Plants need soil, so asking what type of soil is in the garden is the first question a gardener should ask. The following experiment done by the grade 5 science students, is based on the Shake, Rattle and Roll experiment in the Junior Master Gardener Leader Handbook. Purpose: To identify the amounts of different sizes of soil particles that make up a soil’s texture in our school garden. Time: 20 minutes plus 24 hours to settle. Materials: clear plastic cups, plastic spoon, soil, water, permanent marker (The book calls for jars, but I try to use the cheapest and safest materials possible. A clear plastic cup with a plastic spoon to stir worked very well instead of a jar but I knew our soil was very sandy. If the soil is mainly clay, then a jar with a lid so the soil can be thoroughly mixed and suspended in water would work better.) Procedure: Students worked in pairs to complete the following
- Use a permanent marker to label a cup so each group knows which cup belongs to which group.
- Dig about 6 inches into the soil for the soil sample. Do not take the soil from the surface. Half fill the plastic cup with soil.
- Add enough water to fill to within half an inch (1.25 cm) of the top of the cup.
- Stir carefully with the plastic spoon to thoroughly mix the water and soil. Mash lumps against the side or bottom of the cup, then stir again until the soil is completely suspended in the water.
- Place the cup on a solid surface. Do not disturb it for 1 minute.
- Use a permanent marker to mark the side of the cup where the layers are.
- Leave the cups for 24 hours without moving or disturbing it.
- Observe and measure any changes in the layers. Record the results.
- Particles floating on the top of the water are bits of organic matter.
- The top layer of soil is clay, the smallest, lightest particles.
- The next layer down is silt.
- The bottom is sand, the largest and heaviest particles.
Results: Each student created a graph comparing the different layers of soil particles. The graph below was done by a student in the class.
Conclusion: We discussed how knowing the particle size and soil texture would influence our decision about where to have a garden and what to grow in the garden.