Nitrogen Fertilization Response of Dedicated Bioenergy Sorghums in North Carolina.

The eastern North Carolina Coastal Plain region provides a unique opportunity for the establishment of bioenergy crops. Information on agronomic management practices, such as N fertilization, is critical to maximize dry matter (DM) production and improve nutrient management practices. Our objectives were to determine DM production, plant tissue nutrient concentration, and nutrient removal of two dedicated bioenergy sorghums. The study was conducted over two growing seasons (2012 and 2013) at the Williamsdale Research Station in Duplin County, North Carolina. Sorghum entries Blade ES5200 (biomass-type) and M81E (sweet sorghum-type) were fertilized with 0, 67, 134, 201, and 268 kg N ha^-1 yr^-1. For Blade ES5200, increasing N application resulted in a linear increase for: DM production (13.7 to 17.4 Mg ha yr^-1), plant tissue N concentration (6.9 to 8.6 g kg^-1), and N removal (95.6 to 151.2 kg ha^-1). Plant tissue P concentration decreased linearly with increasing N rate (1.9 to 1.5 g kg^-1). There was no treatment effect on K concentration (15.1 g kg^-1) or on P or K removal (26.6 and 239.55 kg ha^-1, respectively). For sorghum M81E, N and K removal increased linearly with increasing N rate (67.8 to 100 kg ha^-1 for N and 124.1 to 164.7 kg ha^-1 for K), but there was no effect on DM production (11.5 Mg ha^-1), N, P, or K plant tissue concentration (7.2, 1.5, and 12.4 g kg^-1, respectively), and P removal (17 kg ha^-1).  The results indicated that there are differences in N response of sorghum types. The data will contribute to establishing best management practices for the production of bioenergy sorghums in North Carolina.