Chemical Composition of the Aboveground Tissues of Miscanthus × giganteus and Relationships to Soil Characteristics

To reduce the C footprint of human activities, there is a growing need for alternative energy sources including the production of bioenergy feedstocks. Miscanthus × giganteus is a high yielding grass with low environmental impact and high potential for feedstock use. Studying the composition of the aboveground tissues of Miscanthus is important for understanding feedstock quality for biofuel conversion and how crop residue quality may affect soil input management. Data on Miscanthus leaf and stem chemistry including carbon (C), nitrogen (N), macronutrient concentrations, and the optical characteristics of the water extractable organic matter (WEOM) was analyzed to identify differences in composition between aboveground tissues and modeled to identify soil variables that may be correlated with tissue chemistry. Leaves and stems were dominated by N, potassium (K), calcium (Ca), phosphorus (P), and magnesium (Mg), but overall, the leaves contained higher nutrient concentrations compared to the stems. The leaves displayed elevated Si:K (0.0935) and Ca:K (0.445) ratios and lower C:N (36) and C:P (323) ratios compared to the stems (0.0560, 0.145, 150, and 645, respectively). Leaf WEOM contained large, aromatic, and complex structures, while the stem WEOM was dominated by small, recently produced structures. Varying relationships were found between tissue C and the mobile C pool in surface (0–15 cm) and deep (45–60 cm) soils. Overall, Miscanthus leaves had a chemical composition indicative of reduced biofuel quality compared to the stems. The relationships with soil mobile C suggest a dynamic linkage between Miscanthus physiology and this active soil C pool. These results have implications for crop nutrient allocation and nutrient management practices.