A lot seems to depend on how government deals with our massive debt.  If inflating the dollar is the way out (as it appears now), land should be good to go to $10K (or whatever), assuming taxes don't get out of control.

But if drastic cuts in entitlements and subsidies happen, and/or the economy struggles for a decade, and agriculture develops in other countries ... then it all could change. 

And we could lose the ethanol support if energy moves in another direction ... like more US drilling or nuclear, nat gas or coal, or even sugar cane.  Political blogs I read, conservatives and liberals both seem mostly against ethanol support.  Without ethanol subsidy, do we go back to $2.25 corn?

If we lose all subsidies, and taxes go up, and investors have to bail to cover other losses (stock market or whatever) ... it certainly seems feasible land values could at least retrace much of the recent bull run.

"At $2,350 per acre, average farmland values are more than 20 percent higher than their historic peak of $1,940 recorded in 1981."

http://www.fdic.gov/bank/analytical/quarterly/2008_vol2_4/farmland.html

 I think it has continued to spike for two more years since this chart, probably because our government is out of control and so many are trying to get out of the dollar.  A regression to the mean might cut values in half.  Political upheaval might break even the lower end of the uptrend.  It sure seems possible that things are getting a little frothy at the top ... though "they" were saying that a few years ago.