Comparison of Flux Gradient and Chamber Techniques to Measure Soil N2O Emissions.

We compared nitrous oxide (N₂O) emissions measured with static chambers to those from a newly developed micrometeorological flux gradient (FG) approach. Measurements were made at a vegetable farm following chicken manure application. The FG calculations were made with a single open-path Fourier transform infrared (OP-FTIR) spectrometer (height of 1.45 m) deployed in a slant-path configuration: sequentially aimed at retro reflectors at heights of 0.8 and 1.8 m above ground. Emissions were measured continuously with the FG technique, but once a day with chambers. The N₂O emission rates measured by FG were statistically higher (by 40%) than those from the chambers. Our results suggest the OP-FTIR slant-path FG configuration worked well in this study: it was sufficiently sensitive to detect the N₂O gradients over our site, giving high temporal resolution N₂O emissions corresponding to a large measurement footprint.