Martin Brown wrote:
wrote:
On 15 May, 18:57, "Emrys Davies" wrote:
I have read that glyphosate is deactivated when it comes into contact
with the soil. Does that mean that you can spray weeds with glyphosate
one week and then safely plant shrubs in the same area of land a few
weeks later without there being any fears of the glyphosate which was
originally used?

Short answer is Yes.

Actually this is a slightly dodgy claim. It actually depends on the
soil. The glyphosate isn't destroyed on contact with the soil, which
is often how it gets repeated but it gets attached onto clay
particles. If you don't have clay particles because your soil is
primarily peat or sand then it can't happen.

For this to be a serious problem you have to be on wind sorted desert
sands or a perfect pure peat bog. Even a trace of fine clay will provide
enough surface area to lock it down. Extreme cold and darkness will slow
down the final decomposition too.

Also this can't be as
instantaneous as the marketing speak seems to suggest. If it were it
would constitute a risk of fire or explosion. It will take a while

"A while" for physical adsorption onto clay is a fraction of a second on
contact. It is the same sort of thing that makes activated charcoal take
out impurities in tapwater and on about that sort of timescale.

If you want to test it spray some glyphosate onto your soil, take a
sample of the newly sprayed soil and add mustard & cress seeds. If they
grow OK then you have your answer (may fail on peat based composts).

To test the limits you could try planting mustard and cress and using
glyphosate spray immediately for their first watering. I don't know if
they can survive that since it will leave active residue on the seeds
surface.

If your soil contains clay,as admittedly most soils do, then you are
probably OK a week later.

A trace of clay and the soil will lock up and deactivate the glyphosate.
The molecules persist for a while but they cannot do anything.

Regards,
Martin Brown
** Posted from http://www.teranews.com **

So, do you reckon injection by syringe is an effective delivery method
for glyphosphates? I'm thinking particularly of borage where I could lop
off the top of the plant and inject into the main stem as I go. This
would presumably not deliver much volume of liquid but at least it would
be accurately placed. The roots are about a foot long so digging out
isn't really an option.