By TIM ALEXANDER
Illinois Correspondent

CHAMPAIGN, Ill. — Illinois’ state climatologist says the soil in Illinois does not generally cool to temperatures conducive for fall nitrogen applications until mid-November.

“The short answer is that you can begin applying N when the four-inch bare soil temperature reaches 50 degrees,” said Jim Angel, of the Illinois State Water Survey. “Normally, the four-inch soil temperature drops below 50 degrees by November 10 in northern Illinois, and as late as November 18 in southern Illinois. But those are just averages.”

Actual dates can vary from year to year, said Angel, with factors such as soil color, soil moisture and crop residue modifying soil temperatures between and even within individual crop fields. He declined to predict when soil temperatures may cool to a consistent 50 degrees this fall.

“Unfortunately, there is no ‘forecast’ of soil temperatures,” he said. “However, it’s going to have to get a lot cooler than this for those soil temperatures to start dropping. The mean daily air temperature has to drop below 50 degrees for several days, for this to occur.”

Angel posted his thoughts on fall N applications on his blog at http://climateillinois.wordpress.com and daily soil temperatures for Illinois can be found at www.isws.illinois.edu/warm/soiltemp.asp