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Home > News, Media & Government Relations > News Releases > MDA encourages farmers to use soil temperature to guide fall nitrogen application timing

News Release

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FOR IMMEDIATE RELEASE:  Wednesday, September 23, 2015

MDA encourages farmers to use soil temperature to guide fall nitrogen application timing

Network of soil temperature monitoring stations provides real-time data

ST. PAUL, Minn. – The Minnesota Department of Agriculture (MDA) advises farmers and fertilizer applicators to check soil temperatures when timing application of ammonium-based nitrogen fertilizers this fall.

“In areas where fall nitrogen applications are appropriate, soil temperature, not harvest progress, should be your guide of when to apply,” says Bruce Montgomery, manager of the MDA Fertilizer Management Section. “Waiting until soil temperature stays below 50º F before applying anhydrous ammonia and urea increases the availability of nitrogen to next season’s crop and decreases the amount of nitrate that could potentially leach into groundwater.”

Soil temperature is measured at a six-inch depth; the same depth anhydrous ammonia is typically applied. To help farmers know when the target 50º F soil temperature has been reached, the MDA has established 21 real-time, statewide soil temperature monitoring stations. Station data is updated every 15 minutes with the help of satellite uplink technology from the Minnesota Department of Natural Resources and the National Weather Service.

According to Dr. Mark Seeley, University of Minnesota Extension climatologist, on average soil temperatures reach 50º F during the first week in October in northern Minnesota and the fourth week of October in southern Minnesota.

In addition to delaying application until soil temperatures stay below 50º F, best management practices for nitrogen use developed by the University of Minnesota Extension recommend using a nitrification inhibitor when fall applying anhydrous ammonia and urea in south-central Minnesota. In southeast Minnesota’s karst region and statewide on coarse-textured soils, fall application of nitrogen fertilizer is not recommended regardless of soil temperature. Specific nitrogen use recommendations by region of the state.

The MDA has announced plans to develop a rule over the next two to three years which will restrict fall nitrogen fertilizer application in areas vulnerable to groundwater contamination. This would include southeast Minnesota’s karst region and statewide on coarse-textured soils. The rulemaking is part of the state’s revised Nitrogen Fertilizer Management Plan which was completed March of this year. More information on the plan.

CONTACT: Allen Sommerfeld / MDA Communications
651-201-6185 / allen.sommerfeld@state.mn.us

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