How to Use Worm Castings for Tomatoes – 6 Benefits Included?

Apart from adding a bunch of nutrients to the growing medium, worm castings for tomatoes improve soil structure, soil aeration, and microbial activity. Also makes it retain moisture and enhances its draining ability.

I’m a mega fan of worm castings! Not just because it is an inexpensive way to enrich your garden soil but also because it can minimize waste.

Worm castings are packed with a wide range of nutrients that can benefit vegetables, fruits, succulents, and flowers. Basically, you can use this organic fertilizer to grow any plant.

Needless to say, adding worm castings can be a great benefit for your tomatoes.

Tomatoes are heavy feeders, and they need primary nutrients like nitrogen, phosphorus, and potassium, along with secondary nutrients.

With a 5:5:3 NPK ratio, worm castings can give a nutritional boost to your tomato plants.

Unlike chemical fertilizers, worm casting is a slow-releasing fertilizer that avoids over-fertilization.

Before you dwell on the steps to use it efficiently in your garden, let’s learn about this organic fertilizer in detail and how you can make it at home.

What is Worm Castings?

Also known as vermicastings or vermicompost, vermi means worm, and castings is the process of composting.

worm castings for tomato plants

In simple terms, it is worm poop.

But it doesn’t stink.

Red wigglers are earthworms that consume organic compounds, or kitchen scraps served to break them into organic matter.

Uncle Jim’s Worm Farm prefers to call it the “black gold”.

Not only does it add nutrients, but it significantly improves the soil’s ability to absorb nutrients.

With high levels of saturated nutrients and low levels of containment, worm castings can make your tomatoes grow bigger. (source)

The interesting thing is you can make it at home.

Serve red wigglers (prominent vermicomposters) with your kitchen scraps and leftover food. It works for you to consume and make excreta that don’t stink.

6 Benefits of Worm Castings for Tomatoes

Managing wastage and food production is a double challenge that most countries with growing populations are facing.

A study carried out that vermicomposting can partially solve this challenge.

Instead of throwing kitchen leftovers, you can recycle them to make organic fertilizer for your backyard.

meta-analysis on the effectiveness of worm castings states that vermicomposting applications can significantly help to produce larger and higher quality yields.

are worm castings good for tomatoes

1. Beneficial Microorganisms

In addition to essential nutrients, worm castings have beneficial bacteria that are important for organic gardening.

  • Bacteria help break down complex compounds to produce simple amino acids and fatty acids that the plant can easily absorb.
  • This breakdown increases humus in the soil, thus improving soil structure.
  • Microorganisms break organic matter to release nutrients and carbon dioxide into the growing medium.
  • Certain microorganisms are known to increase nitrogen levels in the soil.
  • Microbial activity improves soil aeration and drainage ability of the potting soil.

Overall, microbes are essential for the decomposition and nutrient-recycling process. You can check its importance in the soil here.

2. Slow-releasing Fertilizer

Organic compounds like worm castings gradually release nutrients into the soil.

  • It promotes uniform growth of your tomato plants.
  • Unlike synthetic fertilizers, worm castings don’t burn your plant with over-fertilization.
  • It ensures a consistent supply of nutrients for optimal growth of tomatoes.
  • Slow-releasing fertilizers allow the soil to absorb nutrients efficiently.
  • It avoids running off nutrients into storm drains.

Slow-releasing fertilizers like worm castings enhance nutrient uptake by the soil, reduce the frequency of applying fertilizers, improve soil health, and reduce the risk of nutrients running off into waterways.

3. Improves Soil Structure

Poor soil structure results in water logging, lock-up of nutrients, and anaerobism (lack of oxygen).

Adding worm castings attracts microbes, which feed on organic components in the soil to improve soil aeration.

It helps easily flow nutrients and oxygen through the roots.

Improved soil structure shows a positive impact on your tomato plants.

4. Great Source of Nutrients

Worm castings include nitrogen, phosphorus, potassium, calcium, magnesium, iron, zinc, copper, cobalt, sulfur, and manganese.

Along with these essential nutrients, worm castings provide secondary nutrients and trace minerals that significantly improve plant’s ability to absorb nutrients from the soil.

Note: the difference in NPK value is due to the manure served to red wigglers. Studies show that using cattle manure has a greater impact on the crop. If you’re using kitchen scraps, then you probably shouldn’t expect this NPK value.

Worm castings are renowned for higher nitrogen levels. However, it won’t burn your tomato plants as they are released slowly into the soil over time.

5. Helps Tomato Plant Fight Diseases

Enzymes and antibodies in worm castings inhibit soil-borne diseases and make your plant strong enough to fight other diseases.

Worm humus may benefit the soil by removing toxins and harmful bacteria from it.

Worm castings are said to release enzymes that degrade the exoskeletons of pests and insects, thus resulting in the death of insects.

Read this: How to Get Rid of Aphids and Flea Beetles?

6. Permaculture Farming

In simple terms, the main aim of permaculture farming is to avoid throwing waste and design a system that promotes sustainability.

Worm casting is the perfect process that avoids wastage and helps to convert it into organic fertilizer that, in turn, is used to make food.

As a nature lover, gardeners should prefer worm castings to fertilize their backyard rather than going out for synthetic fertilizers.

How to Use Worm Castings for Tomato Plants?

There are different ways in which you can enrich your potting soil.

The nutritional needs of tomato plants depend on their growing phases.

  • At the germination stage, seeds don’t need high levels of nutrients. Similarly, tomato seedlings have low nutritional requirements, mainly nitrogen, phosphorus, and potassium.
  • These nutrients contribute to root development and the formation of leaves and stems.
  • When the tomato plant reaches adulthood, it requires all nutrients, along with proper watering and sunlight.

So, you must determine the nutritional needs of your tomato plant before applying worm castings.

1. Adding Worm Castings to Potting Soil

Let’s say you already germinated seeds indoors and have tomato seedlings that are ready to transplant in the garden.

Prepare the potting soil mix at home by mixing 1 part of worm castings, 2 parts of garden soil, and 1 part of perlite.

These ingredients ensure the growing medium drains well and retains the required moisture.

2. Mulch around the tomato plant

Worm castings are full of humus, which is organic matter.

During the growing season, apply worm castings around the plant. It acts like mulch that releases nutrients gradually and retains the required moisture.

Mulch avoids weed growth, and it decreases the escape of moisture into the atmosphere.

Also Read: Can I Spray Soapy Water on My Tomato Plants?

3. Compost Tea

You can make a liquid fertilizer out of worm compost tea by steeping it in water.

It is filled with nutrients, beneficial microorganisms, and enzymes that deter pests and enhance overall soil health.

As the nutrients in the worm castings are readily available for the tomato plant to absorb, spraying the liquid compost tea can significantly increase the yield.

How Much Worm Castings Per Tomato Plant?

Add ¼ to 1 cup of worm castings in every tomato plant hole.

However, the amount of vermicompost depends on several factors, including climatic conditions and the size of the container.

Those who’re growing tomatoes in containers are recommended to add 1 cup of worm castings in a 5-gallon bucket.

When used as mulch, spread a thin layer of the organic fertilizer around the tomato plant.

1 cup of worm castings will be sufficient to enrich tomatoes during the season. Along with this, you’re advised to use balanced organic liquid fertilizer during the growing season.

Check this: Can You Eat Tomatoes with Black Spots?

How often do you add worm castings to tomato plants?

Apply worm castings after every 2-3 months.

Organic fertilizers don’t have the danger of burning plants, but this doesn’t mean you repeatedly add worm castings to plants.

During growing season, apply once every 4-6 weeks.

Conduct soil tests to determine the nutritional requirements of the plant.

Are Worm Castings Good for Tomatoes?

Yes, worm castings are good and safe to be used on tomato plants. 

You can add it to the plant hole or use it as dressing around the plant.

In both ways, it releases nutrients that can enrich the plant.

Also Read: What causes white lines on tomatoes?

Important Tips While Fertilizing Tomato Plants

Tomatoes need nitrogen, phosphorus, potassium, calcium, potash, and magnesium for ideal growth.

Along with these nutrients, tomatoes need trace minerals that ensure the production of plant hormones and balance nitrogen levels.

Though worm castings include all required nutrients, you must conduct a soil test before fertilizing tomatoes, as in some cases, nutrient levels can be lower.

  • After applying fertilizer, give your tomato plants an adequate amount of water.
  • Water is the medium with which all nutrients in the soil are transported to the plant.
  • Avoid over-fertilizing your tomato plants.
  • Choose well-drained soil, as it helps to avoid overwatering issues.
  • If you’ve already added worm castings or old compost to the plant hole, then your tomato plant doesn’t need to be fertilized till it reaches a certain height.
  • Two weeks before flowering, use phosphorus-rich fertilizer to enhance tomato flowering.
  • Always opt for a balanced fertilizer to enrich your tomato plants.
  • When you notice the main stem of the tomato plant is thick, you can start applying balanced fertilizers.
  • Check for the signs of over-fertilization or nutritional deficiency.

Also Read: Are Eggshells Good for Tomato Plants?


Organic growers can now use worm castings to fertilize tomatoes, as it reduces wastage and ensures a consistent supply of nutrients.

Worm casting is a slow-releasing fertilizer that enhances soil’s ability to absorb nutrients from the soil.

Adding 1 cup of worm castings in the container improves soil structure, helps to retain moisture, and drains excess water from the pot.

Nutrients in worm castings can be low when compared to commercial fertilizer, but they compensate for this by attracting beneficial microorganisms.

Enzymes released by the breakdown of organic compounds can help to deter insects and pests.

Worm casting is a great soil amendment that increases nutrients in the soil and inhibits soil-borne diseases.