Abstract:In order to investigate the effects of lignin and earthworms and their combined effects on plant biomass and soil microorganisms, farmland soils were collected, and ryegrass pot experiments with different combinations of lignin and earthworms were setup. Based on the determination of biomass, combined with methods such as quantitative PCR and high-throughput sequencing, the effects of lignin and earthworms on soil bacterial and fungal communities were studied. The results showed that lignin significantly reduced ryegrass biomass, while earthworms could alleviate the inhibitory effect of lignin and promote ryegrass biomass. Lignin significantly inhibited the numbers of soil bacteria and fungi, and changed the community structures, and potential degrading bacteria such as Sphingomonadaceae and Methylophilaceae were significantly enriched. The effect of adding earthworms on soil microorganisms was relatively small, and the combined treatment of lignin and earthworms significantly increased the copy numbers of bacteria and fungi and changed the abundance of the aforementioned degrading microorganisms. These results indicated that lignin reduced the copy number of soil microorganisms, and may inhibit plant growth through phenolic allelopathic substances released by its own degradation, which adversely affected the health of soil ecosystems. The combined treatment of earthworm and lignin affected the composition of lignin-degrading microorganisms in the soil, and both microorganism population and plant biomass tended to increase, suggesting that earthworm is beneficial to the microbial metabolism of lignin and lignin-derived phenolic compounds in the soil. This study provides a scientific basis for the utilization of lignin resources in farmland ecosystems.