OK, i read through a lot of this, but i missed other parts, so point out where i am duplicating effort.
i am going to try and address all the issues i have seen (it appears to me that most of them repeat) in one comprehensive farming post. we will see how well it works.
here are the issues and resolutions as i would like to see it.
assumption: dorfs only eat 8 times a year and drink 18 times a year. any farming considerations will have to take this into account. toady has already stated that he does not wish to increase this, so end numbers will have to reflect this.
1. a dorf requires roughly 10 squares of land per harvest to be feed and boozed. this takes into account crop failures and food loss. (so only 8 tiles if there is no loss)
2. each square of "normal" food takes 1 seed and produces 2 "consumables." this gives you one to eat and one for booze. the consumable is not stacked, but are separate items. this will not be a problem after hauling is revamped, and makes things simpler and more consistent down the production chain. fertilization can increase the yield by 1 consumable per tile, reducing your land use by 1/3rd
a. normal crops take 2 or more seasons to grow, and above ground crops can only be grown in spring and summer, requiring 2 seasons to be fallow. below ground crops are year round, usually taking two seasons or more to grow, but require fertilization with each planting. (this will also benefit from more types of fertilization, but it keeps things balanced, since UG farming will likely require half the space to grow.) with the new partial use system one unit of fertilizer could fertilize 5 plots, or we could just up the output of fertilizer per reaction.
b. to keep farmers busy watering and tending fields will be required, though watering can be automated/eliminated with good farm construction (see suggestions for near water farms and flooding).
c. certain high value crops should implement the space requirement (cardinal point and 9 square, depending on value), as i think it is a good mechanic that should not go to waste. it just means you need more space to grow it.
d. a farmers skill determines failure rate of crops. a regular no prefix farmer should have a failure rate of 2 in 10. a farmer with no skill should have a failure rate of 6 or 7 in 10 (so unsustainable, and thus a cost to train them). legendaries should of course not have a failure (barring outside circumstances of course). as farmers skill up they also work faster, but the speed difference between not farmer and legendary should only be a max of 25%. since the production is not determined on the speed of the farmers anyway this will just mean that a legendary will have more time to work on other stuff, or you will need 25% fewer field laborers if they are all legendary (not unlikely). harvesting and watering are also "hauling" jobs and not give farming xp, only planting and tending do.
3. one consumable makes 2 booze. on booze job requires 5 consumables, for a total of 20 booze per barrel, every time.
4. food processing will always yield a "seed unit" and a processed food unit ("ingredient"). seed units can also be cooked, but require 5 to 20 individual seeds units to make 1 "ingredient" and may require processing before cooking. booze will require 2 units to make one ingredient.
5. cooking food will require 2 to 4 ingredients, and will always yield a stack of 2 to 4. (meat will also have to abide by the no stack rules as well) this will also help mitigate the "one job makes a huge stack of super expensive food" issue).
6. animals will need to be fed, but that should only indirectly consume from the farmland, and should not be fed directly from your crops unless their is not other source of food for them (see the many suggestions on grazing and chunk usage). some indirect sources could be stubble (which should also be harvestable and used as fertilizer) and rotted food.
and now to head off some of the debate (i may be duplicating effort hear. in that case just take this as a long winded "i concur").
i do not think 10 tiles per dorf is unreasonable. the starting 7 will need a 10x7 plot to grow food on. that can easily be done with one designation. a 20x100 plot is not actually a great deal of in game space, and can wind up being only 20 individual fields. this issue can be mitigated even further if you allow the field to be expanded beyond 10x10. people who complain about this just don't want it to mess up their current fort designs. i say there is going to be a lot more coming that will cause a lot more problems with that later on. burrows will probably have a greater impact on fort design than this. you can fit farmland for 230 dorfs on one 48x48 embark tile.
if anyone has objection to the "no stack" issue, it will be entirely moot once the hauling is updated. plus it vastly simplifies food handling.
this suggestion also does not address other types of crops such as orchards, wall climbing vines etc. eventually the plan is to get multi z level trees/plants and orchards and vineyards will have to be handled and balanced with that in mind. this is for "farmplot" only crops.
i am sure this as all been talked about before and i just glossed it over, but i wanted to get my thoughts on the matter spelled out clearly.