GOLD

Hydroponic Lettuce Growing

We have two sets of hydroponic systems growing leaf lettuce. We are growing one set with natural light and one set with artificial light to determine what is best for the plants in the winter.
Kyle Wicentovich Mark Wicentovich
Grade 5

Hypothesis

Our hypothesis is that lettuce grown with sunlight as its light source will work better than using artificial light because the sun is more powerful and has more energy than a lightbulb.

Research

We conducted research using the book 

“Hydroponic Food Production”

The  questions we wanted to answer in our research were:

What do the plants need to grow best besides the basics (Oxygen, water, light)

What is pH?

When can we transplant?

We also looked for clues on what light would be best in Canada but we found it was based on so many factors. Like direction of window, time of year, type of artificial light, etc.

We found good information from “Advanced Nutrients” who make nutrients specifically for hydroponic growing.  We followed these directions for our plant nutrient concentrations.

Please see our attached presentation for more information on our research.

Variables

The variables we studied were sunlight and artificial light (Gro-Lights). We kept all other variables the same for the plants so we could make conclusions about sunlight versus artificial light. 

We had:

7 sunny days

4 fully cloudy days

5 partly cloudy days

4 unrecorded days because we were not home.

The weather and the amount of sunlight was an uncontrolled variable.

 

Lights were on 8 hours per day. This was a controlled variable.

We had 4 batches of lettuce with 7 plants in each batch.

Batch 1 and Batch 2 were placed in sunlight

Batch 3 and 4 were placed under artificial lights.

Plants 7 in Batch 3 and 4 would not fit under the lights so these plants are a good experimental “control”.  We explain in the observations section that these plants did not grow as well as any of the others.  So they proved that our basement location did not get as much light as our sunny location.

 

Procedure

 

  • We planted the seeds on Dec 28th 2020
  • We placed them under the artificial lights to help them sprout
    • We placed ALL seeds under lights, even the ones that later would be placed in sunlight
  • We watered them regularly with nutrient solution
  • We had a timer on the artificial lights set to 8 hours of light per day
  • On Jan 2, 2021 (6 days after planting) we already had some seeds sprouting
  • Some seeds did not sprout at all
  • once the plants had two cm long roots we transplanted them into our hydroponics system. This occurred on Jan 30th. Please see our attached presentation in the "Attachments" section for a video of the transplanting process.

    We planted 28 lettuce plants on January 30th

    14 for sunshine and 14 for artificial light

  • For the sunny location we used a south facing window. We placed the artifilcial lights over the plants in the basement 
  • On Jan 31st we recorded the length on the longest leaves for the 28 plants
  • We let the plants grow for several weeks. We checked the water level in the water bucket under the hydroponic system and we added water, nutrient solution and pH Down when needed.

Observations

Observations (Feb 21) Artificial Light

  • The plants in Batch 3 and 4 had 8-9 leaves each.
  • The leaves of the plants that were growing under artificial light were larger than the plants growing in sunlight (see chart slide in our presentation in the Attachments section).
  • The roots were also larger on the plants growing under artificial light.
  • During the growth phase these plants used more water.
  • The leaves were bright green.
  • The stalks of the plants were thicker.
  • Plant 7 (in batch 3&4) did not receive any artificial light and the plants hardly grew.  The leaves were a pale, light green.

    Observations (Feb 21) Sunlight

  • The plants in Batch 1 and 2 had 8-9 leaves each.
  • The leaves in sunlight were smaller than artificial light (see chart slide).
  • The roots were thinner and shorter than the plants growing under artificial light.
  • During the growth phase these plants less water.
  • Leaves were bright green.
  • The stalks of the plants were thinner.
  • All plants fit in the window so they all grew similarly.

Analysis

Why did artificial light work better than sunlight?

  • The artificial light was closer to the plants so they would get more light.
  • In the winter, Canada is farther from the sun so the sunlight is not that strong.
  • We had cloudy days while the artificial lights came on everyday

Interesting Fact

The sun produces 3.86 x 1026 Watts of energy (source: Siri)

38,600,000,000,000,000,000,000,000,000 W

Our artificial lights produced 20W per bulb

The sun is very weak in our living room in the winter!

 

Conclusion

What we learned is that artificial light works better than sunlight. Our hypothesis was incorrect.

Sunlight still worked well, even in winter.  It would be interesting to do this project in the summer.  Would our results be different? Maybe…

 

We hope you enjoyed our project and our presentation.  Thanks for watching.  

 

Application

Our results are useful for any home gardener in Canada. Our results show that artificial light works better than sunlight in the winter, because the plants under the artificial light absorbed more water and grew faster than the sunlight plants. To apply our data, a home gardener may want to buy some artificial lights but they don't have to.  Because in the sunlight, the plants still grew fine.

Savings by growing lettuce at home

My mom bought the hydroponic systems from Wayfair.ca for 75$ each, The nutrient solutions and the seeds cost about 50$ for a total cost of $200.  Our family eats a head of lettuce every five days.  If the cost of the lettuce is $3, we spend 219$ per year on lettuce.  In year 1, the system will save us $19 but after that, it will save us $219 per year minus seed and nutirent costs.  If everyone did the same thing, there would be less trucks on the road delivering lettuce and this would help the environment.

Sources Of Error

Errors due to Variables

If we had three weeks of one hundred percent sunny days our results might have been different. We had a good mix of weather typical for a Calgary winter. Even though the weather was a uncontrolled variable we believe that our conclusions are correct. 

Length of Time to Grow Plants

It took 3 weeks to grow our plants, we could not do the experiment three times.   The short days of January and February that affected our plants could not be repeated at any other time of the year.

Sprouting Seeds 

We probably had the lights too far away from the seeds.  This resulted in spindly stalks. Next time we will put the lights closer to the seeds.  The good thing is that this affected all the plants equally.

 

Citations

Hydropic Food Production by Howard M. Resh

Advancednutrients.com

Acknowledgement

We want to thank our Mom for helping us a lot with the science project and we want to thank Wayfair for selling the lettuce growing system at a good price.  We would also like to thank Mrs. Cooksley for being the CYSF organizer at our school and the staff at the school who judged us.