Maybe you’ve noticed this sign talking about “Our Legacy of Lead” on our shed, and it’s there for an important reason. One thing Prospect Farm has worked on since the beginning is improving our soil quality. Like any urban green space that has existed alongside roads and highways for more than 40 years, our soil is contaminated from the lead in exhaust, even though it’s been many years since gas has had lead in it. Soil near houses older than 50 years also tend to have elevated lead levels from the paint chipping off over time.

It’s difficult to extract lead from soil, so the most effective approach is to add more to it in order to bring its overall concentration down — things like compost, which is why we maintain our well-organized composting system! We test a selection of our beds year-to-year (Brooklyn College’s Soil Lab is our go-to resource for this), and, for the most part, our numbers have improved a lot. But we’ve noticed in the last couple of years that some beds have jumped back up, most likely from rainwater run-off coming down from the hill where we haven’t remediated the soil.

Lead contamination is of particular concern for young people as excessive exposure to lead can cause developmental problems, reduce brain function, and affect motor skills. Just touching lead-contaminated soils will not cause problems, but what will is breathing in high-lead dust or eating lead-contaminated soil (i.e., by not washing hands before eating). As for eating plants grown in soil with high lead, the Soil Science of America lead info page has this info:

It’s hard to be exposed to lead by eating vegetables or fruits. Plants do not take up lead on purpose, because lead is not a plant nutrient. Plants may contain measurable amounts of lead, but this isn’t because plants are actively taking up lead from soil, but because we’re able to measure very low concentrations of lead in environmental samples.

Additionally, lead is generally more likely to be found in the greens of a plant than fruit (e.g., tomatoes!), so we plant strategically based on our test results. We generally don’t plant any root vegetables in the soil, since it’s hard to wash all the soil off, though we’ve tried a few in containers. But we are looking into other ways of planting safely while we work on improving our soil, like utilizing rain gutters as containers.

We’ve already planted three rain gutters with greens and herbs

Our other experiment this year is straw bale gardening. One of our members picked up a bale from a nearby café’s leftover Halloween decoration, which was helpfully already broken down a bit, saving us some prep time. Then for ten days everyone who came on their watering shift sprinkled the bale with fertilizer and doused it with water to prime it with nutrients. Now we’ve covered the straw with a layer of soil mixed with compost and planted two spots with watermelon seeds. The plants will grow into the straw bale, and at the end of the season, we can mix the remaining straw into the bed to further amend the soil. We’re curious to see how it goes!

Watermelon seeds going in

We encourage members and visitors to be cautious working in and around our soil, especially younger folks. The most important tips from the posted sign are to wash your hands after gardening/playing and be mindful of tracking soil/dust into your home. If you are harvesting veggies, wash them thoroughly before eating. Also keep in mind these hazards are possible in most green spaces in the city!