Agriculture Reference
In-Depth Information
Table 4.5
Effect of elevated CO
2
level on yield of
selected crops (Singh et al.
2010
)
detrimental to yield quality of certain crops.
For example, elevated CO
2
is detrimental to
wheat fl our quality through reductions in pro-
tein content (Sinclair et al.
2000
).
Without CO
2
fertilization, many regions, espe-
cially in the low latitudes, suffer a decrease in
productivity by 2050. In contrast, by including
CO
2
fertilization, all but the very driest regions
show increases in productivity. If CO
2
fertiliza-
tion is strong, North America and Europe may
benefi t from climate change at least in the short
term. However, regions such as Africa and India
are nevertheless still projected to experience up
to 5 % losses by 2050, even with strong CO
2
fertilization. These losses increase up to 30 % if
the effects of CO
2
fertilization are omitted. In fact
without CO
2
fertilization, all regions are pro-
jected to experience a loss in productivity owing
to climate change by 2050.
A reduction in CO
2
emissions would be
expected to reduce the positive effect of CO
2
fer-
tilization on crop yields more rapidly than it
would mitigate the negative impacts of climate
change. Even if GHG concentrations rose no fur-
ther, there is a commitment to a certain amount of
further global warming (IPCC
2007
). Stabilization
of CO
2
concentrations would therefore halt any
increase in the impacts of CO
2
fertilization, while
the impacts of climate change could still continue
to grow. Therefore, in the short term, the impacts
on global food production could be negative.
However, estimates suggest that stabilizing CO
2
concentrations at 550 ppm would signifi cantly
reduce production losses by the end of the cen-
tury (Tubiello and Fischer
2006
).
For all species, higher water-use effi ciencies
and greater root densities under elevated CO
2
in
fi eld systems may alleviate drought pressures
(Centritto
2005
). This could offset some of the
expected warming-induced increase in evapora-
tive demand, thus easing the pressure for more
irrigation water. This may also alter the relation-
ship between meteorological drought and agri-
cultural/hydrological drought; an increase in
meteorological drought may result in a smaller
increase in agricultural or hydrological drought
owing to increased water-use effi ciency of plants
(Betts et al.
2007
).
Ambient
CO
2
level
(380 ppm)
Elevated
CO
2
level
(550 ppm)
CO
2
fertilization
effect (%)
Parameters
Green gram
Biological
yield (g m
−2
)
270
295
9
Seed yield
(g m
−2
)
92
102
11
Soybean
Biological
yield (g m
−2
)
463
530
14
Seed yield
(g m
−2
)
190
220
16
Chickpea
Biological
yield (g m
−2
)
694
800
15
Seed yield
(g m
−2
)
213
258
21
Wheat
Biological
yield (g m
−2
)
1,068
1,260
18
Seed yield
(g m
−2
)
442
516
17
4.2.5
Effect on Yield
During 2007-2009, an experiment was con-
ducted at the Indian Agricultural Research
Institute farm, New Delhi, India, on four crops
(green gram, soybean, chickpea, and wheat)
inside the FACE ring (Singh et al.
2010
). It was
found that biomass as well as grain yield
increased in all these crops under the elevated
CO
2
condition (550 ppm) (Table
4.5
). The
enhancement in yield was associated with
increase in the number of pods/plant, number of
seeds/pod, number of spikes/m
2
, number of
grains/spike, etc.
4.3
Elevated Temperatures
The global temperature has increased by 0.74 °C
during the past 100 years. The recent report of
IPCC (
2007
) has reconfi rmed the increasingly
strong evidence of global climate change and has
projected that the average atmospheric tempera-
ture across the world would rise by 1.8-4.0 °C
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