[Methane Production Potential and Methanogenic Pathways in Paddy Soils Under Different Rice-based Cropping Systems]

Area of Science:

• Agricultural Science
• Environmental Science
• Soil Science

Background:

• Methane (CH4) production in paddy soils is influenced by cropping systems and methanogenic pathways.
• Understanding these differences is crucial for mitigating greenhouse gas emissions from agriculture.

Purpose of the Study:

• To investigate the CH4 production potential and methanogenic pathways in paddy soils under different rice-based cropping systems.
• To quantify the contribution of acetate fermentation to CH4 production.

Main Methods:

• Soils from three cropping systems (rice-wheat, rice-fallow, double-rice) were analyzed using anaerobic incubation.
• Methane production potential, dissolved organic carbon (DOC), acetic acid content, and stable carbon isotopes (δ13CH4, δ13CO2) were measured.
• The fluoromethane (CH3F) inhibitor was used to assess acetate-dependent methanogenesis (fac).

Main Results:

• Methane production potential was significantly lower in the rice-fallow system compared to rice-wheat and double-rice systems.
• The rice-fallow system had higher acetate-dependent methanogenesis (fac) rates (84-98%) compared to other systems.
• Soil properties like cation exchange capacity and pH were negatively correlated with CH4 production potential.

Conclusions:

• Cropping systems significantly impact CH4 production potential and pathways in paddy soils.
• The rice-fallow system, despite lower overall CH4 production, relies heavily on acetate fermentation.
• These findings provide insights for managing paddy soil CH4 emissions.