Anhydrous ammonia application should be delayed until soil temperatures are 50°F and trending downward. Soil microorganisms convert ammonia to nitrate nitrogen so as temperatures decline, this conversion rate slows.

Wait until soil temperature at the 4” depth are below 50°F and are expected to move toward freezing. Soil temperature measurements can be found at the University of Missouri weather stations located at Graves Chapple, Buchanan County Extension Center and Hundley-Whaley.

Ammonia has an advantage that soil microorganisms are required to convert from the outer injection zone inward which slows the conversion process compared to a dry urea product in the form of granules.

Questions always are asked about the use of nitrification inhibitors. The long-term average with give you approximately two weeks of delaying the conversion. But what is often misunderstood, is if we fall apply too early in the fall, the value of the nitrification inhibitor will be lessen. Again, ammonia should be delayed until soil temperatures move downward and this will allow the use of the nitrification inhibitor to be valuable in the spring and maybe early summer.

As far as other best management practices do not fall apply ammonia to sandy soils as the ammonium nitrogen and nitrate nitrogen may be leached below the rootzone. With poorly drained soils, nitrogen is converted by microorganisms in water saturated soil conditions and lost to the air.

The rains may help seal fall ammonia. Dry soils can risk the movement upward in the knife track and be lost. Also, if the soil is too wet, the knife track can also fail to seal allowing losses. Some add-ons such as coulters and other methods of covering the knife track might be valuable in certain situations. If you smell ammonia the next day after ammonia application, you are experiencing losses.

For more information, contact Wayne Flanary, Field Specialist in Agronomy, University of Missouri Extension at 816-279-1691 or cell phone 913-220-3670.