Site impacts nutrient translocation efficiency in intra- and interspecies miscanthus hybrids on marginal lands

Miscanthus, a C4 perennial rhizomatous grass, is capable of growing in varied climates and soil types in Europe, including on marginal lands. It can produce high yields with low nutrient inputs when harvested after complete senescence. Senescence induction and rate depend on complex genetic, environmental, and management interactions. To explore these interactions, we analysed four miscanthus hybrids (two novel seed-based hybrids, GRC 3 (M. sinensis × sinensis) and GRC 14 (M. sacchariflorus × sinensis); GRC 15, a novel M. sacchariflorus × sinensis clone; and GRC 9, a standard M. × giganteus clone) in Italy, Croatia, Germany and the UK.

Over all trial locations and hybrids, the average aboveground biomass of the three-year-old stands in August 2020 was 15 t DM ha-1 with nutrient contents of 7.6 mg N g-1 and 14.6 mg K g-1. As expected, delaying the harvest until spring reduced overall yield and nutrient contents (12 t DM ha-1, 3.3 mg N g-1 and 5.5 mg K g-1). At lower latitudes, the late-ripening M. sacchariflorus × sinensis GRC 14 and GRC 15 combined high yields with low nutrient contents. At the most elevated latitude location (UK), the early-ripening M. sinensis × sinensis combined high biomass yields with low nutrient offtakes. The clonal M. × giganteus with intermediate flowering and senescence attained similar low nutrient contents by spring harvest at all four locations.

Seasonal changes in yield and nutrient levels analysed in this study provide: 1) a first step towards recommending hybrids for specific locations and end uses in Europe; 2) crucial data for determination of harvest time and practical steps in the valorisation of biomass; and 3) key sustainability data for life cycle assessments. Identification of trade-offs resulting from genetic × environment × management interactions are critical for increasing sustainable biomass supply from miscanthus grown on marginal lands.