If you purchase farmland, at least in the upper Midwest, you'll earn a 5-8% yearly dividend by renting it out, and there is little to no maintenance that you need to do yourself (depending on your rental contract).
This is an unlikely avenue for me given my geography, but out of curiosity and for the purposes of the discussion, are you basing the return on equity invested or on total value of the land?
Any suggestions for more info on this? Books, how-to's, longer "this is what I did stories"? I could just start calling rural real estate lawyers and asking nosy questions, but maybe there's a quicker way. :)
I fell into it when my wife and I had the opportunity to buy a parcel of her grandmother's farm that was already being rented, so I don't have much more information than that.