It elaborates on the types of burrow walls and the microbes associated with it. The present review emphasizes the interaction of microbes and earthworms and the significance of earthworm burrow wall as a 'hot spot' of microbial activity. The microorganisms associated with the burrow walls are species specific, different in composition and function and significantly different from soil only a few millimeters away.

This may be the case also with burrows since not all earthworms cast at the soil surface most species that deposit casts do so in their own burrows. It is proposed that the most important effect of earthworms on soils may be the stimulations of microbial activity that occurs in casts. Moreover, earthworm burrow walls harbour distinctive communities of soil animals like protozoa, nematodes and microarthropods, which presumably control microbial activity in these microhabitats. Since one half of the nitrogenous waste of an earthworm is excreted through the body surface, it presumably accumulates in the burrow walls and affects the soil microbial community in those areas. This role is achieved inside or in the vicinity of burrows. Due to their relatively large size and characteristic feeding behaviour, certain species have a significant impact on soil structure, soil fertility, plant growth and crop yield. The effects of earthworm activity on soil processes differ between ecological categories and species creating distinctive microhabitats for soil microorganisms and other invertebrates. Earthworms as ecosystem engineers play an important role in soil ecosystems.

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