Hypothesis

I think the plants that get 100% (recommended amount) of fertilizer will grow the best. If the plants get too little fertilizer, 25% or 50%, the fertilizer won't be able to boost the growth as much. I think 125% of the recommended amount of fertilizer won't grow the best either, because too much fertilizer can stress the plants and make it hard for them to stay stable with the amount they're being given, and can end up killing the plants. Overall, I think the plants with the recommended amount (100%) of fertilizer will grow the most efficiently.

How does fertilizer actually boost plant growth? The fertilizer I am using has Nitrogen, Phosphate, and Soluble Potash. Nitrogen helps the plant make chlorophyll. Chlorophyll in lettuce is the green pigmentation that plants use to catch sunlight for photosynthesis. Some types of lettuce have a lighter colour because there is less chlorophyll. Photosynthesis is the process of

Independent variable - Amount of fertilizer (25%, 50%,100%, 125%)

Dependent variables - Plant growth

1. Plant height
2. Plant width
3. Plant weight

Controlled Variable - The same for all plants

1. Amount of water
2. Watering schedule
3. Amount of light
4. Light schedule
5. Type of light (Grow lights)
6. Type of soil (Potting mix)
7. Type of plant (Buttercrunch lettuce)
8. Fertilizing schedule (Once a week)
9. The temperature stays the same for all plants
10. Size of pots

For my project, I first germinated about 60 seeds. To do this, I first filled a bowl with water, put my seeds inside, and stirred for 20 minutes. After, I wet 2 paper towels, then wrung them out, until they were barely wet. After, I took the seeds out of the bowl, and put all the seeds on one paper towel. I then placed the second paper towel on top. The next day, I wet the paper towel twice to keep it moist. After 3 days, I filled 12 pots with soil. I picked out 36 of the best seeds and placed 3 seeds per pot. I also made a stand for 4 strips of grow lights. I put 3 plants under each grow light. Every day, I watered each plant until it came above the surface of the soil. I then watered the plants every second day. After 2 weeks of doing this, I started fertilization. I first filled 4 measuring cups with 1 litre of water. I then got miracle grow indoor plant food, and in 1, I did 5 squirts of the fertilizer. This was going to be my 125% mixture. In the next measuring cup, I did 4 squirts for 100%. I did 2 squirts for 50%, and 1 squirt for 25%. I then placed 50 ml of the 25% mixture into 3 plants under the same light. I also labelled the 25% mixture and the 3 plants that I put that mixture into. (Group A 25%). I then repeated this process for the rest of the plants. That same day, before I added the fertilizer, I recorded the weight in grams, the height, and the width in cm. This will be how I determine my conclusion. I am taking pictures of each plant group weekly to show the change.

Qualitative observations

25% fertilizer plants: The plants are growing slowly. Stems are thick and strong. Leaves are smaller but

50% fertilizer plants: This group of plants are growing slightly quicker than the 25% group

100% fertilizer plants: These plants are growing quite quickly. Though the stem is not as strong, the plants are just able to hold themselves up, grow tall, while keeping a good balance.

125% fertilizer plants: All of the plants are very thin. Even with the light being closer to the plant, the stem has not become thicker. These plants have been drooping quite a bit, probably because they can't hold their own weight.

Light observation: Lettuce needs grow lights about 5 - 10 cm away from the tallest point. When the lights are farther away from the plants, they develop a weak stem, and usually are not able to hold up their weight

The plants that grew the most efficiently was 50% of the recommended amount of fertilizer. Just because the fertilizer boosts growth, does not necessarily mean they are the strongest. 125% of the recommended amount was actually one of the worst plant groups. This was due to the fact that too much fertilizer can stress plants too much and make them weaker. Fertilizer boosts growth by stressing the plant to grow more, and the plant cannot handle more than what the company making the fertilizer recommends. I think that 25% did not win because it did not have as much stress to grow faster. I think 100% didn’t win either because there was still too much stress on the plants, causing them not to do as well. I think that 50% grew the most efficiently and fast, because there was not so much stress on the plants. This gave a chance for this plant group to grow strong, while still getting a boost, and growing the fastest.

My experiment tested how different concentrations of fertilizer (25%, 50%, 100%, and 125% of the recommended amount) affected plant growth by measuring the weight, height, and width of each plant. The data showed that the group given 50% of the recommended fertilizer grew the biggest and most efficiently compared to the other fertilizer concentrations. This result shows that plants do not necessarily need the full recommended amount to achieve strong growth. Because the 50% group outperformed the others, my original hypothesis—that the recommended amount was necessary for the best growth—was not supported by the results. These findings suggest that using less fertilizer could be more effective and more cost-efficient for growing plants. If I were to do this experiment again, I would probably change the way I checked how much water is in each plant. I used a moisture meter, thinking that this would also keep the weight of the water consistent in each plant. Turns out, I was wrong, so the weight is actually decreasing because the weight of the water is inconsistent.

People could use many results in quite a few ways. One way is to save money, because if a lower concentration of fertilizer helps plant growth, that means less money spent on fertilizer for people like farmers. Using less fertilizer would also mean less of a chance of consuming something dangerous in the plant.  Too much fertilizer, in some cases, could be toxic for people to consume. My results could also help the environment. Less fertilizer usage means less of a chance of polluting bodies of water like wetlands, rivers, or small streams. My experiment will also determine if adding more than the recommended amount of fertilizer actually helps the plants. If it does, we can speed up plant growth while keeping the plant alive. By finding the best fertilizer usage, people can grow healthy and strong plants while keeping the environment safe.

My findings could also have positive environmental impacts. Reduced fertilizer usage lowers the chances of polluting water bodies like wetlands, rivers, and streams. My experiment will also investigate whether applying more than the recommended amount of fertilizer actually enhances plant growth. If it proves effective, we could accelerate plant growth while keeping the plant healthy.

By determining the optimal fertilizer usage, people can grow healthy and fast-growing plants while also protecting the environment.

A problem that occurred is the moisture meter only detected how moist the soil was, not how much water was actually in the soil. This left the weight of each plant decreasing and increasing with no cause. Next time, I will measure out the water, so the water stays the same for all the plants, creating a more exact weight, making the experiment better.

https://freescience.info/the-role-of-nitrogen-in-plant-growth-a-scientific-perspective/? https://www.researchgate.net/publication/364150308_Role_of_nitrogen_N_in_plant_growth_photosynthesis_pigments_and_N_use_efficiency_A_review https://research.fs.usda.gov/treesearch/26654 https://scholar.google.ca/ https://www.mdpi.com/2311-7524/11/9/1077 https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2024.1430241/full?utm https://harvardforest.fas.harvard.edu/education-opportunities/classic-outreach-resources/autumn-foliage-color/leaf-science/leaf-pigments/?utm

I would like to first thank Ms.Kouseris and Ms.Underdahl for giving me support in this project, as well as organize this project at our school. I would also like to thank the Calgary Youth Science Fair for letting this science fair happen.