Miscanthus Sinensis is as Efficient as Miscanthus × Giganteus for Nitrogen Recycling in spite of Smaller Nitrogen 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.

Seasonal decline in leaf photosynthesis in perennial switchgrass explained by sink limitations and water deficit

“…Even when soil VWC dropped by ~4-fold under the shelters, and A net decreased by up to ~26%. Other studies have found a stronger negative leaf photosynthesis response to water deficit ( Barney et al., 2009 ; Lovell et al., 2016 ; Taylor et al., 2016 ; Hawkes and Kiniry, 2018 ; Chen et al., 2020 ), including across 49 switchgrass genotypes in which decreased by 40 – 80% under drought stress ( Liu et al., 2015 ). This discrepancy may be because the control treatment in our field experiment (i.e., plants outside the shelter) experienced ambient environmental conditions, while other studies used irrigated plants as the control.…”

“…Few studies reporting changes in leaf carbohydrate under drought conditions in switchgrass suggest that the response may be specific to the particular storage carbohydrate. Key carbohydrates such as trehalose, fructose ( Liu et al., 2015 ), and proline ( Kim et al., 2016 ; Hoover et al., 2018 ) seem to be more readily affected, while other soluble sugars such as glucose or sucrose as well as starch remain relatively constant ( Hoover et al., 2018 ). Our work is distinct from earlier water deficit studies because we present diurnal and seasonal leaf carbohydrate measurements.…”

Photosynthetic decline in aging perennial grass is not fully explained by leaf nitrogen

“…However, older plants have larger root systems with which to mine soil N, and larger N pools that can be transferred to new buds to support initial growth in early spring. Spring N mobilization ranges between 23 kg ha −1 and 98 kg ha −1 have been reported ( Leroy et al , 2022 ), and these could be help mitigate the size-dependent N limitation, but little is known about the effects of N reserves on leaf N content over years. It is also possible that lower photosynthetic rates result from older plants allocating a larger proportion of N to non-photosynthetic functions as they age, but that is also poorly understood.…”

Nitrogen fertilization effects on aged Miscanthus × giganteus stands: Exploring biomass yield, yield components, and biomass prediction using in‐season morphological traits

“…The yield response to N application in Urbana is likely a result of the age of the stand and the concomitant N depletion during the preexperiment years (2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016)(2017) when no N was applied. Although miscanthus can effectively recycle N (Christian et al, 2006;Dierking et al, 2017;Dohleman et al, 2012;Leroy et al, 2022), biomass harvesting can deplete the soil and rhizome N; thus, additional fertilization is required to compensate for the loss (Kantola et al, 2022;Tejera et al, 2021). The different N responses in Pesotum can be attributed to differences in soil conditions compared with Urbana and/or differences in historical N management.…”