Disadvantages of worm castings

Worms castings, let’s be honest, they look pretty disgusting. Having said that, they have a wealth of benefits from being organic, they add nutrients to your soil and help your plants to grow. However, you’re not here for the advantages, are you? You want to know about the disadvantages of worm castings and I’ve got plenty for you:

Disadvantages of worm castings snippet image

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Disadvantages worm castings

Making your own worm castings at home is time-consuming. If you only have a small worm farm, it could take around 6 months to harvest enough castings for your garden. If you don’t want to harvest your own, you have the option of purchasing them, however, they are rather expensive in comparison to other natural fertilizers. Let’s briefly touch on some more disadvantages:

  • It’s a time-consuming process
  • they can be expensive to buy
  • Not as effective as other fertilizers
  • Disturbs worm’s natural habitat

What are worm castings?

Worm castings are the end result of the process of digestion and absorption of organic matter by earthworms (yes worm poop). Some people refer to it as a combination of vitamins for plants because worm castings are frequently described as the most powerful manure ever.

Aside from the essential elements your plants require, you’ll find phosphorus, nitrogen, zinc, iron, potassium, and concentrated nitrates in worm castings. Worm castings, like our bodies, contain beneficial bacteria and host a 20 times greater bacterial activity than digested soil, which aids plant development.

Pure worm castings are readily available on the market and interestingly enough, people have grown successful businesses catering to this specific need. Just when you think you couldn’t hear anything stranger, people are selling worm poo… and thank the lord they do!

If you want to learn about types of worms in potted soil then feel free to read an article I wrote that covers this.

create quality worm castings



Having your own worm farm and waiting for worm castings to appear is a time-consuming process if you’re doing it at home. To put it into perspective, it will take you at least 6 months to get a bucket full! That’s a lot of waiting for very little return!

Larger commercial worm farms where they can hold many layers of composting worms can churn out a lot of castings in comparison to the smaller home farms. This is due to the increased surface area where they can feast and defecate. More worms, more poop, more poop, more yield… simple!

To help the worms eat faster, add more levels to your worm bin. The worms will climb the worm tower in order to access fresh food. When you add layers, I always discover that worms survive on all levels. This indicates that the worms can continue breaking down organic matter and food over a larger surface area, speeding up the process.

Worm activity in the winter is considerably slower due to the colder temperatures. This can result in a drastic reduction or even complete stoppage in castings production until the weather warms up again. You’ll have to be patient and wait for springtime if you want to see a return on your investment.

Wheelie bins are great for larger-scale worm farming because they are easy to keep warm in the winter and have a larger surface area. By using a wheelie bin, you can continue to produce castings all year round without any weather-related interruptions.

food scraps


Worm castings can be expensive, especially if you’re purchasing them from a store. A 1lb bag of quality worm castings costs around $15 and a 2lb bag costs $25.

To put that into perspective, you could buy a 40lb bag of manure for the same price as 4lbs of worm castings. Composting is also an option and is more affordable than purchasing worm castings.

The advantages of using Worm Castings might far outweigh the expense. Worm Castings also aid in the aeration and drainage of your garden soil, making them an essential instrument for growers aiming to grow large amounts of robust plants.

worm casting


Worm castings are not as effective as other fertilizers. This means that if you’re looking to scale up your production, you’ll need to use more worm castings in order to achieve the same results.

The application rate for worm castings is 15-20lb per 100 square feet. This is considerably higher than other organic fertilizers such as manure, which has an application rate of 15lbs per 100 square feet.

If you’re using worm castings as a top dressing, you’ll need to apply them at a rate of 1/4″ – 1/2″. For reference, a cup of dry worm castings weighs approximately 0.5lbs. This means that you would need 4 cups of worm castings to top dress a 100-square-foot garden.

soil amendment

Disturbs worms

The process of obtaining castings from your worm farm will always disturb your worms. Even if you’re careful, getting the castings out is difficult at best. The eggs and larvae may be harmed when they are extracted because they contain a high concentration of nitrogen.

Worms are also very sensitive to light, sound, and vibration. When you disturb their home, it can cause them to go into shock and die. If you’re not careful, you could end up killing a large portion of your farm.

plant and animal pathogens

Temperature changes

To ensure the survival of your worms, keep them away from extremes in temperature and humidity. Worms are, after all, still living creatures. If it’s too hot or too cold, they will die.

The ideal temperature for worms is between 55-77 degrees Fahrenheit. If the temperature gets too high, the worms will start to migrate to the surface in search of cooler air. If it gets too cold, they will go into hibernation.

Worms are also very sensitive to moisture. Too much moisture will cause them to drown while too little will cause them to dehydrate and die. The ideal moisture level for worms is between 60-80%.

To maintain these optimal conditions, you’ll need to monitor the temperature and humidity of your worm farm carefully. This can be difficult, especially if you’re using an outdoor bin.

It’s not as effective as other fertilizers

Worm castings are not as effective as other types of fertilizers because they are not as concentrated. This means that you’ll need to use more worm castings in order to achieve the same results as you would with other fertilizers.

The amount of macronutrients is limited also because earthworms don’t have the ability to break down complex molecules. This means that the nitrogen, phosphorus, and potassium content of worm castings is lower than other fertilizers.

Worm castings also lack micronutrients such as calcium, magnesium, and sulfur. These are essential for plant growth but must be supplied by other means. So you may want to take this into consideration when comparing a natural organic fertilizer to chemical fertilizers.

potting soil

How to collect your worm castings

Method 1 – Scraping method

The most basic approach is to remove the worm lid and blanket. Then use a rake or shovel to gently scrape off the top layers. The worms will dig down to the lower levels of the castings, and you may remove it over time from the top.

It takes time to scrape and remove the next layer of castings. If you do this operation carefully, you can remove up to 2/3 of the worm castings. Always provide fresh bedding, such as dead grass, hay, or dead leaves for the worms to eat and break down, especially if your pets are confined outside often.

Method 2 – Tip and Scrape

This is a variation of the first method, but you do not need to remove the entire worm lid. You can simply tip the bin on its side and harvest worm castings that have been collected on one side. Then rotate the bin so that the other side is exposed and repeat the process.

With this method, you can collect a larger amount of castings in a shorter period of time. However, you will need to be careful not to damage or disturb the worms too much.

Method 3 – Layers of tiered worm farms

Tiered worm farms make castings removal a lot easier. After the bottom layer has been filled, replace the lid and move it to the top level. The worms will descend to the bottom level and exit through the lower entrance.

I’ve done this a lot, but I’m always left with worms in the layer. To return any remaining worms to the worm farm, I’ll always take a spade and scrape the worm castings and remove any remaining worms and place them back into the worm farm.


So let’s summarise what we have learnt and the disadvantages of worm castings:

  • Earthworm castings are the final product of earthworms’ digestion and absorption of organic waste that can contain beneficial nutrients

  • It takes time to collect worm castings (up to 6 months to collect a bucket’s worth

  • They are expensive to purchase in comparison to other natural fertilizers

  • You’ll need to use a lot more worm castings to cover the same area in comparison to other fertilizers

  • You disturb worms’ natural habitat by collecting worm castings

  • You need to keep an eye on temperature changes as this can have a negative effect on your worms

  • There are three main ways to collect worm casts: Scraping method, Tip and Scrape method and Tiered Worm method

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Oliver Wright

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