Iowa farmers are being encouraged to wait for cooler weather to apply anhydrous ammonia in their fields. Barb Stewart, state agronomist with the U.S.D.A.’s Natural Resources Conservation Service, says applying anhydrous ammonia before soil temperatures are constantly below 50 degrees can result in nitrogen loss.

“Anhydrous ammonia can be changed into nitrates and once it’s in that form, it’s soluble. If we get rain later on in the fall or early spring and that nitrogen is already in the form that’s very soluble, it can be leached from the soil,” Stewart said. That nitrogen loss can impact crop development and yields and contaminate groundwater and streams. Stewart says farmers should consider a spring application to make the best use of the nutrients.

“You can even do a split application and do part of your nitrogen either in the fall or early spring and then apply some of it after some of the crop has emerged,” Stewart said. “That’s even better yet because you’d be spoon feeding the nitrogen out there at a time when the crop needs it the most.”

Stewart says she has seen several farmers already applying anhydrous ammonia. The Iowa State University Extension website provides a history of average soil temperatures in every Iowa county. Stewart’s asking farmers to check the website and make sure their local soil temps are below 50 degrees for several days before they apply fertilizer.

Iowa State University Extension website