How to Use a pH Meter

pH Basics: What It Is and How to Measure It

Good nutrition is essential to grow plants successfully. Soil pH is one factor to consider in order to improve plant nutrition and production. Learn more about soil pH and how to use a pH meter below.

What is Soil pH?

  • A measure of the acidity or basicity of your soil.
  • Soil pH is important since it affects the growth of plants and the severity of some diseases.

What does pH affect?

Soil's pH affects the ability of plant roots to absorb nutrients. Calcium, phosphorus, potassium and magnesium are likely to be unavailable to plants in acidic soils, while plants have difficulty absorbing copper, zinc, boron, manganese and iron in basic soils. By managing soil pH, you can create an ideal environment for plants and often discourage plant pests at the same time.

Measuring pH

Soil pH is measured on a scale of 0-14. A soil or water pH reading below 7 is considered acidic, while a pH reading above 7 is basic. A pH reading of 7 is neutral and is ideal for many plants and spray materials. The pH scale is logarithmic, which means that a pH reading of 6 is ten times more acidic than a reading of 7. You can measure the pH of your soil, your spray tank water or your irrigation/fertigation water.

Crops, ornamentals, and turf need careful pH management to maintain their best quality and appearance. The wrong pH can lock nutrients in the soil, making them unavailable to plant roots. A pH that's too high or low can make disease, insect, and weed problems worse.

Spray tank water:
 If your spray tank water is too acidic or too basic, the pesticides you mix in can be deactivated and may even burn your plants.

Irrigation/fertigation water:
 The pH of the water you apply to your plants should match your desired soil pH otherwise the water applied will gradually change soil pH.

pH Levels

Acceptable pH varies by plant type. If you're not sure what's best for your plants, you can check a reference book or ask your seed or chemical dealer, Cooperative Extension agent, or private consultant.

Remember, when you adjust soil pH levels, you can also affect plant growth, nutrition, and susceptibility to pests. When setting a pH goal for your soil, you will want to take all of these considerations into account.

Acidic fertilizers can be used to lower pH, and limestone is often used to raise pH. The type of limestone or fertilizer applied and your soil type can make a difference in how quickly and how much pH will change.

How to Test Soil pH

  1. Sample—Collect 15-20 soil samples per field, fairway or potting mix.
  2. Mix—Place these samples in a clean plastic container.
  3. Measure—Remove a small amount (coffee measure) of soil from your mix and add to an equal amount of distilled water.
  4. Shake and wait—Stir or shake the soil and water mixture vigorously. Then let it sit for five minutes.
  5. Test—Turn on your pH meter and remove the cap to expose the sensor completely in the solution. Record the reading on the meter.

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