Miscanthus Sinensis is as Efficient as Miscanthus × Giganteus for Nitrogen Recycling in Spite of Smaller N Fluxes

Abstract Nitrogen (N) recycling is a key mechanism to ensure the sustainability of miscanthus production with no or small fertiliser inputs, but little is known on the subject in miscanthus species other than the most cultivated Miscanthus × giganteus. This field experiment on Miscanthus × giganteus and Miscanthus sinensis quantified plant biomass and N stock dynamics during two years. Endogenous net N fluxes, calculated by the difference in plant N content throughout time, were higher in Miscanthus × giganteus than in Miscanthus sinensis. Indeed, 79 kg N ha-1 and 105 to 197 kg N ha-1 were remobilized during spring and autumn respectively for Miscanthus × giganteus, as opposed to 13 to 25 kg N ha-1 and 46 to 128 kg N ha-1 for Miscanthus sinensis. However, their N recycling efficiency, defined as the ratio between N remobilisation fluxes and the maximum above-ground N content, did not differ significantly. It ranged from 8 to 27% for spring remobilisation and from 63 to 74% and 24 to 38% for autumn remobilization calculated on above-ground and below-ground N respectively. Exogenous N, the main source of N to constitute maximum plant N content for all genotypes, was provided by fertilisation (22 to 24%) and organic matter mineralisation or other sources (43 to 59%). During winter, 50 to 56% of plant N content was lost. Abscised leaves constituted an additional loss of 6 to 12%. Our results show that Miscanthus sinensis is as efficient as Miscanthus × giganteus and as performant as other perennial species concerning N functioning.