Nitrogen is an essential nutrient required for sustaining life and high-output cropping systems. However, it has been estimated that only 40-60% of applied fertilizer N is utilized by plant-uptake. Inherent inefficiencies in plant-soil systems can lead to excess N in the environment. One such inefficiency, NH₃ volatilization, can account for huge losses of applied N. Increased atmospheric NH3 concentrations have been linked with haze, eutrophication, and forest decline. Polymer-coated urea (PCU) is one type of nitrogen fertilizer that uses temperature controlled diffusion to better match N release to plant need and thusreduce N lossesGlasshouse and field studies were conducted with maize (Zea mays L.) and a mixture of Kentucky bluegrass (KBG; Poa pratensis L.) and perennial ryegrass (PRG; Lolium perenne L.) to compare an untreated control to 200 and 300 kg N ha^-1 applied as either uncoated urea or PCU (ESN^® or Duration CR45^®). Glasshouse studies were conducted in sand, sandy loam, and loam soils. Field studies were conducted in sand and clay loam soils.  Sample collection and analysis  for the  glasshouse studies were conducted using non-static, non-flow-through chambers and photoacoustic infrared spectroscopy. Sample collection for the field trials was conducted by a modified passive flux method. Three short-term (17-21 day) trials were conducted with sand, sandy loam, and loam soils and a full term (45 day) trial with the loam soil. In all cases, use of PCU substantially reduced ammonia volatilization compared to untreated urea, by 40-51% in field trials and 14-72% glasshouse studies. These significant reductions in NH₃ volatilization represent progress in reducing loss of N to the environment following fertilization.