Identification of Suitable Earthworm Species for Introduction of Vermicompost Production in Sri Lanka

Earthworms (Annelida: Oligochaeta) contribute to soil fertility and play a key role in composting garbage. Recycling of organic wastes using earthworms produce compost known as vermicompost. This method is one of speediest, environmental friendly and economically viable method of compost production which has gained importance due to higher in plant nutrient contents compared to compost produced from traditional methods. Different methods of vermicomposting have been introduced to Sri Lanka using local and imported earthworms by several governmental and non governmental organizations. However, little information is available in successful production of vermicompost programs in Sri Lanka while in India, Cuba and China have large scale of vermicomposting programs using identified species of earthworms. Major constraint of development of vermi-technology in Sri Lanka is lack of knowledge on taxonomy and biology of earthworms in naturally occurring in different habitats. Thus, study on taxonomy, diversity, ecological category and lifecycle pattern of earthworms is essential to identify suitable earthworm species for development of technology for vermicompost production in Sri Lanka. The study was carried out in seventeen different sites including agricultural (organic farms, integrated farms, plantations, home garden and University Park) as well as natural sites (primery forest, secondary forest, mountain forest, dry patana and wet patana grassland) in wet and intermediate zones of Sri Lanka for the period of four years (1996-2000). Soil samples were collected from an area of 0.25 m2 and the depth was 0.40 m from ten monoliths collected randomly from each site. Earthworms were hand sorted and collected from each sample. Collected earthworms were identified and classified using their external and internal morphological features with comparison of available taxonomic descriptions and keys. The reproductive system is a major distinguishing feature and the morphology of cocoons were also used to identify common earthworms in the field. Further, earthworms are divided in to three major ecological categories mainly based on their feeding habit and habitats, namely epigenic, endogenic and anecics. Epigenic earthworms have a short lifecycle, having small pigmented body, tolerance to environmental stresses, produce more cocoons within short period and eating & living in decaying organic garbage.  Endogenic earthworms have comparatively large unpigmented body, long lifecycle, intolerance to environmental stresses and produced few cocoons per year and eating & living in the soil Anesic earthworms are pigmented and large earthworms living in at least below 1m depth and eating a decaying organic matter.
Twenty-two morphospecies of earthworms including fifteen genera belonging to nine families have been identified representing from 17 selected sites. Of the 9 families, five families including 9 genera and 3 species have not been recorded previously from Sri Lanka. According to ecological categories, there were 6 species of epigenic forms, 15 species of endogenic forms and single species of anecics forms were recorded. Epigenic earthworms were commenly used for vermicompost production. Among the epigenic forms, Periyonix excavatus, Eudrilus Eugenia, Eisenia foeitida, Dichogaster bolaui and Lampitto mauritii were commonly found man made agro-ecosystems where degraded organic matter is accumulated. According to the literature and information those identified species are being used in vermicomposting world wide. However, three of them are namely Periyonix excavatus call as “red wriggler”, Eudrilus eugenia call as African night craw” and Eisenia foetida call as “Tiger worm” commercially cultured and widely used in vermicomposting world wide.
This research indicated that there are adequate earthworms resources are available in Sri Lanka for implementing of successful vermicomposting program without importing of earthworms from other countries.

Keywords: Earthworms, Organic matter, Vermicomposting

Samaranayake, J.
Plant Genetic Resources Centre, Sri Lanka