So you are considering making anhydrous ammonia applications this fall. Why the fuss over waiting until 50°F and lower soil temperatures?
The form of nitrogen that can potentially be lost from soils due to wet conditions is nitrate (NO3-) (Figure 1). The form applied as anhydrous ammonia is NH3, which is quickly converted to ammonium (NH4+) when it comes in contact with water in soil. Because ammonium is a positively charged ion, it is attracted by electrostatic forces to negatively charged soil. Ammonium is not leached or lost by denitrification (conversion to a nitrogen gas).
Iowa State University
Sawyer, John E., "Why 50 degrees Fahrenheit?" (2001). Integrated Crop Management News. 1933.
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