University of Illinois Extension – Bureau, LaSalle, Marshall, Putnam Unit and Russ Higgins, University of Illinois Extension Commercial Agriculture Educator, shares the following for consideration by farmers and producers for spring planting:

Should I increase my Nitrogen rate? 

Spring-like days have brought excitement to the farming community. Equipment is being readied for the planting season and field decisions are being finalized. One of those decisions is the nitrogen rate for corn production. In Northern Illinois, total per acre fertility costs are projected at $132 for corn after soybeans and $142 for corn after corn according to data generated and shared on farmdoc, 2021 Crop Budgets for Illinois.

Fertility is the largest individual direct cost for corn production. These projections were generated with $4.00 corn. With current corn prices above $5.00 per bushel, could we apply more fertilizer, especially nitrogen?

            The answer is yes, but it is likely less than you think. Before ordering an extra 30 to 40 pounds of nitrogen, let’s look at the Nitrogen Rate calculator or MRTN.  Most are familiar, but a quick backstory on the MRTN (Maximum Return to Nitrogen) development. Seven states – Minnesota, Iowa, Wisconsin, Illinois, Indiana, Michigan, and Ohio – currently use this approach. The calculator uses the trial data from each state or each region within a state, and for trials with corn following corn and corn following soybean to produce MRTN values and ranges. Illinois is divided between Northern, Central and Southern regions. For Illinois, the calculator runs on data updated annually; we add new data and selectively remove data from older studies. This approach is an economic one and requires the user to enter expected prices for marketed corn and nitrogen source and expense. With higher corn prices or lower nitrogen costs, you would expect a higher MRTN in a field. Remember, along with the MRTN value is a range, typically about 15 pounds of N on either side of the MRTN. We realize farmers have a better history with their fields and can selectively pick and choose those that may benefit from nitrogen levels on the higher or lower side of that range.

Let’s run several scenarios and see where we are. I’m using Anhydrous as my nitrogen source at $550 per ton or 34 cents per pound of N. For sake of an extreme comparison I’m using last falls expected corn price of $3.75 per bushel and (perhaps overly optimistic, but we were there earlier in the year) a 2021 corn marketing price of $5.50 per bushel. For corn following soybeans the MRTN at the lower market price was 174 pounds of nitrogen and a suggested range of 157 – 191 pounds per acre. When we increase the corn market price to $5.50, the MRTN climbs to 192 pounds of nitrogen and a suggested range between 176 and 206 pounds of nitrogen per acre. What about corn following corn? Our research tells us that corn on corn requires more nitrogen. Using the same nitrogen source and prices as before, corn on corn marketed at $3.75 has a MRTN of 205 pounds and a range of 190 to 223 pounds per acre. Increasing the market price to $5.50, the MRTN climbs to 224 pounds of nitrogen and a suggested range of 207 to 234 pounds per acre. As we just illustrated, at a most optimistic level, our suggested increase in nitrogen rate was closer to 20 pounds, and with current fall prices offered, is likely closer to an increase of only 10 pounds. The take home message? We may justify a slight increase in nitrogen rate to get a few more bushels, but don’t go overboard.

 Spend some time inputting your actual costs and tailoring this helpful online tool for your operation. . Wishing all a safe and prosperous growing season in 2021.

If you have questions or need more information, Russ Higgins, and Daryle Wragge, Agriculture Program Coordinator, can be reached by calling University of Illinois Extension- Bureau, LaSalle, Marshall, Putnam Unit Office at 815-224-0889.

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