Understanding your soil can be the difference between thriving plants and struggling plants. Every type of plant will have a preference regarding soil type, and trees, shrubs, or perennials planted in less-than-ideal soils may not be very successful. So, let's learn about the different types of soil so that you can give your plants the best chance of growing strong, healthy, and beautiful.
What Are the Different Types of Soil?
The different types of soil may vary slightly depending on who you talk to, however, the three main types are sand, silt, and clay. Each of these different soil types are differentiated by particle size, with sand being made up of larger particles, silt being made up of slightly smaller particles than sand, and clay having the smallest particles of the three. Let's dive into some other differentiators when it comes to the three different types of soil.
Sand
Sandy soils primarily consist of small particles of weathered rock. There is very little organic matter, making this type of soil the lowest in nutrients. It also has a very low capacity for holding water, as water drains through sandy soil freely and the rock particles do not absorb any of the water as it passes through. Sandy soils usually have a more acidic pH and are airy and warm. Many plants may have a hard time surviving in such soils due to the lack of moisture and nutrients.
Silt
The particles that make up silt are smaller than sand but larger than clay. Silt is generally higher in nutrients and can retain a high amount of moisture. It has a very smooth texture, unlike the rough and gritty texture of sand. Silt is easily carried by moving currents and is often found near lakes, rivers, and other bodies of water.
Clay
Clay soils consist of the smallest particles, and due to the particle size, this type of soil is usually very compact and heavy with little to no airspace. It is extremely good at retaining water and is sticky when wet but smooth and almost powdery when dry. Many plants have difficulty growing in clay-heavy soils due to its density and lack of drainage.
Other Types of Soil
Other types of soil that are not one of the main three but that may be often seen or referred to include the following:
Loam
Loam is another term that is often used in conversations about soil, and it is simply the combination of clay, silt, and sand. The combination of the three types of soil can vary in ratios, giving you different types of soil such as clay loam, loamy sand, silt loam, silty clay loam, and so on. While sand, silt, and clay are primarily a reference to the particle size, loam is more a description of the soil composition. Ideal loamy soil mixes enough of each type of soil that they contribute their positive attributes and not their negative ones. For example, sand helps the denser soils to be more well-draining, while clay and silt contribute nutrients, organic materials, and moisture-retaining properties.
Peat Soil
Peat soils include soils that are high in organic materials. Peat soils are less common to find naturally and are usually a soil amendment that is found in garden centers, landscaping companies, or home improvement stores. Peat is very high in nutrients and has both good drainage and good moisture retention. People often purchase sphagnum peat moss to mix into their existing soils to change the soil structure, introduce nutrients, or change the pH.
Gravel and Rock
Some soils especially here in Colorado are dominated by rock and gravel, making them difficult to work with. Many soils that primarily consist of gravel and rock need to be replaced entirely, as the gravel and rock are difficult to cultivate and have no nutrients or moisture-retaining properties.
How To Determine What Type of Soil You Have
There are several methods for determining what type of soil you have around your home or in your gardens. Identifying the type of soil you are working with is important, as this will help you understand which plants will grow well or how you need to modify or amend your soil for certain plants to thrive.
Identifying Soil Texture by Measurement
As outlined in an academic paper by the Colorado State University Extension, here are the steps one should take to identify soil type by measuring the amount of silt, sand, and clay in the soil sample:
Step 1: Spread your soil sample out on a newspaper to dry. Remove all rocks, trash, roots, etc., and break up any lumps and clods.
Step 2: Finely pulverize the soil.
Step 3: Fill a quart-sized jar 1/4 full of soil.
Step 4: Then fill the jar with water until it is 3/4 of the way full.
Step 5: Add a teaspoon of powdered, non-foaming dishwasher detergent.
Step 6: Secure a leak-proof lid and shake the container hard for 10 to 15 minutes. This will break apart the soil aggregates, separating the soil into individual mineral particles.
Step 7: Set the jar where it will not be disturbed for 2 to 3 days.
Step 8: Soil particles will settle out according to size. After 1 minute, mark on the jar the depth of the sand.
Step 9: After 2 hours, mark on the jar the depth of the silt.
Step 10: When the water clears, mark on the jar the clay level. This typically takes 1 to 3 days, but some soils it may take weeks to fully settle.
Step 11: Measure the thickness of the sand, silt, and clay layers.
Step 12: Calculate the percentage of sand, silt, and clay.
[clay thickness] / [total thickness] = percent clay
[silt thickness] / [total thickness] = percent silt [sand thickness] / [total thickness] = percent sand
Step 13: Turn to the soil texture triangle and look up the soil texture class.
Identifying Soil Texture by Feel
As also outlined by the same academic paper by the Colorado State University Extension, there are also three feel tests one can conduct to roughly gauge the soil type:
1. Feel Test
Rub some moist soil between your fingers.
Sand feels gritty
Silt feels smooth
Clays feel sticky
2. Ball Squeeze Test
Squeeze a moistened ball of soil in your hand.
Coarse texture soils (sand or loamy sands) break with slight pressure.
Medium-texture soils (sandy loams and silt loams) stay together but change shape easily.
Fine textured soils (clay or clay loam) resist breaking.
3. Ribbon Test
Squeeze a moistened ball of soil out between your thumb and fingers.
Ribbons less than 1 inch
Feels gritty = coarse texture (sandy) soil
Not gritty feeling = medium texture soil high in silt.
Ribbons 1 to 2 inches
Feels gritty = medium texture soil
Not gritty feeling = fine texture soil
Ribbons greater than 2 inches = fine texture (clay) soil
Note: A soil with as little as 20% clay will behave as a clay soil. A soil needs 45% to over 60% medium to coarse sand to behave as a sandy soil. In a soil with 20% clay and 80% sand, the soil will behave as a clay soil.
How To Determine What Type of Soil You Need
Determining the type of soil you need will usually depend on the plants you intend to plant. Most plants will, however, grow best in a rich, loamy soil. Soil that is too clay-heavy can drown the roots of many of your plants, while soil that is too sandy will not provide many plant varieties with adequate moisture. You can amend soils with other materials to achieve the desired soil type, or you can replace your soil with a quality topsoil. It is also common to mix compost into your soil to increase the organic materials in the soil, which will help improve almost any soil type.
The Best Soil for Your Plants
We hope you have found this guide helpful! However, if you have any questions or still need assistance in determining your soil type or creating a soil mixture that will be conducive to growing strong and healthy plants both in your landscapes and gardens, we are here to help. At Bath Landscape & Irrigation, we make sure to bring in quality soil to ensure that any newly planted trees, shrubs, or perennial plants will thrive! To speak with a landscape designer about getting started on a project of your own, check out our services page and fill out a contact form. And for more resources and information on how to care for your landscape, the different services we offer, and more, visit our blog!
Resources:
Adrian Card, David Whiting, Carl Wilson, and Jean Reeder. "Soils, Fertilizers, and Soil Amendments." Colorado State University Extension. 2015. Web. Date accessed: March 2023. Retrieved from: https://cmg.extension.colostate.edu/wp-content/uploads/sites/59/2020/01/GN-210-Soils.pdf