I like this idea. It allows for the magical feasts of stories without allowing magic to replace agriculture for whole regions.
Three warping points sounds like a lot for me though. I might prefer it to work something like high magical auras, only affecting those who aren't already aligned with the realm.
It is a lot, yes, but I want it to be - eating Magical food is an emergency measure, not a cost-saving one. In particular, it's actually worse for Magi than Grogs. IMS, the grogs were kept happy by liberally supplementing their diet with created beer and were, after a few years (of one point a season - it wasn't their main food supply), some of them were starting to get a little weird.
True, but in both cases you can argue that you're eating nothing. I tend to think of it like a cooking fire - you can magically create wood and then apply mundane flame to get a campfire. Once the spell ends, does the cooked food become raw once more, and instantly cold? That happening offends my sense of, well, sense and so I apply the same approach to the food issue.
But it's not like a magical fire cooking. It's like healing a wound magically. When the spell duration ends the wound returns, because it was not healing, because it was not there.
If you ate magical food for nourisment then ate tons of normal food for pleasure. since you were already nourished the mundane carbs and such would get stored as fat rather than being retroactivly matabolised when the magical nourishment went away. (That is of course a very modern i.e. anachronistic explanation)
If you are eating food sustained by magic (that is has a running duration), then you are being sustained by magic yourself. So when the magic ends - so do you...
I could be wrong, especially as I don't have the book, but I read this, not as "food conjured by faerie powers", but more like "strange food grown in a faerie aura". The Faerie analog to normal food, if you want. Like in these stories where you can't eat faerie food.
Well you could interpret it that way but then it's an irrelevent reference that implies you should get warping from eating food grown on covenant grounds.
But really that wouldn't suprise me if the grown food in an aura was the case in that anecdote.
I havent noticed anyone reporting the use of day-lasting spells to accelerate growth of plants, which upon end of duration remains as they are at said end.
This is way more unbalancing than just creating food, let me explain :
Day 1 : I accelerate the growth of my fields to full maturity within Sun duration, target Boundary (ie. the field).
Day 2 : my people harvests the grain, and if manpower allows, sows the seeds back.
Day 3 : I accelerate the growth of my field to full maturity within Sun duration, target Boundary (and i did not use copy and paste)
Day 4 : my people harvests again, and sow again.
3 sowings and 3 harvests per week, if manpower allows, of course, but that can also be solved by a spell if it is required. And of course, being fine christians, we dont work on Sundays.
End and final result : excessive production of food, all valid as per RAW. Economy collapses due to excessive supply of food on the market.
Thus, seen like that, the non-permanent nature of food created with Vis becomes a moot point, as per RAW, unlimited food is perfectly possible and fine, without using any Vis.
Any thoughts ? (and draughts are not an issue anyway as we accelerate growths of plants)
François
How are you casting a ritual every other day without Vis by RAW? Well, if it's a level 20 ritual cast by a Mercurian Magus with Imbued with the Spirit of Herbam and the Spell Mastery option Stalwart Casting, then OK, it's doable. However, I think once you've tossed Day and Boundary in there you are well past level 20 with this effect. Also, generally speaking, Boundary won't cover your "fields" (note the plural) unless you make it larger. That's not to say it can't be done, but it needs to be done differently, such as with a Circle target and many castings (probably risking botches a lot more than the rituals would).
Also, I'm not sure I remember the effect properly, but I would think there would be problems with the fields not laying fallow. You'd probably end up maturing terrible crops with little nutritional value after a few castings regardless of the method. But I my memory may be off.
Chris
That would work except the Rego Herbam rules specify that the plants don't produce fruit.
The lumber industry does great from this tho.
I don't think the "mature quickly" spells need vis. This is their strong point and Fuldry's way of doing is perfectly valid.
And, indeed, economy breaking. But when magic is involved, economy is easily broken.
page 78 , ArM05
Which can be actually quite useful , having no seeds , e.g. olives for making oil.
Ah i knew there was somthing wierd about it. But at least it is more complex than simply going "poof, let them eat cake". And you would have to have a reasonable supply of mundane plants to get seeds to plant.
Also seedless freaking cotton=win
That's a very odd rule and seems counterintuitive. Rego controls natural processes such as plant maturation. You'd expect a natural result and instead get a very unnatural fruit.
I swear, one of the authors really seems to be going out of his way to make this whole magical food thing not work.
He is specifically using a ritual that requires Vis. Note the Boundary target. This is why I said it could be adjusted using Circle or something similar. So, no, his way is not perfectly valid.
Chris
Don't forget , the Ars Magica paradigm is Aristotelian physics , not Newtonian.
Though , if Art and Academe covers this , i can't recall where.
(page 78 , ArM05)
You want to do this using the CrHe guideslines, correct?
The only limitation I see is that Target: Boundary makes it a ritual spell.
After calculation, you'd need a ritual, agreed (and for 2 reasons, 1 level, 2 boundary requires ritual as per spell guidelines):
Base 15, bring a plant to maturity, +2 duration Sun, +4 target boundary, +1 target Touch= level 50. I don't think there is a way to bring it to level 45.
(well depending on your area, Vis might not be a big issue).
Objective is not Fields, but a single field, which might be quite big as per boundary target, which is at most, 100 paces diameter.
And as I am not "creating" plants, but accelerating growth, seeds will be there, ready to be sown again next day. Now back to drawing board to remove that annoying boundary requires ritual 
OK, 3rd Edit, revised version :
Base 15, bring a plant to maturity, +2 duration Sun, +2 target room, +1 target Touch= level 35.
Requires seeds to be sown in square rooms 20 feet per side, which IMO I would allow to be acceptable without ceilings... As the target guidelines says ceiling height does not matter...
Level 35, no ritual involved at all, can be cast at will quite easily if you can reach the required casting total, thus allowing you to cast it like 10 to 15 times at dawn or dusk, and have fully grown plants at end of duration.
Peasants in the area will think that the pact is rather weird to put walls within the fields, but this does work. As it is tedious, I would think a magus would grow rather quickly bored of doing this every other day, but this works.
4th edit : would multiple floors make multiple rooms ? Depending on how you build your room, like a square tower built with a CrTe ritual, a single square room might contain multiple floors all within the room boundry, like, the gardens of babylon, kind of. (as I see it : square pillars holding floors, like 2 meters apart, 4 meters to a side, within a square room 6 meters to a side, the room between the floors and the external wall to allow people that recolts the fruits to actually throw them off the sides, and people down to sweep them to storage.
Now just make a magic item that lets pesants do that and it may get done. No self respecting magi is going to spend all his time tending fields.
I don't hold with economy worship, myself. Especially not in a game. So this is perfectly fine. Even desirable.