soil ph

What is Soil PH?

Soil pH is a measure of the acidity or alkalinity of the soil. When you test pH, you are measuring the number of hydrogen atoms that carry a positive charge.


Soils can be classified according to their pH value:

  • 6.5 to 7.5—neutral
  • over 7.5—alkaline
  • less than 6.5—acidic, and soils with pH less than 5.5 are considered strongly acidic.

The higher the concentration of hydrogen ions, the more acidic your sample is. The lower the concentration of hydrogen ions, the more basic your sample is. Acidic substances fall between pH 0 and pH 7 on the pH scale. Basic substances fall between pH 7 and pH 14 on the pH scale. pH 7 is neutral; it is neither acidic nor basic.

Optimal Soil pH Ranges

Plants that thrive in more acidic soil include apple trees (pH 5 – pH 6.5), potatoes (pH 4.5 – pH 6), and orchids (pH 4.5 – pH 5.5). Alkaline loving plants include acacia and walnut trees (they both like soil between pH 6 – pH 8).

To figure out the best soil pH for your needs, do a little bit of research on the type of plants that you want to grow. Natural soil is typically between pH 4 and pH 8. If your soil’s pH doesn’t match the plants’ optimal range, you’ll need to treat your soil.

Common acidic substances include orange juice, soft drinks, and black coffee. Common basic items include gin, baking soda, and household cleaners. Pure water is completely neutral at pH 7.

Why Test Soil pH?

Correct soil pH is essential to ensure optimal plant growth and crop yield, because it allows nutrients to be freely available for plants to take in. Testing the pH of your soil helps to determine what plants are best suited for that area.


Things That Affect Soil pH

Many things can affect the pH of your soil. The most common factors are climate and weather, other plants in the area, the pH of your irrigation watersoil type, the kind of fertiliser you use, and nutrient availability.

  • Climate and Weather
  • Plants
  • Irrigation Water
  • Soil Type
  • Fertiliser
  • Nutrient Availability

How to Test Soil pH

Slurry pH Testing:

How to Test Soil Using the Slurry Method

  1. Gather some soil from the test area.
  2. Take the homogeneous sample and add equal parts of soil and distilled or deionized (DI) water in a 1:1 ratio. So, for 25 grams of soil you would add 25 mL of water.
  3. Stir the sample for 5 seconds.
  4. Let it sit for 15 minutes.
  5. Start stirring the sample again after 15 minutes, and take your measurement.

Direct Soil pH Testing

How to Test Directly in Soil

  1. Using an auger or ruler, first put a hole down into the soil. The hole needs to be the same depth each time you test to avoid pH discrepancies.
  2. Add some distilled or deionized water to the hole; the soil should be damp but not saturated with water.
  3. Insert your testing instrument into the hole, and allow for the reading to develop or stabilise.

Soil pH Testing Options

four main groups for soil PH Testing options:




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