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A recently developed slant-path flux gradient (FG) technique, combined with open-path Fourier transform infrared (OP-FTIR) spectroscopy, was deployed to concurrently measure gas emissions of ammonia (NH 3 ), nitrous oxide (N 2 O), carbon dioxide (CO 2 ), and methane (CH 4 ) from an intensive vegetable farm in Australia. Gas fluxes were continuously measured for three weeks following chicken manure application to a celery crop, followed by intermittent measurements for three days a week for another three weeks. The average flux measured over the 41 day measurement period for NH 3 and N 2 O, was 5.2 and 2.9 mg N m −2  h −1 , respectively, CH 4 was 1.1 mg C m −2  h −1 , and CO 2 was 0.7 C g m −2  h −1 . Manure and fertilizer application substantially increased the emissions of these gases, by providing carbon (C) and nitrogen (N) substrates to the soil. The cumulative N losses as NH 3 and N 2 O following fertilizer application were 6.7% and 3.7% of total N applied, respectively. Using this FG/OP-FTIR technique, we demonstrated that the N 2 O emission factor for this vegetable farm is much higher than the IPCC default emission factor for manure applied to managed lands. These results highlight the need for large-scale measurements to quantify multiple gas losses from intensive agricultural systems. [ABSTRACT FROM AUTHOR]