Soil is rarely devoid of life. Soil which supports plant life is teeming with many soil organisms, the majority of which are too small to see. Some examples of soil organisms are fungi, bacteria, nematodes, diatoms (algae), earthworms, ants, centipedes, millipedes, beetles, snails, and slugs. All these soil creatures and more make up the soil community. In STEM Club, we sought to discover for ourselves, what lives in our soils?
Most fungi and bacteria are supported by relationships with plant roots, so they stay close to plants. Any creatures that live on fungi and bacteria also stay close to the roots. Other larger herbivores, like beetles, ants, centipedes, and termites, feed closer to the surface where more plant debris is located.Therefore most soil creatures live within a few inches of soil closest to their food sources.
This community of organisms is deeply involved in the soil food web. It’s basically a recycling program, where plant and animal residues are broken down by a chain of soil consumers (nematodes, bacteria, fungi, mites, earthworms, etc), who are then consumed by birds and other mammals, cycling carbon and essential nutrients.
Soil protects soil organisms from harsh sun, wind and, rain, while still providing air, water, and nutrients essential to life. When soil organisms break down plant and animal debris they change the structure of the soil. Creatures like earthworms break down larger vegetative clumps into smaller clumps of organic matter, making the soil structure finer. In a good plant debris-based soil, the actions of earthworm, as well as the amount of organic matter, greatly increases the soil’s ability to hold nutrients and water, as well as structure (pores).
Soil lacking in oxygen, water, and organic matter would be very bare and devoid of biodiversity. The area would consist only of a few, very specific kinds of soil organisms and specific plants that could tolerate these challenging environmental conditions.
What Lives in Our Soil?
Can you think of any other examples of food webs? What are some reasons why a soil would not have a layer of organic matter or humus near the surface? What would be some environmental strategies to remedy such a soil? What would happen if a group from the soil food web (fungi, animals, plants, insects, earthworms) suddenly disappeared?
The goal of this activity is to discover what lives in soil. Students will select a location to collect a soil sample, return to the classroom, and thereby note a variety of characteristics of the soil (moisture content, texture, color, etc.).
- Small shovel(s) or trowel(s)
- 1-liter plastic freezer bags
- Plastic jars
- Magnifying glasses
- Permanent marker
- Map of school grounds, town, or county (geographically and by elevation)
1. Preparation :: Take note of locations that the students would be interested in taking samples from. Be sure to have a variety of locations:
- Garden or flower bed
- Wooded area
- Near a parking lot
- Near a sidewalk
- Turf (grassy area)
Have a table in the classroom or other open space ready for observing soils. If students will be drying soil, you’ll need a place where soils can be left for several days
Have students draw a map of the school grounds.
2. Digging Soil :: At each selected area, have students:
- Observe location and vegetation
- Describe location and vegetation orally
- Write about location and vegetation in journals
- Use trowel or shovel to collect several clumps of soil
- Place soil in freezer bags
3. Observations :: Place soil samples on table or other open space. Divide students into groups and distribute one soil sample bag per group. Observe characteristics of the soil
which may include:
- Other soil creatures
4. Record observations by location on chart (sample below). Predict from chart which soils might be best for growing crops.
- Develop an inquiry project to further investigate your prediction in step 4.
- Choose a soil organism and write an expository paragraph (include: name, appearance, role, supporting details, and conclusion).
- Think of three animals that live in the soil and the homes they build. Students draw a soil community that includes small creatures, creatures above the soil, and plants.
- Create an informative poster to illustrate the soil food webs (include at least five trophic levels).
You can learn more about the activities we undertook in STEM Club here: