Seasonal variation in methane flux from rice paddies associated with methane concentration in soil water, rice biomass and temperature, and its modelling

Abstract

To attempt to develop physicochemical and physiological modelling for methane transport from the rhizosphere to the atmosphere through rice plants, methane flux, methane concentration in the soil water, and the biomass of rice were measured in lysimeter rice paddies (2.5 × 4 m, depth 2.0 m) once per week throughout the entire growing season in 1992 at Tsukuba, Japan. The addition of exogenous organic matter (rice straw) or soil amendments with the presence or absence of vegetation were also examined for their influence on methane emissions. The total methane emission over the growing season varied from 3.2 g CH4 m -2 y -t without the addition of rice straw to 49.7 g CH4 m -2 y-1 with rice straw and microbiological amendment. In the unvegetated plot with the addition of rice straw, there was much ebullition of gas bubbles, particularly in the summer. The annual methane emission due to the ebullition of gas bubbles from the unvegetated plot with the addition of rice straw was estimated to be almost the same as that from the vegetated site with the addition of rice straw. In the early growth stage, the methane flux can be analyzed by the diffusion model (Flux = Methane concentration × Conductance of rice body) using parameters for methane concentration in the soil water as a difference in concentration between the atmosphere and the rhizosphere, and for the biomass of rice as a conductance of rice body. On the other hand, although the diffusion model was inapplicable to a large extent from the middle to late growth stage, methane flux could be estimated by air temperature and concentration in the soil water. Thus, methane transport from the rhizosphere to the atmosphere through rice plants consisted of two phases: one was an explainable small part by diffusion in rice body; the other was a large part strongly, governed by air temperature. The existence of gas bubbles in the soil may be related to the transition between the two phases

Diurnal Methane Fluxes as Affected by Cultivar from Direct-Seeded, Delayed-Flood Rice Production

“…The soil-texture effect on CH 4 emissions may also be responsible for the lack of a cultivar effect on CH 4 emissions from the clay (NEREC) compared to the silt-loam soil (RREC) in this study (Table 3). In contrast to studies that reported no diurnal variation [6] [14] [15], CH 4 fluxes/estimated emissions differed among measurement times of day for each of the four location-growth stage combinations in the direct-seeded, delayed-flood production system measured in this study. These results were similar to the measured diurnal variations reported previously [2] [4] [6]- [13].…”

“…Previous reports indicate diurnal variations (i.e., the amplitude and timing of flux minima and maxima) in CH 4 emissions may also differ over time within the growing season [8] [10] [12]. However, numerous studies have also reported no significant difference in CH 4 emissions between day and night [6] [14] [15]. Differences between cultivars have generally been consistent given the multitude of factors that have been shown to affect CH 4 fluxes and emissions throughout a growing season, such as soil texture [16] [17] [18] [19], fertilizer nutrient source [20], organic soil amendments [8] [12], residue management/previous crop [21] [22] [23] [24], water management scheme [8] [25] [26], and production system [27].…”

Methane Emissions among Hybrid Rice Cultivars in the MidSouthern United States

“…The seasonal pattern of CH 4 emissions increasing once the flood is applied, peaking near heading, then declining prior to flood release has been observed in numerous previous studies [30,32,49,51,53,59,60,61,62] and suggests that root exudates increase during vegetative growth providing substrate for methanogenesis and decrease again during grain fill as resources are translocated to the filling grains. Research conducted by Denier van der Gon et al [63] indicated that CH 4 emissions are related to allocation of photosynthetically derived C between roots and grains and that decreasing translocation of C to grains (i.e., removing florets prior to grain fill) causes an increase in C translocation to roots and an increase in CH 4 emissions.…”

Competitive interactions between methane- and ammonia-oxidizing bacteria modulate carbon and nitrogen cycling in paddy soil

“…The nitrogenous fertilization of paddy soil in this study is about 250 kg N ha −1 , which is equivalent to 107 µg N g −1 d.w.s., assuming an effective soil depth of 20 cm. In addition, methane concentrations of 900-15 000 ppmv were generally detected in paddy soil during rice-growing season (Nouchi et al, 1990(Nouchi et al, , 1994. Therefore, the microcosms were incubated with 100 µg urea-N g −1 d.w.s.…”