Hydroponics Made Easy

Instructions

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 it.
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 (nutrient-poor or nutrient-rich), 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

   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.

   Why is a wick necessary in this type of hydroponic system?

   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). Mark each bottle with a negative symbol (-) to indicate that it is without nutrients. 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. 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.

   What do the negative control bottles teach us about plant's requirements for growth? Do plants need nutrients to grow?

   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.
   
   
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.

    Why do you think the concentrated liquid fertilizer needs to be diluted?

11. Prepare your experimental condition bottles (3 each). Mark your bottle with a positive symbol (+) to indicate it contains diluted liquid fertilizer or nutrients. Measure 190mL of nutrient-rich solution for each experimental hydroponic system or bottle. 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. Add a pellet of coconut coir to a cup. Rehydrate the coconut coir pellet in 50mL of water. This will be enough for one hydroponic system or bottle. (Note: This can be scaled up to rehydrate multiple coconut coirs at a time.) Wait about 2-3 minutes for the coconut coir to absorb the water. Then, gently mix it with your measuring spoon, so that it has a similar consistency throughout the material. 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.

    In hydroponics, plants grow from nutrient-rich water. Why would we still use a growing medium?

    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. 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. Carefully drop 1 seed into each 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, and tape closed to ensure no light gets in, as seen in Figure 6.

    How does the foil prevent algae growth?

    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.

    How do you think the nutrient-rich vs. nutrient-poor hydroponic systems will impact plant growth? Make a prediction.

16. As the plants grow, measure their growth daily. Use these measurements to form conclusions about your experiment by answering the following questions: How do nutrients impact plant growth? Use your results to inform your answer. Is soil necessary for plants to germinate and grow? Remember that these hydroponic systems do not contain soil, but coconut coir.

    How does your plant growth compare between each replicate of the same condition, and between nutrient-poor and nutrient-rich hydroponic systems?