Hello Spring and good that you like the book.
Allotments of 16 rods or about a tenth of an acre were intended to give families the chance to grow most of their vegetables. It depends how many veg you eat, the season, how productive you can make your soil and whether you grow space hungry veg like cauliflower. Growing intensively and double cropping means smaller areas do well, I don’t want to put a precise figure on it for all these reasons.