Texture (Silt, Clay and Sand)

The FAO Soil Doctor guide provides a standardized methodology for determining soil texture by hand on site:

The ribbon method:
Take a sample of soil and remove the > 2 mm fraction (gravel — see below, roots, organic material) by sieving or by hand. The sample should be sufficient to fit comfortably into the palm of your hand. Moisten the soil with a little water and knead it into a ball. Continue to work the ball, adding more soil and water if necessary, until the soil no longer sticks to your fingers and there is no apparent change in plasticity (usually 1 – 2 minutes).

Using a clean, moistened hand, place the ball between your thumb and forefinger and slide your thumb across the soil (shearing) to extrude a ribbon. Soils with high clay content are further categorised by moulding the bolus into rods. If the rods fracture the soil is assigned a texture grade lighter than a medium clay. This method has been adapted from McDonald et al. (1998).

Gravel (particles > 2 mm) is removed from the soil prior to texturing because it does not contribute to chemical and some physical properties of soils.

Detailed methodology on how to measure soil texture on site can be found at Soil Testing Methods from FAO pg. 4-15.

Detailed information on soil sampling such as where to take the samples from, how many, the best time to sample, and depth of sampling, can be found at the Farm Carbon Toolkit.

Note: To know the exact percentages of sand, clay and silt it is necessary to send the sample to a laboratory.