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Before you add anything to your soil or plant anything in your garden this year, answer one question:

When was the last time you had a soil analysis done? Five years ago? Ten? Never?

Soil analysis tests are an investment—usually $10 to $15—but I can almost guarantee that you will recoup that money several times over by not adding things to your soil that it doesn’t need.

Just to be clear, I’m referring to a soil analysis done by a lab, not one of the little kits you pick up at the hardware store where you mix something that resembles and Easter egg dyeing kit with tiny bits of soil. I think those are probably better than nothing and are a bare minimum if you are gardening in a new place. Of all the things you need to know about your soil, the acidity level is the most important in my opinion, and those little kits can give you a pretty good idea of where that is at.

When you take a soil sample, dig down about 4 to 5 inches and sample from several places in your garden. 

Most labs that do soil testing focus mostly on agriculture testing or environmental testing for things like Chromium (“Erin Brockovich,” anyone?), but they also do simpler tests aimed at homeowners. But you won’t necessarily hear about them until you go looking for them.

To my knowledge, every state has a public university extension program and they will either be able to test your soil at a state lab or give you a list of labs that do the testing (if you’re in Canada, here’s one list of soil labs I found). Just do an Internet search for “University of (your state) extension” and once you get to the extension website, do a search for soil test. If that fails you could search for a nearby state’s lab and ask if you could send your sample there.

It’s important that you take a sample properly. Some labs provide sample bags but most that I know of are fine with a sample in a regular old Ziploc bag (well, actually a new bag because you wouldn’t want anything else contaminating your sample).

A Ziploc bag works fine, but some labs also provide wax-lined sample bags.

When it comes to taking a sample, don’t be greedy. Different areas of your yard could have very different soil depending on fill that might have been used, what has been growing there, or how you’ve amended the soil over the years. So stick to an area that you anticipate will have consistent soil. You want to take small samples from about five different areas within a bed (assuming you’ve identified that as your test area) for a total of about 2 cups of soil. A trowel will do just fine for this job. Just dig down to about 5 to 7 inches below the surface and bring up a bit of soil. Then use just the “core” of what comes up on your trowel to add to the sample bag.

I took samples from two gardens and you can even see the difference in the soil. The top sample is from the small garden between the patio and the house that, despite having great growing conditions, does not produce plants that thrive, leading me to believe there’s something wrong in the soil. The bottom sample is from the main garden.

Label your bag and fill out the sample submission form. If you are sending more than one sample, make sure to label them in a way that makes sense to you. I used “Patio garden” and “Main garden” as well as assigning each a sample number as required on the form I sent in with them.

Speaking of forms, there will usually be one to fill out and send in with your samples, so make sure you do that. Most labs will also ask for what kind of planting is destined for the area so they can offer amendment recommendations.

Labs will have submission forms for download on their website. Make sure to fill it out and mail in with your samples.

I recently sent two soil samples in to the University of Wisconsin Soil Lab. The first is from the skinny garden between the house and the patio. This three foot strip of dirt is deep and gets full sun. It might be slightly dry because it is a little under the eaves, but I make it a point to water it. And even though sun-loving plants should thrive there, they don’t. They grow, but nothing is truly happy there. Which makes me wonder if something is going on with the soi. I will probably dig out all of the dirt there and replace with with really nicely amended soil, but if there is something leaching into the soil, that should show up in a soil test.

I also sent a sample from the main garden, just because I’ve never tested that area.

Depending on how busy the lab is (I’m hoping I beat the spring rush), I expect to get results and a list of suggested amendments in a couple weeks. It should be interesting.

Have you ever tested your soil? What did you learn?

6 Responses

  1. I sent three soil samples away for testing yesterday. I've been meaning to do this for years, but I'm planning on landscaping a large part of the property now and I really want to get an idea of what is most likely to thrive in my soil before I purchase the plants. I can't wait to get the results.

    1. My results are due today and I'm oddly giddy with anticipation. This is probably a sign that I've truly gone off the deep end, but there's not too much to be excited about in the garden this time of year.

  2. We did it at our first garden which was small. I don't remember if we did it here, but with a half acre that is completely gardened I think we did not bother. We used to generate a lot of compost, had access to aged manure etc. So we did a fair amount of early improvements. Now we just pretty much add leaf mulch.

    1. We're going to get a huge bagger attachment for the riding mower that should mulch and bag leaves much more efficiently than we've been able to do until now. More and more, I think leaf mulch is such an important amendment for the garden.

  3. In spite of going through the Master Gardener program (where we learned about this in detail), I've never had my soil tested. In recent years, my vegetable growing has been less than stellar, and I'm pretty sure it's because of the soil. Time to do this!

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