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, and energycane yielded over 20 Mg DM ha 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), 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

Pennisetum purpureum Schum. (napiergrass) is a perennial grass used for forage especially in South America and Africa. Over the last 30 years, a USDA -ARS nursery containing accessions collected from all over the world has been established in Tifton, Georgia. The study reported here was conducted to assess the molecular genetic variation and genetic relatedness among 89 accessions from the Tifton nursery using amplified fragment length polymorphism markers, morphological data and ploidy level. Using 218 polymorphic markers from eight selective primer combinations, the 89 accessions were clustered into five groups using a principal components analysis and a dendrogram based on Dice similarity estimates and unweighted pair group method with arithmetic average clustering. These five groups include three groups collected from Kenya, a group from Puerto Rico, and accessions derived from the cultivar Merkeron. This research provides the first molecular characterization of the Tifton nursery, displays the relationships between accessions, and provides potential heterotic groups for napiergrass and pearl millet (Pennisetum glaucum (L.) R. Br.) breeding improvement.

Napiergrass (Pennisetum purpureum Schum.) is a high-yielding perennial biomass crop that is well adapted to the Southeast USA where poultry litter is readily available. This research was conducted to compare biomass production and nutrient utilization of napiergrass fertilized with either poultry litter or inorganic fertilizer. Each spring, approximately 100 kg ha −1 of N, 40 kg ha −1 P, and 90 kg ha −1 K were applied as poultry litter or equivalent inorganic fertilizer. Biomass was harvested each winter after senescence. For the first 2 years, dry matter yield did not differ among treatments, but in the third and fourth years, yields declined in all treatments and were lowest in the unfertilized treatment. Biomass N concentration and N removal were greatest in the inorganic treatment. In general, N removal exceeded the amount applied, suggesting that higher application rates may be necessary to maintain yields. Biomass P concentration and total P uptake were greatest in the litter fertilized treatment, demonstrating that napiergrass can remove some of the excess P from applied litter. Soil cores were taken periodically to assess changes in soil properties. After 2 years of production, soil pH in the surface layer (0-15 cm) was lower in the inorganic treatment than in the other treatments. After 4 years, total soil C had increased by an average of 3,180 kg ha −1 though fertilizer treatments did not differ. Yield declined in all treatments after 4 years and N supplementation is recommended for production in upland fields.