Where do lawn chemicals go?

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Michael Wise
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Where do lawn chemicals go?

Post by Michael Wise » August 28th, 2016, 10:29 pm

Sorry if this is not the right place for this question. I always struggle with where to put "general" non climate specific questions.

Assuming they are applied responsibly, at or below recommended rates, where do they go? Perc down? Microbial breakdown? Other breakdown? Stay there forever?

Is it different for every chemical? Fungicides, PGR's, herbicides, insecticides, etc.?

Is there an accumulation? Or do yearly maximums prevent this?

Do some chemicals "go away" better than others?

Every question doesn't necessarily need an answer. Just wanted to make it clear what I'm wondering.


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andy10917
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Re: Where do lawn chemicals go?

Post by andy10917 » August 28th, 2016, 10:39 pm

It varies, a lot. Some items break down into "metabolites", and the metabolites may be harmless or cause problems. The time it takes to break down can be a few days or a year. Getting to the water table or building up in composts can be a real problem.

Billy
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Re: Where do lawn chemicals go?

Post by Billy » August 29th, 2016, 7:33 am

That's a good start, Andy. We can think of a lot of things that can happen to things we put in the environment, but it all comes around to a few basics:

1) Something eats what we apply and metabolizes it
2) Something eats what we apply and it remains unchanged
3) Water (rain) carries it off
4) It adheres to the soil
5) It volatilizes into the atmosphere
6) UV light degrades it

Most materials that we apply are eaten by something -- plant, animal (microbes), fungi. When these materials are consumed, they change form during the metabolic process. Because many of the pesticides we apply are organic chemicals (the scientific meaning or organic, not the tree-hugger hipster meaning of organic), they are broken down into mostly CO2 and water.

If you're interested in how persistent some products are in the environment, check out the SDS info for the products you're using -- sometimes that info is listed there. If not, sometimes you can find it at extoxnet or NPIC. A common pesticide people on this board talk about is prodiamine, which has a half-life in aerobic soils of about 2 months. Another common pesticide is 2,4-D, which has a half life in aerobic soils of just about 2 weeks. If you dig into the EPA registration documents for these materials, you can find even more info.

The long and short of it is that nature doesn't like to leave things unchanged. Weather, environment, and living things (mostly fungal and bacterial microbes) act on everything we put in the environment and break it down over time.

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