Agriculture Reference
In-Depth Information
3 Methane Emission from Rice Cultivation
Rice paddy field is an important source of methane. Many field and lab based stud-
ies have been carried out around the world to explore various aspects of methane
production and emission from rice paddy soils. Wassmann et al. (
2000a
) have stud-
ied methane emissions from five different Asian countries (China, India, Indonesia,
Philippines, and Thailand) and reported that climate and soil conditions play impor-
tant roles in regulating methane emission potential from rice fields. They have used
automated closed chamber method for estimating methane emissions from the rice
fields. Their study revealed that low temperature and subtropical climate limited
CH
4
emission in Northern China and northern India whereas tropical stations
( Maligaya, Philippines; Beijing and Hangzhou, China) registered higher emission
rates (300 kg CH
4
/ha
-1
/season
-1
).
CH
4
emission from rice fields is highly sensitive to existing water regime, local
variations in crop management and quality of organic inputs so that in most of the
cases their cumulative impact overpowers the impact of soil and climate (Wassmann
et al.
2000a
). The spatial variations in CH
4
emissions from different rice-growing
areas have also previously been reported (Parashar et al.
1996
; Yagi et al.
1994
).
Wassmann et al. (
2000b
) showed that distinct period within the season can help
to reduce CH
4
emission significantly (20-80 %) in irrigated rice cultivation. Chare-
onsilp et al. (
2000
) reported that methane fluxes from deepwater rice fields is lower
than that of irrigated rice fields but due to longer seasons and continuous flooding
conditions, total emission from deepwater rice fields is quite high, i.e., about 99 kg
CH
4
/ha
-1
/season
-1
. Emission of methane from rain-fed rice fields is much lower than
that of irrigated rice fields (Setyanto et al.
2000
). Garg et al. (
2011
) estimated that
in the year 2008 India's total methane emission was about 20.56 Tg and agriculture
sector contributed 23 % of India's total GHGs emission. The study also showed that
Uttar Pradesh and Andhra Pradesh were the two highest methane producing states
and Mumbai and Anugul (Orissa) districts were the two highest methane producing
districts in India.
4 Nitrous Oxide Emission from Agricultural Soils
Flooded rice fields are not the potent source of N
2
O emissions because of prevail-
ing anaerobic conditions (Granli and Bockman
1994
). Emission of N
2
O starts only
when the fields are drained and aerobic conditions are created. Use of N-fertilizers
increases the rate of N
2
O emissions from rice fields (Kumar et al.
2000
). Sharma
et al. (1995) estimated that N
2
O-N emissions from irrigated and upland paddy fields
in India are about 0.004-0.21 Tg/yr
-1
and 0.002-0.01 Tg/yr
-1
, respectively. How-
ever, the emission of CH
4
can itself act as a check on N
2
O formation in flooded rice
soil (McCarty et al.
1991
). Ghosh et al. (
2003
) reported that in New Delhi, India, to-
tal CH
4
emission under upland conditions is in the range of 24.5-37.2 kg/ha
-1
while
N
2
O fluxes varied in the range of 0.18-100.5 µg m
-2
ha
-1
with CV 69-143 %, and
