Nitrogen fertilization of Miscanthus x giganteus: effects on nitrogen uptake, growth, yield and emissions from biomass combustion

A field experiment was carried out to study the effect of N fertilization on a recently established crop of Miscanthus x giganteus. Five N rates (0, 40, 80, 120 and 160 kg/ha/year) were applied during the second, third and fourth growing seasons. Spring harvested biomass yields were increased by N fertilization in all growing seasons. Increases in biomass yield were attributable to positive effects of N fertilization on the number of shoots per plant and on plant height. During the third and fourth growing seasons, the biomass yields from the 120 and 160 kg/ha treatments were 35 and 43 %, respectively, higher than that of the control but estimated combustion emissions of NOx and N20 from these treatments were significantly greater than all other treatments. The environmental benefits of using N fertilization to enhance biomass production will be mitigated by higher emissions of environmentally harmful nitrogenous species from biomass combustion if N fertilization leads to significant increases in biomass N concentration.