Effect of nitrogen fertilization on carbon accumulation by Miscanthus × giganteus in both above and below ground

Abstract

Miscanthus is known for its high biomass yield and carbon accumulation, with requirement of relatively low nitrogen fertilizer. Little effort has been made to investigate the effects of nitrogen fertilizer on biomass yield and carbon accumulation. Therefore, this study was conducted to investigate the effects of nitrogen fertilization on biomass yield and carbon accumulation in the above- and below-ground parts of M. × giganteus. Miscanthus plants were cultivated under different fertilizations, 0, 30, 60, 120, and 240 kg N ha-1 year-1, for 6 years. Above-ground biomass yield were assessed every year at harvest in early March. Below-ground biomass including rhizomes and roots was harvested and assessed in the 6th year, when above-ground biomass debris was also assessed. Soil was sampled in the 6th year and total carbon content in soil was analyzed. Cumulative above-ground biomass increased with increasing nitrogen fertilizer level with significant differences between non-fertilized treatment and fertilized treatments. Below-ground biomass also increased with increasing nitrogen fertilizer level up to 60 kg N ha-1 year-1, and thereafter decreased with increasing nitrogen fertilizer level. However, no significant increase in soil total carbon (TC) was observed with nitrogen fertilizer level. In total, carbon accumulated in both above- and below-ground parts of miscanthus for 6 years increased with nitrogen fertilization although soil total carbon was not significantly increased by nitrogen fertilization. Linear regression analysis between nitrogen fertilization and carbon accumulation by miscanthus revealed that miscanthus could accumulate 27.23 t ha-1 annually even at no nitrogen fertilization. Carbon accumulation per unit nitrogen fertilization was estimated to be 0.021 t carbon ha-1 per kg N ha-1.