Soil part 2: Texture is almost everything
Updated: Aug 3, 2020
You may think that the triangle pictured above looks very complicated, but once you learn how to use it you will understand how much fun it can be to categorize soils. This is a valuable tool that all soil scientists and people who regularly interact with soils use on the daily (usually as a mental picture rather than an actual photograph). This is a way to swiftly categorize soils based on texture.
Before we dive into the triangle we must first understand what makes up soils.
These are not exact percentages, but rather a guideline.
Some soils may have more or less of these four components.
When texturing soils, we are looking specifically at the mineral component and ratios of sand, silt, and clay.
Sand, Silt, and Clay
Hand texturing is an easy way to calculate clay composition, but if you want a really simple technique for determining soil texture use the water bottle method. Take a water bottle and add in soil, detergent, and water. Shake it until all of the soil is stratified (suspended in the fluid) and let it sit. Once all of the particles have settled (this will take much longer for the smallest of particles, clay, to settle out) you can then estimate the percentage of each particle within the bottle.
Once you know the percentage of each of the three particles you can go and look at your triangle and figure out your soil's texture.
Start with the clay:
Look at the bottom left corner and follow the arrow upward with the increasing of
percentage. When you arrive at 10% you can mentally mark that spot.
Silt: follow the top of the triangle down until you arrive 25%.
Sand: follow the arrow on the bottom right of the triangle left until you arrive at 50%.
Look and see where all three lines connect to determine your soil texture. For this soil it would be classified as a sandy clay loam.
Loams are highly valuable soils, and the combination of the different particles in different ratios can produce a variety of loams including clay loam, silty clay loam, sandy loam, loam, silt loam, and loamy sand.
Continue to practice and see how quickly you can determine the texture of a soil. Just remember that all three percentages of sand, silt, and clay should add up to 100%, otherwise the triangle will not work and you will probably be a bit confused.
Now why is soil texture so important?
The texture of soils greatly influences its function. Soils with more sand will increase the ability for water to infiltrate and it provides larger pore space for plant roots to grow deep into its horizons. Smaller particles like silt and clay have larger surface areas for cations (magnesium, potassium, and calcium etc.) to attach and provide accessible nutrients to plants and other organisms. They also hold water in tiny spaces to keep soils hydrated for much longer. The different pore sizes provide habitat for a variety of macro and micro-organisms. They also allow for air to be contained within their spaces to allow for plant roots to breathe and aerobic organism to function.
Have fun and let us know what you think! Was this exciting and new information that you feel has added value to your life? Is there something else about soils and their classification that you would like to know about?