Ecosystem Carbon Dioxide Flux in Perennial and Annual Crops used on Mixed Beef Farms.
Vern Baron1, David, G. Young1, and Claude Labine2. (1) Agriculture and Agri-Food Canada, Lacombe Research Center/ Plant & Soil Section, 6000 C & E Trail, Lacombe, AB T4L 1W1, CANADA, (2) Campbell Scientific (Canada) Corp., 11564 - 149 St. NW, Edmonton, AB T5M 1W7, Canada
Carbon sequestration on mixed farms requires an understanding of year round carbon dioxide flux dynamics in more than one crop species. This study compared daily, seasonal and annual carbon dioxide flux between barley and meadow bromegrass fields typical of those used for forage production on beef systems found in central and northern Alberta. Towers with Bowen ratio/energy balance (BREB) instrumentation were placed in two adjacent fields with north-west facing slopes at Lacombe, AB, Canada. The meadow bromegrass field was established in 2002 and the barley field, annually using zero-tillage techniques. Measurements were initiated on April 10, 2005. In 2005 the barley and meadow bromegrass provided 86 and 186 days of carbon dioxide sink, respectively. However, mid-season average daily BREB carbon dioxide uptake was 2.5 times greater for barley than meadow bromegrass. Night time average daily BREB carbon dioxide flux to the atmosphere was 45% greater for meadow bromegrass compared to barley during the sink period. The net carbon dioxide flux during the sink period was 2023 g m-2 for barley and 893 g m-2 for meadow bromegrass. The total carbon dioxide lost from the ecosystem during the respective dormant periods was 1955 g m-2 and 599 g m-2 for barley and meadow bromegrass, respectively resulting in a net sequestration of 68 g m-2 for barley and 294 g m-2 for meadow bromegrass during the 2005 – 2006. Estimates of carbon dioxide equivalent removal in harvested material was 2470 g m-2 for barley; 1420 g m-2 and 390 g m-2 of hay and grazed regrowth, respectively were removed for meadow bromegrass. Thus, while the perennial crop was the stronger ecosystem sink, the agricultural utilization of the crops, resulted in their being sources for carbon dioxide emission.