Cold, hot, dry, wet, early, late — six words that both summarize and demonstrate the variability in spring planting conditions for the last several Michigan cropping seasons. Though uncertainty with spring weather may always exist, resources are available to reduce grower uncertainty when selecting corn nitrogen (N) rate applications.
Iowa, Illinois, Indiana, Michigan, Minnesota, Ohio and Wisconsin have adopted the Maximum Return to Nitrogen (MRTN) corn N recommendation system.
The MRTN system was adopted to further enhance farm profitability by maximizing the economic return of N fertilizer invested while simultaneously addressing some of the negative environmental consequences that occur when applying excessive N rates.
The system provides a range of N rate recommendations based on many years of corn yield data from N response trials conducted exclusively across a range of soils. What the MRTN system also recognizes and accounts for is that the most economically optimum N rate will never be a constant measure as both corn and fertilizer prices will fluctuate over time. The system provides a profitable range of N rates that allows for user input to adjust N rates based on crop rotation, soil productivity potential and current price of N fertilizer and corn grain.
The MRTN recommendation table is a summary of results from the Michigan database within the Corn Nitrogen Rate Calculator. Both tools may be accessed via the Soil Fertility and Nutrient Management Program website at Michigan State University.