The formation of macro-aggregates is an important process to fertile soils. Plant roots, earthworms, microbes such as fungi and bacteria are known to be involved in the formation, but their interactions are not fully understood.
Thus, the objectives of the study were to: (1) know how macro-aggregate formation is differed among plant species, (2) know how plant-earthworm interaction affect the formation, and (3) explain how plant-earthworm interaction affect the formation from the point of the microbial community.
We conducted a pot-scale experiment using Sorghum, Rhodes grass, and Clover, with and without endogeic earthworms (Eisenia japonica). Then we analyzed the bulk soil, soil from the rhizosphere, and soil from earthworm burrows for their microbial community structures as well as the changes in the quantity of macro-aggregates.  
The presence of earthworm positively impacted coarse-macro-aggregate formation in pots with Rhode grass and Clover but not in Sorghum. Earthworm presence also influenced bacteria and fungi in bulk soil. In brief, root length, bacterial abundance, EE-GRSP concentration, and fungal community structure in bulk soil were positively correlated to the amount of coarse-macro-aggregate.
Plant species determine the amount of coarse-macro-aggregate. Furthermore, plant-earthworm interaction affects the soil bacteria and fungi, which might contribute to stabilizing coarse-macro-aggregate.