Ammonia volatilization from urea reduced N fertilizer efficiency of crops. Addition of acidic materials to urea may reduce NH3 volatilization and improve N use efficiency. The objectives of this study were to compare the effects of compacted or blended mixtures of urea and triple superphosphate (TSP), urea and KCl, or urea, TSP, and KCl on NH3 volatilization and N use efficiency by corn Zea mays L.) under a no-till system. A Ste. Rosalie clay (Typic Humaquept) and an Ormstown silty clay loam (Typic Humaquept) were used with three rates of TSP (0, 26, and 52 kgP ha-1) and two rates of KCl (0 and 100 kg K ha-1). Total NH3 volatilization for 9 d following fertilization ranged from 27 to 31 g kg-1 of added urea-N on the Ste. Rosalie soil and from 50 to 82 g kg-1 on the Ormstown soil with urea alone. Ammonia volatilization decreased when TSP, KCl, or both were applied with urea. Nitrogen recovery of added urea, N use efficiency, and corn yields increased with added TSP and KCl. Compacted mixtures of urea with TSP, KCL, or both had an advantage over blended fertilizers in reducing NH3 volatilization and improving N use efficiency and corn yields.