I no longer have the references at hand, but I remember a serious study (INRA ???) which showed that 80 or 90% of the copper brought to high dose in viticulture it seems to me, was found in the 10 first cm.
For my calculation, I took 20 cm.
In the summary you put, it is not clear how copper is applied. Obviously, it seems to be potted trials on cuttings
... Very peculiar. I guess this is the measure of foliar treatments (which can have a phytotoxic effect). The doses are in μM (micro-moles, but μM by what? Liter? Foot? Kg?) ... Unexploitable like that. I did not find the report in extenso to understand.
There is a lot of data in this thesis, with page 25, the soil contents (which interest me), depending on whether it is an uncontaminated soil, contaminated soil plowed (the front actually goes down but it is not more reassuring, even if it is a little less marked - dilution?) or contaminated soil not plowed. We see that we cross the toxic 150 ppm for worms, of course for mushrooms ... And that we are in an order of magnitude having nothing to do with the needs! No need to argue about it to defend copper!index.php? mark_notification = 107168 & hash = c0528c91
PS: I answer, but you note that my intention was to underline the delicate slip of the marketing, which already acts that the copper is also toxic (and thus which dissimulates this in the eyes of the consumer not very curious, but which could have been alerted by the media!)