Effects of earthworms on the performance of Lolium multiflorum, soil properties and microbial communities in its root-zone soil under cadmium stress

Phytoremediation is an environment friendly, sustainable, and aesthetically pleasing technology for remediating heavy metal polluted soil. Earthworms are ubiquitous macrofauna in the soil ecosystem that play an important role in maintaining soil health and fertility. However, the understanding of earthworms' effect on phytoremediation remains limited.

In a greenhouse experiment, Lolium multiflorum was subjected to three levels of cadmium (0, 20, or 100 mg kg⁻¹) fully crossed with two levels of earthworm treatments (i.e., with or without Eisenia foetida Savigny).

Plant growth was inhibited while the root-shoot ratio and nitrogen accumulation in shoots were increased under 100 mg kg⁻¹ cadmium. Earthworms interacted with cadmium level to affect the total phosphorus content in soil. Furthermore, earthworms enriched specific microorganisms and significantly influenced bacterial communities under 0 and 20 mg kg⁻¹ cadmium. We observed a significant enrichment of specific microbial species in cadmium polluted soil when earthworms were present. Earthworms’ presence increased the sensitivity of fungal communities in soils polluted with cadmium.

Both earthworms and cadmium had certain impacts on the growth of plants, soil properties and microbial communities in root-zone soil. Moreover, the results suggest that earthworms may alleviate some negative effects of cadmium on soil microorganisms. The findings highlight the effect of earthworm on plant performance, soil properties, and root-zone microbial communities under cadmium stress, providing valuable insights into its role in phytoremediation of soils polluted with metals.