Onion (A. cepa) is an important horticulture crop which is sensitive to nutrient limitations worldwide. Urea hydrolysis to ammonia (NH3) and carbon dioxide (CO2), due to soil urease activity, causes urea-N loss. Comparative to several commercial products, the potential use of micronutrient coated urea to reduce urea hydrolysis based NH3-volatilization losses is novel to-date. In this study, boron (B), iron (Fe), zinc (Zn) and copper (Cu) were coated on urea at their full or half recommended rates as (B)-half, (Fe)-half, (Zn)-half, (Cu)-half, (B)-full, (Fe)-full, (Zn)-full, (Cu)-full, (B+Fe)-half, (B+Zn)-half, (B+Cu)-half, (Fe+Zn)-half, (Fe+Cu)-half, (Zn+Cu)-half, (B+Fe)-full, (B+Zn)-full, (B+Cu)-full, (Fe+Zn)-full, (Fe+Cu)-full and (Zn+Cu)-full having gum-only coated urea as an internal control. Parallel to these, p-Phenylenediamine (PPD-0.2 %, 0.4 %, 0.6 %, 0.8 % and 1.0 %) and hydroquinone (HQ-0.5 %, 1.0 % and 2 %) coated urea treatments were also used with acetone-only coated urea as an internal control. Whereas the uncoated urea treatment was taken as an overall control. In pot experiment, the soil residual urea concentrations were increased by 2, 0.5, 1.85, 2.69 and 3.15 folds at 8 days after incubation (DAI), by 5.6, 1.89, 5.97, 0.54 and 6.23 folds at 12 DAI and by 119, 123, 155, 84 and 87 folds at 16 DAI under (B)-full, (B+Zn)-full, (Fe+Zn)-full, PPD-0.8 % and PPD-1.0 % coated urea treatments, respectively, as compared to uncoated urea. Among these five coating combinations, 54.26 % and 44.82 % bulb yield increments were observed under (Fe+Zn)-full and PPD-1 % coated urea, respectively, in comparison to uncoated urea in field experiment. However, the 33.33 % increment in nitrogen agronomic efficiency (NAE) and subsequent economic gains proved (Fe+Zn)-full coated urea application as a solution to address N losses in alkaline calcareous soils.