Author: Prajina Neupane
Agriculture and Forestry University
Vermi – worms Compost – manure
Therefore, vermicompost is the product of decomposition process using various species of worms, usually red wrigglers, white worms and other species of earthworms to create a mixture of decomposing vegetables or food wastes, bedding materials and vermicastings. The rearing of worms for this purpose is termed as vermiculture and the process is vermicomposting, which is a bio-oxidative process where detritivores earthworm species interact with microorganisms, accelerating the stabilization of organic matters.
SPECIES OF EARTHWORMS SUITABLE FOR COMMERCIAL VERMICOMPOSTING
Soil is not required in vermicomposting since the organic matter acts as both the substrate and food. Thus, only epigeic earthworms can be used in the process. Several earthworm species have been evaluated for their potential use in vermicomposting, some of which are given below:
Perionyx excavatus etc.
Among all, the most commonly used species worldwide are Eisenia fetida (tiger worm) and Eisenia andrei (redworm).
|Commercial Earthworms||Common Earthworms|
|Epigeic earthworms||Endogeic earthworms|
|Live in the organic horizon, on or near the soil surface||Live deeper in the soil profile|
|Mainly feed on decaying organic matters such as vegetable and animal debris||Mainly feed on soil and the associated organic matters|
|Usually small, pigmented and have high metabolic and reproductive rates that allow them to adapt to the changing environmental condition of the soil surface.||They have little pigmentation, lower rate of reproduction and construct highly branched horizontal galleries, which get filled with excrements as worms move along the organic-mineral horizon of the soil.|
|They have shorter life cycle and under unfavorable condition, they suffer high mortality increasing the reproduction rate greatly.||They have longer life cycle and are more resistant to unfavorable condition such as drought and lack of food.|
|They also display high rate of consumption, digestion and assimilation of organic matter and play a key role as litter transformers, producing holorganic casts.||
Note: Although morphologically similar, E. fetida and E. andrei are phylogenetically and biologically different species and do not interbreed. All other species used in vermicomposting are also separate species and do not interbreed as well. Therefore, the presence of more than one species in mixed culture leads to lower reproduction rate and a less successful vermicomposting system due to competition between species for survival.
HOW TO CONSTRUCT VERMICOMPOSTING SET UP?
According to one’s convenience and availability, plastic tubs, wooden boxes or cemented tanks can be used as vermicomposting set but drainage is compulsory. The set up should be wider and less deep with convenient length. Generally, plastic bins are more vulnerable to overheating when exposed to direct sunlight, but retain more water compared to wooden bins.
Preparation of Vermibed
- Shredded newspaper or shredded cardboard or dried leaves or straw (cut into small pieces)
- Compost starter
- Food wastes
- Try to set up the bin about two days before adding worms so that the moisture level reaches equilibrium and lets the food waste start to break down – worms do not actually eat fresh food but rather feed on microbes that thrive by decomposing food scraps.
- Cover the bottom of the bin with a layer of pre-moistened newspaper and mix it with hand so that it is fairly fluffed up. You can also use other type of bedding materials such as shredded cardboard, straw, dried leaves etc.
Bedding is done to serve several purposes:
- To provide a carbon source.
- To provide bulk and help keep food waste from matting down and blocking airflow.
- To absorb excess moisture.
Straw can provide carbon and bulk but does not absorb much moisture, whereas cardboard doesn’t bulk up very well. Newspaper meets all three purposes so, is best for bedding. If newspaper is not available, use a mixture of other materials so all needs are met.
- You can add compost starter as an additional organic material, which is optional, but can be very helpful when setting up a new bin as it can help introduce proper microorganisms to the system. A bit of near finished healthy compost from another bin can provide a starter microbe population that will reproduce and colonize faster than new microbes.
- If you are restarting the bin after harvesting, keep a small amount of the harvested compost to help ease the transition and keep the microbe population consistent.
- Add food waste. Start lightly, about a pound of food per pound of worms. The worms may be in shock upon entering the new system and make sure that you don’t overfeed them. For first feeding, you can apply food in a fairly even layer across the bin.
- If possible, cover the bin with fluffed layer of shredded newspaper and let the bin sit for a day or two before adding worms. If you cannot wait and the newspaper bedding is still dry, add a small amount of water and mix to moisten all materials.
- Add worms on the top and cover with a thin layer of shredded newspaper or moist gunny bags, but ensure proper air circulation.
Maintaining Moisture and Temperature:
Epigeic earthworms require a substrate with relatively high moisture content. Moisture content between 80-85% will ensure high growth rate, which can be manually determined – the substrate should be damp, but when a handful is squeezed by hand, barely any water should escape. Watering is required at regular intervals depending upon humidity, temperature and moisture content. Proper drainage is also must as earthworms can’t survive in waterlogged condition. The temperature of the substrate should be between 20-25°C for optimal development of epigeic earthworms. They will also breed successfully under these conditions.
WHAT TO PROVIDE AS FEED?
Like other creatures, earthworms do have their own food preferences. One must provide food which are moist, soft and low in acidity. As a general rule, feed worms a mix of equal parts “brown” and “green” foods. Browns are high in carbon and carbohydrates, while greens add a lot of nitrogen and protein to the soil.
Greens include green vegetables and other natural foods – melon rinds, lettuce, carrots, fruit peels etc. and they need not necessarily be green. Browns may be food or non-food items, such as coffee grounds, paper, egg shells, cartons and dry leaves.
Here is list of some worm feeds:
- Cattle manure, poultry manure, sheep/ goat manure (pre-decomposed)
- Hog manure, Rabbit manure (pre-decomposed)
- Fresh food scraps (e.g. peels, other food preparation wastes, leftovers, commercial food processing wastes)
- Pre-composted food wastes
- Biosolids (human wastes)
- Legume hays
- Grains (e.g. feed mixture for animals)
- Corrugated cardboard
Note: Do not feed meat, egg and meat products as they attract housefly and other insects for breeding whose larvae and maggots feed on earthworm. Avoid milk and milk products as they are high in protein content and produce more heat on decomposition. Also avoid citrus fruits and peels as they are highly acidic.
HARVESTING OF VERMICOMPOST
Depending upon temperature and climate, it takes about 6-12 months to form a fully prepared vermicompost. Some methods of harvesting vermicompost are:
After all the compost has been converted into worm casting including bedding, dump the whole bin out on a tarp on a sunny day. Form a couple of small pyramids of worm castings and the worms will burrow into the pyramids as they dislike light. Then, carefully brush worm castings off outside of the pyramid and set aside. The worms will burrow again. Repeat until almost all worm castings are harvested and only a small ball of worms is left. Refill the bin with fresh worm bedding and add your composting worms back to the bin.
Side to Side Migration-
After all the bedding has been processed into vermicompost, pull it all to one side of your worm compost bin leaving the other side open. Fill the open side with fresh worm bin bedding. Over a couple of weeks, most of the worms will move to the new side and you can pull the finished worm compost.
Use an old bag that has many holes in it. Fill the bag with some fresh bedding and some of their favorite food. Tie the bag shut and place it in the vermicompost bin. Be sure the worms don’t have any other food in their bin except for in the worm corral bag. Wait a couple weeks for the worms to get inside the bag and then simply lift out your worm corral. Now, the worm castings can be harvested and used in your field.
PRECAUTIONS AND MAINTENANCE
- Bedding should have high C:N ratio. Carbon source should be more than protein source since protein source on decomposition produces more heat which is not good for earthworms.
- Do not put fresh cowdung on the bed because it produces more heat and can kill the earthworms.
- Maintain moisture, shade (by using low thatched roof), temperature ranging between 10-30° C and proper airflow in the vermi-bed.
- Protect earthworms from natural enemies like frogs, toads, snakes, birds, lizard, ants, moles, larva and maggots of dipterans, beetles (like Devil’s coach horse, Rove beetles, larger ground beetles etc.), Centipedes, leeches, slugs and semi-slugs like
- Cow dung should not be hard and dry, make the dung wet and cold before using it as earthworms’ feed.
- Take care that there is no outbreak of termites and red ant in the bed.
- Do weeding every week in the bed, so that earthworms can get proper air flow.
- Worms should not be injured during handling. Avoid using sharp tools.
- Frequent observation of culture bed is essential as accumulation of cast retards growth of worms.
- Minimum space required is 2 sq. meter per 2000 worms with 30-45 cm thick bed.
- Addition of inoculum as a bait from earlier habitat helps in early adaptation of worms to new site of rearing.