Effect of oxidizing and reducing agents in soil on methane production in Southeast Asian paddies

Figures & data

Table 1. Soil sampling locations, and chemical properties.

Location	Country	Soil type	pH	Total C(g kg^−1 d.s)	Total N(g kg^−1 d.s)	Hexose (mg kg^−1 d.s)	Total Fe(g kg^−1 d.s)	Free Fe(g kg^−1 d.s)	Latitude and longitude
Kamphaeng Saen	Thailand	Typic Haplustalfs	5.83	8.3	0.72	718	12.64	10.47	N 14°01.640ʹ E 99°58.229ʹ
Ban Go Ta	Thailand	Tropaquepts	4.36	6.9	0.52	847	4.12	1.93	N 16°28.267ʹ E 102°52.016ʹ
Ban Na Ngam	Thailand	Paleaquults	3.91	7.8	0.64	520	6.33	2.92	N 16°32.796ʹ E 102°51.265ʹ
Suphamburi	Thailand	Aeric (Plinthic) Endoaqualfs	4.97	26.5	2.25	835	34.59	13.02	N 14°40.102ʹ E 100°05.541ʹ
Kamchanaburi	Thailand	Aeric Endoaqualfs	7.68	9.9	0.95	471	19.45	5.31	N 14°06.274ʹ E 99°42.702ʹ
Binuang	Indonesia	Kanhapludults	3.89	7.2	0.61	872	1.91	1.29	S 03°06.920ʹ E 115°04.414ʹ
Sungai Rungas	Indonesia	Endoaquepts (Sulfic)	4.80	46.7	3.20	1074	18.45	15.24	S 03°20.881ʹ E 114°46.110ʹ
Jakenan	Indonesia	Aeric Endoaquepts	3.45	4.4	0.47	256	6.89	2.43	S 06°46.751ʹ E 111°11.912ʹ
Cihideung	Indonesia	Hapludults	3.58	12.7	1.33	673	41.52	24.25	S 06°34.247ʹ E 106°43.495ʹ
Atang	Indonesia	Dystrudepts	4.59	15.2	1.39	360	66.77	26.59	S 06°32.099ʹ E 106°44.076ʹ
Maligaya	Philippines	Ustic Epiaquerts	4.43	17.3	1.46	800	39.64	14.10	N 15°40.076ʹ E 120°53.796ʹ
Los Banos	Philippines	Typic Dystrudepts	6.30	17.2	1.49	375	52.88	12.88	N 14°09.909ʹ E 121°15.778ʹ
Tarlac	Philippines	Typic Psammaquents	4.89	11.3	0.96	965	23.07	4.37	N 15°35.796ʹ E 120°42.835ʹ
Ligao	Philippines	Typic Eutrudepts	5.49	28.8	3.00	1094	20.40	4.05	N 13°25.189ʹ E 123°55.459ʹ
Cagsawa	Philippines	Typic Haplustox	6.02	14.0	1.46	722	17.98	2.79	N 13°09.979ʹ E 123°42.028ʹ
Mt. Mayon	Philippines	Typic Haplustox	4.58	11.7	1.21	328	16.28	2.79	N 13°10.866ʹ E 123°42.724ʹ
Hiep Hoa	Vietnam	Acrisoils	4.40	5.7	0.50	359	2.11	1.34	N 21°20.945ʹ E 106°01.961ʹ
VAAS campus	Vietnam	Fluvisol	5.13	6.4	1.21	1808	33.21	3.33	N 21°00.063ʹ E 105°45.898ʹ
Hai Dunog	Vietnam	Dystric Fluvisol	4.87	8.6	0.87	535	20.62	14.09	N 20°58.354ʹ E 106°19.672ʹ
HUA campus	Vietnam	Eutric Fluvisol	5.58	5.2	0.91	719	34.22	6.90	N 21°00.062ʹ E 105°55.844ʹ
Tay Ninh	Vietnam	Acrisol	5.19	2.9	0.30	333	1.81	0.76	N 11°08.094ʹ E 106°19.160ʹ
Can Tho	Vietnam	Fluvic Tropaquept	5.10	28.5	2.65	792	18.75	3.36	N 10°02.636ʹ E 105°44.364ʹ
Soc Trang	Vietnam	Hapli Arenosol	7.54	0.11	0.04	215	21.54	9.57	N 09°20.200ʹ E 106°05.180ʹ
Average			5.07	13.18	1.22	681	22.40	7.99

Bold and Italic values indicate as max and minimum for each properties, respectively.

Figure 1. Methane, mineralizable nitrogen and ferrous production in Southeast Asian paddy soils. Different letters show significant (P < 0.05) differences in methane production.

Table 2. Correlation between the production of CH₄ and CO₂ and the soil’s chemical properties.

	CH4	CO2	Hexose	Total Fe	Free Fe	Ferrous	Mineralizable-N
CH4	–	0.275	0.506*	−0.424*	−0.418	−0.052	0.390
CO2		–	0.522*	0.061	−0.100	0.049	0.878**
Hexose			–	0.093	0.024	0.049	0.492
Total Fe				–	0.783**	0.663**	0.348
Free Fe					–	0.615**	0.173
Ferrous						–	0.524*
Mineralizable-N							-

*P < 0.05; **P < 0.01.

Figure 2. Relation between methane production and total iron contents in Southeast Asian paddy soils. (●) Thailand; (▲) Indonesia; (■) Philippines; and (♦) Vietnam.

Figure 3. Relation between Min-N/Fe (X) and CH–C/CO₂–C (Y). The linear regression line was calculated with all soils.