I'd really hate to see this much work go into a system that we don't even use, it's just silly. Especially if seiges will have all your farmers from the fields running into your fortress, wouldn't it be better to have large farming layers to help ease the amount of food that you need to stockpile? Especially if we go with making food rot
like in this thread, we can prevent people from just stockpiling their way through seiges, and you would have to feed and house a sudden 300-dwarf influx of refugees in those cases.
This is the closest I'd be willing to go to an "Easy crop"... the infamous "Lumper". You get a few years of easy harvests before the Blight destroys it:
NAME: Waterlump Tuber (The Lumper potato)
notes: This is based upon the Lumper potato strain. For those who aren't that big on American/English/Irish history, the Lumper was the potato strain that fell victim to the Potato Blight that caused the Irish Potato Famine that led to millions of Irishpeople fleeing their native land to places like the United States. (See:
http://www1.american.edu/ted/potato.htm) Unlike most modern potato strains, the lumper was actually not a particularly tasty potato, instead being rather watery. It also grew somewhat slower than modern potatos because, as a early strain of potato that shares more in common with wild potatos than domesticated potatos, and as such, was leafier and spent more time blooming flowers. The key to understanding why this was the crop that caused the famine is that these potatos were much easier to grow than other breeds (soil fertility-wise), and that they had essentially all the nutrients you needed to survive, except for Vitamin A and Calcium, which you could get from milk or cheese, which most poor people relied on for their needs. This is why it became virtually the only crop grown in Ireland, making the lumper such an unprecedentedly easy target for the potato blight, which in turn made a single disease's rapid spread (thanks to the incredible density of the lumper population for that disease to feed upon) capable of starving a million people, and forcing even more people to flee the nation.
PREFSTRING: lumps and knobs
EDIBLE: pest, cooked, grazer
TILE: 232
COLOR: 6 0 0
NUTRIENT_N: 130: 80: -22 (--)
NUTRIENT_P: 90: 50: -5 (-)
NUTRIENT_K: 90: 50: -2 (-)
SOIL_PH: 107: 127: 87: 147: 0
WATER_REQUIREMENT: -80 (--)
BIOMASS: 60: 130: 20: 190: 0
FULL_HARVEST: 33
VALUE: 1 (Actually, since this is a "for sustainance only" crop, I do think perhaps reducing the advantage for having a crappy crop (1 value basically means you get twice as many crops as a 2 value crop), so that we still count a 1 value crop as a 1.5 value crop for the purposes of balancing the equations. This would make this plant only produce a FULL_HARVEST of 22.)
PEST: Waterlump Blight, tuber weevil, wireworm
BIOME: Cold to warm, wet, marginal lands
SEASON: All year, aside from freezing
GROWDUR: 660
SEED TYPE: Destroys crop
Otherwise, why are we bothering? People are trying everything they can to get out of learning a new system, but they're inevitably going to love it when they actually have it.