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Nitrogen Fertilizer Restrictions Begin on Sept. 1

Posted By Jim Calkins, Regulatory Affairs Manager, Thursday, September 24, 2020
Updated: Monday, August 10, 2020

UPDATE: MDA distributed a bulletin on September 24th with more details of the impact of soil temperatures on some nitrogen fertilizers and a new interactive soil temperature map: Know Where and When to Apply Fall Nitrogen Fertilizer

The Minnesota Department of Agriculture (MDA) has distributed a news release to remind farmers that the application of nitrogen fertilizer in the fall and on frozen soil will be restricted in areas vulnerable to groundwater contamination and in Drinking Water Supply Management Areas (DWSMAs) with elevated nitrate levels beginning on September 1, 2020.  The nitrogen fertilizer restrictions are included in the Minnesota Groundwater Protection Rule which became effective on June 24, 2019, and are based on the recommendations included in the Minnesota Nitrogen Fertilizer Management Plan (NFMP; March 2015, Addended July 2019).  The nitrogen fertilizer restrictions are intended to protect groundwater, including groundwater used for drinking water that may be, or has already been, impacted by the 12-13% of Minnesota’s cropland that is vulnerable to groundwater contamination by nitrates from nitrogen fertilizers.

The Groundwater Protection Rule has two parts: Part 1 which restricts the application of nitrogen fertilizer in the fall and on frozen soils in agricultural areas that are vulnerable to groundwater contamination and in protected areas around public wells – Drinking Water Supply Management Areas (DWSMAs) – that have high nitrate levels (nitrate-nitrogen concentrations at or in excess of 5.4 mg/liter), and Part 2 which focuses on public water supply wells with elevated nitrate levels and the protected areas around these wells (the DWSMAs) and includes a combination of voluntary and regulatory efforts designed to mitigate nitrate levels before they exceed the drinking water standard (10 milligrams of nitrate-nitrogen/liter).

Vulnerable groundwater areas include areas where nitrate can move easily through the soil and into groundwater and contaminate drinking water resources including areas with coarse textured soils, karst geology, and shallow bedrock.  Karst geology is dominated by underground fissures and voids that makes them very porous and allows water to move through them rapidly and where contaminants can reach groundwater resources quickly; in Minnesota, karst geology is primarily found in southeastern Minnesota).   Affected agricultural lands can be located on an interactive, online map available on the MDA website that shows the vulnerable groundwater areas and DWSMAs with a resolution down to the individual farm level (see the link below).

Excluding Drinking Water Supply Management Areas (DWSMAs) with nitrate-nitrogen levels greater than or equal to 5.4 mg/liter, several counties that have a low potential for nitrate leaching based on climate (precipitation and evapotranspiration rates), have a short planting season, or have a limited amount of agricultural land (less than 3%) are excluded from the fall nitrogen fertilizer restrictions and there are also a number of state-wide exceptions to the Minnesota Groundwater Protection Rule.  These exclusions and exceptions are outlined in the rule and on the MDA website (see the links below).

The MDA has developed a recorded presentation (YouTube video) that explains the purpose of the Groundwater Protection Rule, where the nitrogen fertilizer restrictions apply, and the exceptions to the rule. This presentation may be accessed through the MDA website at or directly at .  In addition, the MDA will be hosting a webinar on Wednesday, August 12 from 10:00 until 11:00 a.m. to answer questions about the Minnesota Groundwater Protection Rule and the associated nitrogen fertilizer restrictions.

The MDA news release about the nitrogen fertilizer restrictions is available on the MDA website at

Additional links to information about the Groundwater Protection Rule:

If you have questions or comments regarding this MNLA Regulatory Update or the nitrogen fertilizer restrictions under the Minnesota Groundwater Protection Rule, contact Jim Calkins, MNLA Regulatory Affairs Manager, at or 952-935-0682.


Figure 1.  An example of a fertilizer analysis, specifically a fertilizer that contains 15% nitrogen (8.4% ammoniacal nitrogen and 6.6% nitrate nitrogen) by weight; nitrogen fertilizer restrictions designed to protect groundwater and drinking water resources from contamination by nitrates by restricting the application of nitrogen fertilizers on agricultural lands in the fall and on frozen ground are scheduled to become effective on September 1, 2020 (Photo Credit: James Calkins).

Tags:  fertilizer  MDA  nursery grower  regulatory 

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