Answer:
Symbiotic bacteria plus earthworms.
Step-by-step explanation:
Symbiotic bacteria is a type of bacteria which in which a bacteria lives in association with other organisms and gain benefits from one another. The nitrogen fixing bacteria lives in the roots of the leguminous plants which fixes nitrogen for the plant and in return, the plant provides food. earthworms increased the availability of nutrients, better drainage, and aeration of the soil which is very necessary for the plant growth.