## Calculating corn nitrogen needs for late season purchases of inputs

### Corn producers may want to consider using nitrogen rates tied to the maximum return to nitrogen approach.

Since 2009, Michigan State University has been suggesting nitrogen (N) rates based on a system called maximum return to nitrogen (MRTN). Corn yield response for Michigan and other corn-producing states in the Midwest show that the new hybrids are more efficient in utilizing the N for producing grain. One bushel of corn is being produced, on average, with 0.80 pounds N.

#### 1Low: average yield =< 120 bu/a; Medium: average yield = 121-150 bu/a; High = 151-180 bu/a;Very High = more than 181 bu/a [where average yield is the five-year average (disregard unusual highs and lows)].

As producers approach year-end buying decisions, they can access some tools to assist them in their decisions associated with corn N rates. Iowa State University has incorporated Michigan data from the past several years into a model that provides the economic optimum N rate. This corn N rate calculator is found at Iowa State University Agronomy Extension’s Tools webpage.

Producers should project what the potential price might be for N and the corn price to utilize the correct N:corn price ratio. An example using 28 percent UAN prices at \$350/ton is equal to 0.63/lbs. of N and the price for corn at \$5.70 gives a N:corn price ratio of 0.11.

Don’t be caught short of N for your corn crop as shown in the photo below, but utilize the most economical rate to make your farm the most profit.