Switchgrass Biomass Yield Responses to Stand Density and Nitrogen Fertilization in Illinois.

Switchgrass potential as a feedstock for biomass production is being evaluated for the best management practices in central Illinois.  An established switchgrass plot planted in 2004 was fertilized with urea and ESN-urea at five nitrogen rates (0, 56, 112, 158, and 224 kg N ha^-1).  Plots were harvested during the peak summer maturity (7-15.5 Mg ha^-1), after killing frost (4.5-10.5 Mg ha^-1), and early spring (4.5-8.5 Mg ha^-1) in order to evaluate the potential for biomass yield.  Yields showed a positive response to increasing N rates and a negative response over time.  Response to applied nitrogen indicates optimal application rates between 112 and 224 kg N ha^-1 of urea. Harvest during the summer achieved maximum harvestable dry biomass.