Proving that healthy soil grows healthy plants

The goal of this experiment: To show how soil quality affects the growth of a plant and its roots.

What we know: To grow strong and healthy, a plant needs sunlight, water, and nutrients from the soil. A soil that is enriched with compost will provide extra nutrients, which the plant can absorb through its roots.

The experiment: In one container you will use plain soil, and in another you will mix the same soil with an equal amount of compost. You will then plant seeds and observe what happens to the plants above the soil and the roots in the soil.

Now print this page, turn off your computer, and start experimenting!

Step 1. Wrap aluminum foil around the outside of both containers, and then punch holes in the bottom of both. If you're using plastic bottles, first have a parent help you cut off the top 1/3 of the bottles.

Step 2. In the dishpan or bucket, mix together equal amounts of soil and compost — enough to fill one of the containers. If you have any soil/compost mixture left over, use it in your garden.

See the difference: The bottle on the left has rich compost added to the soil.

Step 3. Fill the other container with soil only. Label the containers.

Step 4. Plant some seeds in each container. Place both of the containers in the same sunny location. Water whenever the soil feels dry to the touch.

Step 5. Watch the seeds grow! Allow the seeds to grow for 4-8 weeks, checking on them from time to time to see which container is growing better plants. Take off the foil and check the roots, too (then put the foil back on).

Observe and draw conclusions:
• Which container grew healthier plants? Why?
• Do the roots in each container look different from each other? Explain.