www.vncold.vn Vietnam National Commission On Large Dams 1 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 1mx1mx1m. - Soil characteristics: the soil of rice field is silly clay loam, pH = 6.8, organic substance is 3.73 %, total N is 0.23 %, P 2 O 5 = 0.22 %, K 2 O 5 = 1.34 %. _______________________ 1 Assoc. Prof. Dr. Vice Director, Department of Agriculture and Rural Development of Ninh Thuan Province; 2 Assoc.Prof., Dr. Center for Water Resources and Environment, www.vncold.vn Vietnam National Commission On Large Dams 2 3 ME. Vice Director, Center for Irrigation and Water Supply-Vietnam Institute for Water Resources Research - Characteristics of the irrigation water: the water is supplied from Dan Hoai pumping station located near the bank of the Red River. The chemical properties of water as follows pH = 7.7, total N = 5.4 mg N/l, NH 4 + = 0.19 mg N/l, P 2 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). Figure 1- The chamber set on rice field to measure methane emission www.vncold.vn Vietnam National Commission On Large Dams 3 Air sampling glass bottles (250 mml capacity) have two ways. The collection of samples operates with the taking out of the full water inside the bottles. Water deep and temperature inside the chamber are also measured during each sample collection for calculating the chamber air volume at standard temperature and pressure. Air sampling from the chamber was done at intervals of 0, 15, 30 and 45 minutes started at 9 am of every Monday from transplantation to harvest. - Air sample analyzed method: The air samples are sent to laboratory and analyzed by GC 14B equipped with FID and a column of carbonxen 1000. GC is calibrated before and after each set of measurement using 9.39 ppmv methane standard. II. Research results The results of methane emission at two above treatments are showed in tables 1, 2, 3, 4, 5 and figures 2, 3, 4, 5 below Table 1- The methane flux in spring crop 2004 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 (%) 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 www.vncold.vn Vietnam National Commission On Large Dams 4 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 40 0 20 40 60 80 100 Days after transplanting CH4 (mg/m2/hour) Point A Point B Table 2- The methane flux in summer crop 2004 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 (%) 16/8/2004 4 5.0 2.8 3.0566 4.80938 -57.3 23/8/2004 11 3.5 2.6 12.0455 15.4503 -28.3 30/8/2004 18 6.2 4.1 25.8555 31.5028 -21.8 6/9/2004 25 3.2 2.9 50.2633 54.5608 -8.6 13/9/2004 32 4.8 4.7 53.3186 49.0097 8.1 20/9/2004 39 4.3 3.6 42.5146 11.8831 72.1 27/9/2004 46 3.7 0.0 35.2001 16.8521 52.1 4/10/2004 53 4.0 1.8 20.9416 13.6749 34.7 11/10/2004 60 2.9 3.4 7.17517 8.98779 -25.3 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) www.vncold.vn Vietnam National Commission On Large Dams 5 Table 3- The methane flux in summer crop 2005 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 (%) 3/8/2005 1 3.40 1.20 3.659 3.371 7.86 10/8/2005 8 1.40 1.40 12.812 19.781 -54.40 17/8/2005 15 5.50 4.80 19.779 29.473 -49.01 24/8/2005 22 3.70 3.70 45.503 51.293 -12.72 31/8/2005 29 7.70 5.00 51.018 48.168 5.59 8/9/2005 36 2.10 1.00 47.147 10.040 78.70 15/9/2005 43 5.40 4.60 35.641 19.498 45.29 21/9/2005 50 4.00 0.70 21.778 14.049 35.49 29/9/2005 57 9.50 3.30 10.006 9.229 7.77 5/10/2005 64 2.20 0.40 6.525 7.085 -8.58 12/10/2005 71 5.00 0.0 4.171 3.668 12.07 20/10/2005 78 0.50 0.0 5.675 3.936 30.65 26/10/2005 85 5.80 5.80 4.643 5.401 -16.33 2/11/2005 92 3.80 3.80 3.233 6.363 -96.81 Figure 4- Methane flux diagram of point A in comparison with point B in summer crop 2005 0 10 20 30 40 50 60 0 20 40 60 80 100 Days after transplanting CH4 (mg/ m2/hour) CH4 (point A) CH4 (point B) www.vncold.vn Vietnam National Commission On Large Dams 6 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% 4/5/2006 57 3.80 0.0 22.224 13.707 38.3% 9/5/2006 66 4.30 0.0 17.196 15.898 7.5% 16/5/2006 71 2.50 2.50 13.413 20.739 -54.6% 24/5/2006 78 5.50 5.50 10.227 12.665 -23.8% 30/5/2006 85 4.50 4.50 8.214 7.657 6.8% 6/6/2006 91 3.80 3.80 3.147 4.281 -36.0% 13/6/2006 98 6.40 6.40 2.817 6.143 -118.1% 20/6/2006 105 8.30 0.0 3.548 3.233 8.9% Figure 5- Methane flux diagram of point A in comparison with point B in spring crop 2006 0 5 10 15 20 25 30 35 40 45 0 20 40 60 80 100 120 Days after transplanting CH4 (mg/m2/hour) CH4 (point A) CH4 (point B) www.vncold.vn Vietnam National Commission On Large Dams 7 Table 5 - Methane emission of point A in comparison with point B Unit: kg/ha 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 save irrigation water and to increase rice yield. References 1. Nguyen Mong Cuong, Nguyen Van Tinh and others (2000). Report on measuring the methane emission from irrigated rice field under intermittent drainage technology. 2. Yong-Kwang Shin, Seong-Ho Yon, Moo-eon Park and Byong-Lyol Lee (1996). Mitigation Option for methane emission from rice field in Korea. Royal Swedish Academy of Science. Ambio Vol.25 No 4. 3. ADB (1994). Climate change in Asia: Thematic Overview. Regional study on Global Environment Issue. 4. IRRI. (1999). Terminal report January 1993 – December 1998, GLO/91/631 International Research Program on Methane emission from rice field. . www.vncold.vn Vietnam National Commission On Large Dams 1 INFLUENCE OF ON FARM WATER MANGMENT TO THE METHANE EMISSION IN THE RED RIVER DELTA AREA - VIETNAM Nguyen Van Tinh 1 ; Nguyen Quang. 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. 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