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 Do Plants Grow Taller Hydroponically Or In Soil?

By Lauryn B.

6th Grade SOAR, 1998




 The purpose of this experiment was to find out if radishes grow taller and have more leaves if grown hydroponically using the water culture method and grown hydroponically using the flood and drain method, or if grown "conventionally" in potting soil.

 I became interested in this idea when I saw an article in the newspaper about hydroponics a year ago.

 The information gained from this experiment will help farmers decide whether to use hydroponics to grow plants. It will be especially beneficial in our valley because growing plants hydroponically also saves water. People who live in large cities will also benefit from this data because you can grow plants hydroponically in very small spaces. This could also be useful in the limited area of a spacecraft, and on sea floor dwellings.




My hypothesis is that the plants grown using the water culture method will grow taller than the plants grown in soil or using the flood and drain system.

 I base my hypothesis on the fact that hydroponically grown plants’ roots are suspended in water and nutrients all the time, and air is bubbled to them, whether than being given the nutrients in small bursts. Also, the soil-grown plants are not receiving the nutrient solution in the same form.




The constants in this study were:

Type of plant, scarlet knight radish (trial 1) early scarlet globe (trial 2)

Approximate size when planting, 1.0 cm -1.5 cm (trial 1) 3.5 cm -4.0 cm (trial 2)

Amount of water when small, 30 squirts per day per quad

Amount of light, 14 hours per day

Size of growing quadrant in starting tray when small, 8 cm by 5 cm

Size of large tub, 19cm by 32cm

Amount of water given to soil plants, 200 mL per week

Times of flood and drain, 6:00-6:30 A.M., 5:00-5:30 P.M., 8:00-8:30 P.M.

 The manipulated variable was the growing medium. There were three experiment groups: potting soil, water culture, and flood and drain method.

 The responding variable was the height of the radish plants after 15 days.

 To measure the responding variable the height of the each plant was measured in cm to the top of the leaves from the shavings or soil every other day.







Grow Light




Large tubs (19 cm by 32 cm)


Rubber stoppers




Bottle (4 L size)


Air pump

16 L

Nutrient solution (ingredients in research report)

4 L

Potting soil

*2 sheets

Machinery cloth


Wood shavings


Spray bottle




Recording sheets


Bubble rock


Tubing connectors


Top loading balance


Paper towels



Well water

* The sheets need to be 90 cm by 30 cm, one having 6 mm by 6 mm holes, one having 1.2 cm by 1.2 cm holes.




Procedure for Starting Seeds:

  1. Fold two white Bounty paper towels in half.
  2. Fold the halves in half, nearly forming a square.
  3. Put each paper towel on a plate.
  4. Unfold each paper towel into halves.
  5. Put 20-30 seeds on each paper towel, making sure the seeds get on one of the quarter sheets only.
  6. Fold the paper towel back into fourths.
  7. Every day, give the seeds 30 ml of tap water
  8. When the plants have started to sprout, and have a stem about 1 cm long, transplant to sand (steps 9-15)
  9. Drill a hole in the bottom of each compartment (quad) of the starting tray.
  10. Fill the compartments to the rim with sand.
  11. Poke 2 holes on each end 1 cm deep, 1/4 cm away from the edge.
  12. Put 1 sprouted seed in each hole.
  13. Cover the seeds with sand.
  14. Turn the grow lights on at 6:30 A.M. and turn them off at 8:30 P.M. each day.
  15. Give each quad 30 sprays of water each day, 15 in the morning, and 15 in the evening.


Procedure for making Water Culture System:

  1. Attach the ends of the tubing to the tubing plugs of the air pump and bubble rock.
  2. Cut a piece of the smaller holed machinery cloth, so it will fit inside the tub, 2.5 cm up from the bottom.
  3. Make a hole in one side of the machinery cloth, so the bubble rock’s tube will fit through.
  4. Set the bubble rock in the middle of the tub.
  5. Set the machinery cloth in, making sure it’s not piercing the air tube.
  6. Put 2 cm of wood chip shavings on top of the mesh.
  7. Cut the piece of larger holed machinery cloth to a size that will fit directly on top of the shavings.
  8. Pour two liters of nutrient solution in.
  9. Poke four holes evenly spaced into the shavings.
  10. Take out the seedlings from the sand and put 1 plant in each hole.
  11. Put the mesh on the shavings, making sure the plants go through the holes.
  12. Turn on the air pump.


Procedure for making Flood and Drain System:

  1. Put a tubing connector into each rubber stopper.
  2. Attach the tube’s ends to the tubing connectors.
  3. Drill 1 hole in 1 side of the tub, 1cm up from the bottom of the tub.
  4. Drill a hole in the middle of the bottle’s lid.
  5. Insert 1 stopper into the hole in the tub.
  6. Put the other stopper into the hole in the bottle lid.
  7. Cut a piece of smaller holed machinery cloth, so it will fit inside the tub, 2.5 cm up from the bottom.
  8. Put 2 cm of wood chip shavings on the mesh.
  9. Pour in 2 L of nutrient solution, making sure the lid is on the bottle, so the nutrients can drain out.
  10. Poke 4 holes in the shavings, equally spaced.
  11. Put 1 plant in each hole and cover their roots.
  12. Cut a piece of larger holed machinery cloth, so that it will fit directly over the shavings.
  13. Set the mesh on the shavings, making sure the plants are through the holes.
  14. To flood, take the lid off the bottle, and pour the nutrients over the plants. Leave the bottle elevated above the tub. After 30 min., drain it.
  15. To drain, put the lid on fairly loosely, so air will be allowed to escape the bottle. Put the bottle lower than the tub.
  16. Flood at 6:30 A.M. and drain at 7:00 A.M.
  17. Flood at 5:00 P.M. and drain at 5:30 P.M.
  18. Flood at 8:00 P.M. and drain at 8:30 P.M.


Procedure for Soil System:

  1. Drill 2 holes in the middle of the short side on the bottom of 1 of the large tubs.
  2. Fill the tub with 5 cm of potting soil.
  3. Poke 4 holes into the soil.
  4. Put 1 radish seedling in each hole and cover it’s roots with soil.
  5. Every week give to the soil plants 200 ml of water.


Procedures for all Plants

  1. Turn on the grow lights at 6:30 A.M. and turn them off at 8:30 P.M. every day.
  2. Every other day measure every plant in centimeters from the shavings or soil.
  3. The plants will be transplanted to the hydroponic and soil systems when they are 1-1.5cm tall.

 Trial 2 Procedural Additions

  1. Soak wood shavings in well water for 24 hours prior to use. Change water 6 times to leach out any toxic compounds from the shavings.
  2. Plant seedlings in adult systems at height of 3.5-4.0cm.




Hydroponics is the science of growing plants without soil. It comes from the Latin word "hydro" meaning water and "ponos" meaning labor. William Gericke first used the word in 1937. The first record of hydroponics was the Hanging Gardens of Babylon, where plant roots were placed in running streams of water. It was also used in World War II, to grow food for the soldiers.


When using hydroponics, there are a variety of methods you can choose from. In water culture, the plant roots are suspended in nutrient solution, while air is pumped to them. There must be an air pump in this method, because plants will die if no air is provided for their roots. Water culture was the first hydroponics method used.

In the flood and drain method a nutrient solution is intermittently supplied to the plant’s roots. A bucket full of nutrients is connected by a tube to the tub where the plant’s roots are suspended. First, the nutrients in the bucket are drained into the bottom of the tub through a tube. This is done by holding the bucket higher than the tub. Then, after 30 minutes, the bucket is placed lower than the tub so all the nutrients drain out.

Aggregate culture is when the plants are grown in peat moss, sand, gravel, wood chips, etc. It is more common today than water culture.

There are also other methods such as the wick method.


 When growing plants inside, they may need grow lights. The lights should be no less than 60 cm above the plants, and sometimes a shade of tinfoil or plastic should be used to reflect the light. The lights should be on for 10-14 hours a day.

Advantages and Disadvantages

Some advantages of hydroponics are that soil is not needed, and the plants can be grown quickly and in small spaces. Hard work is also excluded. It also saves water and is easier to control pests. There are hardly any weed problems and nutrients can be recycled. The amounts of fruit are higher and there is better control of the environment.

Some disadvantages are that the systems can cost a lot, and that disease can spread easily between plants in the same system with the same nutrients. Also, not all plants can be grown hydroponically.

 Plants That Grow Well

 Some plants that grow well hydroponically are eggplants, peas, cherry tomatoes, beans, onions, radishes, carrots and cucumbers.

Nutrient Solution

 A common nutrient solution includes:

1 liter water

0.8 grams Calcium nitrate

0.2 grams Potassium nitrate

0.2 grams Potassium dihydrogen phosphate

0.2 grams Magnesium sulfate

Trace Iron phosphate

There are other formulations that include micronutrients. These are usually found in soil and water.


 All plants need water, air and sunlight to live. But, they also need a lot of nutrients. Nitrogen is needed for leaf and stem growth. Phosphorus helps fruit and flowers develop. The job of encouraging root growth is done by calcium. Copper and iron are needed in the production of chlorophyll. During the energy process of photosynthesis plant cells need potassium. Sulfur helps in production of plant energy. Maganese does the job of helping to absorb nitrogen. Zinc helps to transfer energy. Scientists aren’t sure why plants need boron, but they know that plants need a very small amount of it.

Nutrient Deficiencies

 If a plant has small and yellow leaves, it needs magnesium. If it has a phosphorus deficiency, it will be small and have dark leaves. If the plant’s growth is stunted it needs zinc. If the plant has a nitrogen deficiency, it will be small. If it needs boron, it will have brittle stems and the tips of the new leaves will be brown. If it needs calcium, its leaves will be curled at the edges and the younger leaves will be immovable. If it has a maganese deficiency, it will have poor growth and blooming. If the plant is lacking potassium, the old leaves will be yellow and curled, while the newer ones will droop. If the tips of its leaves are yellow and pale, it needs iron.


Hydroponics is a successful growing method. There are many different methods of hydroponics. Plants may need lights when grown inside. There are advantages and disadvantages to hydroponics. Only some plants grow well hydroponically. There are many different nutrient solution mixes. Plants need nutrients, and some times they may have nutrient deficiencies. All in all, hydroponics is very rewarding and fun, even though it may have a downside sometimes.




The original purpose of this experiment was to find out if plants would grow taller and have more leaves if grown hydroponically using the flood and drain method and the water culture method than if grown in soil.

 The results of the experiment were that the soil plants grew the tallest, having an average height of 5.75 cm at the end of 15 days. This was trial 1 data. The flood and drain plants grew to an average height of 3 cm in trial 1.

The water culture plants came in last with an average height of 2.5 cm in trial 1. In trial 2, the flood and drain plants grew the tallest, having an average of 8.25 cm. The soil plants grew 7.5 cm tall on average. The water culture plants grew only to and average of 2.25 cm.





 My hypothesis was the water culture plants would grow the tallest in trial 1. The results indicate that this hypothesis in should be rejected in trial 1 because the soil plants grew the tallest. In trial 2 my hypotheses was also rejected, because the flood and drain plants grew the tallest.

 Because of the results of this experiment, I wonder if the hydroponic systems were not set up correctly. During my research I found several sources that implied that hydroponic plants grew tall and well. Possible problems were that the amount of air in the water culture systems was not optimal, the nutrient mixes were lacking micronutrients, the wood shavings contained toxic compounds, or the plants were not adequately supported.

 If I were to conduct this project again I would do an interview of a hydroponics expert and learn more about building the systems before I started. I would analyze the well water for mineral content, and use a micro nutrient mix as well as a macro one. I would also use an inert support method such as vermiculite instead of the wood shavings.




Benefits of Hydroponic Food Production, [Online] Available, downloaded Dec.3, 1997.

Brooke, Lawrence L. "Hydroponics: A Global Perspective," [Online] Available, downloaded Jan. 14, 1998

Dickerman, Alexandre and John. Discovering Hydroponic Gardening. Santa Barbara: Woodbridge Press Publishing, 1975 p. 47-63

"Far-Out Dining," Newsweek Feb. 2, 1998, p. 8

"Feed Your Hydroponics", Mother Earth News . Feb.-March 1993: 36, 87.

Hanging Gardens of Babylon, [Online] Available, downloaded Dec. 3, 1997

Hershey, David R. Plant Biology, New York; John Wiley and Sons, Inc., 1995 pp. 144

"Hydroponics," World Book Encyclopedia, 1995.

Riedman, Sarah R. Gardening Without Soil, New York; Franklin Watts, 1979 p. 6-8, 10, 13, 19




Aggregate- In this method the plants are grown in gravel, peat moss, wood shavings, etc.

Cellulose- A type of plant material.

Flood and Drain Method- A hydroponic method where there is a bucket full of the nutrient solution connected to the tub with a bucket. The bucket is filled with a nutrient solution. Then the bucket is put higher than the tub, so that the nutrients drain down to the plant’s roots in the tub. After half an hour, the bucket is put lower than the tub, allowing the nutrients to drain out, thus giving air to the roots.

Hydroponics- The science of growing plants without soil.

Macro Nutrients- Nutrients that plants need in large amounts.

Micro Nutrients- Nutrients that plants need in small amounts.

Nutrients- Things that provide nourishment.

Plant- A living being, that has cellulose cell walls, and no power of movement.

Soil- The top layer of the earth’s surface, in which you can grow plants

Water Culture- A hydroponic system in which the plant’s roots are suspended in a nutrient solution. There is also an air pump to aerate the roots.

Wick Method- This is where the plant’s roots are suspended above a tray of nutrient solution. There are wicks connecting the roots and the tub of nutrients, so the wicks draw the nutrients up to the roots.

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