As previously reported by Anderson (2009), the relationships between soil quality, earthworm activity and plant yield are not trivial and the effects of earthworm activity may not be apparent in all situations.
Although earthworm activity in this study did not influence plant growth and yield for the first maize planting, our study found that earthworms had a positive influence on tomato growth and a negative influence on the second maize cultivation when soils were amended with compost.
Further studies are needed to determine the different mechanisms involved.
The influence of earthworms on plant growth varies depending on the soil properties (Laossi et al., 2010) and plant species (Noguera et al., 2011).