By Phyllis Stewart’s Third-Grade Students, Horace Mann Montessori School, Dayton, Ohio
Editor’s Note: Originally published in Dragonfly Magazine in 1996, this vintage inquiry takes us back to a playground in Ohio, where a group of third graders turned a pile of yard waste into a seven month-long lesson on the power of decomposition.
The Spark
Have you ever seen a compost heap? We like to think of it as nature’s way of recycling. We wondered what would happen if we took the things falling from our trees—like leaves, grass, and sticks—and put them into a wire bin on our playground. We wanted to see if these materials would really change over time.
The Prediction
We weren’t all in agreement! Twenty-one of us thought the leaves, sticks, and grass would eventually turn to dirt. However, four of us thought the materials would stay exactly the same.
How We Investigated
To start our experiment, Mr. Stewart built a compost bin for us. We tied the bin to a drainpipe in a corner of our school playground and filled it to the top with leaves, grass, and sticks.
Every week, we had a routine: we stirred the contents with a stick and wet it down with water. Once a month, we went outside to observe the changes and use a yardstick to measure exactly how high the pile was. We even made a giant collage in class to describe our project as it happened.
What We Found
It turns out, the “Shrinking Heap” earned its name! We watched our pile go from 50 centimeters in October all the way down to just 2.5 centimeters by May.
| DATE | HEIGHT | CONDITION |
| Oct. 15, 1994 | 50 centimeters | The leaves were fall colors. |
| Nov. 15, 1994 | 40 centimeters | The leaves and grass were brown and dry. |
| Dec. 15 1994 | 25 centimeters | The leaves were dry and crumbly. The bark came off some of the sticks. |
| Jan. 15, 1995 | 11 centimeters | The grass could not be seen. The leaves broke into small pieces. The sticks were whole. The compost was beginning to get mushy. |
| Mar. 10, 1995 | 7.5 centimeters | The leaves were like brown flakes. |
| Apr. 3, 1995 | 5 centimeters | The sticks were beginning to get mushy. |
| May 5, 1995 | 2.5 centimeters | The soil was flat and a little lumpy. |
By the end, the leaves, grass, and sticks had completely turned into soil. We even planted a pumpkin seed in our new compost, and it grew into a healthy plant! We learned that “decompose” means to rot or decay, and that all living things will turn to soil when they die.
“I was surprised at how long it took for the leaves and sticks to change to dirt.” — Amanda Yocum (third grade student)
Go Wild: Your Turn
Can you make your own dirt? Different leaves fall apart at different speeds.
- The Challenge: Make small heaps with different types of leaves (like maple vs. oak) or other materials like paper and plastic.
- Predict: Which one will disappear first? How do you think temperature or extra water might change the speed?
- Track It: Use a ruler to measure your “shrinking heap” every month!
The Field Guide (Educator Sidebar)
- Subject/Grade Level: Life Science / 3rd Grade
- Inquiry Focus: Data Logging, Longitudinal Observation, and Experimental Design.
- The Science Behind It: Decomposition is the process by which organic substances are broken down into simpler matter. Microorganisms, fungi, and invertebrates (decomposers) release nutrients back into the ecosystem by consuming organic waste.
- Standards Connection: NGSS: LS2.B: Cycles of Matter and Energy Transfer in Ecosystems.
- Materials Needed:
- Wire compost bin
- Leaves, grass, and sticks
- Water and a stirring stick
- Yardstick for measurement
- Journal for recording observations