Effects of straw returning after anaerobic microbial pretreatment on soil carbon sequestration and emission reduction

Soil carbon sequestration benefits are critical for agricultural development, and irrational agricultural waste disposal practices can lead to significant carbon emissions. Returning straw is known to enhance soil organic carbon, making strategies to accelerate straw degradation highly valuable for agricultural carbon sequestration. Anaerobes have demonstrated strong capabilities in accelerating lignocellulose degradation. However, the influence of straw on the transformation process of carbon, and the priming effect of soil carbon, needs to be further explored. This study utilized rumen microorganisms with mainly anaerobes for straw pretreatment, and employed isotope tracer method to simulate carbon transformation after straw returning. The pretreatment of ¹³C-labelled straw with RMs for 6 hours significantly increased its decomposition rate by 79.37 %. While the cumulative CH₄ emission flux rose, along with an increase in the abundance of methanogen-associated mcrA genes, the total soil carbon content increased by 61.79 % over a 60-day experimental period. Enzyme activities in the soil increased significantly, facilitating lignocellulose breakdown. Canonical correspondence analysis indicated that CH₄ emissions were attributed to increased abundance of the anaerobes, while increased CO₂ emissions were associated with soil carbon sequestration. Meanwhile, the Proteobacteria is involved in soil carbon sequestration and CO₂ production. These results suggest that anaerobic microorganisms exhibit high efficiency in accelerating straw degradation rates and enhancing soil carbon content following a 6-hour pretreatment of straw. The capacity of anaerobic microorganisms to convert solid waste has been shown, and highlights their robust potential for agricultural waste management and carbon sequestration.