Giant reed, also known as spanish reed, provence reed or indian
grass, is a perennial vigorously rhizomatous plant that can reach
heights of up to 10m in sub-tropical regions and is a member of
the grass family. It is most commonly found growing wild along
riverbanks
and wetter areas throughout Southern Europe but is also found in
dryer field margins, road sides and on infertile land. It is naturalised
to parts of China and the southern states of the USA where it is
often regarded as an invasive plant. Despite its origins, giant
reed has genotypes that can tolerate cooler climates such as exist
in
the UK. The plant produces long and strong, lodging resistant,
hollow stems that may become branched if not harvested annually,
and regularly
alternate long narrow pointed leaves along the length of each stem.
It has been identified as potentially the ‘champion’ of
biomass crops in Europe because of its aggressive growing potential,
high yields, low inputs and pest and disease resistance. So far,
very little effort has been spent on trials of this crop in the
UK. The Cardiff University, Objective 1 ERDF funded, ACRE project
has
3 demonstration/trial sites situated in West Wales and is also
monitoring a site in upland Mid Wales.
Agronomy
Giant reed can be grown on almost any soil type, from well drained
light loams to heavy compact soils. It is deep rooting and has
the ability to utilise deep sub soil water table reserves. Frost
damage may occur if water freezes in cut hollow stems close to
the rhizome. The crop produces a dominant canopy that is able
to very quickly suppress all other vegetation. In nature the
plant does not produce seed but spreads through the growth and
displacement of its rhizomes and as such is relatively easy to
control. For agricultural purposes the crop can be propagated
either by the planting of rhizomes or stem cuttings. Soil is prepared simply by ploughing and harrowing, no herbicide
is required to establish the crop. Fertiliser additions must be
made to deficient soils but are not generally needed during establishment
especially when planting rhizomes. Rhizomes are planted at depth
of 10-15cm in early spring. Each rhizome should contain at least
one bud. These rhizomes are large (length, 10-18cm; diameter, 1-10cm)
and contain reserves capable of producing rigorous growth in the
establishment phase. However, planting stock and machinery able
to plant such large rhizomes on a commercial scale are not yet
available in the UK, but planting machinery would be analogous
to a potato planter. Therefore propagation, at the present, by
rhizome may be expensive, time consuming and labour intensive.
Planting density is suggested at 30,000 rhizomes/ha, at 0.5 x 0.7m
spacing. Under Mediterranean conditions each rhizome can produce
up to 10 stems whilst in cooler climates unfertilised and fertilised
plots produce 1 and 3-5 stems/rhizome, respectively.
Once a root stock is established, growers will then have the opportunity
to expand the area of crop by stem propagation. Stems harvested
green are either prepared as cuttings, containing a node with sections
of adjacent internodes and planted vertically to a depth of 4-8cm,
or whole stems can be laid down horizontally into the soil and
buried in furrows to a depth of 6-8cm. Stem propagation is performed
later in the season when soil temperatures are warm enough to stimulate
the formation of shoots from the node buds. Initial results show
that with this type of propagation, plants develop slowly as they
need to expend energy developing a rhizome in order to survive
the winter, therefore herbicides may be necessary to maximise survival.
However, a similar stand density to rhizome planting results within
a few growing seasons.
Under high (700 mm/yr) and low (300 mm/yr) irrigation regimes
in southern Europe Dalianis et al. (1995) has reported yields of
32.6 and 29.6 t/ha/yr dry matter. The same study identified that
high rates of nitrogen addition have no significant effect on yields
in comparison to low in the initial growing period. Also, high
biomass losses (30%) were reported due to wind blow of leaves and
plant tops when the harvest was delayed until winter, making an
autumn harvest preferable. Moisture content of autumn harvests
is between 36-49% in Mediterranean climates where field drying
is used after cutting. Plants in milder climates can remain green
throughout the winter months and then branch in the spring, so
for dense re-growth from the rhizome it is recommended that stems
are cut in the autumn to allow new buds time to develop ready for
spring growth. The high yielding potential of giant reed needs
still to be confirmed but it must be remembered that all work so
far has been done on unimproved stock and no genetic or selection
work has been done to develop genotypes that maximise yields under
different climates.
The alternative uses for giant reed are diverse. It has been used
effectively as a windbreak, protecting more valuable crops from
damage, for thatching and, is ideal for paper production as it
is pithless. It has been used to produce fishing rods, woodwind
instrument “reeds” and pipe organ pipes! It can also
be used in biofiltration systems to removed organic pollutants
from waste water such as septic tank run-off.
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Dalianis, C., Sooter, C. & Christou, M. (1995) Growth, biomass
and productivity of Arundo donax amd Miscanthus sinensis ‘giganteus’.
In: Chartier et al. (eds) Biomass for energy, environment, agriculture
and industry. Proceedings of the 8th EU Biomass Conference, Pergamon
Press, UK, vol. 1, pp. 575-582.
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