Exploring the Rate of Plant Growth in Crystals vs. Soil

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Updated on Jul 22, 2013

In this project, measure the rate of growth of a bean seed or young plant placed in a superabsorbent crystal medium to that of a simular plant placed in soil. These crystals canstore water in the soil and then release it as the plant’s roots need it.Learn about the possible application of hydrogel superabsorbent crystals in forestry, gardening, and landscaping as a means of conserving water.

Ahydrogel superabsorbentcrystal is long chain of molecules called apolymer, that can absorb vary large amounts of water.This ability to hold water makes it an ideal medium for seed germination and plant growth.The research aspect of this science fair project is to compare the rate of plant root growth in water absorbing crystals to that of soil.

Placing a plant seed or the roots of a small growing plant into a container of these crystals allows water to be absorbed by the plant’s roots as it is needed. These crystals function similar to hydroponics, which is the growing of plants in water instead of soil. The difference between the two activities is that for hydroponics to be successful, the water must be enriched with nutrients and sometimes oxygenated. Also, the plants must be placed in some type of inert medium like sand, vermiculite, or sawdust to provide mechanical support in order to anchor the roots. The physical structure of the crystals used in this science fair project serves as the anchor, soexternal support is not necessary.


  • Hydrogel superabsorbent crystals
  • Metric ruler
  • Potting soil
  • Clear plastic cups
  • Fertilizer or liquid minerals
  • Fast-growing plant seeds (grass, radish, or beans).

Research Questions

  • What is a hydrogel crystal?
  • Will a plant grow in a hydrogel crystal medium the same as in soil?
  • Under similar conditions which plant grew at a faster rate?
  • At the completion of the project which plant grew to the greatest height?
  • How is a hydrogel crystal growth medium similar to hydroponics? How are they different?
  • What are the practical uses for hydrogel crystals in forestry, gardening, and landscaping?


  1. Fill a clear large plastic cup with water.
  2. Place five to ten crystals in the water. The crystals will begin to grow immediately.
  3. Allow the crystals to grow to a point where they cannot be seen inside the cup
  4. Add a little fertilizer or liquid minerals to the crystals.
  5. Fill another cup with potting soil and dampen with water.
  6. Place 2 or 3 beans seeds or one small bean plant into both cups.
  7. If small plants are being used instead of seeds they should be of the same approximate height. Place the roots under a gentle flow of water from the faucet to clean off as much dirt as possible. Or, work the dirt loose in a bucket of water.
  8. The roots only should be submerged in the crystals.
  9. Place both cups in the Sunlight or under an electric lamp.
  10. As the seeds germinate and/or the plants grow measure and record their height in a table like the one below.

Height in Centimeters

Plant Root Growth Medium

Day 0

Day 2

Day 4

Day 6

Day 8

Mike Calhoun is a consultant for the National Science Teachers Association, a veteran science teacher, and hosts an online science website. Over the years Mike has studied trends in science, education, and finance, conducting research, developing programs, and writing articles on these topics.

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