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AIR1-CT92-0294
Miscanthus Productivity Network |
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Proposal No: | AIR1-CT92-0294 |
| Date Prepared: | September 1999 | |
| Source: | Final report 1997 |
Summary
Introduction Miscanthus x giganteus is a woody rhizomatous C4 grass species which originated in Southeast Asia and was initially imported to Europe as an ornamental plant. It is a perennial plant with an estimated productive life time of at least 10-15 years, and both the stems and leaves of the crop can be harvested annually. Miscanthus is characterised by relatively high yields, low moisture content at harvest and a low susceptibility to pests and diseases. In addition, due to the fact that it utilises the C4 type of photosynthesis, it shows a high irradiation conversion efficiency than C3 plants and it also more efficient in its use of nitrogen and water. It is a promising non-food crop, yielding high quality ligno-cellulosic material for both energy and fibre production.
Objectives The specific objectives of the network were as follows:
Activities These were carried out by 14 partners located in 10 countries throughout Europe. Standard productivity trials of the genotype M. x giganteus have been established and monitored by all partners of the Network and four existing trials (established in 1990) were also maintained. Other activities include investigation of low temperature effects, genotype screening, water stress analysis and environmental impact assessment Experiments on harvesting, drying, storage pre-treatment methods for Miscanthus were being undertaken to identify optimum procedures and minimum costs. Industrial analysis by the partners investigated the use of Miscanthus as a raw material for the production of energy and paper pulp.
Results The genotype that was examined in the field by the partners was Miscanthus x giganteus, this is a naturally occurring interspecific hybrid which like all Miscanthus species, is an unimproved plant but which exhibits considerable yield potential under European conditions. The yields of Miscanthus were found to vary considerably according to site and climate with highest yields being in Southern European sites when water was not a limiting factor. Network members have reported that the trials need to be continued in order to determine the mature yield (> 3 years) of fully established Miscanthus as there is no evidence that any of them had reached their mature yield potential by 1996.
Yields of over 24 ton/ha DM were recorded in Portugal (Lisboa), Greece (CRES) and Italy (Catania) in year 3 (all with irrigation) in comparison with Irish and British third year yields of between 11 and 16 ton/ha DM and 3rd year yields of 18.3 t/ha in North Germany. The yields in Ireland and Britain compare very favourably with the annual dry matter production from short rotation coppice which is grown as an energy crop in these countries. It was found that the growth of Miscanthus in Northern Europe is influenced by low temperatures despite the fact that Miscanthus is better adapted to temperate climates than most other C4 crops.
Experiments investigating the thermal response of leaf extension of a number of genotypes have shown that the response of absolute leaf extension rate to temperature varies widely between genotypes. This may provide a basis for selecting Miscanthus genotypes which could be more productive under temperature limiting conditions. Problems of plant survival due to low temperatures over winter in the first year of crop growth have been encountered at three main sites in Ireland, the Netherlands and Germany, winter failure was also noted in some treatments in a site in Comwall (UK).It was considered that susceptibility of the plant material to damage from low temperatures in the first year may be the result of a number of factors including high soil water content, low temperatures, pre-condiuoning prior to a.frost event, the maturity of the plant, state of dormancy and size and state of buds. However, the validation of these factors as those which play a key role in winter mortality of Miscanthus can only be achieved through further research and development.
It was observed generally that first year winter failure rate was higher in micro- propagated plants than rhizome propagated plants. Genotypic variation in winter survival has been noted and this indicates the possibility of improving winter survival through plant breeding and selection. A method for rapid screening of rhizome cold tolerance has been developed. Further studies are required to apply this protocol to genotypes other than M. x giganteus and thereby investigate the variation in sensitivity to cold between genotypes.
Miscanthus has a high water use efficiency (272 l/kg DM) relative to C3 species due to the fact that it uses the C4 type of photosynthesis. However, due to its high productivity, the water requirements of Miscanthus are still high. It was found that in all trials, highest yields were on the plots with the highest irrigation treatment, with irrigation being identified as a limiting factor in achieving maximum yields, depending on the soil type, site and growth stage. It was found that plant water status affects stomatal conductance and hence leaf transpiration and net photosynthesis, and that as the soil water deficit (i.e. water stress) increases photosynthetic rates decrease. Further research is required in order to identify the optimum, most cost-effective irrigation rates.
Responses to fertiliser applications vary according to soil type and nutrient supply capacity. It was found that soil nitrogen supply may only have a significant effect on yields after the first 2-3 years of growth. This may simply reflect crop nutrient as yields increase. Results also show that rhizomes act as storage organs for nutrients which enables a rapid growth in spring by a resource relocation processes. The nutrient store is built up during the vegetation period and filled in the beginning of autumn (September/October). During the following spring, from March onwards, the store will be depleted as the nutrients of the rhizomes support the production of new above ground biomass.
A root:shoot ratio of about 1:1 was measured. It was also demonstrated that nutrient offtake in dry matter at harvesting was relatively low with approximately 0.5% offtake of nitrogen and potassium and less than 0.05% offtake of phosphorous and magnesium.
Herbicides are required to control weeds during the establishment phase because the slow initial growth of Miscanthus makes it uncompetitive against annual and perennial weeds. Once the crop has established, weed growth is effectively suppressed, initially by the litter layer on the soil surface and subsequently by the closure of the crop canopy that reduces the light penetrating into the understorcy. Weeds that do survive are frequently etiolated and offer little competition to the crop, Spraying of herbicides around the edges of the plantation to remove invading weeds may be all that will be required in the established crop.
There have been no reports of diseases that significantly reduce production of Miscanthus, however, if the area of Miscanthus grown increases, a greater risk of disease may arise. At present, Fusariuin has been observed in Ireland and Barley Yellow Dwarf leutovirus (BYDV) in the United Kingdom.
A mechanistic Windows-based model for the prediction of Miscanthus growth and yield has been developed, known as WIMOVAC (Windows Intuitive Model of Vegetation response to Atmosphere and Climate Change), it has been designed to run on IBM PC-compatible computers running on Microsoft Windows.
Taxonomic studies used two approaches; these were:
The results indicate that while morphological characters may be of some use in distinguishing species, they are of little or no use below the species level. Random Amplified Polymorphic DNA (RAPDs) used with primer OPA - 16 from the Operon kit A however were able to successfully distinguish all of the species and genotypes that were surveyed. The screening experiments demonstrate the variability which exists between Miscanthus genotypes. This indicates a potential for genetic improvement of the crop particularly for characters such as yield and cold tolerance. The genotype screening experiments also showed that yields vary according to location giving rise to the suggestion that in the future genotype selection may need to site specific.
Moisture content at harvest ranged from 25-40% in Southern European countries to 30-60% in more Northern countries; the lower moisture contents in Southern European countries may facilitate Autumn harvesting. Genotypic variation in moisture content at harvest was observed in screening experiments where new cultivars had a moisture content at harvest of 20-30% compared with a moisture content of 44-50% for M. x giganteus.
Several harvesting, drying and storage systems were investigated. Miscanthus can be harvested in the form of chips, bales, bundles or pellets depending on the harvesting machine which is used and the implementation of additional processing of harvested material. Depending on the harvest method used, the material can be stored in the form of chips (different lengths), bales, bundles or pellets. The maximum moisture content for storage of chopped material is 25%. The moisture content should be 18% or lower for storage over a longer period (one year). Big bales can be stored at a moisture content of up to 25% moisture. Bundles can be stored outdoors. Both chipped and compacted material as well as bales can be stored effectively under cover. Open air storage is also possible but some kind of cover may be necessary.
It was found that Miscanthus, with an energy density of 18.2 MJ/kg, is comparable to other combustion materials such as straw when co-combusted with coal to produce energy. It was also concluded that paper produced from Miscanthus is suitable for printing and office uses as well as for wrapping and food packaging.
A study was carried out to determine the feasibility of Miscanthus production throughout Europe by evaluating the gross margins of production, i.e. output of the crop (yield multiplied by crop value) minus the variable costs such as fertilisers, sprays, establishment costs and contract harvesting. The results of the study indicated that production costs varied between organisations and regions. In all cases gross margins were negative. It was found that northern European Miscanthus production costs could be covered by a selling price of 33 ECU/odt without grant aid and assuming a mature yield of 20 odt/ha (sustainable yield in Northern Europe) and a planting cost of 0.05 ECU per rhizome piece. Southern European Miscanthus production costs could be covered by a price of 23 ECU/odt without grant aid and assuming a mature yield of 30 odt/ha (Southern Europe sustainable yield) and a planting cost of 0.05 ECU per rhizome piece.
It was found that establishment costs and crop yield are the key determinants of the economic viability of Miscanthus. However, it has been shown by the partners that there is considerable potential for reducing establishment costs and increasing crop yields. The plants used in the field were grown specifically for the Network and so had very high production costs, these costs would be expected to drop if production was more widespread. In addition, the genotype screening experiments showed that seeded plants yield well. This presents tremendous opportunities for cheaper plant production methods in the future. Higher crop yields can be obtained through crop breeding and genotype screening. In summary, the economics of Miscanthus production are not static and as information and experience increase, input costs may be expected to reduce.
© Copyright 2006 Policy Statements
Updated
by CPL Press:
03/07/2007
- biomatnet@biomatnet.org
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