We're talking about game balance here, not real world agriculture.
1 space = 1 dwarf = 1 bed = 1 anvil : the dimensions in RL are irrelevant
1 seed = 1 space which yields up to [clustersize] (default 5) plants based on skill
1 plant = 1 Food OR 5 Alcohol
1 Alcohol = 1 Food (*see below*)
Cooking takes 2,3, or 4 stacks of "Food", totals them and makes a stack of Meals
This is a game, so all are abstractions...IE a seed is enough seed or spawn to plant a square, quarry bush leaves are a spice so they are likely a pile of leaves dried and ground up like tea, and one meal is enough to fill a dwarfs tummy.
* on alcohol: this is one of the key exploits used in older versions of DF to multiply food production... grow/gather plants, brew them, cook the booze. Not being able to do this prevents the player from converting booze into food for emergencies. However, even not using this exploit results in a gross overabundance of food in the current version/settings. I have always thought that this should be reduced in usefulness (IE 2 alcohol = 1 food).
Cooking seeds is a lot like cooking alcohol (free food) and works wickedly in conjunction with it. However it is necessary so the player can convert seed stock into food for emergencies. Cooking seeds is also labor intensive compared to cooking with large stack items.
The solution is in these numbers, as well as [GROWDUR]... but the elegant solution changes the minimum number of them.
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In my current fort I am not using the alcohol exploit, and I have tripled the default grow times (900 to 1500) and actually have had a challenge to feed ~120 dwarves. I have made farms on par with my old 2D Forts, totaling about 500 to 600 tiles. Farm/Food staff (post 40 dwarves all browns do it all for me) is around 15%-20% of adult population. From this experiment I am thinking the golden level for me might be default [GROWDUR] x4. I really don't want to mess with stack size [CLUSTERSIZE].
Thus my suggestion is an init option called [plantgrowth:#]. Setting to any integer >0 multiplies the default growth time in the raws by that integer. Resolve the raw files [GROWDUR] so that:
[PLANTGROWTH: 3] x [GROWDUR] = desired default*, so that a player can make it easier (setting it to 1 or 2) or harder (4,5)).
Toady seems to like 5 point scales, and I hope eventually he adds in a 5 point difficulty scale. this would be one of the scaled values therein.
*My recommendation is that desired default should be 3x current value, needing no changes to the raws.
Since all this can be easily done in the raws anyhow, I can just add them to my list of edits to each new version.