When I was in pesticide...school, grins, there was an instructor who laughingly said you could drink this stuff. ha ha.
The chemistry of glyphosate changes the second it is sprayed on another surface. It does not leach. It is systemic, not contact. It is transported through the phloem from the leaves to the roots. This is where the damage is done, glyphosate ruins the roots. It takes 3 weeks for complete kill. It takes 3 weeks to be able to plant seeds in that soil.
When used correctly, glyphosate worked well. Too bad now we have to EAT this glyphosate in our food. Corn and other plants have been genetically programmed to be part glyphosate. They can spray glyphosate on crops without hurting the crops. Just the weeds. Now in my opinion that is like going after a couple of bad guys running around in New York City...with a nuclear bomb. Killing everything including the two dumb criminals. Guess it makes more money for the agricultural company.
But using roundup or glyphosate properly once every 5 years? Can be labor saving and judicious. But not be part of our food...
The MSDS sheets, that I had to read every single time I used glyphosate said 3 weeks for planting new plants or seed. If you buy gmo corn, you get to EAT it. A bit different, huh?