Effect of Selected Earthworms on Soil Fertility, Plant Growth and Vermicomposting

Abstract

The study investigates the effect of the endogenic earthworm Pontoscolex corathrurus on soil fertility and plant growth and three epigenic earthworms Periyonix excavatus, Eudrilus eugenia and Eisenia foetida on vermocomposting. At the organic farm site, year round abundance of P. corathrurus ranged from 4.95-19.6 for adults, 2-13.25 for juveniles and 2.2-7.3 for cocoons and in integrated farm site from 2.2-15.6 for adults, 1.5-11 for juveniles and 0.8-4.6 for cocoons. Effect of P. corathurus activity on soil fertility relieved that worm casts are significantly high in N (9.7-6.5%) and C (5.7-3.5%) content than surrounding soil. The pH of casts was neutral compared to the fluctuating pH of surrounding soils, in both sites Presence of P. corathurus in pot experiments, significantly increased the growth of Zea maiz when inoculated with 7 earthworms per pot. Culturing of the 3 selected epigenic earthworms in 7 composting media, containing cow dung, vegetable refuse and rice straw in different ratios, showed that presence of cow dung significantly increased the multiplication rate. Vermicomposting yielded com-post having higher N, P, Fe, and Mn levels, better particle size in comparison to the controls. Findings of the study confirm that earthworms commonly found in Sri Lanka can be easily used for soil fertility improvement and vermicomposting without having to import species from elsewhere.