Plants have different requirements for light, water, soil type and soil acidity level. If you're putting in a new garden, planting a vegetable crop or trying to troubleshoot a declining plant, don't overlook the effect of soil pH on plant growth. Using a pH tester is not challenging and provides a road map to improve garden health.
The pH scale ranges from 0 to 14, with 7 being neutral. Numbers below 7 designate an acidic soil; numbers above 7 mean an alkaline soil. Each plant has a preferred pH level that keeps it happiest. For example, sweet peppers do best with a pH of 6 to 8, tomatoes prefer a slightly acidic 5 to 7 pH and carrots like a 5 to 6 pH level. If you try to grow carrots and tomatoes in an alkaline soil, they will fare poorly.
Gardeners looking for a home pH tester can choose an electronic tester or a manual color change test kit. Gardeners can also contact their county extension office to arrange for an officer to run a complete soil test. The extensive test advises gardeners on what nutrients to add to soil, what toxins are in the soil and what the pH is. County extension and manual soil tests are inexpensive; the University of Rhode Island offers $4 pH tests (as of 2010).
To get accurate results you need to get a good soil sample. The University of Rhode Island advises gardeners to get 10 samples for garden bed or lawn planting, and three to four samples for tree planting. Using a trowel, slice down through the turf and bring up a small piece of soil. The University of Rhode Island suggests a depth of 3 to 4 inches for lawn samples, 6 to 8 inches for garden beds and 10 to 12 inches for tree planting, since the root systems of each type vary in length. Place all soil slices in a plastic bag and mix them thoroughly to prepare for pH testing.
You need to get the soil sample before you begin. If you're using a manual pH tester, squirt the test solution into the soil sample and wait the recommended amount of time (about an hour, suggests The Garden Helper). Then press a color change strip to the soil sample and wait for the strip to change color. Then consult the scale and match the color with a number on the pH chart to determine soil pH.
For an electronic pH tester, slide the tester's probe into the soil. Within a few minutes, the tester reads the soil pH and gives you a value automatically.
The University of Maine Cooperative Extension advises testing your garden soil once every three years. Soil pH changes over time, and if you've had to amend the soil you will need to add more nutrients to maintain that pH. Test your soil either in the fall before frosts or in the early spring. You need time to amend the soil before planting.