ScienceDaily (Sep. 27, 2010) — Tile drainage in the Mississippi Basin is one of the great advances of the 19th and 20th centuries, allowing highly productive agriculture in what was once land too wet to farm. In fact, installation of new tile systems continues every year, because it leads to increased crop yields. But a recent study shows that the most heavily tile-drained areas of North America are also the largest contributing source of nitrate to the Gulf of Mexico, leading to seasonal hypoxia. In the summer of 2010 this dead zone in the Gulf spanned over 7,000 square miles.