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What is Soil? (FBCEC)

TopicGeology - Soils
Laboratory and Hands-on Activities - General
Summary
Most children give little thought to the soil we depend on. This activity will guide them to investigate their own soil samples and then plant seeds in them.
Recommended SettingIndoor and outdoor classroom
LocationFred Berry Conservation Education Center, Yellville, AR
Contact
Education Program Coordinator, 870-449-3484
Duration45 minutes - 1 hour
Suggested Number of ParticipantsUp to 20
Special Conditions
Weather Permitting
Objectives
  • Analyze and describe the composition of soil samples.
  • Collect and observe soil samples on site at FBCEC.
  • Discuss how soil is formed.
  • Recognize that life depends on soil.
Key Terms*

Clay

Humus

Loam

Mineral

Quartz

Sand

Soil

Materials

Beakers with water

Hand lenses

Hand trowel

Petri dishes

Samples of sand, loam and clay

Seeds for planting

Small cups

Spoons

Stereo microscopes

Toothpicks or forceps

Ziploc bags

Background

Humanity, in a sense, owes its survival to a few inches of topsoil. Soils are formed mainly by the breakdown of rocks, minerals and plants. Three basic soils are sand, clay and loam. Sand consists mainly of quartz particles, and clay is made up of extremely fine minerals that pack together. Loam is typically loose, rich soil with a significant amount of humus. The type of soil in an area can dramatically influence human activities such as development and agriculture.

Procedure
  1. Ask participants to name foods they enjoy. Tell them that much of what they eat is plants and that the animals (meat) they eat rely on plants for food. Ask, “What do plants need to live?” Even young participants will be aware that plants need soil. Briefly relate the discussion to our dependence upon soil.
  2. Ask participants to tell you what soil is made of. Invite them to examine the soil samples (sand, loam and clay) under the microscopes.
  3. Bring the class together to discuss what they learned. Bring out the similarities and the differences in the soil compositions. Sandy soils are mostly small grains of sand (quartz). Loam contains decaying plants (humus), and clay is made of tiny grains of mud-like particles. Briefly describe how these soils are formed, and then have participants speculate which type might be best for growing plants.
  4. Tell participants they will collect their own soil sample with a partner and bring it back to examine. Let them choose a site to collect the sample, and instruct them to use their trowel to scoop up about 2/3 bag of soil and seal their bag.
  5. Have them to keep their bags closed while looking at the sample. Ask them to describe the color and the texture (big particles, small ones, etc.). Note anything unique about the sample’s appearance. Have them open the bags and smell the soil. What does it smell like?
  6. Next, let them use microscopes to examine a spoonful of their sample and describe anything they find interesting. Is their soil most like sand, loam or clay?
  7. Give each participant a small cup and instruct the participant pairs to divide the remainder of their sample equally into the cups. Provide each participant with seeds to plant in the cups and then instruct them to lightly water the seeds. Let them label their container with their name and the seeds planted. They may take their planted seeds when they leave, and provide care instructions.
Modifications

For older participants (up to 8th grade), conduct a detailed analysis using soil test kits. Test factors like pH, nitrates, phosphates, etc. Discuss soil texture and color. If time allows, perform a second comparison with one sample from the bottomland field and one from the upland field. Discuss the habitats of those areas.

Review
  • Compare the appearance and composition of the sand, loam and clay samples.
  • Explain how soils are formed.
  • Describe the connection between soil and all living things.
Resources
  • Kohnke, Helmut and D.P. Franzmeier (1995). Soil Science Simplified, Waveland Press, Inc., Long Grove, IL.
  • Lavies, Bianca (1993). Compost Critters, Dutton Children’s Books.
  • United States Department of Agriculture – Natural Resources Conservation Service. http://soils.usda.gov/
Related Documents
Glossary

Clay – soil made of very fine particles, usually silicates of aluminum and/or iron and magnesium; absorbs water slowly and retains it for a long time

Humus – dark organic part of soil formed from decaying plants and animals, often called topsoil, which improves the soil’s fertility and water-holding ability

Loam – a rich, fertile soil containing clay, sand, silt and humus

Mineral
– a naturally occurring inorganic solid with a crystal structure and definite chemical composition

Quartz – a colorless or transparent mineral that can scratch steel and hard glass easily

Sand – a loose granular material disintegrated from rocks, consisting of particles smaller than gravel but courser than silt

Soil – the upper layer of earth that may be dug or plowed and in which plants can grow