Should Nitrogen be Added to Foliar Fungicide Applications to Hard Red Winter Wheat?.

Foliar fungicides can protect winter wheat (Triticum aestiveum L.) grain yield, and wheat farmers sometimes include nitrogen solution with the applications in the hopes that added nitrogen will increase wheat grain protein, yield, or both.  The objective of this study was to determine the effect of various nitrogen fertilizer-by-foliar fungicide combinations on winter wheat normalized difference vegetative index (NDVI), grain yield, test weight, and grain protein. Our hypothesis was that nitrogen products would perform similarly and late-season nitrogen application would increase grain protein but have no effect on yield or test weight.  The experiment was conducted near Lahoma, OK during the 2012-2013 wheat production season. Experimental design was a factorial arrangement of a randomized complete block design with four replications. Treatment responses were evaluated using the SLICE option of the SAS Mixed procedure. Factors were fungicide treatment (no fungicide or 0.77 L ha^-1 Quilt Xcel), nitrogen source (urea ammonium nitrate (UAN) solution or CoRon), and foliar nitrogen rate (0, 2.8, or 5.6 kg ha^-1). A 28 kg ha^-1 UAN treatment was also included. Applying 28 kg ha^-1 UAN significantly decreased NDVI due to leaf burn, and damage was accentuated with foliar fungicide. Neither fungicide, nitrogen, nor their interaction significantly increased grain yield. Test weight was increased by fungicide application regardless of nitrogen treatment, and the largest increase occurred with 5.6 kg N ha^-1 UAN. Wheat grain protein was affected by nitrogen treatment and ranged from 15.9% in the control to 16.7% with 5.6 kg N ha^-1 applied as Coron. Results of this study indicate that including nitrogen with foliar fungicides applied to hard red winter wheat may improve grain protein; however, additional site years of study are needed to determine if this response is consistent across multiple environments.