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Stream and Flat Fan Topdress Application of Urea Ammonium Nitrate in Winter Wheat (Triticum Aestivum L.)

England, Brandon
Changing the application method of nitrogen (N) fertilizer has the potential to increase grain yield in winter wheat (Triticum aestivum L.). The objective of this study was to evaluate the use of streamer nozzle application using urea ammonium nitrate (UAN) versus flat fan nozzle application. The experiment was conducted at the Robert L. Westerman Irrigation Research Station at Lake Carl Blackwell, OK (LCB), and at the EFAW Research Field near Stillwater, OK for two years (2006-2007, and 2007-2008). Additional sites were established in 2007-2008 at the Perkins Research Station at Perkins, OK, and another site at the Robert L. Westerman Irrigation Research Station at Lake Carl Blackwell, OK. The experimental design was a randomized complete block with three replications. Treatments included four N rate combinations applied in three different methods; 1. streamer nozzle topdress application of liquid UAN; 2. flat fan nozzle topdress application of liquid UAN; and 3. granular urea applied to the surface without incorporation. Nitrogen rate combinations were 0 - 45, 0 - 90, 45 - 45, and 45 - 90 kg N ha-1, preplant and topdress application rates respectively. Excessive rainfall in 2007 at both sites resulted in highly variable, and extremely low wheat grain yields (< 700 kg ha-1 in all plots), with a great amount of variation occurring between N rate treatments. The adverse weather conditions resulted in the check plot producing higher yields than half of the other treatments thus restricting proper evaluation of N rates and method of application for this year. In 2008 an increase in grain yields was observed from topdress N application with the streamer nozzle. A benefit was observed from utilizing the streamer nozzle for topdress application at the higher N rate combinations (0 - 90, 45 - 45, and 45 - 90 kg N ha-1) however the increase in yield observed at the highest N rate combination was not significant. A small increase in yield was seen when using the flat fan nozzle over the streamer nozzle at the 0 - 45 kg N ha-1 rate. The benefits of fertilizing with the streamer nozzle tended to be more evident at the middle two N rate combinations (0 - 90 and 45 - 45 kg N ha-1) where N was limiting early in the season.