Switchgrass Management as a Biomass and Biofuels Crop.

Switchgrass is a high biomass producing perennial that offers great potential to be effectively used as a bioenergy crop for cellulosic ethanol production. Switchgrass management variables including seeding rate, nitrogen rate, variety selection, weed control, and storage and harvest strategies have been investigated for 5 years. A seeding rate-nitrogen rate interaction study with 5 seeding rates, 2.8 to 14 kg/ha, and 4 nitrogen rates, 0 to 202 kg N/ha, on four distinct soil-landscape situations has been conducted for the last 5 years. These situations include a moderately well-drained upland, severely eroded sloping upland, well drained level floodplain, and poorly drained floodplain. Data generally indicate no interactions between seeding and nitrogen rate and no dry matter biomass yield increase above 67 kg N/ha. Under good management, seeding rates, as low as 2.8 kg pure live seed/ha have been sufficient for maximum biomass yield. A variety evaluation has also been conducted on the same four soil-landscape positions for 5 years. The common Alamo, lowland variety, was compared to three synthetic lowland ecotypes. Generally yields between the cultivars have not been significantly different. Weed control studies are also underway. Data indicate weed control is probably not necessary except in year 1 and sometimes year 2 when very severe weed competition was present, especially from annual grasses. Disease incidence for the cultivars evaluated has been low and considered not yield limiting. Large round and square bales are also being compared under different storage scenarios to evaluate dry matter losses. These data are being used to develop specific production management strategies for most profitable switchgrass biomass production for conversion to bioenergy products such as ethanol. Switchgrass production is expanding in TN, with about 2500 ha being contracted for use by a pilot biorefinery planted or to be planted next year.