Producers have been applying fall anhydrous ammonia for the past several weeks. Soil temperatures this past week averaged around 50° Fahrenheit and one wants these soils to continue to cool according to this week’s forecast. This is good except ammonium continues to nitrify to nitrate until 32° Fahrenheit then stops. We will need to monitor early applied ammonia fields next year for sufficient nitrogen.
Several growers use different nitrification inhibitors as they apply their anhydrous ammonia. For example, growers may apply nitrapyrin as a nitrification inhibitor that slows the conversion of ammonium to nitrate. Nitrapyrin is degraded over time by chemical hydrolysis when lessens over time. It’s important to realize that warm soils can speed nitrapyrin breakdown, therefore, consider soil temperature even when using this product. The reason for use of a nitrification inhibitor is for next spring to have more ammonium present during excessive wet periods. There is risk of nitrogen loss next year when using nitrification inhibitors during fall warm weather.
Another issue is that dry soil can also lose ammonia. Ammonia needs water to react when applied to the soil. This takes a little time and is not immediate. The reaction is the ammonia gas is converted to ammonium ion which can attach to the soil. The wetter the soil, the more rapid this conversion, and in dry soils conversion is slower. Dry soils can allow ammonia to escape before it converts into ammonium.
One of the most important ways of getting ammonia to seal in dry soil is to inject 6 to 8-inches deep. Shallow injection will allow ammonia to move upward in loose soil. Be sure soil is sealed above the slot. This can be accomplished by wing sealers and also closing disks.
If you walk across a field and smell ammonia, you should change your equipment setup or place ammonia deeper into the soil or wait until better soil conditions.
For more information, contact Wayne Flanary, Field Specialist in Agronomy, University of Missouri Extension at 816-279-1691.
