Effect of Irrigation Management On Nitrous Oxide Emissions From Winter Wheat.

Land-use and agricultural practices affect the soil microbial carbon (C) and nitrogen (N) turnover and the biosphere-atmosphere exchange of greenhouse gasses (GHG), namely N₂O, CH₄ and CO₂. In view of the global importance of irrigated agriculture, it is critical to understand how and to which extent this land-use system interacts with the terrestrial N and C cycles and contributes to atmospheric GHGs.

There is limited data on the influence of irrigation management on trace gas exchanges. We present a study on the effect of different irrigation intensities on the emissions of nitrous oxide from irrigated winter wheat on black vertisols in South-Eastern Queensland, Australia.

Soil N₂O fluxes from winter wheat were monitored over one season with an automated measuring and analysis system allowing for a high temporal resolution. N₂O emissions were highly variable both temporarily and spatially with highest fluxes occurring after rainfall or irrigation. The magnitude of these “emission pulses” was found to be largely controlled by the amount of irrigation water applied with total N₂O emissions corresponding to 0.2- 0.4% of total N applied. Highest seasonal N₂O emissions were observed in the treatment with the highest irrigation intensity; however N₂O emissions in relation to yield were highest in the treatment with the lowest irrigation intensity. Our data suggests that timing and amount of irrigation can effectively be used to reduce N₂O losses from irrigated agricultural systems; however for best management practices the ratio of N₂O emissions to crop yield has to be taken into account.