Miscanthus x Giganteus or "Elephant Grass" is a the sterile hybrid between M. sinensis and M. sacchariflorus. It has risen to prominence since the early 1980's as a potential biofuel on account of its high dry weight annual yield that can reach 25t/ha (10t/acre).
Miscanthus x Giganteus is traditionally planted in the spring in the form of a rhizome, this is because unlike traditional crops miscanthus doesn’t produce a viable seed head which can be harvested annually. Planting is ideally carried out between the months of March and April just as soil temperatures begin to start rising.
Planting is carried out with specialised machinery capable of delivering rhizomes at a calibrated rate to a constant depth. To ensure the best possible start for the crop it is essential that the rhizomes are planted into a fine seedbed to a depth of 10 centimetres.
Crop emergence can take anything up to 3 months after planting and this is mainly a result of two variable factors which are moisture availability and the size of the initial rhizome planted. Larger rhizomes have a greater energy content and will surface a lot quicker.
As miscanthus is planted in metre wide rows there is quite a lot of bare ground which opens the path for weed competition in the early stages. As a result of this the crop will require at least two herbicide sprays a year for the first two to three years, by this time the crop will have filled in between the rows and because of the vigorous growth of the miscanthus it will out compete any weed. Another important fact which aids weed control is the amount of mulch which builds up from the crop as a result of it losing its leaves over the winter months, this also creates a haven for insects and wildlife to live and feed in.
In its first year the miscanthus will grow to a height of 1.2 - 2 metres. The crop then senesces over the winter months and is topped down to ground level in the spring. At the end of April the crop will re-shoot and keep growing until the end of September, achieving an average height of 3 metres. This following spring you may look to get your first harvest as the crop will have produced twice as much cane as it did in the first year. Crop yield will keep increasing year on year as the underground rhizome is establishing itself until it levels off in year 4 onwards. Average yields for an established UK crop can be anything between 10 and 20 t/ha.
Harvesting which takes place over March / April is carried out using conventional maize harvesting equipment. Depending on the requirement of the end market and the distance it has to be transported the crop can either be chipped in the field or baled.
There are several end uses for miscanthus which include horse bedding, garden mulch and most importantly of all as a biofuel where it is burned alongside coal or alone in small scale CHP units. As the emmissions of CO2 released during buring are equal to those absorbed by the plant from the atmosphere during its growth, the process "carbon neutral" - although this ignores the fossil fuel energy requirements for growing the crop.
We gratefully acknowledge the support of Bical Energy in the production of this article.
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