Background: Sorghum Bicolor L. and arbuscular mycorrhizal fungi (AMF) have a mutually beneficial relationship that influences the movement of carbon below ground. The rising concentration of carbon dioxide (CO₂) in the atmosphere during the middle and later part of the twenty-first century (550–700 ppm) is expected to change the dynamics of below-ground carbon storage. To increase climate-resilient and carbon-efficient agricultural systems, it is vital to understand how these two species interact.
Objectives: Objectives for this article include: (1) Identify the processes and structures that control AMF (arbuscular mycorrhizal fungi)-mediated carbon distribution to sorghum (Sorghum Bicolor); (2) quantify the contribution of glomalin-related soil protein (GRSP) and hyphal turnover to stable soil organic carbon (SOC) pools; and (3) evaluate how elevated CO₂ impacts mycorrhizal network dynamics and microbial communities in the rhizosphere.
Methods: A total of 54 experiments from around the world were conducted to look at how carbon gets assigned in the sorghum system and to see if the amount of carbon in the soil from AMF, GRSP, and carbon stabilization in soil differed under normal or higher CO₂ levels.
Results: Sorghum plants inoculated with arbuscular mycorrhizal fungi (AMF) grown in an elevated carbon dioxide (CO₂) environment had 23-47% greater underground carbon allocation than controls without AMF. Glomalin root-associated soil polymer (GRSP) concentration in soil increased by 18-35% and soil aggregate stability was improved as a result of increased total glomalin production. The rate of AMF fungal colonization increased by 15-28% and greater amounts of extra-radical fungal hyphal biomass associated with the AMF also contributed to a higher production of glomalin and soil organic carbon (SOC) stabilization via organo-mineral interactions. In addition, AMF symbiosis improved the stress tolerance of host sorghum plants, as demonstrated by increased water-use efficiency (20-35%) and nitrogen-use efficiency (15-22%). The synergistic effects of AMF and elevated CO₂ also enhanced total host plant biomass and rhizodeposition, providing 12-28% of the total SOC input to a soil ecosystem.
Conclusions: The enhanced capacity for carbon storage that happens as a result of the interaction between arbuscular mycorrhizal fungi (AMF) and sorghum when grown under elevated concentrations of carbon dioxide (CO2) further supports the uses of both AMF and sorghum as critical components of climate-smart agronomy and carbon farming. Nonetheless, many important knowledge gaps exist regarding long-term carbon stabilization, soil priming effects and AMF species-specific relationships in semi-arid agroeocsystems. Future studies require the integration of prolonged agricultural field studies, omics-based study methods and isotopic approaches to establish strong proof-based strategies for carbon management.