After a half-century of dominance, the U.S. is losing its edge in agriculture to a booming, high-tech Latin American powerhouse. Its secret weapon? Soyabeans. A big swath of soya-producing lands that stretch between the Andes and the Atlantic forest and from northern Argentina to the southern flanks of the Amazon basin. Soylandia, as this immense region might be called, is almost entirely unknown to Americans and indeed much of the Western World. But it may well be the future of one of the world’s most…