Well... I'll go straight to the point. For how many days does one deer/doe/something like that provide food for one man? And for how many days does one acre of grainfield provide food? Assuming that he eats three meals a day.
The 4th edition Triamore supplement answers your grain question (using an example from the Rhine Tribunal/Lotharingian Tribunal).
But:
Why don't you just make up a number? It doesn't really matter. It is as many days as the storyguide says. Or do you really want to calculate the rate at which it spoils, the amount of salt (or smoking) needed to conserve meat etc? The number of years before a plw must be replaced, the place of whetstones,...
It's just a game.
Jamie Oliver tells us (on one of his intermidable cooking programs http://www.youtube.com/watch?v=qJo8eE21NZg) that a wild boar "easily provides about 40-50 portions". That sounds like a reasonable starting point.
Although if you are going to spread that out over days, you need to worry about preservation --- on the other hand, that is easy with magic.
On the order of 5-10 bushells per acre, depending on agricultural practices/crop/location/etc. Which (I think) translates to around 150-300 litres worth of grain. How much food you get obviously depends on what you do with it.
Based on Whitney, M. (1923) "The Yield of Wheat in England during Seven Centuries", Science, 58(1504):320-324 http://www.jstor.org/stable/1648518
With modern agricultural practices you are looking at 30-100 bushells per acre (depending on where you are, and what precisely you are doing). Magic might help approach modern yields.
HârnMaster is my favouritest game evah!
Beyond even Ars Magica.
Sure you can make up numbers , but getting official confirmation is also helpful.
A quick squiz through Lords of Men reveals , quite frankly , not much.
(the Ease Factor may be too high for my Perception Roll though)
Better stick to healthy natural boar. Artificial magically processed food is likely to cause Warping and a myriad of other health problems, just ask Magus Jamie.
Sorry, couldn't resist. Now if I could just figure out the right ReAn to make a Boar McNugget.
So by that, a one acre winter crop would feed one person for four months, leaving enough grain to sow a spring crop which would in turn feed one person for fourteen months, leaving enough grain to sow the next winter crop... of course that ignores things like rent, tithe, taxes and other such "expenses."
Note that it really makes too much difference, but if a bushel of barley is about 60 pounds, which seems about right --- then using standard ale recipes that would end up at about 140 Litres of ale. Which is a bit over 9 pints a day. Which seems slightly too much.