On Wed, Mar 27, 2013 at 11:47 AM, Bill T <[log in to unmask]> wrote:

>
> Yes, the issue is amount,. Half life means little if the concentration is
> small (point source) rather than uniformly distributed, such as a spray.
>

You push a coated seed into the ground.  Some of the coating abrades.  Some
moves off the seed with water movement.  The seed germinates and the
systemic moves throughout the stem leaves and roots.  The seed is gone.
There is no more point source.   The roots are throughout the soil.  Some
of the above ground material may or may not be incorporated in tillage or
if no till just through degrading.  If it is a dry year and the crop is
ploughed down, which is what happened in many corn fields I understood from
Bob's posts, then all the material  goes back in the soil.

There is no point source once the seed is gone.  I think it is a non issue
and that is why none of the regulators considers it.

But there are other legitimate losses of material from the soil ecosystem
to consider when you are looking at soil accumulation.  Some of the
material is removed in the harvesting of the crop.  Some of the material is
removed by photodegradation in the crop.  When you look at half life
figures there are many of them given: aerobic in soil, anaerobic in soil,
degradation in water, and photodegradation.  But there is no doubt that a
portion remains in the soil and in some types clothianidin breaks down
painfully slowly.   That was one of the main problems with DDT.

Stan

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