Rice plants reduce methane emissions in high-emitting paddies.

Area of Science:

• Agricultural Science
• Environmental Science
• Soil Science

Background:

• Paddy fields are a major source of methane (CH4) emissions, with rice cultivation often assumed to enhance these emissions according to IPCC guidelines.
• Rice plants possess dual roles in methane cycling: enhancing emissions via aerenchyma and substrates, and suppressing them through oxygen supply that inhibits methanogenesis and promotes oxidation.
• The net effect of rice on methane emissions depends on the balance between these opposing functions, particularly in high-emitting environments.

Purpose of the Study:

• To investigate and demonstrate the actual impact of rice plants on methane emissions in high-emitting paddy fields.
• To challenge the conventional understanding that rice cultivation solely enhances methane release from paddy soils.

Main Methods:

• A comparative study was conducted in triple-cropping rice paddy fields in the Mekong Delta, Vietnam.
• Methane emissions were measured using the chamber method in areas with and without rice plants.
• Gas samples were analyzed using gas chromatography to quantify methane concentrations.

Main Results:

• Rice plants were found to suppress overall methane emissions in high-emitting paddy fields.
• The degree of methane emission reduction by rice varied with plant growth stages, peaking at maximum tillering and decreasing post-heading.
• In high-emitting paddies, methane production is primarily driven by soil organic matter from previous crops, not rice-derived substrates.

Conclusions:

• Rice cultivation actively suppresses methane emissions during the growing season in high-emitting paddy fields.
• The oxygen-supplying function of rice plays a crucial role in mitigating methane release in these environments.
• Selecting rice varieties with high methane-suppressing capabilities is significant for managing emissions from high-emitting paddies.