Kenny McBride wrote:After, let's say five years, what kind of per acre yields might you expect from a well-planted site? Are we talking enough to feed one person? Ten people? Twenty?
We have a productive farm based on a lot of permaculture methods. In our case a lot of what we produce is coming from livestock because that is what we do and that is what our land is good at - we're in the mountains. Ours is a swiftly sloping farm. Our land is very good at producing pasture which our pigs and chickens turn into eggs, lamb and pork. The people we feed (e.g., our family, our customers) eat a lot of meat and there is also a huge number of berries and other fruit, wild greens and cultivated roots, greens and other veggies. Field crops like wheat and such that require flat lands we're not such a good place for - thus trade and commerce.
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Real life example:
I farm. We sell some to individuals but mostly we supply local stores and restaurants so I don't really know how many people eat our farm's products.
I can easily and sustainably do 10 pigs per acre - proven for a long time. Almost all their food can come from our farm, all of it with a little more patience (e.g., they take nine months to get to market weight rather than six). I think with the past decade of experience at this I can boost that to 20 per acre if I wanted. Along side them per acre we also have a few dozen chickens, couple of sheep, some ducks and geese in our case. This is easily sustainable. They grow more slowly since no corn/soy grain commercial feed but it is doable all from our land.
10 pigs/acre/yr
x 5 acres
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50 pigs/year (add the other animals but I'm ignoring them) (In reality we have more than 5 acres and more than 400 pigs)
A pig is about 200 lbs of food after slaughter (eat everything on the hanging carcass - most of that is edible - add the chickens to make up for any inedible parts you don't like but don't be picky, you're doing permaculture, right!?)
That's 200 x 50 = 10,000 lbs of pork a year (Hanging Weight)
A person needs about two to three pounds of pork a day (that's a need, not an option.

Everyone needs pork, especially bacon.

) which is about 912 lbs/yr (major paleo diet!). This could be easily half that if you're eating berries and other things so the number below for people per acre could be higher by that same ratio.
Thus that's about 10 people that can be supported on five acres getting ALL their diet from those five acres which is about two people per acre on a very rich meat diet. (delicious)
If you also ate some berries, veggies, etc you would be able to take advantage of the incredibly rich growing conditions created by those livestock and diversify your diet supporting probably two to four times that number of people. I can grow quite a bit of other stuff on those same five acres - I just don't sell any of it.
If you are willing to farm more intensely than I am then it is probably better again.
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Based on my experience it is doable and is sustainable but this would take more intensive farming than I want to do. It would look more like something out of the Asian or Andes mountains than we do now but then again, we too terrace much like they do but I don't want to do it that intensely.
One concern I have is that there is a point where you are competing with the wildlife for the food. By our creating fields we have increased the biodiversity and amount of food and wildlife on our land. At the rate we take from our land the amount we have increased is more than what we take. However if we went to the theoretical maximum the wildlife would suffer for it. Correct with that in mind.
Farming is a nutrient export business and you have to be careful not to send out too much. Having slaughter and butchering on-farm increases the carrying capacity of the land because the offal, the guts, gets returned to the
compost and the land. Legumes like alfalfa, trefoil, clovers all suck nitrogen out of the air fertilizing the soil. Considering changing society so they don't throw heavy metals and pharmaceuticals down the toilet and everyone saves their valuable poop and pee to return to the land - that would help.
Note that I have a lot more than five years invested building our farm infrastructure and many years of experience so my numbers might not be representative of where you could get to in five years but they are where you could get to eventually - maybe you can do better. However I doubt that someone starting from ground zero of knowledge would get there in five years. It takes a lot of time to learn, build infrastructure, get permaculture plantings going, perennials, etc. What we need is for it to become the cultural norm so you learn from birth.