Get the Dirt on Soils – A Teaching Unit for Gr. 4-8


Soil, Dirt, Sediment – Are they all the same?

We call it soil when its in the garden, dirt when its on our clothes (soil our of place), and sediment when its in the river or lake. Its all the same.



At the end of this unit, students will be able to:

1) Explain why the study of soils is useful to humans.

2) List parts of an ecosystem.

3) List 5 factors that form soil and give examples of how each factor can influence soil formation.

4) Explain significance of soil texture.

5) Conduct an investigation to determine texture of a soil sample using the “feel method.”

6) Conduct an investigation to determine texture of a soil sample using the “soil sieve method.” (middle/high school students only)

7) Conduct an investigation to compare the permeability rates of different soil textures.

8) Conduct an investigation to compare the soils found at 2 or more different sites.

9) Give examples of how soil information is used to determine appropriate human land uses.  Define ‘human land use.’

10) Give examples of how soil texture and moisture influence the type of plant community that can be supported.



Soil is the foundation for civilizations. Fertile soils helped build the famous Roman, Greek, and Egyptian (Nile River civilizations of the past. Soil destruction or mismanage-ment was associated with the downfall (salt accumulation, erosion, topsoil loss, loss of fertility) of these same civilizations which good soils had helped to build. (Brady, 1974).


Soil is Part of all Terrestrial Ecosystems:

1. Energy – sunlight          4. Vegetation

2. Water                         5. Animals

3. Soil

Soil provides “habitat” for a plant


5 Factors of Soil Formation

1.       Weather/climate

2.     Underlying geology

3.     Biological organisms

4.     Topography

5.     Time - soils in U.P. are ~10,000 years old; soil forms at rate of 1 cm per 250-2,500 yrs


What Is Soil Made Of?

1. 45% Minerals (how do rocks break down to soil?)

2. 5 % Organic matter = decomposed plants & animals (how does this happen?)

3. 25% Water (where does this come from?)

4. 25% Air (how do you know this is there?)


Minerals or rocks break down due to air and water erosion; chemical breakdown due to lichen and weathering (freeze-thaw action).


Organic matter may be the smallest % but it is extremely important. OM is the result of the decomposition of dead plants and animals by many organisms. Organic matter adds nutrients to soil:          

worms          bacteria       protozoa      snails           slugs

slime            crickets       sow bugs      millipedes     ants

fungi (mushrooms are fruiting bodies of fungus. Penicillin was derived from a soil fungus)


Ants are the major mechanical modifiers of world’s soils.

Worms provide most soil fertility.


Water comes from precipitation (rainfall and snowfall)


Air fills the spaces between particles, until forced out by water.



Hands-On Nature by Jenepher Lingelbach   

¨      Forest Floor: Home of the Hidden Workers, p. 73-79

¨      Rotting Logs: Temporary Homes on the Forest Floor, p. 80-86

(note: many tree seedlings get their start on rotting logs, esp. yellow birch)


WOW! The Wonder of Wetlands

¨      Nature’s Recyclers p. 226


Soil Organism Diversity Study – the diversity and number of soil organisms in top 6” of a square foot of soil is determined by doing a species diversity study. Each group of 3 students, using a 4’ length of string tied into a circle, tallies the number and type of organisms they find. Combine all groups’ data into a bar graph.) 


Research the role of each soil organism found.




How Are Soils Described?

A) Soil Profile – soils are arranged in layers called horizons

1. Organic Horizon – plant and animals range from undecomposed to fully decomposed. Peat soils are 100% organic material found in bogs and fens.

2. A Horizontopsoil – Topsoil is the most important layer of soil because it can be modified by cultivation, erosion, fertilizer, and it is where the activity of soil organisms takes place.

3. B Horizon - Subsoil

4. C Horizon - unconsolidated parent material

5. Hard Bedrock


There are 20,000 soils in United States. Soils in the U.P. have been formed over the past 10,000 years since the last glaciation.


B) Naming of Soils – each soil type is named after the town where it was first described.  Michigan State Soil is “Kalkaska Sand.”


C) Physical Properties of Soils color, texture, drainage (infiltration rate), structure, depth


Soil Texture (or particle size) – all soils made up of clay, silt, sand; ~ equal parts of each is called loam. Soil texture influences: permeability, porosity, erodability.


Soil Texture can be determined by:

1)  “Feel Method” (see description on p. 238 of WOW! the Wonder of Wetlands) – using small amount of soil and water, try to ribbon out soil between your thumb and forefinger.

2) Soil Sieve Analysis – air or oven dry a sample of soil from each site. Measure a 100 gram sample and put into sieves. Shake sieves for 5-15 minutes. Weigh soil remaining on each of the bottom three screens. Calculate % sand, silt, clay. Determine soil textural type (silty loam, sandy clay, etc.) using Soil Triangle (attached) for how to name soil based on % of constituents.

Soil Sieve separation sizes:

¨       Trapped in top sieve = Gravel (> 4.0 mm)

¨       Trapped in second sieve = Granules (2.0 to 4.0 mm)

¨       Trapped in third sieve = Sand (2.0 mm to .05 mm)

¨       Trapped in the fourth sieve = Silt (.05 mm to .002 mm)

¨       In bottom pan = Clay (<.002 mm) clay has more useful plant nutrients than sand.


Pore spaces = space between soil particles. Number and size of pore spaces determine porosity and permeability rates of different soils. Compare size of pore spaces between gravel (basketballs) and sand (marble) particles.



Compare characteristics of different soil particles – sprinkle a sample of sand, silt and clay onto tape or glue on index cards. Note where soil sample taken from. Examine soil particle using a magnifier.


Compare erosion rate of 3 different soil textures - larger, heavier particle sizes require greater velocity wind or water to be moved. Use a small fan to blow different textures of soil. Or shake a soil sample containing different textures in a jar of water.  As water movement slows, the gravel will settle out first, followed by sand, silt, clay, and finally organic matter.


Compare permeability rates of gravel, sand, silt, and clay by pour water through a cup (with holes punched in bottom) of each and measuring the time it takes for the water to come out the bottom.


Compare porosity of sand, silt and clay – put equal amounts of each into 3 cups. Measure amount of water poured into each until the soil is saturated. Clay has more pore space, although the size of pores is smaller and capillary action (adhesion of water molecules to the clay particles) slows the movement of water.


Compare productivity of sand, silt, and clay by growing same types of seeds in each different soil texture. Be sure to plant seeds no deeper than the length of the seed.


Type of Soil Determines Suitability for Different Land Uses?

¨      What kind of crops will grow there (fertility) –farming, gardening, orchards

¨      Grasslands & pasture for grazing

¨      Type and productivity of different forest types – conifer, hardwood (see handout)

¨      Roads & building sites (sand is best)

¨      Whether it will erode—blow or wash away

¨      Wildlife habitat – grassland, forest, desert

¨      Wetland?

¨      Septic system possible? Landfill siting? (clay has very limited drainage; gravel and sand may drain too quickly)

Activity:  Investigate Soils at Three Different Sites



data sheet         soil auger          MSU Extension Tree ID Key or Treefinder

clipboard           can                   plastic gallon jug of water

pencil                soil sieve           meter stick

squirt bottle      shovel



1) Examine litter layer. What types of plant materials are present? How decomposed are they?


2) Record the dominant plant community at each site.


3) Sift through soil in top 10 cm. What soil organisms are present?


4) Record the color, moisture and smell of the topsoil.


5) Determine the texture of the topsoil using the “feel method.”


6) Describe the soil profile of the top two feet.  (Use soil auger & meter stick).


7) Compare the permeability rate of the soil at each site.


8) What is the depth to groundwater?

Soils Teaching Resources


Activity guides:

Hands-On Nature by Jenepher Lingelbach     

¨      Forest Floor: Home of the Hidden Workers, p. 73-79

¨      Rotting Logs: Temporary Homes on the Forest Floor, p. 80-86


Project Learning Tree (K-8)      

¨      Soil Stories, p. 252-257 (site characteristics, soil characteristics, air space, water movement)


WOW! The Wonder of Wetlands

¨      Nature’s Recyclers p. 226

¨      Do You Dig Wetland Soil? p. 231

¨      How Thirsty is the Ground? p. 239

¨      Nature’s Filter, p. 250


Dig In! Hands On Soil Investigations (K-4). National Science Teachers Assn.



Secondary Project Learning Tree – The Changing Forest: Forest Ecology

Soil Studies  p. 46-48


LaMotte Soil Tour – for conducting fertility analysis of different soils.



2001 Soil Planning Guide calendar – available from USDA/Natural Resources Conservation Service

 Magnifiers            Soil Survey for your county

White tubs            Soil Sorting Sieves (from Delta or Hubbell Scientific – get 5-6 trays!)

 Soil Auger            Shovel
Small ziploc plastic bags and marker for collecting and labeling soil samples                        

Music tapes

¨      Earthy Tunes by Mary Miche (Tel: 510-845-8417)                                   


Children's books:

A Log’s Life by Wendy Pfeffer  (ISBN 0-689-80636-1)                                            

Magic School Bus Hops Home---A Book About Animal Habitats  (ISBN 0-590-48413-3) 

Magic School Bus Meets the Rot Squad---A Book About Decomposition

(ISBN 0-590-40023-1) 

A Handful of Dirt by Raymond Bial. 2000. (ISBN 0-8027-8699-5)


Science Content Standards Addressed:


A. Science As Inquiry

¨      Ask a question about objects, organisms, and events in the environment

¨      Plan and conduct a simple investigation

¨      Employ simple equipment and tools to gather data and extend the senses

¨      Use data to construct a reasonable explanation

¨      Communicate investigations and explanations


C. Life Science

¨      Characteristics of organisms

¨      Organisms and their environment


D. Earth and Space Science

¨      Properties of Earth materials

¨      Changes in the Earth and sky


F. Science in Personal and Social Perspectives

¨      Types of resources

¨      Changes in environments

¨      Science and technology in local challenges


G. History and Nature of Science

¨      Science as a human endeavor


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