MDA reminds farmers of fall nitrogen fertilizer rules
A Minnesota Department of Agriculture (MDA) news release reminds farmers and commercial fertilizer applicators of fall nitrogen fertilizer restrictions in certain parts of the state. The state’s Vulnerable Groundwater Area Map, which was last updated in January 2024, highlights areas where those restrictions are enforced. Generally, fall nitrogen application is restricted in southeastern Minnesota, along with some central and north-central parts of the state. The restrictions begin Sept. 1 each year.
The MDA news release encourages farmers and commercial applicators outside of vulnerable groundwater areas to wait until the average soil temperature is 50 degrees or cooler before applying manure or nitrogen fertilizer. Research shows that delaying fall application helps prevent nitrogen loss, protect water quality, and ensure more nitrogen availability for the next season’s crop, the release says.
MDA directs farmers and commercial applicators interested in tracking soil temperature in their area to its online 6-inch soil temperature network map. You can find the current 4- and 6-inch soil temperature at 70 locations across the state and see the past week’s soil temperature history.
The fall nitrogen restrictions are part of the Minnesota Groundwater Protection Rule, which minimizes potential sources of nitrate pollution to the state’s groundwater. In part one of the rule, MDA prohibits fall nitrogen fertilizer application on areas with vulnerable ground water and protection areas around a municipal public well that have high nitrate levels. Vulnerable groundwater areas are considered farmland with coarse textured soils, shallow bedrock, and karst geology.
In part two of the rule, MDA outlines steps to reduce the severity of contamination in areas where nitrate is already elevated in public water supply wells. A 2019 Minnesota Corn news post highlights the details of the Groundwater Protection Rule. It can be found here.
For more information on the restrictions outlined in the Groundwater Protection Rule, visit mda.state.mn.us/nfr. The University of Minnesota Extension’s Nutrient Management Podcast covers fall fertilizer in its latest episode. The full episode can be found here.
