Yield and quality improvements from the late‐season UAN spraying of winter wheat cultivars differing in grain protein concentration

Abstract Wheat ( Triticum aestivum L.) producers need to know whether a late‐season urea ammonium nitrate (UAN) application is effective in improving grain protein concentration (GPC) in high‐yielding environments. Field experiments were conducted over 3 years to evaluate the effect of UAN on awned cultivars Bologna and SY‐Moisson, differing in GPC. Crops were grown under standard nitrogen (N) fertilization practice with and without UAN application. UAN solution (32 kg N ha −1 ) was sprayed midday at anthesis with no leaf burn afterward. Average grain yield (9110 kg ha −1 ) and GPC (113 g kg −1 ) were similar across growing seasons. Compared to non‐treated plots, UAN application increased flag‐leaf greenness, which was more evident toward the end of grain ripening. UAN‐treated crops consistently produced higher yields than the non‐treated control (on average by 382 kg ha −1 ) primarily due to heavier grains. The GPC averaged 122 g kg −1 for Bologna and 104 g kg −1 for SY‐Moisson. Increases in GPC following UAN application were higher in Bologna (9 g kg −1 ) than in SY‐Moisson (5 g kg −1 ). However, yield increases were slightly larger in SY‐Moisson than in Bologna so that cultivars recovered a similar amount of grain N (18 kg ha −1 ) added with UAN treatment. Foliar UAN application had no effect on Hagberg falling number but increased test weight and Zeleny sedimentation in addition to the farinograph and extensograph traits. Increases in wet gluten content after UAN spraying were consistent for SY‐Moisson only. Late‐season UAN treatment improved wheat yield and milling and bread‐making quality, with cultivar‐specific increases in GPC.