Synthetic Microbial Community Promotes Straw Humification and Improves Soil Organic Carbon in Cropland.

Area of Science:

• Agricultural Science
• Microbiology
• Soil Science

Background:

• Straw return boosts soil organic carbon (SOC) and soil multifunctionality (SMF).
• Low humification rates limit straw return benefits in field conditions.
• Synthetic microbial communities (SynComs) show potential for enhancing straw humification.

Purpose of the Study:

• Identify key microbial taxa for maize straw humification.
• Construct a stable two-membered SynCom to promote humification.
• Evaluate SynCom's impact on straw decomposition and SOC in field conditions.

Main Methods:

• Progressive dilution-microcosm cultivation.
• Co-occurrence network and functional analyses to identify keystone taxa.
• Construction and field testing of a SynCom composed of *Bacillus siamensis* and *Bradyrhizobium japonicum*.

Main Results:

• Identified keystone taxa promoting maize straw humification.
• Constructed a two-membered SynCom (*B. siamensis* and *B. japonicum*) that enhances enzyme activity via cross-feeding.
• SynCom inoculation improved straw humification and SOC in field experiments by enhancing the microbial carbon pump.

Conclusions:

• A systematic approach for identifying keystone taxa and constructing SynComs for straw humification was developed.
• The engineered SynCom effectively promotes maize straw humification and increases soil organic carbon.
• This strategy offers a promising method for improving soil health and agricultural sustainability.