Multi-Plot Micrometeorological Measurements of Nitrous Oxide Flux from Agro-Ecosystems.

Nitrous oxide fluxes are highly variable in time with management practices (e.g. manure or inorganic nitrogen addition) and weather (e.g. severity of winter freezing) interacting to drive the variability in emission.  Micrometeorological methods do not interfere with source conditions and hence, can be used quasi-continuously (at hourly to half-hourly intervals) to capture the highly intermittent nature of N₂O emission episodes.  Simultaneous flux measurements on multiple plots in-situ are desirable so that the effect of management practices on emissions can be characterized. We have conducted several studies deploying the flux-gradient technique to measure surface N₂O fluxes at a long-term site in Elora, ON, Canada, established in 2000 with the objective of improving our understanding of how management affects N₂O emissions.  The flux measurement methodology used will be described and operational details (e.g. air sampling system, site requirements) will be presented within the context of other micrometeorological techniques such as eddy covariance.  Results of past and recent experiments will be used to illustrate the long-term dataset and what has been learned through quasi-continuous measurements.  Integration of research results with other techniques such as chamber methods will be discussed.