Why Should You Add Topsoil To A Compost Pile - Backyard Boss
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Why Should You Add Topsoil To A Compost Pile

Are you having issues with your compost? Try adding topsoil! Compost is a great way to recycle your organic waste, like food scraps and leaves, into rich soil that you can use to fertilize your garden or lawn.

If you’ve ever tried to build a compost pile at home, you know it takes time to transform into the black gold your garden needs to thrive. Turning organic waste into nutrient rich compost is a skill you should acquire.

Compost needs different nutrients, air, and moisture to thrive. Lacking any of those elements means it won’t break down properly. This is where topsoil kicks, taking your compost to the next level.

Below you’ll learn more about topsoil and how to add it to your compost.

What is Topsoil?

Organic layer and topsoil of a Vertisol
Image credits: SoilPaparazzi via Canva

Topsoil is the uppermost layer of soil, around 8 inches deep, covering a plot of land. It contains a mixture of decomposed organic matter, minerals, sand, and silt called humus. This layer of soil is where most plants take root and where they derive their nutrients and moisture.

Topsoil is rich in organic matter and contains different microorganisms that accelerate the decomposition of organic material. A sandy topsoil can also be used to improve drainage

The Benefits of Adding Topsoil to Your Compost 

soil and topsoil
Image credit: Lakeisha Ethans for Backyard Boss

Adding topsoil to compost piles helps, here’s how:

  • Speed up the decomposition process and strengthens the compost
  • Increasing the number of nutrients available in your compost
  • Improve the texture of your finished compost
  • Make your compost easier to handle
  • Help prevent disease in your garden
  • Provides a good base for planting
  • Add bulk to your compost
  • Controls weed population
  • Allow air to penetrate deeper into your pile
  • Reduce odors
  • Improve drainage and water retention

Characteristics of Quality Topsoil

Handful of potting soil
Image credits: Alicia Christin Gerald via Unsplash

The characteristics of topsoil vary depending on the type of soil, climate, and environment. However, topsoil should generally have good drainage, high organic content known as humus, low pH, and adequate moisture. Test your finished compost soil’s pH before using it in your garden. While some plants thrive in alkaline soil, others do best in acidic soil, and some prefer neutral soil.

Use the following as a rule of thumb when selecting topsoil for your compost:

Neutral pH

It refers to the acidity or alkalinity of the soil. A neutral pH (5.5-7.5) is ideal for most plants.

Adequate Soil Pores 

Adequate soil pores are particles filled with water, air, and biota that aid drainage and retain moisture and nutrients. A lack of soil pores can lead to compaction, which makes the soil hard to work with and integrate into the compost pile.

Low Salinity

Low salinity makes it easier for plants to absorb water and nutrients from the soil. Ideally, your soil should have less than two dS/m (decisiemens per metre) soluble salts for optimum plant growth.


Texture refers to the appropriate blend of sand, silt, and clay in topsoil. It plays a significant role in your plant’s lifecycle since it controls water infiltration, moisture and nutrient retention, and drainage qualities of your soil. Ideal topsoil should have less than 30 percent clay, less than 70 percent sand, and less than 70 percent silt.

Organic Matter

Your topsoil should have high organic content for optimum plant growth. Organic matter helps prevent soil compaction and retains nutrients for plants to absorb. Ideal topsoil should have more than two percent organic matter by weight.

Topsoil Commercial Grades

Peat Moss
Image credits: Tortoon via Shutterstock

1. Premium Grade

It is the highest quality topsoil that comes from rich, fertile soils. It contains high levels of organic matter and nutrients that help improve the structure and fertility of the soil. Premium topsoil is ideal for planting trees, shrubs, perennials, vegetables, fruits, and flowers.

2. General Purpose Grade

General-purpose topsoil is suitable for any garden, including lawns, borders, flower beds, vegetable gardens, fruit trees, and perennial gardens. General-purpose topsoil is often less expensive than premium topsoil and have lower amounts of organic matter and nutrients.

3. Economy Grade

Economy-grade topsoil is a mixture of sand, clay, silt, and gravel. It does not contain enough organic matter or nutrients to make it suitable for gardening. Economy topsoil is commonly used for landscaping projects such as driveways, patios, and walkways. To use it for gardening purposes, you’ll need to add compost and soil amendments for healthy plant growth.

What’s the Difference Between Topsoil and Potting Soil? 

Texture, Arid Soil Types Samples
Image credits: Rita Meraki via Shutterstock

Topsoil is the soil’s first 2 to 8-inch deep layer that contains decomposed organic matter (humus) and mineral particles. However, the exact blend of sand, silt, clay, and organic matter differs between locations. Some topsoil may be optimal to use from the get-go, while others from different locations might be low on organic content or contain too much clay. 

This is why it’s a great idea to test your soil before using it in your garden. You can hire a professional, use garden soil testers, or DIY with household items. You may need to use soil amendments or soil conditioners to improve the soil’s texture, nutrient content, and pH levels before use.

On the other hand, potting soil is a mixture of peat moss, perlite, vermiculite, and composted manure explicitly designed for container gardening. It holds moisture and nutrients while providing good aeration, but it’s technically not soil. 

In a broad sense, potting soil is called soil, but it’s a growing medium that may or may not contain any soil. Although you can mix potting soil with your compost, it won’t yield the same result as using proper topsoil, as it differs significantly in composition.

Mixing Topsoil & Compost Together

laying soil on tarp
Image credits: sacratomato_hr via Creative Commons

Mix topsoil with compost to create rich, fertile soil for your garden. Many people add too much soil to their compost pile, but this does more harm than good. Too much soil can clog the compost. The idea is to sprinkle it throughout the pile.

Topsoil’s beneficial microorganisms can speed up decomposition in your compost pile by locking in moisture. Here’s how to add topsoil to your compost pile:

Step One: Start Your Pile 

Add 6 inches of brown material (dry and hard) to your container, followed by 2 inches of green material (wet and soft). Finally, add 2 inches of quality topsoil to start the decomposition process. Adding topsoil will prevent foul odors from attracting rodents, pests, and insects. Continue to add layers (brown, green, soil) until the pile is 3-5 feet high.

Step Two: Add Water

To make good compost, the overall moisture content of your compost pile should be about 60-65 percent (nearly as moist as a wrung-out sponge). Too much water will cause the compost to expand and become compacted, making it difficult for air to penetrate the mix. On the other hand, if the mixture is dry, add additional water to moisten the mix.

Step Three: Leave it Alone

After adding water, leave the pile alone for at least four days to start the decomposition process. After that, turn the compost pile with a pitchfork and monitor its moisture levels. You can turn your compost pile every three to seven days to ensure regular aeration. It can take anywhere between three and four months for your compost pile to decompose before it’s ready for you to use in your garden.

Topsoil and Compost – A Great Pair

Topsoil is the best way to add nutrients and microorganisms to your compost pile. It, in turn, will boost your compost production and yield a better result for use in your gardening activities.

While compost is rich in nutrients, bacteria, and fungi that help break down organic matter, topsoil is rich in nutrients that are easily accessible to plants. Mixing these two creates a perfect environment for them to thrive.

Hopefully, this article was helpful to you and gave you some clarity when it comes to adding topsoil to your compost pile. Let us know your thoughts and questions in the comment section below, and share the article if you liked it.

Happy Gardening!