Evaluation of Foliar UAN Rate and Application Timing on Wheat Grain Yield and Protein.

Several studies have investigated the effects of foliar nitrogen timing on grain yield and protein in hard red winter wheat (Triticum aestivum), yet results remain inconclusive. The objective of the present study is to evaluate grain yield and grain protein response to foliar nitrogen application. The trials were planted in 2014 at four research stations in Oklahoma. Urea ammonium nitrate (UAN) mixed in a 1:1 solution with water was applied at two growth stages. Four separate treatments consisted of three rates of nitrogen (14, 28, and 40 kg N ha^-1) applied at first hollow stem and 14 Kg N ha^-1applied at the flag leaf stage. A control plot (no N applied) was also evaluated. Normalized difference vegetative index (NDVI) sensor readings were collected throughout the growing season. Nitrogen content in the grain will be determined using a LECO dry combustion analyzer from grain subsamples collected at harvest.

Expected Results: There was no recorded leaf burn from foliar N applied with flat fan nozzles at first hollow stem or flag leaf growth stages. Grain yields are expected to increase with increasing rates of foliar nitrogen at first hollow stem.  Nitrogen applications applied at the flag leaf stage are expected to increase grain protein.