Methodological aspects of quantifying GHG
emissions from rice fields
Reiiner Wassmann
Internatiionall Riice Research Instiitute

‘Closed Chamber‘ Method
Fan
Fan
time
concentration
Transparent chamber
Septum
Syringe
or
Vacutainer
tube

Diurnal patterns: algorithms
F = 13.2 F6 + 4.6 F12 + 7.2 F18
16
14
12
10
8
6
4
2
0
Mature rice plants
0 6 12 18 24
Buendia et al. 1997
Daytime
CH4 emission (mg m-2 h-1)
Young rice plants
R2 > 0.98
F = 10.4 F6 + 5 F12 + 7.4 F18

Seasonal patterns: Mid-season drainage
water level (cm) / line Eh (mV) / dots
100
0
-100
-200
water level (cm) / line Eh (mV) / dots
30
20
10
1400
1200
1000
800
600
400
200
Days after planting
30
20
10
0
20 40 60 80 100 120
-300
1400
1200
1000
800
600
400
200
0
methane emission (mg CH4 m-2 d-1)
20 40 60 80 100 120
0
20 40 60 80 100 120
100
0
-100
-200
-300
0
methane emission (mg CH4 m-2 d-1)
20 40 60 80 100 120
Field experiment at Hangzhou, China (Lu et al. 2000)

Field stations of the Intenational Rice Research Institute
(projects funded by US-EPA and UNDP/ GEF)
IrIrrrigigaatetedd
RRaaininfefedd
DDeeeeppwwaateterr
IRRI/
Los Banos

a
b
View of the
field chambers
(for flooded/
non-flooded
condition)

Schematic Presentation of Automated System
I) Field
chambers
II) Pneumatic
unit
III) Sample
transfer
IV) Calibration
gas
V) Injection
loop/ GC
V) Data acqu./
control

Urea (Nueva Ecija)
1200
1000
800
600
400
200
0
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
start of rainy season
(May 15)
end of rainy season
(Nov 15)
1 15 29 43 57 71 85 99 113 127 141 155 169 183 197 211 225 239 253 267 281 295 309 323 337 351 365
SFLUX 1 SFLUX 2
VEG1
REP1
RIP1
VEG
REP
RIP
0.13 SF1
0.30 SF1
0.57 SF1
0.16 SF2
0.37 SF2
0.46 SF2
PRE1
0.003 SF1
PHV1
0.02 SF1
PRE2
0.02 SF2
PHV2
0.06 SF2
DRY
FLX=0
PHV3
0.001SF2
Cropping calendar (Philippines)

700 0
600 0
500 0
400 0
300 0
200 0
100 0
0
INDIA
Major emission classes
7000
6000
5000
4000
3000
2000
1000
0
INDONESIA
700 0
600 0
500 0
400
A
B2
C
D
E
F
G
B1
red: irrigated rice green = rainfed rice blue = deepwater rice

How can we address these questions and overcome the complications?
Model.
+Upscaling
Field
Measurements
Process Studies
Process Studies