Separating Soil from Dirt
You can use these lesson ideas to teach students about the importance and ecology of soil.
By Lynsey Peterson
“Soil isn’t dirt,” I tell my students. “Dirt gets on your clothes or floors; soil is an ecosystem with interacting biotic and abiotic factors.” Yet, my students continue to use the terms dirt and soil interchangeably until I show them the difference.
To show my students the amazingly complex world of soil, I take them outside and allow them to dig up some with small shovels or spades. We conduct a soil texture analysis, which is actually quite easy and not all that technical. Using a flow chart and a little water, we perform a series of physical characteristic tests by rolling and pinching moist soil. We classify the soil based on its percent composition of sand, silt, and clay. This also gives us an opportunity to discuss the abiotic components of soil: air, water, and small pieces of rocks and minerals. We take larger samples of our soil indoors to look at its biotic components.
Once inside, we set up Berlese funnels. You can purchase these or make them out of a funnel, screen, and cup. Place a piece of screen, netting, or cheesecloth in the bottom of the funnel. You want the soil to stay in the funnel, but allow small organisms a pathway out. Put the soil into the funnel (holding it over the garbage can to avoid a mess) and place the funnel over the cup. Students can put a small bit of water in the cup to help the organisms survive the night. The entire Berlese funnel setup goes under an incandescent lamp. The heat and light from the lamp drives the soil organisms downward, through the funnel and into the cup. When your students return the next day, they will see the macroinvertebrates that make the soil their home.
I have my students practice their classification skills by identifying the organisms they find. I also have them pass their organisms to the other groups so that every student gets to see what was found. The students research the organisms and find out what they eat. We discuss the other organisms present in soil, such as bacteria, plant rootlets, fungi, and protists. Then we create a food web to illustrate the soil ecosystem.
Once we’ve investigated the properties of and organisms in soil, my students aren’t so quick to call it dirt. You can also try these other ideas to show your students the complex soil ecosystem.
Dirt Isn't Just Dirt:
Students remove small measured chunks of soil from the schoolyard and then take them apart in order to identify and count all of the animals found within each chunk. They submit their data for others to compare and analyze.
Students prepare for a field trip. They navigate through an Underground Network site. This "field trip" can be conducted in a patch of healthy grass or soil anywhere you can find it: right outside your building, in a backyard or at a neighborhood park
Students analyse the biotic and abiotic factors that influence forest soil development and use a soil profile to identify soil horizons. They analyze the physical properties of soils and assess practices that protect soils and minimize degradation.
Students examine and discuss the physical characteristics of soil particles. In groups, they compare and contrast different soil samples based on those characteristics. They also examine the relationship between particles in the soil and soil texture.
Students study and classify soil. In this soil science lesson, students classify soil by texture and size and study soil horizons. Students label the soil types with their specific soil horizon and learn about permafrost. Students complete a soil horizons worksheet.