MCGA highlights strengths of Minnesota Groundwater Protection Rule
In January, the Minnesota Department of Agriculture (MDA) opened a public comment period on the adequacy of the state’s Groundwater Protection Rule. The action was in line with a court-approved stipulation agreement between the plaintiffs (a coalition of environmental groups) and the defendants (Attorney General/MDA and a Minnesota Corn Growers Association (MCGA) led coalition of farmer organizations).
As part of its mission to ensure corn farmers have the tools they need to productively and efficiently raise a crop, MCGA submitted comments to MDA on the rule. The following is a summary of those comments.
—
The Minnesota Groundwater Protection Rule (GPR) provides a strong, targeted framework for limiting nitrate-nitrogen impacts from commercial fertilizer to groundwater. The rule emphasizes local collaboration, adoption of best management practices (BMPs), and includes meaningful escalatory steps when nitrate-nitrogen levels are elevated.
Because groundwater moves slowly through aquifers, near-term nitrate monitoring observations often reflect historical conditions. As a result, the rule should be evaluated over its full implementation cycle, and additional restrictions are unnecessary.
The GPR is correct to take a targeted approach to nitrate-nitrogen mitigation. More than 99% of Minnesota’s community public water systems comply with the federal nitrate standard of 10 mg NO3-N per liter, and 93% have average source-water nitrate-nitrogen concentrations within the normal background range of 0–3 mg NO3-N per liter. Statewide ground and surface water monitoring data do not show widespread statistically significant increasing trends in nitrate-nitrogen concentrations.
The GPR consists of two parts comprised of separate criteria and associated requirements. Part 1 of the GPR restricts the application of nitrogen fertilizer in the fall and on frozen soils if you farm in 1) an area with vulnerable groundwater or 2) those protection areas around a municipal public well, known as a drinking water supply management area (DWSMAs), with high nitrate-nitrogen concentrations. To see if you farm in a vulnerable groundwater area, view the vulnerable groundwater areas map.
If nitrate-nitrogen concentrations in a DWSMA are already elevated, the rule has a robust sliding scale process for mitigating leaching to groundwater within the DWSMA. The process consists of four mitigation levels beginning with a suite of active monitoring, outreach, and voluntary adoption of nitrogen management practices. If nitrate-nitrogen conditions are higher, it includes the formation of local advisory teams (LATs) consisting of producers, agronomists, public water suppliers, SWCD staff, technical experts, and other local representatives. Those teams must publish site-specific BMPs tailored to the DWSMA.
The rule requires those identified BMPs to be implemented on at least 80% of cropland (excluding soybeans) within three growing seasons. It also allows for regulatory actions if BMPs are not adopted or if nitrate-nitrogen concentrations within the DWSMA increase.
In the 25 DWSMAs designated as Mitigation Level 2, 18 have local advisory teams, and 12 have published BMP lists. In several instances, collaboration among water suppliers, conservation agencies, and producers has already led to measurable BMP adoption. For example, in the Goodhue DWSMA, implementation efforts supported conservation practice implementation on more than 1,500 acres by 2025—approximately three-quarters of the contributing area—to both reduce nitrogen leaching and improve soil health.
The GPR also accounts for the complex nature of groundwater movement, notably the fact that measured nitrate-nitrogen concentrations from the aquifer are a lagging indicator of BMP effectiveness. In most landscapes, groundwater moves slowly through layers of soil and rock with monitoring reflecting land management practices from previous decades. As a result, early progress under the rule is best evaluated through BMP implementation alongside longer-term groundwater monitoring over the rule’s full implementation cycle.
Defending farmers’ crop production tools
For years, the Minnesota Corn Growers Association (MCGA) has worked to ensure corn farmers are represented in discussions around fertilizer regulations. The organization was actively involved in shaping the Minnesota Groundwater Protection Rule when it was adopted in 2019.
More recently, MCGA has been engaged as environmental groups petitioned the Environmental Protection Agency (EPA) to impose additional regulations on manure and fertilizer use in Southeast Minnesota. In January 2025, several of those groups filed a lawsuit against the Minnesota Department of Agriculture (MDA) and the Minnesota Pollution Control Agency (MPCA) seeking further state regulation of commercial fertilizer and manure application, respectively. In response, MCGA led a coalition of nine farmer organizations in a request to intervene in the case.
In September, the parties in the lawsuit reached an agreement requiring MDA to evaluate whether the Groundwater Protection Rule adequately limits nitrate-nitrogen impacts from commercial fertilizer to groundwater. As part of that review, MDA opened a public comment period in January.
Earlier in 2025, MCGA also participated in the MPCA’s public comment process on proposed updates to the state’s feedlot and manure management rules (Minnesota Rule 7020).
