Grass seed growers in the dryland areas of eastern Washington and northern Idaho were recently forced to begin using urea-based nitrogen (N) sources alternatives to ammonium nitrate. The purpose of this study was to evaluate the influence of dryland grass seed production conditions on ammonia (NH3) volatilization from urea-based N sources in the laboratory and field, and Kentucky bluegrass seed yields and N recovery in the field. In laboratory simulations of field systems, surface pH averaged 8.5 in unburned and 9.5 in burned systems, while the burned system had net urease enzyme activity of <1% of the unburned systems. Laboratory incubations suggest the potential for NH3 volatilization from urea is greater from stands in which post-harvest residue is baled and removed than from stands in which residue is burned. In the field, surface pH was >8.0 in both burned and unburned stands. Burning also resulted in high surface temperatures and, similar to lab measurements, low urease enzyme activity.  Results from the field were similar to those in the lab, indicating higher rates of NH3 volatilization from a bluegrass stand that was not burned. Rates of NH3 volatilization were also higher with urea-based N sources applied in mid-November compared to early October, presumably due to a higher soil moisture content in November.