Agriculture Reference
In-Depth Information
7.3 Water Management
Practice of midseason drainage has been followed in China since 1980s and stud-
ies showed that it resulted in 40 % CH
4
emission reduction i.e., about 5 Tg CH
4
/yr
(Li et al.
2005b
). However, the effectiveness of water management in reducing
CH
4
emissions varied from place to place. Midseason drainage also increased N
2
O
emissions that offset a part of Greenhouse gas radiative forcing benefit (nearly
32 %) obtained through reduction in methane emission. Maximum Greenhouse
gas radiative-forcing benefit can be gained when midseason drainage is applied to
soil with low organic content and high clay content (Li et al.
2005b
). Husin et al.
(
1995
) studied the influence of various irrigation practices (continuous flooding,
intermittent irrigation, and saturated soil conditions) on CH
4
flux from rice fields
in Java and Indonesia and proved that the water management treatments signifi-
cantly influences the average daily methane fluxes. The study showed that CH
4
flux in intermittently irrigated rice fields was 53 % lower than that of continu-
ously flooded fields. Soil Eh status can be maintained easily by altering water
management practices. Midseason drainage can increase Soil Eh to the oxidative
state (to the level + 450 mV from −160 mV) in just a few days that suppressed the
methanogenesis process in the rice soil (Reddy et al.
1989
; Patrick and Jugsujinda
1992
).
Yagi et al. (
1998
) studied the impact of water percolation on CH
4
. The study
suggested that CH
4
emission rate got reduced significantly with an increase in the
percolation rates. Yu et al. (
2004
) reported that under non-flooding (but wet) irriga-
tion system, cumulative global warming potential of rice fields can be reduced up
to about 72 %. Nelson et al. (
2011
) reported that midseason drainage can reduce
methane emission effectively as well as promote methane oxidation process which
together can reduce Greenhouse gas emissions by 75 million t of CO
2
equivalent.
Tyagi et al. (
2010
) studied the impact of four different types of water manage-
ment systems (continuous flooding, tillering stage drainage, midseason drainage
and multiple-drainage) on CH
4
efflux from rice fields. The study showed that mid-
season drainage and multiple-drainage are highly effective in reducing methane
emissions from rice soil. The study also reported that midseason drainage and mul-
tiple-drainage can mitigate GWP of rice soil by 41 and 37 % respectively. Itoh et al.
(
2011
) studied the impact of prolonged midseason drainage on methane flux from
Japanese rice fields and reported that seasonal CH
4
emissions and 100-year GWP
can be reduced to approximately 69.5 and 72 % respectively by alternative water
management without any significant decrease in the grain yield.
7.4 Direct Seeding of Rice
Corton et al. (
2000
) reported 18 % CH
4
emission reduction by utilizing direct seed-
ed rice practice in Philippines. Wassmann et al. (
2004
) showed that DSR practice