The Scientific Way
There are ways to find soil type by soil particle size. Since there are three different types of soil (Sand, Silt, and Clay) then each has its own size particles to test. For clay soils the particles are less than .002 milimeters and are why it has so much surface area. For silt soils the particles are each over .002 mm and under .05 mm in diameter. And finally there are five grades of the soil we call sandy, or just sand. Loamy soils are just a mix of the sand, silt, and clay.
- Very coarse: 1.0-2.0mm
- Coarse: .50-1.0mm
- Medium: .25-.50mm
- Fine: .10-.25mm
- Very fine: .05-.10mm
The Non-Scientific Way
This method involves no fancy testing and no lab work, just earth and water. While one may have to wait a bit for the results, it is free and can help if the area that is being tested tends to change from time to time. When conditions are right, this is a near fail proof method, and one seen in practice more than the particle size testing and other testing.
To do this test, wait until it has been two days past a rain. Pick up a scoop of the dirt that is needed to be tested and roll it around until it is the size of an average golf ball. Squeeze. Now how does it feel? Is it slippery? Then it is clay. Is it smooth earth? This means it is silt. Is it gritty? That is sandy.
Now take that ball while it is still there in a hand and open. Does it fall apart? That is sandy soil. Does it take a few minutes to fall apart? That is loamy soil. Does it stay as a ball? That is clay soil.
Differences between Soil Types
Soil types range widely and there are differences between them for the gardener. Silt soils tend to retain their water and nutrients. Sandy soils will be a good water drainer but will do so quickly. It is the quickest to warm. Clay soils are heavy and hold water for longer times, drying very hard. It takes the longest to warm. Loam is nothing but a mix of the three, and is the better environment for nearly all plants.
“A Georgia Native Plant Guide” –© 2005, Mercer University Press