Nitrous Oxide Emissions from Annual and Perennial Biofuel Cropping Systems

Burning of fossil fuels in the transportation sector accounts for 28% of US greenhouse gas (GHG) emissions. Substitution of cellulosic biofuel in place of conventional gasoline or diesel could reduce GHG emissions from transportation; however, the effectiveness of cellulosic biofuel in reducing emissions depends on emissions during the growth of biofuel crops. The objectives of this study were (i) to measure N2O emissions of potential cellulosic biofuel cropping systems, and (ii) to characterize the temporal variations in N2O emissions in these cropping systems. Annual N2O emissions were measured in corn (Zea mays L.)-soybean [Glycine max (L.) Merr.] and photoperiod-sensitive sorghum [Sorghum bicolor (L.) Moench]-soybean rotations as well as in switchgrass (Panicum virgatum L.) and miscanthus (Miscanthus sacchariflorus) from 2011-2013 in Manhattan, KS, using static chambers. No consistent significant differences were found in N2O emissions among crop species, though miscanthus tended to have the least emissions. Most N2O was emitted during large events of short duration (1-3 d) that occurred after substantial rainfall events with high soil NO3-. In 2011 and 2012, most N2O was emitted during the growing season. In 2013, 30-50% of the N2O emissions were emitted after September which was attributed to freeze-thaw cycles.