Agriculture Reference
In-Depth Information
In a 20 years' crop duration of
S. viminalis,
with a cutting cycle of
four years, the average harvestable stem production amounts to 0.825 *
11.4 = 9.4 t d.m. because of reductions in the initial and post-
harvest years. In a 10 years' crop duration of
M
.
×
giganteus,
the average
harvestable stem production amounts to 0.84 * 11.6 = 9.8 t d.m.
because of reductions in the initial years.
4.2 Future development of the actual yield (year 2020)
It was assumed that breeding for an improved stem/foliage ratio in
S.
viminalis
and
M.
×
giganteus
will lead to half the theoretically possible
yield increase in 20 years. Therefore, under optimal conditions in 2020,
one may expect a potential stem growth of a full-grown crop of 17.5 + 1.7
= 19.2 t d.m. in
S. viminalis
in 2020, and of 18.9 + 2.1 = 21.0 t d.m.
ha
-1
y
-1
in
M.
×
giganteus.
The additional annual increase in stem growth of
0.2 % by the enhanced content in the atmosphere, leads to a potential
stem growth of a full-grown
S. viminalis
crop of 20.0 t d.m.
in
2020.
It was assumed that both the management factors causing an
annual yield increase in winter wheat of 1.03 %, and the factors causing an
annual yield decrease in silage maize of 0.73 %, apply to biomass crops.
Yields of biomass crops grown by arable farmers may increase by the
application of knowledge that is gained through research programmes;
enlargement of the area with low productive soils and the introduction of
pests and diseases are possible developments that could reduce the yield
increase. The resulting yield increase owing to developments in crop
management would thus amount to 1.03-0.73 = 0.3 % annually, and the
fraction of the potential yield attainable by farmers would increase from
0.725 to 0.77 in 20 years (0.77 is calculated as 0.725
×
[1.003]
20
).
Resulting actual stem growth rates are 0.77 * 20.0 = 15.4 t d.m.
in
S. viminalis,
and 0.77 * 21.0 = 16.1 t d.m. in
M.
×
giganteus.
If it is assumed that in
M.
×
giganteus,
winter losses are reduced to
10 %, the expected yield in spring 2021 is 0.9
×
16.1 = 14.5 t d.m. In
S. viminalis,
the harvested stem fraction is assumed to be constant at 0.9,
and the increment of harvestable stem biomass will amount to 0.9 * 15.4 =
13.9
t d.m.
Increasing the cutting cycle in
S. viminalis
to five years, and the
crop duration to 30 years, increases the average harvestable
stem
production during the crop duration to 0.867 * 13.9 = 12.0 t d.m.
All factors together cause an increase in stem growth from 9.4 t d.m.
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