Cabbage Chemistry: DIY pH & Soil Testing

Detailed Soil pH Testing Protocol
We are providing a written summary of our full experimental process so future teams can replicate or extend our work:

Soil pH Testing Protocol (from our project):

• Prepare a natural pH indicator by chopping red cabbage, boiling it for 15 minutes, and collecting the deep blue liquid.

• Gather materials: soil sampler, pH strips, distilled water, sample cups/containers, and a spoon.

• Collect four soil samples from different locations along the Blacks Beach Trail, each surrounded by different plant species.

• Mix each soil sample with 1/2 cup of water and let it sit for 15 minutes to allow minerals to dissolve.

• Test each sample using:

  1. Commercial pH strips

  2. A tablespoon of the soil-water mixture added to the cabbage indicator, and observe the color change to indicate pH level
     
     

Demonstration Video
A short video documenting our full process, from cabbage preparation to field sampling to pH testing. This is a visual guide for anyone attempting the experiment for educational or scientific purposes. (Linked in the Project Deliverables section)

Annotated Bibliography of Key Sources
A list of references we used, including:

• The Journal of Chemical Education article on student-led urban estuary monitoring
  https://pubs.acs.org/doi/full/10.1021/acs.jchemed.7b00334 

• The Cornell SoilNOW Guide explanation of red cabbage as a natural pH indicator
  https://blogs.cornell.edu/soilnow/ph/how-to-test-soil-ph/ 

• Scripps Coastal Reserve Capstone – Environmental Significance & Public Engagement
  https://escholarship.org/uc/item/961043gm 

• Cabbage Indicator Color Reference Chart showing expected indicator color changes https://testbook.com/chemistry/red-cabbage-indicator  

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Equipment & Materials List
Below is the complete list of materials we used, as described in our project document:

Materials Used:

• Soil collection probe

• pH testing strips

• Distilled water

• Red cabbage

• Boiled water

• Soil collection containers

• Soil from the Scripps Reserve/Blacks Beach Trail area

• Spoon

pH Chart:

We have decided that our project will be OPEN for expansion. Since we determined that soil pH is not an affordable way to determine soil health, we encourage others to explore other methods to determine soil health that are both accessible and affordable. 

We found that Using pH strips and Cabbage juice was not a conclusive way to determine soil health, as for all samples and methods, we got the same pH range (6-7). For further directions, we should ask ourselves of other accessible and affordable ways to determine soil health.