Target Grade Level / Age Range:

3rd-5th Grade

Estimated Time:

2 hours plus observation time over three weeks.  


Through three activities, students will learn about how natural resources are used to produce food, the value of topsoil, and how farmers protect and conserve natural resources.   


Activity 1

  • Digital or Printed Copies of Iowa Ag Today, Issue 3
  • Pair of dice  

Activity 2

  • 1 plexiglass root observation box OR 2, 8 to 16-ounce clear plastic cups. If using cups poke small holes in the bottom for drainage.
  • 1-2 cups of topsoil, ideally taken from garden or field.
  • 1-2 cups of subsoil (dig at least one foot into the ground to ensure that you reach the subsoil)
  • Masking tape
  • 4 corn kernels and 4 soybean seeds (email to request free seeds) 
  • Soil Profile video

Activity 3:

  • Apple
  • Paring knife
  • Cutting board or plate

Activity 4:

Essential Files (maps, charts, pictures, or documents)


  • erosion: process of the gradual destruction or diminution of something; eroding or being eroded by wind, water, or other natural agents.
  • conservation: protecting and conserving natural resources such as soil and water. 
  • subsoil: layer of soil immediately below the topsoil. It is usually lighter in color, less fertile, and sticky in texture. 
  • Topsoil: top layer of soil. It is the most fertile layer of soil with the most nutrients for growing crops. Topsoil is rich in organic matter (decomposed plants and animals).

Background – Agricultural Connections

Nearly all food can be tracked back to soil. Fruits, vegetables and grains are grown in soil. Meat, eggs, and dairy products come from animals that eat plants that grow in soil.   

The Midwest is often referred to as the “breadbasket” of the United States or even of the world. This is because the Midwest has some of the best soil in the world, which is ideal for growing wheat, corn and other grains. Because of this, it is important that we protect our topsoil from wind and water erosion. 

Land that is tilled and left bare is more susceptible to erosion by wind or water. Topsoil that is washed or blown away can take decades to naturally replace. Excess nutrients applied to the soil can reach waterways through runoff and the groundwater.

It used to be common for farmers in Iowa to plow the soil in the fall or spring.  Plowing completely turns over the soil, leaving it exposed to wind and water. Topsoil, especially on hills, would blow or wash away. When Iowa land was first plowed, the settlers found 14 to 16 inches of topsoil. By 2000, the average was six to eight inches.

In the 1960s, farmers began using chisel plows to prepare the soil for planting. The chisel would make deep slits into the soil. This tillage method did not disrupt the soil as much as plowing, and enabled farmers to grow crops on hills without losing as much soil to wind and water erosion. Minimally tilling the soil is called conservation tillage. It is still used today when tilling is necessary.

Today, many farmers do not till the soil before planting. No-till farming is when farmers plant seeds directly into unbroken soil. Stems, leaves and roots from last year are left on the ground. This helps protect the soil from wind and water erosion. Earthworms and living soil organisms break down last year’s crop residue, providing for air and water movement through the soil and providing organic matter for a good environment for the seeds to germinate and crops to grow.

Farmers use many other conservation practices to keep the topsoil in place and keep nutrients from entering water sources. Cover crops planted on crop fields in the fall help protect our water from becoming polluted with sediment and nitrates. Terraces are used on hilly land to slow water down as it runs off the hill. Buffer strips and bioreactors are used to help filter sediment and nutrients out before it enters streams, ponds, and lakes.

Interest Approach – Engagement

Tell students that Iowa usually ranks first or second in producing four agriculture products. Then ask, “Do you know what they are?” If they are stumped, tell the class that two are crops (plants) and two are products from livestock (animals).  For at least the last 15 years, farmers in Iowa have produced more corn, pork, and eggs than farmers in any other state. Iowa usually ranks number one in soybean production too, but sometimes it is second behind Illinois. 

Then ask, “Why do you think Iowa is such a good state for growing crops and raising livestock? Iowa is a top agriculture state because of our climate and soil.


Activity 1: Natural Resources & Pizza (40 minutes)

  1. Independently or as a class, read page 1 of Iowa Ag Today, Issue 3: Iowa’s Invaluable Natural Resources, to learn more about Iowa’s natural resources. 
  2. Write two lists on the board.
    1. Ask the class to name the four natural resources discussed in the article. List them under the heading “Natural Resources,” and number them 1-4.
    2. Next, ask the class to name six pizza ingredients. List them under the heading “Pizza Ingredients,” and number them 1-6.
  3. Divide the class into pairs and tell them that they are going to do a Think, Pair, Share to discuss why each natural resource is needed for pizza.
    1. Ask for two volunteers to roll the dice.
      1. The first die will select the natural resource. If the volunteer rolls a 5 or 6, ask him/her to roll again.
      2. The second die will select the pizza topping. 
    2. Ask students to “think” about their answer independently for 15 seconds. Set a timer to keep track of the time,
    3. When the timer goes off, ask one person in each pair to share their answer. Reset the timer for 15 seconds for that person to share.
    4. When the timer goes off, give the second person in each group 15 more seconds to add to their partner’s answer. 
    5. Repeat steps 3a-3d until all of the pizza toppings and natural resources have been used at least once. Rotate which partner goes first and second each round. 
  4. As a class, review why each of the four natural resources are needed to make pizza.  

Activity 2: Topsoil vs. Subsoil Investigation  (20 minutes plus observation time over three weeks). This experiment is designed to illustrate the importance of topsoil.

  1. Nearly all food can be tracked back to soil. Fruits, vegetables, and grains are grown in soil. Meat, eggs, and dairy products come from animals that eat plants that grow in soil. Watch this video with students to introduce them to the importance of soil and the layers that make up soil.  .
  2. Explain to the class that they are going to do an investigation to compare two layers of soil – topsoil and subsoil. 
    1. As its name suggests, topsoil is the top layer of soil. Topsoil is the most fertile soil layer with the most nutrients and organic matter. Most farmland in Iowa has an average of 6 to 8 inches of topsoil.
    2. Subsoil is found directly under topsoil. It is usually lighter in color, less fertile, and sticky in texture.  
  3. Place topsoil in one half of the plexiglass root observation box or one of the plastic cups.
  4. Place subsoil in the other half of the root box or in the other plastic cup.   
  5. Write the date and type of soil on masking tape and place it on each cup or section of the box.
  6. Plant 2 kernels of corn and 2 soybeans about one each deep in the topsoil side of the box or in the topsoil cup. If using cups, be sure to plant the seeds next to the edge of the cup, so you can see the roots as they grow. 
  7. Water the seeds.
  8. Repeat step 5 in the subsoil side of the box or subsoil cup.  
  9. Place the box or cups in a sunny location that is above 60 degrees Fahrenheit. Water them when the top of the soil is dry to the touch. 
  10. Keep a journal and compare the plants in the topsoil and subsoil at least once a week for three weeks. Draw a picture of the plants and record the height of each plant, the number of leaves, length of the roots, etc. 
  11. At the end of week 3, gently remove the plants from the cups and wash away the soil.  Record final measurements and observations.
  12. As a class, discuss your observations. Do the plants growing in the subsoil or topsoil look healthier?  Why do you think this is the case? 
  13. The plants growing in the topsoil should look healthier because the topsoil contains more organic matter. Organic matter makes the topsoil more nutrient-rich, better drained than the subsoil.
    1. Remind students that all pizza toppings, except seafood, can be traced back to soil.
    2. Vegetables are grown in soil. 
    3. Wheat that is used to ground to make flour for the crust grows in soil.
  14. Dairy cows that produce milk for cheese eat corn, soybeans, grass, alfalfa, and other crops that are grown in soil. .
  15. Conclude reminding the students that Iowa has some of the earth’s best topsoil, which is why most the state is used for growing crops and raising livestock.

Activity 3: Apple Earth  (20 minutes)

  1. Ask the students, “How much of the world has topsoil that is suitable for growing crops?” (Hold up the apple) This apple represents planet Earth. We’re going to cut the apple into pieces to see how much of the Earth can be used to grow food for more than 7 billion people and all the animals in our care.
  2. Let’s start by thinking about water. How much of the world is water? Cut the apple lengthwise in four equal parts and take away three. These three parts represent the water on Earth.  3/4 or 75% of the Earth is made up of water. Ask students where we find water on planet Earth. (Oceans, rivers, revisions)
  3. How much of the land is too hot or too cold to grow crops? Cut the remaining quarter in half lengthwise and take away half. This half represents the areas on Earth that are too hot, too cold, or too wet for the plants we eat to grow. 1/8 of the Earth has land in a climate that is unable to grow or produce food.
  4.  Ask students what places are too hot?  (deserts and places near the equator.) What places are too cold? (The poles, places where there is frozen ground.) What places other than bodies of water are too wet? (Swamps and the rainforest.) Can we grow food on all of the remaining land? (Cut the remaining portion into four equal parts and take away three.) These three parts represent areas of Earth where the plants we eat can’t grow roots into the ground. We call these surfaces impervious, which means incapable of penetrating or being passed through. Ask students what things cover soil and make the ground impenetrable? (Roads, houses, businesses, shopping malls, schools, parking lots, mountains, forests.)
  5. The fourth portion – only 1/32 of Earth – represents the land that can grow crops for the 7+ billion people and animals on Earth.
  6. Can we grow food to the core of the Earth? No. (Peel the skin off the remaining section.) This skin represents topsoil, the part of the soil that plants grow in. This is the amount of soil on planet Earth that grows the food to feed all the people and animals that live around the world.
  7. Ask students if this is very much topsoil on planet earth to grow our food? (No.) Ask students if the amount of land with good topsoil on the Earth is getting bigger or soil?  It is getting smaller because land is being used for housing, businesses, schools, and other things that our growing population needs. The amount of topsoil on the land is also decreasing because of wind and water erosion. 

Activity 4: Conservation Practices (40 minutes)

  1. The last two activities taught us that good topsoil is needed to grow crops and that only a small portion of the earth has topsoil that is well suited for growing food for us and feed for livestock. Now we are going to learn what farmers can do to protect this valuable and limited resource—topsoil.
  2. Ask students for examples of how their families conserve natural resources? (Examples include recycling paper, turning off the water when brushing their teeth)
  3. Explain that overtime people have learned that conserving natural resources is important and they have changed how we do things in order to conserve and protect the environment. Science and technology have helped us conserve natural resources, too.  Discuss a few examples of environmentally-friendly technologies (Examples: include improved methods to recycle materials, water and energy-saving appliances, fuel efficient cars, programable thermostats, etc.) 
  4. Tell students that they are going to read about how farmers have changed how they cultivate, or till the soil, in order to protect it from wind and water erosion. Distribute copies of Iowa Ag Today, Issue 3 or share the link to the digital version. Read the title and introduction paragraph of Change Over Time (page 6) to the class, and then ask for volunteers to read the 200 Years Ago, 100 Years Ago, 50 Years Ago, and Today sections aloud. 
  5. On the board, begin a list of what farmers are doing to conserve and protect soil. Practices discussed in the article include conservation tillage, and no-till farming.    
  6. Next, ask students to read Farming Goes Digital (right side of page 2) and Farmers Care about Water and Soil…and You Should Too!  (Pages 4 &5)
  7. After they are finished reading, discuss new learning and add to the list of soil conservation practices on the board. To wrap up, ask students to write a paragraph to answer the question: How can farmers use technology and conservation practices to protect soil? Their paragraph should include evidence from the articles to support their reasoning.  

Did you know? (Ag facts)

  • Only 3% of the Earth’s surface, or 10% of the Earth’s land, is arable, or well-suited for growing crops.
  • Iowa has 55,875 square miles of land. Over 85% of Iowa’s land is used for agriculture. 
  • Science and technology in agriculture have increased crop yields, preserved and improved soils, and produced healthier foods.
  • Advanced conservation practices are used on more than 50 percent of U.S cropland acres.
  • GPS guidance systems reduce overlap, resulting in less trips across the field. This reduces soil compaction and the amount of fuel, seed, fertilizer and pesticides used. 
  • Soil tests analyze composition, nutrient content, pH, and other characteristics. Farmers use the results to determine the proper type and amount of fertilizer to apply.
  • Organic matter is an important part of soil, and it is made of things that were once alive.

Extension Activities

  • Have students practice retelling the apple activity to a partner or small group. Ask students to retell the story as homework and summarize one person’s reaction to the demonstration.
  • Invite a farmer or a local Natural Resources Conservation Service (NRCS) staff member to your classroom to discuss soil and water conservation practices on farmland.
  • Have students conduct research to learn more about one of the conservation practices introduced in the Iowa Agriculture Today articles. Write a paragraph describing specifically what the conservation practice does (cause) and what effect the practice is having.
  • Create a timeline using the photos from the Change over Time article in Iowa Ag Today, Issue 3.  Add more photos to show tillage tools used by the Iowa Indians in the 1700s and by farmers in the 1980s.

Suggested Companion Resources


Part of this lesson was adapted from activities in the Pizza-a-Thon Facilitators Guide created by Eldon Weber at Iowa State University.

The Apple Earth activity was adapted from the Where We Live curriculum by Iowa State University Extension.


Cindy Hall

Organization Affiliation  

Iowa Agriculture Literacy Foundation 

Agriculture Literacy Outcomes

  • T1.3-5.b. Explain how the interaction of the sun, soil, water, and weather in plant and animal growth impacts agricultural production
  • T1.3-5.c Identify land and water conservation methods used in farming systems (wind barriers, conservation tillage, laser leveling, GPS planting, etc.)
  • T1.3-5.e. Recognize the natural resources used in agricultural practices to produce food, feed, clothing, landscaping plants, and fuel (e.g., soil, water, air, plants, animals, and minerals)
  • T2.3-5.e Understand the concept of stewardship and identify ways farmers/ranchers care for soil, water, plants, and animals
  • T4.3-5.b Describe how technology helps farmers/ranchers increase their outputs (crop and livestock yields) with fewer inputs (less water, fertilizer, and land) while using the same amount of space 
  • T5.3-5.c. Explain how agricultural events and inventions affect how Americans live today (e.g., Eli Whitney - cotton gin; Cyrus McCormick - reaper; Virtanen - silo; Pasteur - pasteurization; John Deere - moldboard plow)
  • T5.3-5.f. Understand the agricultural history of an individual’s specific community and/or state

Iowa Core Standards

  • Science
    • 3-LS4-3. Construct an argument with evidence that in a particular habitat some organisms can survive well, some survive less well, and some cannot survive at all.
    • 3-ESS3-1. Make a claim about the merit of a design solution that reduces the impacts of a weather-related hazard.
    • 4-ESS2-1. Make observations and/or measurements to provide evidence of the effects of weathering or the rate of erosion by water, ice, wind, or vegetation.
    • 5-LS1-1. Support an argument that plants get the materials they need for growth chiefly from air and water.
  • Social Studies
    • SS.3.13. Identify how people use natural resources, human resources, and physical capital to produce goods and services.
    • SS.4.17. Create a geographic representation to illustrate how the natural resources in an area affect the decisions people make.
    • SS.4.25. Analyze the impact of technological changes in Iowa, across time and place.
    • SS.4.26. Explain how Iowa’s agriculture has changed over time.
  • English Language Arts
    • RI.3.1 Ask and answer questions to demonstrate understanding of a text, referring explicitly to the text as the basis for the answers.
    • W.3.8 Recall information from experiences or gather information from print and digital sources.
    • W.3.1 Write opinion pieces on topics or texts, supporting a point of view with reasons.
    • RI.4.1 Refer to details and examples in a text when explaining what the text says explicitly and when drawing inferences from the text.
    • W.4.2 Write informative/explanatory texts to examine a topic and convey ideas and information clearly.
    • W.4.8 Recall relevant information from experiences or gather relevant information from print and digital sources,
    • W.4.9 Draw evidence from literary or informational texts to support analysis, reflection, and research.
    • RI.4.7 Interpret information presented visually, orally, or quantitatively (e.g., in charts, graphs, diagrams, timelines, animations, or interactive elements on Web pages) and explain how the information contributes to an understanding of the text in which it appears.
    • W.4.7 Conduct short research projects that build knowledge through investigation of different aspects of a topic.
    • W.4.8 Recall relevant information from experiences or gather relevant information from print and digital sources.
    • RI.5.1 Quote accurately from a text when explaining what the text says explicitly and when drawing inferences from the text.
    • RI.5.7 Draw on information from multiple print or digital sources, demonstrating the ability to locate an answer to a question quickly or to solve a problem efficiently.
    • W.5.1 Write opinion pieces on topics or texts, supporting a point of view with reasons and information.
    • W.5.8 Recall relevant information from experiences or gather relevant information from print and digital sources.
    • W.5.9 Draw evidence from literary or informational texts to support analysis, reflection, and research.