Evaluating the effects of alternate wetting and drying (AWD) on methane and nitrous oxide emissions from a paddy field in Thailand

Figures & data

Table 1. Physical and chemical properties of acid sulfate paddy soil at Prachin Buri Rice Research Center, not determined.

	Depth (cm)
Properties of soil	0–20	20–50	50–65	65–90	90–110	110–150
Texture	Clay	Clay	Clay	Clay	Clay	Clay
Sand (%)	16	20	22	20	20	20
Silt (%)	22	22	22	20	20	20
Clay (%)	62	58	56	60	60	60
Bulk density (Mg m^−^3)	1.2	1.4	1.3	1.2	1.0	–
pH (H2O)	4.8	4.7	4.7	4.5	4.5	4.4
Organic matter (g kg^−1)	30	8	5	3	3	4
Available P (mg kg^−1)	11	3	2	1	1	1
Available K (mg kg^−1)	115	66	71	99	110	119
CEC (cmol kg^−1)	37	31	27	28	29	30

Table 2. Key crop cultivation practices and dates in the dry seasons(DS) and wet seasons (WS).

Practice	DS1	WS1	DS2	DS3	WS3
Cropping period	27 December 2013–4 April 2014	19 June–15 September 2014	1 January–9 April 2015	17 February–25 May 2016	30 June–26 September 2016
Crop duration (days)	97	88	99	97	89
Herbicide application
Butachlor + Propanil 70%	6 January (10 DAS	2 June 2014	11 January 2015 (10 DAS)	27 February 2016 (10DAS)	10 June 2016 (10 DAS)
Thiacloprid at 10 mL ha^−1	14 January 2014 (18 DAS)	18 July 2014 (29 DAS)	20 January 2015 (19DAS)	–	–
Azoxystrobin + Difenoconazole at 250 mL ha^−1	14 March 2014 (77 DAS)	–	14 March 2014 (77 DAS)	–	–
Fertilizer application
DAP at 20 kg N ha^−1	16 January 2014 (20 DAS)	10 July 2014 (21 DAS	25 January 2015 (24 DAS)	14 March 2016 (26 DAS)	21 July 2016 (21 DAS)
P2O5 at 37.5 kg ha^−1	17 January 2014 (20 DAS)	11 July 2014 (21 DAS)	25 January 2015 (24 DAS)	14 March 2016 (26 DAS)	21 July 2016 (21 DAS)
K2O at 37.5 kg ha^−1	18 January 2014 (20 DAS)	12 July 2014 (21 DAS)	25 January 2015 (24 DAS)	14 March 2016 (26 DAS)	21 July 2016 (21 DAS)
First urea at 25 kg N ha^−1  Second urea at 25 kg N ha^−1	22 February 2014 (57 DAS)	31 July 2014 (42 DAS) 20 August 2014 (62 DAS)	14 February 2015 (44 DAS) 3 March 2015 (61 DAS)	3 April 2016 (46 DAS) 19 April 2016 (62 DAS)	4 August 2016 (35 DAS) 25 August 2016 (56 DAS)

(WS)DAS: days after sowing; DAP: di-ammonium phosphate; not practiced

Figure 1. Seasonal variations in daily rainfall (a, b, c), daily maximum and minimum air temperature (d, e, f), mean surface water level (g, h, i), CH₄ flux (j, k, l), and N₂O flux (m, n) for three water management practices in dry season (DS1, DS2, and DS3). Error bars for CH₄ and N₂O fluxes indicate the standard error (n = 3). Vertical dotted lines indicate the application timing of nitrogen fertilizer. Gray areas in a and d indicate the lack of data observation.

Figure 2. Seasonal variations in daily rainfall (a, b), daily maximum and minimum air temperature (c, d), mean surface water level (e, f), CH₄ flux (g, h), and N₂O flux (i) for three water management practices wet seasons (WS1 and WS3). Error bars for CH₄ and N₂O fluxes indicate the standard error (n = 3). Vertical dotted lines indicate the application timing of nitrogen fertilizer. Inserted panels in e and f show the magnified y-axis for the high values.

Table 3. Statistical analysis results of combined seasonal means of CH₄, N₂O, grain yield, and water use, with the effects of both treatment (Trt), growing season (s), and a combination of treatment and season (S × Trt).

Treatment	CH4^a (kg ha^−1)	N2O (kg ha^−1)	GWP^a (kgCO2e ha^−1)	Grain yield (t ha^−1)	Yield-scaled GWP (kgCO2e ton^−1)	Water use^a (m^3 ha^−1)	Water productivity^a (ton m^−3)
CF	17.3 A	0.785	857 B	4.50	0.17	8805 a	0.609 b
AWD	8.8 B	0.979	637 B	4.19	0.14	5108 c	1.086 a
AWDS	21.0 A	0.851	1097 A	4.44	0.22	5811 b	1.023 a
Source of variation	p value
Trt	*	0.554	†	0.398	0.140	***	**
S	***	*	***	***	***	***	***
S × Trt	0.502	*	0.129	*	0.221	***	**

^aMeans with different letters indicate significant difference at the 5% level for lower-case letter and at the 10% level for capital one. The asterisks †, *, **, and *** indicate the p value of <0.10, <0.05, <0.01, and <0.001, respectively.