How to get your soil tested, including free options

Where to get soil tested

Every state has a land-grant university with a cooperative extension service, and most run or partner with a soil testing lab. Search for your county name plus "extension office soil test". The office will have sample bags, a form asking what you plan to grow (the recommendations depend on it) and either a mailing address or a drop-off box. Results usually come back by email in a few weeks; one Wisconsin office notes that results have recently taken 4 to 5 weeks, so spring is busy.

Private agricultural labs test soil too and are handy if your state has no public lab. Make sure the report includes recommendations, not just numbers.

Free soil testing options

Free testing exists but is local, so ask your extension office before you pay. Examples we found:

North Carolina: the state agriculture department tests soil free for residents from April 1 through November 25, and charges $4 a sample from December 1 through March 31, according to NC State Extension in Buncombe County.

County programs: some counties fund free tests for residents, such as Johnson County, Kansas through K-State Research and Extension. Master Gardener volunteers and Cornell Cooperative Extension offices also run free pH testing days at farmers markets and garden events in some areas. These quick tests usually cover pH only, which is still the single most useful number.

How to take a good sample

The lab can only test what you send, so the sample has to represent the whole area. Most extension labs ask for the same basics: use a clean trowel or soil probe, take 10 to 15 small slices across one area (one lawn, one vegetable bed), go about 6 inches deep for gardens and 3 to 4 inches for lawns, mix them in a clean bucket, and send about 1 to 2 cups of the mix. Skip spots that are obviously different, like where a brush pile burned or fertilizer spilled, and sample separate areas separately.

Fall is a good time: labs are less busy, and lime added in fall has months to work before spring planting.

Are home soil test kits accurate?

University of New Hampshire Extension says home kits and handheld meters typically are not as accurate as a lab, with accuracy varying by kit and by nutrient, and that a lab report gives tailored lime and fertilizer recommendations a kit cannot. A kit is a reasonable first look if you have never tested, with a lab test to follow. Inexpensive pH kits are the most useful part of most kits.

Reading the results

Start with pH. Most vegetables and lawns do best around 6 to 7. Below that, the report will call for lime; above it, sometimes sulfur. Then look at phosphorus and potassium, which are reported as low, medium or high, and the recommended pounds of fertilizer per 1,000 square feet. See typical topsoil pH in your state and what to add to garden soil for what to do next.

Routine tests do not check for lead or other contaminants; the Wisconsin lab, for one, says it does not test for lead. If you garden in an older city neighborhood or near an old painted building, ask your extension office where to get a lead test.