The Minnesota Department of Agriculture (MDA) advises farmers and fertilizer applicators to check soil temperatures before fall application of ammonium-based nitrogen fertilizers. Warm weather this season has kept soil temperatures around the state from dropping below 50˚ F, the recommended temperature to apply nitrogen and avoid fertilizer loss.
On average, soil temperatures reach 50˚ F during the first week in October in northern Minnesota and the fourth week of October in southern Minnesota. However, that has not happened this year, with soil temps remaining above 50˚ F in many parts of the state.
Soil temperature is measured at a six‑inch depth; the same depth anhydrous ammonia is typically applied. Station data on the MDA online map is updated every 15 minutes with the help of satellite uplink technology from the Minnesota Department of Natural Resources and the National Weather Service.