Disadvantages Worm Castings: Uses, Benefits and Drawbacks

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Last Updated on March 2, 2023

Worms, especially earthworms, have proven to be more useful to human lives when we started acknowledging their contributions through their environmental and commercial applications. 

Through time and research, many technologies have been developed involving our humble ally – worms – like vermi meal production, vermiculture, vermicomposting, and more. But one of the most interesting discoveries about worms is worm casting. 

To understand it better, we have put together below the definition, uses, and disadvantages of worm castings, along with other useful information related to this topic.

What is Worm Casting?

Worm casting is the organic waste that went out the rear end of an earthworm – yes, it’s basically worm poop. But if you want the official scientific jargon, you can refer to it as a “fecal nugget”. It is mostly used as fertilizer because of its rich nutritional content. 

Some people call it the multivitamins for plants because worm castings are often described as the most potent manure there ever was. Here are some of the nutrients you can find in worm castings aside from the main nutrients your plants need: phosphorus, nitrogen, zinc, iron, potassium, and concentrated nitrates.

Like in the human body, worm castings consist of good bacteria, and their microbial activity is 20 times greater than their digested soil which effectively supports plant growth.

With its remarkable versatility in vitamins and minerals, you can substitute any nutritional gap you would have in growing any kind of plant you want. The best part is, all the nutrients your plant needs will be consumed immediately as it is water-soluble. 

If you have a business that would require a lot of worm castings, there is no need to fret as there are already worm castings out in the market because people actually thought they could grow a business using worms, and they’re absolutely right!

Read more about Worms in Compost: Are they a Friend or a Foe?

Worm Casting vs. Vermicomposting

Worm casting and vermicomposting are often confused as one thing, but technically speaking, they are two related, but different things. 

Vermicomposting is how worms help in reducing waste along with other organic wastes (leftover food and composted bedding) and vermicompost is the product of this worm compost system. You know you’ve found high-quality vermicompost when it contains a high percentage of worm castings. 

This particular way of composting is very trendy in urban areas these days as it can easily be done even in the comfort of your own home. You can even find a composting bin just big enough to fit under your kitchen sink.

To cut it short, worm castings are pure worm poop while vermicompost cannot exist without worm castings and contains other composted materials. They are both very rich in nutrients and are used to help your plants grow healthy.

worm casting

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Uses of Worm Casting

We have listed below some of the most known common uses of worm casting:

  • Seed germination

When you mix worm castings with your seed starter it provides the nutrients for new seedlings that boost growth. The new soil mix will hold moisture around the young seedlings providing added protection.

When it’s time to transplant your plants, you may add a cup of worm casting into the soil which would protect them from different diseases for a long time.

  • Side dressing

You can choose to either dig deeper or sprinkle this natural fertilizer around your plant. You don’t have to worry about the exact amount because your plant won’t suffer even if you use too much. 

If you’re planning on using it for outdoor plants, we suggest putting a handful on all sides of the base and then watering it. This would greatly prevent pests from bringing trouble to your plants. Now for indoor plants, you can use 2-3 tablespoons, depending on size.

  • Lawn conditioning

When you use soil for so long, it tends to lose its potency and become barren and it’s your responsibility to rejuvenate it. Adding worm castings is the finest choice as it would greatly help bring back the previous health of your soil. 

Worm castings prevent soil from drying out as it makes your soil more absorbent, consistently making moisture available to your plants.

  • Liquid fertilizer

Commonly known as “worm-casting tea” but this is definitely not for human consumption. This tea can be diluted with water and you can use it as an alternative for watering your plants. Just steep some worm castings in water like you would when making your own tea to drink.

Strengths and Weaknesses of Worm Casting

As we all know, “there’s always two sides to a coin” so if there are advantages to using worm castings, there are also disadvantages and we have listed both below for you.


  • Plant superfood – the most obvious advantage of worm casting is its nutrient-packed quality.
  • Neutral level of pH – this controls your soil’s acidic condition.
  • Protection – worm castings extract harmful toxins, bad bacteria, and fungi; at the same time containing good bacteria and beneficial microbes which help prevent diseases for your plant. 
  • Natural pest repellent – some pests such as scale insects, aphids, spider mites, and the like do not like the fecal nugget of worms so they avoid it.
  • Additional worms for your soil – some worm eggs may be left in your castings, so when those eggs hatch, they will be a great addition to your garden. Worms help break down even heavy metal deposits in your soil making it metal-free and healthy!

Read more about Organic Solution Premium Worm Castings: Natural Nutrient for Plants 


  • You will need more fertilizers – worm casting is not enough fertilizer for other plants, especially for some that require macronutrients.
  • Not suitable for acid-loving plants – acidic plants would not do well in a neutral pH range.
  • It takes time – some casting may take months before it can be used because as we all know, worms are not that big so it takes them a while to produce enough casting.

Basics of Worm Casting: Uses, Benefits and Drawbacks

How Long Does it Take For Worm Castings to Work?

Several factors influence how long it takes for worm castings to work. This includes the type of plants you grow, the soil condition, the application rate, and the method you follow. It can take a few weeks to months before worm castings begin to work. 

How Often Should I Harvest Worm Castings?

If you have a worm bin or compost bin where you raise worms, you can harvest their castings on an ongoing basis as needed. 

To harvest worm castings, remove the top layer of bedding and compost material from the bin and set it aside. The castings will be in the lower layers. You can then mix the castings into your soil or use them as a top dressing on top of the soil around your plants. 

You should try to harvest worm castings every few weeks. As the worms consume the organic matter in the bin, they produce more castings. You’ll have castings available every month. 

What is the Ph Level Of Worm Castings?

The pH. of worm castings varies. How acidic they depend on the type of organic materials the worms feed on and the conditions in the worm bin. Generally, worm castings have a neutral to slightly alkaline pH, typically in the range of 6.5-7.5.

It is important to note that the pH of worm castings can be affected by the pH of the materials that the worms were fed, as well as the pH of the water used to moisten the bedding in the worm bin. The pH of worm castings can also be affected by the conditions in the worm bin, including the temperature, moisture level, and ventilation. If the conditions in the worm bin are not optimal, the pH of the castings may be lower or higher than the typical range.

Worm casting is a good source of nutrients for plants. They can also help improve the structure and fertility of the soil. However, if the pH of the worm castings is significantly different from the optimal pH of your plants, you might have to adjust the pH of your soil before using the castings. You can add sulfur or lime to lower or raise the Ph.

Are There Nematodes in Worm Castings?

Nematodes are tiny, thread-like worms found in soil and can be beneficial or harmful to plants, depending on the species. Some nematodes are predatory and can help control pest populations, while others are plant-parasitic and can cause damage to plants.

Worm castings may contain nematodes. These are common in soil and can be present in the organic materials fed to worms. If your worm castings include nematodes, it is unlikely that you have reason to worry. 

What Vegetables Like Worm Castings?

Worm castings are a rich source of nutrients and beneficial microbes that can help improve soil health and plant growth. Many veggies will benefit if you add worm castings to their growing environment. These include:

  • Leafy greens like lettuce, spinach, and kale
  • Cruciferous vegetables, like broccoli, cabbage, and brussels sprouts
  • Root vegetables, like carrots, beets, and radishes
  • Solanaceous vegetables, like tomatoes, peppers, and eggplants
  • Legumes, like beans and peas

You should use worm castings in moderation. They can be high in nutrients and may cause damage when applied in excess. I recommend not using more than 10-20% worm castings by volume in your soil mix. 

Worm Casting Benefits

When it comes to worm castings, there are many benefits to using them at any point during the growing season. In simple terms, it can help your plants to grow better, improve the retention of water to keep your plants moist, and also protect your plants from any unwanted diseases. Let’s take a more in-depth look at just a few benefits of worm castings.

  • Helps Water Retention. Think of worm castings like a sponge. If you’re looking for an easy way to keep your plants and soil moist, worm castings are the way.
  • Helps to Reduce Erosion. As worm castings are so great at holding water, this also significantly lowers the chances of soil erosion.
  • Improves the CEC. The higher this is, the higher the fertility of your soil.
  • Easy Way to Give Nutrients. It can be tricky to ensure your plants receive the correct amount of nutrients, in an accessible way; but worm castings provide just that.
  • Helps pH Levels. As their pH level is neutral, they can help to make your soil either more neutral or more acidic; depending on what you’re looking for.
  • Aids Structure. Helps to strengthen soils that can be tricky to work with, such as clay or sand.

This is only a small selection of ways worm castings can help your plants and soil, but the list is endless!

Worm Casting Sifter – Which Size is Best?

One of the handiest tools when working with worm castings is a worm-casting sifter. As well as worm castings, it can work with other things in your garden, such as compost. Just like a sieve, it helps to separate products. The size of your sifter depends on what size worms you’re working with. For example, adult worms will need a sifter that’s at least 1/4 inch. However, if you’re using baby worms, you’ll only need around 1/8 inch sifter.

What Color Should Castings Be: Black Worm Castings

You may be wondering what the optimal color of your worm castings should be. The truth is, they should be small, and resemble small footballs. The color should be a deep black. The darker the castings are, the richer the nutrients will be for your plants and soil.

Can You Use Worm Castings and Fertilizer Together?

Of course! It’s suggested that you use them together. They are two different products, that provide different benefits to your plants and soil. Worm castings are mainly used to benefit your soil, while the fertilizer is mainly used on your plants themselves to ensure they have the nutrients they need.

Are Worm Castings Good For Succulents?

Worm castings are perfect for many plants; one of which being succulents. They are very versatile and can be used for many plants. They’re filled with goodness that will aid your succulent plants to grow.

Can I Use Worm Castings During Flowering?

As mentioned, worm castings are extremely versatile. For this reason, they can be used at any point of growth. Whether you want to use them before flowering, or during; you can do so with ease. Whatever the season, whatever the time of year, you can add worm castings to your plants and soil.

How Do You Start a Worm Casting Farm?

Starting a worm-casting farm can be a fun way to produce a valuable soil amendment and reduce waste simultaneously. Here are the basic steps for creating a worm-casting farm:

Materials you’ll need:

  • Worms
  • Worm or compost bins
  • Bedding materials (shredded newspaper, straw, coconut coir)
  • Worm food (kitchen scraps)

Follow these steps:

  1. Set up your worm bin in a cool location that’s out of direct sunlight.
  2. Place a layer of bedding material in the bottom container and add your worms.
  3. Add a layer of food on top of the bedding and cover it with another layer of bedding. Keep the bedding moist.
  4. Ensure the temperature in your worm bin is between 55-77°F (13-25°C). This will keep the worms healthy. 
  5. Add food to the bin as needed. You should also turn the bedding and food once or twice a week to provide oxygen to the materials. 
  6. In a few weeks, there will be worm castings to harvest. You can harvest the castings by scooping them out of the bin.

You can use the worm castings in your garden or sell them to others. 

Conclusion: Advantages and Disadvantages Worm Castings

To wrap this up, worm casting truly is one of the most amazing products of nature. It has very easy procedures that produce excellent results. Though there are a few drawbacks when it comes to worm casting, there are more than enough benefits to balance it out.

With that, we hope you have a finer understanding regarding worm casting through this article, enough to help you start your next gardening project. Do you have any tips or tricks when it comes to working with worm castings? If so, please feel free to let me know in the comments below. And remember, sharing is caring! 


How often should I use worm castings?

You can use worm casting on the top of your soil every month and all through the growing season. Reapplying worm casting monthly to your topsoil will keep your plants looking healthy and exceptional.

Use 0.6ml per 6 inches of worm casting of the container diameter and mix the casting inside your potted plants’ soil. Or you can simply sprinkle 1, 2, or 3 tablespoons of worm casting all over the stem of your potted plants. Water them well after doing this. If you unknowingly applied a bit of extra worm casting, do not worry. It won’t burn or distress your plant.

Is worm casting better than compost?

There is not much difference between worm casting and composting. However, worm casting has more nutrients than compost coupled with a refined and enhanced profile that aids aeration and soil moisture.

Therefore, they are a great option for small-scale vegetable gardens because of their high-level nutrient contents. Also, worm compost is pretty expensive to buy in comparison to compost and several soil additives. In addition, it is not so easy making worm casting by oneself, unlike compost.

On the other hand, compost as well contains organic matter that has decomposed into rich humus. But its nutrients are not as rich as worm casting. Compost is affordable and easy to make by yourself therefore you can get compost for free.

Can you use too many worm castings?

You should not use too much worm casting, always use the right amount. This way, the nutrient levels provided by worm casting will not be too much. However, using a little extra worm casting will not harm or burn your plants, unlike chemical fertilizers. This is because worm casting is mainly organic.

How long do worm castings last?

Although most potting soil nutrient life is about 2 to 5 days. Worm casting can last 6 times longer than most potting soil.

Also, worm casting can be stored for up to 6 months or even longer and it depends on how you store them. Storing worm casting away from ultraviolet light and a constant temperature will make them last longer.

What is the NPK of worm castings?

A survey done on worm casting shows that they are abundant in over 60 micronutrients including calcium, nitrogen, phosphorus, potassium, potash, magnesium, sulfur, and iron. Also, the NPK ratio for worm casting is 5:5:3.

The worm-casting nutrient content is higher than compost. For this reason, the rate at which worm compost is applied is lower and a single application works wonders. The worm-casting nutrient contains microbes that aid in plant disease resistance and deter harmful insects.

Worm casting is water-soluble and makes vital nutrients and trace minerals readily accessible to plants. They are purely organic making them essentially safe than chemical fertilizers.

Another great thing apart from the rich nutrient they provide, worm casting also retains moisture which is vital for plants to successfully pass through drought periods. They will as well enhance your soil structure and aeration.

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