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.
1 Low: 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.