While it totally depends on the scale of what you're growing, one acre is plenty of room for a variety of produce, a few animals, a greenhouse, and many other forms of production. An acre being utilized at its most efficient can produce tens of thousands of pounds of crops a year. Of course, subsistence agriculture means you're primarily planning to feed you and your family. 40,000 lbs of potatoes may be a little overwhelming, and generally not useful. Instead, smaller areas for planning simply mean that your space needs to be used effciently. There's lots of ways to do this, compacting and shrinking the amount of room you need to function and grow can maximize what you're able to produce.
Vertical agriculture involves taking advantage of the upwards space we typically forget to utilize. Plants can be stacked or suspended one above the other. When watering, pouring starts at the top, and gravity pulls the rest of the moisture downwards towards the rest of plants. Shelves, hanging baskets, or other kinds of vertical organization are popular DIY projects, and easy to find across the internet.
