Some of you have probably seen this before, but this interactive map shows profitability of farmland in Iowa at the sub-plot level:
http://mesonet.agron.iastate.edu/GIS/apps/profit/
Changes from 2010-2015 are as you'd expect. I believe they normalized everything to a regional rent basis. I think there is still some pretty significant downside for land prices.
I could see it making sense if you were paying cash and already had a good chunk in other traditional investments. I have a small stake in our family farm, and we just farm what we own. Hopefully I won't inherit a big chunk for 25 years or more, but if something happened soon, I'd probably just hang onto it and rent it out, looking at the ultimate long view. Some consistent cash flow to balance out stocks, bonds and other investments.