Nitrous Oxide Emissions from a Fallow Field Fertilized with Anhydrous Ammonia

Nitrous oxide emission was measured from fallow Palouse silt loam (fine‐silty, mixed, mesic pachic Ultic Haploxerolls) fertilized with 0, 55, 110, and 220 kg of N ha −1 as anhydrous NH 3 . The objective was to quantify N 2 O losses during nitrification of banded anhydrous NH 3 under field conditions. Maximum N 2 O emission occurred shortly after initiation of rapid nitrification. Nitrites were present in the center of the NH 3 retention zone during N 2 O emission from the 110 and 220 kg N ha −1 treaments but not in the retention zone of the check or 55 kg N ha −1 treatments. Cumulative N 2 O emission increased as the NH 3 rate was increased, but was disproportionately large from the 220 kg N ha −1 treatments. However, even at the high N application rate, which was twice that recommended for the alternate winter wheat‐fallow area of the Pacific Northwest, less than 0.1% of the applied N was recovered as N 2 O. Recovery of applied NH 3 in the mineral form was approximately 100, 100, and 80%, respectively, for the 55, 110, and 220 kg N ha −1 treatments 5 weeks after application, suggesting that at the higher N rate N losses may have occurred via mechanisms other than N 2 O.