Effects of alternate wetting and drying technique on greenhouse gas emissions from irrigated rice paddy in Central Luzon, Philippines

Figures & data

Table 1. Soil properties of the experimental site.

Parameters	Values
Soil texture	Clay
Clay (%)	46.2
Sand (%)	21.7
Silt (%)	32.1
pH (H2O)	7.0
OC (g kg^−1)	14.0
Total N (g kg^−1)	1.4
C/N	11.8
Active Fe (g kg^−1)	12.6
Mn (g kg^−1)	0.7

Figure 1. Seasonal variations in daily rainfall (A–C), daily maximum and minimum air temperature (D–F), mean surface water level (G–I), CH₄ flux (J–L), and N₂O flux (M, N) for three water management practices in dry season (DS) of 2014, 2015, and 2016. Error bars for CH₄ and N₂O fluxes indicate the standard error (n = 4). Vertical dotted lines indicate the application timing of nitrogen fertilizer. Gray areas in A–F indicate the lack of data observation.

Figure 2. Seasonal variations in daily rainfall (A–C), daily maximum and minimum air temperature (D–F), mean surface water level (G–I), CH₄ flux (J–L), and N₂O flux (M, N) for three water management practices in wet season (WS) of 2014, 2015, and 2016. Error bars for CH₄ and N₂O fluxes indicate the standard error (n = 4). Vertical dotted lines indicate the application timing of nitrogen fertilizer. Gray areas in A–F indicate the lack of data observation.

Table 2. Seasonal CH₄ and N₂O emissions, GWP, rice grain yield, yield-scaled GWP, total water use, and water productivity as affected by cropping season and water management.

		CH4 (kg CH4 ha^−1)		N2O (kg N2O ha^−1)		GWP (kg CO2 eq ha^−1)		Grain yield (Mg ha^−1)		Yield-scaled GWP (Mg CO2 ha^−1 Mg^−1 grain)		Water use (m^−3 ha^−1)		Water productivity (kg m^−3)
Treatment		DS	WS	DS	WS	DS	WS	DS	WS	DS	WS	DS	WS	DS	WS
CF		69.9	328.9	1.60	0.509	2853	11,333	6.90	5.41	0.43	2.10	10,336	10,944	0.77	0.512
AWD		42.2	350.1	3.50	0.633	2476	12,093	6.88	5.83	0.37	2.14	5913	9215	1.18	0.645
AWDS		52.8	374.0	2.63	0.528	2578	12,874	6.90	5.42	0.41	2.46	5012	8949	1.43	0.615
Season mean		54.9	351.5	2.58	0.556	2636	12,100	6.89	5.55	0.40	2.23	7087	9702	1.13	0.590
		Treatment means
CF		199.4 A		1.05 B		7093 A		6.16 A		1.27 A		10,640 A		0.642 B
AWD		196.1 B		2.07 A		7284 A		6.35 A		1.25 A		7564 B		0.914 A
AWDS		213.4 A		1.58 B		7725 A		6.16 A		1.43 A		6980 B		1.023 A
		p-Value
Source of variation	df
Cropping season (CS)	5	***		***		***		***		***		***		***
Dry or Wet (DW)^a	1	***		***		***		***		***		***		***
Dry season (DS)^a	2	***		0.502		***		**		***		***		†
Wet season (WS)^a	2	***		0.383		***		†		***		***		0.134
Main plot error	15
Treatment (T)	2	*		*		0.776		0.666		0.496		***		***
T × CS	10	*		0.297		0.610		0.954		0.585		***		**
T × DW^b	2	†		0.422		0.476		0.615		0.457		***		***
T × DS^b	4	*		†		0.562		0.747		0.562		***		*
T × WS^b	4	0.315		0.769		0.462		0.946		0.434		†		0.957
Split-plot error	36

Different characters indicate significant treatment differences. df: degrees of freedom.

^aSubdivision of variation among CSs.

^bSubdivision of variation among T × CS interactions.

†p < 0.10, *p < 0.05, **p < 0.01, ***p < 0.001.