Tests for Soil Texture

About Soil Texture

• Soils are usually divided into three textures: sand, silt and clay. Sandy soils have the largest particles and pores, which results in fast drainage. Silt soils are medium-sized with very light particles. Clay soils have the finest particles and the smallest pores. Sandy soils may not hold enough water to provide nutrients to plant roots. Clay soils, on the other hand, may retain too much water and cause root rot and other diseases. Loam soils provide an ideal balance of silt, clay and sand particles and are ideal for most plants.

Estimating Soil Texture

• To obtain a general idea of your soil's texture, moisten a bit of soil and rub it between your thumb and forefinger. If you have sandy soil, it will feel gritty and rough. Silt soils usually feel smooth and particles may slide easily between the fingers. Clay soil particles tend to stick together when wet and will feel sticky. To further test your soil, squeeze a ball of moist soil in the palm of your hand. Sandy soils will break easily, whereas clay soils will not break easily. Loam soils will stick hold together but will also be malleable.

The Ribbon Test

• To perform the ribbon test, moisten some soil and make a ball in the palm of your hand. With your thumb and forefinger, gently roll the soil to make a ribbon. If you cannot make a ribbon longer than 1 inch, your sand is either silt or sand. Sand soils will feel gritty, whereas silt soils will feel smooth. If you can make a ribbon that is longer than 2 inches long, you probably have clay soil.

Lab Tests

• Testing soil texture by feel is not always entirely accurate. As noted by the Colorado State University Extension, soils only need 20 percent clay to behave as a clay soil. Even if your soil is primarily composed of sand, it will act as a clay soil if it has 20 percent or more of clay. For the most thorough results, have your soil tested for exact percentages of clay, silt and sand. Since soil texture does not change, you should only need to have this test done once.