Assessing the methane mitigation potential of biochar and stover incorporation: Insights from the emission dynamics and soil microbiome in maize agroecosystems

Abstract

Methane (CH₄), a significant greenhouse gas, plays a critical role in the global emission dynamics, with agricultural soils exerting dual action on its atmospheric levels. While the efficacy of biochar and stover incorporation in mitigating CH₄ emissions in flooded soils is well-documented, their impact in upland systems, particularly within maize monocropping systems, has not been fully elucidated. This study presents a comprehensive analysis of the effects of biochar and stover incorporation on CH₄ fluxes and the associated methanogenic and methanotrophic microbial communities in a maize monocropping system in Northeast China, over a five-year period. The field study was established with three treatments: untreated control (CK), maize stover incorporation at 7.5 t ha⁻¹ yr⁻¹ (MS), and biochar application at 2.63 t ha⁻¹ yr⁻¹ (MB). Soil CH₄ fluxes, physical and chemical properties, and abundances of mcrA and pmoA genes were measured. Our findings indicated that MB and MS treatments effectively enhanced total CH₄ uptakes during the study period compared to CK by 55.3 % and 84.4 %, respectively. Both MS and MB treatments significantly increased soil organic C (SOC), easily oxidizable C (EOC), and dissolved organic C (DOC) contents, with MS demonstrating a more pronounced boost. A shift in the microbial community, favoring methanotrophy, was indicated by a reduced mcrA/pmoA ratio and altered gene abundances of mcrA and pmoA in the MB and MS relative to the CK. Pearson’s correlation analysis did not find a significant relationship between DOC and soil water content (SWC) with CH₄ emissions. The random forest (RF) model identified that pmoA, mcrA/pmoA, SOC, and mcrA were the top four determinants of CH₄ emissions. This study underscores the potential of biochar and stover return as effective strategies for reducing agricultural CH₄ emissions and emphasizes the necessity of elucidating the microbial underpinnings involved. Further research is warranted to refine these practices for diverse agricultural contexts and to evaluate their long-term environmental efficacy.