The Effect of Sourdough Starter on Cherry Belle Radish Growth

Category: Plant Science
Student: Audrey Peel
Table: PLANT1800
Experimentation location: Home
Regulated Research (Form 1c): No
Project continuation (Form 7): No

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N/a, project not completed yet.



Fhoula, Imene, et al. “Diversity and Antimicrobial Properties of Lactic Acid Bacteria Isolated from Rhizosphere of Olive Trees and Desert Truffles of Tunisia.” BioMed Research International, Hindawi Publishing Corporation, 2013,

“Global Sourdough Market Size, Trends: Industry Analysis Report, 2025.” Global Sourdough Market Size, Trends | Industry Analysis Report, 2025, Aug. 2019,

Higa, T., and S. Kinjo. Effect of Lactic Acid Fermentation Bacteria on Plant Growth and Soil Humus Formation. University of the Ryukyus, Okinawa, Japan, 2004,

Huang, Nan, et al. “The Influence of Different Concentrations of Bio-Organic Fertilizer on Cucumber Fusarium Wilt and Soil Microflora Alterations.” PloS One, Public Library of Science, 6 Feb. 2017,

Mendes, Rodrigo, et al. “Rhizosphere Microbiome: Significance of Plant Beneficial, Plant Pathogenic, and Human Pathogenic Microorganisms.” OUP Academic, Oxford University Press, 1 Sept. 2013,

Reid, G. “The Scientific Basis for Probiotic Strains of Lactobacillus.” Applied and Environmental Microbiology, American Society for Microbiology, Sept. 1999, 


Additional Project Information

Project website: -- No project website --
Additional Resources: -- No resources provided --

Research Plan:

Procedures: Detail all procedures and experimental design including methods for data collection, and when applicable, the source of data used. Describe only your project. Do not include work done by mentor or others. 

  1. Feed the 100% hydration, white-flour sourdough starter
    1. Measure out 20 grams of sourdough starter
    2. Add 100 grams white all-purpose unbleached flour (King Arthur), 100 grams water at 27C. 
    3. Mix until thoroughly combined
    4. Allow to rise for 8-12 hours. Until the starter has reached its peak (about double in size)
  2. Separate 50 Cherry Belle radish seeds into 5 groups of 10 radishes. 
  3. Divide soil (Planting Tree Organic Planting Mix) into 50 small pots (about 3.5 inches in depth and width). 
  4. Place one seed in each pot about a ½ inch deep. Cover with soil. 
  5. Mix ripe sourdough starter with room-temperature water at 1%, 5%, 15%, and 30% concentrations.
  6. Water 10 radish plants with 35 grams of 1% solution, another 10 with 35 g 5% solution, 10 with 35 g 15% solution, 10 with 35 g 30% solution, and the last ten will receive 35 grams of water, alone. 
  7. Place radishes indoors along a long windowsill. All radishes should be on the same window. 
  8. After two days check the growth of the radish plants. Measure height of the above-ground portion of the radish in cm. 
    1. Repeat every two days.
  9. Take note of the rate of germination for each group, marked by the first sign of the plant above ground.
  10. Three days after planting (1 day after measuring plants), follow steps 1, 5, and 6. Make sure to avoid getting water on the leaves, sourdough starter could dry and prevent photosynthesis. 
    1. Repeat every three days, or when the soil is dry. 
  11. Take note of qualitative measurements such as leaf color and wilting
  12. Once a week measure the pH of all the sourdough centration groups, three randomly selected pots from each. Use soil ph Test Strips. 
  13. At the end of the experiment, pull radishes from the soil and measure root length in cm. 
  14. Additionally, take note of qualitative measurements like the size and color of the radish produced. 
  15. Take the mass (in grams) of each radish when pulled from the soil, making sure that all of the soil has been brushed off. 


Risk and Safety:

There are no major risks involved in this experiment. 


Data Analysis:

The data will be analyzed using Analysis of Variance (ANOVA). This test will determine if there’s a significant difference between the data obtained from each group. It’s important to know if the group given plain water has a statistically significant difference in growth from the group given 10% sourdough solution. This test will allow me to make conclusions about my experiment.

Questions and Answers

1. What was the major objective of your project and what was your plan to achieve it? 

       a. Was that goal the result of any specific situation, experience, or problem you encountered?  

       b. Were you trying to solve a problem, answer a question, or test a hypothesis?

The objective of this project was to determine if sourdough starter could be used as a Bio-Organic Fertilizer. This objective was the result of months of throwing away sourdough discard, and feeling as though there must be a much more recycled use for my sourdough discard. In this experiment, I was mostly testing a hypothesis. I hypothesized that the beneficial microbes in the sourdough starter microbiome would help plants grow by colonizing the area around their roots and preventing the growth of harmful bacteria. After coming up with this hypothesis I designed this experiment to test it.

2. What were the major tasks you had to perform in order to complete your project?

       a. For teams, describe what each member worked on.

The major tasks that needed to be performed in order to complete this project were maintaining the sourdough starter, creating sourdough starter solutions, and measuring plant growth. The first thing that I did was plant all of the radish seeds, and began watering them with my solutions of sourdough starter (0%, 1%, 5%, 15%, 30%). After that, I measured their stem height every other day.

3. What is new or novel about your project?

       a. Is there some aspect of your project's objective, or how you achieved it that you haven't done before?

       b. Is your project's objective, or the way you implemented it, different from anything you have seen?

       c. If you believe your work to be unique in some way, what research have you done to confirm that it is?

My project is novel because this procedure has hardly been done before. After extensive research, very few studies have looked at the impact of sourdough starter on plant growth, and those that did mainly focused on isolating the lactobacillus bacteria for this purpose. My project explores a whole new topic in science, thus it is quite unique in that way. This project was also new for me. I haven’t conducted many full-fledged experiments before, thus this was a new experience in my scientific career.

4. What was the most challenging part of completing your project?

      a. What problems did you encounter, and how did you overcome them?

      b. What did you learn from overcoming these problems?

The most challenging part of completing my project was likely trying to minimize outside variables that could impact the results of the experiment. At first, I wanted to conduct this experiment outside where the plants could receive full sunlight. However, two issues arose. Those issues were that it was becoming too cold for the plants to survive overnight and that there was a lack of variable control such as insect damage. To overcome this issue, I placed all of the plants on a windowsill that received full sunlight throughout the day. However, this solution came with its own set of problems. I was concerned that the plants were not receiving enough direct sunlight due to being indoors. Thus, I learned about the importance of timing experiments to match up with the necessary variables. Had I performed the experiment throughout September rather than October and November, I would have been able to keep the plants outside, which I think would have been very beneficial to their overall health, despite some uncontrolled variables.

5. If you were going to do this project again, are there any things you would you do differently the next time?

If I were going to do this project again, I would certainly change a few aspects of my procedure. Firstly, I would dilute the sourdough starter much more than I did. I would create serial dilutions of the sourdough starter, containing much less starter in the solutions that I watered the radish plants with. Additionally, I would place them in an even sunnier environment, because although I did the best that I could indoors due to the cold, I think that the radishes would grow the most if they were outside in full sun. Finally, I would alternate watering them with regular water and with the sourdough solution because I believe that constant watering with the sourdough solution was too much for maintaining plant health. 

6. Did working on this project give you any ideas for other projects? 

Working on this project gave me many ideas for other projects. Firstly, I believe that studying pathogen resistance in plants watered with sourdough solutions compared to control plants would be very interesting. Seeing as lactobacillus colonizes the rhizosphere of plants to prevent the growth of harmful bacteria, it seems like testing pathogen resistance would be a more applicable way to test the effects of sourdough starter. Another project idea that I have is to determine how sourdough starter works as a pesticide against harmful insects. I found in my experiment, that gnats in the room never went near the plants watered with sourdough starter, but would land on normal plants. I think that this would be very interesting to study further. Additionally, I want to sequence the microbiome of a starter as it progresses from young to mature. In order to truly understand how sourdough starter impacts plant growth, one has to understand the complex workings of the sourdough microbiome. To do so, experiments that sequence the microbes present throughout a starter’s life are very important. This experiment would provide some insight about the interactions between microbes over time.

7. How did COVID-19 affect the completion of your project?

Initially, I had planned on sequencing the microbiome of my own sourdough starter to learn more about the contents of sourdough and community interactions within it. However, with COVID-19, I was unable to utilize the school’s labs as needed in this procedure. Thus, I looked into the impacts that sourdough starter has rather than sequencing it. The project I developed was designed with the intention of being conducted completely at home, so that I could minimize COVID-19 roadblocks when conducting the experiment. However, with the slow re-opening of many facilities, I hope to begin sequencing sourdough starter microbiomes using lab equipment at my school.