitrogen loss.

* results adjusted from kg N/ha to lbs N/ac.

Why does nitrogen loss occur? Iowa's fertile soil contains large amounts of nitrogen stored in organic matter. Through mineralization, soil microbes convert organic nitrogen into inorganic forms such as nitrate and ammonium. This biological process starts when soil conditions are fit for microbial activity. There are times during the year when microbes are actively mineralizing nitrogen, but plants aren't actively growing and using the nitrogen, creating the potential for loss. In the article by Iowa Agricultural Water Alliance, Raising Better Crops and Minimizing Our Impact on the Environment², ISU Professor Dr. Michael Castellano explains the mismatch between natural nitrogen cycles and a normal corn and soybean growing season.

Good news: cover crops are one proven solution! In the Rogovska et al. study, adoption of cereal rye cover crop reduced nitrogen loss by 63% compared to typical management (one tillage pass and no cover crop).¹ A 2013 - 2017 study by Iowa Learning Farms, Practical Farmers of Iowa and ISU Extension and Outreach had similar findings; there was a 61% spring nitrate reduction in soybean plots with adoption of a cereal rye cover crop.³

Farmers are actively engaging in solutions to improve water quality in Iowa by adopting practices proven to reduce nutrient loss. Cover crop adoption is increasing around the state, with IDALS reporting record cover crop cost-share sign-up this year.

Need help getting started with cover crops or other conservation practices? Check out the Conservation Professionals Map. Released in September, this tool connects farmers and landowners to conservation professionals around the state. Visit the IAWA Conservation Compass to learn about available cost-share options.

Latest Information

Secretary Naig Encourages Iowa Farmers to Plant Fall Cover Crops to Save Money on Crop Insurance

USDA Increases Investment in Regenerative Pilot Program from $700 million to $1 billon

New map connects Iowa farmers and landowners with local conservation professionals

Fall rains give cover crops a boost

Farmer to Farmer: Darin Proffit

Nestled in the rolling hills of southwest Iowa, Darin Proffit farms alongside the O'Hara family as part of their corn and soybean operation near Shenandoah, Iowa.

Originally from St. Joseph, Missouri, Darin got his start in Iowa agriculture 15 years ago, working at his grandfather's aerial application business. He later joined the O'Hara family's farming operation and seed business, O'Hara Seed Inc., and has been marketing his own grain for seven years.

Darin focuses on technology and conservation to improve soil health and enhance profitability. The farm is 100% no-till and utilizes cover crops ahead of soybeans, by aerial seeding cereal rye into standing corn. Darin uses cover crops as part of his weed control strategy, and because they protect and build soil organic matter.

Darin's long-term goal is to leave the land better than he found it. "I want to be a part of something that builds the ground through my generation, so that future generations can continue to farm this ground."

Darin is adopting new technology to improve fertilizer efficiency and recently invested in the John Deere ExactShot^TM in-furrow system. This precisely places starter fertilizer in bands between seeds, allowing the operation to reduce starter volume by two-thirds. Darin mentioned environmental and economic gains through use of this technology. "This has been a win for the checkbook, and it allows us to be more responsible with fertilizer application."

Beyond the farm, Darin serves as the Iowa Corn Promotion Board District 7 Director and Vice Chair of the Research and Business Development Committee. He also participates in the National Corn Growers Association's Risk Management Action Team, and additional teams as asked.

 For Darin, involvement in Iowa Corn is an opportunity to support farmers across the state and share agriculture's story. "It's very rewarding to be a part of something bigger than just your own operation. To have the privilege of voting on issues that matter to all corn farmers is something I take very seriously. I like having the ability to educate both growers and consumers with real-world stories. Being a part of Iowa Corn gives me the resources and confidence to do it."

Upcoming Events:

• November 3: Cover Crops and Manure Management - Iowa Learning Farms; Le Mars Convention Center, 275 12^th St. SE, Le Mars: 12:00 p.m. - 2:00 p.m.
• November 3: Cover Crops and Conservation Across All Acres - PFI; Drost Farms, 2215 212^th St. Oskaloosa, IA: 12:00 p.m. - 2:00 p.m.
• November 4: Cows, Creeks and Common-Sense - Iowa Learning Farms; 1411 111^th Ave, Castalia, IA 52133: 12:00 p.m. - 2:00 p.m.
• November 5: ISU Northern Research Farm and Boone River WMA Field Day; 2310 S Main St. Kanawha, IA: 8:30 a.m. - 1:00 p.m.
• November 11: Prairie and Pollinator Field Day - Iowa Learning Farms and Pathfinders RC&D; 610 West 4^th St. Storm Lake, IA: 12:00 p.m. - 2:00 p.m.
• November 12: Cover Crop and Grazing Field Day - Iowa Learning Farms; 26129 Tivoli Lane, Epworth, IA. 12:00 p.m. - 2:00 p.m.

Virtual Events:

• Iowa Nutrient Research Center Fall 2026 Seminar Series: Nutrient Reduction Around the World: Second Wednesday of the month from September through December
  • November 11, 3:10 p.m. - 4:00 p.m.; Protection of Water Quality in New Zealand
  • December 8, 3:10 - 4:00 p.m.; The Nonpoint Source Challenge, U.S.
• Iowa Learning Farms Wednesday Conservation Webinar- Every Wednesday at Noon

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