Update from the Field: Make Data Great Again!
Posted by David Dyson, Agronomist on December 18, 2017
It is beginning to look a lot like “prepay” season, and with prepay comes the inevitable question, “How much nitrogen do you think I need to apply per acre?” Nitrogen rate recommendations for a given field are traditionally linked to historical yield levels. For a field in a corn-soybean rotation, the traditional rule of thumb was a nitrogen rate equal to approximately 1 lb. of nitrogen per bushel of expected yield. For corn following either corn or wheat, the recommendation was equal to about 1.25 lbs. of nitrogen per bushel.
These rules of thumb implied a linear relationship between yield and nitrogen rate. In reality, however, the relationship is nonlinear, or curved. The first pounds of applied nitrogen will return the greatest number of bushels, and the last pounds of applied nitrogen will return the fewest number of bushels. Nitrogen application follows the law of diminishing returns, so at a certain level, grain yield stops increasing with additional pounds of nitrogen fertilizer. Consequently, applying more nitrogen than the crop requires is harmful, both economically and environmentally. Throughout the Midwest, most land-grant universities have moved away from yield based nitrogen rate recommendations toward data-driven recommendations based on field trials.
Dr. Bob Neilsen and Dr. Jim Camberato have conducted extensive data trials across the state of Indiana the last few years. Their conclusions are as follows:
The average Agronomic Optimum Nitrogen Rate (AONR) for 53 trials conducted on medium and fine textured soils in southwest, southcentral, southeast, and west central Indiana was 208 lbs. nitrogen/ac. The average AONR for 30 trials conducted on medium and fine textured soils in northwest and northcentral Indiana was 212 lbs. nitrogen/ac. The average AONR for trials conducted on medium and fine textured soils in other regions of the state were 232, 251, and 263 lbs. nitrogen/ac for central 23 trials, east central (26 trials), and northeast 11 trials Indiana, respectively. The average AONR for 16 trials on non-irrigated sandy soils was 202 lbs. nitrogen/ac.
If you have further questions, please contact one of our ag advisors at The Andersons, or contact me directly at 206-578-4884.
In conclusion, it’s important to run your own nitrogen studies so that you have information specific to your fields. You should start with the nitrogen rate you are currently using, and increase the rate across the field. Dr. Nielsen and Dr. Camberato are always looking to add to their trials, so if anyone is interested in conducting on farm nitrogen rate trials, contact Jim Camberato (765-496-9338 or jcambera@purdue.edu) or Bob Nielsen (765-494-4802 or rnielsen@purdue.edu).
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Dave Dyson is a regional agronomist for The Andersons’ Farm Centers which are located throughout Ohio, Michigan, and Indiana. He is an Indiana native and grew up on a dairy farm in Miami County. A graduate of Purdue University with a degree in Crop & Soil Science, Dave has a deep knowledge of various agronomic topics and is committed to helping growers improve their crops. If you have any questions, Dave can be reached at david_dyson@andersonsinc.com.
References:
Camberato, Jim and RL (Bob) Nielsen. 2014. Corn Stalk Nitrate Tests – Research and Recommendation Update. Purdue Extension. Online at https://www.agry.purdue.edu/ext/soilfertility/news/cornstalknitrate.pdf [URL accessed March 2017].
