The measurement term for the level of acidity or alkalinity in garden soil is pH. The pH score is important for plant growth and health because it indicates whether certain nutrients in the ground are soluble and available. Nutrients are soluble based on varying pH levels. For example, aluminum and iron are more soluble at a pH level of 4.0 to 5.0.
The pH scale runs from 0 to 14 with the halfway score of 7 considered neutral. The greatest number of nutrients are available near a very slightly acidic or neutral pH of 6.0 to 7.0. Better gardening outcomes depend on gardeners measuring the pH level of their soil.
White Vinegar and Baking Soda Test
One method for testing the pH level of soil at home involves white vinegar and baking soda. To conduct this test, collect 1 tablespoon of dry garden soil. Place a few drops of white vinegar on the collected soil.
If the soil begins fizzing, the pH level is above 7.5 and is alkaline. The fizzing occurs because the soil’s free carbonates react with the acid in the vinegar.
Next, gather 1 tablespoon of wet soil and add a pinch of baking soda. If the soil starts fizzing, it has a pH of less than 5.0 and is acidic.
Another method for measuring the pH in soil uses liquid dye. Dye changes colors when exposed to acids or bases.
Things You'll Need
- 2 cups chopped red cabbage
- 1 cup water
- Medium-sized cooking pot with lid
- 3 small white dishes
- 1/8 teaspoon baking soda
- Tablespoon (measuring spoon for cabbage water)
- Eye dropper
1/2 teaspoon dry soil sample
Step 1: Boil Cabbage
Place 2 cups of chopped red cabbage and 1 cup of water in the medium-sized cooking pot. Cover the pot with the lid and boil until the water is a dark purple color.
Step 2: Strain Water
Pour the water and cabbage through a strainer. Save the water and set aside to cool.
Step 3: Add Baking Soda
Place 2 tablespoons of cabbage water on a white dish. Add 1/8 teaspoon of baking soda. Notice if the water changes color.
Step 4: Add Vinegar
Place 2 tablespoons of cabbage water on another white dish. With the eyedropper add vinegar to the cabbage water. Add one drop at a time until the water changes color. Take note of any color changes.
Step 5: Test Soil
Place 1/2 teaspoon dry soil on a white dish. Add fresh cabbage water to the soil one drop at a time using the eyedropper. Do not over saturate the soil. Move the dish from side to side so the water reaches all parts of the soil.
Step 6: Tip Dish
Tip the white dish with soil so the water drains off. Notice the color of the water.
Red water indicates the soil is acidic, and blue or green water signifies the soil is too alkaline. If the soil is neutral pH, the water stays purple or bluish-purple.
Each time a pH score moves one unit lower on the scale, acidity increases 10 times. Each time a pH score moves one unit higher on the scale, alkalinity increases 10 times. For example, a pH score of 4 is 10 times more acidic than a pH of 5.
Watch Your Weeds
Certain types of weeds favor soil that is more acidic or alkaline. The presence of the weed is an indicator of the pH level of the soil. Dandelions (Taraxacum officinale F.H. Wigg.), woodsorrel (Oxalis L.), dock (Rumex L.) and Queen-Anne’s-lace (Daucus carota L.) thrive in acidic soil.
Mustard (Brassica L.) and thistle (Carduus L.) like soil with a high alkaline pH level.