Geoscience Reference
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are expected to perform better than crops in tropical areas,
where maize, sorghum, sugarcane and millets are staples and
grown in abundance. Generally, it is assumed that increased
atmospheric CO
2
could enhance growth rates of certain types
of crop plants and that change in temperature and precipita-
tion would affect livestock crops, pest and soils. Plant growth
is generally limited by carbon sink rather than carbon source.
Temperature-sensitive plant developmental processes may con-
strain many agricultural yields. In order to draw an idea about
crop response under enhanced CO
2
concentration, other factors
such as temperature and precipitation must be taken into con-
sideration as their combined effect may be somewhat differ-
ent. The effect of elevated CO
2
on rice cultivars are studied by
Uprety et al. (2000, 2002, 2003). The yields of some crops with
elevated CO
2
concentration are shown in Tables 15.1 through
15.3 (Cline, 1999; Aggarwal, 2000; Uprety et al., 2000).
Increases in CO
2
and other GHGs result in climate changes
such as temperature increase, more erratic pattern of rainfall,
weather change and so on. The uneven monsoon rainfall in
India leads to large-scale droughts and floods, having a major
effect on Indian crop production (Parthasarathy and Pant, 1985;
Parthasarathy et al., 1992; Selvaraju, 2003; Kumar et al., 2004)
and on the economy of the country (Gadgil et al., 1999a; Kumar
and Parikh, 2001). This certainly has an impact on agriculture
and this impact manifests itself in a number of ways, namely,
changes in the length of growing season. Scientists suggest that
a 1°C increase in average temperature would tend to advance the
thermal limit of cereal cropping in the mid-latitude Northern
Hemisphere and would bring more land under cultivation than
table 15.1
Effect of elevated (620 ppmv) CO
2
concentration
on yield and yield attributes in rice (
Oryza sativa
var. Pusa 834)
Critical
difference
at 0.05P
Ambient
(310 ppmv)
Elevated
(620 ppmv)
% Increase
over ambient
Character
Grain yield (g)
28.28
43.22
52.83
8.50
100 grain
weight (g)
18.80
21.90
16.49
0.92
Number of
panicles
12.00
14.00
16.63
0.76
Grain number/
panicle
139.40
230.40
65.28
23.20
Source:
Uprety, D. C. et al., 2000.
Indian J. Plant Physiol
., 5: 105-107.
