What is my soil type? How-to identify and amend your garden soil
Ferry-Morse Home Gardening Blog | August 2021
A gardener cupping a fresh soil sample in their hands.
When it comes to gardening, you may think you need a lot of specialized knowledge to be successful.
The truth is, most of us learned what it takes to grow a plant when we were very young: water, sun and soil. Most beginning gardeners feel fairly comfortable diagnosing how much sun and water their plants receive, but are stumped when it comes to the quality of their soil.
This article will show you how to identify your soil texture and introduce you to various soil amendments and their use.
Composition of Soil
Soil is made up of different components of various sizes.
These components can be relatively large, as is the case with sand, or very small, such as clay. There are three main particles that determine the texture of your soil:
- Sand is the largest, or most “coarse”, particle found in soil. It does not hold much water or many nutrients, but is excellent for aeration
- Clay is the smallest, or most “fine”, particle found in soil. It holds a lot of water and nutrients, but is so dense that it can restrict root growth and become oversaturated
- Silt is a medium-sized particle, which possesses properties that are an ideal balance between sand and clay. Silt retains water and nutrients while still allowing for good drainage
Testing Your Soil Texture
It’s not necessary to use complex or expensive tools to determine your soil texture.
Simply take a clean glass jar with a tight-fitting lid and fill 1/3rd of it with your native soil (remove any larger twigs or rocks first).
Then, fill the rest of the jar with water and a few drops of dish soap. Cap the jar, shake vigorously for three minutes and then set somewhere to rest undisturbed for 24 hours.
An illustrated walkthrough on how-to test your garden soil sample at home.
After your jar has had time to rest, you will notice that three distinct layers have formed. This is because the particles settle at different speeds due to their size.
The bottom-most layer is the larger sand particles, followed by silt in the middle and clay on top. Observing the relative depths of each layer will tell you the primary components of your native soil.
An infographic depicting how you can interpret the results of your soil sample.
If the bottom layer is the largest, you have sandy soil that will have difficulty retaining moisture and nutrients. This can be remedied by adding amendments like peat moss or compost.
If the top layer is the largest, you have clay soil, which will drain slowly and inhibit root growth. Drainage can be improved through the use of amendments like perlite or vermiculite.
If the middle layer is the largest, or if all three layers are similar in size, congratulations! You have a soil that is high in silt: this kind of soil is referred to as “loamy”, and provides an ideal balance between water-retention and drainage.
And if you’ve discovered that you don’t have perfect soil, don’t worry! As mentioned above, even the most difficult soil can be improved through the use of amendments.
What is an amendment?
Amendments are any product, organic or inorganic, that you add to your soil to change its quality. Using soil amendments you can change the pH of your soil, add nutrients and improve drainage. Let’s review some of the most common soil amendments:
- Perlite is naturally-occurring volcanic glass that has been “popped” like popcorn! It’s large size and porous structure give it the perfect mix of moisture-retention and aeration properties
- Vermiculite is similar to perlite in that it is a natural mineral that has been expanded using heat. Vermiculite is better at retaining moisture than perlite, but allows for less aeration
- Peat Moss is made of decomposed organic material collected from peat bogs. It acts like a sponge, sucking up water and nutrients. It is naturally acidic, and therefore ideal for plants that prefer a lower pH
- Compost refers to various mixtures of decomposed organic matter. Compost improves water retention in addition to adding nutrients to the soil. It is more alkaline than peat moss
- Lime is the name for (surprise!) ground limestone, and it can be used to make soil more alkaline. This can improve nutrient uptake and water penetration, making it ideal for use in a seed starting soil mix
Various types of amendments you can use in your soil.
Individual soil amendments are like ingredients you can use to make your own special soil recipe.
If you have heavy clay soil, add larger particles like perlite or vermiculite to improve aeration.
If you have a coarse, sandy soil, add organic material like peat moss or compost to improve nutrient- and water-retention.
Over time, the continual addition of amendments will improve your native soil. Some, like inorganic perlite and vermiculite, will remain in your soil for longer as they do not decompose rapidly. Others, like compost, you will want to replenish every year, as the nutrients it contains are absorbed.
For many beginner gardeners, choosing the right amendments and determining the right quantities to improve your soil is a daunting task.
Never fear! It’s for this reason that brands like Jiffy have developed pre-mixed soils such as the Natural & Organic Seed Starting Soil Mix, where the guesswork is taken care of by creating a blend of peat moss, vermiculite and lime which is ideal for starting seeds.
And whether you choose to use a quality pre-mixed soil blend or experiment with your own soil amendment recipe (or both!), you can do so confidently knowing that the mysterious science of soil isn’t so mysterious after all!