Nitrous Oxide Emissions From Irrigated Cotton In Texas and Arizona.

Emissions of nitrous oxide (N₂O), a potent greenhouse gas. are known to multiply serveral several fold with N fertilizer additions to cropland.  Rarely do N₂O losses represent an agronomic or economic loss to a farmer.  Most N₂O emission data in the US is or corn or wheat.  Little data is available for cotton.  We conducted N rate cotton studies under a center pivot in Floydada, TX and with level basin irrigation in Maricopa, AZ.  Nitrous oxide emissions were measured weekly between first square and peak bloom.  Twenty-four-minute incubation periods with vented chambers were employed, followed by N₂O analysis on a ECD-GC.  .  At both sites, N₂O emissions declined as the season progressed, presumably as plant depleted available soil and fertilizer NO₃-N.  Fluxes were not detectable more than 4 days after irrigation events.  Nitrous oxide emissions were low, with a maximum seasonal flux of 367 g N₂O-N/ac lost for the 120 lb N/ac fertilizer rate in TX.  This is only 0.5% of applied N, and is well below the IPCC default N₂O emission factor of 1 %.