Corn Nitrogen Rate Calculator Helps Farmers Determine Fertilizer Needs, Protects Environment

October 25, 2012, 11:53 am | Dustin Vande Hoef, Willy Klein

AMES, Iowa – Iowa State University Extension and Outreach and the Iowa Department of Agriculture and Land Stewardship today highlighted the Corn Nitrogen Rate Calculator available to help farmers find the maximum return to nitrogen fertilizer applications and the most profitable application rate for their farm.

The Corn Nitrogen Rate Calculator can be found at This online tool is rapidly updated to allow for changing hybrid genetics, rotations and climatic conditions. The Iowa database in the calculator was updated in 2012 with 2011 response data and now contains 214 trials for corn following soybean and 111 trials for corn following corn.

“Having adequate nitrogen available is critical for corn production, but given the high prices for fertilizer it is important farmers determine the right amount that is needed on their crops,” Iowa Secretary of Agriculture Bill Northey said. “Every farmer wants to make sure plants have the fertilizer they need while not over applying, so this calculator is a great tool.”

The calculator can be used for both corn and soybean rotations and corn-on-corn operations. It allows farmers to compare up to five price ratios – pricing options for nitrogen and corn. Farmers can reach out to their local fertilizer suppliers to find current fertilizer prices

The calculator then lets farmers determine the optimal rate of application based on up to four different corn prices.

“Nitrogen rates determined by the calculator are the total fertilization amounts for each rotation, there is no need to further adjust rate for previous crop,” said John Sawyer, soil fertility and nutrient management specialist with Iowa State University Extension and Outreach.

Sawyer reminds farmers they should also wait until soil temperatures remain below 50 F before applying anhydrous ammonia (NH3) fertilizer this fall. A statewide real-time soil temperature data map is maintained by ISU Extension and Outreach at and can be used by ag retailers and farmers to determine when fall nitrogen applications are appropriate.


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