BLOOMINGTON, Ill. — The autumnal rite of Illinois farmers applying nitrogen (N) to their fields could be threatened if producers continue to encourage nitrate leakage by adding the nutrient too early in the season, according to the new “Keep it in the Crop (KIC) by 2025” stewardship program.

Under the KIC banner, Illinois Corn and the Illinois Fertilizer & Chemical Assoc. (IFCA) have issued Best Management Practices (BMPs) for the fall application of N fertilizers to farm fields, advising producers it is probably still too early in the season to apply N according to the state soil temperature map. KIC cites both environmental and financial advantages for farmers who wait until ground temps are proper for fall N application.

“Protecting your (N) investment is more important than ever, considering the cost of N coupled with the pressure on agriculture to reduce N losses from field tiles,” said Jean Payne, IFCA president. “The ability to apply fall N is important to Illinois farmers and the fertilizer industry.”

Illinois Corn, a group comprised of members and officials of the Illinois Corn Growers Assoc. and the Illinois Corn Marketing Board, called fall N application a “hot-button” issue currently “under the microscope” in the state.

“The temptation is certainly there, but the truth of the thermometer remains. It’s too early in the season to apply (N) if you are following (BMPs),” advised Illinois Corn last week. “Compromising the integrity of the industry at this point could very well compromise fall-applied N for everyone in Illinois.

“Users should be aware that soil temperature fluctuations during the fall may result in periods with soil temperatures below the accepted threshold for N application, followed by an extended period with soil temperatures above the accepted threshold. Therefore, users are advised to be aware of both the current soil temperature and short- to long-term weather forecasts.”

The 24th edition of the Illinois Agronomy Handbook advises farmers to wait until the daily maximum soil temperature in their region reaches a prolonged average of 50 degrees Fahrenheit before applying N to fields. The Illinois State Water Survey (ISWS) offers a daily updated map listing four-inch soil temperatures across the state based on data gleaned from selected Illinois Climate Network Stations.

Illinois Corn recommends farmers and applicators monitor their region’s soil temperatures via the water survey data, which is accessible at www.isws.illinois.edu/warm/soiltemp.asp

The KIC nutrient stewardship program recommends fall-applied anhydrous ammonia be stabilized before application. Stabilization protects against nitrate leaching losses, Payne noted.

“Fall N is an acceptable agronomic practice when it’s applied according to recommendations. Stabilizing fall N is something that can ensure against nitrate losses when soils begin to warm in late winter and tiles start to flow,” she said.

Patrick Kirchhofer, manager of the Peoria County Farm Bureau, said N is currently being applied on farm fields in Peoria County.

“N-Serve is a (N) stabilizer that is being put on with anhydrous ammonia, which helps keep N in a form that will stabilize it and prevent it from leaving the soil profile,” Kirchhofer said.

“When the soil warms up the next spring, the anhydrous ammonia will convert to a form of N that is available for the corn plant to take up.”

Kirchhofer stressed soil temps must have dropped to 50 degrees or less at a four-inch depth in order for the N to achieve stabilization. Warmer soil temperatures do not protect against conversion to nitrate.

Jim Angel, state climatologist with the ISWS, agreed the threshold for applying fall fertilizer is a soil temperature of 50 degrees. “What you want to do is wait a little beyond the first day when soil temperatures reach 50 degrees. Sometimes it will swing back and forth before the colder weather of late November settles in,” he said.

According to the ISWS Water and Atmospheric Resources Monitoring Program, soil temperatures recorded at its Peoria Station averaged 50.3 degrees last Saturday. Stations in northern Illinois recorded soil temperatures in the mid- to upper 40s, while central Illinois stations’ soil temps fluctuated around the 50-degree mark.

Fall N application south of Illinois Route 16 – an area encompassing virtually all of southern Illinois – was not recommended by the ISWS on Nov. 4.

For more information about proper N applications, visit www.KIC2025.org