Why test soil pH?
Because plants like tomatoes grow best in slightly acidic soil, and you can fix your soil if it’s too acidic or too alkaline — but you have to know first!

Red Cabbage Soil pH Experiment

What You Need:

• Red cabbage

• Water

• Pot and stove (or a microwave)

• Strainer

• 2 clear cups or containers

• Soil sample from your garden

Steps:

• Chop red cabbage into small pieces.

• Put the cabbage pieces in a pot and cover them with water. Boil for 10 minutes until the water turns purple.

• Turn off the stove and let the water cool.

• Strain out the cabbage pieces and keep the purple liquid — this is a natural pH indicator!

• Take a small sample of your soil and put it in one of the cups.

• Add some cabbage water to the soil and watch the color change:

  • Pink/red means acidic soil

  • Green/blue means alkaline soil

  • Purple means neutral soil

Part 4: Adjusting Soil pH (if needed)

• If your soil test shows it’s too acidic (pink/red), you can add lime to make it less acidic.

• If it’s too alkaline (green/blue), add things like sulfur or even coffee grounds to make it more acidic.