Organic agriculture has much lower yields than conventional agriculture for most crops [1]. I believe permaculture is more restrictive than US-Organic. It would take some big changes in our diet to absorb such a loss in productivity.
There's also the little pickle that manure from an industrial feedlot is considered an organic fertilizer.
(I'm not suggesting it's directly a problem, the issue is that it's real hard to figure out the nitrogen budget society ends up with if all synthetic fertilizers go away)
During the economic sanctions, Cuba was forced to stop using synethetic fertilizers, pesticides, and even tractors. They could not import enough to be able use those at scale. The people there had to adapt and work out how to live.
(I'm not suggesting it's directly a problem, the issue is that it's real hard to figure out the nitrogen budget society ends up with if all synthetic fertilizers go away)