Soil pH is probably the single most informative measurement that can be made to determine soil characteristics.
— Thomas, G.W. 1996

Soil pH is an excellent indicator of a soil’s suitability for plant growth. It tells much more about a soil than merely indicating whether it is acidic or basic. For example, availability of essential nutrients and toxicity of other elements can be estimated because of their known relationship with pH Thomas, G.W.  1996 (1). It influences the solubility of nutrients, affects the activity of micro-organisms that break down organic matter and impacts nutrient transformations in the soil. This affects the availability of nutrients in the soil and impacts crops growth either positively or negatively Omex Agriculture Inc. 2016 (2).


Soil pH is a measure of the concentration of hydrogen ions in the soil solution. pH affects both the availability of nutrients and the plants ability to absorb and assimilate them. When the pH is not at the proper level, the plant will lose its ability to absorb some of the essential elements required for healthy growth. Therefore, plant growth, including nutrient availability and microbial activity, are favored by a soil pH range of 5.5 – 8.0.

See the pH range guide for a wide variety of plants, by clicking here: pH range guide


The R-Squared Diagnostic's Soil pH and Texture Test Kit components:

3 - Air tight protective tubes containing 15 pH papers each (short-range pH 4.5 to 8.5)
1 - Soil pH and texture sample reaction vessel (blue cap)
1-  pH and soil texture instruction leaflet
1 - pH scale color chart
1 - Soil textural triangle chart
1 – Ruler

Other optional items not included with kit:

  • Wax or grease pencil for marking S and W line on Sample Reaction Vessel and drawing "separate" lines on Soil Textural Triangle
  • Non-foaming dishwasher detergent
  • Calculator

Soil pH Testing Instructions:

  1. Collect soil or compost samples, with several handfuls, at random locations and mix together well, in a bucket or small container, to form a “composite sample”. Remove debris (large pieces of leaf, wood or rock). Use a garden sieve if available.  
  2. The kit contains a Sample Collection Vessel (with blue cap) and a ruler. Using the ruler, mark the Soil (S) and Water (W) lines on Sample Collection Vessel (Figure 1).
 Figure 1: Mark S and W lines with wax pencil or similar.

Figure 1: Mark S and W lines with wax pencil or similar.

   3. Add soil to S line and clean water (filtered or distilled) to W line indicated by the ruler.
   4. Shake vigorously for 1 minute so that the soil is thoroughly mixed with the water.
   5. Wait for the soil to settle, at least 10 minutes.                                                                                  6. Tear off a 1-inch strip of the pH paper and insert in the water; then, immediately remove from the          liquid. The color will change instantly.                                                                                             7. Hold paper against the color chart shown in the inside lid of the box and match colors for soil pH.