Abstract:
Methane (CH₄) is the second most impactful anthropogenic greenhouse gas (GHG) andis
significantly emitted from rice paddies, contributing 6–11% of global CH₄ emissions. Accurate
quantification of these emissions is critical for developing effective mitigation strategies.
However, field-level measurements of GHGs are often challenging and costly. In paddy soils,
approximately 90% of methane is emitted through rice plants, requiring large chambers to
enclose the entire plant for accurate CH₄ emission measurements in the field. To address this, a
laboratory experiment was conducted to develop a method for measuring CH₄ emissions from
inundated paddy soil using gas-permeable silicone tubes (inner diameter: 1 mm; outer diameter:
1.5 mm) to simulate plant-mediated CH₄ transport. A closed chamber system with four chambers
(each with a 500 ml headspace) was used to evaluate the feasibility of the using silicone tubes
and to assess the effects of tube density and insertion depth on CH₄ flux. In the first experiment,
five silicone tubes inserted to a depth of 5 cm were tested against a control condition without
silicone tubes The second experiment assessed two insertion depths (5 and10 cm) and tube
densities (5 and10 tubes), equally distributed over 68 cm². CH₄ emissions were measured every
2 minutes for 30 minutes, followed by a 10-minute ventilation period for gas collection and
measuring system including the gas cell of the FTRI spectrometer. Results from the first
experiment showed that CH₄ emissions increase significantly under the silicone tube treatment
compared to the control. In the second experiment, CH₄ emissions were greater at the 10 cm
insertion depth compared to at 5 cm, though the increase was not proportional to the depth, likely
due to enhanced oxidation of CH₄ in the surface oxidized layer near the soil-water interface. These
findings demonstrate that gas-permeable silicone tubes are a promising tool for simulate plant
mediated CH₄ emissions in la
