Now more than ever, the practice of fall applied Nitrogen is under the microscope in Illinois. Regardless of individual farmer opinions on the matter, the fact is that environmental interests have turned this particular farming practice into a “hot button” issue in Illinois right now. Best Management Practices for fall applied N have been recommended by IL Corn and most farm groups, along with the IL Fertilizer and Chemical Association.

The temptation is certainly there, but the truth of the thermometer remains. It’s too early in the season to apply nitrogen if you’re following best management practices. A quick check of the state soil temperature map shows that nowhere in Illinois were soil temps below the recommended 50 degrees yesterday.

Check the map daily. Use the Daily Maximum 4-Inch Bare Soil Temperature Map (° F) to determine if N application is appropriate. If you’re a land owner, please note that asking your tenants to put on nitrogen early to avoid perceived supply problems puts them and your N providers in an uncomfortable position. Compromising the integrity of the industry at this point could very well compromise fall applied N for everyone in Illinois.

Click state soil temperature map for the latest information on soil temps.

The future of fall applied N in the state of Illinois depends on YOU. Do what’s right.

The IL Fertilizer and Chemical Association recommends using nitrogen stabilizers for ALL fall applied N.

Only apply N when the soil temps are in the low 50’s and the longterm forecast is for sustained cool weather.

If you choose NOT to use an N stabilizer, only apply N when soil temps are below 50 degrees and will stay that way.

The Illinois State Water Survey, through a grant from the Illinois Department of Agriculture Fertilizer Research and Education program, has initiated daily dissemination of maps showing 4-inch bare soil temperatures across the state based on observations taken at selected Illinois Climate Network sites. These data are intended to assist Illinois farmers with timing of post-harvest nitrogen (N) fertilizer application. The information displayed is specifically representative of the actual locations where soil temperature observations are made. Elsewhere, these data should be viewed as a guide to general soil temperatures within a given region, and as indicative of current temperature trends progressing across the state. Farmers and applicators should monitor the soil temperature of each field before fall application of N fertilizer.

Individual daily maps are analyses of the observed soil temperatures across Illinois on the previous day at a depth of 4 inches below a bare soil surface. Figures show:

• soil temperature between 9:00 a.m. - 10:00 a.m. (Central Standard Time) on the previous day

• daily (midnight to midnight) maximum soil temperature on the previous day 

• daily (midnight to midnight) minimum soil temperature on the previous day

Charts will be updated by 4 am each day.

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.