The Impact of Tile Drainage on Illinois Agriculture
The State of Illinois has approximately 27 million acres of arable land that is being used for production agriculture. Its agricultural output was approximately $12 billion dollars in 2009-2010. Illinois receives an average of 42 inches of rain in the north to 48 inches of rain in the south. One of the drawbacks of this abundance of rain water is the fact that, without drainage tile's approximately 35 percent of the land would be waterlogged and could not be used for production agriculture.
The U of I has had a significant impact on subsurface drainage technology, which successfully removes water from the soils and directs it to the Mississippi River. Numerous researchers from an entire generation of faculty made major contributions to the technology.
U of I biogeochemist Mark David has been studying nitrate concentrations, which flow in streams to the Gulf of Mexico and lead to seasonal hypoxia, since 1993. A study of the entire Mississippi Basin shows that the most heavily tile-drained areas of North America are also the largest contributing source of nitrate to the Gulf. He, along with scientists from Cornell University, compiled information on each county in the Mississippi River basin including crop acreage and yields, fertilizer inputs, atmospheric deposition, number of people, and livestock to calculate all nitrogen inputs and outputs from 1997 to 2006.
For 153 watersheds in the basin, they also used measurements of nitrate concentration and flow in streams, allowing them to develop a statistical model that explained 83 percent of the variation in springtime nitrate flow in the monitored streams. The greatest nitrate loss to streams corresponded to the highly productive, tile-drained corn belt from southwest Minnesota across Iowa, Illinois, Indiana, and Ohio.