It would be extremely difficult to eat that weight of greens in a day. The Mozafar paper is the first paper to report B-12 levels above trace in common plant foods. Accordingly, it would be unwise to assume that a particular soil will supply levels of B-12 to plants that are adequate for human nutritional needs. Mozafar analyzed the plant foods at the location where they were grown, just after harvest. Most consumers buy their foods from markets, and the food has been processed and shipped.
Similar questions apply to types of cooking and food processing.
Legal risks from use of raw manure. Some organic farmers prefer to simply use heavy mulches, with no manure or compost. Some vegan purists reject the use of animal manure. Of course, some might reply that human manure can be used instead. Per Mozafar, sewage sludge is very high in B-12, but organic food advocates oppose the use of sewage sludge because of possible heavy metal contamination.