Commercial and recreational gardeners are showing a growing interest in taking accurate pH measurement of soil samples. The pH of soil indicates more than its alkalinity or acidity strength; it affects the relative availability of nutrients, the soil life, and the type of plants that will thrive.
The common range of soil pH varies from 4.0 to 8.0; the range of soil pH for optimal availability of plant nutrients is 6.0 to 7.0. The ability of soil to provide adequate nutrition to the plant depends upon the following factors:
Soil life refers to living organisms that live in the soil and break down the organic materials. Soil bacteria that assist in the decomposition of organic material thrive at a pH of 6.3 to 6.8. Fungi and mold prefer a more acidic soil, making soil more prone to souring and putrefaction.
Plants also have different soil pH preferences—several gardeners’ web sites offer charts of preferred pH levels for different plants. Knowing the pH of soil can help you choose the correct plants and the required treatment for your soil.
Method A
LAB: To get started you will need a standard pH meter, a pH electrode, an ATC probe, a stirrer with stir bar, beaker, deionized water, and buffers.
Method B
If the testing is being performed for recreational gardening, you can use a pH tester with ATC (35634-15) and buffers for calibration (35653-04).
Scoop up soil into a clean, dry plastic jar or plastic bag. Remove stones and crush any clumps of soil for better results. Gather two to three representative samples of each soil sample to confirm results. No sample preparation or preservative required.
A minor (< ±0.5 pH) difference between results of the same soil sample indicates good technique and high confidence in results.
One of the easiest ways to correct the pH of your soil (both acidic and alkaline) is by adding compost. The alternative is to add an alkaline source (such as ground limestone) to acidic soil or an acidic source (such as pine needles or peat moss) to alkaline soil. Consult with authorities from a local agricultural extension office, local growers’ associations, or university before you apply chemicals to correct soil pH.