[Editor’s Note: Bruce is Project Manager of Solar Roots, and runs a small demonstration farm in Pyin Oo Lwin, Myanmar. Bruce comes from an engineering background and offers regular trainings on his solar power technologies and vermicomposting systems among other things. Bruce can be reached at firstname.lastname@example.org]
Introduction to Vermiculture
There are over 6,000 species of worms in the world, many of them not even named or studied. However, the farmer is interested in two main categories of earthworms, namely “deep burrowers” and “surface dwellers”. Deep burrowers include the common garden worm or Nightcrawler, (grey/pink color and about 15 cm long) and they eat soil mixed with decaying organic material. An early expert on worms was Charles Darwin, who established that earthworms process and enrich soil endlessly, and without whom, farming as we know it, would not be possible. The deep burrowers create long tunnels that go down almost 6 feet in depth, allowing deep penetration of water and oxygen. At the same time, deep burrowers bring up minerals that are incorporated into surface soil. The value of earthworms to the farmer cannot be overstated.
However, it is the surface dwelling worm, also called the composting worm, that I will concentrate on in this article. Composting is the process of decomposing and stabilizing organic material, mainly through the activity of micro-organisms along with larger decomposers, including worms. Decomposition happens naturally all around us, and by encouraging and enhancing this process, the farmer can speed up the composting process and increase the quality of the resulting organic material. Composting essentially breaks down complex compounds into simpler ones that plants can take up more easily. Composting with worms is called ‘vermicomposting’ and this produces an ideal soil amendment, full of microbes and nutrients, with excellent water retention and soil structure characteristics.
Note on nomenclature: the terms used in this field are various and there is not universal agreement as to their meaning. Here is my understanding and usage:
- Vermiculture: The intentional cultivation or rearing of earthworms and use of their ability to process organic material.
- Vermicasts/Vermicastings: The pure excrement produced by the worms, broken down from previously undegraded organic material. With some care, vermicasts can be harvested in their pure form from the top of the bin.
- Vermicomposting: Using worms to break down or ‘bio-degrade’ organic material for the purpose of creating a usable organic amendment.
- Vermicompost: The resulting mixture of pure worm castings, food remains and bedding once the bin has been harvested.
Background and History
It is thought that worms, in one form or another, have been present for up to 150 million years, so vermiculture has been happening for a considerable amount of time. But it has only been seriously studied and developed as an agricultural tool in the last 150 years. Since the advent of extremely powerful microscopes, we have access to the wondrous world of microbes. Farmers have been unknowingly applying vermicompost to their fields, mixed in with animal manure for millennia. Wherever you have a midden or dung heap, you are likely to find composting worms. Now, vermicomposting is a recognized subject and technology, and many universities include it in their curricula.
Types of Worms
There are about 6 or 7 different species of composting worms that have been ‘domesticated’ and kept for the castings that they produce. The most widely distributed worm is the Red Wiggler (Eisenia fetida), also called Brandling or Tiger worm. This type of worm is native to Europe but is now found in worm farms all round the world. However, it is not so common in the wild in southeast Asia. Our native worm in Myanmar and everywhere between India and Malaysia is the Malaysian Blue worm (Perionyx excavatus) also called the Indian Blue worm. The second composting worm in Myanmar is the African Nightcrawler (Eudrilus eugeniae). As the name suggests, this worm is not native but was brought here, likely by NGO’s and government projects. I keep both the Malaysian Blues and the African Nightcrawlers, and there are big differences between them.
Malaysian Blues: These native worms are commonly found in piles of
cow manure, which is one of their favorite foods. They are 8 cm to 15 cm long and a dark red/brown color. A distinguishing feature is that when exposed to light, their head exhibits a translucent blue sheen (Figure 1). They are a very active worm, often thrashing wildly when touched or exposed to light. The Malaysian Blue reproduces prolifically and can quickly process large amounts of organic material. Then, why is it not the No. 1 composting worm in the world? Well, it does have one major drawback, which is its wandering nature. If living conditions are not to their liking or there is a thunderstorm, they are likely to try to escape, even if it means dying in such an attempt. Last year, I lost thousands of Malaysian Blues from my indoor worm farm during the rainy season. We don’t fully understand this behavior, but it has forced me to give up keeping Malaysian Blues indoors. Luckily, they thrive outdoors!
African Nightcrawlers: These imported worms generally have to be
purchased, and the going rate here is 100Kyats (7 cents US) per adult worm. You need at least 200 to get started. The African Night crawler is a much larger, more muscular worm, growing up to 15 cm in length and it also exhibits the distinctive blue sheen when exposed to light (Figure 2). However, it does not have the wanderlust of its Malaysian brother and indeed has a tranquil personality, preferring to laze about on the surface of the food. Thus, I am making a change for rainy season this year, where the Malaysian Blues will be kept in outdoor manure piles and the African Nightcrawlers will be kept in purpose-built worm bins indoors.
Preferred Growing Conditions
Composting worms are tough creatures, and can survive less than optimal surroundings, but to thrive, they need specific conditions, as follows:
Temperature: Composting worms will thrive between 15 and 25 degrees C (59-77 degrees F) but may die if exposed to extreme heat or cold. My Malaysians and Africans, both being tropical worms, are most comfortable at the higher end of that range. One way to ensure happy worms is to have a pile large enough for them to seek out the temperature that suits them best. In winter time with reduced temperatures, worm activity — eating, excreting, and reproducing — will slow down markedly but will pick up again when the weather warms.
Moisture: Worms need moist conditions, about 80% by weight, where the bedding feels like a wrung-out sponge. Squeeze it and one or two drops of water should come out, no more. Glistening skin on the worms is a sign of correct moisture. One mistake that beginners often make is to let the worm bin become anaerobic, or oxygen deficient, through lack of drainage. Much of the worm food will have a high water content, but even so, daily spraying is required in hot conditions.
Aeration: Worms ‘breathe’ through their skin and the composting process releases other gases that must be allowed to escape, so plenty of aeration is required. Remember, you are trying to create ideal conditions for the worms and the host of bacteria, fungi, and other decomposing creatures that inhabit the worm bin.
Food: Composting worms can eat almost any kind of decaying organic matter: kitchen scraps, agricultural waste, dead leaves, or animal manure, etc. Again, we must think along the thrive vs. survive continuum; are the worms thriving or just barely surviving? To get good consistent, high quality worm castings, one should provide good, consistent, high quality food. This takes more time, effort, and investment. Foods that worms dislike include: citrus, strong tasting vegetables/spices like onions and chili peppers, meat, dairy, and oily foods. It is easy to observe when they avoid certain foods and quickly consume others (i.e. pumpkins, soft fruits, etc.). One important condition is that the food should be pre-composted to some degree. A large serving of fresh vegetables is likely to start composting thermophilically, producing intolerably high temperatures for the worms. It is possible for it to even go anaerobic, due to the high moisture content, producing foul-smelling black sludge. Food should be pre-composted, chopped fine and added only 1 or 2 inches deep. Overfeeding is usually more of a problem than underfeeding.
Bedding: When setting up your compost bin, you should place at least 15 cm of bedding material to provide the worms with a suitable habitat. I use compost that is at least one year old, but other choices are aged manure, coconut coir, or peat. Peat is not sustainably harvested in Myanmar, so I mention it only as example of the material structure that we are looking for. The bedding should be porous with good drainage. Later on, the food itself can also act as bedding. I feed chopped banana stalks mixed with cow manure, which is food and bedding in one.
Light: Composting worms cannot take exposure to strong light. Their skin is very light-sensitive, and if exposed, they dive down into the bedding immediately, the Malaysian Blues thrashing wildly as they do so.
Benefits and Harvesting Methods of Vermicasts
Worms can break down organic material very rapidly, resulting in a stable vermicompost with a better structure, microbial content, and more available nutrients than thermophilic composts. Other benefits include enhanced water retention, improved root growth, and superior cation exchange capacity (CEC). In short, vermicompost may just be the best natural, organic soil amendment that the farmer can use.
Vermicompost is most useful in a potting mix when added at around 20% by volume. A small handful can also be deposited at the bottom of the hole when transplanting seedlings. This gives new plants a good start in life, promoting stronger roots and improved disease resistance. For established plants, adding a top dressing of vermicompost will add fertility, retain moisture and generally improve soil condition on an on-going basis. Making vermicompost tea is another effective way of using your castings. My simple method is to place 5-10 handfuls of vermicompost in a strainer bag inside a 5 gallon bucket full of water, along with 6 bubbler stones connected to 3 small aquarium air pumps. I add 1 teaspoon of molasses and 2 teaspoons of EM (effective microorganisms) and leave it bubbling for 24-48 hours. The resulting tea is teeming with microbes and should be used within the first 12 hours. It can be used as a foliar spray or soil drench with a watering can. We find that it really helps plants that are fighting disease or struggling to get started.
There are several harvesting methods to choose from:
The Light Method: Dump the finished vermicompost on a flat surface exposed to strong light. The worms will immediately burrow down to get away from the light. After 10 minutes, scoop off the top level of worm-free castings. Continue this process until only the worms are left.
The Migration Method: This can be horizontal or vertical. Stop feeding the worms for 2 weeks, then add food to the top or one side of the bin. The hungry worms will migrate to the food, leaving the rest of the bin relatively worm-free. I use an especially enticing mixture of boiled and pureed potatoes, sweet potatoes, and carrots.
There are also the Continuous Flow Through Method and Pile Method that I use, which I go more into detail below.
Overview of Our Vermicomposting Systems
Vermicomposting can be done at any scale, from the smallest, using kitchen scraps, to the largest, using pre-composted manure moved around by front-loaders. The worm bin can be made of plastic, wood, concrete or even water-proof fabric. There are many websites and online videos that can provide more detail, but I would like to quickly describe the two systems that we use on our farm here in Myanmar.
The Continuous Flow Through (CFT) Method: The principle of operation is that you have a container open at the top and the bottom, although the bottom is kept closed until you are ready to harvest. Food is added through the top in 3 to 6 cm layers. After 3 to 6 months, the casting can be harvested from below, leaving most of the worms undisturbed in the middle section of the bin.
I have made these systems from cordura-like backpack material, 200L oil drums, and metal or wood structures sheathed with plywood and flat metal roofing. I get the cordura-like fabric bags sewn up by a local tailor, according to my specifications. Simply, the bag is made of 4 tapering panels sewn together to make a conical shape (Figure 3, page 3). The dimensions are shown in the diagram on page 3 (Figure 4). This fabric has the dual advantages of being water-resistant yet still breathable. I have used these bags a lot during my learning process, as they give instant access for monitoring the worms and for showing them to visiting students. They are also easy to harvest from below, or when using the Migration system with especially attractive food.
A larger and more robust CFT bin is made from a used 200L oil drum (Figure 5). I cut the top off and also cut a hole 30cm x 45cm near the remaining base. Just above this hole I drill 7 smaller holes to accept
25mm galvanized pipes which have screws drilled into them (Figure 6). This set-up of pipes and screws with 3 or 4 sheets of cardboard laid on top provides the “floor” upon which I lay 15 cm of bedding and the then the worms, and lastly the food. I finally top off all my bins with another layer of cardboard as well as a jute or hessian sack. It takes about 3 months for the worms to eat the cardboard and leave enough castings to form a solid layer at the bottom. After 6 months, when the bin is almost full, the castings are harvested by turning the blue handles on the pipes, which scrapes off the bottom-most 50mm of dried castings without disturbing the worms at the top enjoying the food. Once these systems get going, they require less work and provide a regular supply of castings.
The Pile Method: This is done simply using a pile of cow manure or other pre-composted material, on the ground, surrounded by a hoop of mesh or bamboo (Figure 7). As long as food is added regularly and the pile is protected from the sun and the rain, native Malaysian Blue worms will arrive by themselves and produce great castings which can be harvested in about 6 months. If they decide to leave during a rainstorm, they will most likely return, because this pile has the best food in the neighbourhood.
Vermicomposting is a powerful tool that the farmer can harness to improve the structure and fertility of his/her soil. It is cheap and scalable. Even when the farmer sleeps, the worms are working hard to produce the best quality natural soil amendment. As consumer concern rises about food safety and health, the market for organically grown crops will only increase. On the large scale, vermicomposting can help societies manage organic solid waste and get a valuable by-product. I urge readers to reconsider the lowly earthworm and his works. It just could be that he is man’s other best friend!
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Berkelaar, D. 2009. Income and Other Benefits from Using Worms to Make Compost. ECHO Development Notes. 104:1-6. https://www.echocommunity.org/en/resources/28a1cd54-b295-4d67-98e6-7fd38d5a05cf
Edwards, C. A., N. Q. Arancon., R. L. Sherman. 2010. Vermiculture Technology Earthworms, Organic Wastes, and Environmental Management.
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