The Homegrown Mailbox: How and Where Do I Get My Soil Tested?

When you write a book you get questions. In our case, due to the sinking economy in California, they are delivered by Kevin Costner on horseback rather than by email or regular federal postal trucks. No problem, we like questions. A caveat here: like Nancy Klehm, the Green Roof Growers and Black Swan author Nassim Taleb, we prefer the term “practitioner” to describe what we do as opposed to “expert”. We favor experience over speculatifyin’ and make no claims to accuracy. But, we’re happy to take the letters from Kevin, the horse poop for compost and try our best. Here’s one question we get a lot:

Q: Y’all know where I can get my soil tested? I’ve started HUGE garden in my side yard and it just occurred to me that it is where people used to park their cars. I’m concerned about Oil or other pollutants from the cars that might still be in the soil. Any experience with this? Can I test without it costing an arm and leg?

J.R., Los Angeles

A: See my updated response here. [Note update at bottom of this post!] There’s basically two groups of things to test for: contaminants and soil nutrient levels. There are cheap home test kits, but sending samples to a lab is much more accurate. To find a lab in the US, the best place to start is with your local Cooperative Extension Service. Find yours via this link. Some offer free or low cost soil testing.

Here in Los Angeles the Extension Service does not offer testing, but they were nice enough to provide a list of local labs. The lab I talked to, Wallace Laboratories, offered tests at $75 a sample–see their price list for specifics. Before you send a sample talk to the lab to find out what they test for and how much they charge for phone consultation in interpreting the results. If you’re worried about contaminants make sure to describe your situation.

Sampling is a DIY project. You put the soil in a bag and send it off to the lab (they’ll tell you how to dig for the sample and how much to send). You’ll probably need to do several samples since different parts of the yard might have different problems.

In the end I cheaped out and went with Peaceful Valley’s soil testing service for $29.99. No contaminant testing, but the results did tell me that I’m very low in nitrogen, with a soil ph that’s slightly alkaline. They charge for phone consultation, but I was able to interpret the results myself with their slightly overpriced booklet that you can order along with the test.

Another approach, especially if you live in an old house like ours, is to assume that your soil is contaminated, skip the test, and grow things in raised beds, containers or stick to ornamentals. You could also try bioremediation: each season plant a cover crop, let it grow, and then pull it up and dispose of it. Test the soil until it comes out clean. This works well, but it can take many years to get all the contaminants out.

For those of you in Los Angeles, our local Extension Service agent Yvonne Savio kindly sent me the following list of labs with comments.

Biological Urban Gardening Service
PO Box 76
Citrus Heights, CA 95611
(916) 726-5377
URL: www.organiclandscape.com
Email: [email protected]
Organic recommendations, very user-friendly
Owner Steve Zien and I co-author “Organic Matters” organic gardening column in Sacramento Bee for 20 years.

Wallace Laboratories
365 Coral Circle
El Segundo, CA 90245
(310) 615-0116
www.bettersoils.com
Test results very scientific
No recommendations

Soil and Plant Laboratory, Inc.
1594 N. Main Street
Orange, CA
(714) 282-8777

FGL Environmental
853 Corporation Street
Santa Paula, CA
(805) 525-3824

USDA Natural Resources Conservation Service
44811 N. Date Avenue
Lancaster, CA 93534-3136
(661) 945-2604

Here’s a dirt cheap (pun intended) test for soil ph that you can do yourself.

UPDATE: 7/7/09: Visiting journalist Michael Tortorello tipped us off to the University of Minnesota’s soil testing lab will test out of state samples for their regular (low) fee. It’s much cheaper than the services listed above. Their submission forms are located here.

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9 Comments

  1. Raised beds do rule! Not just for contaminants but for those pesky invasives with runners who shudder under my watchful eye in the beds. ;)

    Love the Postman reference. Very cute.

  2. wallace labs rocks. i send all of my client’s soil samples through them. i have had a handful of high lead results here in silverlake/atwater area and would highly encourage anyone growing edibles to either test their soil for contaminants or raise your beds up over 18″ so that roots do not go to native soil.

  3. I sent my soil samples to a university in Boston (can’t recall which one) and it was no where near $75. Again, my memory is sketchy, but $15 sounds closer to the mark.

  4. Hey all–yes indeed soil samples are much cheaper outside of Los Angeles. A visiting journalist told me that his state’s lab will test out of state samples for $15. I’m going to call, confirm this and report back.

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