Ammonia loss from commercial fertilizers can impact the formation of atmospheric aerosols, as well as contribute to nitrogen (N) deposition in terrestrial and aquatic ecosystems. Urea is the predominant form of N fertilizer used worldwide due to its high N content (46.6% N) and low cost.  Once in contact with soil or vegetation, urea is hydrolyzed to ammonium via the activity of naturally occurring urease enzymes. Losses of N from surface applied urea as ammonia can exceed 30%. To address this issue, various physical and chemical mechanisms have been incorporated into granular urea. The most common chemical mechanism is incorporation of an urease inhibitor such as N-(n-butyl) thiophosphoric triamide (NBPT). In this study, we investigated ammonia volatilization from surface applied urea using a new urease inhibitor formulation (LIMUS^® from BASF, The Chemical Company) as compared to commercially available granular urea. Laboratory experiments were conducted with a customized growth chamber system designed to continuously measure ammonia volatilization. With day/night soil surface temperatures of 10/21⁰C, urea or LIMUS^®-treated granules were surface applied (+/- crop residues) to columns filled with a Midwestern US soil (Drummer silty clay loam). Temporal patterns in ammonia volatilization were followed for at least 10d. Field experiments were conducted on a plot of translocated Drummer silty clay loam to a research site just south of Raleigh, NC. Ammonia volatilization of applied urea granules was monitored using acid-coated foam in covered-PVC cylinders, or annular denuder technology using flow-through PVC chambers. Daily exchanges of acid-coated denuder tubes enhanced the sensitivity of ammonia volatilization measurements for the treated-urea granules. Ammonia-loss from commercial urea granules ranged from 6 - ~ 35%, depending on ambient temperature. This loss typically occurred within the first 5-10 days under field conditions. Incorporation of the urease-inhibitor product minimized the loss of N via volatilization (< 5%) for up to 20+ days in the absence of a rainfall event. Visual observations confirmed that on bare soil, treated or untreated urea granules quickly “dissolve” and move into the soil. The accompanying urease-inhibitor formulation moves with the urea continuing to provide protection against reaction with naturally occurring urease enzymes. In the presence of crop residues, the urease inhibitor was also very efficient. Use of the new urease inhibitor formulation is an effective way to reduce N losses as ammonia when urea-containing fertilizers are surface applied to agricultural crops.