Good, leased farmland in the midwest will earn you only around 2 – 3% per year. That’s comparing the annual rent to today’s value. It is not a place to be if you need cash flow.
However, that same farmland has about doubled in value in the last five years. The value of the land depends upon crop price trends and expectations of future crop prices. Corn has about doubled in the past 3 – 4 years. Land prices may be in bubble territory right now. OTOH, the bubble may get bigger–depends upon world crop prices.