I seriously doubt it. 70 lbs/week is about the order of magnitude of what one person would eat in a week, but people who eat mostly from their gardens normally are working more on the order of a couple thousand sf/person.

You can jack the numbers up a lot with heavy irrigation/fertilization/perfect climate and lots of experience and work, like in some of the urban homesteading movement. But even the urban homesteaders are serious outliers.