There is no distance that I am aware of, only barrier.
This was something that always fascinated me about organics and the USDA.
But, then I began finding the same in other areas as well.
So, a barrier is as simple as a separation wall or a field.
I had a client that grew onions - organic and conventional and his barrier for storage was a wall and the field barrier was a road and on the other side conventional onions.
Walking thru a Whole Foods market one day I was amazed to see conventionals right nect to organics and the only separation was a cardboard display piece.
When I jokingly said to a store worker, I guess they get mixed up a lot - to which the worker said all the time and when they don't come in with stickers on we just guess which side of the barrier they go on.
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