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Miscanthus, a C4 perennial rhizomatous grass, is a low-input energy crop suitable for marginal land, which cultivation can improve soil quality and promote soil organic carbon (SOC) sequestration. In this study, four promising Miscanthus hybrids were chosen to evaluate their short-term potential, in six European marginal sites, to sequester SOC and improve physical, chemical, and biological soil quality in topsoil. Overall, no differences among Miscanthus hybrids were detected in terms of impacts on soil quality and SOC sequestration. SOC sequestration rate after 4 years was of +0.4 Mg C ha−1 year−1, but land-use transition from former cropland or grassland showed contrasting SOC sequestration trajectories. In unfertilized marginal lands, cultivation of high-yielding Miscanthus genotypes caused a depletion of K (−216 kg ha−1 year−1), followed by Ca (−56 kg ha−1 year−1), Mg (−102 kg ha−1 year−1) and to a lesser extent of N. On the contrary, the biological turnover of organic matter increased the available P content (+164 kg P2O5 ha−1 year−1). SOC content was identified as the main driver of changes in biological soil quality. High input of labile plant C stimulated an increment of microbial biomass and enzymatic activity. Here, a novel approach was applied to estimate C input to soil from different Miscanthus organs. Despite the high estimated plant C input to soil (0.98 Mg C ha−1 year−1), with significant differences among sites and Miscanthus hybrids, it was not identified as a driver of SOC sequestration. On the contrary, initial SOC and nutrients (N, P) content, as well as their elemental stoichiometric ratios with C, were the key factors controlling SOC dynamics. Introducing Miscanthus on marginal lands impacts positively soil biological quality over the short term, but targeted fertilization plans are needed to secure crop yield over the long term as well as the C sink capacity of this perennial cropping system.

New biomass crop hybrids for bioeconomic expansion require yield projections to determine their potential for strategic land use planning in the face of global challenges. Our biomass growth simulation incorporates radiation interception and conversion efficiency. Models often use leaf area to predict interception which is demanding to determine accurately, so instead we use low-cost rapid light interception measurements using a simple laboratory-made line ceptometer and relate the dynamics of canopy closure to thermal time, and to measurements of biomass. We apply the model to project the European biomass potentials of new market-ready hybrids for 2020–2030. Field measurements are easier to collect, the calibration is seasonally dynamic and reduces influence of weather variation between field sites. The model obtained is conservative, being calibrated by crops of varying establishment and varying maturity on less productive (marginal) land. This results in conservative projections of miscanthus hybrids for 2020–2030 based on 10% land use conversion of the least (productive) grassland and arable for farm diversification, which show a European potential of 80.7–89.7 Mt year−1 biomass, with potential for 1.2–1.3 EJ year−1 energy and 36.3–40.3 Mt year−1 carbon capture, with seeded Miscanthus sacchariflorus × sinensis displaying highest yield potential. Simulated biomass projections must be viewed in light of the field measurements on less productive land with high soil water deficits. We are attempting to model the results from an ambitious and novel project combining new hybrids across Europe with agronomy which has not been perfected on less productive sites. Nevertheless, at the time of energy sourcing issues, seed-propagated miscanthus hybrids for the upscaled provision of bioenergy offer an alternative source of renewable energy. If European countries provide incentives for growers to invest, seeded hybrids can improve product availability and biomass yields over

The cultivation of perennial biomass crops (PBCs) on marginal lands is necessary to provide feedstock for the bio-based EU economy and accrue environmental benefits through carbon (C) sequestration in soil. Short rotation coppice (SRC) species, e.g., willow, black locust, and poplar, and perennial rhizomatous grasses, e.g., miscanthus, switchgrass, and giant reed, have been tested in many EU projects in the last 10 years to investigate their productive potential and contribution to the mitigation of climate change. A major knowledge gap regarding PBCs is the fate of accumulated soil organic carbon (SOC), once PBC plantations are reverted to arable crops. In this study, the effects of PBCs reversion on SOC and carbon-dioxide emission (CO2) were monitored over a 2-year period in a long-term (11-year) multispecies trial of six PBCs: Three SRC species including poplar (Populus spp.), willow (Salix spp.), and black locust (Robinia pseudoacacia), and three herbaceous rhizomatous grasses including miscanthus (Miscanthus x giganteus), switchgrass (Panicum virgatum), and giant reed (Arundo donax). The SOC change and GHG emissions were then modeled with the ECOSSE model. Two years after the reversion, SOC increased significantly for all PBCs with no significant difference between them. During the PBC cultivation phase, 5.35 Mg SOC ha−1 was sequestered while 10.95 Mg SOC ha−1 was added by reversion, which indicated that 67% of SOC sequestration occurred after the reversion. The ECOSSE model was successfully used to simulate SOC sequestration trajectories (R2 = 0.77) and CO2 emission from soil (R2 = 0.82) after the reversion of the six PBCs. This indicated that the high SOC sequestration rate after the reversion was due to humification of belowground biomass (roots + rhizomes/stumps), which had been mulched and incorporated into the reversion layer (0–30 cm). This occurred in the first 2 months (on average 5.47 Mg SOC ha−1 y−1) and in the first year after the reversion (1.3–1.8

Miscanthus, a C4 perennial rhizomatous grass from Asia is a leading candidate for the supply of sustainable biomass needed to grow the bioeconomy. European Miscanthus breeding programmes have recently produced a new range of seeded hybrids with the objective of increasing scalability to large acreages limited by current clonal propagation. For the EU-GRACE project, new replicated field trials were established in seven locations across Europe in 2018 with eight intraspecific M. sinensis hybrids (sin × sin) and six M. sacchariflorus × M. sinensis (sac × sin) from Dutch and UK breeding programmes, respectively, with clonal Miscanthus × giganteus. The planting density of the sin × sin was double that of sac × sin (30,000 & 15,000 plants ha−1), creating commercially relevant upscaling comparisons between systems. Over the first 3 years, the establishment depended on location and hybrid. The mature sin × sin hybrids formed tight tufts of shoots up to 2.5 m tall which flower and senesce earlier than the taller sac × sin hybrids. Following the third growing season, the highest yields were recorded in Northern Italy at a low altitude (average 13.7 (max 21) Mg DM ha−1) and the lowest yielding was on the industrially damaged marginal land site in Northern France (average 7.0 (max 10) Mg DM ha−1). Moisture contents at spring harvest were lowest in Croatia (21.7%) and highest in Wales, UK (41.6%). Overall, lower moisture contents at harvest, which are highly desirable for transport, storage and for most end-use applications, were found in sin × sin hybrids than sac × sin (30% and 40%, respectively). Yield depended on climate interactions with the hybrid and their associated planting systems. The sin × sin hybrids appeared better adapted to northern Europe and sac × sin hybrids to southern Europe. Longer-term yield observations over crop lifespans will be needed to explore the biological (yield persistence) and economic costs and benefits of the different hybrid systems.

Due to its versatility and storability, biomass is an important resource for renewable materials and energy. Miscanthus hybrids combine high yield potential, low input demand, tolerance of certain marginal land types and several ecosystem benefits. To date, miscanthus breeding has focussed on increasing yield potential by maximising radiation interception through: (1) selection for early emergence, (2) increasing the growth rate to reach canopy closure as fast as possible, and (3) delayed flowering and senescence. The objective of this study is to compare early season re-growth in miscanthus hybrids cultivated across Europe. Determination of differences in early canopy development on end-of-year yield traits is required to provide information for breeding decisions to improve future crop performance. For this purpose, a trial was planted with four miscanthus hybrids (two novel seed-based hybrids M. sinensis × sinensis [M sin × sin] and M. sacchariflorus × sinensis [M sac × sin], a novel rhizome-based M sac × sin and a standard Miscanthus × giganteus [M × g] clone) in the UK, Germany, Croatia and Italy, and was monitored in the third and fourth growing season. We determined differences between the hybrids in base temperature, frost sensitivity and emergence strategy. M × g and M sac × sin mainly emerged from belowground plant organs, producing fewer but thicker shoots at the beginning of the growing season but these shoots were susceptible to air frosts (determined by recording 0°C 2 m above ground surface). By contrast, M sin × sin emerged 10 days earlier, avoiding damage by late spring frosts and producing a high number of thinner shoots from aboveground shoots. Therefore, we recommend cultivating M sac × sin at locations with low risk and M sin × sin at locations with higher risk of late spring frosts. Selecting miscanthus hybrids that produce shoots throughout the vegetation period is an effective strategy to limit the risk of l

Miscanthus, a C4 perennial rhizomatous grass from Asia is a leading candidate for the supply of sustainable biomass needed to grow the bioeconomy. European Miscanthus breeding programmes have recently produced a new range of seeded hybrids with the objective of increasing scalability to large acreages limited by current clonal propagation. For the EU-GRACE project, new replicated field trials were established in seven locations across Europe in 2018 with eight intraspecific M. sinensis hybrids (sin × sin) and six M. sacchariflorus × M. sinensis (sac × sin) from Dutch and UK breeding programmes, respectively, with clonal Miscanthus × giganteus. The planting density of the sin × sin was double that of sac × sin (30,000 & 15,000 plants ha−1), creating commercially relevant upscaling comparisons between systems. Over the first 3 years, the establishment depended on location and hybrid. The mature sin × sin hybrids formed tight tufts of shoots up to 2.5 m tall which flower and senesce earlier than the taller sac × sin hybrids. Following the third growing season, the highest yields were recorded in Northern Italy at a low altitude (average 13.7 (max 21) Mg DM ha−1) and the lowest yielding was on the industrially damaged marginal land site in Northern France (average 7.0 (max 10) Mg DM ha−1). Moisture contents at spring harvest were lowest in Croatia (21.7%) and highest in Wales, UK (41.6%). Overall, lower moisture contents at harvest, which are highly desirable for transport, storage and for most end-use applications, were found in sin × sin hybrids than sac × sin (30% and 40%, respectively). Yield depended on climate interactions with the hybrid and their associated planting systems. The sin × sin hybrids appeared better adapted to northern Europe and sac × sin hybrids to southern Europe. Longer-term yield observations over crop lifespans will be needed to explore the biological (yield persistence) and economic costs and benefits of the different hybrid systems.

Miscanthus holds a great potential in the frame of the bioeconomy, and yield prediction can help improve Miscanthus’ logistic supply chain. Breeding programs in several countries are attempting to produce high-yielding Miscanthus hybrids better adapted to different climates and end-uses. Multispectral images acquired from unmanned aerial vehicles (UAVs) in Italy and in the UK in 2021 and 2022 were used to investigate the feasibility of high-throughput phenotyping (HTP) of novel Miscanthus hybrids for yield prediction and crop traits estimation. An intercalibration procedure was performed using simulated data from the PROSAIL model to link vegetation indices (VIs) derived from two different multispectral sensors. The random forest algorithm estimated with good accuracy yield traits (light interception, plant height, green leaf biomass, and standing biomass) using a VIs time series, and predicted yield using a peak descriptor derived from a VIs time series with 2.3 Mg DM ha−1 of the root mean square error (RMSE). The study demonstrates the potential of UAVs’ multispectral images in HTP applications and in yield prediction, providing important information needed to increase sustainable biomass production.

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 [Miscanthus sinensis × sinensis] and GRC 14 [M. sacchariflorus × sinensis]; GRC 15, a novel M. sacchariflorus × sinensis clone; and GRC 9, a standard Miscanthus × giganteus clone) in Italy, Croatia, Germany and the UK. Over all trial locations and hybrids, the average aboveground biomass of the 3-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 Miscanthus × 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 valorization of biomass; and (3) key sustainability data for life cycle assessments. Identification of trade-offs resulting from genetic × environment × management interactions is critical for increasing sustainable biomass supply from miscanthus grown on marginal lands.

Miscanthus, a C-4 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 [Miscanthus sinensis x sinensis] and GRC 14 [M. sacchariflorus x sinensis]; GRC 15, a novel M. sacchariflorus x sinensis clone; and GRC 9, a standard Miscanthus x giganteus clone) in Italy, Croatia, Germany and the UK. Over all trial locations and hybrids, the average aboveground biomass of the 3-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 x 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 x sinensis combined high biomass yields with low nutrient offtakes. The clonal Miscanthus x 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 valorization of biomass; and (3) key sustainability data for life cycle assessments. Identification of trade-offs resulting from genetic x environment x management interactions is critical for increasing sustainable biomass supply from miscanthus grown on marginal lands.

Perennial crops have been proposed as a solution to couple the production of sustainable biomass for multiple uses with several environmental benefits such as soil C storage. Concerns exist that the C sequestered in soil could be lost in a few years after the perennial crops are reverted to arable land. In this study, the current knowledge on the effects of perennial crop reversion on soil C and N was summarized by performing a meta-analysis. One year after the reversion a significant increase of soil C and N stocks (+15% and +12% respectively) were found in the 0–30 cm layer, while in the time interval between the second to fifth year after the reversion, there were no significant increases or decreases of soil C and N. The incorporation of the belowground biomass (BGB) into the soil at reversion plays a key role in the fate of soil C and N stocks after the reversion. In fact, when reverting a multiannual biomass crop there are significant losses of soil C and N. In contrast, when reverting a perennial biomass crop (PBCs) such as rhizomatous herbaceous or SRC woody crops there are no losses of soil C and N. The BGB of perennial grass is mainly composed of root systems and not of a huge amount of belowground organs as in the case of PBCs. The shredding of the BGB and its transformation as particulate organic matter (POM) represent the major pulse C input at the reversion that can undergo further stabilization into a mineral-associated organic matter (MAOM) fraction. Introducing PBCs into crop rotation resulted in an effective carbon farming solution with a potential positive legacy for food crops in terms of achievement of both climate and soil fertility goals.

The objective of this work was to assess the environmental performances of advanced biofuels produced from perennial energy crops (miscanthus and willow) grown in bioenergy buffer strips (BBS) and compare them with the environmental performances of alternative systems providing the same function, i.e. private mobility. The growing evidence of potentially negative environmental impacts of bioenergy pathways calls for renewed efforts in identifying win-win bioenergy pathways, thus capable of mitigating climate change without worsening other environmental impacts. An holistic approach encompassing all the relevant areas of environmental concern is thus fundamental to highlight environmental trade-offs. Therefore, in this study we follow an attributional Life Cycle Assessment approach, but our analysis includes detailed modelling of biogenic carbon pools, nutrients cycles, infrastructures’ impacts as well as the expansion of the system boundaries to include the fuel use. We find that the fragmented and linear configuration of the buffer strips does not affect significantly the GHG emissions of lignocellulosic ethanol for BBS compared to growing the crops in open field. Additionally, we find that ethanol from perennials grown in BBS has the potential to reduce several other environmental impacts associated to private mobility. Firstly, the cultivation of miscanthus and willow in BBS enables both the removal of nutrients from the environment and the removal of carbon from the atmosphere, through the creation of an additional terrestrial sink. Secondly, when compared to the use of fossil gasoline, bioethanol from BBS crops generates lower impacts on all other areas of environmental concern, such as resources depletion or air pollution. We also find that cars fuelled with bioethanol form buffer strips perform even better than electric vehicles in all the impact categories analysed except for acidification and particulate matter emissions, where battery electric vehicles run

The cultivation of Perennial Energy Crops (PECs) couples the production of ligno-cellulosic biomass to the provision of multiple ecosystem services, such as the reduction of greenhouse gas emissions and the mitigation of climate change through carbon (C) sequestration in soil. Though C sequestration in soil by PECs has been widely studied, the contribution of their belowground biomass (BGB) to soil C sequestration and their influence on soil nitrogen (N) storage potential has received very little attention. In this study, C and N stocks in soil and BGB fractions (plant belowground organs and fine roots) was measured for six PECs (Populus spp. “Poplar”, Robinia pseudoacacia “Black locust”, Sa-lix spp. “Willow”, Arundo donax “Giant reed”, Miscanthus x giganteus “Miscanthus”, and Panicum virgatum “Switchgrass”) grown on marginal soil, eleven years after establishment. All PECs had a higher soil organic carbon (SOC) stock and soil total nitrogen (STN) stock than arable land in the top (0-10 cm) soil layer. In this same top layer, woody crops had the highest SOC stock. The increase of SOC under PECs led to increased soil porosity in the top-soil layer. On average, 43% of the below-ground C stock of PECs was allocated in the plant belowground organs (PBO) (i.e in the rhizomes of herbaceous PECs and the stump for woody PECs). Giant reed had the highest C stock in PBO, while switchgrass the lowest (22.7 vs 5.9 Mg C ha-1). On the contrary, switchgrass had the highest C stock in fine roots. Giant reed had the highest belowground C stock (sum of soil and BGB contribution) and black locust the highest belowground N stock. After eleven years of PEC cultivation, 68% of the belowground C stock was allocated in the BGB, and 32% was as SOC.

C input to soil together with plant-microbial-soil organic matter (SOM) transformations are key ecological drivers for soil functioning in perennial cropping systems. In this study, we assessed the effect of three woody (poplar, black locust, willow) and three herbaceous (giant reed, miscanthus, switchgrass) perennial energy crops (PECs) on SOM pools, soil microbial biomass and metabolism and soil P forms distribution. After 9 y from plantation on a low-grade arable land, PECs significantly increased SOM content as much as 3.9 g kg− 1 (+23 %) in the topsoil (0− 30 cm). At the same time active C increased by 194 mg kg− 1 (+ 43 %) and microbial biomass by 10.7 mg g− 1 (+ 80 %). Microbial catabolic activity as measured respectively with twenty enzymes activities (EA) involved in C-, N-, P-, and S- cycling increased by 90 % and C substrate utilization profile (CSU - MicrorespTM) showed an increase of respiration rate by 13 % on average of all 16 substrates utilized. PERMANOVA and dbRDA analysis indicated that activity of microbial community associated with PECs differed significantly from that of arable land, with herbaceous PECs significantly increasing EA involved in C and N cycling while woody PECs increasing those involved in P-cycling. Interestingly, organic P forms content (monoester- and diester-P) along with its contribution to total NaOH-EDTA extractable soil P increased in all PECs, but more in woody than herbaceous ones. Functional diversity and evenness of microbial community resulted higher under herbaceous than woody PECs. Depth decay relationships of Bray Curtis similarity for EA patterns, more than CSU profile, was signifi- cantly smaller in woody and arable land than in herbaceous PECs, indicating a significant control of plant C inputs to soil from deep-rooting systems on proximate agents of belowground functioning. Our investigation highlighted the higher capability PECs, compared to annual cropping systems, in coupling nutrients cycling with C cyclin