Your challenge is to have vertical farms in widespread use accounting for 25% of world agricultural production by 2012 with a POD after 1960
ASB.
Just not going to happen for anything except incredibly expensive niche markets. No way would it hit 25% of global food production.
Growing maize in Illinois and Iowa is cheap, cheap, cheap. Growing anything in a greenhouse is far more expensive. Growing stuff in a greenhouse perched on the side of a skyscraper is more expensive than that.
Anything produced in such a facility would be, at a ballpark guess, at least 10x more expensive than field crops, probably rather more. And if that was the price of food, at least a quarter of the world population would starve to death.
Congratulations on your Vlad Tepes award.
How does vertical farming work? Do the plants grow up the wall, or a floor of a skyscraper is dedicated to plants? Wiki didn't explain it enough for me...