Vermi - composting

‘Vermin’ stands for earthworm. The organic matter when subjected to decomposition with the help of earthworms the resultant product is ‘vermi compost’ and the process is known as vermicomposting. The product is the result of organic waste consumed by earthworm, digested and passed through gut and excreted in the form of granules. Iy is a mesophilic process, utilizing microorganisms and earthworms that are active at 10-32^oC. the vermocompost is rich in microbial activity and plant growth regulators, and fortified with pest repellence attributes as well.

Scope 

From vermiculture, we get well decomposed vermi casts, which can be used as manure for crops, vegetables, flowers, gardens, etc. In the process, earthworms also get multiplied and the excess worms can be converted into vermiprotein which can be utilised as feed for poultry, fish, etc. Vermi-wash can also be used as spray on crops. Thus various economic uses can be obtained from organic wastes and garbage and prevent pollution. It has been estimated that organic resources available in the country alone can produce not less than 20 million tonnes of plant nutrients (NPK). The five major crops viz., paddy, jowar, wheat, bajra and maize alone are estimated to yield approximately 141.2 million tonnes of straw and legumes add another 10.0 million tonnes. It is estimated that annual domestic wastes of 25 million tonnes, 320 million tonnes of cattle manure and 3.3 million tonnes of poultry manure are generated annually in India. Vermicompost technology has promising potential to meet the organic manure requirement in both irrigated and rainfed areas. It has tremendous prospects in converting agro-wastes and city garbage into valuable agricultural input. When organic manures are used, the chemical nutrients are also utilised well by crops as they improve soil health and balance the negative effects of chemicals.

Role of Soil biota      

Soil is a natural medium for growth and multiplication of plants, microbes and various other soil biota. Organic matter is an important constituent of soil, which include, undecomposed and partially decomposed plant and animal residues, the live and dead micro organisms, as well as highly decomposed and colloidal end product called humus. In the biological system, plants as producers, animal and man as consumers and soil organisms as decomposers are dependent on each other in a particular habitat called eco system. Soil organisms like bacteria, fungi, ants, termites and earthworms etc. are responsible to improve health of the soil. A healthy soil will always be rich and diverse in these biota. Earthworms bioconvert the organic wastes into plant nutrient resources and thereby act as catalysts in protecting our environment.

Role of Organic matter

The organic matter is food for most soil micro organisms. In most fertile soils the organic matter forms about 3-5% of the dry weight of the soil. With cultivation, in tropics the organic matter gets oxidised quickly. Lack of organic matter results in adverse effect on the physical, chemical and biological properties of soil. Mineralisation of soil organic matter results in release of plant nutrients and other plant growth stimulating humus products. Indirectly organic matter acts a reservoir of the plant nutrients, carbon compounds and regulates the availability of plant nutrients.

Location of  the vermi unit

The vermicompost unit may be set up on the farmers field, by digging pits in the soil. But the efficiency can be increased in cement tanks, wooden boxes or plastic tubes as per the availability of wastes. The tank construction may be done on raised lands and above ground level to avoid flooding and water logging. The floor should be constructed in such a way as to provide slope on all directions from the center of the tank.

It must be understood clearly that earthworms are preyed by a number of predators like rats, frogs, lizards, ants and hence the success of the composting depends on the housing/infrastructure developed for vermiculture. The efficiency and speed of composting depends on the vigour and biological activity of the worms. Therefore, infrastructure should be developed well to ensure congenial environment for growth and multiplication.

Implements required

Shovel, crowbar, spade, bucket, spreader, wiremesh (3 mm), bamboo baskets, dung fork, trovel, chaff cutter (hand operated), sieve etc.

Techinical parameters

The technical parameters of vermicompost unit are given below -

Species of Earthworms

Species of earthworms most suitable for vermicomposting are Eisenia fetida, Eudrilus eugenae and Derinoyx excavatus. Depending upon the tank size, about 200 to 500 young healthy earthworms of the identified species may be kept in mud pots with moist soil and brought to the site and released into the culture tanks as explained below. The earthworms for starting a vermicompost unit can be obtained from other farmers who are already engaged in the activity, voluntary agencies, KVKs, state agriculture department, Research units of Agricultural University who will also provide technical guidance if required.      

Feed Ingredients

Earthworms eat 10 % soil and 90 % organic waste materials. Cow dung and agro-wastes in the ratio of 1:1 to 1:3 may be mixed and allowed to predecompose for about 2 weeks in a separate tank adjacent to the vermicompost tank, before being fed to the earthworms. Earthworms do not have mandibles and hence, only predecomposed matter needs to be added. Agro wastes may cover farm waste like straws, feed residues, green leaves, grasses, toppings from trees, cattle shed wastes, kitchen wastes, animal dung of all animals except poultry birds, vegetable/flower wastes from markets, agro-industries waste like sugar factory press mud, etc. The ideal feed for earthworms could be leaf litters mixed with cowdung which helps to decompose the waste and increase the earthworm population.

Process of making vermicompost

The ideal tank size for small scale production is 10’ x 6’ x 2.5’ (150 cu. ft.). Care should be taken to create adequate no.of holes (about 8 holes of 5 cm. diameter at the bottom) to facilitate drainage of excess water. The feed mix is poured over a bedding of earthworms of about 15 to 20 cm thick. The bedding may comprise broken bricks, stone pieces, saw dust, sand and soil. Earthworms should be released in this bedding followed by feeding material. The predecomposed material need not be added in layers but its depth should not be more than 1.5 to 2 feet. The tank should be well aerated and kept moist by periodic sprinkling of water especially in the first 6 to 8 weeks. The tank is covered with thatched roof to maintain the moisture of the tank feed (40% moisture should be maintained). Under sub optimal moisture conditions the earthworms have a tendency to move downwards towards the bed of the tank. When the moisture, temperature and organic matter are optimum, the size, weight and cocoon producing capacity of earthworms increases.  

Conversion

a) One kg. of worms numbering about 600 to 1000 can convert 25 to 45 kg. of wet waste per week. The compost recovery would be around 25 kg. per week under well managed conditions.

b) One kg. of earthworms produce a minimum of 2000 and a maximum of 5000 cocoons per week. The viability of cocoons will be around 60 per cent and incubation period is about 2 weeks. However with preservation the viability can be retained upto 3 months. They become sexually matured in about 6 to 8 weeks. Each matured earthworm lays eggs at 7 to 10 days interval and with the period of 12 months, each earthworm produces 247 worms. The young worms take about 90 days to attain maturity and reproduction capacity. They have tremendous rate of growth if the conditions are congenial and feed is good. About 1 kg. biomass equivalent earthworms can become 20 kg. in 4 months and 200 kgs in another 4 months.

c) Laboratory observations indicate that 100 gms of good quality compost contains about 25 to 30 cocoons. From the original inoculam of earthworms adequate no. of worms can be multiplied for further production of vermicompost. Also the excess production of worms can be sold to new entrepreneurs or as worm meal to poultry or fish producers. Each beneficiary depending upon the expertise and need, may start with a minimum of 3 tanks so as to get the vermicompost throughout the year.   

Harvest

The total decomposition may take about 75-100 days depending on various factors. Therefore one tank may be used 4 to 5 times in a year for vermicompost. A few days before the harvest watering of the tank is discontinued to allow migration of worms towards the bottom of the bed. The compost is then transferred outside without disturbing the bed and heaped on a plain open surface. The left over worms will then migrate to the center of the heap and can be collected and put back to the tank after segregation from the compost. The compost is sieved through a 3 mm mesh and then packed in gunnies. About 1700 kg. of compost can be obtained from each cycle. While sieving the unhatched cocoons can also be retrieved. The excess worms can be retrieved and put in new tanks or sold or can be sun-dried to make vermi protein. Per one cubic metre of composting volume, about 2 kg. of worms (i.e. about 2000 nos.) need to be retained.  The compost should be sun-dried and then bagged for sale/use. 

Application of Vermi-compost

In orchards the does depends on the age of the tree. A deep ring of 15- 20 cm is to be formed around the tree. A thin layer of dry cow dung with 2-5 kg of vermin-compost is than applied. This is covered with a thin layer of soil. This ring is mulched with organic matter and a light spray of water is given, for general use in agriculture, vermin-compost is mixed with equal quantity of dried cow dung. This is broadcasted when seedlings are 12-15 cm high and water should be sprinkle.

General rate of application in different crops:

Field crops:                       3-5 t/ha

Vegetable crops:               5-7 t/ha

Fruit crops:                        3-5 kg/tree

Flower crops:                    100 g/pot

Nursery bed and lawns:     1-2 kg/m²

Table.  Average nutrient content of vermi-compost and compost.

Benefits of application of vermi-compost 

1. Enhancement of soil productivity
2. Recycle of organic wastes is achieved.
3. The produce with better taste, luster and keeping qualities without toxic residues can be produced, fetching a higher price.
4. Improved soil physical, chemical and biological properties.
5. It is a cost-effective pollution abatement technology.
6. Waste creates on pollution, as they become valuable raw materials for the soil biotechnological processes.
7. Soil salinity is reduced with low soil erosion and runoff.
8. They promote the growth of microorganisms in their gut by favorable condition. 

Precautionary measures in vermi-composting

• Protect the composting from direct sun and rain
• Protect the unit from bird, lizard and rat by covering with a net
• Prevent the attack of ants by sprinkling of salt/turmeric powder
• Application of right number of earthworms
• Proper and regular watering

References

1)      Gupta,P.K .(2003). A hand book of Soil, Fertilizer and Manure. Agrobios, Jodpur, India.

2)      Sharma,A.K.. (2004). A handbook of Organic Farming. Agrobios, Jodpur, India.

3)      Palaniappan,S.P. and Annadurai,K. (2003). Organic Farming: Theory and Practice. Scientific Publication, Jodpur, India.

4)      Singh,S.S. and Singh, Rajesh (2008). Sustainable Agriculture for Secured Survival. Kalyani Publishers. New Delhi.India.

Authors:

Dinesh Sah and P.Debnath

Department of Natural Resource Management,

College of Horticulture and Forestry, Central Agricultural University,

Pasighat (East Siang)- 791102, Arunachal Pradesh.

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