13 November 2011

Fun experiment to determine your soil texture

Soil Texture Experiment

Getting to know your soil is half way to determining how well your plants will grow.

Your soil contains nutrients and minerals that allow plants to thrive so if you can identify your soil type – whether it’s clay, sand, peaty or loam, you can work with the soil you have rather than constantly fighting against it.

So how do you find out what your soil texture is?

A fun experiment you can carry out at home (and a great one for the children to help with too) is to place about a cup full of your soil into a straight sided, clean jar, removing any larger pebbles or stones first.

Add a tablespoon of laundry detergent and a tablespoon of salt to the soil then fill the jar with water to the top before screwing on a lid tightly.

Shake the jar for five minutes or so (you may need help!)

Leave the jar undisturbed where you can see it. After a couple of days the soil particles will settle into layers.

As the sand particles are the heaviest they will sink to the bottom first, followed by silt then clay. The thickness of each layer will help to determine how much of each is contained in your soil.

So as you can see from the result of our Greenside Up soil, a small layer of sand has settled at the bottom, then silt, with clay at the top, at roughly 20% sand, 30% silt and 50% clay.

The Greenside up soil is therefore considered a heavy clay soil. 

You can usually identify your soil type just by looking at it and feeling it, without the need for an experiment (this was just for a bit of fun) - sandy soil is lighter in colour than clay for instance.

So how do I do that?

Grab a handful of dry soil and add a few drops of water, mixing well until it become pliable. Try rolling the soil into a ball.


If it feels gritty, if it crumbles when you try to roll it into a ball then your soil is sandy.

Course sand feels like granulated sugar when rubbed between fingers.
Medium sand feels like table salt when rubbed.
Fine sand is harder to detect unless you hold your fingers near your ears as you rub it.

Sandy soils are easy to dig but water and nutrients flow through them easily, meaning they dry out quickly and will have to be replenished regularly.  Sandy soils warm quickly and retain their heat (just think of a warm beach) which some plants especially like, particularly carrots and their roots will swell.

Silt and Clay

If, when you try to roll the soil into a ball in your hand it holds together well, or if it feels much finer than sand, then your soil texture will be silt or clay. If it feels like plasticine then its fine clay whereas silt particles will leave it feeling like icing sugar. If you can roll the soil into a sausage and it forms a ring, its clay. If it forms a sausage but breaks up as you try to make a ring, its clay.

Clay soils are described as heavy and can be very sticky to dig. If you try digging when clay soil is wet you can damage the structure of it. Clay soils are slow to warm up but retain water better in the hotter months and therefore keep their valuable nutrients for longer.  Because their particles are so tiny they tend to pack together tightly which creates poor drainage and aeration and can contribute towards roots rotting.

Silty soils feel silky or soapy when moist.
Clay soils feel sticky when moist.

I'll be posting an article on the Greenside Up website soon explaining soil texture in more detail. In the meantime why not have a go and see what results you come up with.

If you'd like to read more about soil types, Peter Donegan wrote a much more detailed blog post about it back in 2008.


  1. Dee, I will share this with my hort students who have to do quite a few experiments for Soil Science Fetac Level 5.

    Ena Ronayne
    The Garden Design Co
    Tutor of Horticulture at Killester College of Further Education

  2. Thanks Ena, nothing like a practical for us to really learn what's going on.


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