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Nitrogen Application for Spring Wheat and Durum Protein Increase (06/18/15)

Spring wheat and durum is approaching heading. My plots near Lisbon are in the boot stage and will head out in a few days.

Nitrogen Application for Spring Wheat and Durum Protein Increase

                Spring wheat and durum is approaching heading. My plots near Lisbon are in the boot stage and will head out in a few days. The specter of protein dockage and failure to make grade is on many producers’ minds with high yield potential and possible loss of at least some N from the record May rainfall.

                To review options, for yield increase with N, application of streamed liquid N or urea with a urease inhibitor (Agrotain*/Limus* chemistries or something like them) up to jointing stage will result in a yield increase and a slight protein bump. From jointing on, any N applied will go into protein. Any N applied, whether streamed or urea with a urease inhibitor followed by rain is generally not as efficient as UAN or melted urea applied immediately post-anthesis.

                Things to do

                My strongest recommendation for protein increase is to wait until immediately post-anthesis. This is the timing where the main stem and next two tiller anthers are ‘done’ (no longer yellow). Any other lurking tillers are of no yield consequence, so nuking anthers with N application is not an issue. At this stage, apply 10 gallon per acre UAN (28-0-0) with 10 gallon per acre of water, apply during the cool of the day (during hot periods, this means morning between sunup and maybe 10AM. If it’s in the 60’s all day, keep going; if it becomes hot, quit about 10AM.) The application is made with flat fan nozzles pointed downwards. Expect some leaf burn, but this has not resulted in yield decreases in NDSU research trials- and some of the trials burnt the leaves badly. Apparently, the N in the flag leaves was mobilized during heading so that immediately post-anthesis burning is not the issue it would have been earlier. You should expect from ½ to 1% protein increase with this application. If a grower does not realize this increase, it is most likely because S was marginally deficient, or disease interfered with protein accumulation. If some company that can ‘melt’ urea and make a urea solution is in the neighborhood, this liquid urea product usually results in less burn than UAN. I would not mix ammonium thiosulfate with the immediate post-anthesis program. I would favor ammonium sulfate at a low rate (1-2 pounds S max) with the UAN if a grower decides to put on any S at all. Supplemental S should have been applied a couple weeks ago.

                Things NOT to do-

                Do not apply during heading. UAN or fertilizer of any kind will harm sensitive wheat flowers.  Protein increase would be likely, but at the expense of yield.

                Do not use low rates of slow-release N fertilizers. Some salespeople want growers to believe these products are more efficient than UAN so a much lower rate can be used, but all of our research indicates that applied as a foliar to wheat these materials are no more efficient than UAN.

                Do not mix with fungicide at flag leaf. Fungicides are supposed to protect the flag leaf, and adding fertilizer will reduce the leaf surface and is counterproductive to this purpose.

*Use of a product name is not an endorsement of any product.

Dave Franzen

NDSU Extension Soil Specialist

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