OBTAINING NET GHG FLUX MEASUREMENTS AS PART OF NACP

R Desjardins Agriculture and Agri-Food Canada, 960 carling Ave, K.W. Neatby Building, Ottawa, K1A0C6, Canada

Desjardins@agr.gc.ca

It is generally well accepted that agricultural soils have the potential to sequester C. The actual C sequestration depends on the agricultural practice, the environmental and soil conditions. To quantify the impact is a challenge that can be tackled using flux measurements. The combination of tower and aircraft-based flux measurements collected in Iowa, during 2003, over an agricultural region consisting primarily of soybean and corn crops is an example of a data set that could be used to develop and verify how one can scale up tower-based flux measurements of CO2 to obtain regional CO2 flux estimates. However, increasing soil C sequestration may not always contribute to a net GHG reduction because a practice that increases soil C sequestration can either have a positive or negative effect on the net GHG budget because of the trade-off between C sequestration and N2O emissions. Two case studies will be presented where local N2O emissions were scaled up to a region: 1) A series of chamber measurements over a 10 by 10 km2 area will be compared to N2O flux measurements using aircraft–based sensors. 2) A combination of tower and aircraft-based N2O flux measurements will be shown to provide daily N2O flux emissions at a regional scale. More data sets of this type are required for improving and testing process-based models of CO2 and N2O.