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The jam jar soil experiment

Soil is made up of a mixture of sand, silt, clay and rotted plant (organic) material. Different soil types have differing percentages of each. The jam jar soil experiment helps you to understand what the proportions of these are for the soil you work with. You should try this experiment with soils from different areas and compare the results to see how soils vary. Try it also with the soils you get in bags from garden centres for growing seeds and see how that varies from your garden soil.

Step One

Take a clean, straight-sided jam jar and fill it about a third of the way up with the soil you are experimenting with. Also have ready another jar of clean water and a stirring stick.

Start off with a jar a third filled with soil

Start off with a jar a third filled with soil

Step Two

Now add the clear water until the jar of soil is almost full.

Add water stir and stir thoroughly

Add water stir and stir thoroughly

Step Three

Now use a stirring stick to stir up the mixture really thoroughly.

Stir the mixture thoroughly and wait for it to settle

Stir the mixture thoroughly

Step Four

Now leave the jar for one hour so the contents settle out and the water can start to clear.

The soil jamjar experiment - note the layers of soil

The soil jamjar experiment

Step Four

Now the water has settled out, you should be able to see different layers appearing. Sand particles are the biggest and weigh more than silt - so the bottom layer will be the sand part of the soil. Any pebbles will also be at the bottom. Next up is the silt layer. Silt particles are smaller than sand and weigh less so they appear over the sand. If you were able to separate out any clay particles they are the smallest and will be on top. If your soil is really thick clay then you may just be left with clay lumps at the bottom, Next up you will have the water. This is likely to be discoloured. The colouring is likely to be rotted plant (organic) material that is soluble (it's dissolved). Finally, at the top will be floating organic material which isn't fully rotted.

What you can do is now use a measuring tape to measure the height of the total soil and water (say 10cm), and then the height of each layer (say the silt is 1cm). Then you can work out the percentage of each part of the soil. This is called the soil texture. For silt for example the sum is 10cm divided by 1cm all multiplied by 100 to get the percentage (so 10/1 x 100 = 10%). Finish off by drawing a pie chart of the different proportions, and as noted above compare the results with other soils.

If you found this interesting have a look at the related Jam-Jar experiment in the Activity Sheets section, as well as the other activities there!