Dig your hands down into the earth. What do you feel? Every handful of soil has its own individual texture, and those characteristics offer a significant contribution to crops. What determines the unique textures of soil? Why is it important, and which type of soil has more erosion resistance? Find the answers to these questions and more with this informative article.
What Is Soil Texture?
When a pedologist mentions ‘soil texture,’ they’re referring to the amount of various sized sand, clay, and silt particles in a sample of dirt. The composition of these grains makes up the inorganic parts of soil and are the bits and pieces that bind with organic matter to form topsoil.
The size of soil’s particles and their spacing also determines how much water will flow through it. Soil with a higher concentration of large grains of sand will have a greater infiltration rate, while dirt that is primarily clay will pool water on its surface as opposed to absorbing it.
Soil Textural Classes
A soil’s textural classification refers to the combination of sand, silt, and clay that make up the soil. It can be determined using exploratory research methods such as feel. A coarse-textured soil is probably composed primarily of sand, while a fine-textured soil is most commonly dominated by clay.
Farmers can also take a quantitative approach with a hydrometer. With this lab-based method, the soil is mixed with a sodium hexametaphosphate solution to separate the earth’s aggregates into identifiable parts. The U.S. Department of Agriculture outlines 12 primary soil texture classifications including the four most common types: sand, loam, silt, and clay.
Sand is the largest sized dirt particle. Each grain ranges in size from 2.0 mm down to 0.05 mm. It feels gritty to the touch. Since sand is just a bit of gravel, it drains well but doesn’t do an adequate job of retaining essential water and nutrients. Gravel particles that are larger than 2.0 mm are not considered when determining texture.
The soil that’s referred to as loam offers a proportion of 40% sand, 40% silt, and 20% clay in a single sample. It’s often the dirt of choice for making bricks and provides plenty of organic material for growing crops.
Silt particles are considered moderate in size. However, with sizes ranging from 0.05 mm down to 0.002 mm, individual particles are too small to see with the naked eye. It has a similar shape as sand particles, just worn down to a smooth texture.
While it’s not as strong as sand, silt is better at holding both water and nutrients. Because it’s prone to losing small amounts of minerals from each particle, silty soil generally makes more minerals available to your plants.
The smallest sized dirt particle, clay is less than 0.002 mm in diameter. To put that in perspective, you’ll need to line up 12,000 clay particles side by side to measure one inch. Clay feels sticky in your hands and is an excellent building medium.
What Determines the Texture of the Soil?
The percentage of materials determines a soil’s textural class, including the common particles we’ve already met: sand, silt, loam, and clay. Its texture is an important characteristic that influences a diverse number of properties, including water infiltration rates, aeration, susceptibility to erosion, and pH buffering capacity.
The Importance of Soil Texture
The texture of your field’s soil is essential to a successful harvest on a variety of levels. From saturation to water-holding capacity, let’s discuss each component of soil texture’s importance.
The amount of clay, sand, or silt in the dirt defines the rate at which water is able to drain through it. Once saturated, water moves more quickly through sandy soils than it does through soil that’s heavy in clay.
Soil texture influences how much water is available to your plants. Once your field’s saturation level reaches capacity, your clay soil will hold more water than its sandy counterpart.
Well-drained fields are usually a sign of proper soil aeration. This texture of dirt is rich with air, which promotes a healthy root system and leads to a bumper crop.
Different textured soils also respond differently to erosion. Some are more susceptible to loss based on their percentage of silt and clay particles. Those soils have a higher erodibility level than a sandy soil under the same weather and tilling conditions.
Various soil textures also offer different levels of organic matter. This material breaks down faster in sandy soils than in silt and clay, likely due to the higher availability of oxygen for decomposition.
How Soil Texture Affects Erosion
Now we understand that a soil’s texture is directly related to the amount of clay, silt, and sand particles it contains. But what does this have to do with soil erosion? Soil texture has two main effects on erosion.
First, it influences the rate of infiltration and water’s ability to enter the soil. When it rains, does the water run off rapidly? If so, then you probably have sandy soil. This type of dirt has large pores that act like pipes, channeling water right into the ground.
Does the water collect on the surface or in low lying areas? If it does, then you probably have clay soils that are not known for providing good drainage.
Second, some types of dirt particles don’t detach as easily as others. Silt particles wash away easily because they’re tiny and don’t readily combine with other soil aggregates.
Which Type of Soil Is More Erosion Resistant?
One study suggests that an estimated 30 tons of agricultural soil are lost in the United States to erosion each year. This loss outpaces the rate of formation by an astonishing eight times.
So, which type of soil offers the most erosion resistance? The answer is clay. Clay is better at resisting erosion because it’s small particles hold water, making it a stickier compound than sand.
A soil’s texture affects many aspects of your garden, including erosion. Use this handy guide to help determine your dirt’s composition and how you can use that information to help you conserve topsoil.