Top Crop Manager

News Corn Fertility and Nutrients
OMAFRA: Determining your corn MERN

April 25, 2022  By Top Crop Manager

Ben Rosser, corn specialist with Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA), has added another article to his series this spring on corn fertilization – specifically, on optimizing corn N levels while taking into consideration higher-than-usual input costs and uncertain availability.

The essentials growers should know about MERN:

  • MERN stands for the “most economic rate of nitrogen” – the rate that maximizes economic returns on N fertilizer;
  • MERN is influenced most strongly by variability in N response across environments (fields, parts of fields, growing seasons);
  • MERN is also influenced by changes in corn and nitrogen fertilizer prices, but very significant changes in nitrogen:corn price ratios are required to change MERN appreciably;
  • While calculating true MERN requires several N rates and software to fit N response curves, MERN can be estimated on-farm using the two-rate zero-N and N-rich “delta-yield” approach with the N Rate Evaluator tool at

For a more detailed description of what MERN is, how it functions, and how growers can use it to make on-farm decisions, visit the OMAFRA Field Crop News website.



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