The Jewish Passover seder rite begins with the youngest person, the one least familiar with history, to ask the question, "Why is this night different from all the others?" And so begins the ritual explanation of the history of the Jewish people. Recently, Jason Henderson, a vice president at the Omaha branch of the Kansas City Federal Reserve, posed the economic equivalent question for agriculture: "Why is this farm land boom different from all the others?" He went on to explain the cycle of U.S. agriculture over the past 100 years. The following are some highlights.U.S. agriculture enjoyed two golden eras in the 20th century: the 1910s and the 1970s. Both were led by strong global demand and rising exports; both boosted agricultural com...