REMINDER: Nitrogen fertilizer fall and frozen soil application restrictions begin September 1 each year.

View the map to see where the restrictions apply and learn more about this part of the rule.

The Groundwater Protection Rule (GPR) minimizes potential sources of nitrate pollution to the state’s groundwater and protects our drinking water. The rule restricts the application of nitrogen fertilizer in the fall and on frozen soils in areas vulnerable to contamination, and it outlines steps to reduce the severity of the problem in areas where nitrate in public water supply wells is already elevated.

Rule documents

*A number of web addresses in the rule have changed. Please view the Updated Links (PDF) to access the references listed.

Parts of the Rule

The rule contains two parts. Each part contains separate criteria and requirements. Depending on where you farm, you may be subject to one part of the rule, both parts, or none at all.  

The rule is intended to promote appropriate nitrogen fertilizer best management practices (BMPs) and to involve local farmers and agronomists in adopting the most current science-based and economically viable practices that can reduce nitrate in groundwater. These other practices are called alternative management tools (AMTs).

Use the following links to find more detailed information.

A quick summary of Parts 1 and 2 of the rule are included below.

Part 1 of the rule

Part 1 of the Groundwater Protection rule 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 areas (DWSMA), with high nitrate.

Vulnerable Groundwater Areas are determined by coarse textured soils, shallow bedrock, or karst geology and are designated by quarter sections or government lot. An entire quarter section or government lot is included if 50% or more of the area is considered vulnerable.

Notification of areas subject to fall application restrictions under Part 1 of the rule will be posted annually on January 15. Restrictions begin September 1 each year.

View additional information on Part 1 of the Groundwater Protection Rule

Part 2 of the rule

Part 2 of the rule responds to DWSMAs which already have elevated nitrate. The goal is to take action to reduce nitrate in groundwater before a public well exceeds the health standard for nitrate. The rule is structured using a sliding scale of voluntary and regulatory actions based on the concentration of nitrate in the well and the use of the BMPs. The MDA will form a local advisory team with farmers, agronomists, and other community members. This team will be involved in reviewing, considering and advising the MDA on appropriate practices or requirements to reduce nitrate in the DWSMA. 

There are four mitigation levels used to determine voluntary and regulatory actions, two voluntary levels and two regulatory levels. All areas will begin at a voluntary level and move to regulation only if BMPs are not adopted or if nitrate contamination in the groundwater increases.

Regulatory actions under Part 2 of the rule are delayed at least three years from the date the rule took effect and after a DWSMA is determined to meet the criteria for Level 2. The Groundwater Protection Rule became effective on June 24, 2019.

View additional information on Part 2 of the Groundwater Protection Rule