Site-specific feasibility of alternate wetting and drying as a greenhouse gas mitigation option in irrigated rice fields in Southeast Asia: a synthesis

Figures & data

Figure 1. Locations of the four experimental sites.

Table 1. Location, soil properties, season, weather, and field management of the four experimental sites.

Site name	Hue	Jakenan	Prachin Buri	Muñoz
Location
Country	Vietnam	Indonesia	Thailand	Philippines
Province	Thua Thien	Central Java	Prachin Buri	Nueva Ecija
City	Hue	Jakenan, Pati	Bansang	Muñoz
Latitude (°N)	16.43	6.78	14.01	15.67
Longitude (°E)	107.51	111.20	101.22	120.89
Soil properties^a
Texture	Loam	Loam	Heavy clay	Clay
Clay (%)	17.8	22.5	62.9	46.2
Sand (%)	49.3	48.6	10.4	21.7
Silt (%)	32.9	28.8	26.7	32.1
pH (H2O)	4.36 ± 0.02	5.04 ± 0.21	3.53 ± 0.03	5.89 ± 0.11
pH (H2O2)	2.94 ± 0.05	3.33 ± 0.21	2.10 ± 0.06	4.43 ± 0.02
Bulk density (g cm^−3)	1.01	1.54	1.43	1.21
Active Fe (g kg^−^1)	12.3 ± 0.0	3.6 ± 0.0	15.6 ± 0.1	12.6 ± 0.3
Active Mn (g kg^−^1)	0.03 ± 0.01	0.05 ± 0.00	0.07 ± 0.00	0.68 ± 0.01
Total C (g kg^−^1)^b	19.2 ± 1.1	5.3 ± 0.3	22.2 ± 1.2	14.6 ± 1.1
Total N (g kg^−^1)^b	1.88 ± 0.10	0.47 ± 0.02	1.80 ± 0.10	1.20 ± 0.10
C:N mole ratio^b	11.9 ± 0.2	13.3 ± 1.0	14.6 ± 0.4	14.0 ± 0.8
Season/weather
Crop calendar	Dry: January–March Wet: April–August WF: September–December	Wet: Nov–March Dry: March–July DF: July–November	Dry: January–April Wet: June–September WF: September–December	Dry: January–April DF: April–June Wet: June–September WF: September–December
Rainfall (mm)	Dry: 251 Wet: 283 WF: 1642	Wet: 966 Dry: 336 DF: 158	Dry: 99 Wet: 948 WF: 408	Dry: 25 DF: 253 Wet: 835 WF: 470
Air temperature (°C, min.-max.)	Dry: 11.3–37.3 Wet: 22.8–38.7 WF: 19.2–37.7	Wet: 24.0–39.0 Dry: 23.7–39.5 DF: 22.9–39.8	Dry: 24.0–35.5 Wet: 25.5–33.8 WF: 24.5–33.7	Dry: 21.8–31.1 DF: 24.5–35.9 Wet: 23.3–30.3 WF: 23.1–31.9
Field management
Variety	HT1	Cisadane	RD41	NSIC Rc238
Growth duration (day)	96–120	107–132	88–98	81–98
Crop establishment	Wet direct seeding	Wet: Direct seeding Dry: Transplanting	Pre-germinated seed broadcasting	Transplanting
Inorganic fertilizer
N (kg N ha^−^1)	92–120	120	70	90–120
P (kg P2O5 ha^−^1)	72	60	37.5	40
K (kg K2O ha^−^1)	62–78	90	37.5	40
Organic amendment	Microbial organic fertilizer	Farmyard manure	None	None
Residue management	Rice straw removal	Rice straw removal	Rice straw removal	Rice straw removal

^aRange of standard deviation.

^bThe average value of yearly samplings from all treatments during the experiment (see Fig. 4 for sampling time).

WF: Wet fallow; DF: Dry fallow.

Figure 2. Comparison of the soil profiles in the four experimental sites. The soil profiles are arranged according to the apparent soil redox condition with showing the USDA and FAO classifications.

Figure 3. Relationships between (A) predicted SF_CH4-AWD and observed SF_CH4-AWD and (B) observed SF_CH4-AWD and NNFD for the data in Hue and Jakenan (n = 24; 2 sites × 6 seasons × 2 practices (AWD and AWDS)). In A panel, dotted line indicates the linear regression between predicted and observed SF_CH4-AWD. In B panel, solid and dotted lines indicate the multiple regression line with MinWL of −15 cm and the linear regression between observed SF and NNFD, respectively.

Figure 4. Interannual variations in total carbon content at a soil depth of 0–20 cm among three water management practices in (A) Hue, (B) Jakenan, (C) Muñoz, and (D) Prachin Buri. Vertical bars indicate the standard deviation (n = 3–4).

Table 2. Comparison of alternate wetting and drying (AWD) implementation among the four experimental sites^a.

Criteria	Water management	Hue	Jakenan	Prachin Buri DS	Muñoz DS	Muñoz WS
Minimum water level (cm)	AWD	−18.3 ± 6.2 (−25.4 to −7.7)	−23.1 ± 13.5 (−46.3 to −11.3)	−12.5 ± 5.6 (−15.4 to −4.0)	−13.9 ± 1.0 (−15.0 to −13.1)	−9.5 ± 4.2 (−12.5 to −6.5)
	AWDS	−13.0 ± 4.9 (−20.1 to −6.3)	−32.1 ± 18.0 (−63.8 to −19.2)	−13.0 ± 4.5 (−15.4 to −6.3)	−13.3 ± 6.3 (−19.1 to −6.6)	−8.6 ± 0.6 (−9.0 to −8.1)
Number of non-flooded days	AWD	30.2 ± 5.8 (22 to 39)	30.7 ± 7.9 (20 to 41)	24.3 ± 3.8 (20 to 27)	34.0 ± 10.5 (24 to 45)	10.5 ± 9.2 (4 to 17)
	AWDS	29.3 ± 8.5 (14 to 36)	27.2 ± 11.9 (14 to 44)	13.3 ± 4.7 (8 to 17)	31.7 ± 19.0 (12 to 50)	6.0 ± 2.8 (4 to 8)
Ratio of non-flooded days to total days^b	AWD	0.31 ± 0.08 (0.16 to 0.41)	0.28 ± 0.08 (0.16 to 0.39)	0.26 ± 0.03 (0.23 to 0.29)	0.39 ± 0.19 (0.21 to 0.60)	0.13 ± 0.11 (0.05 to 0.21)
	AWDS	0.30 ± 0.09 (0.16 to 0.41)	0.24 ± 0.11 (0.11 to 0.37)	0.14 ± 0.03 (0.09 to 0.17)	0.38 ± 0.27 (0.13 to 0.67)	0.07 ± 0.04 (0.05 to 0.10)
Average water level (cm)	AWD	−0.1 ± 2.2 (−3.0 to 3.6)	0.8 ± 0.6 (−0.1 to 1.7)	−0.5 ± 2.7 (−1.2 to 0.4)	−1.4 ± 1.1 (−2.7 to −0.9)	1.9 ± 0.7 (1.4 to 2.4)
	AWDS	−0.1 ± 1.9 (−3.4 to 2.4)	0.1 ± 1.3 (−1.5 to 1.7)	3.3 ± 1.0 (2.2 to 4.3)	−2.0 ± 4.8 (−7.4 to 1.9)	2.9 ± 1.1 (2.1 to 3.8)
Drainability^c (mm hr^−^1)		0.94 ± 0.28	1.85 ± 0.80	0.78 ± 0.29	0.67 ± 0.24	0.67 ± 0.24

^aMean value ± standard deviation across seasons with the minimum to maximum range in parentheses.

^bTotal days from seeding to final drainage.

^cObserved rate of decline of the surface water level, including evapotranspiration.

Table 3. Comparisons of the effects of AWD on greenhouse gas emissions, rice productivity, and water use among the four experimental sites.

	CH4 (kg CH4 ha^−1)		N2O (kg N2O ha^−1)		N2O contribution to GWP (%)		GWP (kg CO2 ha^−1)		Grain yield (Mg ha^−1)		Yield-scaled GWP (Mg CO2 Mg^−1 grain)		Water use (m^3 ha^−1)		Water productivity (kg grain m^−3)
Site	DS	WS	DS	WS	DS	WS	DS	WS	DS	WS	DS	WS	DS	WS	DS	WS
Value under continuous flooding (CF)
Hue	499.5	644.2	0.28	0.70	0.6	1.0	17,030	23,540	4.41	4.44	3.49	4.89	8127	8394	0.56	0.54
Jakenan	385.3	515.4	0.81	1.13	2.2	2.3	13,342	17,861	5.12	6.87	2.67	2.61	6635	12,521	0.83	0.57
Prachin Buri	13.4	23.0	0.97	0.22	39.3	5.6	746	1190	4.64	4.28	0.15	0.23	7119	11,332	0.71	0.45
Muñoz	69.9	328.9	1.60	0.51	20.6	1.4	2853	11,333	6.90	5.41	0.43	2.10	10,336	10,944	0.77	0.51
Change under AWD relative to CF (%)
Hue	−25.8	−23.8	−26.3	−26.3	−21.8	12.7	−30.8	−24.8	10.3	4.5	−33.6	−21.8	−14.4	−14.9	30.1	25.6
Jakenan	−36.7	−36.8	−13.5	12.1	26.4	85.9	−36.3	−35.9	−0.82	−1.4	−36.8	−35.4	−6.4	−5.7	4.6	3.3
Prachin Buri	−31.2	–	19.3	–	11.8	–	−11.5	–	−12.6	–	−3.2	–	−29.8	–	17.6	–
Muñoz	−32.1	14.1	91.3	4.7	95.8	25.1	−11.4	14.0	−0.13	1.9	−9.3	9.1	−47.1	−17.0	69.0	22.2
P-value
Site (S)	***		***		–		***		***		***		***		***
Dry or Wet (DW)	**		0.209		–		**		0.484		**		***		**
Water management (WM)	***		0.269		–		**		0.638		0.326		***		***
S × DW	***		***		–		***		***		***		***		***
WM × S	0.129		0.711		–		*		0.594		†		***		*
WM × DW	0.829		0.959		–		0.778		0.295		0.829		0.238		0.931
WM × DW × S	0.901		0.894		–		0.914		0.140		0.955		*		*

– data not available.

***, **, *, and † indicate significant difference at p = 0.001, 0.01, 0.05, and 0.1, respectively.

Figure 5. CH₄ emission-related parameters in the four experimental sites. (A) Emission factors (EF) for CF and AWD. (B) AWD scaling factors (SF). Data in dry season are shown for Prachin Buri. Data in dry and wet seasons are shown separately for Muñoz. Mean data in dry and wet seasons are shown for Hue and Jakenan. Means overall sites and seasons with and without Muñoz wet season are separately shown. The horizontal bars for each site indicate the 95% confidence intervals. Bars for IPCC (2006) indicate the error range given in the IPCC (2006) guidelines. In A panel, the values for Prachin Buri CF and AWD are 0.024 ± 0.027 and 0.031 ± 0.041, respectively.

Figure 6. The ratio of seasonal N₂O-N emissions to the total amount of chemical fertilizer N applied. Data for dry season and wet season are shown separately for Muñoz. Mean data in dry and wet seasons are shown for Hue, Jakenan, and Prachin Buri. Means overall sites and seasons with and without Muñoz wet season are separately shown. The horizontal bars indicate the 95% confidence intervals.

IPCC 2006: 2006 IPCC Guidelines for National Greenhouse Gas Inventories Volume 4: agriculture, Forestry and Other Land Use. Eds. Eggleston S, Buendia L, Miwa K, Ngara T, Tanabe K. Institute for Global Environmental Studies (IGES), Hayama, Japan.

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