Ohio State University corn nitrogen rate recommendations follow a unified framework used throughout the Corn Belt. Together with six other states (Iowa, Illinois, Indiana, Michigan, Minnesota, Wisconsin), the Ohio recommended nitrogen rates are not based on yield goals, but on economic returns. Corn yield responses along with corn and nitrogen prices are used to calculate the point at which the last unit of added nitrogen returns a yield increase large enough to pay for the added nitrogen cost. This approach, called the maximum return to nitrogen (MRTN), is favored because of the economic volatility in both corn grain and nitrogen fertilizer prices. The past 10 years provides ample evidence of these fluctuations.
The MRTN interface requires 3 inputs: i) the previous crop grown (corn or soybean), ii) price of nitrogen fertilizer, and iii) price received per bushel of corn. When corn prices are low, nitrogen rates will be reduced; when corn prices rise, recommended nitrogen rates will increase. Similarly, the model responds to nitrogen prices, recommending high nitrogen rates when nitrogen costs are low, and reduces rates when costs are high. The model is housed on an Iowa State University website coordinated by Dr. John Sawyer, but each state provides their own yield response data and some support for website maintenance and updates. When a user selects Ohio as a state, they will only find data collected from trials in Ohio. The tool can be found here: http://cnrc.agron.iastate.edu
Previously there were 116 trials from Ohio (80 trials with corn after soybean, and 36 trials with corn following corn). After this major update, there are now 281 trials in the database (228 trials after soybean, 53 after corn). This database update is part of the comprehensive revision of the Tri-State Fertilizer Recommendations, with major support from the Ohio Corn and Wheat and the Ohio Soybean Council. With help from farmers, Ohio State University extension county educators and numerous private crop consultants, we conducted 56 nitrogen rate trials over 20 counties across the state from 2015-2017. Additional trial data came from OSU extension and from the Adapt Network project, coordinated and supported by the Environmental Defense Fund. These data trials were all independently analyzed and vetted before inclusion into the database. This represents a tremendous collective effort and countless hours of work by many committed professionals working toward a common goal. The recommended nitrogen rates can be found in the table below.
Recommended nitrogen rates (lb nitrogen/acre) for corn following soybean, based on price of corn grain and nitrogen fertilizer.
Additional analyses are now being conducted to look at trends with soil type and regions in the state. We’ll see if it is justified to split the state up into separate regions.
Selecting rates to maximize profitability and not yield can be a difficult mindset for the farming community to break. Farmers love reporting big yields from their fields. However, we need to understand that maximizing yields usually translates into reduced profits and greater nutrient losses from the field. Now more than ever, we as a farmer community need to continue to proactively address water quality issues in the state. We trust that farmers and retailers can use this information to look past maximum yield and a reduced bottom line, and instead choose profitability and sound nutrient management when selecting how much nitrogen to apply to their corn crop this season.