Favorable weather has helped push Illinois harvest progress well ahead of normal, prompting farmers to consider applying fall fertilizers early after fields are clear.

But University of Illinois experts say soils are still too warm for safe, effective fall fertilizer application.

The unusually warm start to fall has caused soil temperatures across the state to remain 5 to 10 degrees warmer than average for this time of year, said Illinois State Climatologist Trent Ford with the Illinois State Water Survey.

Measurements at ISWS Water and Atmospheric Resources Monitoring Program sites show 4-inch soil temperatures under sod have remained in the high 60s to low 70s across the state.

Given these warm soil temperatures, farmers should hold off on fall fertilizer and manure applications for at least two or three weeks since they can be less effective and can harm the environment.

The major concerns, U of I Extension environment and energy stewardship educator Jay Solomon said, are loss of applied nutrients and potential environmental impacts.

“The push for application may be to empty manure storages. However, these warm air and soil temperatures can increase the potential for odor complaints,” Solomon said. “The nitrogen volatilized off as ammonia gas can be a major component of the odor produced during application. Keeping the nitrogen in other forms longer benefits both the crop and the environment.”

The Illinois Agronomy Handbook recommends not applying fall fertilizers until the daily maximum bare soil temperature at 4 inches is below 50 degrees. Above this temperature, the rate of nitrification increases significantly in soils. This chemical change increases the risk of nitrogen losses through gas emissions and leaching with soil water movement before spring crop planting. On average, the last day with maximum 4-inch soil temperatures above 50 degrees is around Nov. 1.

Farmers may be concerned about the potential of less-than-favorable weather for fertilizer application later in the season. But Ford said forecasts don’t show any signs of the potential for problematic weather in the next few weeks.

“Both long-range forecasts and outlooks are leaning to near to above normal temperatures at least through the last week of October,” Ford said. “In addition, forecasts do not show any indication of persistently wet conditions for the second half of October.”

Current soil temperatures across Illinois are available online through the State Water Survey’s Water and Atmospheric Resources Monitoring Program at isws.illinois.edu/warm/soil.

America’s Farmers Grow Communities

Eligible farmers can enroll through Nov. 1 for the chance to direct a donation to a local nonprofit organization, school STEM or youth agriculture program.

The Bayer Fund will double individual donations to $5,000 for 2022, up from $2,500 in previous years, through its America’s Farmers Grow Communities Program.

Since 2010, the program has awarded $60 million to thousands of nonprofits, schools and ag students across rural America, and farmers have played a key role in directing funds to programs and organizations that contribute to their communities.

Farmers are eligible to enroll in the program if they are 21 years old and are actively engaged in farming at least 250 acres of any crop.

Winners will be announced in January.

Enrollment and more information are available online at AmericasFarmers.com and by calling 877-267-3332.

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