Industrial Crops and Products 12 2000 97 – 109
The modelled productivity of Miscanthus × giganteus GREEF et DEU in Ireland
J.C. Clifton-Brown
a,b,
, B. Neilson
b
, I. Lewandowski
a
, M.B. Jones
b
a
Uni6ersita¨t Hohenheim, Institut fu¨r Pflanzenbau und Gru¨nland
340
, Fruwirthstrasse
23
, D-
70599
Stuttgart, Germany
b
Botany Department, Trinity College, Uni6ersity of Dublin, Dublin
2
, Ireland Received 27 July 1999; received in revised form 28 January 2000; accepted 14 February 2000
Abstract
The contribution of Miscanthus biomass to an energy or fibre industry in Ireland can only be estimated if the potential productivity is predicted on a regional basis. In order to parameterise a model to predict dry matter
production, growth and climatic measurements were carried out in 1994 and 1995 on a Miscanthus field trial, planted in 1990 in southern central Ireland. These were used to derive relationships between: i leaf canopy light interception
and thermal time calculated from air temperatures; and ii radiation intercepted and above ground biomass. These relationships were used to parameterise an empirical productivity model in which water and nutrient supplies are
assumed non-limiting. The output from this model was incorporated into a geographical information system GIS to map the predicted potential production of M. × giganteus throughout Ireland, using 10 year daily air temperatures
and incident radiation from 23 climatic stations. Across the island, potential biomass yields at the end of the growing season, ranged between 16 and 26 t DM ha
− 1
. The model approach and its predictions are discussed. © 2000 Elsevier Science B.V. All rights reserved.
Keywords
:
Miscanthus; Geographic information system GIS; Growth model; Energy crops; Ireland www.elsevier.comlocateindcrop
1. Introduction
Herbaceous, rhizomatous crops can provide a renewable, and largely carbon-neutral, energy
source. Miscanthus, a genus of rhizomatous, perennial C
4
grasses with origins in E. Asia, is a strong candidate as a biomass species on account
of several advantageous physiological characteris- tics. Plants using C
4
photosynthesis have the po- tential to out-yield those with the more common
C
3
photosynthesis because when grown under op- timum conditions they have a maximum conver-
Abbre6iations
:
DD
TBX
, degree days accumulated above a base temperature of X°C; e
c
, radiation use efficiency g DM MJ
− 1
PAR intercepted; e
i
, efficiency with which the radiation is intercepted by the crop dimensionless; k, radiation extinc-
tion coefficient dimensionless; LAI, leaf area index dimen- sionless; PAR, photosynthetically active radiation 400 – 700
nm MJ m
− 2
; S
t
, integral of incident solar radiation MJ m
− 2
; t
l
, thermal leaf area coefficient DD
TBX
m
2
leaf m
− 2
ground; W
h
, above ground dry matter t DM ha
− 1
. Corresponding author. Fax: + 353-1-6081147.
E-mail address
:
jcbrowntcd.ie J.C. Clifton-Brown 0926-669000 - see front matter © 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 9 2 6 - 6 6 9 0 0 0 0 0 0 4 2 - X
sion efficiency of light energy in photosynthesis which is 40 higher than C
3
plants Monteith, 1978. For C
4
plants the optimal conditions are most frequently either sub-tropical or tropical
but, interestingly a clone of Miscanthus has been recently shown, even in the temperate climate of
southern UK to achieve efficiencies 37 above those of native C
3
plants Beale and Long, 1995. This is probably due to the fact that Miscanthus
naturally occurs in, and is adapted to, cooler climates than most other species which exhibit C
4
photosynthesis Numata, 1979. Furthermore, it has also been shown that the environmental im-
pact of cultivation of Miscanthus is less than annual crops because a large proportion of fer-
tiliser inputs are effectively recycled from one year into another via the perennial rhizomatous system
Beale and Long, 1997. Finally, Miscanthus has a very good combustion quality due to low Cl, N, S
and ash contents Lewandowski and Kicherer, 1997.
To develop an energy industry which uses biomass as a raw material, high yield potential is
essential and it is also necessary to show how this yield potential varies with climatic conditions.
Crop growth models are now used widely to predict yields based upon prevailing climatic con-
ditions Schapendonk et al., 1998. Many of these are based on principles established by Monteith,
1977. Here the dry matter at final harvest W
h
is the product of the integral of incident solar radiation S
t
, the fraction of radiation which is intercepted by the canopy e
i
and the efficiency with which intercepted radiation is converted into
biomass e
c
, so that W
h
= S
t
· e
i
· e
c
1 Assessment of the yield from a promising clone,
Miscanthus × giganteus Greef and Deuter, 1993, has been attempted in field trials established at 16
sites across Europe in the European Miscanthus Network Project Walsh, 1997. In this paper data
collected in 1994 and 1995 from field trials estab- lished in southern central Ireland in 1990 were
used to parameterise the model described by Eq. 1. By using data from 23 meteorological stations
in Ireland and incorporation of the model results into a geographic information system GIS the
model has been scaled up to produce countrywide values of potential primary production of above
ground dry matter. It was shown that the poten- tial above-ground productivity of M. × giganteus
in Ireland could vary from 16 to 26 t DM ha
− 1
year
− 1
. It is important to note that M. × gigan- teus is just one of several clones of the Miscanthus
genus used in biomass trials and the model devel- oped here, although generic in nature, has been
parameterised specifically for this clone.
2. Materials and methods
