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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
>>