High Prices and High Yields = More Nitrogen?

Greg Stewart, OMAFRA Corn Specialist

The tantalizing yields of the last several years combined with higher corn prices may prompt some producers to unleash high nitrogen
application rates in order to secure maximum yields and maximum profitability. The OMAFRA recommendations for nitrogen on corn are comprised in the Corn N Calculator and they do allow producers to take into consideration several factors including both corn yield and corn price. Using the Calculator will allow producers to examine various scenarios and hopefully select a nitrogen rate that will come close to
optimizing returns.

The N Calculator can be found at www.gocorn.net and can be used straight off the internet, via an Excel version, or you can print a paper document that will allow you to work through various possibilities with a pencil and calculator.

The print out from an N Calculator scenario is featured in Figure 1. The calculator input items are the specific details surrounding this field of corn. It serves as an example of what the calculator might have looked like in the spring of 2006, with corn prices at $2.80 per bushel and nitrogen prices at $.45/lb. In this case, the total N recommendation is for 106 lbs N/acre. The farmer intends on placing 25 lbs of starter
down with the corn planter and sidedressing the remainder. After taking into consideration an efficiency adjustment for sidedressing, this amounts to 65 lbs N/acre. The 2007 version of this same field might well be altered (thankfully!) by inserting $4.25/bu as the selling price. This is especially the prudent thing to do if you have already forward contracted the corn from this field at this price. When we plug in the higher corn price, the Calculator will come back with a recommendation for 79 lbs of sidedress N after placing the same 25 lbs/acre via the starter. This is a no-brainer. As the ratio between corn price and N price improves, producers will want to, and can afford to apply more N in order to push closer to the maximum yield potential for the field. But notice that the research data that went into the calculator does not
support a huge increase in N rates; it is a fairly modest increase (14 lbs N/acre) for a price change of $1.45/bushel, with N prices held constant.

The other possibility that we will consider is the yield expectation from the field. Given very high yields for the last two years it will be normal for most growers to be optimistic about the 2007 yield expectations. If we altered the yield expectation from 145 to 175 the calculator will call for an additional 18 lbs of sidedress nitrogen. It is appealing to apply this “insurance N” every year just in case yields soar as they did in 2006. We have tested this concept on various multi-year data sets to see if in the long haul we could make more money by adding 20-30 lbs/acre extra nitrogen, every year, over what the calculator called for. The answer has been quite clear – NO! I liken it to buying tickets for the fourth game of the Stanley Cup Finals if you are a Toronto Maple Leafs fan! Some day it will pay off, but it costs you too much in the process. However, I am all for being reasonably optimistic as you enter yield expectations for a given field. Consider what the last five to eight year average has been, and make some upward adjustments if the soil is in good shape for 2007, if you get it planted early, and for the genetic gains
that come from your careful hybrid selection.

The calculator will not always be a bull’s-eye in terms of your nitrogen needs. And we continue to test it and look for additional research data that will allow us to improve it in the future. For now, hopefully it provides good guidelines for producers to target the most economical N rates for their various corn cropping scenarios.

Figure 1. Sample printout for a nitrogen rate determination by the Nitrogen Calculator.