Comparing CO2 Flux Data from Eddy Covariance Methods with Bowen Ratio Energy Balance Methods from Contrasting Soil Management.

Measuring CO₂ fluxes from contrasting soil management practices is important for understanding the role of agriculture in CO₂ flux source-sink relationships.  There are several micrometeorological methods for measuring CO₂ emissions, however all are expensive and thus do not easily lend themselves to spatial replication and frequentist statistical models.  The present study was conducted to measure CO₂ fluxes over four contrasting agricultural management treatments on a Rhodustalf soil using the Bowen ratio energy balance (BREB) and eddy covariance (EC) systems.  Meteorological data and CO₂ fluxes were measured with BREB instruments over four plots with three plots of corn (Zea mays L.) and a fourth tilled and fallow plot during and after the growing season in Harare, Zimbabwe.  Contrasting tillage and irrigation treatments were applied to the three corn plots.  The four BREB instruments were placed near the center of each plot and a separate EC instrument was centrally located between the four plots.  Fluxes of CO₂ were derived every 30 minutes for all five instruments.  The EC data downwind of a particular BREB instrument was compared with the BREB data.  Initial data analyses indicate that measurements of sensible heat fluxes compare well among the various systems, but that there is considerable scatter among the CO₂ fluxes, with experimental challenges arising from the need to ensure that the EC system is correctly reporting results associated with a specific upwind plot.