Our fast-food nation is driven by corn. A couple of recent college graduates decide to learn more about the commodity by growing an acre in Greene, Iowa and shooting a television program. “King Corn” airs this week on public television’s Independent Lens.

The Des Moines Register’s Philip Brasher says the film “is a warm, playful portrayal of Greene as its well its residents and farmers. At one point the woman behind the counter at a local bakery comments on the speed at which farmers can get their planting done with modern machinery: ‘Then they’re back twiddling their thumbs until it’s time to spray something.’”

The film perhaps missed a good bit of the changing economics that the ethanol boom brought about but then again much of the bloom is off that rose.