Farmers being advised to hold off on applications of anhydrous ammonia

Staffers with the Iowa Department of Agriculture and Land Stewardship and with ISU Extension and Outreach are advising farmers to wait to apply anhydrous ammonia as a way to help reduce nitrogen loss and better protect the environment.

The agencies say it's best to wait until soil temperatures remain below 50 degrees Fahrenheit before applying anhydrous ammonia (NH3) fertilizer this fall.   ISU Extension and Outreach maintains a statewide real-time soil temperature data map on their website that ag retailers and farmers use to determine when fall N applications are appropriate.  The website can be found at http://extension.agron.iastate.edu/NPKnowledge/.

"The reason for waiting to apply anhydrous ammonia until soils are cold is that nitrification, the process of biological conversion of ammonium to nitrate, occurs at a more rapid rate with warm soils. Since ammonium-N does not leach and is not subject to denitrification, as is nitrate, it is more stable in the soil," said ISU Extension specialist John Sawyer, a professor in soil fertility and nutrient management at Iowa State University.

In addition to waiting for cooler soil temperatures, farmers should also make sure that the soil is not too dry, too hard, or too wet as those conditions can cause injection issues and allow ammonia to move to the soil surface and be lost to the air.  If conditions are not suitable, then waiting for better conditions is suggested.