Ratoon Season Rice Reduces Methane Emissions by Limiting Acetic Acid Transport to the Rhizosphere and Inhibiting...

Area of Science:

• Agricultural Science
• Environmental Science
• Microbiology

Background:

• Rice paddies are a significant source of atmospheric methane (CH4).
• Ratoon rice (RR) exhibits lower CH4 emissions compared to main-crop rice (MC), but the underlying mechanisms are unclear.
• Understanding carbon allocation and microbial interactions is crucial for mitigating CH4 emissions in rice cultivation.

Purpose of the Study:

• To investigate the mechanisms behind reduced CH4 emissions in RR compared to MC and late rice (LR).
• To quantify the impact of RR on CH4 flux, grain yield, and economic return.
• To elucidate the role of carbon allocation and rhizosphere microbial communities in CH4 reduction.

Main Methods:

• A 2-year field experiment comparing RR, MC, and LR.
• ¹³C-labelling to trace carbon allocation between rice plants and the rhizosphere.
• Rhizosphere metagenomics to analyze microbial community composition and gene expression.
• Abscisic acid (ABA) pathway analysis.

Main Results:

• RR reduced daily CH4 flux by 91% and increased grain yield by 34%-57% compared to MC and LR.
• RR diverted more photosynthate carbon to grain and less to the rhizosphere, limiting substrate for methanogens.
• Reduced abundance of Methanobacteriaceae and down-regulated methanogenic genes were observed in RR rhizosphere.
• An ABA-mediated interaction involving OsCIPK2 and OsSWEET1A was identified as key to carbon reallocation.

Conclusions:

• RR offers a promising strategy for climate-smart rice farming by simultaneously reducing CH4 emissions and enhancing crop efficiency.
• Targeting carbon allocation patterns and rhizosphere microbial function, modulated by ABA signaling, can lead to significant environmental and economic benefits.
• This study establishes a framework for understanding and optimizing rice cultivation for reduced greenhouse gas emissions and improved productivity.