Volatilization losses reduce the efficiency of surface-applied urea for crop N uptake, and can be controlled using urease inhibitors to retard hydrolysis or by the presence of other amendments that enhance retention of NH4+ formed by urea hydrolysis. A greenhouse study was conducted to evaluate the effectiveness of oxidized charcoal (OCh; 150 g kg−1 fertilizer) applied with or without Cu and/or Zn (∼0.5–2 g kg−...