Soil Chemistry Testing Home Activity: I dread there’s lead in my garden bed!

Soil testing activity for kids

Digging in the backyard dirt to do some soil chemistry testing.

For a budget of maybe $20-30, this is a useful and fun science experiment that you can do with your family and friends at home, if you have a yard and/or garden. Not to mention, this is something that can help improve your own health, as well as the overall health of the environment you live in…

Things you’ll need:

  • About $20-30 depending on how many soil tests you’ll do; it costs about $10 for a basic soil test, plus you’ll need a budget for mailing, or you may be able to bring it to your local extension school in person; generally it’s best to do more than just one soil test to calibrate your results.
  • a big plastic bucket
  • some trowels or soil sampling tools
  • ziplock bags, a permanent marker, and padded mailing envelopes

Well, it’s that time of year, when I go out and start preparing soil for my various gardening experiments of the year. Because I have recently been moving around and am now establishing a new home garden on a slightly bigger scale, I decided to go out and do some early soil testing on a new area of land that I want to use for planting veggies and herbs.

Beautiful things in the garden

These are all pictures from my own gardens, of some of the interesting and beautiful things I have grown in recent years…

First, I found my local “extension school” for agriculture and soil testing, at my closest state university (University of Massachusetts), and looked up their forms and testing procedures. According to the UMass extension school, the best soil samples are from garden-sized areas, where you take 10-15 “subsamples” and mix them together. When sampling, you use a clean trowel or sampling device, and take soil from the entire soil profile, where roots and/or rooting vegetables may end up growing, which is up to 6″ deep. Then place the samples in a big clean plastic bucket.

Soil testing

Dig at least 6″ into the ground and get even amounts of soil from all levels of soil to get a proper soil test result. Here, the soil was placed into a regular plastic shopping bag.

I identified a few potential garden sites from all around the backyard and started taking subsamples. I mixed subsamples in a large bucket, and was sure to clean the buckets and trowels between different samples. On a map, I identified areas which I sampled, so I could be sure to know where exactly I would set up the garden.

Mixing soil subsamples for a soil test

Mix soil subsamples thoroughly in a large clean bucket, to get proper results; only a small amount of soil is used to do a soil test so it’s important to make sure you mix thoroughly at this stage

Since it’s been snowing off and on a lot this year, the soil was somewhat on the wet side, so according to the extension school instructions, I used a fan and blew the samples for a day before mailing. Then after making sure the samples were once again thoroughly mixed, I placed about 1 cup of soil into ziplock bags, and labeled the regions where I obtained the samples and mailed them to the extension school, along with a check for the sampling.

Labeling the soil samples and filling out the testing request form

Labeling the soil samples and filling out the testing request form

Well, to my surprise, I found that the soils were quite acidic and would need a lot of dolomitic limestone added to it, in order to make sure all nutrients would be available to the young plants. I would also need to fertilize the soil a bit to make sure enough nutrients will be available to the plants as they are growing. (These tests are really quite extensive for just 10$ – you get Phosphorous, Potassium, Calcium, Magnesium, soil pH, Boron, Manganese, Zing, Copper, Iron, Sulfur and more — they even provide you with specific recommendations for how to properly fertilize your soil).

Soil chemistry test results

Normal soil chemistry test results, from one of my samples; this one had around/under 100 ppm of lead, which is considered in the “low” and normal range

But even more surprising – I found out that one of my 3 samples was slightly contaminated with lead! How could this be?

Lead-contaminated soil sample test results

Lead-contaminated soil sample test results – as you can see here the lead tested at over 330 ppm, which is considered “medium range” but way higher than normal conditions in nature

It turns out lead is not as uncommon as people think in soils, and it can be very dangerous to young children, pregnant women and older women, in particular becuase of the potential for osteoporosis. If there are even medium levels of lead in the soil, it is best not to grow vegetable plants there, and if you do, you should avoid leafy veggies and stick with tomatoes, eggplant, beans and related vegetables which do not absorb as much of the lead.

Where does the lead come from? Often it comes from old house paint, which has been scraped off or “de-leaded” from an older house. If your house is new, but has been built on a place where another house once existed, your soil can still be contaminated today. But, it can also come from places where older leaded fuels have been dumped, or where older lead-based pesticides were used, or any number of different industrial sources. In fact, there’s really no way of completely knowing where the lead came from — and more important, just by looking at soil, there’s no way to know if it’s contaminated. So, before you grow something you may eat, you should test your soil. If you are in a high risk group, you should also be sure to use gloves and wash your hands thoroughly after touching soil.

So, I have lead in my soil — what can I do? There’s a number of things you could do. For instance, in my case, I have several regions with very low lead, and only one area with high lead. My plan is simply not to plant vegetables in that area, but perhaps some flowers. But there are other things that can be done, for instance:

  • Bioremediation: you can grow plants which absorb lead, and then find a way to dispose of the plants through a service which eliminates biohazards
  • Use a large amount of gypsum/limestone or other Ca based soil additive which will raise the pH and then plants will tend not to absorb as much lead
  • Grow plants which do not absorb much lead, like tomatoes, eggplants, beans or some other non-leafy veggies; please check on lead absorption first
  • If the lead is very high, you may need to call your local health and environmental protection departments, to assist you with remediation

Lead is a very serious health concern – so be sure and test your soil before you start playing with it, or growing food in it!

Barnas Monteith has a geology background and is author of THL’s Furious Case of the Fraudulent Fossil.

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Mar 17, 2013 | Posted by in Cool Activities, Uncategorized | Comments Off