Soils — A Dirty Business, But Someone Has To Do It (PCEC)


This lesson will allow participants to test the physical characteristics of soils (texture, percolation, pH, presence of phosphorus, nitrogen, and potassium), analyze the data gathered, and make educated predictions about the effects those characteristics will have on the flora of the Cook's Lake Area. (Note: Several prerequisites are needed for this activity. The PCEC educator will explain these prerequisites when the activity is scheduled.)

Grade Level:

5 and up

Recommended Setting:

Indoor or outdoor classroom

Outdoor Activity:



Potlatch Conservation Education Center at Cook’s Lake, Casscoe


Education Program Coordinator, 870-241-3373


One to two hours

Suggested Number of Participants:

20 - 25

Special Conditions:

One adult supervisor per 10 students; outdoor activities, weather permitting.


  • Make accurate observations and predictions about a soil sample’s physical characteristics.
  • Analyze data and produce graphs that reflect the data gathered.
  • Apply test results to real-life activities in order to make an informed decision.

Key Terms*:


Chemical weathering



Horizon (A, B, C, R)





Mechanical weathering



pH scale




Sandy soil


*See glossary for definations


(Per group)

2 - 3 small shovels or garden trowels

4 2-liter clear cola bottles (cut in half)

Drip, drip, drip percolation rates of soil

Filter paper or paper towel

Magnifiers (dissecting scope if available)

Plastic beaker that measures 500 ml of water

Soil samples from two different areas

Soil test kit

Stop watch or watch with second hand


Most participants have had extensive experience with soil. They play in it and get yelled at for grinding it into their clothes, but they never realize how important it is to our existence. Soil is the foundation for life on Earth since it supports the plant life we use for food. Soil is not an inert material; it teems with life. It is the naturally occurring, loose (unconsolidated) covering on the Earth's surface made up of minerals such as sand, clay, silt, organic matter and organisms too small to observe with the human eye. It is formed by broken rock particles that have been altered by chemical and environmental conditions, weathering and erosion. The mixture of mineral and organic constituents are in solid, gaseous and aqueous states.


  1. Ensure that participants understand the terms and procedures for the field study. This information is contained in the handout, “Soils Field Study worksheet.” It can be provided, upon request, when the activity is scheduled.
  2. Participants should work in groups of four to six. The teacher should assign these groups prior to arriving at Cook’s Lake. This grouping will give each person a chance to be leader, recorder, materials gatherer, reader and expediter.
  3. Go over the handout to make sure they understand the terms and procedures described.
  4. Show the groups to the activity area, and explain all safety rules and time requirements for the activities included in the handout.
  5. Monitor participants, as needed.
  6. Collect equipment and materials.
  7. Discuss and compare findings from various sites.


Have participants analyze how well they predicted the types of plants/animals actually found in their soil sample areas and how well their samples actually drained.


Based on the analysis of the soil sample, what was the soil type?
Based on the analysis of the soil samples’ pH, what plants could have grown in the soil? Compare this with what was actually found at the soil sample site. (See table I and table II in participant worksheet.)

Participant Worksheets:

Soils Field Study Worksheet


Calcium – soft grey alkaline earth metal; the fifth most abundant element by mass in the Earth's crust that is essential for living organisms, particularly in cell physiology

Chemical weathering – breakdown of rocks, soils and minerals by atmospheric chemicals or biologically produced chemicals; also known as biological weathering

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

Erosion – the natural process by which the surface of the earth is worn away by the action of water, glaciers, winds, waves, etc

Horizon (A, B, C, R) – specific layer in the soil which measures parallel to the soil surface and possesses physical characteristics which differ from the layers above and beneath; horizon formation is a function of a range of geological, chemical and biological processes and occurs over long time periods

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
Legume – plant in the pea family (Fabaceae or Leguminosae) or a fruit of these plants; legume fruit usually opens along a seam on two sides; common name for this type of fruit is a "pod,” includes alfalfa, clover, peas, beans, lentils, lupins, mesquite, carob and peanuts

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

Magnesium – alkaline earth metal that constitutes about 2 percent of the Earth's crust by mass, making it the eighth most abundant element in the crust; a common additive to fertilizers

Mechanical weathering – breakdown of rocks and minerals by frost, wind and tree roots with no chemical alteration

Nitrogen – nonmetallic element that constitutes nearly four-fifths of the air, occurring as a colorless, odorless, almost inert diatomic gas in various minerals and in all proteins and used in important manufactured materials

Percolate – permeate or penetrate gradually

pH scale – measure of a liquid’s or solid’s alkalinity, represented on a scale of 0 to 14 with 7 being a neutral state, 0 the most acidic and 14 the most alkaline

Phosphorous – nonmetallic chemical element that has the symbol P and atomic number 15; normally a white phosphorescent, waxy solid, becoming yellow when exposed to light; poisonous and unites easily with oxygen so that it ignites spontaneously at room temperature

Potassium – light, soft, silver-white metallic element of the alkali metal group; oxidizes rapidly in air and reacts violently with water

Rhizobium – nitrogen-fixing bacteria of the genus Rhizobium that form nodules on the roots of leguminous plants, such as clover and beans

Sandy soil – soil with large particles that drain quickly and hold nutrients poorly; has a gritty texture formed from weathered rocks such as limestone, quartz, granite and shale

Sulfur – pale yellow, nonmetallic element occurring widely in nature in several free and combined allotropic forms; used in black gunpowder, rubber vulcanization, the manufacture of insecticides and pharmaceuticals and the preparation of sulfur compounds such as hydrogen sulfide and sulfuric acid