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Vermicomposting, the conversion of organic waste into vermicompost, is mediated by the combined action of earthworms and microorganisms. This interesting and attractive alternative to regular composting turns organic waste into a substrate that can be used as a soil amendment and as a growing medium for use in horticulture. Soil is not required in vermicomposting as the organic matter acts as both the substrate and food, and therefore only epigeic earthworms can be used in the process. Several earthworm species have been evaluated for their potential use in vermicomposting, including Eisenia fetida (Savigny), Eisenia andrei (Bouché), Dendrobaena veneta (Rosa), Dendrobaena hortensis (Michaelsen) Eudrilus eugeniae (Kinberg), and Perionyx excavatus (Perrier). The species most commonly used in vermicomposting and vermiculture facilities worldwide are Eisenia andrei and Eisenia fetida. This chapter reviews and updates the controversy surrounding the taxonomic differentiation between E. andrei and E. fetida, and between D. veneta and D. hortensis, showing that these are all different species and emphasizing the importance of maintaining pure cultures in vermicomposting systems. In the final section, methods of cultivating epigeic earthworms to ensure high rates of growth and reproduction are described.
Earthworms (Crassiclitellata) are terrestrial oligochaetes that usually live in the soil. These invertebrates constitute the largest animal biomass in most temperate ecosystems, where they strongly influence the physical, chemical, and biological properties of soil. They play a key role in modifying soil structure and accelerating the decomposition of organic matter and nutrient cycling, ultimately shaping the structure and composition of the aboveground plant community.
BENEFITS OF EARTHWORMS
Earthworms help in the preparation of compost and maintaining soil health as follows:
- Improvement in fertility of soil.
- Mixing of sub-soil and top soil.
- Use of earthworms in recycling of city and rural wastes, sewage waste water and sludge, and industrial wastes, e.g. Paper, food and wood industries.
- Amelioration of physical condition of soil.
- Correction of undetermined deficiencies in plants.
- Used in Unani system of medicine for treatment of certain diseases Supplementing traditional feeds.
What Worms Need
The Five Essentials
Compost worms need five basic things:
- An hospitable living environment, usually called “bedding”
- A food source
- Adequate moisture (greater than 50% water content by weight)
- Adequate aeration
- Protection from temperature extremes
These five essentials are discussed in more detail below.
Bedding is any material that provides the worms with a relatively stable habitat. This habitat must have the following characteristics:
Worms breathe through their skins and therefore must have a moist environment in which to live. If a worm’s skin dries out, it dies. The bedding must be able to absorb and retain water fairly well if the worms are to thrive.
Good bulking potential
If the material is too dense to begin with, or packs too tightly, then the flow of air is reduced or eliminated. Worms require oxygen to live, just as we do. Different materials affect the overall porosity of the bedding through a variety of factors, including the range of particle size and shape, the texture, and the strength and rigidity of its structure. The overall effect is referred to in this document as the material’s bulking potential.
Low protein and/or nitrogen content (high Carbon: Nitrogen ratio)
Although the worms do consume their bedding as it breaks down, it is very important that this be a slow process. High protein/nitrogen levels can result in rapid degradation and its associated heating, creating inhospitable, often fatal, conditions. Heating can occur safely in the food layers of the vermiculture or vermicomposting system, but not in the bedding.
- Housing: Sheltered culturing of worms is recommended to protect the worms from excessive sunlight and rain. All the entrepreneurs have set up their units in vacant cowsheds, poultry sheds, basements and back yards.
- Containers: Cement tanks were constructed. These were separated in half by a dividing wall. Another set of tanks were also constructed for preliminary decomposition.
- Bedding and feeding materials: During the beginning of the enterprises, most women used cowdung in order to breed sufficient numbers of earthworms. Once they have large populations, they can start using all kinds of organic waste. Half of the entrepreneurs have now reached populations of 12,000 to 15,000 adult earthworms.