CHONGWE, Zambia—Benson Chipungu sits in a leather armchair and reaches for the remote to switch off the news. Pieces of fabric hang over the windows, darkening the room against the heat. A gas-powered hand-plough is parked in the corner. On the floors behind his chair, dozens of ears of corn are spread out, a display of the paltry crop the 56-year-old farmer managed to salvage from his rain-starved soil.