watering can pouring out water onto veggie garden below

Experiment: pH in Soil & Food

Looking to add a little "pHizz" to your gardening game? Then you're in the right place! In this blog, we'll dive into the mysterious world of pH and learn how to make sure your plants are living their best life. From the wacky world of Miracle Berries to the ins and outs of soil acidity, get ready to become a true pH master!

Download Printable Worksheets (7th Grade & Above): Teacher MaterialStudent Material

Download Printable Worksheets (6th Grade & Below): Teacher MaterialStudent Material

What is pH?

pH measures the acidity or alkalinity and in this case, in soil.

Why do we need to measure pH in soil?

The pH in the soil controls the nutrient chemical form as well as controls their reactions.

  • ultra acidic (<3.5)
  • extremely acidic (3.5–4.4)
  • very strongly acid (4.5–5.0)
  • strongly acidic (5.1–5.5)
  • moderately acidic (5.6–6.0)
  • slightly acidic (6.1–6.5)
  • neutral (6.6–7.3)
  • slightly alkaline (7.4–7.8)
  • moderately alkaline (7.9–8.4)
  • strongly alkaline (8.5–9.0)
  • very strongly alkaline (>9.0)

What controls pH in soil?

  • Soil acidification: the acidity of the soil decreases over time
  • The rate at which the acidity decreases depends on:
    • Rainfall: the more rain, the more acidic the soil becomes due to an atmospheric reaction with CO2 that creates carbonic acid. The pH of normal rain is around 5.6.
      • With rain comes leaching.
    • Leaching: when water-soluble substances are deposited into lower soil by precipitation
      • With heavy rain comes water pollution. The water-soluble substances are carried elsewhere instead of leaching
    • Root crops: a root crop is a root vegetable like potatoes, beets, or carrots
      • When these crops grow roots, they output hydrogen ions to create a more acidic soil
    • Fertilizer: similar to root crops, the use of ammonium fertilizers also outputs hydrogen ions to create a more acidic soil.
      • The fertilizer undergoes a nitrification process to form nitrate which leads to the discharge of hydrogen into the soil.
    • Nitrification Process: ammonium is converted into nitrite through oxidation and nitrite is oxidized into nitrate
    • Acid Rain: this occurs when sulfur and nitrogen are oxidized from burning fossil fuels or volcanoes
      • Does not always have to be raining. This could be in snow, fog, hail, or dust with acid in it.
      • The pH of acid rain is around 4.6. While a lesser number than rain, normal rain is considered neutral and acid rain is not. When acid rain gets into waterways, it contaminates and creates a more acidic environment.
    • Oxidative weathering: when oxygen combines with other substances to create an oxide

What pH do foods need?

pH needed for different types of fruits and veggies in soil from Miracle Fruit to squash to raspberries

How to test pH in soil:

  • The soil of the Miracle Fruit Plant should always be between 4.5 and 5.8. Failure to do so may result in a wilted, brown, sad plant.
  • Water with filtered water or rain water only.


Record the pH levels for your plant as well as experiment with different items to see if it increases or decreases the pH level in soil.

Partner up and take turns recording observations, characteristics, and fixing any issues that arise with the miracle berry tree. 

Finish the hypothesis:

If I add orange peels to my soil, then my plants pH will:
If I add coffee grounds to my soil, then my plants pH will:
If I add more water to the soil, then my plants pH will:
If I add moss to my soil, then my plants pH will:

  • Plant pot, 6 inches wide
  • Soil, if not purchased with the plant
  • Miracle Fruit Plant
  • pH Soil Meter
  • Coffee Grounds
  • Sphagnum Moss
  • Orange peels
  1. Fill 3/4 of your chosen pot with soil mixture.
  2. Carefully remove the plant from its original pot.
  3. Be gentle with the root system and avoid untangling it as this can cause issues in the future.
  4. Place the plant in the pot.
  5. Cover the plant with soil until the roots are not visible.
  6. Make sure not to place the roots too close to the bottom of the pot as this can lead to under watering the plant.
When to check pH level:
  • When you see brown and/or crispy leaves
  • We recommend purchasing a soil pH tester from your local hardware store to get accurate reading
How to raise or lower pH:
  • How to raise pH level:

    • Do not use anything with lime or a lime base

    • Spread your post morning coffee grounds for the tree! Sprinkle grounds on the top of the soil and as they breakdown, it will make your soil more acidic

  • How to lower pH level:

    • Add sphagnum peat moss to the top of the soil, around an inch, and work into the top layers of the soil

    • Be careful not to disturb the roots

Example observation table:





Did I/We Do Anything?

Week 1

Plant looks healthy, 3 leaves

pH reading of 5.5


Week 2

Plant seems to be yellowing, could be from overwatering

pH reading of 4.0

Sprinkled coffee grounds on the top to help increase pH

Week 3

Plant has sprouted a new leaf making 4 total

pH reading of 5.0


Week 4

The leaves are turning red

pH reading of 5.3

Moved the plant to a place where there was filtered light. Will continue to watch

Weeks 5-6

No new red leaves

pH of 5.0

Added a little of coffee grounds again to raise pH

Weeks 7-8

The leaves now look pale, not as vibrant as before

pH of 6.0

Added sphagnum moss to the soil in hopes it comes down


CCSS.ELA-LITERACY.RST.6-8.3 Follow precisely a multistep procedure when carrying out experiments, taking measurements, or performing technical tasks.
CCSS.ELA-LITERACY.RST.6-8.4 Determine the meaning of symbols, key terms, and other domain-specific words and phrases as they are used in a specific scientific or technical context.
CCSS.ELA-LITERACY.RST.6-8.7 Integrate quantitative or technical information expressed in words in a text with a version of that information expressed visually (e.g., in a flowchart, diagram, model, graph, or table).
CCSS.ELA-LITERACY.RST.6-8.9 Compare and contrast the information gained from experiments, simulations, video, or multimedia sources with that gained from reading a text on the same topic.

Back to blog