Soil Texture

Soil Texture by feel

What is soil texture?

Texture refers to the relative proportion of sand, silt, and clay-sized particles in a soil. Texture is sometimes described by differentiating heavy (high-clay) and light (sandy or loamy) soils. Soil texture is a major determinant of the workability, water retention, and drainage of soils, along with the level of organic matter (see the POXC and particulate organic matter tests) and level of aggregation (see the aggregate stability test). Clay and loam retain more water for crops than sandy soils; sandy soils drain easily, while clay soils can have issues with draining quickly especially if they become compacted or lack organic matter. In addition, the level of clay in soil can markedly affect its fertility characteristics since crop nutrients such as potassium, calcium, and magnesium are held on the particles of many types of clay. Higher clay content soils can also generally store more organic matter over time if they are receiving organic matter inputs like manure or crop residues.

Because sand, silt, and clay are three components in soil that sum to 100%, the texture of soils can be categorized on a textural triangle seen below.

Above, the soil textural triangle. Different texture types like “loam” or “sandy loam” are described by their proportions of sand, silt, and clay. For example, a clay loam has proportions of about 35% silt, 30% sand, and 35% clay (the point in the diagram just above the ‘O’ of clay loam) with a range of values that define the light green “clay loam” zone. To avoid confusion in using the diagram, pay attention to the direction of the percentage labels around the outside, which align with the lines you should use to assess a point on the diagram, and also their relation to the 100% types of clay, silt, and sand.

Relative size of different soil particles:

The diagram below shows the approximate relative size of sand, silt and clay particles, and compares them to some common objects (pencil point, human hair, bacteria).

Materials you will need:

Water (any type will do, stream water is acceptable)
Your hands!
For the United Nations Food and Agriculture Organization (FAO) test below, some people find it helpful to roll out the “sausage”, “pencil”, and other shapes on a flat surface like a board, table, or sheet of plastic on the ground.
A 2 mm sieve may be helpful to prepare a sieved sample before testing, but pebbles and coarse fragments can also be simply removed by hand.

Method step by step:

Option I. USDA feel method:

The USDA (United States Department of Agriculture) method below is a relatively precise method once you practice it a few times, and is definitely precise enough to relate to the functional attributes of the different textural types in the textural triangle. The final step in assessing a wet pinch of soil will come more easily once you have assessed a few different soils and can note the difference between gritty and smooth feel of a soil. We have noticed that new users often find the FAO method (Option II below) easy to use as well. The two methods can be used to check each other when performed on a soil, since both are relatively rapid and should give similar answers.

Refer to the chart below for the procedure, also available for download here.

Option II. United Nations Food and Agriculture Organization (FAO) feel method:

Refer to the method steps below, also available here: