The Influence of Three Years of Supplemental Nitrogen on Above- and Belowground Biomass Partitioning in a Decade-Old Miscanthus × giganteus in the Lower Silesian Voivodeship (Poland)

Abstract

Because of the different opinions regarding nitrogen (N) requirements for Miscanthus × giganteus biomass production, we conducted an experiment with a set dose of nitrogen. The objective of this study was to examine the effects of nitrogen fertilization on the biomass yield, water content, and morphological features of rhizomes and aboveground plant parts in various terms during a growing season over the course of three years (2014–2016) in Lower Silesia (Wroclaw, Poland). The nitrogen fertilization (dose 60 kg/ha and control) significantly affected the number of shoots (p = 0.0018), the water concentration of rhizomes (p = 0.0004) and stems (p = 0.0218), the dry matter yield of leaves (p = 0.0000), and the nitrogen uptake (p = 0.0000). Nitrogen fertilization significantly affected the nitrogen uptake in all plant parts (p = 0.0000). Although low levels of nitrogen appeared to be important in maintaining the maximum growth potentials of mature Miscanthus × giganteus, the small reductions in the above- and belowground biomass production are unlikely to outweigh the environmental costs of applying nitrogen. More studies should use the protocols for the above- and belowground yield determination described in this paper in order to create site- and year-specific fertilizer regimes that are optimized for quality and yield for autumn (green) and spring (delayed) harvests.