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Lead In Our Soil…

This is our plot in the summer of 2009 when we started preparing the space for the next planting season.

As David shared in a previous post we did a soil test through the University of Massachusetts and found that the lead levels in our garden soil were dangerously high. The extrapolated levels as reported by U Mass were 488 ppm (part per million). The high end of the safe contact threshold is 300ppm. We did a subsequent test through a local lab that does a lead specific test and they reported that our lead levels were as high as 600ppm! For the most part veggies and fruits dont absorb lead deposits in the soil so fruiting crops may be safe to grow and eat. On the other hand the levels are high enough for us to be concerned about our children being exposed to the soil and the safety of any root veggies we might want to grow. We want this to be a family friendly project and instilling earth friendly values in our children is of the utmost importance. It would be a shame to have our children sitting on the sidelines because the soil is not safe for them to be exposed to.

There are many ways of addressing this issue. We can mulch the entire garden area with a couple of layers of cardboard and a foot or so of wood chips. With this serving as an effective barrier covering the contaminated soil we can then install raised bed gardening plots. The downside to this for me is that it essentially amounts to sweeping the problem under the carpet.

Another option is excavation. We would have to rent equipment, hire laborers or commit to excavating the soil ourselves. This would entail digging up substantial portion of our yard. Right now the plot that we prepared is approximately 12′ x 24′. Ideally we would excavate to a depth of about three feet or so. Do the math and that amounts to a minimum of 864 cubic feet of soil that we would have to excavate an safely dispose of. Not small task in terms of labor, logistics and cost!

Earlier this month we returned to our plot to turn over the soil and get it ready for seeds.

Another option is phytoextraction. Yes, it is a fancy word and to be honest I just learned it a few hours ago. It basically amounts to planting crops that will absorb lead from the soil. I first came across this strategy while working on assignment covering the aftermath of Hurricane Katrina and the flooding of New Orleans. Hands On New Orleans had a city-wide operation of planting sunflowers as a strategy for extracting heavy metals and toxins from the soil. It was a pretty impressive operation and it immediately came to mind when we got our soil report.

The down side to phytoextraction is that it is a slow process and, in our case, may take up to 7-10 years to reduce lead contamination to acceptable levels (from 600ppm to 300ppm at least). The up side is obvious, it restores the soil, provides a labor and cost accessible option for families of limited means, and sequesters the lead in a vehicle that and be reasonably disposed of.

If you are interest in learning more about phytoextraction and its potential here are some good links:

The Food Project – Soil Testing & Remediation

Blue Dominos – Phytoextraction

Botanical Cleanup Crews

We are very excited about learning how to grow fantastic fruits and veggies for our family. We really want our children to have this experience shape their core values.

We had some beautiful starts in the ground and they are doing beautifully. Our soil is rich, has a good mixture of silt and sand and seems to love our starts. Lead is the secret menace!


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