I'm not really arguing one way or the other, just trying to understand it all myself.

Corn production has increased, but there has to be the increase in demand.  Without that, more supply can collapse prices.  Ethanol has sopped up a lot of the "over production" for now.  Inputs have also risen, and supply of fertilizers IS in doubt, while that demand is rising, and transport costs are rising.    

Land prices have around 300% in 20 years, while production has increased 30% or so.  Jim Rogers likes ag, and he has been right a lot.  But I think much of his position has to do with currency problems.  He was buying in Brazil a few years ago as I recall ... I'm thinking other countries will be increasing acreage AND yields.

"Iowa State University's annual land price survey showed that in 2005 the average acre of farmland in Iowa was valued at $2,914. That year is a useful benchmark for land values because crop prices had not yet increased. Multiplying the 2005 land value by 2.8 suggests that $5.00 corn and $12.00 soybeans could support average land values in excess of $8,000 per acre."

http://www.card.iastate.edu/iowa_ag_review/winter_08/article1.aspx

I'm not sure if that is just tillable acres, $2914 seems a little low.