Use of the nocturnal boundary layer budget method in estimating farm-scale greenhouse gas emissions

Quantification and control of greenhouse gas emissions in agriculture is an area of special focus due to the relative ease in adjusting agricultural practices in response to scientific findings, making it possible to have a concrete reduction in emissions from this sector. Two of the challenges in obtaining precise estimates of emissions from the typical agricultural farm are the issues of scale and surface heterogeneity. Most commonly, measurements are made at various small scales, from relatively homogeneous surfaces, such as plots or fields, and these are scaled up to represent emissions from the farm as a whole. However, a typical farm and the GHG sources therein are not homogeneous in nature. Moreover, even within a so-called homogeneous surface (plot or field) there can be high spatial variability in emissions. For these reasons a farm-scale emission value can hold a high amount of error. In response to this problem, a study was conducted to explore the use of a micrometeorological method that measures GHG emissions directly at the farm scale.

This poster will present details on the use of the nocturnal boundary layer budget method in estimating farm-scale fluxes of CO2, CH4, and N2O from two eastern Canadian agricultural farms in 2002 and 2003. Special focus will be placed on methods of calculation and uncertainties inherent in the technique, with reference to spatial variability in gas concentrations near the surface and the problem of choosing an appropriate NBL height with which to calculate the GHG flux.