From: klier@iscsvax.uni.edu
Newsgroups: rec.gardens
Subject: Re: glyphosate and composting
Date: 9 Apr 92 17:13:50 -0500
Organization: University of Northern Iowa

Chris at Ecology Center Fund <ecologycntr@igc.org> writes:
> 
> Thanks for the info, Kay, and let me retroactively edit my diatribe to say
> that _I_ didn't know of any info on breakdown products, not that there _was_
> no info.
> 
> Other questions:  what effect do differing edaphic conditions (soil pH, parent
> material, soil moisture, etc.) have on rhizobial metabolism of glyphosate?

Can't answer that, since I've only read the abstract of the rhizobial 
metabolism paper.  Various species of Rhizobium can survive in almost any
soil type, so parent pH and chemical composition shouldn't play a major role.
We played with it long ago in a microbial diversity or microbial physiology
class, and could get all sorts of soil bacteria to use glyphosate as their
only source of phosphate or their only source of carbon, or their only 
source of nitrogen.  I recall making an agar that had glyphosate +
some inorganic minerals and getting all sorts of bacteria to grow.  I 
think I isolated 20 or 30 different species of bacteria that did quite
nicely on that.  So it's not just Rhizobium that will "eat" glyphosate.

Things that generally influence microbial decomposition include available
moisture, oxygen content and temperature.  The more of any of these, the
faster most bacteria will grow (and metabolise).  Of course, there are
limits for each factor for each species of bacteria, but soil populations
are generally large and mixed.



> Has there been recertification testing done on Roundup since the original
> testing done by the infamous Industrial Bio-Test Laboratories (whose chief of
> staff admitted to falsifying results of thousands of tests?).  
EPA is supposed to be in the process of retesting all sorts of herbicides and
pesticides under supervision of their own scientists (though most of it is
being contracted to university researchers, if I recall right).  I heard 
they were starting with the things they most susconfirmation of breakdown
into inorganic phosphate and methylglycine, I doubt it's high on the list.
Remember, though, Roundup is glyphosate + a bunch of "inert" ingredients,
trade secret, and we don't know what all goes into the brew.  I can tell you,
though, that I did "patch test" myself with Ortho's Kleenup, a prediluted
glyphosate sold to homeowners (it's very difficult to get permission to
run human tests of anything, but no one says you can't be your own guinea
pig).  No reaction after 24 hours of exposure of skin at the inside of my
arm.  I have skin that breaks out or falls off after exposure to almost
anything, so I'm _guessing_ that that formulation isn't too nasty.

> And the big one:
> Why spray when you'll have to pull the weed anyway?

I use glyphosate under 3 or 4 major circumstances.  None of them involve
pulling weeds.

1) killing obnoxious or noxious woody vegetation that cannot be easily
  handled.  e.g., poison ivy around latrines or cabins in a children's
  camp; killing aspen or dogwood clones on prairies (where these most
  certainly do not belong).      
2) killing perennial weeds with a large possibility of overwintering or
  reestablishing from vegetative fragments left behind by pulling.
  e.g., my research plots of freeze-resistant johnson grass after the
  study wcompleted; killing yellow nutsedge in my mother's lawn
  (newly introduced).
3) selectively killing introduced species in areas of native vegetation
  e.g., garlic mustard (which is spreading like wildfire from the
  eastern US) in state parks and preserves; yellow and white sweetclovers
  in prairie preserves; bluegrass in prairie preserves.

All of the above involve application of glyphosate to _individual_
plants -- very controlled, minimal dosages, no slop to non-target organisms.
Most of us who do this don't even drip on the soil!   The plants are left
to rot in situ.

4) Killing ALL vegetation at a site so that it can be reseeded with minimal
weed competition.  e.g. (done once), wiping out an entire back yard that
was 95% weeds so it could be tilled, graded and reseeded; (done several
times) wiping out old pastures or weedy vegetation in roadside ditches
so that the area can be reseeded with locng out a back yard (95% weeds) so
it could be tilled, reshaped, and reseeded; (done many times), wiping out
all the vegetation in an old field or roadside ditch so that the area
can be reseeded with locally collected seeds of native plants (essentially
a native plant germplasm preservation effort).

We don't pull the weeds there, either -- we're often talking 5-20 acres
at a time!

Kay