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Vermicomposting: Transforming waste into Gold

Introduction

Vermicomposting is a simple biotechnological process in which certain species of earthworms are used to enhance the process of waste conversion and produce a better end product. It is one of the easiest methods to recycle agricultural wastes and to produce quality compost. Earthworms consume biomass and excrete it in digested form called worm casts. Worm casts are popularly known as ‘Black Gold’. The casts are rich in nutrients, growth promoting substances, beneficial soil micro flora and having properties of inhibiting pathogenic microbes. Vermicomposting differs from composting in several ways. It is a mesophilic process, utilizing microorganisms and earthworms that are active at 10–32°C (not ambient temperature but temperature within the pile of moist organic material). The process is faster than composting; because the material passes through the earthworm gut, a significant but not yet fully understood transformation takes place, whereby the resulting earthworm castings (worm manure) are rich in microbial activity and plant growth regulators, and fortified with pest repellence attributes as well. In short, earthworms, through a type of biological alchemy, are capable of transforming garbage into ‘gold’.

Materials used for vermicomposting

Generally, dried chopped crop residues, tree leaves and animal dung mostly cow dung are the key raw materials used for vermi composting. Decomposable organic wastes such as animal excreta, kitchen waste, farm residues, organic sludge, weeds and forest litter can also be used as composting materials which are ideal for earthworms. Mixture of leguminous and non leguminous crop residues enriches the quality of vermicompost. There are different species of earthworms viz. Eisenia foetida (Red earthworm), Eudrilus eugeniae (Night crawler), Perionyx excavatus etc. Red earthworm is preferred because of its high multiplication rate and thereby, converts the organic matter into vermicompost within 45-50 days. Since it is a surface feeder, it converts organic materials into vermicompost from top.

Preparation of Vermicompost

Following steps are followed for vermicompost preparation:

1.       Vermicomposting unit should be in a cool, moist and shady site

2.       Cow dung and chopped dried leafy materials are mixed in the proportion of 3: 1 and are kept for partial decomposition for 15 – 20 days.

3.       A layer of 15-20 cm of chopped dried leaves/grasses should be kept as bedding material at the bottom of the bed

4.       Beds of partially decomposed material of size 6x2x2 feet should be made

5.       Each bed should contain 1.5-2.0 q of raw material and the number of beds can be increased as per raw material availability and requirement

6.       Red earthworm (1500-2000) should be released on the upper layer of bed

7.       Water should be sprinkled with can immediately after the release of worms

8.      Beds should be kept moist by sprinkling of water (daily) and by covering with gunny bags/polythene

9.       Bed should be turned once after 30 days for maintaining aeration and for proper decomposition

10.   Compost gets ready in 45-50 days

11.    The finished product is 3/4th of the raw materials used.

Harvesting

1.       The compost is ready when the material is moderately loose and the colour of the compost is dark brown. Vermicompost can now be harvested from the pit.

2.       Stop watering two to three days before empting the beds so that the worms get separated from the compost. The worms can also be separated using sieves/meshes.

3.       The harvested material should be placed in a heap in the sun so that most of the worms move down to the cool base of the heap

Precautions during composting:

1.       The floor of the unit should be compact to prevent earthworms’ migration into the soil.

2.       15-20 days old cow dung should be used to avoid excess heat.

3.       The organic wastes should be free from plastics, chemicals, pesticides and metals etc.

4.       Aeration should be maintained for proper growth and multiplication of earthworm

5.       Worms should not be injured during handling

6.       Optimum moisture level (30-40 %) should be maintained

7.       18-25 degree centigrade temperature should be maintained for proper decomposition.

Nutrient content of vermicompost

Parameters

Content (%)

pH

6.8

OC

11.88

OM

20.46

C/N ratio

11.64

Available N

0.50

Available P

0.30

Available K

0.24

Ca

0.17

Mg

0.06

Importance of Vermicompost:

Source of plant nutrients

Earthworms consume various organic wastes and reduce the volume by 40–60%. Each earthworm weighs about 0.5 to 0.6 gm, 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 percent age (nearly two fold) of both macro and micronutrients than the garden compost. Plant growth promoting activity of vermicompost was tested using a plant bioassay method. The plumule length of maize (Zea mays) seedling was measured 48 h after soaking in vermicompost water and in normal water. The marked difference in plumule length of maize seedlings indicated that plant growth promoting hormones are present in vermicompost.

Improved crop growth and yield

Vermicompost plays a major role in improving growth and yield of different field crops, vegetables, flowers 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 mungbean was also significantly higher with vermicompost application. Likewise, in another pot experiment, the fresh and dry matter yields of cowpea (Vigna unguiculata) were higher when soil was amended with vermicompost than with biodigested slurry.

Role in Nitrogen cycle

Earthworms play an important role in the recycling of N in different agro-ecosystems, especially under jhum (shifting cultivation) where the use of agro-chemicals is minimal. It is reported that during the fallow period intervening between two crops at the same site in 5 to 15 year jhum system, earthworms participated in N cycle through cast egestion, mucus production and dead tissue decomposition. Soil N losses were more pronounced over a period of 15 year jhum system.

Improved soil physical, chemical and biological properties

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 affects plant growth. The application of organic matter including vermicompost favorably affects soil pH, microbial population and soil enzyme. It also reduces the proportion of water-soluble chemical species, which cause possible environmental contamination.




Writer :: Manav and Bharat Taindu Jain      Published on :: 05-Nov-2018


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