by Thom Petersen

Nitrate is one of the most common contaminants in Minnesota’s groundwater, and there are unique geologic features in parts of Minnesota that make the groundwater more vulnerable to nitrate contamination.

The U.S. Environmental Protection Agency drinking water standard for nitrates is 10 milligrams per liter. Some public and private wells have nitrate levels that exceed that standard.

Public water systems regularly test for nitrates and ensure levels meet the EPA standard, while it is the responsibility of private well owners to test their wells. Human activities such as sewage disposal, livestock production and crop fertilization can elevate the level of nitrates in groundwater.

Last November, the EPA requested that Minnesota develop a plan and provide education and outreach, as well as alternative drinking water, to residents in eight southeast Minnesota counties that have water containing nitrates above the federal standard.

The Minnesota Department of Agriculture is concerned about nitrates in groundwater. That’s why we’ve taken significant actions over the past decade, and work is ongoing in those eight counties of Dodge, Fillmore, Goodhue, Houston, Mower, Olmsted, Wabasha and Winona, as well as other areas of the state susceptible to nitrate contamination.

This work is being done through collaboration with farmers, partners such as soil and water conservation districts, and other state and federal agencies.

Partner opportunities

The Nitrogen Fertilizer Management Plan is designed to reduce nitrate levels in areas with vulnerable groundwater. This strategy outlines an approach to assessing agricultural practices and working with the agricultural community to select, adopt and implement recommended best practices in the most vulnerable areas of the state.

An important outcome of the plan, which was revised in 2014, was the MDA’s Township Testing Program.

More than 90,000 private well owners were offered nitrate testing in 344 townships across the state through the Township Testing Program from 2013 to 2019. That included 21,801 residents in the eight southeast counties.

Of the 8,714 people who submitted a sample, 12.1% (1,058 wells) were greater than 10 mg/L. The program has provided foundational scientific information to help identify areas of concern and prioritize work for state and local partners.

Another outcome of the Nitrogen Fertilizer Management Plan was the Groundwater Protection Rule. Since 2019, the MDA has implemented the rule, prohibiting the fall application of commercial fertilizer on 71% of cropland (approximately 1.1 million acres) in southeast Minnesota and over 9 million acres statewide.

The MDA has also convened local advisory teams and is working with farmers to adopt practices to address local groundwater problems.

The Minnesota Agricultural Water Quality Certification Program assesses whole-farm risks to water quality and invests in conservation practices that protect our water resources.

On an average certified farm, there is up to a 49% reduction of nitrate loss through the adoption of conservation practices like nutrient management, cover crops and conservation crop rotation.

MAWQCP has certified over 1 million acres statewide since the program began in 2014. There are 269 MAWQCP-certified producers operating over 191,000 acres (as of December 2023) in southeast Minnesota.

Nitrate reduction work is also happening in southeast Minnesota with the Root River Field to Stream Partnership, AgBMP Loan Program, Nutrient Management Initiative and more.

The MDA is committed to working with farmers, landowners and well owners in southeast Minnesota, in conjunction with the Minnesota Department of Health and Minnesota Pollution Control Agency, on mitigating nitrate contamination in groundwater.

Our efforts rely on active participation by local farmers and crop retailers.

I encourage you to get involved. I also encourage private well users to test annually for nitrates, as recommended by the Department of Health.

To learn more about our nitrate reduction work, visit our website at mda.state.mn.us/nitrate.

Petersen is the commissioner of the Minnesota Department of Agriculture.