I think it's one of the problem with the lack of clear categories on the forum; I chose the category bio-intensive for my thread, hence the curious question and specification.
Bio-intensive gardening is a method where you also focus on growing healthy soil. The ratio I mentioned, 60/30/10 mean that basically, you try to grow about 60% of carbon-crop, 30% of calories crop, and the rest is plants that are mainly for the minerals or vitamin, or even other uses.
Carbon crops are those that produce some calories, but which produce a lot of bio-mass that when mature, has a lot of carbon that you can use to make compost for the garden. Wheat is one: correct calories but not a lot, and a LOT of biomass. Calories crops are those that gives the most calories, much more that carbon crops, but they give little to no bio-mass. Potatoes gives a lot of calories compared to wheat, grown in the same space (1 square feet of potatoes gives much more calories in less time than one square feet of wheat). But you get a tiny amount of biomass from potatoes. Then, the other crops, most often referred as vitamin/mineral crops, are things like lettuces, cabbages, carrots... you can't survive on eating those only in term of calories (5kg of carrots would gives you decent calories for a human for one day, but I assume you are not a bunny). However they gives precious vitamins and minerals.
There are some green manure used to avoid empty beds, and anything that can be composted for the nitrogen is of course used. But with the ton of carbon you get from the carbon crops, you actually have enough to make very good compost, with good carbon to nitrogen ratio.
Corn and buckwheat completely fulfill the definition of a carbon crop, as well as wheat, rye, amaranth, quinoa... Tomatos are more in the vitamin/minerals (10%), when they die in autumn there's not that much biomass and it's more nitrogen rich than needed for the carbon part of the compost. As for poplar, well I can't plant tree since I'm renting.
EDIT: An example, I think milk thistle might be interesting (it's not mentioned anywhere in the resources I have on bio-intensive; yet its seeds are medicinal as well as its leaves, and produces huge stem which seems good for composting, so it could serve as a carbon crop.
Hopefully it clarify the original post.. If you have more question I can answer them, although I was the one asking questions at first