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A soil test can help you make good decisions about what your soil may need.

• Tests show nutrient levels, pH, and organic matter content.
• Soil biology can be analyzed by specialized labs.
• In the city and near roads and old buildings, you may want to test for lead and arsenic.
• Test results also provide recommendations for improving soil fertility.

Nutrient levels. Tests can help you determine whether your soil is deficient in any of the essential plant nutrients.

pH. Most plants thrive between pH values 5 and 8. In the rainy Pacific Northwest, soils tend to be acid (below pH 7) rather than alkaline (above pH 7). A test will point out your soil’s pH.

Organic matter content. Worms, insects and other tiny organisms that fertilize your plants and keep them healthy feed on your soil's organic matter. A level of at least 5 percent is ideal for most garden plants.

Biology. Some labs can analyze your soil for the presence or absence of a wide array of beneficial soil organisms and suggest ways to enhance the populations of those that will help your garden plants thrive. Visit Soild Foodweb for more information.

Lead and arsenic. Urban soils sometimes contain harmful levels of lead and other heavy metals. Get your soil tested, especially if you have young children and:

• Your garden is near a road. There may still be residue from the use of leaded gasoline.
• Your home was built before 1978, when lead in house paint was banned.
• Your property was used an orchard, where lead or other heavy metals may have been used as pesticides.
• You live in the Puget Sound basin, within the Asarco copper smelter plume areas. Arsenic, lead, and other heavy metals are still in the soil as a result of this pollution.

Children are especially vulnerable to health effects of these metals. They can cause permanent learning disabilities and decreased growth.

How to get a soil test.

• Basic tests for major nutrients and pH can be purchased for home use.
• A laboratory analysis is generally more reliable.
• Contact your local cooperative extension service to find a soil fertility-testing lab.
• Contact your local health department for information on testing for lead and other heavy metals.
• The lab will provide instructions on how to collect samples and interpret the results.

Resources:

• Soil sampling (PDF)
• Soil testing (PDF)
• Facts about arsenic and lead