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Agronomy Update

E. Indiana and Ohio: Sidedressing and Nitrogen Rates in Corn

Published on Wednesday, May 28, 2014

Do I use a nitrification inhibitor while sidedressing corn?
Many growers are or will be sidedressing corn shortly. One question we often get this time of year is, “Do I use a nitrification inhibitor?” As is often the case, it is not an easy answer. The probability of response depends on many factors including soil type, drainage, tillage, form of nitrogen (N) used, and weather.

Here is a list that will provide the greatest chances for crop response to a nitrification inhibitor:
--- Poorly drained soils - With poorly drained soils the chance of denitrification is higher, increasing nitrogen loss. Therefore applying an inhibitor can keep nitrogen in the ammonium form a little longer.

--- Sandy soils - Sandy soils or lighter soils increase the probability that nitrogen will be leached from the root zone so nitrification inhibitors often help in this situation.

---No-till - Corn planted into no-till situations have generally seen the greatest response to nitrification inhibitors (especially preplant). Acccording to the National Corn Handbook, 82 percent of studies have shown a positive increase with an average yield bump of 13 percent.

--- Dribbling UAN or spreading urea on the surface - A certain percentage of UAN and urea can volatilize, especially if there is not a rainfall event soon after application. If UAN or urea are applied to the surface, you have a better chance of seeing a crop response with inhibitors.

--- Sidedress corn early - The earlier you sidedress corn the greater the probability of response. If your corn is at the V2-V3 stage, then (N) inhibitors have a greater chance of paying off since very little nitrogen has been taken up at this time. If you wait until the V5-V8 stage, corn will actively be taking up between 4-8 lbs of (N) per day and inhibitors probably won’t provide a return.




--- Heavy rainfall soon after application - Storms pop up all the time in Ohio and Indiana. If we get a heavy rainfall soon after application, the chance of seeing a crop response is greater. The opposite can be true, however. If we turn dry and (N) is kept in the upper portion of the soil profile (because of the inhibitor) there can be a yield loss.

Most farmers want to know that they will get a return on any input they put into the crop. Although nothing is guaranteed, these are the situations I believe will provide a higher chance of response. Even if you don’t see a yield response, there is research from Indiana that indicates better standability with N inhibitors. 




What is the optimum nitrogen rate in corn?
Beck’s Practical Farm Research (PFR)® has been conducting nitrogen (N) rate studies for the past five years. Over this period they have found that the Economic Optimum Nitrogen Rate (or rate that maximizes profitability for a given cost of (N) and price for corn) is about 178 lbs./A. for corn after soybeans and 212 lbs./A. for corn after corn. Corn after corn needs more (N) because the corn stalks and the microbes that break it down will compete with the current corn plant for (N).

The (N) needs from these studies are a good starting point. You may want to increase the (N) rate if you have poorly drained soils, low organic matter (OM) soils, or low fertility levels. In general, the better your soils are the less nitrogen you need. Why? There is approximately 1000 lbs. of organic (N) in your soils for every one percent of OM. In any given year between one to six percent of that organic (N) will be mineralized - this is dependent on temperature and moisture. If a 3 percent OM soil mineralizes 6 percent of its organic (N), you can get close to 180 lbs. of (N) from your organic matter. In addition, when you have well balanced fertility in your soils the corn plant will actually utilize less (N).

In a year like 2013, where we had plenty of moisture, more (N) was mineralized and we had yields well above what we expected from the amount of (N) applied. In a dry year, like 2012, very little (N) was mineralized and our plants showed (N) deficiency.

Beck’s has also done research on hybrid responses to (N) utilization. There have been certain hybrids that have shown a consistent response to split applications such as BECK 6077AM and 6272HR, while other hybrids may vary from year to year. Generally speaking, there is not a disadvantage to split applications, but you may not always see a large crop response. Talk with your Seed advisor or dealer to see if there is information on your hybrids. If you have Beck’s Hybrids 2013 PFR book the information can be found on page 266. You may also access the PFR book online by visiting

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Mark Apelt

Mark Apelt

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