Vermicomposting technology is one of the best options available for the treatment of organics-rich solid wastes. The term vermicomposting is coined from the Latin word ‘Vermis’ meaning to the ‘worms’. Vermicomposting refers to composting or natural conversion of biodegradable garbage into high quality manure with the help of earthworms. Earthworms play a key role in soil biology; they serve as versatile natural bioreactors to harness energy and destroy soil pathogens. The worms do so by feeding voraciously on all biodegradable refuse such as leaves, paper (non- aromatic), kitchen waste, vegetable refuse, cattle dung etc.
Earthworms play an important role in the recycling of N in different agroecosystems, especially under jhum (shifting cultivation) where the use of agrochemicals is minimal. Earthworms participated in N cycle through cast-egestion, mucus production and dead tissue decomposition.
Earthworms consume various organic wastes and reduce the volume by 40–60%. Each earthworm weighs about 0.5 to 0.6 g, eats waste equivalent to its body weight and produces cast equivalent to about 50% of the waste it consumes in a day. These worm castings have been analyzed for chemical and biological properties. The moisture content of castings ranges between 32 and 66% and the pH is around 7.0. The worm castings contain higher percentage (nearly twofold) of both macro and micronutrients than the garden compost.
Limited studies on vermicompost indicate that it increases macropore space ranging from 50 to 500 µm, resulting in improved air-water relationship in the soil which favorably affect plant growth . The application of organic matter including vermicompost favorably affects soil pH, microbial population and soil enzyme activities. It also reduces the proportion of water-soluble chemical species, which cause possible environmental contamination .
Vermicompost plays a major role in improving growth and yield of different field crops, vegetables, flower and fruit crops. The application of vermicompost gave higher germination (93%) of mung bean (Vigna radiata) compared to the control (84%). Further, the growth and yield of mung bean was also significantly higher with vermicompost application.
For general field crops: Around 2–3 t ha-1vermicompost is used by mixing with seed at the time of sowing or by row application when the seedlings are 12–15 cm in height. Normal irrigation is followed.
For fruit trees: The amount of vermicompost ranges from 5 to 10 kg per tree depending on the age of the plant. For efficient application, a ring (15–18 cm deep) is made around the plant. A thin layer of dry cow dung and bone meal is spread along with 2–5 kg of vermicompost and water is sprayed on the surface after covering with soil.
For vegetables: For raising seedlings to be transplanted, vermicompost at 1 t ha-1 is applied in the nursery bed. This results in healthy and vigorous seedlings. But for transplants, vermicompost at the rate of 400–500 g per plant is applied initially at the time of planting and 45 days after planting (before irrigation).
For flowers: Vermicompost is applied at 750–1000 kg ha-1.
For vegetable and flower crops vermicompost is applied around the base of the plant. It is then covered with soil and watered regularly.