In 2016, 60 farmers participated in the NREC funded Nitrogen Rate Trials. These farmers worked in concert with their ag retailers and with Dan Schaefer of IFCA to incorporate replicated nitrogen rate trials in their fields using nitrogen rates from 0 to 250 lbs of nitrogen and nitrogen timings that included fall, spring, post-application and late season nitrogen treatments.
Dr. Emerson Nafzger at the University of Illinois designed the protocol for the trials to ensure consistency of the various nitrogen timings and treatments; he also provides the analysis of the trial results post-harvest. Dr. Nafziger incorporates this constant stream of new data into the Maximum Return to Nitrogen (MRTN) calculator to ensure that Illinois farmers have access to the best available science when making nitrogen rate decisions for their crop. The MRTN is a key activity in the Illinois Nutrient Loss Reduction Strategy.
Dr. Nafziger recently published an analysis of the 2016 N rate trials, and the November 14, 2016 University of Illinois Bulletin on this subject can be accessed in its entirety at http://bulletin.ipm.illinois.edu/?p=3752 . The key takeaways are:
- Most N Rate Trials showed considerably less N was needed in 2016 compared to 2015. This may reflect both the large supply of N from mineralization of soil organic matter under the favorable environmental conditions of May and June, and also the drier June this year that limited N loss and root damage. (See graph of N Rate Trial from DeWitt County).
- More of the N needed by the 2016 corn crop was taken up by the time of tasseling compared to 2015. Yields were similar in both years, so having more N taken up by tasseling did not clearly lead to higher yields.
- Those who added N in late vegetative stages this year in addition to normal N rates applied early in the growing season might well have ended up with more soil N than usual after harvest.
- Dan Schaefer sampled soil for N at the time of crop maturity and nearly all showed soil N levels less than 6 or 7 ppm, which is considered to be baseline. Low soil N levels are also observed in the UI N-Tracking trials which are also funded by NREC.
- The only place where elevated N levels are being observed after crop maturity is where applied N rates were considerably higher than those needed to maximize the yield. Using too much N is never a good idea, and that was especially true in 2016.
Note: In December 2015, IFCA will post results of the 2016 N Rate Trials at ifca.com under “Keep it 4R Crop Tools. Presentations by Dr. Nafziger and Dan Schaefer are scheduled for January 17, 2017 at the IFCA Convention in Peoria, IL.
In looking ahead to the 2017 crop and making nitrogen rate decisions, Dr. Nafziger states:
“We can think of no good reason to adjust N rates, unless you are planning a rate that is substantially higher than the 175 (155 in Northern Illinois) and 210 lbs per acre calculated by the MRTN for corn following soybeans and corn following corn, respectively, in the region of Illinois where fall N is used. If you are planning a higher rate than this, a downward adjustment is in order. We never know what spring will bring, but it makes more sense to react to loss conditions if they occur than to apply more N “just in case.”
One final piece of advice from Dr. Nafziger to maximize return on your nitrogen investment and reduce the chance of nutrient loss:
“Base N rates on the N rate calculator, which is based on research showing what rate can be expected to maximize profit. And then apply N responsibly in order to minimize N loss and to keep N for the crop.”
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