There are numerous different labs which provide soil testing services, some private, some through Universities. Different labs may have differing requirements for the amount of soil and the packaging, but obtaining an accurate soil sample will generally require the same steps.
Use a clean spade or shovel to collect at least half a dozen samples from various areas of your garden. To collect a sample, dig down about 6 inches and scoop out the soil, placing it in a clean bucket. Mix all the samples in bucket using your spade, but try to avoid touching the soil with your bare hands.
Bring the moist soil inside and spread it out to dry. If you have collected samples from multiple sites, or you want different plots to be tested individually, make sure to keep them separated. Once the soil is dry, carefully measure out the required amount and place in a labeled bag for shipping to the lab.
After the analysis has been conducted by the lab you will receive a soil test report. Most routine soil test reports will include the pH, texture, percent organic matter, Macro nutrient(P,K, Ca and Mg) levels, and if required, recommendations for lime application. Nutrient levels will be indicated as Low, Optimum or High. You can requests addition tests, such as heavy metals, usually at additional cost, but these can be important, especially for urban gardeners. The lab should provide explanations for how the analyses are conducted, and how to read the test report.
With an accurate soil test you can greatly improve the efficiency and productivity of your garden. The information provided can help you choose which crops are best suited for your soil. It will also help you understand how well your soil will hold water and nutrients, and what kind of amendments may be beneficial. And, if you test your soil each year you will be able to track its development. The addition of fertilizers, compost, or cover crops will hopefully be represented in improved organic matter and nutrient levels.
For a list of soil testing labs, click here:
We use and recommend the University of Massachusetts lab since it includes testing for lead without an additional fee.