Generally, the recommended ratio of worm castings to soil is 15-20% castings to 80-85% soil or potting mix. This means that for every 1 kg of worm castings, you should use 8-9 kg of soil or potting mix. For example, if you are making a 10 kg potting mix, you would use 1.5-2 kg of worm castings and 8.5-9.5 kg of soil or potting mix.
Worm castings are a great addition to soil because they improve drainage, aeration, and water retention. They also add nutrients to the soil, making it more fertile. Worm castings, also known as vermicast or worm humus, are nutrient-rich organic fertilizers produced by earthworms.
They are often considered the black gold of gardening due to their numerous benefits for soil health and plant growth. Here we will explore the optimal application of worm castings in gardening and farming.
Everybody has a different set of questions on different segments on this topic. So Let’s get a brief
Application | Amount of Worm Castings |
Per Gallon of Soil or Potting Mix | 15-20% (1.5-2 kg per 10 kg mix) |
Per Square Foot of Garden | 1/2 to 1 pound |
When Planting New Plants | 1 to 3 tablespoons per hole |
Per Gallon of Water | 1 cup |
Per 5-Gallon Bucket (Worm Castings) | 4 to 6 cups |
Per 5-Gallon Bucket (Worm Casting Tea) | 1.5 to 2 pounds |
What Are Worm Castings?
Worm castings are the nutrient-rich excrement produced by earthworms as they digest organic matter. Earthworms, especially the red wiggler species (Eisenia fetida), are renowned for their ability to transform organic waste into a highly beneficial soil conditioner.
The digestive process in these creatures breaks down organic materials and enriches them with essential nutrients, making worm castings a valuable addition to any soil.
How Much Worm Castings Per Square Foot?
From my previous experience and research on the web and group, I found that you should put about 1/2 to 1 pound of worm castings on every square foot of your garden. This helps your plants grow nicely. You can mix the castings into the soil so they spread out well.
When you’re planting new plants, you can use 1 to 3 tablespoons of worm castings for each hole. This gives them a good start.
It’s good to add worm castings to your garden 2 to 3 times a year, in the early spring, summer, and fall.
You can also sprinkle 1/2 inch of castings on top of the soil every 2 to 3 months from spring to fall to keep your garden happy.
How Much Worm Castings Per Gallon of Water?
A good rule to remember is to use 1 cup of worm castings for every 1 gallon of water. This creates a liquid mixture that can serve as a fertilizer or leaf spray for your plants. If you’re adding other ingredients to your fertilizer or tea, the amount of worm castings may vary.
For the best results, it’s a good idea to use rain or well water. If you want to make sure the mixture is well-aerated, you can use an appropriate-sized air pump.
In simple terms, use 1 cup of worm castings for each gallon of water, and you can also use rain or well water for better results.
If you’re adding other things, you might need to adjust the amount of worm castings you use. An air pump can help keep the mixture well-oxygenated.
Ingredient | Amount per Gallon of Water |
Worm Castings | 1 cup |
Molasses | 1/3 cup |
Worm Casting Tea | 3 cups |
How Much Worm Castings Per 5 Gallon Bucket?
To use worm castings in a 5-gallon bucket, you can add about 4 to 6 cups of worm castings. That’s roughly the amount of worm castings you should put in there.
If you want to make worm-casting tea in a 5-gallon bucket, you can use around 1.5 to 2 pounds of worm castings for every 5 gallons of water.
This will help your plants get the good stuff from the worm castings when you water them.

How To Manage the Application Rate Of Worm Castings?
The appropriate application rate of worm castings largely depends on the type of plants you are cultivating and the existing condition of your soil. Here, we’ll break down the recommended application rates for different scenarios.
1. General Garden Use:
For general gardening purposes, where you want to enrich the soil and promote overall plant health, a common guideline is to use approximately 5-10% worm castings by volume. This translates to about 1/2 to 1 gallon of worm castings per 10 gallons of soil.
2. Seedlings and Transplants:
When working with delicate seedlings or transplants, it’s advisable to use a milder mixture. A 1:1 ratio of worm castings to soil is often suitable for promoting healthy root development and reducing transplant shock.
3. Container Gardening:
Container gardening often requires higher concentrations of nutrients due to the limited soil volume. You can mix worm castings with potting soil at a 10-20% ratio, depending on the specific requirements of your plants.
4. Established Garden Beds:
If you have well-established garden beds with reasonably fertile soil, using worm castings as a top dressing is an effective strategy. Spread a 1-inch layer of worm castings over the soil surface and gently work it into the top layer of the soil.
5. Vegetable Gardens:
For vegetable gardens, which benefit greatly from nutrient-rich soil, you can use up to 20% worm castings in your soil mixture. This can be especially beneficial for heavy feeders like tomatoes and peppers.
6. Houseplants:
When using worm castings for indoor plants, it’s best to blend them into the potting mix at a 10-20% ratio. This ensures steady nutrient availability for your potted plants.
When Considerations for Large-Scale Agriculture?
In large-scale agricultural operations, the quantity of worm castings required can be substantial. The optimal application rate will depend on the specific crops being grown, soil quality, and budget constraints. However, a general guideline for larger agricultural applications is to use 1-2 tons of worm castings per acre, which equates to approximately 50-100 pounds per 1,000 square feet.
Measuring by Weight vs. Volume
Some gardeners prefer measuring worm castings by weight for more precision. On average, a gallon of worm castings weighs around 8-10 pounds. This information can help you accurately gauge how much you need based on the desired application rate.
Conclusion
In conclusion, for each gallon of soil or potting mix, it is recommended to use approximately 15-20% worm castings, equivalent to 1 cup per gallon. This precise amount helps enhance soil quality, providing better drainage, aeration, and nutrient enrichment, ultimately promoting healthier and more fertile soil for your plants.
Reference:
https://www.planetnatural.com/worm-castings-benefits/ https://plumeria.care/fertilizing/worm-casting-tea-especially-great-seedlings/

I am a graduate of Bangladesh Agricultural University, where I delved into various agricultural disciplines, equipping me with a profound understanding of agriculture. Beyond academics, I have hands-on experience in gardening and crop cultivation. My passion is to embrace sustainable farming and horticulture. With a BSc in Agriculture, I am dedicated to promoting environmentally conscious and efficient agrarian practices.
Bachelor of Science (BSc) in Agriculture (Hons.)
Master of Science. (Sustainable Agriculture & Food Security ) (MS)
Bangladesh Agricultural University