Compost or Worm Castings? What Is The Best? Uncovering The Ultimate Soil Amendment

Written By Jenn

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Compost and worm castings are both good for the soil and loved by gardeners. Is one better than the other?

Compost is a standard choice for many gardeners, as it’s relatively cheap, easy to make, and readily available. Compost is a perfect mix of organic matter that has decomposed, resulting in a nutrient rich mix to add to and vastly improve the structure and quality of soil.

Worm castings, also known as vermicompost, are the excreta of red wiggler worms. They are considered a high-quality organic fertilizer due to their fine texture and nutrient density.

Worm castings, also known as vermicompost, are the excreta of composting worms. They are considered a high-quality organic fertilizer due to their fine texture and nutrient density.

In the following paragraphs, we will delve more into the advantages and disadvantages of each option.

Compost and Worm Castings Overview

Defining Compost

mature compost

Compost is a organic matter that has decomposed over time.

Compost is created by breaking down various waste materials like kitchen scraps, yard waste, and other organic materials through the natural process of decomposition.

I like using compost in my garden because it helps improve soil structure and promotes healthy plant growth by providing essential nutrients and beneficial microorganisms.

Defining Worm Castings

vermicompost in man's hands

Worm castings, also known as vermicompost or vermicast, are the nutrient rich excrement of earthworms. As the worms consume and digest organic matter, they convert it into a highly valuable, nutrient dense substance that is easily absorbed by plants.

I find that incorporating worm castings into my gardening routine significantly boosts the health and productivity of my plants.

Main Components of Compost and Worm Castings

Both compost and worm castings share similar characteristics, but noticeable differences make each valuable for different purposes. Below, I’ll explore the main components of both:


  • Compost contains a diverse range of nutrients deriving from the decomposed organic matter, such as nitrogen, phosphorus, and potassium.

  • Compost is high in organic matter which is vital for soil structure as it helps to enhance water retention and overall soil quality.

  • Compost contains beneficial microorganisms which contribute to the breakdown of organic matter, promoting healthy plant growth.

Worm Castings:

  • Worm castings are higher in nutrients than compost, often containing more nutrients than compost, including a higher concentration of essential elements like nitrogen, phosphorus, and potassium.

  • Worm castings contain nutrients that are more easily absorbed by plants than those in compost, ensuring their longer availability for plant growth.

  • Worm castings, similar to compost, harbor beneficial microbes, including bacteria, fungi, and protozoa, which can enhance nutrient cycling and soil health.

In summary, both compost and worm castings offer remarkable benefits for my garden as they provide essential nutrients, improve soil structure, and harbor beneficial microorganisms.

compost or worm castings

Making and Using Compost

Composting Process and Materials

In my experience, composting is an essential gardening practice that helps recycle organic waste and improve soil quality.

The composting process involves decomposing organic materials, such as leaves, grass clippings, and kitchen scraps, in a controlled environment.

This process of composting, requires a balance of carbon-rich materials (like leaves, hay, and straw) and nitrogen-rich materials (like grass clippings, fruits, and vegetables) to promote decomposition by microorganisms.

I ensure that the compost pile has adequate moisture and aeration for efficient decomposition.

When making compost, begin by layering different materials in alternating layers, starting with bulky materials like branches for aeration at the bottom, followed by leaves, grass clippings shredded newspaper, and kitchen waste.

It’s essential to regularly turn the compost pile to supply oxygen and maintain the decomposition process.

two compost bins made form wooden pallets

Benefits of Compost for Soil and Plants

I’ve found that using compost in my garden offers multiple benefits to both the existing garden soil and plant health.

First and foremost, compost is an excellent organic fertilizer, adding essential nutrients like nitrogen, phosphorus, and potassium into the soil. This helps to promote healthier plant growth and increased crop yields.

Compost also improves the soil’s water retention capacity. The organic matter in compost increases the soil’s ability to hold moisture. This reduces the need for frequent watering and also protects plants during dry weather.

Compost promotes better soil aeration, making it easier for plant roots to penetrate and access nutrients.

Compost introduces beneficial microorganisms into the soil. These microorganisms help break down organic material further, converting it into humus, which enhances soil fertility and stability.

Compost can reduce soil erosion, as the humus rich soil is less likely to wash away during heavy rain.

Ribbon Organics OMRI Certified Organic Compost Size: 7.9 Gallons, 32-35 Pound Bag

Making and Using Worm Castings

Worm Composting Process and Materials

A worm farm, also known as vermicomposting or vermiculture, is a contained compost bin where live worms feed on household food scraps and other organic matter. As the worms consume the compost, they leave behind nutrient-rich waste, called worm castings or vermicompost, which can be used as fertilizer for plants and gardens.

Vermicomposting or worm composting takes place in either a commercially bought container, often called a worm farm or a DIY worm farm.

Worm castings or vermicast are produced as the composting worms consume the organic material, which is essentially worm manure.

This process of producing worm castings, takes a few weeks to a couple of months, based on factors like the temperature and moisture levels in the worm farm.

Once the bulk of the bedding has been consumed and transformed into castings, I harvest them by separating the castings from the worms and any leftover bedding material.

Brut Worm Castings – 30 Lb – Organic Fertilizer – Natural Solution for Healthy Houseplants, Flowers, and Vegetables - Use Indoors or Outdoors - Odor Free

Benefits of Worm Castings for Soil and Plants

I have discovered that worm castings are an excellent soil amendment for numerous reasons:

Worm castings are packed with essential nutrients like nitrogen, phosphorus, and potassium that support plant growth.

As the composting worms break down organic materials, they foster the growth of beneficial microbes, which improve soil structure, aeration, and water-holding capacity.

The nutrients in worm castings are released slowly, providing a steady supply for plants without the risk of over-fertilization.

Worm castings contain natural enzymes and compounds that help plants fend off pests and diseases.

In my garden, I use worm castings as a top dressing around existing plants or mix them into the soil when planting new ones. Mixing worm castings with compost in a 15%-20% castings to 80%-85% compost ratio yields impressive results.

By doing this, I have experienced healthier, more robust plants with fewer pest and disease issues.

Comparing Compost and Worm Castings

Nutrient Content and Availability

When it comes to nutrient content, worm castings have a higher concentration of macronutrients than compost: Nitrogen 2.5% vs 1.5%, Phosphorous 2.0% vs 0.6%, and Potassium 1.9% vs 1.0%.

This means that worm castings provide a richer source of essential nutrients for plants. Calcium is also found in higher concentrations in worm castings vs compost, which is crucial for plant growth and development.

However, it’s important to note that nutrient availability depends on the quality of the compost or worm castings. In general, worm castings tend to release nutrients more slowly, making them less likely to cause nutrient burn or harm delicate plant roots.

Soil Conditioning and Drainage

Both worm castings and compost can contribute to soil aeration and drainage. But worm castings popularly known as vermicast or vermicompost, have a fine, crumbly texture that improves drainage better than traditional compost.

This can be particularly beneficial in heavy clay soils where water tends to puddle and drainage is poor.

heavy clay soil
Maybe the gardener can come back and use some worm castings in this clay soil!

Both worm castings and compost can help improve the soil’s structure and water retention.

When mixed into the soil, they allow water and air to infiltrate more easily and encourage plant roots to grow deeper. This helps plants develop a more extensive root system.

Benefits for Microbes and Microorganisms

The presence of beneficial bacteria and fungi in the soil is critical for healthy plant growth, and both compost and worm castings support these vital communities.

Compost, being an organic material, contains a diverse range of microbes that can outcompete harmful organisms and break down organic matter to release vital nutrients for plants.

In contrast, worm castings are the by product of the decomposition process of what worms eat, which means they contain beneficial microorganisms and enzymes not typically found in compost.

Worm castings also deliver beneficial microbes that can help protect plants from diseases and pests.

Overall, both compost and worm castings contribute to building a vibrant, living soil teeming with beneficial microbes, providing an excellent alternative to chemical fertilizers in gardens and other agricultural settings.

Limitations Of Using Worm Castings Or Compost

Price Differences and Affordability

Worm castings offer a highly nutritious soil amendment but they tend to be more expensive than regular compost because it takes longer for worms to produce castings than it does for organic materials to decompose in a compost pile.

Vermicomposting typically takes around twice as long as regular composting.

Compost, on the other hand, can be made by gardeners using readily available and inexpensive organic materials like kitchen scraps, yard waste, and other leftover plant matter.

This accessibility makes compost more budget friendly than worm castings, which may require a more significant investment in equipment like vermicomposting bins and worm colonies.

Managing Pathogens and Pests

Compost and worm castings are organic materials. Improper management can lead to the growth of harmful microorganisms or the attraction of unwanted pests.

In some compost piles, high temperatures generated during the decomposition process can help kill off pathogens, but I have to ensure the compost pile is adequately managed, turned frequently, and reaches the right temperatures. Achieving the ideal compost conditions can be labor intensive and requires me to monitor the pile closely.

When using worm castings, it’s essential for me to maintain a healthy environment for the worms that minimize the risk of pathogens.

Proper vermicomposting practices include regulating the moisture content, providing adequate bedding, and maintaining the right pH levels in the worm bin.

Practical Applications and Best Practices

When to Use Compost

For my vegetable and flower gardens, I generally use compost when I want to improve the overall soil fertility and structure. Compost, which is made up of broken down organic matter such as leaves, grass clippings, and food scraps, helps to aerate the soil and increase its capacity to retain moisture.

It’s especially beneficial when applied as a top dressing in the spring, just before planting season. I also like to mix compost with the soil in my potted plants to provide them with essential nutrients and to promote healthy plant growth.

When to Use Worm Castings

Worm castings, also known as vermicast, are nutrient-rich excrement or worm poop produced by red wigglers. I prefer to use worm castings when I need a more concentrated source of nutrients for my plants, like when I’m transplanting or need to boost growth.

Worm castings help improve soil structure by adding beneficial microbes and improve nutrient availability. They are particularly effective for flowers and vegetables that require a richer source of nutrients. I also like to add them to the soil in my potted plants for an extra nutritional boost.

Mixing Techniques for Maximum Benefits

I’ve found that combining compost and my own worm farm castings can have a synergistic effect, resulting in even better plant growth and soil improvement.

To get the most benefits from this mixture, I typically create a 50:50 blend of compost and my own worm castings myself. This allows me to reap the benefits of both soil amendments for my vegetable, flower, and potted plant needs.

When applying this mixture as a top dressing, I usually spread a 1-2 inch layer over the soil surface and then gently mix it into the top few inches of soil. This method helps to distribute the nutrients more evenly throughout the soil and encourage deep root growth.

As a soil amendment for transplanting or repotting plants, I mix the 50:50 blend directly into the planting hole, ensuring that the plant’s root system comes into close contact with the nutrient-rich mixture. This helps to stimulate root growth and minimizes transplant shock.

VermiHut Plus 5-Tray Worm Compost Bin – Easy Setup and Sustainable Design

Frequently Asked Questions

What are the benefits of worm castings compared to compost?

Worm castings offer several benefits, such as higher nutrient content, improved soil structure, and decreased risk of diseases in plants.

They release nutrients at a slower rate, ensuring a long-lasting impact on plant growth.

In contrast, compost also benefits the soil, but its nutrient content is generally lower than that of worm castings.

How do worm castings and compost differ in nutrient content?

Worm castings contain higher concentrations of nitrogen, phosphorus, and potassium compared to compost.

This makes them more effective in promoting plant growth and crop yield.

On the other hand, compost provides organic matter that helps improve soil structure and water retention, but its nutrient content is generally lower.

Can worm castings be used as a substitute for compost?

Yes, worm castings can be used as a substitute for compost. However, it’s essential to recognize that each material has unique benefits.

While worm castings provide high levels of nutrients, compost aids in improving soil structure and water retention. Therefore, using them together can provide the best results for your plants and soil health.

What are some pros and cons of using worm castings in gardening?

The advantages of using worm castings include higher nutrient content, better soil structure, and less risk of plant diseases.

These benefits can lead to increased plant growth and health.

The disadvantages include the longer time and effort required to produce worm compost castings.

vector - composting worm
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