Habitats, part 1: Soil (Nature Study, Lesson 216)

My boys, like most boys, play in dirt all the time, but they have never really taken a moment to look at it closely. I asked them to observe the color, texture of the soil in the backyard and to notice things such as roots, leaves, pebbles and any living critters. I asked them to divide their find into living and non-living things and also to think about how they relate to plants, animals and humans as a beginning to thinking about dirt as a part of ecosystems.

I had them sketch out a simple food chain We then talked about what each part of the food chain might possibly leave in the soil. Another great activity, which we didn't get a chance to do this time, is to encourage critters out of the soil with a lamp. Put a small amount of steel wool (not the kind with soap) in the bottom of a funnel to keep the soil from falling through the hole. Gently place 1-2 cups full of soil in the funnel. Place the funnel in a glass jar.  Place a desk lamp with an incandescent bulb above the funnel (about 8 inches from the soil) and watch as the tiny animals move downward through the soil to escape the light and heat and fall into the jar. If you are worried about the little guys escaping, you can put an inch or so of water in the bottom of the jar for them to fall into.

Comparing two types of soil brings even more observations and comparisons of color, texture, odor and moisture content. Clay soils tend to be sticky when wet and can easily be rolled into a ball. It absorbs and retains water. Sandy soils are crumbly and do not hold water well. We talked about places in which one soil would be desired over the other and why. 

We talked about how the different soils came to be. I also asked them to think about the fact that soil is a coating on all the earth. 

I made a "soil" parfait similar.   As they ate their treat, I noted the different layers. 

The top layer, representing the organic material, is a mixture of nuts and chips on a layer of  top soil pudding. A gummy worm added to represent the living things in the layers of soil. The next layer down, the topsoil (pudding) is mixed with gravel (cookie crumbs). The next layer, the subsoil, is made up of some larger pieces of cookie to represent weathered rock and then at the very bottom, (cookie) bedrock.

We made a soil profile test of the soil in the backyard. To make a soil profile, fill a vial (we actually used an clean, empty spice bottle) with about one inch of dirt. 

Add a pinch or so of alum. This acts as a dispersing agent, helping the soil  particle to break into smaller part and settle out into layers by density. Fill to the top with water. Cover and shake vigorously and then let stand. The hard part is getting them not to touch it again at this point, to give it a chance to layer. While they are waiting, I asked them to make predictions of what they would see. 

Once it layered, we talked about what was in each layer and that some layers were larger than others. The floating layer is organic matter. The top layer is clay (usually mixed with the water), the middle layer is silt and the bottom layer is sand. It is fun to compare two sample to see the difference in the ratios. If you let the soil profile sit on a shelf for several days, the layers become even more pronounced.
You can compare two types of soil to compare and contrast the differences.