Climate Change Mitigation - Climate Resilient Agriculture for Ensuring Food Security - page 297

Table 13.8 Economics of wet-seeded rice in Sri Lanka
(Weerakoon et al. 2011 )

under irrigated conditions, direct seeding was
profi table, whereas under rainfed conditions,
gross returns were about half than under irriga-
tion, and the direct seeded cropping system was
not profi table.
According to Wassmann and Pathak ( 2007 ),
costs of emissions saving through direct seeding
was found to be more than US$35 per t CO 2 e
saved.

Total input\
costs (US$/
ha)

Gross
returns
(US$/ha)

Profi t
(US$/ha) Region

Dry zone irrigated 523 865 342

Intermediate zone
irrigated

551 731 181

Wet zone rainfed 538 426 −112

13.1.5.8 Chemical Fertilizer
Amendment
Emissions of GHGs are affected by the
amounts and types of fertilizers applied, so
judicious choice of fertilizer application rates
and fertilizer types can reduce emissions. The
source, mode, and rate of application of min-
eral fertilizers influence CH 4 production and
emission from flooded rice paddies. CH 4 emis-
sions from rice fields were decreased by 18 %
due to chemical fertilizer amendments
(Minami 1995 ).
Increases in rice production in South Asia
have been attributed to increased nitrogen use.
Increased nitrogen use may also have an addi-
tional benefi t of lowering methane emissions.
Incorporating urea into soil has been shown to
reduce methane emissions. However, surface-
applied urea resulted in 20 % more emissions
compared to an unfertilized fi eld. The use of
sulfate-based fertilizer has also been linked to
methane emission reductions. Metra-Corton
et al. ( 2000 ) reported that ammonium sulfate
reduced methane emissions by 25-36 % in rice
fi elds. Applying phosphogypsum (calcium sulfate
dihydride) in combination with urea reduced
methane emissions by more than 70 %.
Application of sulfate-containing fertilizers
reduced methane emissions from fl ooded rice
fi elds (Adhya et al. 1998 ). In contrast, incorpora-
tion of organic sources, for instance, green
manure and rice straw, in soils stimulates meth-
ane emission (Denier van der Gon and Neue
1995 ).
Foliar application of nitrogenous fertilizer is
another potential mitigation practice for reducing
CH 4 emissions from rice soils (Kimura et al.
1992 ). Adhya et al. ( 1998 ) demonstrated a large

Korea, where the common cultural practice is to
transplant 30-day-old seedlings, signifi cant
reductions in methane emissions could be
achieved by direct seeding on wet soil (8 %) and
on dry soil (33 %) with no signifi cant effect on
yields in either case. Similarly, Metra-Corton
et al. ( 2000 ) showed that direct seeding resulted
in a 16-54 % reduction in methane emissions
compared to that of transplanted rice seedlings.
For six different cases, Wassmann et al. ( 2000 )
reported a 16-92 % reductions in methane emis-
sions with direct seeding compared to trans-
plants, for six rice cultivars; however, yield
reductions of 4-36 % was also observed.
Subsequently, Huang et al. ( 2012 ) found no sig-
nifi cant effect on yield over six growing seasons,
when a treatment of no-tillage + herbicide + broad-
cast of pre-germinated seeds on fl ooded fi eld
was compared to conventional tillage + later
fl ooding + transplants, but at the end of the fi fth
year, increased in organic carbon in the top 5 cm
of soil was approximately matched by reductions
in carbon at deeper depths.
(i) Advantages
• Direct planting is faster and less labor-
intensive than transplanting.
• It reduces land preparation time.
(ii) Disadvantages
• Yields reduced in some instances (Hossain
et al. 2002 )
• More lodging of rice plants (De Datta
1986 )
Weerakoon et al. ( 2011 ) surveyed Sri Lankan
farmers and presented the cost of cultivation for
direct wet-seeded rice in three scenarios: dry
zone irrigated, intermediate zone irrigated, and
wet zone rainfed (Table 13.8 ). They found that