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Corn growers, forget about "1.2 is all you should do." With nitrogen fertilizer prices pushing record prices of $500 per ton, it's time for a new approach to application rates.

University of Illinois agronomists have been reviewing the traditional nitrogen fertilizer recommendation for months along with cohorts across the Corn Belt.

Combined studies have found that applying 1.2 pounds of nitrogen fertilizer for every anticipated bushel of corn produced generally leads to application of more nitrogen than the corn can efficiently use. And excess nitrogen has been shown to leach out of soil, potentially contaminating surface water.

The new recommendation provides a range of application rates tied to both production practices and nitrogen fertilizer prices.

Or as crop scientist Emerson Nafziger put it - "a rate that provides returns close to the maximum for a given set of corn and nitrogen prices."

If you intend to plant corn following soybeans next spring, the recommendation is to apply between 122 pounds and 162 pounds per acre when corn prices are $2 per bushel and nitrogen costs 30 cents per pound ($492 per ton).

Planting corn following corn? The recommendation changes to 137 pounds to 174 pounds of nitrogen under the same price scenario.

Basically, nitrogen rates drop about 1.5 pounds for each 1-cent increase in the cost of a pound of nitrogen if corn prices stay the same. That translates into about 1 pound of nitrogen per acre for each $10 increase in the cost of a ton of anhydrous ammonia fertilizer, Nafziger noted.

If nitrogen prices remain at 30 cents per pound, corn prices would have to drop by about 33 cents per bushel to decrease the recommended nitrogen rate by 10 pounds per acre.

An exception exists in continuous corn fields where yield expectations would exceed 150 bushels per acre. Nafziger recommended growers boost nitrogen rates on those fields by 0.4 pounds of nitrogen per acre.

Nafziger added that corn growers no longer have to be concerned about giving nitrogen credit for soybeans, which fix nitrogen in the soil through root nodules. The recommendations are based only on trial data from 250 Illinois fields where corn followed soybeans. So, the soybean credit is already included.

Join a nitrogen field test

Even with the new nitrogen application rate recommendation in place, Nafziger said there's a need to learn more about efficient nitrogen use.

More field tests will help fine-tune the recommendation and build more confidence in the new guidelines. So, Nafziger's looking for at least 100 farms to perform field scale nitrogen tests next year.

Nafziger's applied for funding, but he won't know what's available until early spring. Funding would be used to cover any yield losses due to a nitrogen deficiency in low-rate field strips.

Volunteers will have to be able to precisely apply nitrogen and record yields. He'd like at least 80 corn following soybean fields with the rest continuous cornfields. He prefers the fields to have been devoid of manure application for 10 years.

Other stipulations include:

• Trial strips of 12 or 16 rows with at least two border rows on each side.

• Strips measuring [ mile to \ mile long.

• Strips need to be in a uniform field or part of a field in a soil type typical of the area.

• Nitrogen rates will be 0, 50, 100, 150 and 200 pounds per acre.

• Any form of nitrogen and application timing will be acceptable.

• Each rate must be applied to three, separate strips.

If the project sounds interesting and plausible, contact Nafziger at ednaf@uiuc.edu or call (217) 333-4424.

Pantagraph Farm Editor Chris Anderson writes about agriculture every Wednesday. Contact her at canderson@pantagraph.com.

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