Texture By Feel
(Or How do those soil judges do it anyway?)
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One of the things that's most important about soil science is figuring out exactly what's in the soil you're studying. There are lots of laboratory experiments for figuring that out, but one of our favorites is the measurement that let's you go outside, find some soil, and test it in a fun and different way.
If you've done any studying of the soil, someone has probably mentioned "Texture By Feel." What this means is that scientists (and others who work with or just plain like the soil) want to know what sizes of particles are in the soil. One of the ways they find out is to dig up some soils from outside, take the sample in their hands, and figure out what's in the soil by feeling it.
Three different size particles affect the way the soil feels or the "texture" of the soil. They are called sand, silt, and clay. You probably felt sand the last time you were at the beach (it's the one that feels so gritty between your toes). You may have felt clay in an art class if you worked with a potter's wheel or molded some pottery for your parents. Clay feels sticky and takes a lot of pressure to squeeze. Silt feels soft and silky, just like flour used for baking. If you've ever helped to bake cookies and worked with the flour (before the chocolate chips were added) you've probably felt what silt feels like.
Once the amount of sand, silt, and clay is known, you can give the soil a texture class name. These names change depending on how much of each size particle is in the soil. We use the "Textural Triangle" to give us the names of the textural classes.
Why is it Important to Know the Soil Texture?
There are people who are really good at sensing just how much sand, silt, and clay a soil contains. They spend a lot of time studying the way different soils feel. Soil scientists use the texture method as a standard part of their field soil analysis.
Some people make describing a soil profile in to a national sport! These people are called soil judgers. Soil judgers compete in contests where they are asked to describe many properties of the soil profile in a specific amount of time. The soil judgers who come closest to the "correct" descriptions, win.
Soil Judging contests usually are between students at Colleges or Universities. But, anyone can learn to describe the soil in the same way that soil jusgers do. If you'd like to give some of those soil judgers out there a run for their money, here are two different ways to help you figure out how much sand, silt, and clay are in your soil sample. Each way works just as well, so choose the one you feel more comfortable with.
Method 1: Using Textural triangles:
Method 2: Using a Texture By Feel guide:
Or, you can download the color version postscript file or the black and white version postscript file.