Kai-Uwe Schwarz

Progress in upscaling Miscanthus biomass production for the European bio-economy with seed-based hybrids

Field trials in Europe with Miscanthus over the past 25 years have demonstrated that interspecies hybrids such as M. × giganteus (M × g) combine both high yield potentials and low inputs in a wide range of soils and climates. Miscanthus hybrids are expected to play a major role in the provision of perennial lignocellulosic biomass across much of Europe as part of a lower carbon economy. However, even with favourable policies in some European countries, uptake has been slow. M × g, as a sterile clone, can only be propagated vegetatively, which leads to high establishment costs and low multiplication rates. Consequently, a decade ago, a strategic decision to develop rapidly multiplied seeded hybrids was taken. To make progress on this goal, we have (1) harnessed the genetic diversity in Miscanthus by crossing and progeny testing thousands of parental combinations to select several candidate seed‐based hybrids adapted to European environments, (2) established field scale seed production methods with annual multiplication factors >1500×, (3) developed the agronomy for establishing large stands from seed sown plug plants to reduce establishment times by a year compared to M × g, (4) trialled a range of harvest techniques to improve compositional quality and logistics on a large scale, (5) performed spatial analyses of yield potential and land availability to identify regional opportunities across Europe and doubled the area within the bio‐climatic envelope, (6) considered on‐farm economic, practical and environmental benefits that can be attractive to growers. The technical barriers to adoption have now been overcome sufficiently such that Miscanthus is ready to use as a low‐carbon feedstock in the European bio‐economy.

Productivity of poplar short rotation coppice in an alley-cropping agroforestry system

In temperate regions, short rotation woody crops cultivated as tree strips in alley-cropping agroforestry systems (ACS) can provide economic benefits by producing an additional commodity, and environmental benefits, e.g., soil erosion control, protection against evaporation and increased biodiversity. Moreover, compared to agrisivilcutural systems incorporating noble trees, ACS with short rotation coppice (SRC)-strips provide periodically high energy outputs and could help to answer environment and energetic political objectives in Germany. However, limited data are available in such systems concerning biomass production of different strip designs. An ACS incorporating poplar SRC has been established near Braunschweig in Lower Saxony (Germany) in 2008. Two harvest cycles (a coppiced 3-year rotation cycle and a un-coppiced 6-year rotation cycle) and two strip designs (“SRC”: 6 poplar rows; “Combined”: 4 poplar rows and 1 aspen row in the centre) were compared. Diameters at breast height, tree heights, shoot numbers and mortality rates were measured to describe growth and estimate yield of outer and middle poplar rows within a tree strip. Concerning the 3-year rotation cycle, higher numbers of shoots per tree as well as higher biomass yields compared to the control field were measured in outer rows, both leeward and windward. With the 6-year rotation cycle, all leeward rows and the middle rows of the combined design showed larger diameters and higher biomass yields. Middle rows of the SRC design, in both rotation cycles, revealed a quicker height growth than outer rows, but a reduced biomass production. Both rotation cycles showed similar yearly biomass production. The results can contribute to improve the design of poplar SRC-strips in ACS in order to optimize biomass production. We recommend reducing the number of rows within SRC-strips, while increasing their total length. Further research is however needed to determine effects of increased biomass in outer tree rows on adjacent crop fields, which influences the whole system productivity.

Environmental Influences on the Growing Season Duration and Ripening of Diverse Miscanthus Germplasm Grown in Six Countries

The development of models to predict yield potential and quality of a Miscanthus crop must consider climatic limitations and the duration of growing season. As a biomass crop, yield and quality are impacted by the timing of plant developmental transitions such as flowering and senescence. Growth models are available for the commercially grown clone Miscanthus x giganteus (Mxg), but breeding programs have been working to expand the germplasm available, including development of interspecies hybrids. The aim of this study was to assess the performance of diverse germplasm beyond the range of environments considered suitable for a Miscanthus crop to be grown. To achieve this, six field sites were planted as part of the EU OPTIMISC project in 2012 in a longitudinal gradient from West to East: Wales—Aberystwyth, Netherlands—Wageningen, Stuttgart—Germany, Ukraine—Potash, Turkey—Adana, and Russia—Moscow. Each field trial contained three replicated plots of the same 15 Miscanthus germplasm types. Through the 2014 growing season, phenotypic traits were measured to determine the timing of developmental stages key to ripening; the tradeoff between growth (yield) and quality (biomass ash and moisture content). The hottest site (Adana) showed an accelerated growing season, with emergence, flowering and senescence occurring before the other sites. However, the highest yields were produced at Potash, where emergence was delayed by frost and the growing season was shortest. Flowering triggers varied with species and only in Mxg was strongly linked to accumulated thermal time. Our results show that a prolonged growing season is not essential to achieve high yields if climatic conditions are favorable and in regions where the growing season is bordered by frost, delaying harvest can improve quality of the harvested biomass.

Genetic Diversity of Salt Tolerance in Miscanthus

Miscanthus is a woody rhizomatous C4 grass that can be used as a CO2 neutral biofuel resource. It has potential to grow in marginal areas such as saline soils, avoiding competition for arable lands with food crops. This study explored genetic diversity for salt tolerance in Miscanthus and discovered mechanisms and traits that can be used to improve the yield under salt stress. Seventy genotypes of Miscanthus (including 57 M. sinensis, 5 M. sacchariflorus, and 8 hybrids) were evaluated for salt tolerance under saline (150 mM NaCl) and normal growing conditions using a hydroponic system. Analyses of shoot growth traits and ion concentrations revealed the existence of large variation for salt tolerance in the genotypes. We identified genotypes with potential for high biomass production both under control and saline conditions that may be utilized for growth under marginal, saline conditions. Several relatively salt tolerant genotypes had clearly lower Na+ concentrations and showed relatively high K+/Na+ ratios in the shoots under salt stress, indicating that a Na+ exclusion mechanism was utilized to prevent Na+ accumulation in the leaves. Other genotypes showed limited reduction in leaf expansion and growth rate under saline conditions, which may be indicative of osmotic stress tolerance. The genotypes demonstrating potentially different salt tolerance mechanisms can serve as starting material for breeding programs aimed at improving salinity tolerance of Miscanthus.