The pH reading of soil is a measure of the acidity or alkalinity of your soil. The pH scale goes from 0 (very acid) to 14 (very alkaline), with 7 being neutral. Problems in growing most lawns, trees and shrubs will occur only when pH readings are in the extremes--below 5 or above 8. A moderate pH level provides the best environment for the soil-dwelling microorganisms that release nutrients, especially nitrogen, to the roots of the plants.
If soil pH is too low or too high, nutrients needed by plants to make food will not dissolve quickly and may turn into insoluble forms that the plant cannot use.
Most soils in home landscapes are going to range from 6.0 to 7.5. Extreme pH levels are fairly unusual, but still can be found.
For best plant growth you should try to keep the landscape's pH between 6 and 7.5; somewhere between a slightly acidic level to slightly alkaline level. Many soils naturally fall within this range, but some need to be corrected.
While we have a file dealing with the specifics of correcting serious pH problems, remember that the addition of that ubiquitous organic matter will help you avoid any pH problems in the long term.
Taking a pH Reading Yourself
It is possible to check just the pH of your soil, without having to take an entire soil test. For this purpose, use the commercially available plastic strips with pH-sensitive dyes or a meter that measures the soil's pH from electrodes inserted into the soil. The strips are almost as accurate as the meters and they are a whole lot less expensive. Their only disadvantage is that they require distilled water to function.
To use the strip, make a slurry of your soil and some distilled water in a clean dish. The mixture should have the consistency of molasses, and slide slowly off a spoon or spatula. Let it stand for an hour or so. If it has thickened too much, add a little more water to get to the right consistency again. Place the pH strip directly into the slurry and leave it there for at least a full minute (6 minutes is best for accuracy). Remove the strip and rinse it with distilled water. You can then match its color to a chart that comes with the pH kit. Each color represents a different pH level.
Or you can use one of the pH meters that are sold in garden centers and online. They are not considered to be precisely accurate but in my experience they give me a good general idea enough to make decisions about my soil's pH.