Do's and Don'ts of Late Season N in Wheat

Daniel Kaiser and Jochum Wiersma

Looking to improve grain protein in spring and winter wheat? Foliar applications of N during the onset of kernel fill have shown to effectively increase grain protein, but there are a few do’s and don’ts to keep in mind when it’s time to apply.


DO:

• Apply up to 10 gallons per acre of 28-0-0  UAN (30 lbs of N per acre) with an equal amount of water. The water helps to reduce leaf burn.
• Use the Wheat Protein Response Decision Guide (below) to determine the likeliness of crop response and compare to price of UAN. Stick with UAN sources: higher-cost slow release products such as those formulated with methylated urea have not been shown to be more efficient that UAN alone.

DON’T:

• Apply during the heat of the day. Aim for early evening applications to reduce the potential for leaf burn. 
• Tank mix this N with any fungicides at Feekes 10.51 or beginning of anthesis. Instead, apply the additional N 3 to 6 seven days after Feekes 10.51.

Other Considerations

• The probability of a response by the crop is about 80 percent.
• An increase of 0.5 to 1.0 full point in grain protein with the additional 30 lbs N/acre is possible regardless of variety seeded.
• With UAN, expect some leaf burn. Dissolving urea in water to make a urea solution can reduce these effects but is challenging as the reaction of urea with water absorbs heat (endothermic reaction). Be sure that urea is not contaminated with biuret, an impurity in urea-based fertilizer that results from the condensation of two urea molecules. High quality urea will contain less than 0.2 percent biuret.

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Support for this project was provided in part by the Agricultural Fertilizer Research & Education Council (AFREC).