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INFLUENCE OF ON FARM WATER MANGMENT
TO THE METHANE EMISSION
IN THE RED RIVER DELTA AREA - VIETNAM
Nguyen Van Tinh
1
;
Nguyen Quang Trung
2
;
Nguyen Viet Anh
3
Abstract
Rice cultivation plays an important role in the culture and diets of people of
Vietnam and it, also, offers possibilities to mitigate climate change. The on-farm
water management of rice field is one of main factors affecting methane emission
from rice field. The paper presents the experimental results on influence of water
regime in rice field on the methane emission from rice paddy in Ha Tay province
from 2004 to 2006.
Rural paysages in the Red River Delta (North Vietnam)
I. Experimental Method
- Experimental site: the experimental research has been implemented in Hoai Duc
District, Ha Tay Province; it is 13 km far to the west of Hanoi capital. The
experimental measure of methane emission from rice field has been conducted in
two different treatments such as continuous irrigation (point A) and intermittent
drainage irrigation (point B). These two treatments were used in order to assess the
potential for methane reduction on rice paddy and to quantify the potential methane
emission reduction in the irrigated rice field through water management on rice
field. Each treatment is applied in the specific tank with the three dimensions of

O
5
= 1.75
mg P/l, PO
4
3-
= 0.54 mg P/l.
- Climate: humid tropics with the cool winter, annual rainfall of 1700 mm, mean
solar radiation of 123 kcal/cm
2
/year, maximum temperature of 33
0
c in July and
minimum temperature of 14
0
c in January.
- Water regime on rice field: For point A, the water deep on rice field is remained
from 3 to 6 cm during all periods of growing rice. For point B, the water on rice
paddy is dried up within 1 week at some stages of maximum tillering and jellow-
ripened, and the water deep on rice paddy is maintained from 3 to 6 cm during all
other periods.
- Cropping system: two crops consist of spring rice and summer rice with pig
manure of 8000 kg per ha and chemical fertilizer of 220 kg N per ha, 800 kg P per
ha and 190 kg K per ha.
- Air sampling method: chamber technique has been used in this research. This
technique consists of fixing aluminum channel bases at the measurement sites in
advance from 3 to 4 hours. These bases are mounted with a U-shaped channel to
hold water. The perspex box of 32x52x99 cm with its open end rests on the channel.
The water in the channel isolated the air inside the perspex chamber from the
outside atmosphere (figure 1).

Reduction
rate
Point A Point B Point A Point B (%)
23/3/2004 2 4.0 3.0 3.829 4.7616 -24.4
30/3/2004 9 2.1 0.1 4.7907 6.1026 -27.4
6/4/2004 16 2.5 2.3 5.5389 5.8328 -5.3
13/4/2004 23 2.5 1.5 20.1925 19.7963 2
20/4/2004 30 9.1 7.0 29.9133 35.8277 -19.8
27/4/2004 37 0.1 0.0 36.0056 20.8623 42.1
4/5/2004 44 0.1 0.0 28.7927 13.7549 52.2
11/5/2004 51 2.8 0.0 24.5955 14.0732 42.8
18/5/2004 58 5.3 3.7 18.2179 22.2767 -22.3
25/5/2004 65 2.8 0.0 14.7404 21.1464 -43.5
1/6/2004 72 4.1 3.0 11.1096 13.1666 -18.5
8/6/2004 79 0.1 0.0 13.9301 12.4548 10.6
15/6/2004 86 5.8 3.2 8.6008 9.9906 -16.2
22/6/2004 93 0.1 0.0 2.5358 4.8656 -91,9
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Figure 2- Methane flux diagram of point A in comparison
with point B in spring crop 2004
0
5
10
15
20
25
30
35

18/10/2004 67 3.5 0.0 5.03206 7.58994 -50.8
25/10/2004 74 1.5 0.0 4.05896 7.05759 -73.9
1/11/2004 81 2.7 0.0 6.48329 5.97636 7.8
8/11/2004 88 2.0 0.0 7.39542 3.79716 48.7
15/11/2004 95 1.5 0.0 1.67898 2.05848 -22.6
Figure 3- Methane flux diagram of point A in comparison
with point B in summer crop 2004
0
10
20
30
40
50
60
0 20 40 60 80 100
Days after transplanting
C H 4 ( m g / m 2 / h o u r )
CH4 (point A)
CH4 (point B)
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Table 3- The methane flux in summer crop 2005 at point A and point B
Date
Days after
transplanting
Field
deep
water
(cm)

0 20 40 60 80 100
Days after transplanting
CH4 (mg/ m2/hour)
CH4 (point A)
CH4 (point B)
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Table 4- The methane flux in spring crop 2006 at point A and point B
Date Days after
transplanting
Field
deep
water
(cm)
Methane flux
(mg/m
2
/hour)
Reduction
rate
Point A Point B Point A Point B (%)
7/3/2006 1 4.00 4.00 3.467 3.448 0.5%
14/3/2006 8 3.60 3.90 4.341 4.264 1.8%
26/3/2006 20 3.90 2.80 6.837 6.046 11.6%
28/3/2006 22 3.70 2.30 19.831 16.743 15.6%
4/4/2006 29 2.40 0.0 29.621 29.716 -0.3%
11/4/2006 36 3.40 0.0 39.030 32.171 17.6%
18/4/2006 43 2.40 0.0 30.623 24.757 19.2%
25/4/2006 50 4.00 0.0 25.314 15.713 37.9%

Treatments Spring crop
2004
Summer crop
2004
Summer crop
2005
Spring crop
2006
Point A 369.1 457.2 451.00 382.80
Point B 340.3 401.5 383.82 344.17
Reduction rate (%) 7.8 12.2 14.9 10.09
The above experimental research results showed that methane emission rates were
affected by water regime in rice paddy. The methane flux in most periods of
intermittent drainage irrigation case is lower than continuous irrigation treatment.
However, the methane emission reduction is mainly in stages of the biggest
emission on rice field (periods of tillering and before flowering). The seasonal
integrated methane emission flux in point A is 369.1 to 457.2 kg CH
4
/ha while in
point B the seasonal integrated methane emission flux is 340.3 to 401.5 kg CH
4
/ha.
The average methane emission reduction rate is 7.8 to 14.9 %.
Conclusion
The methane development and emission on rice field depend very much on water
regime in rice paddy. For the Red River delta area of Vietnam, the use of
intermittent drainage irrigation technique is very useful in practice to reduce
methane emission on rice field and to contribute to the global environment
protection. Besides, in some author research results concerned it, also, is very
helpful in applying the intermittent drainage irrigation technique in rice paddy to