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Growing season greenhouse gas flux from switchgrass in the northern great plains

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Switchgrass (Panicum virgatum L.) is being evaluated as a bioenergy crop for the northern Great Plains. Field measurements of CO₂, CH₄, and N₂O flux are needed to estimate the net greenhouse gas (GHG) balance of this biofeedstock. The study objective was to determine effects of recommended Nitrogen (N) fertilization (67 kg ha⁻¹ of N applied) and unfertilized switchgrass on growing season soil-atmosphere CO₂, CH₄, and N₂O flux using static chamber methodology. 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 (27.6 kg ha⁻¹ ± 4.0 kg ha⁻¹ vs. 86.3 kg ha⁻¹ ± 14.3 kg ha⁻¹ as CO₂ equivalents (CO₂eq) for 0 kg ha⁻¹ and 67 kg ha⁻¹ of N applied, 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 Mg ha⁻¹ ± 0.5 Mg ha⁻¹ dry matter) than without N (3.2 Mg ha⁻¹ ± 0.5 Mg ha⁻¹) (P < 0.05). Net greenhouse gas intensity (GHGI; kg GHG flux kg⁻ ¹ harvest yield as CO₂eq) for switchgrass production was similar between N treatments (0.71 vs. 0.44 for 0 kg ha⁻¹ and 67 kg ha⁻¹ of N applied, respectively; P = 0.18).
M.R. Schmer , M.A. Liebig , J.R. Hendrickson , D.L. Tanaka , R.L. Phillips
USDA Scientist Submission
Biomass and bioenergy 2012 October v.45
Elsevier Ltd
Journal Articles, USDA Authors, Peer-Reviewed