A pioneering study of U.S nitrogen use in agriculture has identified 20 places across the country where farmers, government, and citizens should target nitrogen reduction efforts. The 20 nitrogen ‘hotspots of opportunity’– which appear on a striking map — represent a whopping 63% of the total surplus nitrogen balance in U.S. croplands, but only 24% of U.S. cropland area. Nitrogen inputs are so high in these areas that farmers can most likely reduce nitrogen use without hurting crop yields.