What Is a pH Tester for Soil?

Soil Acidity

• Plants need numerous different chemical compounds to grow successfully, but three are most essential: nitrogen (N), potassium (K) and phosphorus (P). The pH level of a soil determines how much and in what form these nutrients will be available to plants. A soil with a pH reading above 5.5, for instance, will feature nitrogen in a form that is available for plants to use (nitrates). Similarly, phosphorus (P) will only be available to plants in form that they can use in soils with a pH reading between 6.0 and 7.0.

The pH Scale

• The pH scale is not only used for soil but actually to measure the acidity of any compound. The scale ranges from 0 to 14, with acidic compounds (lemon juice, battery acid) measuring from 0 to 7 on the scale, neutral compounds (water) measuring 7 and basic or non-acidic compounds (salt water, bleach) measuring from 7 to 14. In the context of soil acidity, the term "basic" is usually replaced with "alkaline" to describe soils that are not highly acidic.

pH Testers

• Since soil acidity or alkalinity must be determined before planting, pH testers are devices sold to aid gardeners in determining this important gardening metric. An electronic pH meter is easy to use and accurate, usually a hand-held device that you simply stick into the ground to take a pH reading. Gardening supply stores also sell a simpler -- albeit less effective -- way to test your soil. Soil samples are placed into containers into which dyes are added; the color of the dye indicates the acidity or alkalinity of the soil.

Other Considerations

• The importance of determining soil pH before you cultivate a given plant cannot be overstated. Soil with a low pH reading can cause health problems for plants grown in that soil, such as manganese toxicity, aluminum toxicity, calcium and magnesium deficiencies and stunted growth. As soil acidity increases, the availability of vital micronutrients decreases. Determine the pH requirements of every plant you plan to grow in your yard and test your soil's pH before planting to avoid problems associated with soil pH.