Ask each student to bring in a quart-sized plastic bag of soil. Provide trays with a lip for the students to examine their soil. Furnish magnifying glasses for the students to find the many different components of soil. They should find sand, bits of dried leaves and pebbles in their bag of soil. After giving the children ample time to examine their soil, conduct a class discussion. List on the board all of the items the students were able to identify in the bag of soil.
Different types of soils absorb water differently. Show this comparison to the students in your classroom. Have available a cup of sandy soil, clay soil and rich, fertile soil. Weigh the cup of soil in the cup. Punch two holes in the bottom of the cup with a pencil. Slowly pour four ounces of water into the cup. After the extra water drains from each cup, weigh the cups, again. Compare the water weights to their original weights. The cup of soil that increased in weight the most is the one that absorbed the most water. Ask the third-graders to explain how the amount of water the soil absorbs affects the plants trying to thrive in the soil.
Many books are written for the third-grade audience explaining the wonders of soil. "A Handful of Dirt" by Raymond Bial shows off the elements of soil that grow the food we eat. "Dirt: The Scoop on Soil" by Natalie Rosinsky shows the important role soil plays in providing food. Read the stories aloud to the third-graders to explore the many factors of soil with literature.
Composting is a way for third-graders to learn how food waste is turned into fertile soil. Obtain the help of the cafeteria manager, school janitor and parent volunteers to keep this program going. Ask a parent to build a compost pile for the school. Place buckets in the lunch room close to where the students typically throw their waste in the trash. Post daily what is accepted in the compost bin. Products like meat and grease attract too many wild animals and should not be placed in the compost bin. The third-grade class is responsible for taking the buckets to the compost bin. Have the class, janitors or parent volunteers turn the compost soil weekly. Use the soil that is made on flower beds around the school.