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How to Bring the pH Level Down in Plants

The pH level of the soil around your plants can affect them negatively by preventing roots from being able to absorb necessary nutrients available in the soil. After you have tested your soil and determined the pH needs to be lowered, you'll need to know how to bring the pH level down in plants in a safe manner that isn't harmful to the very plants you want to help. Unlike one-day garden projects, plan to allow time for the pH to shift rather than shocking the plant with a sudden change.

Things You'll Need

  • Shovel
  • Plastic cup
  • pH test kit
  • Gallon watering can
  • Clean water
  • Aluminum sulfate
  • Tablespoon (for garden purposes only)
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Instructions

    • 1

      Dig a hole near your plant 12 inches deep with a clean shovel. Collect a sample from the wall of the hole as deeply as possible into a clean, plastic cup. Test the sample according the method of your pH test kit, either testing in water or inserting a probe, to determine the starting pH of your plants. Refill the hole.

    • 2

      Fill a gallon watering can with 1 gallon of clean water. Add 1 tbsp. of aluminum sulfate to the water. Stir the mixture slowly to mix the sulfate into a dilute solution.

    • 3

      Water around the base of your plant with the sulfate mixture, working in a 1 to 2 foot diameter. Avoid pouring the sulfate water directly against the stems, branches and leaves of the plants as you water.

    • 4

      Leave the soil alone for two to three weeks as the sulfate has a chance to get into the soil and lower the pH. Repeat Step 1 to test the soil to note how far the pH dropped and whether or not it still needs to be lowered. Repeat Steps 2 through 4 as often as needed until you reach the desired pH.