Effect of intermittent drainage in reduction of methane emission from paddy soils in Hokkaido, northern Japan

Figures & data

Figure 1. Arrangement of the experimental paddy fields in a three-year experiment from 2016 to 2018.

Table 1. Specific dates of agricultural practices in the experimental fields from 2016 to 2018.

Year	Sowing of rice seeds	Basal fertilizer application	First flood irrigation, puddling^†	Transplanting of rice seedlings	First drainage in summer^†	Intermittent drainage^†,‡	Flowering	Final drainage^†	Rice harvest	Rice straw incorporation with plowing
2016	04/13	05/11	05/12	05/20	06/27 - 07/01	07/22 - 08/28	ca. 08/01	08/28	09/27	10/28
2017	04/12	05/10	05/15	05/19	06/29 - 07/03	07/21 - 08/28	ca. 07/28	08/28	09/21	10/16
2018	04/11	05/15	05/15 - 05/16	05/22	06/22 - 07/04	07/19 - 08/27	ca. 07/31	08/27	09/19	-

†In the plots with continuous flood irrigation, the soil was continuously flooded from the first flood irrigation to the final drainage.

‡Sequence of generally three-day flood irrigation and four-day drainage.

Figure 2. Seasonal change in air temperature, precipitation, CH₄ and N₂O fluxes, soil reduction/oxidation potential (Eh) at depth of 10 cm, and soil bivalent iron (Fe²⁺) content in experimental paddy fields during the rice cultivation period in 2016.

Figure 3. Seasonal change in air temperature, precipitation, CH₄ and N₂O fluxes, soil reduction/oxidation potential (Eh) at depth of 10 cm, and soil bivalent iron (Fe²⁺) content in experimental paddy fields during the rice cultivation period in 2017.

Figure 4. Seasonal change in air temperature, precipitation, CH₄ and N₂O fluxes, soil reduction/oxidation potential (Eh) at depth of 10 cm, and soil bivalent iron (Fe²⁺) content in experimental paddy fields during the rice cultivation period in 2018.

Table 2. Cumulative CH₄ and N₂O emissions in the experimental paddy fields from 2016 to 2018.

CH4
	2016	2017	2018
		kg CH4 ha^−1
LiC soil
CF	31±6	186±106	176±93
ID	3±1(91)	121±19(35)	60±32(66)
HC soil
CF	11±4	84±6	165±23
ID	1±2(87)	66±19(21)	46±12(72)
N2O
	2016	2017	2018
		kg N ha^−1
LiC soil
CF	0.00±0.02	−0.21±0.04	−0.32±0.11
ID	0.01±0.06	−0.10±0.19	−0.25±0.10
HC soil
CF	−0.07±0.08	−0.11±0.11	−0.33±0.05
ID	−0.09±0.05	−0.08±0.02	−0.31±0.04

Values are shown as the mean ± standard deviation of three replicates.

CF and ID represent continuous flood irrigation and intermittent drainage, respectively.

Values in parentheses represent the percentage of reduction in CH₄ emission by intermittent drainage.

The CH₄ emission was significantly lower in the ID plots than in the CF plots (P < 0.05), and lower in 2016 than in 2017 and 2018 (P < 0.05) by the two-way analysis of variance and Tukey’s multiple comparison test with the water management practice (CF and ID) and the year (2016–2018) as the two factors, and soil types (i.e., the LiC and HC soils) were the two replicates (n = 2). The N₂O emission was not significantly different between the CF and ID plots, whereas it was significantly lower in 2018 than in 2016 and 2017 (P < 0.01).

Table 3. Brown rice grain yields in the experimental paddy fields from 2016 to 2018.

	2016	2017	2018
		g m^−2
LiC soil
CF	678±78(80)	446±60(81)	486±73(72)
ID	670±72(85)	513±52(78)	503±47(69)
HC soil
CF	640±82(73)	673±83(77)	574±87(68)
ID	664±35(78)	566±71(78)	612±53(58)

Values converted into those with the water content of 15% are shown.

Values are shown as the mean ± standard deviation of five replicates.

CF and ID represent continuous flood irrigation and intermittent drainage, respectively.

Values in parentheses represent the percentage of well-formed rice grains (seiryu-buai).

The difference in rice grain yield was not significant both between the CF and ID plots and among the years by the two-way analysis of variance with the water management practice (CF and ID) and the year (2016–2018) as the two factors, and soil types (i.e., the LiC and HC soils) were the two replicates (n = 2).