There are two main types of soil tests. One test measures the pH level of the soil and can be done with a simple pH soil tester, and the other test measures the pH as well as the minerals and nutrients that are in the soil and must be done in a professional lab.

Soil pH testers consist of a probe and gauge and are available at your local garden center or online. Or you can take your soil samples to the Clackamas County Master Gardeners who conduct free soil pH testing several times a year and use more sophisticated equipment which gives more accurate results. Go to the Clackamas County Master Gardener Website or call (503) 655-8631 for the dates of these free pH testing events. Also check out Testing Soil pH (PDF) for more information on pH testing and how to take your soil samples.

For a very thorough test of your soil which would include measuring the minerals and nutrients in your soil, contact:

A & L Western Agricultural Laboratories
10220 SW Nimbus Ave., Bldg. K-9
Portland, OR 97223
Phone (503) 968-9225
Fax (503) 598-770

Click here to learn how to collect a proper soil sample for testing and here for soil testing fees and the minerals tested.

The correct soil pH is as important to the health of a plant as its location, sun exposure, and soil preparation. Soil pH is a measurement of how acidic or alkaline your soil is. Annual rainfall and the amount of minerals in the soil are two factors that affect the soil’s pH level. Because the high volume of rain that western Oregon gets tends to leach out minerals in the soil, Portland area soils are generally more acidic.

Soil pH is measured on a scale of 0 to 14, with lower numbers being more acidic, higher numbers more alkaline, and 7.0 is neutral. Generally, most plants grow best in a neutral 7.0 pH, although blueberries, azaleas and rhododendrons prefer a soil pH between 4.5 and 5.5, lawns like a pH of 5.5 to 6, and roses do best with a pH of 6.5 to 7. If your soil’s pH level is too high or too low, minerals get bound to particles in the soil so your plant can’t access them, and even adding extra fertilizer won’t help.

Get more information from OSU’s Extension Service on testing and adjusting your soil’s pH level.