With supply chain disruptions and global events over the past year, one question floating around winter 2022 has been “if we aren’t 100% certain today that we can source all the nitrogen (N) fertilizer we normally would, what are the risks if we don’t apply our normal N program in corn?”.
If you are in the uncertainty camp, perhaps you are weighing whether:
- corn acres stay at original intentions, but under the risk of uncertain final N supply and rates
- corn acres are reduced as a hedge to ensure that acres planted will have relatively normal N supply and rates.
Yield Risks for Underapplying N
What are the risks for underapplying N? To provide some insight, I will use a 2011-2014 N response dataset from 15 trials conducted on-farm across parts of Southern Ontario by former OMAFRA corn specialist Greg Stewart.
These N response curves (Fig. 1) include the Most Economic Rate of Nitrogen (MERN) for what might represent a:
- 10-year average cost/price scenario (green dot, $5.00/bu corn and $0.60/lb-N fertilizer)
- 2022 cost/price scenario (red circle, $6.75/bu corn and $1.20/lb-N fertilizer)
For more background on MERN, see the article “Understanding MERN (Most Economic Rate of Nitrogen) for Corn” (Rosser, 2022b).
Yield risks for underapplying N in this dataset can be made by comparing yield loss for these curves as N is shorted below MERN. Since most on-farm N rates are likely selected to not limit yields in most years, I will compare yield declines as N rates are shorted relative to the longer term 10-year average MERN (green dots).
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