ARS | Publication request: Potential Greenhouse Gas Emissions from Two Switchgrass Cultivars under Different N Fertilization Rates

Submitted to: Soil Science Society of America Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: November 1, 2010
Publication Date: November 1, 2010
Citation: Jin, V.L., Varvel, G.E., Wienhold, B.J., Mitchell, R., Vogel, K.P. 2010. Potential Greenhouse Gas Emissions from Two Switchgrass Cultivars under Different N Fertilization Rates. Abstract #338-2. ASA-CSSA-SSA Annual Meeting Abstracts (CDROM), 1-3 Nov., 2010, Long Beach, CA.

Technical Abstract: Increased production and use of biofuels derived from perennial feedstocks such as switchgrass is expected to reduce the emission of fossil-based carbon dioxide (CO2) into the atmosphere. Management choices (e.g. cultivar, fertilization), however, could affect the emission of other important temperature-forcing greenhouse gases (GHGs) such as methane (CH4) and nitrous oxide (N2O). Potential emissions of CO2, CH4, and N2O and net N mineralization were measured from incubations of surface soils (0-5 cm, 5-10 cm) collected at the end of the growing season from a field experiment using two different cultivars of switchgrass (Cave-in-Rock, Trailblazer) under three N fertilization rates (0, 60, 120 kg N ha-1). Triplicate soil samples (50 g) were incubated under controlled laboratory conditions in the dark (25°C, 55% water-filled pore space) over a 28-day incubation period, and headspace gas samples were collected weekly for GHG analysis. Potential N mineralization rates did not differ between switchgrass cultivars, but was significantly greater in soils fertilized at 120 kg N ha-1 compared to lower N rates (P < 0.0001). No treatment effects were significant for cumulative CH4 production. Cumulative CO2 and N2O production were greater in 0-5 cm soils compared to 5-10 cm (P < 0.0001). Cumulative CO2 production was highest in Cave-in-Rock soils fertilized at 120 kg N ha-1 compared to the lower N rates (P < 0.01), but no N rate effect on C mineralization was apparent for Trailblazer soils. Cumulative N2O production, however, was highest in soils from both cultivars treated at the highest N rate. Cumulative N2O production in Trailblazer soils tended to be higher than Cave-in-Rock soils (P = 0.0910), but appeared to be related to greater residual soil N associated with decreased growth and lower overall biomass production by the Trailblazer cultivar. Thus, optimizing N fertilization rate with the biomass production potential for individual switchgrass cultivars could minimize potential GHG emissions from these