Short answer: Vermicompost is the dark, crumbly material left after worms have eaten organic waste, and it is one of the most useful fertilisers a small Ghanaian farm can make. Keep the worm bin moist and cool, feed it in small regular amounts, and harvest the castings by separating them from the worms rather than tipping the lot. Use the castings in nursery mixes and as a side dressing, and keep them away from the birds' scratching ground.
Key takeaways
- Vermicompost is a fertiliser product made by worms, so keep the worms in conditions they can live in and the castings will follow.
- Feed in small, regular amounts, and stop feeding when the bin is wet, sour or full of uneaten food.
- Keep the bin shaded, damp and off hot concrete, and watch the temperature more than the calendar.
- Harvest by separating castings from worms, using light or a tipped bed, and save the worms for the next bin.
- Use castings as a nursery mix component and a side dressing, and brew tea only with clean water and clean equipment.
The product is the castings, and the worms are the factory
The first time most farmers see a worm bin, they expect to find a pile of soil with worms in it. What they find is a dark, crumbly material that smells of a damp forest floor and holds its shape when you squeeze it. That material is the castings, the solid waste that passes through the worm, and it is the product. The worms are the factory that makes it, and they need looking after like any other livestock.
That framing changes how you run the bin. A farmer who thinks of the worms as a pet will overfeed them and leave the bin to sour. A farmer who thinks of the castings as the output will ask how much waste goes in, how often the product comes out, and whether the quality is good enough to sell or use on the crop.
This article is about vermicompost as a fertiliser. Worms also appear in the poultry feed story, where the whole worm is dried and fed to birds, and our earthworms as a poultry feed article covers that route in full. The two uses share a worm, but they start from different goals and they are harvested in different ways.
What castings do once they reach the soil
Castings are the product of the worm's gut and of the microbes that live with it. Passing material through the worm changes its texture, breaks it into very fine particles and leaves behind a large population of bacteria and fungi. Those organisms keep working once the castings are in the soil, which is why people often describe vermicompost as a living product rather than a simple nutrient source.
The practical effects are easy to see. Castings hold water well, so a bed that has had a bucket of castings dug into it dries out more slowly after a hot day. They help the soil crumb together, which makes it easier to dig and easier for roots to push through. They also release nutrients more gradually than a dose of chemical fertiliser, which suits crops that need a steady supply rather than one big hit.
Castings are not a magic product. They are less bulky than fresh manure, and the nutrient content varies with the feed and the bin. A bin fed mostly on starchy kitchen waste will produce a different product from one fed on cattle dung and garden trimmings. If you want to know what you are putting on the field, have the material tested, as you would any other fertiliser.
Containers that breathe and drain
A worm bin needs three things from its container: air, drainage and a way to keep out light and predators. Plastic crates with holes drilled in the sides and a drain tap at the base work well for a household or a small garden. A wooden box lined with hessian or a mesh screen is common on farms where a larger volume is needed. Either way, the container should be big enough to hold a month or two of feed without becoming waterlogged.
Put the bin on a stand, not on bare concrete. Concrete heats up and holds the heat, and a worm sitting on a hot floor will try to leave. A stand also lifts the bin off the ground so that ants, rats and the odd hungry dog cannot reach the material. Keep the bin in the shade of a shelter or a wall, out of the rain, and out of the harmattan wind if the north is your location.
The drain tap is worth fitting from the start. Liquid collects at the bottom of a worm bin as the material breaks down, and if you do not have a tap, you will have to tip the bin to get it out. The liquid is a useful input, but it is also a sign of too much water, and you need to know when it is coming out.
Feeding the worms: small, regular and mostly plant-based
Worms eat in proportion to the food they can process, not to how hungry they look. Feed small amounts often, and check the last feed before you add a new one. A bin with uneaten food on top is either overfed or too wet, and it will sour quickly if you keep adding to it. A thin layer of food, mixed into the top few centimetres of material, is the target.
Plant waste is the best feed: vegetable peelings, leftover soft greens, crushed cassava peel that has been dried and chopped, and garden trimmings that are not woody. Aged cattle or goat dung works well in a small share, because it has already been partly broken down and is less likely to heat up. Shredded dry leaves, paper and cardboard add bulk and help soak up excess water.
Avoid the things that cause trouble. Citrus, onion, garlic and chilli are disliked by worms and can drive them out. Cooked food, oily food, dairy, meat and fish bring smells and flies. Salty waste should be kept out of the bin, and so should anything treated with chemicals. A rule that works well for most households is that if the waste came out of the cooking pot, it goes to the animals or the compost pit, not the worms.
Keep a simple log of what you put in each week. Note the weight, the type of material and any problem you see. Over a few months, the log tells you which feed the worms do well on and which one makes the bin sour.
Temperature, moisture and the Ghana seasons
Worms are sensitive to heat. Above about thirty degrees the bin starts to stress, and the worms move to the bottom or try to climb out. In the coastal and forest zones, the heat in the dry months can drive the temperature up quickly, so the bin needs shade, a thicker cover of dry material and watering in the cool of the evening. In the north, the harmattan brings cool nights and dry, dusty days, and the bin needs protection from the wind as well as the sun.
Moisture matters just as much. The material should feel like a wrung-out sponge: damp to the touch, with no water running out when you squeeze it. Too dry, and the worms curl up and stop feeding. Too wet, and the bin goes anaerobic and smells of sour rot. In the rains, cover the bin and check the drain tap every few days. In the dry months, water with a fine rose and keep the water off the surface crust.
A simple test for the season is the worms themselves. Lift a handful of material and look. Active worms that move away from the light and burrow down are a good sign. Worms clumped at the surface, or dying in a heap, mean something is wrong with the temperature, the moisture or the feed. Fix the cause first, because adding more feed will only make it worse.
Starting the bin with stock you can trust
Buy worms from a breeder or a trained supplier rather than digging them from a dump or a compost heap. Wild worms may not be the right species for a bin, and they bring other organisms along with them. Ask the breeder which species they supply, how old the stock is and how they were kept, and be wary of a supplier who cannot answer those questions.
Start the bin with a bed of moist bedding material, such as well-rotted dung mixed with shredded dry leaves, about 15 to 20 centimetres deep. Add the worms on top, and leave them for a day or two before you feed them. Give them time to find the bedding before you add food. A stocking that is too heavy for the bedding will stress the worms and slow the bin down.
Expect a slow first few weeks. The population grows as the food and the conditions support it, and a bin that looks quiet in the first month may be doing well underneath. Do not judge a new bin on its first harvest. Judge it on the health of the worms and the quality of the castings over a season.
Separating castings from the worms
Two methods are common. The first is the light method. Stop feeding one side of the bin for a few weeks, and feed the other side. The worms move towards the food, leaving the castings on the side you have stopped feeding. Dig the castings out from that side, leaving the worms behind, and then start feeding the empty side again. It takes patience, but it keeps the stock in the bin.
The second method is the tip-and-sort method, and it is quicker. Tip the bin onto a clean sheet or tarpaulin in a shaded spot, and build the material into a low cone. Leave it for a short period so the worms burrow to the centre away from the light. Scrape the outer castings off the cone layer by layer, and put the worms back into the bin with fresh bedding. Work in the shade, because the worms will die in strong sun.
Whichever method you use, sieve the castings before you bag them. A mesh of a few millimetres removes the bits of undigested material and the odd worm that was missed. Dry the castings in the shade rather than the sun, and store them in breathable bags, not sealed plastic, where they can heat and sour.
Keep the worms when you can. A bin that loses too many worms during harvest will take months to rebuild, and the castings will drop off as the population falls.
Worm tea, and the liquid from the drain
Worm tea is a liquid made by soaking castings in water, usually with air bubbling through the mix for a day or so. It is used as a foliar spray or as a soil drench, and many growers like it for quick feeding of seedlings and leafy crops. The liquid from the drain tap is not the same thing, and it is best used as a soil drench only, diluted with clean water, because it can be strong and it can carry bacteria from the bin.
Brew with clean water, a clean bucket and a clean stirrer. Water that has been standing in an old drum or a dirty tank can bring bacteria and algae into the tea, and some of those organisms can be a risk on food crops. Use the tea within a day, and do not store it for long. Spray tea on crops you will cook rather than eat raw, unless you have checked the water and the process with your extension officer.
The effect of tea is hard to measure on a small farm. Treat it as a useful supplement rather than a complete feed. A seedling in a bad patch of soil may respond well, and a mature crop may show little difference. Keep notes on what you spray and what you see, so you can judge it for yourself.
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Using castings in nurseries and on crops
The best use for castings on a small farm is in the nursery. A common starting point for a seedling mix is about one part castings to three parts topsoil or sand, adjusted for the crop and the soil. Mix it well, fill the bags or trays, and water it in before you sow. Seedlings raised in a mix like this tend to root well and hold together when they are transplanted, which matters more than any single nutrient figure.
In the field, castings work well as a side dressing or a planting-hole addition. Put a small handful into each planting hole for tomato, pepper, okra or leafy greens, and mix it into the soil. For a side dressing, scatter a light band along the row, keep it a little away from the stems, and water it in. Do not pile castings against the stem, because the damp material can invite rot.
Ask your agric extension officer for a rate for your crop and your district, and use that as your starting point. Castings are a fertiliser and a soil conditioner. They work best when added regularly, and a single heavy dose on a poor field will not fix years of neglect on its own.
Apply castings to dry soil or to soil that you have watered, and water the bed after application so the material settles. In the harmattan, a light cover of mulch over the bed keeps the surface from drying and blowing away.
A worked example: a household bin for a family plot
Take a family plot with a small kitchen garden and a bin fed on the household's vegetable peelings and trimmings. Suppose the household produces about one kilogram of suitable waste a day. That is an assumption, and your own kitchen will differ, so weigh a week of waste before you size the bin. Keep the feed in the bin on a regular schedule and record what you add.
| Record | What to note | Why it matters |
|---|---|---|
| Feed weight, weekly | Total kilograms of suitable waste added | Shows whether the bin is keeping pace |
| Moisture check, weekly | Squeeze test: damp, wet or dry | Catches sourness or drying before the worms suffer |
| Temperature in the heat | Shade, cover and watering pattern | Shows how the bin copes with the season |
| Castings harvested, monthly | Weight, after sieving and drying | Tells you the yield from your feed |
| Worm health | Active or clumped, count of dead worms | Gives you the earliest sign of a problem |
After three or four months, you will have a record that tells you how much the bin takes, how much it returns and where it struggles. A household that does this will know whether to add a second bin, cut back on feed or move the bin to a cooler spot. A household that does not will be guessing, and guessing with worms usually means losing them.
The castings from this bin go first to the nursery, then to the kitchen garden, and any surplus goes to a neighbour who wants to try it. Keep the excess out of the market until you have tested the product, and check current rules on selling fertiliser before you do.
Where castings sit beside the flock
Birds and worm bins do not mix well. Hens will scratch through a bin that is left open, scatter the material and eat the worms, which may please the flock but is a setback for the bin. Keep the bin fenced and covered, and keep the flock's ground separate from the bin area. If you want worms as a poultry feed, that is a separate project with its own rules, covered in our earthworm poultry feed article.
The other fertiliser routes on a mixed farm are covered in our making organic fertiliser article, which shows how castings and compost can be blended. Our composting farm waste article covers the bulk material that often feeds the worm bin in the first place. For the bird manure route, our poultry manure guide explains drying and handling.
A farm with a flock, a garden and a worm bin has plenty of uses for the waste. The task is to keep each stream clean and recorded, so that the castings do not end up mixed with bird litter or the feed bins. Our poultry record keeping article sets out simple logs that can run alongside a worm record.
New birds for the yard beside the bin? Begin with our day-old chicks range, then use the order section. Our team can be reached on WhatsApp at +233 24 915 1503. The chick prices page lists current starting prices, and the breeds page compares the birds we hatch.
A checklist for the first worm bin
Use this list before the first worms go in, and again when you harvest. Most failed bins miss one of these steps.
- Choose a container that breathes and drains, with a tap at the base.
- Place the bin on a stand, in shade, away from hot concrete and birds.
- Buy worms from a breeder who can say what species they supply.
- Start with moist bedding about 15 to 20 centimetres deep and let the worms settle.
- Feed small amounts of plant waste, and avoid citrus, onion, cooked food and oil.
- Check the moisture with the squeeze test each week, and adjust with water or dry material.
- Watch the temperature in the hot months, and keep the bin covered in the rains.
- Harvest by the light method or the tip-and-sort method, and keep the worms.
- Sieve and dry the castings in the shade, and store them in breathable bags.
- Use castings in nursery mixes and side dressings, and keep a record of every result.
Questions farmers ask
Are castings the same as ordinary compost?
They are similar in purpose but different in process. Ordinary compost is made by heat and microbes working through a heap, while vermicompost is made by worms and their microbes working through a bin at lower temperatures. Castings are usually finer, more uniform and more biologically active than a typical compost heap. Both improve soil, and both are worth making on a farm.
Which worm should I use for castings in Ghana?
Buy from a breeder who can tell you the species and how they keep it. The species matters less than the conditions you provide. Keep the bin cool, damp and shaded, and feed it properly. Ask your agric extension officer or a local breeder which stock does well in your zone and season.
How often should I harvest castings?
Harvest when the bin has a good depth of castings and the worms are healthy, which often means every few months rather than every few weeks. Use the light method or the tip-and-sort method, and do not take so much at once that the worms lose their home. A bin that is harvested too often never builds up its population.
Can I use castings on maize?
Yes, castings can be used on maize as a side dressing or a planting-hole addition, though the amount should be set for your soil and your rate with your extension officer. Maize has a large nutrient demand in the growing season, so castings alone may not meet it on a poor field. Use them alongside other fertiliser or compost as your agric officer advises.
Why are my worms leaving the bin?
Worms leave when conditions are wrong. The usual causes are heat, dryness, waterlogging or sour food. Check the temperature, the moisture and the feed, and fix the cause first. A bin with a small spill of worms is often recovering from a hot day or a heavy rain, and it will settle once conditions are right.
Can I put castings straight onto seedlings?
Mix castings into the nursery soil rather than laying them on top of seedlings. A raw dose on top can burn tender roots and invite rot in damp weather. A nursery mix with a share of castings gives a gentler, steadier supply, and seedlings raised that way tend to transplant well.
Do castings smell?
Good castings smell earthy, like a damp forest floor. A sour or rotten smell means the bin is too wet, overfed or short of air. Fix the cause before you harvest, and dry the castings in the shade if they still smell after sieving. Do not bag castings that smell sour, because they will heat and spoil in the bag.
