Charles C. Mann in his book "1491: New Revelations of the Americas Before Columbus" quoted H.G. Wilkes who said that the milpa was "...one of the most successful human invetions ever created." A milpa [maize field] is a small cleared field in which farmers plant a dozen crops at once including maize (corn), squash and beans, tomatoes, sweet potato (depending on local conditions). The beans use the corn as a trelise, fix nitrogen, and add to ecological diversity etc. The results are nutritionally useful and well mixed for humans. Crop rotation with its gap in productivity is rarely needed. For the small community in the new survival mode, a re-discovery and testing of the milpa and a local or community system of milpas for site-specific differences seems like a good idea.