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Late Season N in Wheat - The Cliff Notes Edition 2.0

Once again there is here is interest in late-season application of nitrogen with the goal to improve the grain protein content of spring and winter wheat. Foliar applications of N during the onset of kernel fill have shown to be able to increase grain protein.

The key points of foliar applications of N on wheat to improve grain protein content follow:

  • Apply up to 10 gpa of UAN with an equal amount of water - the water is needed to reduce leaf burn.
  • DO NOT apply during the heat of the day - early evening application reduce leaf burn considerably.
  • DO NOT tankmix this N with any fungicides at Feekes 10.51, but rather apply the additional N 2 to 5 days after anthesis.
  • The probability of a response by the crop is about 80%
  • Only expect an increase of 0.5 to 1.0 full point in grain protein with the additional 30 lbs N/A
  • All varieties respond equally well to the additional N
Figure 1. Decision guide for economic return.

Use the decision guide to determine whether an economic return is possibly in relationship to the price of the UAN (Figure 1).  Furthermore, Dr. Dave Franzen's research has clearly shown that product like N-Pact and Coron applied at their recommended, low rates of 1 to 3 gpa near, at or after flowering do not increase grain protein.  

While there is no effect on grain yield, some leaf burn is to be expected when using UAN.  Dr. Dave Franzen also suggests that leaf burning can be further reduced if  urea is dissolved in water to make a urea solution. A word of caution is that the urea to make the solution is not contaminated with biuret. Biuret or carbamylurea is the result of condensation of two molecules of urea and is an impurity in urea-based fertilizers. High quality urea contains less than 0.2% biuret.

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