FLUXES OF NITROUS-OXIDE AND MOLECULAR NITROGEN FROM IRRIGATED SOILS OF CATALONIA (SPAIN)

Nitrous oxide (N2O) is a gas of environmental concern that can be emit ted during nitrification and denitrification. Molecular nitrogen (N-2) is the ultimate product of denitrification. The emission of both gase s represents an economic loss. This study quantified daily and seasona l N2O and N-2 emissions from three benchmark arable soils sown with ma ize (Zea mays L.) in Catalonia (northeast Spain) during the irrigation season, and identified the major factors and processes determining th ese emissions. The N2O was sampled using the closed chamber method, an d N-2 from N2O that accumulated with the acetylene inhibition method, simultaneously in the field. At mater-filled pore space (WFPS) >70%, l osses amounted to 389 g of N2O-N ha(-1) d(-1) from the El Pinell site, 144 g of N2O-N ha(-1) d(-1) from the Barbens site, and 125 g of N2O-N ha(-1) d(-1) from the Bellpuig site. Most of the N was lost through c omplete denitrification. Up to 640 g of N-2-N ha(-1) d(-1) were lost f rom the El Pinell site, 1438 g of N-2-N ha(-1) d(-1) from the Barbens site, and 233 g of N-2-N ha(-1) d(-1) from the Bellpuig site. Negative N2O and N-2 fluxes were found. Total (N2O + N-2)-N losses represent 1 3.6% of the N applied at the El Pinell site, 8.6% at the Barbens site, and 1.7% at the Bellpuig site. Denitrification was the main source of emission. Significant N2O-N losses due to nitrification were also mea sured. The potential for gaseous N losses from these soils at <40% WFP S is low (it averaged 0.01 g of N ha(-1) d(-1) from the three sites).