The Finger Rub Experiment
Take an amount of moist soil, about the size of a pea, and squeeze
it in between your thumb and fingers. What can you feel? If there
is a lot of sand in the soil you will feel its gritty presence.
Does smearing the soil on your finger leave a mark? If it does
the soil contains smaller particles of silt and clay. Soils with
a high level of organic material may appear almost spongy, allowing
water to be squeezed out. Trained soil surveyors can learn to differentiate
precisely the types of soil by its feel alone. You can also try
a touch of soil on the tip of your tongue to see how smooth or
gritty is it! Sand feels coarse and gritty to the touch as the
particles are relatively large. Silts have a smooth, soft feel
as the particles are smaller. Clay feels smooth and sticky as the
particles are very fine indeed.
Soil texture is the term used to describe the balance of the three
mineral constituents that go to make up soil; sand silt and clay.
One way to identify soil texture is to take a pinch of soil and
wet it gradually, whilst kneading it between your fingers and thumb,
until there is enough moisture to hold the soil together and the
soil is cohesive and sticks together. You can then use the method
below to correctly identify the soil texture:
Select the answer to the first question below and then follow
the questions through. The soiltype will then be identified. At
any time you can go back or start again. Once you've done one,
you can try another !