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College of Food, Agricultural, and Environmental Sciences


New Extension Tool Helping Farmers Save on Fertilizer

August 29, 2007

WOOSTER, Ohio -- A new economic tool, developed by Ohio State University Extension, is changing the way corn farmers manage their fertilizer inputs -- and helping them save money in the process.

Known as a nitrogen rate calculator, the free program (accessed from calculates optimum nitrogen rate recommendations through average corn yields and using only two inputs: the price of corn at harvest and the cost of nitrogen at application.

Robert Mullen, an OSU Extension fertility specialist with the Ohio Agricultural Research and Development Center, said the goal is to apply the minimum nitrogen needed for maximum yield results, thereby saving farmers money on fertilizer applications.

"The tool is part of a new nitrogen application program that is slowly replacing old recommendations that based fertilizer inputs on yield potential. That is, if a grower wanted 150 bushels per acre, he would apply the maximum nitrogen needed to get those 150 bushels," said Mullen. "However, through years of research we found no correlation between nitrogen applications and yield. That is, you eventually reach a yield ceiling and applying more nitrogen doesn't necessarily mean you'll get more yield, and it could also mean that you could apply less nitrogen to achieve the same yield. So we figured with the way nitrogen prices are today, considering the economics was timely."

Under the new recommendations, nitrogen application is based on average yield responses -- much of it already calculated by Mullen through nitrogen rate studies at 70 locations. So, for example, if nitrogen is 40 cents per pound and the price of corn is $4 a bushel, the best nitrogen rate would be 156 pounds for corn following soybean, with an application range of 150 to 180 pounds. As the cost of nitrogen or the price of corn changes, the economic optimum rate of nitrogen also changes.

"The beauty of the system is that it doesn't matter what region of Ohio you are growing corn, the nitrogen rate will be the same, indicating that the weather is the biggest variable," said Mullen.

Mullen and his colleagues have been educating Ohioans about the new nitrogen recommendations for the past year and a half and have received positive responses.

"Farmers are appreciative of our efforts. This new approach makes sense to them," said Mullen. He pointed to a survey conducted during the Conservation Tillage and Technology Conference, an annual event in Ohio that targets farmers from Ohio, Indiana and Michigan.

Based on survey results, 65 percent of respondents stated that they planned on reducing their nitrogen rates. Those respondents tend 5 million acres throughout the tri-state region.

"If nitrogen rates were reduced on just half of those acres, that would mean 60 million pounds less nitrogen added, translating into a $24 million annual savings in nitrogen costs," said Mullen.

All land-grant universities in the North Central region are moving toward a similar basis for generating nitrogen recommendations, he said.

Candace Pollock
Robert Mullen