It is estimated that the organic wastes from coconut based farming systems produce nearly 6 to 8 tonnes of coconut waste in the form of leaves, spathe, bunch waste, and husk of nuts available from one hectare of well managed coconut garden. This waste biological materials shall be converted into high value vermicompost.
Continuous application of chemical fertilizers alone causes degradation of soil health. If bio inputs like vermicompost are applied, the soil is protected from different forms of soil degradation. The vermicompost is an organic fertilizer that is abundant in enzymatically digested organic matter containing nutrients in easily available or mineralizable form. It is also rich in earthworm mucus containing energy sources. When vermicompost is added to soil, it will act as topsoil and enhance soil microbial activity, thus making soil alive. It is a finely divided peat-like organic material with excellent structure, porosity, aeration, drainage, and water holding capacity. The physical, biological, and chemical processes involved in plant growth and development are influenced by the addition of vermicompost. It is a better source of organic matter than other composts. The vermicompost improves soil aeration, and water holding capacity and thus facilitates better growth of the plant due to its granular nature.
The biodegradable agricultural and urban wastes can be converted into vermicompost using earthworms. Though, various species of earthworms are employed in the process of vermicomposting, epigeic species of earthworms have better potential as waste decomposers. The commonly used epigeic species are Eudrilus eugeniae, Eisenia foetida, and Perionyx excavatus. All these species are voracious feeders and can feed upon a wide variety of degradable organic wastes. Their high growth rate also helps in the quicker decomposition of the wastes.
Due to the presence of lignin and polyphenols, the natural decomposition of organic by-products and the release of nutrients is very slow. But the earthworms known as compost worms or manure worms, which survive only in organic matter, accelerate the decomposition of such organic materials. The technology of producing vermicompost from lignin-rich and highly recalcitrant coconut leaf litter using an indigenous strain of African night crawler earthworm, Eudrilus sp, was developed by ICAR-Central Plantation Crops Research Institute. A local strain of earthworm related to African Night Crawler (Eudrilus sp.) was identified, which is quite efficient in converting coconut leaves into granular vermicompost. This earthworm is dark violet, large sized, and their cocoon is spindle shaped, thick, and dark in colour.
The earthworm (Eudrilus eugeniae), converts coconut leaves into vermicompost in less than three months, Nearly 4 tonnes of quality vermicompost can be produced from the wastes generated from 1 ha of healthy coconut garden per year by this earthworm.
The preparation of vermicompost from dried coconut leaves using earthworms like Eudrilus eugeniae (African night crawler) is an effective way to recycle organic waste into nutrient-rich compost.
The preparation of vermicompost from dried coconut leaves using earthworms like Eudrilus eugeniae (African night crawler) is an effective way to recycle organic waste into nutrient-rich compost.
There are two components in the process of vermicomposting coconut leaves. One is maintaining of nucleus culture of earthworm Eudrilus sp. and another is vermicompost production on a large scale.
Culturing of earthworms:
Fallen and weathered coconut leaves are chopped into 15 cm pieces in a chaff cutter, and mixed with cow dung slurry in a 1:1 ratio(w/w). This substrate is pre-decomposed for 20-25 days with regular watering. The pre-decomposed material is then filled into plastic basins, cement tanks, or wooden boxes, or made into a 10 cm bed on the cement floor. The nucleus culture of Eudrilus sp. is then introduced into the above mixture at the rate of 50 worms per 10 kg of the substrate and properly mulched with dry grass, straw, or wet gunny bag. The units are protected from direct sunlight and watered regularly. Once a week, fresh cow dung slurry can be added to the material. Within 1-2 months, the earthworms multiply 300 times, which is used for large-scale vermicompost production from coconut leaves.
Large-scale vermicompost production
Large-scale coconut leaf vermicompost can be produced in pits, thatched sheds, open ground, and cement tanks. The bed system of composting carried out in cement tanks is ideal. Though the length and breadth of the tanks can be made as per convenience, the depth should not be more than 1 meter. Coconut leaves weathered for 2-3 months are to be used. After chopping off the thick base, cut dry coconut leaves into 2 or 3 pieces manually and fill inside the tank up to 1 foot height with their lower side up. A layer of cow dung slurry @10: 2 (100 kg leaves: 20 kg cow dung slurry) is spread over it. Three such layers can be accommodated in a 1 metre deep cement tank. Adequate moisture must be ensured by sprinkling water regularly and the whole substrate is allowed to pre-decompose for 20-30 days. Then add earthworms to tanks @ 100 worms/ 1000 kg substrate. Cover the tank with nylon mesh to prevent the entry of rats, birds, and rhinoceros beetles. The rhinoceros beetle can also be managed by application of Metarhizium anisopliae as well as crushed leaves of Clerodendron injortunatum. Water the tanks regularly to maintain at least 30-40% moisture. Avoid over watering as it will kill the earthworms. The level of the substrate will fall down to half the depth of the tank by 60-75 days indicating completion of vermicomposting. A maximum of 70% of inputs is converted to vermicompost. Stop watering at this stage and heap the compost in a mound to facilitate separation of the worms from the vem1icompost. Harvest vermicompost from the top of the mound, free of earthworms, after two weeks, and shade dry and pack for further use. Hand-sort earthworms accumulated at the bottom of the heap which can be used for further vermicomposting. The woody petioles and midrib remain partially decomposed. These can be added to the next round for complete vermicomposting.
A maximum of 70% of the substrate would be converted to vermicompost within 3 months. When the level of the substrate in the tank falls by more than 2 meters, stop watering, and composted material is heaped into a mound. The earthworms will move to the bottom of the mound. The vermicompost free of earthworms can be collected from the top layer of the mound after one or two weeks. This compost may be sieved and shade-dried. Earthworms accumulated at the bottom of the mound can be sorted and picked by hand and can be used for the next round of composting. Though the vermicompost production from coconut leaves can be carried out throughout the year, efficient compost turnover and multiplication of worms take place when the temperature is in the range of 28-32°C and relative humidity is above 90%.
Vermicomposting by using bio-shredder
Pulverize the coconut leaves along with thick woody petiole using a bio-shredder machine. Fill the pulverized materials into the tank with layers of cow dung as mentioned earlier. Add a layer of uncut coconut leaves or a coir-pith layer in between the pulverized substrate to prevent compaction. The rest of the procedure is similar to vermicompost production by using cut leaves.
Properties of coconut leaf compost
- The coconut leaf vermicompost produced by Eudrilus sp is dark brown coloured, granular matter.
- It has a highly desirable CN ratio (10:17), high organic carbon (18-20%), humic acid content (10-13%), and easily available important plant nutrients (N-1.8-2.1 %, P2O5-0.21 0.30%, K2O -0.16-0.4%).
- It has a pH of 6.0-6.2, a water holding capacity of 160-170%, and is also rich in plant growth promoting hormones like indole acetic acid, gibberellic acid, and phenolics.
- Biologically, the vermicompost has high counts of nitrogen fixing, phosphate solubilizing, cellulose degrading, and plant growth promoting bacteria like fluorescent Pseudomonads and Bacillus
