The objective of this study was to investigate the effect of the application of N fertilizer and the cutting age on the dry biomass production of elephant grass. The experiment was performed with the variety Paraíso and planted in a Ferralsol in 2008 in the district of Gurupi (State of Tocantins). Four different rates of urea application were tested (0, 50, 100 and 150 kg ha-1) and harvests were made at 120, 150 or 180 days after germination (DAG) of the setts. The dry matter and total N accumulation were evaluated. Dry matter production increased with dose of N, the greatest effect being observed at 180 DAG. There was a linear increase in dry matter (R² = 0.75**) and N accumulation (R² = 0.96**) permitting a productivity of 34 t ha-1 of dry matter and an accumulation of 471 kg N ha-1. The N utilization efficiency (biomass production per unit of applied N) increased with plant age. The higher efficiency of N use favored the quality of biomass production for energy production owing to the higher fibre content.
Pennisetum purpureum; biomass; bioenergy
