Neutralize/remove residual weedkiller
 

Hi,

On Sunday, I accidentally and unfortunately used a residual weed killer
in an area where I intend to plant a lawn later in the year. The weed
killer was from an Irish manufacturer (Gouldings "CleanUp") and
contains Aminotriazole (40%) and Atrazine (60%). (Atrazine seems to be
banned by the EU, strange).

Does anyone have any advice as to how I might neutralize the weed
killer? There has been little or no rain and a lot of sun since I put
down the weed killer. The ground is very hard (back garden in a new
build). I've already tried with some success to scrape off the top inch
of soil and then dig over to a depth of about 6 inches to expose
untreated soil. Any idea if this will work?

Jonathan wrote:

On Sunday, I accidentally and unfortunately used a residual weed killer
in an area where I intend to plant a lawn later in the year. The weed
killer was from an Irish manufacturer (Gouldings "CleanUp") and
contains Aminotriazole (40%) and Atrazine (60%). (Atrazine seems to be
banned by the EU, strange).

Nasty persistent stuff. Keeps seeds from germinating properly for about
6 months, and there are regulations about how much you can apply in a
given year.

Does anyone have any advice as to how I might neutralize the weed
killer? There has been little or no rain and a lot of sun since I put
down the weed killer. The ground is very hard (back garden in a new
build). I've already tried with some success to scrape off the top inch
of soil and then dig over to a depth of about 6 inches to expose
untreated soil. Any idea if this will work?

If you are laying turf then removing the worst contaminated top layer of
ground will probably be sufficient. If you are seeding a new lawn then
chances are you would be better off waiting until next year by which
time the active ingredients will have degraded. I think they claim it
gives 6 months protection from weeds if used as directed.

Quick test is try growing some cheap mustard and cress seed on it. If it
grows OK without dying off then the soil is good enough.

I have known people use "Pathclear" or similar as spot weeder on lawns
and then wonder why they had bare bald patches where nothing would grow.

Regards,
Martin Brown

Martin Brown wrote:
Nasty persistent stuff. Keeps seeds from germinating properly for about
6 months, and there are regulations about how much you can apply in a
given year.

I've done a little investigation of Atrazine and Aminotriazole.
Aminotriazole seems to break down in a few weeks, so that's not a
problem. Atrazine, on the other hand, has a much longer half life,
typically about 40-60 days, but this can vary significantly depending
on conditions. Moist soil and sunny conditions seem to increase the
breakdown rate. Non-neutral pH levels also increase the breakdown rate
and I've found contradicting information about whether high or low pH
levels are better (Neutral conditions are bad). The half-life is also
reduced in fertile soil.

Quick test is try growing some cheap mustard and cress seed on it. If it
grows OK without dying off then the soil is good enough.

Thanks for the tip -- I'll give that a try. I'm optimistic that the
very high temperatures over the last week and the very hard ground and
my limited "cleaning" of the area will solve the problem.

Regards,
Jonathan