Biomass Yield and Nutrient Removal Rates of Perennial Grasses under Nitrogen Fertilization

Perennial grasses may provide a renewable source of biomass for energy production. Biomass yield, nutrient concentrations, and nutrient removal rates of switchgrass (Panicum virgatum L.), giant miscanthus (Miscanthus x giganteus), giant reed (Arundo donax L.), weeping lovegrass [Eragrostis curvula (Shrad.) Nees], kleingrass (Panicum coloratum L.), and Johnsongrass (Sorghum halepense (L.) Pers.) were evaluated at four N fertilizer rates (0, 56, 112, or 168 kg N ha(-1)) on a Minco fine sandy loam soil in southern Oklahoma. Species were established in 2008 and harvested for biomass in winter of 2009 and 2010. Biomass yield (dry matter basis) did not show a strong relationship with N fertilizer rate (p = 0.08), but was affected by year and species interactions (p < 0.01). Weeping lovegrass and kleingrass produced 29.0 and 16.0 Mg ha(-1) in 2009, but only 13.0 Mg ha(-1) and 9.8 Mg ha(-1) in 2010, respectively. Biomass yields of giant reed, switchgrass, and Johnsongrass averaged 23.3, 17.8, and 6.0 Mg ha(-1), respectively. Giant miscanthus established poorly, producing only 4.7 Mg ha(-1). Across years, giant reed had the highest biomass yield, 33.2 Mg ha(-1) at 168 kg N ha(-1), and the highest nutrient concentrations and removal rates (162 to 228 kg N ha(-1), 23 to 25 kg P ha(-1), and 121 to 149 kg K ha(-1)) among the grasses. Although giant reed demonstrated tremendous biomass production, its higher nutrient removal rates indicate a potential for increased fertilization requirements over time. Switchgrass had consistently high biomass yields and relatively low nutrient removal rates (40 to 75 kg N ha(-1), 5 to 12 kg P ha(-1), and 44 to 110 kg K ha(-1)) across years, demonstrating its merits as a low-input bioenergy crop.