Originally Posted by Darth_Yuthura
That opens up another front that I'm not inclined to deal with.
There must be a fallow period taken during crop production. At any one time, there are at least 25% of fields not in use to allow the soil to recover after each planting. Crop rotation helps this, but fallow periods have to be taken on a regular basis.
Of all the beef you can produce, you end up feeding the cow twenty times as many calories as you get back from its growth. Instead of growing crops for cattle, you could get twenty times as much nutritional value for human consumption.
I wasn't clear--I was talking about land left fallow because the gov't pays the farmers not to grow crops on them. With modern agriculture techniques, there's no need to leave ground fallow 25% of the time or even rotate crops, though it helps to grow soybeans every few years to fix nitrogen back into the soil. I'm not familiar with the amount of of calories required to grow cattle, but I do know it's not nearly as efficient a use of calories as feeding people the grain directly.
We also have a lot of farmland in the Plains that just isn't in use at all--there aren't any farmers to till the land in some areas.