Location: Agroecosystem Management Research
Title: Growing season greenhouse gas flux from switchgrass in the northern Great Plains Authors
Submitted to: Biomass and Bioenergy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 14, 2012
Publication Date: July 24, 2012
Repository URL: http://handle.nal.usda.gov/10113/54537
Citation: Schmer, M.R., Liebig, M.A., Hendrickson, J.R., Tanaka, D.L., Phillips, B.L. 2012. Growing season greenhouse gas flux from switchgrass in the northern Great Plains. Biomass and Bioenergy. 45:315-319. Interpretive Summary: Switchgrass (Panicum virgatum L.) is being evaluated as a bioenergy crop for the United States. Biofuels are expected to provide transportation energy needs in an environmentally sustainable manner. A research need regarding switchgrass for bioenergy is estimating soil greenhouse gas fluxes and how this is influenced by fertilizer management practices. A study was conducted in south, central North Dakota to measure CO2, CH4, and N2O flux in unfertilized switchgrass plots and fertilized (60 lbs N acre-1) switchgrass plots. Static chamber methodology and gas chromatography were used to measure CO2, CH4, and N2O flux between 24 May and 14 September, 2010 on a Parshall fine, sandy loam. Our experiment indicated that cumulative CO2 and CH4 fluxes were similar by N treatment. Results showed that N2O flux was higher under the fertilized than the unfertilized switchgrass plots. Soil CO2 flux accounted for >99% of total global warming potential for fertilized or unfertilized switchgrass. Harvested biomass yields from fertilized switchgrass plots were 113% higher than unfertilized switchgrass plots resulting in similar cumulative global warming potential values between N fertilizer treatments. Results from this study indicate greater N2O emissions will occur when switchgrass is fertilized which may impact regional N2O emissions but increased biomass production from N fertilizer results in similar global warming potential and greenhouse gas intensity values.
Technical Abstract: Switchgrass (Panicum virgatum L.) is being evaluated as a bioenergy crop for the United States. Field measurements of CO2, CH4, and N2O flux from switchgrass are needed to estimate the net greenhouse gas (GHG) balance of this biofeedstock. The study objective was to determine effects of N fertilization on growing-season soil-atmosphere CO2, CH4, and N2O flux from established switchgrass stands. The study was conducted in 2010 near Mandan, ND on a Parshall fine sandy loam. Static chamber methodology and gas chromatography were used to measure CO2, CH4, and N2O flux between 24 May and 14 September from unfertilized switchgrass and switchgrass fertilized with 67 kg N ha-1. Soil temperature affected growing season CO2 and N2O flux (P<0.01) while water-filled pore space (WFPS) affected CO2, CH4, and N2O (P<0.01). Mean hourly CO2 flux was greatest during periods of active switchgrass growth and was similar between N fertilizer treatments (P=0.09). Mean hourly N2O flux was consistently greater under N fertilization than without N throughout the growing season. Overall, N fertilization of switchgrass affected cumulative growing-season N2O flux (9.2±1.3 vs. 29.0±4.8 mg N2O m-1 for 0 and 67 kg N ha-1, respectively; P<0.01), but not cumulative CO2 or CH4 flux (P=0.08 and 0.51, respectively). Aboveground biomass production was greater with N application (6.8±0.5 Mg ha-1) than without N (3.2±0.5 Mg ha-1) (P<0.05). Net greenhouse gas intensity (GHGI) for switchgrass production was similar between N treatments (0.71 Mg CO2e GHG flux Mg-1 CO2e aboveground yield and 0.41 Mg CO2e GHG flux Mg-1 CO2e aboveground yield for 0 and 67 kg N ha-1, respectively; P=0.18). Results from this study indicate greater N2O emissions will occur when switchgrass is fertilized which may impact regional N2O emissions but increased biomass production from N fertilizer results in similar GHGI.