Update from the Field: Up in Smoke
Posted by David Dyson, Agronomist on December 11, 2017
Last week at the Fluid Fertilizer Foundation meeting, I had a discussion with a couple of colleagues about fall nitrogen application. The discussion centered on the pros and cons of different types of nitrogen being applied in the fall. One group liked urea (46%) and UAN 28% for the safety and convenience of application. I tend to favor the ammonia forms of nitrogen: anhydrous ammonia (82%) or aqua ammonia (24.5%). My colleagues could not understand why I favored these more “dangerous” forms of nitrogen. I reminded them that while they may be more dangerous to the applicator, they are much more stable in the soil.
Not all fall-applied nitrogen sources are equal. Fall-applied anhydrous ammonia and aqua ammonia behave very differently when compared to fall-applied urea. Anhydrous ammonia and aqua ammonia are as harmful to microorganisms as they are to people, so the microbes that convert ammonium to nitrate in the soil are typically killed in the area right around the injection band. These microorganisms will eventually recolonize the injection zone, and ammonium will begin its conversion to nitrate (Figure 1). Urea does not inhibit the activity of these microorganisms. As a result, anhydrous ammonia delays the conversion to nitrate by at least two weeks when compared to urea and other fertilizer forms. This is commonly referred to as the natural N serving effect. Farmers can lengthen the stability and prevent nitrogen loss by the addition of DowDupont®’s N-Serve® at a rate of 1 quart per acre. Alternatively, the farmer can add DowDupont’s Instinct® HL to aqua ammonia at a rate of 24 ounces per acre. At The Andersons, we are experimenting with adding UltraMate® LQ to aqua ammonia in the fall, spring, and at sidedress to see if we can prolong the conversion of ammonium to nitrate well past the vegetative stage. Early trials look promising.
With the wetter than normal fall we just experienced and the forecast of a wetter than normal winter, many farmers have asked if they have lost all the nitrogen they just applied this fall. I typically answer their question with another question: Did you add a nitrogen stabilizer to your fall application of nitrogen? If the answer is yes, the farmer can rest assured the nitrogen is still in their fields. I have worked with fall applied anhydrous ammonia and aqua ammonia for 17 years, some of which had wet falls and winters, and some of which had dry falls and winters. I always have clients who worry about investing in fall applied ammonia. To ease their minds, I like to run a PSNT (pre-sidedress nitrate test) when the corn is between V2 and V6. As long as the test shows a nitrate level of 26ppm or greater, the field will have sufficient nitrogen to finish out the crop (Figures 2 & 3).
In conclusion, fall applied nitrogen can save time and money. The trick is to use the right forms and add a good nitrogen stabilizer to your fall application.
Figure 1: Nitrogen Cycle
Figure 2: Indiana's NO3 Chart
Figure 3: Michigan's NO3 Chart
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Dave Dyson is a regional agronomist for The Andersons’ Farm Centers which are located throughout Ohio, Michigan, and Indiana. He is an Indiana native and grew up on a dairy farm in Miami County. A graduate of Purdue University with a degree in Crop & Soil Science, Dave has a deep knowledge of various agronomic topics and is committed to helping growers improve their crops. If you have any questions, Dave can be reached at david_dyson@andersonsinc.com.
Source: https://www.protectyournitrogen.ca/en/faq/happens-applied-nitrogen/
UltraMate is a registered trademark of The Andersons, Inc. DowDupont, Instinct, and N-Serve are registered trademarks of The Dow Chemical Company.
