Kids – the most enquiring minds in the universe; add soil, a few everyday objects and a little science and you’ve got to be onto a winner! Here’s a pair of very simple experiments to get youngsters thinking about soil and start investigating it in a practical way; they’re very ‘hands-on’, require almost nothing in the way of equipment and, best of all, they’re great fun to do.
They’re perfectly safe, but as always, a bit of common sense, safety awareness and age/ability appropriate supervision is going to be called for – and nobody knows better than parents and teachers just how much mess kids can make with soil and water! Pick the site for your impromptu lab wisely, and keep away from electrics, and all should be well.
Time to get those hands dirty!
Experiment 1: Getting a Feel For Soil
You often hear soils being described as “loamy” or “clay”; here’s an experiment to help youngsters understand what that’s all about. All you need to get started is a small amount of soil and if you can arrange for a few different types, from a number of different gardens, so much the better. The method’s easy.
1.Remove any small stones or other non-soil bits that may be present, either by hand or sieve.
2. Take a small amount of soil and roll it into a ball in your hands. If the soil seems too dry to do this easily, add a small amount of water to wet it slightly. What does it look like? Does it feel sticky, or a bit gritty?
3. Try to roll the soil ball out into a sausage. How thin can you make it before it breaks?
4. If you’ve managed to make a sausage, can you bend it into a horseshoe shape, or does it crack apart?
So What Does That Tell Us?
Believe it or not, that tells us a lot about the texture of all that soil and here’s a simple guide to knowing what you’ve got. Just start at the beginning (step A), answer the questions and you’ll soon know what kind of soil you’ve just been investigating.
A. Did it feel gritty?
- Yes – go to step B.
- No – go to step D.
B. Could you roll it into a sausage?
- Yes – it’s a sandy loam.
- No – go to step C.
C. Did your skin get a little stained?
- Yes – it’s a loamy sand .
- No – it’s a sandy soil.
D. Could you make a horseshoe?
- Yes – go to step E.
- No – it’s a loam.
E. When you wetted it, did it feel a bit sticky?
- Yes – it’s a clay soil.
- No – it’s a loam.
So now you know; as the saying goes – simples!
Experiment 2: Soil Specific Gravity
OK, so let’s head off into the realms of some “real” science, using the idea of specific gravity to investigate what our soil is made up from a little further. It’s another one that our friendly meerkat would definitely approve of – pretty much all you need is some rulers, a few large coffee jars and a supply of soil, of course.
1.Sieve the soil to remove any large particles and break up any big clumps.
2. Add enough soil to fill the bottom third of your jar.
3. Top it up to about three-quarters full with water.
4. Screw the lid on tightly and shake like mad for two or three minutes, making sure that when you stop, all the soil has been mixed up in the water.
5. Put the jar somewhere where it won’t be disturbed for a few days, and wait until the water clears.
Here Comes The Maths!
You should now be looking at a series of distinct layers, the heavier soil types having settled out first, and each successively lighter one then sitting on top – based, obviously, on the differences in their specific gravity. What you have will depend on the particular soil used, but if you take your ruler, and use a bit of maths, you can work out the proportions of each type.
Measure the depth of each individual layer, and the depth of all of the settled soil at the bottom of the jar. Now divide the Layer Depth by the Settled Soil Depth and multiply the result by 100 and hey presto – you’ve just calculated how big a percentage of your soil that layer makes up. Repeat that for all of them and you’re well on the way to understanding the way soils are really put together.
Although we often take it a bit for granted, soil is a truly fascinating substance, and science is just such great fun. Put the two together and you’ve probably got the best excuse ever for getting really muddy. Enjoy – but don’t forget to order extra soap!