Crop, Amendment, and System Effects On Greenhouse Gas Emission in a Cool Climate.

Estimating greenhouse gas (GHG) emissions from agricultural systems are affected by many production practices.  A long-term potato cropping system experiment established in 2004 in Presque Isle, ME, on a sandy loam soil addresses three scenarios [ 1) Business as Usual, 2) Maximizing Soil C Sequestration, and 3) Minimizing Greenhouse Gas (GHG) Emission] that are relevant to a USDA-ARS Cross-Location Research Project involving 30 locations. Our objective was to compare GHG emissions from these three systems during the growing season.  The Business as Usual system consists of a barley-potato rotation with fall tillage for both crops.  The Soil C Sequestration scenario employs no-till planting barley plus interseeded timothy in Year 1, followed by timothy sod in Year 2, and spring tillage with potato in Year 3.  This system is present with and without annual compost application.  Emissions of carbon dioxide (CO₂) and nitrous oxide (N₂O) were monitored in both the barley and potato phases of each system during the growing season in 2006 (barley only), 2007, and 2008.  Samples were collected from vented chambers (0.4 by 0.8 m) at 7-14 d intervals.  Cumulative CO₂ flux was consistently greater in potato than in barley, due to frequent disturbance events.  Annual application of compost increased C and N emission slightly from each crop, although not the same extent that this practice increased soil C concentration or storage.  Emission of N₂O from potato under saturated conditions was 5 to 10-fold higher than from barley, due to both placement and amount of N fertilizer input.  This research contributes to regional and national estimates of GHG emissions from agriculture.