Agriculture Reference
In-Depth Information
Table 13.3
Methane effl ux from deep (30 cm)-fl ooded
lowland rice plots planted to cv. Gayatri, as infl uenced by
fertilizer management (Rath et al.
1999
)
•
Reduced tillage
•
Direct seeding
•
Chemical fertilizer amendment
Methane effl ux
a
(mg m
−2
h
−1
)
Days after transplanting (DAT)
30
•
Electron acceptors
Treatment
50
70
85
100
13.1.5.1 Fertilizer, Manure, and Straw
Management
Fertilizer and manure management in rice fi elds
are important methane mitigation technologies.
The fertilizer management mitigation option
includes changes in fertilizer types, fertilizer
nutrient ratios, the rates and timing of applica-
tions, and the use of nitrifi cation inhibitors to
reduce methane emissions by affecting methano-
genesis in rice fi elds.
Nitrifi cation inhibitors are known to inhibit
methane oxidation (Bronson and Mosier
1994
).
Lindau et al. (
1993
) reported that some nitrifi ca-
tion inhibitors can mitigate methane emissions
from rice fi elds as well. They are, therefore, dual-
purpose technologies for both N
2
O and CH
4
mitigation.
(i)
Feasibility of technology and operational
necessities
: The use of the nitrifi cation inhibi-
tors such as Nimin or placement of urea
super-granule in fl ooded rice fi elds can be
considered as suitable options for mitigation
of methane emissions from rice fi elds without
affecting grain yields where fl ood waters are
deep (30 cm) but not shallow (5 cm)
(Tables
13.3
and
13.4
). These measures not
only improve N use effi ciency in lowland rice
cultivation but also reduce methane emissions
from deep-fl ooded rice fi elds.
Methane emissions were lowest in plots treated
with a mixture of prilled urea and Nimin, a nitrifi -
cation inhibitor which inhibits the autotrophic
oxidation of NH
4
+
to NO
2
. Lindau et al. (
1993
)
reported that these nitrifi cation inhibitors can
signifi cantly mitigate methane emissions from
rice fi elds. In a micro plot study with dry-seeded-
fl ooded rice paddies, the application of nitrifi ca-
tion inhibitors, in particular nitrapyrin and
wax-coated calcium carbide, retarded methane
emissions considerably. The decrease in methane
emissions in plots treated with wax-coated cal-
cium carbide was attributed to a direct result of
the slow release of acetylene, a known inhibitor of
Control
8.3a
21.0a
39.9a
90.7a
70.6a
Prilled urea
5.7a
13.1a
26.8a
67.2ab
62.8a
Prilled
urea + Nimin
5.2a
17.7a
27.1a
48.0c
50.0b
Urea
super- granule
6.1a
13.2a
30.7a
58.4c
52.6b
a
Observations. In a column means followed by a common
letter are not signifi cantly different at the 5 % level by
DMRT
Table 13.4
Plant biomass production and the cumulative
methane effl ux from shallow (5 cm)-irrigated and rainfed
deep (30 cm)-fl ooded lowland rice fi elds planted with cv.
Gayatri (Rath et al.
1999
)
Plant biomass
production (t ha
−1
)
Cumulative
methane emission
(g m
−2
)
Grain
yield
Deep (30 cm)-fl ooded fi eld plots
Control
Straw
yield
Treatment
8.38
5.04
347.5
Prilled urea
8.48
5.52
307.5
Prilled
urea + Nimin
10.07
5.48
255.0
Urea
super-granule
10.97
6.22
295.0
Shallow (5 cm) fi eld plots
Control
5.87
4.10
38.8
Prilled urea
7.37
4.90
73.8
Prilled
urea + Nimin
8.51
5.60
70.0
Urea
super-granule
8.19
5.80
116.3
methanogenesis (Bronson and Mosier
1991
).
Lindau et al. (
1993
) also reported that nitrifi cation
inhibitors such as encapsulated calcium carbide
and dicyandiamide - containing compounds
[(NH
4
)
2
SO
4
and Na
2
SO
4
] - had mitigating effects
on CH
4
emissions from fl ooded rice cultivation.
The effectiveness of treatments for inhibiting
CH
4
production in descending order are as follows:
sodium azide > dicyandiamide (DCD) > pyri-
dine > aminopurine > ammonium thiosulfate > thio-
urea. The inhibition of CH
4
production in
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