Fluxes of Nitrous Oxide and Molecular Nitrogen from Irrigated Soils of Catalonia (Spain)

Abstract

AbstractNitrous oxide (N2O) is a gas of environmental concern that can be emitted during nitrification and denitrification. Molecular nitrogen (N2) is the ultimate product of denitrification. The emission of both gases represents an economic loss. This study quantified daily and seasonal N2O and N2 emissions from three benchmark arable soils sown with maize (Zea mays L.) in Catalonia (northeast Spain) during the irrigation season, and identified the major factors and processes determining these emissions. The N2O was sampled using the closed chamber method, and N2 from N2O that accumulated with the acetylene inhibition method, simultaneously in the field. At water‐filled pore space (WFPS) >70%, losses 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 complete denitrification. Up to 640 g of N2‐N ha−1 d−1 were lost from the El Pinell site, 1438 g of N2‐N ha−1 d−1 from the Barbens site, and 233 g of N2‐N ha−1 d−1 from the Bellpuig site. Negative N2O and N2 fluxes were found. Total (N2O + N2)‐N losses represent 13.6% 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 measured. The potential for gaseous N losses from these soils at <40% WFPS is low (it averaged 0.01 g of N ha−1 d−1 from the three sites).