Yield of switchgrass as affected by seeding rates and dates

A bio-refinery to produce ethanol from switchgrass (Panicum virgatum L.) and corn cobs (Zea mays L.) opened in January 2009 in Monroe County Tennessee, USA, and contracts have been awarded to farmers within an 80 km area to produce switchgrass as a biofuel feedstock. This research was undertaken to provide information about seeding rates and dates for a projected 4000 ha of switchgrass production. The experimental treatments were seeding rates of 4.48, 6.72, 8.96, and 11.2 kg ha−1 of pure live seed (PLS) and seeding dates at two week intervals on April 23, May 7, May 21, and June 4, in 2007. The seeding rate of 4.48 kg ha−1 produced lower yields of dry matter than the other seeding rates during the establishment year (4.69 vs 6.42 Mg ha−1). There were no differences in yield among seeding rates in the second through the fourth year of production. The early seeding dates of April 23 and May 7 produced lower yields than the May 21 and June 4 seeding dates in each of the first three years of production. In the fourth year of production, yield from the first planting date was equal to the third and fourth planting dates.