By Nick Paulson and Gary Schnitkey
The ongoing conflict with Iran has resulted in significantly higher nitrogen fertilizer prices as damaged energy infrastructure and closure of the Strait of Hormuz has created supply chain bottlenecks (see farmdoc daily articles from March 17, March 23, March 24, and March 27, 2026). Nitrogen fertilizer prices have been slowly increasing since the fall, but those increases have escalated sharply since the conflict began. Price increases since late February have ranged from 20-25% for anhydrous ammonia to more than 40% for urea at locations in the Corn Belt region of the US (see slides and video from farmdoc webinar on March 26, 2026) .
Corn prices have increased as well but not as much as fertilizer prices. As a result, recommended nitrogen application rates are lower under current pricing conditions compared with last fall. For farmers who apply a portion of their nitrogen in the spring, reducing remaining nitrogen applications to be more in line with the Maximum Return to Nitrogen (MRTN) rate recommendations would be highly advised to avoid unnecessary costs and maximize returns. This is particularly true for situations where spring nitrogen needs were not priced prior to the price increases experienced since the start of the conflict in Iran.
What is the MRTN?
The MRTN calculator was developed and continues to be maintained by University soil fertility specialists from states in the Corn Belt region of the US. The calculator uses results from research trials and provides rate recommendations which maximize the economic return to nitrogen. The recommendations are specific to location or region, crop rotation, and the prices for both corn and nitrogen. Users can use the calculator to provide a recommendation based on a single set of prices or use the multiple price mode to look at different scenarios for corn and nitrogen prices to compare recommendations.
For Illinois, N rate recommendations are provided for three regions (northern, central, and southern) for corn following soybeans and for two regions (northern and central) for corn following corn. The rate recommendations will also vary based on the prices provided by the user for corn and nitrogen.
Four common nitrogen fertilizer products can be selected with prices for those products entered as quoted and then converted to $/lb of N by the calculator. Users can also enter prices in $/lb of N directly.
Based on these inputs, the calculator provides a recommended rate – the MRTN – that maximizes the farmer’s return to nitrogen. It is also important to note that the MRTN recommendation accounts for all potential sources of applied nitrogen. Producers should consider the nitrogen contributions from other sources such as manure, DAP, and MAP. Higher nitrogen prices will result in lower MRTN rates holding the corn price constant. Higher corn prices will result in higher MRTN rates holding the fertilizer price constant.
Source : illinois.edu