Worm compost: What is vermiculture and how to make homemade fertilizer

Last updated on October 23rd, 2023 at 08:19 pm

We are going to continue deepening in the topic of fertilization, dedicating today’s post to worm humus, worm compost or vermicompost. As we have already seen in other articles, there are many types of organic fertilizers that we can use to improve or fertilize the soil. Ecological fertilizers such as manures, garden compost, mushroom compost, green manures, worm compost, compost tea, liquid organic fertilizers…

Worm compost: What is vermiculture and how to make homemade fertilizer

What is worm humus and what is it used for?

Worm humus is a type of compost that is formed by worms that help decompose organic waste. Like vegetable compost, vermicompost can be made in a heap on the ground or in a “vermicompost bin”, which is what the container or composter is called in this case.

Worm compost: What is vermiculture and how to make homemade fertilizer

(If you have never heard of “compost” before, I recommend that you first read the article “Composting in the garden, a good ecological technique”).

What the worms do in the vermicompost is to accelerate the composting process (the conversion of kitchen waste and plant debris into humus). The worms feed on the materials put into the vermicompost and then excrete a humic substance that is very nutritious for plants, a compost that slowly releases nutrients and retains water quite well. In addition, the liquids or “leachates” that are formed can be collected and are also a magnificent natural liquid fertilizer.

Because of its quality, worm humus or worm compost is one of the most widely used fertilizers in organic farming.

How to make compost with worm castings or vermicompost

If you do not have room or time to create vermicompost in your own garden, you can buy it in some specialized fertilizer stores, or horticulture and gardening stores, or buy it from vermicompost producers who sell it directly to the public (many of them offer their products through the Internet, such as the company Dishumus).

If you prefer that the worm humus is produced in your own garden, the first thing you will have to do is to find a place for the worm castings: it should be a cool place (preferably in the shade) because, unlike vegetable compost, worm compost does not require high temperatures, in fact, if temperatures reach too high the worms could die.

You can buy it already assembled or make it yourself, you will only need several plastic containers, a drill and not much more…).

If you use several containers or crates, they should have holes so that the worms can pass from one to another. But you can also choose to use a single container and make different layers that the worms can pass through freely: you will only have to make a separation to create two spaces: one with all the layered materials and another one for the collection of the leachates. Here is an example:

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What are the needs and characteristics of earthworm composting?

To make earthworm humus it is very important to build the right habitat for earthworms. For them to make good worm compost it is very important that they are comfortable and can live and feed well. To do this:

  • You must create a good “bed or bedding” with fibrous materials such as cardboard strips, paper, straw, dry grass, coconut fiber, sawdust….
  • You will introduce on it a layer with soil or vegetable compost and earthworms (now we see which ones).
  • Every few days, you will have to add what will be the food of the worms: organic remains of the garden, remains of fruit, vegetables, bread, eggshells and other remains of our food (if you chop them up or crumble them the worms will eat them faster, they will grow and reproduce more and the vermicompost will be formed before).
  • Do not introduce: meat, fish, fat or oil, dairy products or too much citrus (because they acidify too much).
  • Do not add more food than necessary. If the vermicomposter starts to smell too bad it may be because the worms do not have time to decompose everything in it and it rots… If this happens or if you see that there are still food remains without decomposing, wait a few days to add more remains to the composter.
  • You will need to keep the composter moist and cool so that the worms are comfortable and don’t leave: spray or sprinkle water every two or three days at the most.
  • Add moist fibrous material (from the bedding) once a month or if you see that the worms are done with it.
Worm compost: What is vermiculture and how to make homemade fertilizer

What worms to use to make worm compost? 

Worms for composting can be purchased or captured in the garden. The most commonly used species is Eisenia foetida (earthworm, red worm or Red worm), but you can also buy Eisenia hortensis.

Preparing the pre-compost

As we have already seen, the first thing to do is to prepare this product, which we call “precompost” (in this case, crop residues and rabbit and chicken droppings that are transformed into compost in the large strings of the ETSIA composting plant). This is very important because it is necessary to incorporate organic materials into the earthworms’ habitat so that, in return, they produce the vermicompost.

Once the precompost is ready, we can give it to the worms and, with proper care and management, they will produce the compost we expect.
How do worms make compost?

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When the worms feed on the “food” we provide them with, processes of fractionation, synthesis and enzymatic and microbial enrichment occur in their intestine; in other words,: as it passes through their intestine, the waste is “loaded” with compounds and beneficial microorganisms that favor its decomposition even more. 

The consequence? The waste product excreted by the worms, worm humus, worm compost or vermicompost, is an organic product capable of stabilizing faster than normal compost. The product is more decomposed and, therefore, the transformation of humus into mineral substances, which is what plants really need and absorb, is faster.

Vermicompost ridges

To form the ridges or ridges of compost + worms + vermicompost that you see in the photo, the first thing was to spread a protective surface on the soil to isolate them from the soil and weeds. For this we used geotextile anti-weed netting (specifically the HORSOL BIO anti-weed netting).

On top of the protective nets, two ridges were made with the precompost and with the earthworms we talked about in the previous post.

For a few months we waited for this worm population to multiply so that we could make more ridges without having to buy more worms.

Meanwhile, they were already doing their job by eating and digesting their “food” to make vermicompost.

Worm compost: What is vermiculture and how to make homemade fertilizer
Worm castings and vermicompost in process covered with straw

How to multiply the number of worms

Worms only need food and comfort to reproduce non-stop and exponentially. In fact, it is not uncommon to dig a little in the ridges and find, besides earthworms, eggs like these that I photographed when I visited the vermicomposting plant of the ETSIA: oval, yellowish in color and a few millimeters.

To achieve the maximum reproduction rate of earthworms, the habitat we have created for them must be at a humidity of 80% or so and at the optimum temperature: 20 to 25 º (below that temperature they also reproduce, but at a slower rate).

If it is cold and they are outside, to maintain the right temperature we can try to insulate a little the ridges or where we have the vermicompost. In Agronomos this is what they have done during the cold winter months, so you can see in the photo above a layer of straw covering the ridges (in late spring they remove it). Although the straw is a bit of a nuisance, the worms will reproduce more if we use this simple method.

The humidity must also be adequate, so the ridges have sprinklers to keep them moist.

It is also very important to renew their “food” since after a few weeks they will have digested most of what we put in them at the beginning. That is why, according to what the people in charge of making vermicompost in Agrónomos told me, every 2-3 months they add new precompost to the ridges (about 20 cm high along the ridges), having previously removed the vermicompost already made (now I will tell you how).

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What to do with the worms and the finished vermicompost

When the population grows a lot, the worms stop reproducing: they “detect” that there is little room and little food for all of them and start to reproduce at a much lower rate. If we remove half of the worms, they will have more room, eat more and reproduce again at a higher rate. In addition, with the ones we remove, we can make another ridge and obtain double the amount of worm compost.

For this reason, and because it is necessary to remove the finished vermicompost, is why they use this technique of “cheating the worms”:

We say they “trick” them because they put a kind of “bait” for them to go towards it so they can capture them. The bait is a string of precompost “fresh from the oven” (i.e., from the precomposting plant) that is placed on top of the ridges. Fresh and appetizing food for them, and above all… free! because they have just brought it and it does not have any worm yet.

The worms will climb towards the new cordon.  When they have done so, it will be time to remove them from the “trap” and also to remove the finished vermicompost they leave underneath. The worms will be distributed between the ridge they were in and a new one, so that…in a while, we will do the same operation and get twice as much worm compost! (Take note, this is a very good way to multiply worms!)

I hope these little tricks that I was told have been useful to make vermicompost in the garden 🙂


  • James Jones

    Meet James Jones, a passionate gardening writer whose words bloom with the wisdom of an experienced horticulturist. With a deep-rooted love for all things green, James has dedicated his life to sharing the art and science of gardening with the world. James's words have found their way into countless publications, and his gardening insights have inspired a new generation of green thumbs. His commitment to sustainability and environmental stewardship shines through in every article he crafts.