It was hard to read Scott Reynolds Nelson’s original and intriguing “Oceans of Grain” without thinking of Woody Allen’s “Love and Death”: “The crops, the grains. Fields of rippling wheat. Wheat. All there is in life is wheat.” Karl Marx looked at history and found class. Mr. Nelson tends to find wheat. Thus, in the 19th century, he writes, “the rise of Germany and Italy, the decline of Austria and Turkey, and the European struggle for empire all [had] more to do with the injection of cheap foreign grain into Europe than most historians have recognized.”