Well towns start off as exceedingly small little farming communities in essence. If you have a farm in a new city it takes up half that cities available land and is likely the reason the little community started up there in the first place. So the farm been the life blood of the town would be the centralised landmark. It's not untill a city grows signifigantly that the concept of centralised land value would be worth conisdering... And by then the farms been in the center of town since time began. A protected historic landmark most likely.

If creating fertile land through magic or other means becomes and option at a later point in the development of the game larger cities which have farmland created for them will have to have them placed on the outskirts of town by virtue of that been the only space avaialble at that point anyway, so I don't realy think this is going to be a huge issue.

Ok, I can see what your both saying, but, I live in a rural farm based area.  The amount of land dedicated to farming, and ranching, is huge.  Trying to contain the land required to feed even a moderate sized settlement IN the settlement would make the settlement very large and harder to defend.  That's why medieval castles and towns didn't wall in all the farm land around them, it's just too much.  And, modern farming techniques and scientific breakthroughs have made modern farmers much more productive than their historical counterparts.  I read something years ago, that medieval farmers thought a good harvest was a 3 to 1 yield.  Modern farming gets better than 50 to 1 yields.  These numbers are ballpark estimates, but they should give you an idea of the efficiency of early farming.  Ok, early on the world is a wasteland and settlements are around the few fertile lands, like oasis in a desert.  But as the channelers get going and the land is revitilized the should be a spreading network of farms around these communities.  That's all I'm trying to say.

Reality doesn't need to be plausible, fiction does.