Basics of Worm Casting: Uses, Benefits and Drawbacks

Last Updated on January 7, 2021 by admin

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 vermimeal 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 worm castings, along with other useful information related to this topic.

What is Worm Casting
Basics of Worm Casting: Uses, Benef...
Basics of Worm Casting: Uses, Benefits and Drawbacks

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 its 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, 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.

Best compost products suppliers on the market today 

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 provide protection 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 as to the exact amount because your plant won’t suffer at all 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 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 of a coin” so if there are advantages for using worm castings, there are also disadvantages which we both listed 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 helps prevent diseases for your plant. 
  • Natural pest repellent – some pests such as scale insects, aphids, spider mites, and the likes 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, it 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 in size so it takes them a while to produce enough casting.

Basics of Worm Casting: Uses, Benefits and Drawbacks


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 had a finer understanding regarding worm casting through this article,  enough to help you start your next gardening project. 


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, not to worry. It won’t burn or distress your plant. 

Is worm casting better than compost?

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

Therefore, they are a great option for small scale vegetable garden because of their high-level nutrient contents. Also, worm compost is pretty expensive to buy than 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 much 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. 

Worm castings nutrient content- 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. 

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.