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Dear Jeff,
I work at the the Regional Food Bank of Oklahoma. We currently
have a composting area at the food bank, but we are looking
at expanding it and starting to take in grass clippings from
a local landscaping firm.
We are concerned because some of these lawns would have had
pre-emergent and other herbicides used on them. We wanted
to know what your opinion is on how this might affect our
compost. If you have any research or web sites that you can
refer me to so that I can do future research on this matter,
it would be very helpful. Thank you in advance for your time
and help in this matter.
Casey McKinney
Regional Food Bank of Oklahoma
Urban Harvest Marketing and Development VISTA
Dear Casey,
Here is what I know and how that knowledge effects our own
compost operation:
Most pesticides used on lawns and trees decompose in the
composting process. This is partially a product of the heat,
but more significantly occurs through the activity of the
microbiological action. What these materials break down into
is still unknown. That being said, all organic certification
organizations recognize composting of these materials as an
allowable function.
A certain lawn herbicide called clopyralid, used to control
broad-leaf weeds, has been shown to be resistant to breakdown
through composting. This fact was discovered in Washington
State. Since then, other states have discovered the same problem.
Clopyralid is generally not an issue in field situations,
since the amount in any one spot is very small. It does become
an issue in flower pots, containers or greenhouse operations.
For that reason, we here at The Rodale Institute never use
any compost that contains any grass ingredients in our greenhouse
operations. Any compost containing grass clippings is used
for field crops only.
I always recommend that interested individuals contact their
own state Extension specialist in composting, since they have
the best regional information. Then, on a national level,
I suggest the journal Biocycle,
at JG Press, Inc., in Emmaus, Pa., as the leading authority
on compost.
Good Luck,
Jeff
Have some questions to Ask Jeff? E-mail
him directly at jeff.moyer@rodaleinst.org.
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