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Fertilizer Decisions for 2022

With high costs of fertilizer this coming year, it might be a good time to reevaluate your fertilizer application rates.

Nitrogen is a significant part of the variable costs for corn production. In the past people have said that a general rule of thumb is that you should apply a pound of nitrogen for every bushel of expected yield. But the relationship between nitrogen and corn yield is not a linear relationship. At a certain point you will start getting a smaller yield response from each additional unit of nitrogen and this will eventually decrease to zero response to additional nitrogen.

Researchers at Purdue have been doing field trials throughout the state to determine optimal nitrogen rates. The optimal rates will vary by year and soil types. Depending on the weather, some soils can provide a significant source of nitrogen for corn production. Through the years of these trials, they have come up with recommendations for different regions of the state. For sandy non-irrigated soils, the nitrogen rate to produce the highest yield would be around 211 pounds per acre of nitrogen.

But most farmers are more interested in making a profit rather than getting the highest yield. Given the reduced yield response of nitrogen at higher rates, those extra bushels of corn have much higher costs. To determine what nitrogen rate will have the highest profit, we need to look at the price of nitrogen and corn. So, if your nitrogen price is $1.00 per pound and corn is selling for $5.00 per bushel, the rate to get the highest profit would be 159 pounds per acre. This will not produce the highest yields, but should have the highest profit.

Purdue has been doing these trials throughout the state since 2006 and they frequently update the recommendations. You can find the report here:

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