In message , sw
writes
Nick Maclaren wrote:

In article ,
PA wrote:
thanks every one for your input, I'm still in two minds though....
the bit I don't get is: if no residue is left in the soil, what about when
the roots of the weeds start to break down wont they release chemicals,
which will be then taken up by whats ever growing?
the trouble is I've got about 450 square meters to clear and its taken about
an hour to do one properly
and now I'm dreaming of roots

No, because it will be released into the soil, where it will be broken
down by bacteria. Apparently, some breakdown products disappear very
slowly from the anaerobic sludge at the bottom of ponds, but garden
soil has a very different (and much more vigorous) collection of
microorganisms.

ISTR the most potent breakdown pathways are in soil fungi...

But even so glyphosate is only lethally effective when it hits living
green plant tissue. It can hit bark or roots in normal soil without any
effect.

I'd thought there was some research suggesting it doesn't break down in
soil quite as thoroughly/quickly as was originally believed? Or is that
more a concern where fields of GM-HT crops are resulting in higher
usage?

The research which shows it breaking down very slowly was in extreme
environments where *nothing* organic breaks down quickly either because
it is desiccated, deep frozen, deoxygenated or a combination of all
three.

I am no fan of gratuitous GM style use of glyphosate on field scale to
annihilate all weeds. Not least because I fear it will inevitably lead
to the development of resistant superweeds. But for the moment
glyphosate is as close to a safe environmentally friendly weedkiller as
we have ever managed to come. I favour minimum inputs horticulture.

Regards,
--
Martin Brown