Reuters reports that a group of British scientists is recommending an aggressive shift towards the planting of crops not for food, but for a wholesale replacement of petrochemicals. The combination of declining supplies of petroleum (used for much more than fuel) and a still-growing global population means that replacements will be needed soon -- and it's better to start planning now for that event than to wait until oil (effectively) runs out. "At a news conference, [plant reseracher Alison Smith] complained that in the past there had been a lack of coherent thinking, but that was now changing in the face of the looming crisis."
This concept is a fave of Freeman Dyson's. See The Sun, the Genome, and the Internet.
He suggests that a profitable fuel-crop industry could lure people back to small villages.
I'm not sure I see why a profitable fuel-crop industry would be less-readily dominated by big agribusiness than current food-crop industries.
There should also be a corresponding shift in fertilizer technology; much of today's fertilizers are dependent on petrochemicals.
What might be more effective in the interim is approaching effectiveness of current crops; what happens to non-edible by-products of our existing crops? If they're not being used as sileage and green compost...??