Know where and when to apply fall nitrogen fertilizer in Minnesota

Minnesota's Groundwater Protection Rule restricts fertilizer applications in some areas.

When used safely, anhydrous ammonia is of minimal concern for producers. However, if the substance is used in an unsafe manner, it can lead to very dangerous outcomes. Forum News Service file photo.

ST. PAUL, Minnesota — The Minnesota Department of Agriculture reminds farmers and commercial applicators that fall nitrogen fertilizer applications are restricted in some areas of the state.

Under the MDA’s Groundwater Protection Rule, fall nitrogen fertilizer application is prohibited in vulnerable areas of Minnesota due to environmental concerns or risks. Areas with coarse-textured soils or areas above fractured bedrock or karst geology are the most vulnerable to nitrate loss and groundwater contamination. View a map of the vulnerable regions of the state at . For more information on the restrictions outlined in the Groundwater Protection Rule visit .

In areas where fall nitrogen fertilizer application is allowed, MDA advises farmers and applicators to wait for cooler conditions. Research shows that delaying fall application of anhydrous ammonia and urea fertilizer, as well as manure, until the average soil temperatures reach 50 F or cooler helps prevent nitrogen loss, protects water quality and ensures more nitrogen will be available for next season’s crop.

The MDA provides real-time, 6-inch soil temperatures at 25 locations across the state, as well as links to soil temperature from the University of Minnesota research stations and the North Dakota Ag Weather Network weather stations. View the interactive map at .

The soil temperature network was established to support application of nitrogen fertilizer but it is just as useful for applying manure in the fall. Research from the University of Minnesota showed liquid dairy and hog manures injected in November produced yields 10 bushels per acre higher than manures injected in September and October.


For more information on the Six-inch Soil Temperature Network visit .

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