You can maybe keep a small family alive on an acre, but not really feed long term. With such little space you need to dedicate nearly the entire plot to high caloric crops such as corn.
Each year, I grow an increasing amount of my food from less than an acre. Corn is not an efficient way to get calories in an organic system, it requires too much nitrogen. As others have mentioned, potatoes are much better. And beans/peas, which require achieve their nitrogen requirements via bacterial symbosis. If you really want to go efficient, grow Azolla. I once calculated that a person in a temperate climate could produce most of their nutritional requireents with a plot roughly 25 square meters. Azolla doubles in mass every 2-3 days in ideal conditions and draws everything but trace minerals from the atmosphere.
