In total global production, corn (maize, Zea mays L.) is the most important food and feed crop. Of the 967 million metric tons produced in 2013, 36.5% were produced in the United States, mostly in the Midwest Corn Belt. The United States is by far the world's largest corn exporter, accounting for 50% of corn exports globally (1, 2). Until recently, breeding and management have allowed farmers to increase the number of plants per acre without loss of yield per plant. On page 516 of this issue, Lobell et al. (3) use a detailed data set for farms across the Corn Belt, to show that increasing yields have been accompanied by rising drought sensitivity, with important implications for future crop yields.
