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Marginal lands are an untapped source of agricultural potential, particularly regarding high‐yielding, low‐input bioenergy crops like Miscanthus × giganteus (Miscanthus). Miscanthus is of specific interest because it can be productive and sequester carbon in soil even under the stressful conditions present on some degraded lands. A key component of these abilities is the interaction of Miscanthus with its soil and root microbiome. Microbial functions depend on the nutrient status of soil, and hence are sensitive to fertilization regimes. Nevertheless, little is known about how fertilization strategies affect the partnership of Miscanthus with its microbial associates. Here, we tested the individual and interactive effects of nutrient addition and bioaugmentation (i.e., the addition of microbial communities) on Miscanthus performance and microbiome function in marginal soil. We found that the effect of nutrient addition on Miscanthus biomass yield depended on nutrient addition type (i.e., organic or inorganic nutrients) and whether bioaugmentation was also applied. Some microbial functions, like free‐living nitrogen fixation and carbon use efficiency, were sensitive to nutrient addition depending on whether bioaugmentation was also applied. On the other hand, arbuscular mycorrhizal fungus colonization of roots decreased with fertilization regardless of bioaugmentation. These results imply that managing microbial communities may regulate the effect of nutrient addition on plant–microbe interactions that in part determine system productivity and environmental impact. We tested the interactive effect of nutrient addition and bioaugmentation on plant performance, plant–microbe interactions, and soil carbon and nitrogen contents in a Miscanthus × giganteus agroecosystem. We observed that plant–microbe interactions remained strong in response to nutrient addition when bioaugmentation was also applied, but were weakened by nutrient addition in the absence of bioaugmentation. This work indicates that managing microbial community structure may regulate the impacts of nutrient addition; these dynamics are consequential for agroecosystem productivity and environmental impacts.

Miscanthus × giganteus (Miscanthus) is a warm-season perennial grass grown for bioenergy feedstock production. Nitrogen (N) fertilizer management is crucial for the sustainability of Miscanthus production. In our two-year study (2018 and 2019), we investigated the role of vegetation indices (VIs) in evaluating N fertilization (0 N, 56 N, 112 N, and 168 N kg ha−1) impacts on Miscanthus biomass yield and stand health. The flight campaigns were conducted early, middle, and late during the summer growing season. Among the VIs, mid-summer growing season NDRE provided the best prediction of fresh biomass (R2 = 0.87 and 0.97) and dry biomass (R2 = 0.89 and 0.97) in 2018 and 2019, respectively. The VIs generally showed that it was possible to distinguish between 0 N and 168 N treatments, but neither 0 N and 56 N kg ha−1 nor 112 N and 168 N kg ha−1 could be separated. The results from this study highlight the importance of moderate application of N (112 kg N ha−1) in improving and maintaining the stand health and biomass yield of Miscanthus over time and suggest that mid-summer growing season VIs, NDRE in particular, can be useful for assessment of Miscanthus stand health and biomass yield.

Bacterial assemblages, especially diazotroph assemblages residing in the rhizomes and the rhizosphere soil of Miscanthus × giganteus, contribute to plant growth and nitrogen use efficiency. However, the composition of these microbial communities has not been adequately explored nor have the potential ecological drivers for these communities been sufficiently studied. This knowledge is needed for understanding and potentially improving M. × giganteus – microbe interactions, and further enhancing sustainability of M. × giganteus production. In this study, cultivated M. × giganteus from four sites in Illinois, Kentucky, Nebraska, and New Jersey were collected to examine the relative influences of soil conditions and plant compartments on assembly of the M. × giganteus‐associated microbiome. Automated ribosomal intergenic spacer (ARISA) and terminal restriction fragment length polymorphism (T‐RFLP) targeting the nifH gene were applied to examine the total bacterial communities and diazotroph assemblages that reside in the rhizomes and the rhizosphere. Distinct microbial assemblages were detected in the endophytic and rhizosphere compartments. Site soil conditions had strong correlation with both total bacterial and diazotroph assemblages, but in different ways. Nitrogen treatments showed no significant effect on the composition of diazotroph assemblages in most sites. Endophytic compartments of different M. × giganteus plants tended to harbor similar microbial communities across all sites, whereas the rhizosphere soil of different plant tended to harbor diverse microbial assemblages that were distinct among sites. These observations offer insight into better understanding of the associative interactions between M. × giganteus and diazotrophs, and how this relationship is influenced by agronomic and edaphic factors.

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 is a leading candidate for the supply of sustainable biomass. Breeding programmes have recently produced the first range of seeded hybrids to increase scalability. We established eight intraspecific M. sinensis hybrids and six M. sacchariflorus × M. sinensis hybrids including commercial clonal Miscanthus × giganteus at seven sites across Europe with marginal land. The highest yields were recorded in Northern Italy and the lowest on industrially damaged land in Northern France. Yield depended on climate interactions with the hybrid, with the sinensis hybrids better adapted to northern Europe.

For sustainable biomass production of Miscanthus × giganteus (hereafter miscanthus), understanding the impact of stand age and nitrogen (N) fertilization on biomass yield is crucial. This study investigated the effects of varying N fertilization rates (0, 56, 112, and 168 kg N ha−1) on yield components (tiller height, density, and weight) and their correlations with end‐of‐season biomass yield in miscanthus. We also explored end‐of‐season biomass yield prediction using in‐season traits (canopy height, leaf area index, and leaf chlorophyll content [LCC]). The study was conducted at two sites in Illinois: a previously unfertilized 10‐year‐old miscanthus research stand at Urbana and a 16‐year‐old commercial stand at Pesotum with a history of annual 56N application. Results from 2018 to 2021 in Urbana and 2020 to 2021 in Pesotum showed increased biomass yields with N fertilization, varying by rate, year, and location. Biomass yield in Pesotum peaked at 56N, while in Urbana, it increased significantly at 112 kg N ha−1. Biomass yield was strongly correlated with tiller height and weight measured at Urbana across N rates. Morphological traits measured every 2–3 weeks during the 2020 and 2021 growing seasons showed that canopy height was the strongest single predictor of miscanthus biomass yield, followed by LCC. Mid‐August to September measurements of these traits were the best predictors of biomass yield. Multiple regressions involving the canopy height and LCC further improved yield predictions. We conclude that while N enhances biomass yields of aging miscanthus, the optimum rate depends on the site, environmental conditions, and management history. Nitrogen enhances the biomass yield of mature miscanthus, but optimum rates may vary depending on site‐specific factors, environmental conditions, and management history.

Different agricultural practices can be beneficial in Miscanthus  ×  giganteus ( M  ×  g ) phytotechnology applied to post-military and post-mining lands. However, only limited research has focused on supportive treatments using biochar produced from M  ×  g waste. Indeed, when M  ×  g phytotechnology is applied to contaminated soil, the biochar produced through the pyrolysis of the obtained biomass is contaminated, raising concerns about its further application. The current study tested the use of biochar produced from M  ×  g roots cultivated long-term in slightly contaminated soil in the M  ×  g phytotechnology of Cu- or Zn-spiked soils which is important for finding the solution toward valorization of the contaminated biomass. Two biochar doses (1.67 and 5.00%) were evaluated with varying levels of Cu (200 to 416 mg kg −1 ) or Zn (202 to 580 mg kg −1 ) concentrations in the soils. This study revealed a beneficial influence of biochar on M  ×  g development, specifically by increasing the plant height and aboveground biomass by up to 20.4 and 115%, respectively. However, the root dry weight increased by 31.8% only at the highest application rate of biochar. The option for valorization of the contaminated biochar in the next phytoremediation process applied to soil contaminated more than the biochar itself was tested. The finding showed the positive influence of biochar on the M  ×  g phytoremediation metrics such as tolerance index, bioconcentration factor, translocation factor, and comprehensive bioconcentration index which ensured the perspective of the proposed approach in the implementation of post-remediation management practice.  

The multiyear cultivation of Miscanthus × giganteus Greef et Deu ( M. × giganteus ) at the soils polluted by metal(loid)s were researched. The biomass parameters and concentrations of elements: Ti, Mn, Fe, Cu, Zn, As, Sr, and Mo were determined in the plant’s organs at harvest. The same metal(loid)s were monitored in the plant’s leaves throughout three vegetation seasons. The principal component analysis and general linear model approaches were applied for statistical evaluation followed by Box-Cox transformation. The difference in the distribution of elements in the plant, the content of elements in the soil, various regime of uptake to the plant tissues, and the year of vegetation were analyzed as driving factors of the phytoremediation. The results showed that the leading promoter was the factor of the zone, which was the most essential for Ti, Fe, and Cu and the smallest for Mn. The factor of differences in soil pollution was essential for Zn and Mo, much less for As, Sr, and Mn, limited for Fe, and was not seen for Ti and Cu. The factor of the interrelation effects of the zone and experiment reflected the different regime of uptake for the plant tissues was seen for two elements: more prominent for Cu and smaller for Ti. While analyzing the dynamic of foliar concentrations of the metal(loid)s during 3 years, two groups were defined. Firstly, Fe, Ni, Mn, and Sr showed stable curves with limited distribution of the plant life cycle. Secondly, As, Zn, Cu, and Mo showed different fluctuations in the curves, which can be attributed to essential influence of those elements to the plant life cycle. Further research will be focused on the application of M. × giganteus to the polluted soil in a bigger scale and comparison results of laboratory and field experiments.

Phytoremediation, as a cost-effective, highly efficient, environmentally friendly, and green approach, gained attention to the removal of metals, including heavy metals, from contaminated soils. The toxic nature of heavy metals can have an adverse effect on human health and the ecosystem, and their removal remains a worldwide problem. Therefore, in this study, a field experiment was carried out to evaluate the potential of Miscanthus  ×  giganteus for the removal of ten microelements and heavy metals (Al, Zn, Fe, Pb, Cd, Co, Cr, Cu, Mn, Ni) from contaminated soil in the territory of a Municipal Waste Rendering Plant. Moreover, the effect of the incorporation of soil improver obtained upon composting biodegradable waste as well as the addition of highly contaminated post-industrial soil on the efficiency of phytoremediation and plant growth was described. The soil improver (SK-8) was applied to the soil at a rate of 200 Mg ha −1 and 400 Mg‧ha −1 . Meanwhile, in the last object, 100 Mg‧ha −1 of highly contaminated post-industrial soil was added. Herein, the research was aimed at assessing the possibility of phytoextraction of heavy metals from soils with different physicochemical properties. The results showed that plants cultivated in soil with 400 Mg‧ha −1 of soil improver exhibited the highest yield (approximately 85% mass increase compared to the soil without additives). Furthermore, the application of a single dose of SK-8 (200 Mg ha −1 ) increased the uptake of Al, Fe, Co, Pb, Mn, Ni, and Cd by Miscanthus  ×  giganteus compared to the soil without additives. Additionally, the performed biotests demonstrated no or low toxicity of the investigated soils affecting the test organisms. However, in all experiments, the phytorecovery of the elements did not exceed 1% of the amount introduced to the soil, which may result from a short cultivation period and large doses of SK-8 or highly contaminated post-industrial soil.

Use of plant growth-promoting bacteria (PGPB) for cultivation of the biofuel crop Miscanthus × giganteus (Mxg) in post-military and post-mining sites is a promising approach for the bioremediation of soils contaminated by metals. In the present study, PGPB were isolated from contaminated soil and screened for tolerance against abiotic stresses caused by salinity, pH, temperature, and lead (Pb). Selected strains were further assessed and screened for plant growth-promoting attributes. The isolate showing the most potential, Bacillus altitudinis KP-14, was tested for enhancement of Mxg growth in contaminated soil under greenhouse conditions. It was found to be highly tolerant to diverse abiotic stresses, exhibiting tolerance to salinity (0–15%), pH (4–8), temperature (4–50 °C), and Pb (up to 1200 ppm). The association of B. altitudinis KP-14 with Mxg resulted in a significant (p ≤ 0.001) impact on biomass enhancement: the total shoot and dry root weights were significantly enhanced by 77.7% and 55.5%, respectively. The significant enhancement of Mxg biomass parameters by application of B. altitudinis KP-14 strongly supports the use of this strain as a biofertilizer for the improvement of plant growth in metal-contaminated soils.

The use of indigenous AMF species from heavy metal contaminated areas can be a promising tool to support the phytostabilisation of such areas. The aim of the study was to evaluate the AMF species diversity in the roots of the perennial energy grasses Miscanthus  ×  giganteus and Spartina pectinata grown in areas with different levels of heavy metal contamination with regard to the potential use of the dominant AMF species to support phytostabilisation of soils contaminated with Pb, Cd and Zn. Samples were taken from two sites with different levels of Pb, Cd and Zn contamination and from an uncontaminated site as a control. The AMF colonisation of the roots of Miscanthus  ×  giganteus and Spartina pectinata was investigated. The composition of AMF species in the plant roots was determined by sequencing the D2 region of the LSU rDNA of Glomeromycota . Soil contamination had a significant effect on the composition of AMF communities in the roots. Diversispora and Claroideoglomus were the predominant genera in the communities in the heavily heavy metal contaminated area. The AMF communities at moderately contaminated and uncontaminated areas showed a similar structure, with Rhizoglomus as the dominant genus. Species such as Palaeospora spainiae , Rhizoglomus silesianum , Septoglomus sp., Septoglomus nigrum , Ambispora sp., Claroideoglomus etunicatum and Diversispora sp3. were identified exclusively in the roots of Miscanthus  ×  giganteus and Spartina pectinata grown in contaminated areas. They could potentially be used to support phytostabilisation of areas contaminated with Pb, Cd and Zn, but further studies are needed.