What is a soil test?
A soil test is a process by which elements (phosphorus, potassium, calcium, magnesium, sodium, sulfur, manganese, copper and zinc) are chemically removed from the soil and measured for their "plant available" content within the sample. The quantity of available nutrients in the sample determines the amount of fertilizer that is recommended. A soil test also measures soil pH, humic matter and exchangeable acidity. These analyses indicate whether lime is needed and, if so, how much to apply.
Each sample is analyzed for water pH, Mehlich buffer lime requirement, and for phosphorus, potassium, magnesium, and calcium by the Mehlich 3 (ICP) test. The final report includes the chemical analysis of the soil along with lime and fertilizer recommendations for the crop specified.
Where can I get a test kit?
Standard soil test kits may be purchased from county offices of Penn State Extension or from commercial firms or garden centers that stock kits for the convenience of their customers. Alternatively, you can print soil submission forms (pdf format) from Penn State Agricultural Analytical Services Lab (AASL) and submit your soil sample(s), with payment, to the laboratory in your own sample container. Multiple sample information forms and kits are also available for individuals submitting three or more samples.
The test kit consists of a sample submission form, instructions on how to take a soil sample, a sample bag and return envelope for mailing your sample back to the laboratory.
What is the procedure for taking soil samples?
Collect a slice or core of soil (4 inches deep for lawns, 6 to 8 inches deep for gardens) from 8 to 10 random locations across the lawn or garden. Mix these cores together in a plastic bucket. Fill the provide plastic bag with this mixture and label it so you know which area it came from.
How often should a soil be tested?
As a rule, test sandy-textured soils every 2 to 3 years and clay soils every 3 to 4 years. However, if problems occur during the growing season, send in a soil sample for analysis.