Optimum nitrogen rate and placement in hard red winter wheat (Triticum aestivum L)

Nitrogen use efficiency (NUE) in cereal crops is at 33% on a global scale. Winter Wheat (Triticum aestivum) is one of the major cereal crops being affected by low NUE. Winter wheat is grown across the United States and the world alike and nitrogen is one of the most applied plant nutrients to winter wheat. With great abundance and low world efficiency rates, the need for increasing NUE is paramount. This study looked at varying nitrogen rates, their placement mid-season, and their effects on grain yield. Actual application took place between Growing Degree Days (GDD) greater than zero (GDD > 0) of 90 and 110 to supply the plant with the precise amount of nitrogen needed before its largest vegetative growth stage. The study was conducted in 2020 at four locations across Oklahoma: Lahoma, Hennessey, Perkins, and Stillwater. All studies employed a randomized complete block design with Urea Ammonium Nitrate (UAN) (28-0-0) as the only nitrogen source used. Placement of the UAN was varied between surface applied and sub-surface applied, nitrogen rates varied between 0 kg/ha to 168 kg/ha. Results of this study were mainly inconclusive to the hypothesis that mid-season subsurface applied UAN would yield higher than surface applied UAN at similar N-rates. The supporting optical sensor reading data was also inconclusive. The most significant differences were higher yields when UAN was surface applied. High yields when UAN was surface applied was attributed to the high amount of precipitation that occurred shortly after the midseason application