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In-Season Nitrogen Management

May 19, 2021

By Terry Aukes, CFE Agronomy Sales Manager

As planting comes to an end, we now shift focus to post spraying and in season nitrogen management.  Commodity prices have improved which leaves many growers asking if they were to invest extra resources in their crop where would they look? What would give them the highest return on investment? One data set that drives our decisions at CFE is evaluating the 2020 Answer Plot “Response to” Insights 10-Year Summary on a variety of agronomic decisions, one of which being Response to Nitrogen.

Winfield conducts testing where differences are evaluated between non-limited and limited N applications while rates vary by soil type and location. National Answer Plot summaries are tabulated and in 2020 the yield range was 19.8-97.7 bushels, showing us differences in limited vs non-limited rates of N had on yield. The running 10-year average in 2020 was 66.9 bushels. The reason for such a large range of 19.8-97.7 bu/a in 2020 or any year for that matter is the hybrid-by-hybrid difference. This is a big range! What drives this large variance is the genetic makeup of the hybrid and its response to additional nitrogen or lack thereof. As we evaluate our nitrogen program on a hybrid-by-hybrid basis we need to study what hybrids show a high response to additional nitrogen and adjust the rate accordingly. Another consideration to keep in mind or another way to look at it is the hybrids that show the highest ROI to additional N are certainly hybrids we do not want to be skimpy with rates as they will suffer the most. Using the 10-year summary again, I want to point out the highest response to additional nitrogen was in 2018 at 93.7 bu/a (2018 was extremely wet) and the lowest in 10 years was in 2012 (very dry year) at 54 bu/a. Even in a dry year in 2012 shows hybrid-by-hybrid evaluation by nitrogen is important.

It may be a bit too early to pull LSNT (Late Spring Nitrate Test) but as soon as corn is V5-V8 your CFE agronomists will start pulling samples. We know we have not experienced the heavy spring rains we have had in the past several years, which typically moves Nitrogen deeper in the soil profile, but we also don’t know how much mineralization has occurred from manure and organic matter as it has been a cold spring. We will know more in a few weeks once we start pulling samples. Before then brush up on evaluating each hybrids nitrogen response and be ready to top dress or side dress additional N if need be. A common practice is top dressing urea safened with anvol for volatility protection or using a liquid side dress applicator and UAN injecting with a coulter or knife. In either application, a practice that needs serious consideration is adding additional Sulphur. There is a product called ammonium sulfate 21-0-0-24S used in dry fertilizer applications or a liquid version called ammonium thiosulfate or ATS which is 11-0-0-24S in liquid applications. We have seen great responses not only in yield but plant health with stronger Sulphur rates. I really like top dressing ammonium sulfate (21-0-0-24S) as it is a stabilized form of N already and personally, I would rather invest in the Sulphur than buying anvol. Gypsum is another dry product that contains Sulphur that is PH neutral that can be used.

There you have it folks-you have your homework to do! Work with your CFE agronomist evaluating your nitrogen management program and responses by hybrid to maximize your fertilizer and seed dollars. LSNT soil samples can be used as a tool or resource as well as some nitrogen modeling to aid in the decision-making process.  Finally, determine what form of nitrogen and application method works best for you. Don’t forget the Sulphur!

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