ARS | Publication request: Global Warming Potential of Organic and Conventional Grain Cropping Systems in the mid-Atlantic Region of the U.S.

Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: July 27, 2009
Publication Date: August 24, 2009
Citation: Cavigelli, M.A., Djurickovic, M., Rasmann, C., Spargo, J.T., Mirsky, S.B., Maul, J.E. 2009. Global Warming Potential of Organic and Conventional Grain Cropping Systems in the mid-Atlantic Region of the U.S. In: Proceedings of the Farming Systems Design Conference, August 25, 2009, Monterey, California, p.51-52.

Interpretive Summary: Agriculture impacts global climate change. The impact of agriculture on global climate change can be evaluated by estimating the net exchange of the greenhouse gases carbon dioxide, nitrous oxide and methane that result from on-farm practices and the production and transport of inputs. The sum of these effects for a particular agricultural system is called its global warming potential. We report here on global warming potential calculations for no-till (NT), chisel till (CT) and organic (Org3) cropping systems at the long-term USDA-ARS Beltsville Farming Systems Project in Maryland, USA. Global warming potential was positive in NT and CT and negative in Org3, primarily due to differences in soil carbon and secondarily to differences in energy use among systems. Despite relatively low crop yields in Org3, greenhouse gas intensity, which is the global warming potential per unit of crop yield, for Org3 was also negative and significantly lower than for NT and CT. Results indicate that Org3 helped reduce global climate change, while NT and CT contributed to global climate change. Practices common in organic systems—including incorporating legume cover crops and animal manures into soil—can help reduce global climate change compared to conventional systems, primarily by increasing the amount of carbon in the soil. These results will benefit policy makers, farmers, and others interested in reducing the impact of agriculture on global climate change.

Technical Abstract: The global warming potential (GWP) of a cropping system is the balance between the net exchange of the greenhouse gases CO2, N2O and CH4 that result from on-farm practices and the production and transport of inputs. We report here on GWP calculations for no-till (NT), chisel till (CT) and organic (Org3) cropping systems at the long-term USDA-ARS Beltsville Farming Systems Project in Maryland, USA. We estimated annual GWP by summing the net exchange of CO2 equivalents (CO2eqvt) from 1) changes in soil C, 2) N2O fluxes, and 3) energy used on farm and in the production and transport of material inputs. We also calculated greenhouse gas intensity (GHGI=GWP per unit of grain yield) using crop yield data from the site. The contribution of change in soil C to GWP was 0, 1080, and -1953 kg CO2eqvt ha-1 y-1 in NT, CT and Org3, respectively. The contribution of N2O flux to GWP was 303, 406, and 540 kg CO2eqvt ha-1 y-1 in NT, CT and Org3, respectively. The contribution of energy use to GWP was 807, 862, and 344 in NT, CT, and Org3, respectively. GWP (kg CO2eqvt ha-1 y-1) was positive in NT (1110) and CT (2348) and negative in Org3 (-1069), primarily due to differences in soil C and secondarily to differences in energy use among systems. Despite relatively low crop yields in Org3, GHGI (kg CO2eqvt Mg grain-1) for Org3 was also negative (-207) and significantly lower than for NT (330) and CT (153). Results indicate that Org3 was a net sink, while NT and CT were net sources, of CO2eqvt. Practices common in organic systems—including soil incorporation of legume cover crops and animal manures—can result in mitigation of GWP and GHGI relative to NT and CT systems, primarily by increasing soil C. [GRACEnet Publication]