Soil temperatures in Illinois were 1 to 2 degrees above normal in mid-October, according to Jennie Atkins, Water and Atmospheric Resources Monitoring Program manager at the Illinois State Water Survey, Prairie Research Institute, University of Illinois.

Warm soil temperatures mean farmers need to hold off on fall anhydrous applications, says Dennis Bowman, University of Illinois Extension educator. “The key with fall soil temperatures is monitoring them before fall anhydrous applications,” he explains.

WAIT FOR RIGHT TEMP: Statewide soil temperatures under bare soil at a 4-inch depth averaged 57.7 degrees F on Oct. 14. Dennis Bowman, University of Illinois Extension educator, says farmers need to wait for consistently cooler soil temps before applying fall N.

Soil temperatures dropped by 8 degrees during the first two weeks of October, but remained above normal.  Statewide soil temperatures under bare soil at a 4-inch depth averaged 57.7 degrees F on Oct. 14. 

“It will take us a while to get those soils cooled down consistently enough to apply nitrogen,” Bowman says. “We just want to make sure everybody is patient.”

The Illinois Fertilizer and Chemical Association reminds all farmers to think about the 4 R's before applying fall nitrogen.

What are the 4 R's? Applying nutrients at the right source, right rate, right time and right place.

The IFCA offers its 4R best practices for fall nitrogen applications:

• Wait to apply anhydrous ammonia until the daily maximum soil temperature under bare soil at a 4-inch depth falls to 50 degrees F at 10 a.m. 

• Use an approved nitrification inhibitor at the appropriate rate. 

• Do not apply fall anhydrous on poorly drained soils, soils with excessive drainage, soils low in organic matter content, sandy soils, or soils that cool down late or warm up early.

• Review the Maximum Return to Nitrogen Calculator at cnrc.agron.iastate.edu and talk to your crop adviser to determine your optimum nitrogen rate. 

• Consider splitting nitrogen applications to reduce potential loss in the spring.

• And finally, when soil temperatures cool down and snow falls, avoid spreading fertilizer on frozen or snow-covered soil.