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Soil testing labs

Sampling soilSoil tests are very helpful for any kind of serious gardener since they give you solid, numerical data about your soil.  You can think of them as a report card, showing you positive (or negative) changes over the years and also pointing out areas that you need to work on.  There's plenty of information out there (like this site) to tell you how to take the actual soil test, and I recommend this in-depth pdf document to learn more about how your test results relate to individual crops.  But the real question is --- which laboratory should you send your soil sample to?

I always recommend starting by checking with your state extension service since most offer free or cheap soil tests.  However, extension service laboratories often skimp on testing micronutrients and heavy metals, so it's worth spending a bit more cash at least once during the life of your garden to get an idea of the bigger picture.

Composite soil sampleATTRA provides an extensive list of soil testing laboratories, but you could spend hours checking out each one's services!  (I know because I just did.)  When it comes to a wide selection of services for a low price, there seem to be four main contenders.

The cheapest option is A&L Eastern Laboratories, which offers a basic soil test for only $8.50 if you skip the interpretation.  (Since most interpretation is geared toward large-scale farmers applying chemical fertilizers, you'll need to figure out what the numbers mean on your own anyway.)  This test will cover organic matter, nitrogen, phosphorus, potassium, magnesium, calcium, pH, buffer index, cation exchange capacity, and percent base saturation.  For an extra $4, you can add on sulfur, zinc, manganese, copper, and boron.  For $15, you can test your soil for molybdenum, which is primarily of interest for those of us trying to increase clover in our pastures.
Take soil sample
AgriEnergy Resources offers pretty much the same tests for quite a bit more cash.  Their basic package is $14.20 and throws in sodium (which you probably don't need) while their higher end package includes the extras from the last lab with the addition of iron for a total of $25.  A separate test for cobalt, molybdenum, and selenium is $46.  Cobalt, like molybdenum, is of interest to clover growers, while selenium is a micronutrient important in our immune system but seldom deficient.

Maine Soil Testing Service is a little more expensive than the cheapest commercial labs --- $15 for their basic test --- but includes nearly all of the extras in the same package.  However, they leave out buffer index and percent base saturation while adding lead.  Finally, testing for nitrogen is $7 extra.  (Although nitrogen is very basic to the fertility of soil, I can see why they leave it out --- you're going to add nitrogen in the form of compost every year regardless and values can shift a lot from day to day depending on microbial activity.  If you're not adding chemical fertilizers or farming on a large scale, I'm not so sure you need to have that information in your test results.)

Mix soil samplesFinally, UMass Amherst has perhaps the best deal of all, especially for urban dwellers worried about heavy metals.  Their base package ($10) has everything previously mentioned except sodium, sulfur, organic matter, and nitrogen (and molybdenum, cobalt, and selenium which aren't available anywhere without paying quite a bit extra.)  Meanwhile, they add in four more metals --- cadmium, nickel, aluminum, and chromium.  I'd pay $15 for the basic tests plus organic matter, though, because I think organic matter is important enough to keep track of long term.  Nitrogen is its own test, available for $15, which I would skip, and I can do without sodium and sulfur.

You'll  hear the results of my soil tests in a week or two, so stay tuned for more than you ever wanted to know about interpreting soil test results.  Why not dig up your own soil sample and play along?

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I started my search online and found grow organic and doing a little research saw they used A&L. Researching a little more online (and due to our County Extension having some odd hours) I found an A&L branch in our town.

The grow organic website has a PDF for understanding the soil report. I found it through a google search:

It saved me a lot of time and helped me figure out the quantities for ammendments.

How often do you test your soil? We did it last year and did 3 different tests (3 parts of our small quarter acre yard; existing garden, and two future gardens.)

Comment by Brian Mon Oct 10 17:06:01 2011

I was going to use A&L, but I liked the extra tests UMass offered. We don't test much, though, or I would go with the cheapest option. We tested our soil once (through the extension service) before we put in our first garden, but I've just about mined that data as far as it will go so, six years later, am testing again.

I figure the frequency of testing should depend on your needs. If your garden looks happy and is well established, you might get away with testing every 5 years or so, but in new areas (like our experimental chicken pastures), I'll probably test every year or two for a while to get a real handle on changes.

Thanks for the link to the pdf! That looks extremely helpful, and I'll enjoy comparing it with whatever UMass sends.

Comment by anna Mon Oct 10 18:18:14 2011
Thanks for the info on these facilities. I've been thinking of getting our soil tested for some time now. I just haven't gotten around to it. Maybe this extra info will help me get to it.
Comment by Fritz Monroe Tue Oct 11 11:43:17 2011
If it makes soil testing any more enticing, I'll probably run a lunchtime series when I analyze ours. If yours is ready around the same time, you can learn from our experience. :-)
Comment by anna Tue Oct 11 13:30:33 2011
Where is the extensive post where you analyze your soil test results? also I think your Mom's soil test was in there too. Can't find it with a search. Or is it in one of the Weekend Homesteaders? Thanks!
Comment by Dave V Sat Mar 24 04:52:22 2012

Dave --- I need to make some kind of link-back on posts like this, so that they list the later pages that link to them. The followup lunchtime series starts here (with later posts linked from the end of that post). There is also a slightly more polished/elongated version in Weekend Homesteader: January.

Comment by anna Sat Mar 24 08:39:15 2012

One very unique homestead, $1,500 per acre, the opportunity of a lifetime