Last year, Japan was flooding its rice market with emergency stockpiles in a bid to mollify voters angered by the soaring price of its staple grain. Now, it has the opposite problem: a glut. That is welcome news for shoppers, but the whiplash is hurting people like Hiroshi Asano, 59, who farms a relatively large 38 hectares (93 acres) of rice fields in Chiba, close to Tokyo. He expects to make a loss this year, and he is worried smaller-scale farmers would not be able to survive. “I’ve been...