Nitrogen removal in switchgrass biomass under two harvest systems

Information is lacking on the nitrogen content of switchgrass (Panicum virgatum L.) biomass from different genotypes and management systems. Nitrogen removed in the biomass would be important in determining fertilization practices and biological degradation. Six switchgrass entries were grown for biomass yield under two harvest systems, one-cut: cut once near the end of October, and two-cut: cut in early summer and near the end of October. Dry matter yield, N concentration, and N content of biomass were determined for five years. More N was usually removed in the two-cut system than in the one-cut system. Nitrogen removed in the biomass exceeded N applied under the two- cut system in all years except one year with a severe summer drought. In the one-cut system N removed was less than applied in all years except when no N was applied in the last year. Nitrogen concentration was higher in the summer harvest than the fall harvest of the two-cut system. Nitrogen concentration in the fall harvest was lower for the one-cut than the two-cut system. Differences in N removed between harvest systems reflected the low N concentration of the fall harvest of the one-cut system and the higher N concentration in the summer harvest of the two-cut system. (C) 2000 Elsevier Science Ltd. All rights reserved.