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Hydroponics: The Science of Soilless Gardening

Difficulty
Time Required Very Long (1+ months)
Prerequisites None
Material Availability You must purchase a hydroponics kit. See the Materials and Equipment list for details.
Cost Average ($50 - $100)
Safety Use gloves and safety goggles when handling chemicals. Adult supervision is required.

Abstract

Have you ever planted a garden? It is a real pleasure to see a garden where all of the plants lie in neat rows and are healthy and thriving. However, it can be very frustrating when your garden doesn't thrive. There are numerous causes that prevent a plant from thriving. Perhaps the soil is not rich enough with nutrients or maybe pests are present in the soil that are sapping the seedling's energy. Soils also carry fungi that can attack a young seedling. What if you could avoid some of the causes that prevent a plant from thriving? In this plant biology science project, you will learn about hydroponics, the science of growing plants without soil, but with nutrient-rich water.

Objective

To compare the rate of growth and plant vigor of hydroponically grown plants to plants grown conventionally, in soil.

Credits

Michelle Maranowski, PhD, Science Buddies

Cite This Page

MLA Style

Science Buddies Staff. "Hydroponics: The Science of Soilless Gardening" Science Buddies. Science Buddies, 15 Oct. 2013. Web. 22 Sep. 2014 <http://www.sciencebuddies.org/science-fair-projects/project_ideas/PlantBio_p044.shtml>

APA Style

Science Buddies Staff. (2013, October 15). Hydroponics: The Science of Soilless Gardening. Retrieved September 22, 2014 from http://www.sciencebuddies.org/science-fair-projects/project_ideas/PlantBio_p044.shtml

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Last edit date: 2013-10-15

Introduction

You probably know that just as we get our nutrients from food, plants get their nutrients from the soil. Soil can contain macronutrients (like carbon, nitrogen, and phosphorus) and micronutrients (like iron, sodium, and zinc) that are both essential in order for a plant to thrive. Water is also essential and is used in many ways by plants. First of all, water acts as a solvent and helps to transport nutrients from the soil throughout the plant. Water-filled cells help support various biochemical reactions in the plant. A biochemical reaction is a reaction that occurs between chemicals to support the life of the plant. When a plant doesn't receive water, these biochemical reactions stop, the plant begins to turn yellow, dry up, and then die. So is soil really necessary for a plant to survive, or can they survive in just water? What if the water had all of the nutrients in it that soil does? The answer to this question is yes, plants can survive without being planted in soil. Hydroponics is the science of growing plants in nutrient-rich water. The word hydroponics means "working water" and comes from the Latin words hydro, meaning "water" and ponos, meaning "work." In hydroponics, the nutrients are available at the plant's roots. This allows the plant to gets its food and nutrition with no work. A plant with roots in soil has to work hard to extract its nutrition from the soil and it can waste a lot of energy doing that. But a plant in nutrient-rich water can spend its energy growing bigger leaves, fruits, and flowers in a shorter amount of time. One benefit of growing plants hydroponically is that the nutrients in the water can be completely controlled and the plant can receive exactly the right amount of nutrients at exactly the right time. Another benefit of hydroponics is that it can be used in areas where the soils are not arable (not suitable for farming) and in areas where there is no soil. Figure 1 shows a NASA scientist examining hydroponically grown plants.


Plant Biology science  project <B>Figure 1.</B> NASA plant <B>physiologist</B> at Kennedy Space Center examining his hydroponically grown plants. (NASA, 2004.)
Figure 1. NASA plant physiologist at Kennedy Space Center examining his hydroponically grown plants. (NASA, 2004.)

There are six basic types of hydroponic systems: wick system, water culture system, ebb-and-flow system, drip system, nutrient-film technique, and the aeroponics system. Each system has its advantages and disadvantages. In this plant biology science project, you will experiment with the water culture system and perform your own hydroponics experiment. You will compare the growth rate of peas that are grown in potting soil and peas that are grown hydroponically. Which method will produce seedlings the fastest? Will there be a difference in root growth between the two methods? At the end of this science project, instead of having a "green thumb" you might have a "blue thumb"!

Terms and Concepts

  • Macronutrient
  • Micronutrient
  • Solvent
  • Cell
  • Biochemical reaction
  • Hydroponics
  • Arable
  • Physiologist
  • Water culture system
  • Aerate
  • Data

Questions

  • What are the differences between a macronutrient and a micronutrient?
  • You might think that hydroponics is a new way of growing plants, but it isn't. What ancient cultures reportedly used or mentioned hydroponics? How old is the science of hydroponics?
  • Why is NASA interested in hydroponics? What kinds of hydroponics experiments do NASA scientists perform?
  • What are the differences between the six basic types of hydroponic systems? What are the advantages and disadvantages of each?

Bibliography

For help creating graphs, try this website:

Materials and Equipment

  • Hydroponics experiment kit; available from Sargent Welch, www.sargentwelch.com, part #WL9195B. This kit comes with different chemical nutrients, two culture chambers with one vented top, two germinating floats, germinating plugs, two cardboard sleeves, and assorted seeds.
    • Check to see if there is a packet of pea seeds in the assortment of seeds that came with the kit. If you didn't receive pea seeds, then go to your local gardening store or plant nursery and purchase a packet of pea seeds.
  • Distilled water
  • Aquarium pump with fitting tubing and air stone. Available at your local pet store or fish supplies store or through an online supplier such as Carolina Biological Supply Company, item #671720.
  • Disposable gloves. Can be purchased at a local drug store or pharmacy, or through an online supplier like Carolina Biological Supply Company. If you are allergic to latex, use vinyl or polyethylene gloves.
  • Glass stirring rod; available from online suppliers such as Carolina Biological Supply Company, item 711305
  • Small table
  • Seedling mix; special kind of potting mix available at gardening stores and plant nurseries
  • Terra cotta pots, 3-inch (10)
  • Hand trowel
  • Watering can
  • Lab notebook
  • Ruler with millimeter markings
  • Graph paper

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Experimental Procedure

Setting Up the Hydroponic Experiment

  1. Read the entire instruction booklet that comes with the hydroponics kit.
  2. Follow the instructions and mix the basic nutrient solution. Put on a pair of disposable gloves. Pour the amount of distilled water recommended in the instruction booklet into a culture chamber. Add the recommended amount of chemical nutrients into the culture chamber. Use the glass stirring rod to mix the nutrients into the distilled water.
  3. You will use the air stone to aerate the nutrient-water solution. If your tubing is very long, use the scissors and cut a 2-ft. length of tubing. Your air stone should come with fittings. If it is not already connected, take a moment to attach one end of the tubing to the fitting in the air stone and set it aside.
  4. Place six pea seeds into six germinating plugs. The germinating plugs came with the kit and are the small cylindrical pieces of foam.
  5. Insert the germinating plugs with the pea seeds into the middle and top rows of the germinating float. Label each plug and note the locations in your lab notebook. To make it easy to remember, draw a diagram in your lab notebook and label each location.
  6. Place the air stone, with the attached tubing, at the bottom of the culture chamber. Thread the tubing through the larger hole in the geminating float and then through the vented cover, as shown in Figure 2, below. Place the germinating float into the culture chamber. Make sure that the germinating plugs are in contact with the nutrient-water solution. Attach the other end of the tubing to the aquarium pump. The tubing should hang over the edge of the culture chamber. Put the chamber into the cardboard sleeve to prevent the growth of algae in the solution. Place the culture chamber with the seeds and air stone on the table and cover the chamber with the vented cover.


Plant Biology science fair project   <B>Figure 2.</B> This image shows the air stone in the culture chamber and the tubing coming out of the larger hole.
Figure 2. This image shows the air stone in the culture chamber and the tubing coming out of the larger hole.


  1. Place the table in a south or west window that gets plenty of light. If direct sunlight is unavailable, use a grow lamp to provide light for the seeds. Figure 3 shows the completed culture chamber.


Plant Biology science fair project   <B>Figure 3.</B> The completed culture chamber.
Figure 3. The completed culture chamber.


  1. In your lab notebook, note down the date that you set up the culture chamber with the seed plugs.

Setting Up the Soil Experiment

  1. Now start ten pea seeds in the ten pots. Using the hand trowel, place some seedling mix into each of the pots. Place a pea seed into each of the pots at the depth recommended on the seed package and make sure to cover them with soil.
  2. Water each pot carefully so that a little bit of water comes through the hole at the bottom of the pot. Make sure to water the pots over a sink. Do not over-water the seeds.
  3. Place the ten pots at the same location as the hydroponic culture chamber. Numerically label each pot and note down the labels in your lab notebook.
  4. In your lab notebook, record when you started growing the pea seeds in the pot, the depth at which the seeds were planted, and the brand of seedling mix that you used.

Running the Experiment

  1. The plants need the nutrients in the solution and the gases in the air to thrive. The roots of the growing seedlings need oxygen or the plants will drown. The pump and the air stone serve to add oxygen to the nutrient solution. Once every morning and afternoon, plug the pump into an outlet and aerate the water in the hydroponically grown peas, as follows. Run the pump for 2 minutes, once every morning and afternoon. The nutrient solution will bubble while you have the pump plugged into the outlet. You can take your table closer to an outlet for aerating if your sunny location is not close to an outlet. Unplug the pump and return the table to the sunny location when the aeration is complete.
  2. Check the soil of the pea seeds in the pots. Do not let it get dry, but it should not be too wet either. If the soil is dry, use the watering can and water the pot(s). Water the pots until a few drops of water come out from the bottom of the pot.
  3. Check the seeds in the culture chamber and the seeds in the pots every day at about the same time. Check to see how the seeds look in the culture chamber. Note down the date the seedlings sprouted. Are any roots growing? How many seeds have put out roots or leaves from the culture chamber or the pots? How long are the roots? Use the ruler to measure the length, in millimeters (mm). Note:You will have to sacrifice four of the soil-grown plants to record the growth of their roots. Choose special days to uproot a soil-grown plant. For example, you might want to look at the roots of a plant a few days after it sprouts and then a week after it sprouts. How many leaves have the seedlings put out from both the culture chamber and the pots? How big are the leaves? How tall is the seedling? Use the ruler to measure the height. Record all of your observations in data tables in your lab notebook, like the ones shown below.

Start Date of Culture Chamber: ________________
Date Observations
Plug 1 Plug 2 Plug 3 Plug 4 Plug 5 Plug 6
       
       


Start Date of Potting: ________________
Seedling Mix: ________________________   Seed depth: _____________
Date Observations
Pot 1 Pot 2 Pot 3 Pot 4 Pot 5 Pot 6Pot 7 Pot 8 Pot 9 Pot 10
           
           
  1. Keep checking and making observations of the culture chamber and the pots for two weeks. Add nutrients to the nutrient solution along the way, as recommended in the instruction booklet.

Analyzing Your Data

  1. After two weeks, review the data that you have collected. Plot the data that you have gathered on a graph. Make a plot of when the seedlings, both hydroponically grown and soil-grown, sprouted. Use graph paper to make your plots or, if you prefer, you can make your plots online with a website like Create a Graph. Label the x-axis Date and the y-axis Plant. For each plant, hydroponically and soil-grown, plot the date when it sprouted.
  2. Plot the length of the roots of the hydroponically grown plants for each day of the two-week period. Label the x-axis Date and the y-axis Root Length, in Millimeters (mm). How much do the roots of the hydroponically grown plants vary in length at the end of the two weeks?
  3. Compare the root length of the hydroponically grown plants to the root length of the soil-grown plants. First make a plot similar to the one in step 2 of this section for the soil-grown plants. How does the root growth between the two differently grown plants compare?
  4. Compare the heights of two hydroponically grown plants and two soil-grown plants for each day of the two-week period. Label the x-axis Date and the y-axis Height, in Millimeters.

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Variations

  • Grow different varieties of peas hydroponically. Do all varieties grow better hydroponically or does it depend on the variety?
  • Instead of growing peas, try growing different seeds hydroponically. Grow corn or flowers, both hydroponically and in soil. Is there is a difference between the hydroponically grown corn (or flowers) and soil-grown corn (or flowers)? Is it better to grow seeds and plants hydroponically or do some plants grow better in soil?
  • What happens if you don't have a balanced nutrient-water solution to grow plants hydroponically? Follow the directions given in the instruction booklet and vary the amounts of nutrients in the nutrient solution and see how it affects the growth of the plants.

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