Browsing by Subject "Emergence"

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Introducing new miscanthus hybrids into the European bioeconomy : the effect of environment and management on biomass quantity and quality
(2023) Magenau, Elena; Lewandowski, Iris
Miscanthus has been identified as a promising lignocellulosic perennial biomass crop for temperate climates and different (marginal) soils in terms of yield and ecological benefits. The cultivation of miscanthus brings numerous ecological advantages, such as a reduction in soil erosion, protection of aquatic ecosystems from alteration through eutrophication, and increasing heterogeneity in annual arable landscapes leading to increased biodiversity compared to annual crops. Reasons for this are its perenniality, the long period of time it stands on the field, and its low fertiliser and plant protection demands. Nevertheless, the area under cultivation in Europe is limited. The reasons are that the scientific yield levels are not reached commercially, and the only commercially cultivated hybrid Miscanthus × giganteus (M×g) is sterile. Miscanthus is therefore currently propagated and established via rhizomes, which limits upscaling. However, the seed-based hybrids tested so far do not reach the potential of M×g in terms of yield, quality, and ecological impact under a wide range of climatic conditions. To improve the integration of miscanthus as a biomass crop in the growing European bioeconomy, it is required to reach high and stable yields over several years (security of biomass supply) and a low ecological impact by low nutrient offtakes under different European climates. Therefore, it is essential to gain agronomic knowledge on how genetic (G), location-specific environment (E), and management (M) factors and the interactions between them affect the security of biomass supply and ecosystem services of novel seed-based hybrids. Against this background, the research objectives of this study are: 1) to investigate the effect of the onset of the growing season on biomass supply security and how it is affected by late spring frosts, 2) to assess G × E interaction effects on miscanthus biomass security, and 3) to assess G × E × M interaction effects on nutrient offtake, yield and quality of miscanthus biomass. For this purpose, new seed- and rhizome-based miscanthus hybrids were compared with the commercially grown M×g and evaluated for biomass yield, quality, and nutrient offtakes (a key parameter defining the ecological impact) under different European conditions to determine biomass supply security and ecological effects. The effect of the management parameters cutting height and harvest time was also analysed. The results show that to reach a high biomass supply security, avoiding damage by late spring frosts is essential. An effective mechanism is a low frost sensitiveness of the emerging shoots and to produce new shoots over the whole growth period, as observed for the seed-based M. sinensis × sinensis (M sin×sin). By contrast, a late emergence and producing fewer, thicker but frost-susceptible shoots at the beginning of the growing season, as observed for rhizome-based M×g and rhizome- and seed-based M. sacchariflorus × sinensis (M sac×sin), endangers the biomass supply security in case of frost after emerging. Over the first three years, the establishment process of miscanthus depended on location and hybrid. The M sin×sin hybrids flowered and senesced earlier than the taller M sac×sin hybrids. Active senescence, probably initiated by flowering, increases biomass quality by reducing the moisture and nutrient content. Following the third growing season, the highest yields were recorded at the low-altitude site in northern Italy and the lowest on a industrially damaged marginal land site in northern France. Moisture contents at spring harvest were lowest in Croatia and highest in Wales, United Kingdom. A lower moisture content is highly desirable for transport, storage and most end-use applications. Overall, lower moisture contents at harvest were found in M sin×sin hybrids than in M sac×sin. As expected, delaying the harvest until spring reduced yield and nutrient contents. At lower latitudes, the late-ripening M sac×sin combined high yields with low nutrient contents when harvested in spring. At the most elevated latitude location (Wales), the early-ripening M sin×sin combined high biomass yields with low nutrient offtakes. The M×g clone with intermediate flowering and senescence showed similarly low nutrient contents at all locations. An increased cutting height at spring harvest decreased yields by 270 kg ha-1 (0.83%) with each 1-cm increase in cutting height up to 40 cm. Although whole shoot mineral concentrations were significantly influenced by both hybrid and year interactions, total nutrient contents did not differ significantly from those in the lower basal sections. In years with wet conditions before harvest, an increase in cutting height of 10 cm decreased moisture content by up to 8%, whereas the effect during dry conditions was marginal. To achieve high biomass supply security and increased ecological benefits in miscanthus cultivation, the results of this study lead to the recommendation to cultivate M sin×sin hybrids at locations with a high risk of late spring frosts, as observed in northern European sites, and M sac×sin hybrids at locations where the risk is low, as observed in southern Europe. In southern Europe, M sac×sin hybrids achieved high yields with low nutrient and moisture contents as they made use of the long vegetation period. In general, M sin×sin has a shorter growth period than M sac×sin hybrids, making it the perfect hybrid for northern Europe, where the vegetation period is short. To ensure biomass supply in regions with extreme minimum winter temperatures and late spring frosts, miscanthus should be harvested in spring due to the thicker mulch layer, which functions as insulation. To ensure biomass supply security, a successful establishment is essential. Therefore, during the establishment phase, harvest should generally take place in spring, as the establishment period is crucial for securing biomass yield throughout the cultivation period. Weakening or even loss of plants during this period will lead to higher weed pressure and lower than optimal yields. The harvest cutting height should be as low as possible to achieve a higher yield without an over-proportional increase in nutrient offtake. However, cutting height needs to be adapted according to local conditions by finding an optimum between biomass loss and the risk of damage to harvest machinery and contamination of the biomass by soil. Should the moisture content of the biomass be too high for safe storage due to wet conditions during harvest, the cutting height can be increased to avoid costly post-harvest drying procedures. This study recommends hybrids for specific locations in Europe, provides important data for determining harvest timing and height, and key data on the ecological impact. It shows that the cultivation of miscanthus in Europe, taking into account the G × E × M interactions, has the potential to secure the biomass supply for the growing bioeconomy while positively influencing the provision of ecosystem services. Furthermore, integrating miscanthus into the agricultural system increases its resilience by diversifying the crops grown, the structure of the agricultural landscape and farmers income.