Geoscience Reference
In-Depth Information
greenhouse gas because of its longer lifetime (150 years) and
greater GWP. Atmospheric N
2
O absorbs thermal radiation. An
increase of 0.2-0.3% in N
2
O concentration in the atmosphere
contributes about 5% to global warming.
Emissions of GHGs, particularly the non-CO
2
gases such as
methane, nitrous oxide, carbon monoxide and nitrogen oxides,
from the agriculture sector are significant in India. The pri-
mary sources are the large agricultural areas under paddy cul-
tivation and large cattle population in India. The overall budget
of atmospheric CH
4
emission amounts to 500 Tg/year of which
60 Tg/year from paddy fields worldwide. Methane emissions
from the agricultural sector for 1990 in Tg is as follows:
Livestock—0.3 Tg/year (largest contribution is from non-
dairy followed by buffaloes); paddy cultivation—4.07 ± 1.25 Tg /
year; animal manure—0.9 Tg/year; field burning of agricul-
tural residues—0.116 Tg/year.
1. The Indian domestic livestock population increased
from 456 million in 1987 to 467 million in 1992 and is
expected to increase to 625 million in 2020.
2. The paddy cultivation area of 42.32 mha in India is the
largest in Asia. The global emission of methane from
paddy cultivation is 60 Tg.
3. Field burning of agricultural residues also releases
CO = 2531 Gg and N
2
O = 3 Gg, and agricultural soils
also release N
2
O = 0.24 Tg/year (l Tg = 10
12
g or 1 mil-
lion tonnes).
15.7
pests and diseases susceptibility
The impacts of elevated CO
2
should be considered among oth-
ers in the context of
1. Changes in air temperature, particularly nocturnal tem-
perature due to increase in CO
2
and other trace gases and
changes in moisture availability and their effect on veg-
etative versus reproductive growth.
2. Need for more farm resources (e.g. fertilisers).
3. Survival and distribution of pest populations, thus devel-
oping a new equilibrium between crops and pests (Krupa,
2003).
Indirectly, there may be considerable effects on land use
due to snow melt, spatial and temporal rainfall variability,
availability of irrigation, frequency and intensity of inter- and
