It all depends on what kind of land you have. On dry rocky ground you would need lots. On good farmland you would need much less. Pay attention to what your family eats in a week and try to think about how you would produce it all X 52. That includes winter and spring when much less food is available.

If you had additional pasture for the fauna, you could meet your family's vegetable needs out of less than one acre. The critical point is to think 'gardening', not 'farming'. To survive on that small an area you would need to concentrate on productive crops like turnips, potatos, carrots and cabbage. Check out "square-foot gardening". (there are 43,560 sf in one acre) Obviously cash is a problem. Also, plan for a significant surplus. Failures and wastage always happen.

Horizontal space required to grow food year round for one person: ~500m2

Assuming you have 'Perfect' soil (no one does) you would be able to raise a variety of vegetables on a small plot for one person - think about 12 feet by 12 feet. (144 square feet) Things like tomatoes require very little area to grow a lot of tomatoes. Corn on the other hand you get on average 1.25 ears per stalk - each stalk requires 8 inches by 8 inches. You figure 36 stalks per person (45 ears of corn) takes up an area 4 feet by 4 feet (16 square feet). Feed corn you need a lot of space to raise a decent amount in order to feed those chickens and goats. Other grains require space as well. Things like wheat, oats, rye, etc take up a lot of room not because they are weak producers but because you never get a 100% harvest, there is always loses, from harvest fall offs to slight damage from pests/disease. The key to small garden sustainability comes in using beds (3 foot wide beds that can be tilled while you stand outside of them) of any length. In/on those beds you use: 1. Intensive Gardening: Since you do not need to drive a tractor through the rows you can reduce the amount of space between plants, this gives you advantages of having denser foliage to prevent weeds from growing. ---> http://www.ces.ncsu.edu/depts/hort/consumer/quickref/vegetable/intensive_veg_gardening.html 2. Successive planting: If you use lots of compost in your beds, you can plant one crop right after the other. EXAMPLE: This year I planted winter squash where the spring carrots and lettuces were - Both of these early crops ended in late May, I started my acorn squash and pumpkin before the lettuce went to seed. My First tomatoes are almost done, I will be pulling them up soon (in 2 weeks) and will plant my fall cool weather crops (carrots, more lettuce, etc). ---> http://en.wikipedia.org/wiki/Succession_planting 3. Companion Planting: The "three sisters" (Corn, Beans and Squash) is an example, where you have crops growing together, each helping the other. ---> http://en.wikipedia.org/wiki/Companion_planting My garden is 20 feet long by 20 feet wide (400 square feet) Not even 0.01 acre. It consists of 8 - 9 foot X 3 foot beds set every 18-24 inches apart with a single 30 inch wide bed 20 feet long (against the fence). Figure 266 square feet of bed area. The pathways between beds I use sheet composting http://en.wikipedia.org/wiki/Sheet_composting I lay in grass clippings and autumn leaves and cover with straw. At the end of the growing year I rake away the top layer and have half composted to fully composted material, that stuff I rake into the beds. This has removed the need for excessively large compost bins, reducing the hauling of wheel barrel full of compost, and keeps weeds down between the beds. In that area I have raised: Cool weather (spring and fall): 8 Broccoli (I'm the only one who eats it) 3 Varieties of lettuce (36 x 36 per each) 1 patch spinach (3'x 4') 3 Varieties of carrot (again 3'x3') 1 carrot 'patch) 3 x 3 Radishes (36" x 18") 8 sweet peas. 1 patch Turnip (3'x4') Warm Weather: Beans (Green and Wax) 4 each Tomatoes (3 varieties) 8 Bell Peppers 6 Zucchini (bushing variety) 2 (you only need 2) Jack Olantern Pumpkin (2) Field Pumpkin (Pie pumpkin) 2 Potatoes - Red and "brown" 3 segments 3' x 6' different times to produce year round spuds. 6 Lima bean plants 4 Pinto bean plants 1 Egg plant (that is all I need thanks). 4 Cucumber plants 2 Water melon vines 2 Cantaloupe 3 segments 12 x 36 of white onion 2 Segments 12 x 36 of red onion. 4 Sweet potato vines I also have my perennial and annual herbs in this area. I raised 6 segments of sweet corn, each consisting of 12 stalks, each segment planted a week apart, giving us a longer harvest of ear corn. From this we have eaten fresh, plus I have laid up a lot of beans, tomatoes, zucchini, spinach, peas (Frozen and canned) I have dried garlic, herbs, bell pepper, tomato, onion, carrot flakes... We are still eating root crops (carrot, potato, turnip) that is stored under the house --> It's not a true cellar, a crawl space that I have dug a little deeper (18 inches deeper making it 4 1/2 feet from "ceiling" to floor) and lined with black plastic with a 2x6 boarder to prevent rain water from flowing in. From Grocers we buy our canned corn. During the summer season when corn is in season I buy a few bushels of fresh from the local farms and/or the farmers market. I have found it cheaper and easier than trying to raise enough to can and freeze for our needs. BTW this is all for two people and two dogs. I gave away about a bushel of Tomato, a bushel of zucchini and a half bushel of yellow summer squash. 6 years ago I pulled out the Virgina Creeper and made the Crop Circle. I dug it all out by hand (to remove the roots of that hardy vining weed) and ended up with a circle 14 feet in diameter (7 feet radius). I planted corn in a circle with 3 hills of pumpkin all surrounded by a ring of marigolds. The soil was not amended with compost - I got about 1/3 of the corn producing decent ears, enough pumpkin to make a few dollars and marigolds galore. I mention here because you have critters and may be interested in raising corn yourself. Other than wanting a crop circle of my very own - LOL - I also had to take into account the sprinkler I used (one of those reciprocating yard bird types that water in a 15' to 20' circle) I planted the rows in circles (using a line with a stake at the center, using a hoe handle to draw each circle). I would assume had I amended the soil with composted chicken manure and other composted material my paltry harvest of corn would have been greater. Mind year we have nearly year round growing, with a short 'cold snap' between November and January (Central Valley California) with a threat of light frosts. Chickens and goats need feed (hay and corn) and bedding (straw). I have no idea what a chibis is. If you are raising that yourself you can figure that you will need up to an acre of pasture with some of that set aside for raising grass as hay and straw. An acre of corn will yield a lot of corn: 1 acre yields: 180 bushels 1 bushel = 70 lbs ears 1 bushel = 56 lbs shelled There are between 40 and 60 ears per bushel. Thus 12,600 lbs of ear corn or 10,080 lbs of shelled corn or on average 9,000 ears of corn. This is assuming you use chemical fertilizes, crop rotate, use herbicides and pesticides to get the most bang for your buck. If you are going organic figure a loss of as much as 25% of that. Of course you most likely do not need that much corn. BTW an acre of land is (perfectly squared) 208 feet by 208 feet. So that may help with your calculations.