From Permacltur@aol.com Sat Apr 10 14:55:29 1999 Date: Sat, 10 Apr 1999 08:31:37 EDT From: Permacltur@aol.com To: rachel@devnull.net, owner-permaculture@envirolink.org, permaculture@envirolink.org Subject: Re: Lead bioremediation in gardens Well, Rachael, I'm afraid there are no generalities one would want to trust. Around 1980, Clark Nickelow, then (and maybe still) of the Waltham Field Station, Cooperative Extension Service, Waltham, Massachusetts, had opportunity to do analysis of soil and tissue of crops grown on the soil. He was keeping records, but so far as I know he never published. Maybe y ou can run down Clark, or see if the field station still has the records. (You can probably get your local extension service to run down an adress, or maybe that is enough info for a phone call.) We (Massachusetts Food and Agriculture Coalition) has pushed through the legislature funding so that inner city gardeners could get spectrographic analysis of soil and crop tissue for $5/test. (The rest of us paid $20 or something like that.) So he had the opportunity to test many samples of both. Moreover, Ted Live, who worked in one of the State community agencies (forget the name) was distributing seed to people in standard assortments (also state funded courtesy of MassFAC) so there were a lot of the same varieties comming up that helped a lot in getting trends. Clark determined that lead uptake of vegetables differs markedly not only by species, and by plant part, but also by VARIETY! So variety X of tomatoes will always take up less lead than variety Y. I don't remember any of the details. Also, certain root crops take up lead in the main tissue while others take it up mainly in the peel. So the food is safe if you peel it. Beets and carrots were the comparison Clark used (this is all from one conversation I had with him incidental to the main business of my visit), and I THINK I remember that it was beets that you peel. But I wouldn't bet my health, or anyone elses, on the recollection. If all that data has been thrown away, which is the most likely scenario, then you need to start over. This time publish results in our journal (The International Permaculture Solutions Journal), where it will be ever available to people. Meanwhile, back at what you absolutely can do, there are several fail-safe remedies. 1) Import soil for raised beds. Far fetched? Boston Urban Gardeners were getting contractors to do this for their gardeners at least as far back as the 1970s. They also get organic matter and even manure hauled for free, often as backhauling so the added energy cost is much less. BUG is a non-profit, so there are tax writeoffs for contributions of goods and services. 2) Build soil-less gardens. There are two or three basic types. One is basically gardening in mulch. Barbar Daniels of CA has done this with rooftop gardens and using containers. Basically, she applies deep mulch to a surface, usually an impervious surface, and innoculates it with some topsoil (very little, a sprinkling). She sets out plants in pockets of soil and fertilizes and irrigates everything with dilute urine. Her method was written up in a back issue of the Activist and we have an article on file to publish in an upcoming isue of TIPS journal, too. A very similar method is what I call dryland chinampas. This is written up in Vol. I, No. 3 of TIPS (The International Permaculture Solutions Journal). Again, this would require much less imported soil than regular raised beds. Basically, you make a bed of any shape you like (can be a spiral or concentric circles or straight beds, etc) using thick layers of mulch alternated with thin layers of soil, topping the whole mess with about 2 inches of soil. Plants can be seeded or transplanted into this. In Wichita, Kansas, we built a whole system of these beds using yard waste we picked up by beating the city truck on trash day. Grass clippings are especially useful, and I like green matter for these beds when I can get it. I take clippings next to lawns with weeds--no herbicides. A certain amout of brush trimmings with green leaves attached are ok for the bottom layer. 3) Straw-bale gardens. These are described by Robert Kourik in DESIGNING AND MAINTAINING YOUR EDIBLE LANDSCAPE, NATURALLY. The bad news is that this book is out of print. The good news is that we bought out Bob's inventory of damaged copies (very slightly damaged). Inthis method, a high nitrogen fertilizer is placed on the surface of straw bales and then they are covered by 4-6 inches of soil and planted in. Regular watering is critical. I like to soak the bales down before I start. (Did these in Kansas too.) Don't use hay--it will rot too fast and you will have an awful mess. (I made that mistake when I couldn't get straw in Georgia.) It also heats up too fast an cold cook your seedlings. You can skip the N if you plant legumes that you innoculate. We got phenomenal crops of Christmas limas this way. (That's a variety, not the harvest season.) All methods of soilless gardening require rigorous attention to watering. This is at odds with realities of urban gardens of this type, which are always in zone 3 or 4 for the residents, when ideally they should be no further than zone 2. If you have no capacity to irrigate at will, forget it. And only DEDICATED gardeners should use this system out in zone 3 or further. Just because you want a zone 1 garden in zone 3 doesn't make it a zone 1 garden. The zone system does not slide to accomodate the inconveniences of urban living. This is the commonest mistake in what sometimes passes (alas) for urban permaculture. For anyone else out there contemplating such a situation, this project would be way better off if they had NOT removed the tarmac, which sealed off the toxic soil (you can remove a few small areas for tests of course), and used soilless techniques. Finally, the application of all this organic matter will definitely reduce lead uptake. Also try to keep soil pH between 6.5 and 7, again to reduce lead uptake. Happily, most garden crops like this pH best anyway. I hope I've been helpful. I don't have time for a continuing dialog on this (unless you have consulting funds), but I think I've given you enough information to dig out any further data that you need. Try to get a local college to take this on as a research project and generate your own lead uptake data. (You do have to throw away some crop.) OK, one more point. Back sometime prior to 1980, when I heard about it, a graduate student at Columbia University did a study of heavy metal uptake in NYC urban gardens. As a "control" s/he measured heavy metals in supermarket produce. S/he found that the supermarket vegetables were "heavey" in cadmium and the garden produce "heavy" in lead. Given different forms of toxicity, it was a toss-up as to which vegetables are more toxic. In that situation, why not grow your own, improving the soil (which makes it less toxic), gaining a measure of self-reliance, and making the urban environment more liveable. But steer clear of carrots. By the way, CA has a huge surpluse of rice straw. For Mother Earth, Dan Hemenway, Yankee Permaculture Publications (since 1982), Elfin Permaculture workshops, lectures, Permaculture Design Courses, consulting and permaculture designs (since 1981), and annual correspondence courses via email. Copyright, 1998, Dan & Cynthia Hemenway, P.O. Box 52, Sparr FL 32192 USA Internships. YankeePerm@aol.com We don't have time to rush. A list by topic of all Yankee Permaculture titles may be found at http://csf.colorado.edu/perma/ypc_catalog.html Elfin Permaculture programs are listed at the Eastern Permaculture Teachers assn home page: http://home.ptd.net/~artrod/epta/eptahmp.html In a message dated 4/9/99 7:24:39 PM, rachel@devnull.net wrote: << I'm helping to start a garden on a site that was a parking lot. After depaving, we got the soil tested for lead and it came back with 700 ppm. Some extension services say this is "safe to garden" as long as you wash everything with soap and don't grow roots or greens - in other words almost no cool-season vegetables. We're going to do more detailed spot testing to see if it's only in certain areas, and if it's just one spot we'll probably dig that out and fill it with city compost. In the meantime I am trying to find out what we can do, particularly what crops are safe to eat, and what we can grow that would accumulate/concentrate the stuff that we could then harvest and landfill (or smelt!). I heard of one person who grew a particular variety of corn on a lead-contaminated site, then smelted the corn to obtain a lead ingot (it was an art project). The extension services all say corn, like other fruit/seed crops, is safe, but maybe the lead accumulates in the stalk and husks. I would love to find out what variety of corn this is. If you have any advice, contacts, books, etc, to suggest, I would be grateful. Thank you, Rachel Freifelder Mariposa Grove Community Garden 828 59th St Oakland, CA 94609 510-655-2936 rachel@devnull.net >>