Farmland prices tend to move in phase with crop prices. You could do something with futures or options to gain "exposure".
Check the following links: http://www.great-southern.com.au http://www.thearkfund.com.au I think these are investment funds trading on the ASX (Australian Stock Exchange). I haven't checked, but these might be tradable through Interactive Brokers, they just added ASX.
I suspect local banks reflect the local economy. A small rural bank in Nebraska might relate farm activity there.
I know there is a an ag related etf, but I cant remember what it is ticker is. Farmland seems like a cant miss investment for the next decade.
DBA is ticker of the soft/agri ETF from Powershares/Deutsche Bank. Basically a basket of the AG futures like Wheat, Soybeans etc.