Thursday, March 26, 2015

Easy Soil Sampler Tool for Compacted Soil

Earlier this spring, we decided we should get our dirt tested.  We carefully selected a lab and read through their sampling instructions.  The only problem was that, lacking an auger or corer tool, we would have had to use our trusty spade shovel.  Why is that a problem?  First, because we would be sampling from places around the yard, many of which we won't actually want to turn over.  Second, our soil is extremely compacted, and digging 20+ holes to a depth of 6-8" would require at least a couple hours of sweat and tears.  Instead, we put on our thinking caps and invented a device from the junk we had laying around.  We still spent a couple hours on the project, but only ~20 minutes were doing the sampling.  The other 80-100 were spent inventing and testing, which will save time in the long run.  (Especially for you, dear readers, because that work is now done!)  Plus, now we don't have (big) holes all over our yard.

The key component of our invention is a piece of old 3/4" pipe, such as this electrical conduit.  But it won't work very well directly as a pipe.  So we marked it at 8" from the end, and cut it as shown.  The closer to one side you can get it, the better, because it will have more rigidity and be less likely to twist when actually taking the samples.  Making a pointed end also helps with that.  Three other tools are needed for easy sampling: a hatchet (or hammer), a vice grips, and a screw driver.  Sample collection is then a three-step process.

Step 1: pound the pipe into the ground, up to the 8" mark. (Step 1a: chase the chickens away because they all think that humans working in dirt = treats.)

Step 2: Take the vice grips and rotate the pipe around to cut a core of soil.  Then pull the pipe back out of the ground, which is much easier with the vice grips still attached.

It should be full of dirt.  Like this!

Step 3: Use the screwdriver to scrape the dirt out of the pipe into a bucket. If there is still residue from the sawing operations, it might be good to take a few samples first in areas you don't care about, and discard them.  Step 4 is to repeat steps 1-3 at least 10 times around the sampling area, until enough dirt has been collected to meet the test lab's requirements.  For us, about 15 sampling points worked out to about two cups soil after drying.

When we first started this, we were afraid that the pounding and scraping would lead to increased metals from the pipe getting into the soil and messing up the test results.  But we took a chance, and the zinc levels (what we would expect to go up the most from using galvanized pipe) were right about at background levels for our area.  (All values in the table are in ppm--parts per million, or mg analyte/kg soil.)  On the other hand, our selenium levels are off the chart!  The level we got was still less than A&L Eastern Lab says is hazardous (that same table appearing in other publications, too, possibly originating from a Cornell report), but more than the level that raises a red flag for UMass, and way above background for our area.  Where could that come from (and what should we do about it?)  Don't touch that dial--we'll be back with more info in a few days.

How do you collect your soil samples?  Let us know in the comments section below!


  1. I love your inventiveness! I wonder if it would be worth drilling a hole through both sides near the top and running a dowel (or something similar) through so you could do away with the vice grips and have a handy handle? Any chance you'd let me steal your story and photos (with credit, of course) for my upcoming soil book?

  2. Hi Anna! Thanks for your comment, and sorry for the slow reply. I bet a dowel through the handle part would work great. We had the vice grips handy and just didn't take the time. We'll have to try it and see if it still does the job. Our yard will be nicely aerated after all this experimenting. :-)

    Also, it would be an honor for one of our projects to appear in your book! I usually compress the photos before uploading them to the blog, so let me know if you need higher res versions.