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Botany Science Fair Project

The Soil Moisture Mystery

The Soil Moisture Mystery | Science Fair Projects | STEM Projects
Join us in this experiment to find out if earthworms and water can help plants grow. We'll be testing the effects of soil moisture and earthworms on the growth of beans.


The hypothesis is that the bean plants with the earthworms will grow taller.

Method & Materials

You will place 220 g of potting soil in each of the six pots, label them, add four earthworms to each pot, drop one lima bean in the holes, cover the seeds with the soil, pat the soil down, and water the plants with different amounts of water.
You will need 18 whole lima beans, 5,400 mL of tap water, 6 plant pots, 1,320 g of potting soil, 12 earthworms, 1 bottle of "Schlutz Plant Food", 1 bucket that can hold 1,000 mL, and 1 measuring cup.


The results of the experiment showed that the average height of the plants of the "Moist" (100 mL) groups was greater than any of the other groups. The groups with the least amount of growth were the “Very Wet” groups. The worms must have helped because the plants in “Dry with worms” (50 mL) grew rather high even though it had a lack of water.

Why do this project?

This science project is interesting because it can help farmers living in areas of low rainfall to learn how to keep their plants alive.

Also Consider

Experiment variations to consider include testing the effects of different types of soil and different types of worms.

Full project details

You can find additional information and details for this science fair project here. Have fun exploring!

Related video

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