The comparative agronomic potential of Miscanthus x giganteus and Panicum virgatum as energy crops in Illinois

Bioenergy crops are rapidly gaining importance in the US and around the world. This dissertation describes 4 studies used to assess the comparative performance of Miscanthus x giganteus and Panicum virgatum as energy crops in Illinois. (1) A literature review of M. x giganteus experience in Europe and extrapolation to Illinois. Applying an agro-climatic model of M. x giganteus yields developed in Europe to Illinois suggested the crop yields of 27 and 43 t ha-1 . Assuming a farm gate value equivalent to that of fossil fuels suggested the crop would be very profitable compared to corn/soybean within Illinois, and could meet a significant portion of Illinois' energy demand. (2) A statistical analysis of peer-reviewed literature reports of M. x giganteus in Europe and P. virgatum in the US. Yields were extracted from all prior published trials of the two crops. Across the entire range of temperature, precipitation and nitrogen supply at which these crops have been tested M. x giganteus always outyielded P. virgatum. (3) The first US side-by-side trials of M. x giganteus and P. virgatum were established at three sites across Illinois in 2002. Peak biomass yields in 2004 and 2005 ranged from 26--61 t ha-1 for M. x giganteus , exceeding predictions and approximately four times the yields of the adjacent P. virgatum. (4) Both crops can recycle nitrogen so that fertilizer addition is minimized. Nitrogen dynamics were examined in the side-by-side trials. By late winter, the typical time of harvest, N content was just 0.14% in M. x giganteus and 0.35% in P. virgatum representing about 40 and 11 kg N ha-1 annual takeoff. The findings suggest that even at these very low N contents, nitrogen fertilization would be necessary in the long-term to maintain yields. (5) This study shows that M. x giganteus does have exceptional potential as a biomass crop in Illinois conditions. The annual yields of biomass achieved are among the highest known and yet the crop received no inputs after establishment. There are significant barriers to realizing this potential at a commercial scale: propagation, planting and lack of genetic diversity appearing particular barriers.