Hydroponics: Gardening Without Soil

Abstract

What do plants need to grow? Most of us would answer that they need light, air, water, and soil. But by using a process called hydroponics, you can grow plants without soil! How does it work? Try this project and see for yourself!

Summary

Areas of Science

Plant Biology
Agricultural Technology

Difficulty

Method

Scientific Method

Time Required

Long (2-4 weeks)

Prerequisites

None

Material Availability

A kit is available from our partner Home Science Tools®. See the Materials section for details.

Cost

Average ($40 - $80)

Safety

Handle chemicals with care including wearing gloves. Adult supervision is recommended.

Credits

Laura Ohl, PhD, Science Buddies Alumni

Sabine De Brabandere, PhD, Science Buddies

Michelle Maranowski, PhD, Science Buddies

Science Buddies is committed to creating content authored by scientists and educators. Learn more about our process and how we use AI.

https://www.youtube.com/watch?v=mJCtvZskziI

Objective

Compare the rate of growth of hydroponically-grown plants with and without nutrient-rich water.

Introduction

You probably know that just as we get our nutrients from food, generally plants get their nutrients from the soil. To thrive, plants need both macronutrients (like carbon, nitrogen, and phosphorus) and micronutrients (like iron, sodium, and zinc). Soil can contain all of these, but purified water does not.

Plants also need water and use it in many ways. First, water acts as a solvent and helps to transport nutrients from the soil throughout the plant. Second, water-filled cells help support various biochemical reactions in the plant. A biochemical reaction is a reaction that occurs between biological molecules inside a plant's cells to keep them alive. A plant biochemical reaction that you may have heard of is photosynthesis. Photosynthesis is a reaction involving sunlight, the chlorophyll in plant cells, water, and carbon dioxide. It produces sugar for the plant to use as food. When a plant doesn't receive water, photosynthesis and other biochemical reactions stop, the plant begins to turn yellow, dries up, and then dies.

So is soil really necessary for a plant to survive, or can plants 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. The science of growing plants in nutrient-rich water is hydroponics. 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. So, with little work, the plant gets its food and nutrition. A plant with roots in soil has to work hard to extract its nutrition from the soil, and it uses a lot of energy to be able to do that. Conversely, if a plant's roots are in nutrient-rich water, it expends less of its energy extracting those nutrients so it can conserve its energy and grow bigger leaves, fruits, and flowers faster. 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 when they need them for growth or flowering. Another benefit of hydroponics is that it works in areas where the soil is not arable (not suitable for farming) and in areas where there is no soil. Figure 1 shows a NASA scientist examining hydroponically-grown plants.

Image Credit: National Air and Space Administration, Kennedy Space Center / Public domain

Figure 1. A 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 wick system and perform your own hydroponics experiment. You will compare the growth rate of basil or lettuce seeds grown hydroponically, one set with nutrient-rich water and the other with plain water. Which method will produce seedlings the fastest? Will one method yield more vigorously growing plants compared to the other? 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
• Photosynthesis
• Chlorophyll
• Hydroponics
• Arable
• Physiologist
• Wick system
• Water culture system
• Aerate
• Area
• Ellipse

Questions

• What ancient cultures reportedly used or mentioned hydroponics? How old is the science of hydroponics?
• What are macronutrients, and how are they different from micronutrients?
• What is hydroponics, and how do these systems work?
• What are the differences between the six basic types of hydroponic systems? What are the advantages and disadvantages of each?
• Why is NASA interested in hydroponics? What kinds of hydroponics experiments do NASA scientists perform?
• What is the advantage of using hydroponic systems compared to traditional growing methods

Materials and Equipment

Recommended Project Supplies

Get the right supplies — selected and tested to work with this project.

View Kit

Hydroponic Kit Materials:

• 6 bottles
• 6 100% cotton strips (2”x20”)
• 6 coconut coir pellets
• 1 packet of basil seeds
• 1 3-oz bottle of liquid fertilizer
• 1 measuring cup
• 6 pre-cut foil
• 1 pair of gloves, nitrile, medium

Additional items needed:

• Scissors (or knife)
• 1L or 1-gallon bottle for fertilizer dilution (any bottle will work)
• 1/2 tsp measuring spoon (scoop)
• Permanent marker
• Water
• Tape

This project follows the Scientific Method. Review the steps before you begin.

1. Remove the cap of each bottle (6 total).
2. Where the bottle starts to become flat, about 4 centimeters from the top, make a mark with your permanent marker around the bottle's edge, creating a ring around it to indicate where to cut. 
3. Cut along the upper half of the bottle (where you marked) until the bottle is separated into two parts. The bottom half will hold the water or nutrient-rich water, while the top will hold the coconut coir and seeds to grow the plants in, as seen in Figure 1.
   
   
   Image Credit: Laura Ohl, PhD / Science Buddies

   Image of where to cut bottle for hydroponic system, right below the bend on the top of the bottle.

   Figure 1. Image of where to cut the bottle for the hydroponic system. 
   
   
4. Invert the top of the bottle, placing the opening downward into the bottom half of the bottle.
5. Grab a 2” x 20” piece of cotton to create the wick system.
6. Tie the piece of cotton twice in the middle, forming a knot in the cotton strip and two tails on either side to form a wick system.
7. Insert the wick's tails through the bottle's opening until the knot stops at the opening and the tails flow freely below it, as seen in Figure 2.
   
   
   Image Credit: Laura Ohl, PhD / Science Buddies

   Image of how to insert cotton wick into top of bottle, with tail ends down and knot in top compartment.

   Figure 2. Wick system orientation to ensure water goes up to the seeds. 
   
   
8. Place the top of the bottle and wick system into the bottom of the bottle.
9. Prepare your no nutrient, negative control bottles (3 each):
   1. Mark each bottle with a negative symbol (-) to indicate that it is without nutrients.
   2. With your measuring cup, measure 190mL (or 6.5 fl oz.) of water to add to each hydroponic system or bottle, as seen in Figure 3.
      
      
      Image Credit: Laura Ohl, PhD / Science Buddies

      Image illustrating how to pre-wet the wick of the hydroponic system.

      Figure 3. Pre-wetting the wick of the hydroponic system. 
      
      
   3. Pour 190 mL of water per bottle over the top knot, allowing it to wet the entire cotton wick and trickle down to the bottom of the apparatus. This will pre-wet the wick.
10. Create your diluted nutrient solution by measuring 1/2 tsp of concentrated liquid fertilizer containing the nutrient-rich solution and pouring it into 1 L of water. Invert the bottle 3 times to mix the solution or until it's homogenous or looks all the same.
11. Prepare your experimental condition bottles (3 each):
    1. Mark your bottle with a positive symbol (+) to indicate it contains diluted liquid fertilizer or nutrients.
    2. Measure 190mL of nutrient-rich solution for each experimental hydroponic system or bottle.
    3. Pour the 190mL of nutrient-rich solution over the knot of each wick while it's in the bottle, the same way you did for your negative control bottles.
12. Prepare the coconut coir for the seeds to have a substrate to grow in.
    1. Add a pellet of coconut coir to a cup. 
    2. Rehydrate the coconut coir pellet in 50mL of water. This will be enough for one hydroponic system or bottle. 
       1. Note: This can be scaled up to rehydrate multiple coconut coirs at a time. 
    3. Wait about 2-3 minutes for the coconut coir to absorb the water.
    4. Then gently mix it with your measuring spoon, so that it has a similar consistency throughout the material.  
    5. Carefully transfer the coconut coir into the top half of the bottle to the top edge or lip of the bottle, but do not overfill it, as seen in Figure 4.
       
       
       Image Credit: Laura Ohl, PhD / Science Buddies

       Rehydrating the coconut coir with water.

       Figure 4. Rehydrating the coconut coir and transferring it to the hydroponic system.
       
       
        
13. Plant the seeds in the coconut coir.
    1. Before you plant your seeds, use the end of your permanent marker to make small indentations about 1/8 of an inch deep, to the top of the rehydrated coconut coir in each hydroponic container.
    2. Carefully drop one seed into each of the four indentation, and cover with a thin layer of excess coconut coir as seen in Figure 5.
       
       
       Image Credit: Laura Ohl, PhD / Science Buddies

       Seeding seeds into indentations in the hydroponic system.

       Figure 5. Adding seeds to each indent in the hydroponic system.
       
       
14. Cover the bottle with foil to prevent algae from growing inside of the container, tape closed to ensure no light gets in, as seen in Figure 6.
    
    
    Image Credit: Laura Ohl, PhD / Science Buddies

    Covering hydroponic systems with foil covers to prevent mold growth.

    Figure 6. Covering hydroponic system in foil to prevent mold growth.
    
    
15. Observe and record the growth of the plant over the coming weeks using Table 1.
16. Form conclusions about your experiment by answering the following questions:
    1. How do nutrients impact plant growth? Use your results to inform your answer.
    2. Is soil necessary for plants to germinate and grow? Remember that these hydroponic systems do not contain soil, but coconut coir.

Swipe left to see more

Table 1. Data table to keep track of weekly plant and leaf growth. 

Hydroponics plant growth experiment	Nutrient-rich water			No nutrient water
Measurement	N1	N2	N3	N1	N2	N3
Number of leaves
Length of largest leaf (mm)
Width of largest leaf (mm)

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Global Goals

The United Nations Sustainable Development Goals (UNSDGs) are a blueprint to achieve a better and more sustainable future for all.

This project explores topics key to Zero Hunger: End hunger, achieve food security and improved nutrition and promote sustainable agriculture.

This project explores topics key to Sustainable Cities and Communities: Make cities inclusive, safe, resilient and sustainable.

Variations

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