Earthworms are very sensitive to hydrogen ion concentration. This is a major factor that limits the distribution of earthworms in different soils. While most species prefer a near neutral pH. Some species like lumbricus terrestris and Allolophora caliginosa thrive in soil with a pH of 5.2-5.4. Dendrobeaena octaedra can tolerate pH up to 4.5. Eisenia foetida prefers soil pH of 7.0-8.0. The activity of earthworms is greatly influenced by temperature. Upper lethal temperature ranges from 40 – 50 oC. Earthworms move away from the soil that has an unsuitable temperature.

Some species can survive for long at very low oxygen concentration. Earthworms are generally able to tolerate much higher carbon dioxide concentrations than those characteristics of normal soil air.

Earthworms are easily injured and even killed by exposure to light. They are particularly sensitive to ultraviolet light. Pigmented species are usually less tolerant to light. Surface feeding species come out to the surface only at night or at very low light intensities. Earthworms are usually absent in coarse-textured soils probably due to physical abrasion of their body surface. They are not also found in clayey soils, because such soils are generally deficient in oxygen. Diet of Earthworms mainly comprises organic debris that are at various stages of decay. Though the bulk of the ingested food is dead plant tissues: living organisms such as fungi and microorganisms are also consumed by them. Some species have been found to ingest certain parasitic nematodes.

Most earthworm species are sensitive to high salt concentration. Cultivated land usually contains lower populations of earthworms. This might be due to mechanical damage caused during cultivation operations. Fertilizers have a mixed effect on earthworm population. Liming is beneficial to the earthworms, especially in acidic soils. Plant protection chemicals are generally harmful to earthworms at varying degree, but the response is variable to different chemicals. They are suspected to be scavengers of heavy metals like Lead, Zinc and Copper.

5. Vermicomposting:
The preparation of vermicompost involves five stages viz., (a) collection of agro wastes (b) separation (c) partial digestion (d) inoculation and vermicomposting (e) screening and separation. Names of species suitable for vermicomposting in India are given below.