Nutrient and Water Requirements for Elephantgrass Production As a Bio-Fuel Feedstock.

Elephantgrass (Pennisetum purpureum Schumacher) is a tall tropical bunch grass that produces very high biomass yields and is considered an excellent bio-energy feedstock for the lower South.  However, previous studies have shown that production is not sustainable without fertilizer application and adequate soil moisture.  The objective of one study was to determine the effects of N (three levels) and K (two levels) fertilizer and irrigation (0, 1.1, or 2.2 cm wk^-1) on ‘Merkeron’ elephantgrass at Shellman, GA.  The yield one year after establishment did not vary among fertilizer treatments but was significantly greater for plots receiving 1.1 cm irrigation wk^-1 (29 Mg ha^-1) versus rainfed (21.7 Mg ha^-1).   Second year yields for this study did not vary among fertilizer applications but were higher for 2.2 cm (35.4 Mg ha^-1) and 1.1 cm (33.4 Mg ha^-1) irrigation wk^-1 versus rainfed (26.4 Mg ha^-1).  The C/N uptake ratios were higher for irrigated plots in both years and highest under moderate levels of N and higher K fertilizer rates in year 2.  Excessive rainfall in year three caused significant lodging in August requiring early harvest.  These issues will be addressed in consideration of grower concerns and possible recommendations.