Low-Input Production of Biomass from Perennial Grasses in the Coastal Plain of Georgia, USA

Warm-season perennial grasses are a promising source of biomass for energy production in Southeast USA, and low-input production is desirable. With only residual fertility in the soil and no irrigation, this test compared biomass yields of eight grasses under low-input production: L 79–1002 energycane (Saccharum hyb.), Merkeron and N51 napiergrass (Pennisetum purpureum Schum.), three clones of giant reed (Arundo donax L.), and two switchgrass (Panicum virgatum L.) lines. For the first 2 years napiergrass maintained dry matter (DM) yields over 25 Mg DM ha−1 year−1, and energycane yielded over 20 Mg DM ha−1year−1 for 3 years. Switchgrass yields were lower (8.6 Mg DM ha−1 year−1 average of 4 years), but the biomass contained less moisture at harvest than the other, larger-stemmed grasses. Switchgrass biomass also had the lowest concentrations of N, K, and ash. Average yields of giant reeds were also low (6.4 Mg DM ha−1 year−1), while ash and N concentrations were relatively high compared with switchgrass and energycane. In 4 years of production, energycane and napiergrass removed between 269 and 386 kg N ha−1 and 830–1,159 kg K ha−1, while the other grasses removed significantly less of these nutrients. Giant reed removed 126 kg N ha−1 and 193 kg K ha−1, and switchgrass removed 83 kg N ha−1 and 140 kg K ha−1. In Southeast USA, it is possible to produce biomass from perennial grasses with minimal inputs but the high nutrient removal rates of some species suggest that it may not be sustainable for long periods of time.