MRTN — Maximum Return To N

By Harold Watters, CCA, Ohio State University Extension agronomist

Current recommendations from Ohio State University use an economic model to set our corn nitrogen rate. The Maximum Return To N (MRTN) concept was developed by soil fertility specialists from across the north central region as a Corn Belt wide approach to nitrogen rates.

For us we use data from trials in Ohio so we also have our weather included as part of the equation. And we factor in the price of nitrogen and the value of corn to bring in the economics. I see that our best economic return to nitrogen for $3.50 corn (I’m still optimistic) and $0.40 per pound of N is about 168 pounds of N/A. With a range of about 15 pounds to either side giving us about the same economic return — within $1. You may also gain efficiency by delaying the bulk of you N application until side dress timing. From last year’s experience, better put 50 N with your corn at planting for faster recovery after flooding, then sidedress the remainder later.

The Corn Nitrogen Rate Calculator is available on the Iowa State University website: Go there to get the best suggestion on your nitrogen rate, even run some different scenarios. You’ll need to know:

  • Your state
  • Previous crop — corn or soybeans
  • Price of N
  • Expected sales price for a bushel of corn.

The calculator does use Ohio data from recent years from trials on Ohio farms and research sites.


You need weather records to go along with those fertilizer application records

This is a reminder of several good sources of weather information that can be used as part of your fertilizer application records.

  • is the standard, and we have already told you about this one in our fertilizer applicator meetings.
  • From the Ohio Department of Agriculture is the Ohio Applicator Forecast: This works for fertilizer or manure, and gives a 12- and 24-hour forecast.
  • From OSU’s Byrd Polar & Climate Center: This may be the simplest tool to use. It can provide historical data and a seven-day forecast.
  • I like Weather Underground:
  • And there is also a Midwest regional climate center that can be used: is another site that can provide historical forecast data.

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