Neutralize/remove residual weedkiller

[Jonathan]

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?

[Martin Brown]

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.

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

[michael adams]

Atrazine was banned as a result of an EU Directive 91/414/EEC following peer review in 2003

The timetable for withdrawal given by DEFRA(UK) for amateur products containing Atrazine was as follows

24 July 2003 - last day for sale of the product; 31 December 2003 - last day for use of the product; and 31 March 2004 - last day for storage of the product (to allow time for disposal only).

Atrazine has a half-life of 125 days in sandy soil*.

Plastic drums of pesticide sitting in dark sheds, safe from harmful UF light, can have a half-life of upwards of 20 years.

• look on the bright side. At least you only spilt on the lawn to be, and you or your kids didn't mistake it for shampoo or lemonade.

Assuming this cocktail actually targets grass, it may a case of resowing any bald spots - or using lawn turfs instead.

michael adams

...

[Jonathan]

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.

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