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

Abstract

Abstract Switchgrass ( Panicum virgatum L.) is being evaluated as a bioenergy crop for the northern Great Plains. Field measurements of CO 2 , CH 4 , and N 2 O 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 CO 2 , CH 4 , and N 2 O flux using static chamber methodology. Mean hourly CO 2 flux was greatest during periods of active switchgrass growth and was similar between N fertilizer treatments ( P = 0.09). Mean hourly N 2 O flux was consistently greater under N fertilization than without N throughout the growing season. Overall, N fertilization of switchgrass affected cumulative growing-season N 2 O flux (27.6 kg ha −1 ± 4.0 kg ha −1 vs. 86.3 kg ha −1 ± 14.3 kg ha −1 as CO 2 equivalents (CO 2 eq) for 0 kg ha −1 and 67 kg ha −1 of N applied, respectively; P 2 or CH 4 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 − 1 harvest yield as CO 2 eq) 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).