Bovine urine spots on grassland can produce considerable amounts of N₂O.  The primary source of N in cattle urine is urea, and ingestion of small amounts of condensed tannin from some plants can reduce urine urea levels.  This trial compared greenhouse gas flux from a mixed-grass prairie exclosure after application of water, normal and tannin-altered urine, and NH₄NO₃ fertilizer.  Nitrous oxide emission was quantified by gas chromatography using static chamber methodology over 75 days.  Total applied N concentration for each treatment was 0, 12.7, 8.4, and 12.7 g N L^-1 for water, normal urine, tannin-altered urine, and NH₄NO₃ fertilizer, respectively.  The amount of liquid applied to each chamber was equalized at 384 mL using a single application prior to gas sampling.  Average N₂O emission during the measurement period was 13.4, 18.6, 17.8, and 39.2 µg N m^-2 h^-1 for water, normal urine, tannin-altered urine, and NH₄NO₃ fertilizer, respectively, but these values were not different (P = 0.12).  Lack of difference in average N₂O emission between normal and tannin-altered urine spots may be a result of most N being emitted as NH_3, and/or the tannin-altered urine still having such a high amount of N that N₂O emission was maximized for this urine too.