Effect of nitrogen addition on Miscanthus ×giganteus yield, nitrogen losses, and soil organic matter across five sites

The US Department of Energy has mandated the production of 16 billion gallons (60.6 billion liters) of renewable biofuel from cellulosic feedstocks by 2022. The perennial grass, Miscanthus×giganteus, is a potential candidate for cellulosic biofuel production because of high productivity with minimal inputs. This study determined the effect of three different spring fertilizer treatments (0, 60, and 120kg Nha^-1yr^-1 as urea) on biomass production, soil organic matter (SOM), and inorganic N leaching in Illinois, Kentucky, Nebraska, New Jersey, and Virginia, along with N₂O and CO₂ emissions at the IL site. There were no significant yield responses to fertilizer treatments, except at the IL site in 2012 (yields in 2012, year 4, varied from 10 to 23.7 Mgha^-1 across all sites). Potentially mineralizable N increased across all fertilizer treatments and sites in the 0-10cm soil depth. An increase in permanganate oxidizable carbon (POX-C, labile C) in surface soils occurred at the IL and NJ sites, which were regularly tilled before planting. Decreases in POX-C were observed in the 0 - 10cm soil depth at the KY and NE sites where highly managed turfgrass was grown prior to planting. Growing M.×giganteus altered SOM composition in only 4years of production by increasing the amount of potentially mineralizable N at every site, regardless of fertilization amount. Nitrogen applications increased N leaching and N₂O emission without increasing biomass production. This suggests that for the initial period (4years) of M.×giganteus production, N application has a detrimental environmental impact without any yield benefits and thus should not be recommended. Further research is needed to define a time when N application to M.×giganteus results in increased biomass production.