Lower Nitrogen Rates Show Promise for Southeast Minnesota Corn Farmers

Farmers in Rice and Steele counties are finding that using less nitrogen fertilizer may still deliver solid corn yields—while improving profitability and environmental outcomes.

A multi-year on-farm research project, the Rice–Steele Soil Health Nitrogen Rate – Return on Investment Trials, is evaluating whether nitrogen fertilizer rates guided by soil health testing can outperform traditional recommendations. The project involves eight corn farmers Rice and Steele Counties in Southeast Minnesota who have adopted soil health practices such as no-till, strip-till, cover crops, and diversified crop rotations for several years. The Minnesota Department of Agriculture, Sustainable Agriculture Development Grant, provided funding for the trials.

Applying Nitrogen and interseeding cover crops into MDA Sustainable Agriculture Demonstration plots at Joe Hollinger’s farm. Northfield, MN, June 17, 2025. Credit: Alan Kraus Rice & Steele SWCD

On each farm, corn was grown in side-by-side plots comparing nitrogen rates recommended by traditional soil testing with lower rates recommended by the Haney H3A soil health test. This test measures the soil’s biological activity not captured in traditional soil tests. The biological activity is an indicator of the ability of the soil to make organic nitrogen available to growing plants. Aside from the nitrogen rate, all other management decisions were left up to the farmers and maintained the same on all plots on each farm.

Across the farms, the Haney-recommended plots used an average of 20.5 pounds less nitrogen per acre—about an 11 percent reduction. Yields in those plots averaged 3.2 bushels per acre less than traditional plots, a difference that was not statistically significant.

More importantly, the 2025 results revealed that soil biology played a major role in yield. Organic nitrogen and soil respiration, indicators of biological activity, were more closely linked to yields than nitrate nitrogen alone.

The reduced nitrogen plots also used fertilizer more efficiently. Those plots produced 33 percent more corn per pound of nitrogen applied than traditional plots. With corn priced at $4.50 per bushel and nitrogen at $0.67 per pound, the reduced-rate plots returned 53 percent more value per pound of nitrogen.

A partial budget analysis showed that extra nitrogen often did not pay. Five of the eight farms saw a negative return on the additional nitrogen applied in traditional plots. When one outlier farm was removed, the average return on the extra nitrogen was a loss of $2.71 per acre.

Environmental benefits were also significant. Reducing nitrogen by 20.5 pounds per acre avoided an estimated 160 pounds of greenhouse gas emissions per acre each year and lowered the risk of nitrate loss to water.

The results show soil health testing can help farmers fine-tune nitrogen rates, protect water quality, and improve farm profitability—without sacrificing yield.

The Rice–Steele Soil Health Nitrogen Rate – Return on Investment Trials will continue through the 2027 growing season. For more information about the project, contact me at the Rice SWCD office at 507-332-5408.

Alan Kraus is a Soil Health Specialist with the Rice and Steele SWCDs. He works with producers and landowners in both counties to implement soil health conservation practices. In Rice County, he also promotes the Soil Health Incentives Program and Custom Interseeding Program. Contact Alan with your conservation questions at 507-332-5408.