In a field at the edge of the University of Minnesota’s St. Paul campus, half a dozen students and lab technicians glance up at the darkening afternoon skies. The threatening rain storm might bring relief from the 90-degree August heat, but it won’t help harvest all this wheat. Moving between the short rows, they cut out about 100 spiky heads, put them in a plastic container, and bring them back to a growling Vogel thresher parked at the edge of the plot.