Building sustainable gardens-compost crops?

[Tracydr]

I was reading Gaia's Garden. She said that you need about 3-4 times as much lsnd to produce compost crops than actual crops.
Does anybody actually do this?
I've been kicking around getting a few comfrey plants and adding some cardoon in addition to the artichokes. ( I'm kind of afraid the cardoon will be invasive).
I have about 18 acres of trees and vines so maybe that's all I need? Obviously, I'm using all the pine straw, wood chips and leaves that I can physically collect without killing myself. Plus, kitchen scraps and our UCGs. I will see if my new work has an expresso stand that I can get larger quantities.
Once the chickens have a coop, I will have that. Once I get my horses set up, I will have manure, but that will be spread on their pasture.