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
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