Here we’ll show you two science fair project ideas you can use with soil for your science fair project.

Soil is all around us: it nourishes the plants we grow, which then nourish our bodies. And, when we eventually die, our bodies in turn nourish the soil.

Great science fair projects often come from taking something that is all around us, like soil, and investigating how it works.


Project #1:
Water Retention- Which Type Of Soil
Holds the Most Water

These science fair project ideas investigate how different kinds of soil hold water. As you know, water is one of the basic building blocks of all life, so it needs to be present in rich, fertile soil. How does soil hold onto water, and which kinds of soil hold the most water?


    • Peat moss (humus) – available at your nursery or hardware store
    • Sand
    • scissors
    • 3 coffee filters
    • craft knife or screwdriver
    • permanent marker
    • 6 large, clear plastic disposable cups
    • ruler
    • measuring cup
    • large mixing bowl



1. Come up with your hypothesis – do you think that the most water will be held by sand, humus, or a mixture of the two? Why?

2. Using the knife or screwdriver, make three small holes in the bottom of 3 of the cups.

3. Trace the bottom of the cups onto the coffee filters and cut out the circle

4. Moisten the filters, then place a filter in the bottom of each of the cups with the holes in them.

5. Pair up your cups so that each pair has one cup with holes and one without. Label one pair “sand,” one pair “humus,” and one pair “mixed.”

6. Measure out an equal amount of sand and humus into the proper cups. The soil should be in the cup with the holes. The cups without holes should be empty.

7. Place roughly equal amounts of sand and humus in the mixing bowl and mix until even. Spoon out an amount of this mixture equivalent to the amount of soil in the other cups. Place the mixture in the appropriate cup.

8. Hold the cup with the sand in it over the empty “sand” cup and add ¾ cup (6 ounces) of water. Measure the level of water that pours into the empty cup.

9. Repeat step 8 2 more times with the other soil types

10. Compare the amount of water in each of the cups. Which soil type let the most water through, and which one held onto the most? Why do you think this happened?



Project #2:
Soil and Salinity Experiment

These science fair project ideas look at what happens when chemicals are introduced to soil. In this case, we’ll be looking at the effect of salinity, or the level of salt in the soil.


    • 12 radish seeds
    • 2-3 cups of potting soil
    • water in a spray bottle
    • egg carton for 1 dozen eggs
    • cafeteria tray or baking sheet with raised edges
    • fork
    • salt
    • permanent marker



1. Come up with your hypothesis – do you think plants will grow best with lots of salt, no salt, or a medium amount?

2. Use the fork to poke small holes in the bottom of the egg wells so that they can drain.

3. Separate the egg carton into 3 sections using the marker. Each section should have 4 egg wells. Label one “Low salinity,” one “medium salinity,” and one “high salinity” Number each of the egg wells 1-12. Put 1-4 in “low salinity,” 5-8 in “medium,” and 9-12 in “high”

4. Draw up a data sheet with 12 rows. Label each of the 12 rows as either “high,” medium,” or “low.”

5. Fill each egg well about ½-¾ of the way up with soil. Sprinkle a pinch of salt into each of the egg wells in the “medium salinity” section. Use your fingers to mix the soil up and spread the salt around.

6. Put ½ tablespoon of salt into each of the egg wells in the “high salinity” section. Mix well.

7. Bury a radish seed in each egg well (not too far from the surface), then add another thin layer of soil. Each seed should have the same amount of soil.

8. Spray some water over the egg carton, making sure that each egg well gets moist, but not soaking.

9. Place the tray in a warm place with plenty of sunlight.

10. For the next 2 weeks, return once a day to water the plants and record the progress of each of the radish seeds.

11. Does your data match your expectations?

Did you notice a similarity between these two science fair project ideas? Can you come up with another idea for a science fair project that combines the concepts in Experiment 1 with the methods in Experiment 2?


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