BIOMASS YIELD OF TALL GRASS ENERGY CROPS ON PHOSPHATIC CLAY IN CENTRAL FLORIDA

Accessions of elephantgrass (Pennisetum purpureum Schum.), sugarcane ( Saccharum spp.), energycane (Saccharum spp.), and erianthus [Erianthus arundenaceum (Retz) Jesw.] were planted on phosphatic clay soil in Au gust 1986. Plots were harvested one time per year in December or janua ry during 1987, 1988, 1989, and 1990. Fertilizer was applied once annu ally at the rate of 100 lb acre-1 of N in 1987 and 120 lb acre-1 in su cceeding years. Average annual dry matter (DM) yield over the 4-yr per iod was 16.2 ton acre-1 yr-1 for PI 300086 elephantgrass and 20.2 for N51 etephantgrass. Mean DM yield for energycane accessions was 19 ton acre-1 yr-1 for L79-1002 and 21.8 for US72-1153. Yields for sugarcane entries were 22.2 ton acre-1 yr-1 for US 78-1009, 23.3 for US 56-9, an d 25.1 for CP72-1210. Erianthus (IK-7647) produced a mean dry yield of 21.8 ton acre-1 over a 3-yr period. Individual crops averaged 18.2 to n acre-1 of dry biomass for elephantgrass, 20.4 for energycane and 23. 5 for sugarcane over the 4-yr period. Yield trends for PI 300086 eleph antgrass, US72-1153 energycane, US56-9, and CP72-1210 sugarcanes were higher over the period while trends for N51 elephantgrass, L79-1002 en ergycane, and US78-1009 sugarcane were lower. There was no discernable yield trend for the erianthus genotype IK-7647. The high yields of th ese tall bunch grasses grown on phosphatic clay indicate a great poten tial as a major source of renewable energy.