Effect of nitrogen fertilizer application rate on yield, methane and nitrous oxide emissions from switchgrass (Panicum virgatum L.) and reed canarygrass (Phalaris arundinacea L.)

This 2-yr (2008 - 2009) study conducted in Truro, Nova Scotia, measured plant biomass production (yield and ash content) and greenhouse gas emissions (methane and nitrous oxide), from the bioenergy crops switchgrass (SG; Panicum virgatum L.) and reed canarygrass (RCG; Phalaris arundinacea L.) receiving spring application of nitrogen fertilizer at 0, 40 and 120 kg N ha(-1). In both years, crop yields were unresponsive to N fertilizer. In 2008, SG average yields were greater than RCG producing 7.0 vs. 4.6 Mg ha(-1), respectively, while ash content was significantly greater for RCG in both years. Cumulative seasonal (May - November) N2O emissions were < 1 kg N2O-N ha(-1) in 2008 and <0.2 kg N2O-N ha(-1) in 2009 with crop (SG > RCG) and N fertilizer (N-120 > N-40 = N-0) effects found in 2008 only. Nitrate exposure was greater for SG in 2008 only, but responded to N fertilization in both years (N-120 > N-0). These crops were net sinks for methane and the magnitude of the sink was not influenced by crop type, N fertilization or year. Despite lower yields, the greenhouse gas intensity calculated for RCG (- 2 to 20 kg CO(2)e t(-1) biomass) was lower than for SG (8-60 kg CO(2)e t(-1) biomass) as a result of lower N-2 O emissions.