(source: John Damuth, Nature 290, 699-700 (23 April 1981))
You can put your body mass on trend line (assuming your weight 60 kg, on x axis you'll have ~4.8), find log(D), raise 10 to that number, and you will have area needed to that number of "herbivore people" to meet their feeding requirements (number will be few "persons" per km2). For hunters-gatherers (humans) it can be from few to several km2 per person Just for comparison, nowadays we have less than 2 acres of agricultural land per person. You get my point?
BTW, what vegetables/fruits Suomies had, say, 500 years ago (besides berries)?
And your experience about multiculture farming.. if you fail, does it mean you fail or that the system fails?
You said it yourself, non-organic, so why come tell us organic is a failure? Did you actually pick up any book about permaculture, read it and tried it? Mulch and poop, yes, and if you know something about multiculture farming you probably know the indicators of healthy soil. Can't blame you for not knowing about winter-warm greenhouses because they seem to be a rather new thing, but working. They would had helped you a lot. You know I'm coming from norther than you, snow's here longer than in your place, and people here have those kind of greenhouses too, a friend of mine knows one guy in my hometown 200km north from capital who grows pear trees inside those all-year greenhouses, says he makes an ok profit.
From what you say, it sounds like you picked the plants well, and didn't make the obvious mistakes but weeds management was your problem too. The most common thing, and it's hard when you have weeds that spread through airborne seeds. Fencing your lot with a more deep-grounded fence helps only with those that spread through their root system like bamboo, doesn't cut it in most cases in our area. It can help tho, because some of the seeds are bound to land on the fence. I'd need to read the book again to find what they suggested to this, something more sensible than this. One thing would be to plant a plant that kills the weeds in key positions, maybe tomato or pepper... peanuts dont usually tolerate our winter but one guy did have a whole lot of them in England. They'd manage in a greenhouse, not that it helps you much now, and their roots might kill most weeds.
Did you try to find any permanent solution to your weed problem? Did you test any other solutions to it than pesticides and pulling them up?
First of all, I didn't cared about gardening then (I was just a wetback, mule), nor do I care now (we sold that property 6 years ago). My grandfather was mastermind behind this, and he wasn't stranger to agriculture: his family owned ~30 hectares farm before WWII, he attended agricultural school, and he was gardening in place I'm talking about since 1953 (after long free trip to Siberia). More to that, he was subscribing pop-agricultural journals (were few of them in USSR).
Second, I must apologies for posting incorrect number - 0.5 acres. It was less than 0.15 acres (~6 ares). Retrieved wrong conversion multiplier from memory. Sorry.
Third, we had no problems with weed, cause grandfather was spending his whole days in the garden (when not fishing), so any weed was eliminated just after it showed his "head" to the sun. My post about beet weeding must have misled you, but that was very different story.
Fourth, we had two greenhouses - one for tomatoes/paprika, and one for cucumbers. Heating/illuminating those greenhouses in winter would have been complete waste of energy (greenhouses were wooden frame covered with polythene wrap... Once we built greenhouse using glass... Well, it lasted less than week before hooligans smashed almost all glass).
Fifth, grandfather was applying fertilizers conservatively, i.e. only when needed (well, "needed" just by appearance of the plants) and in lower quantities. Neighbor, who was growing only tomatoes for selling, was having bigger tomatoes and more per plant than we (same variety, got seeds from him, Oxheart in translation). Guess what, he was using more (in quantity) fertilizers.
Anyway, all that holistic, nature caring farming is not bad, but requires lots of hand work, and its not the solution for feeding growing population, Intensive farming (with long lasting consequences) ain't solution either. I'd say, let organic farmers to use synthetic fertilizers, or, for that matter, herbicides/pesticides when plants needed, just without overusing.