Re: Glyphosate

neil@[EMAIL PROTECTED]
 wrote:
> On 15 May, 18:57, "Emrys Davies" <m...@[EMAIL PROTECTED]
> 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
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