We have installed and are testing different systems to modify tile drainage to reduce nitrate losses. The first is water table management, sometimes called controlled drainage (see detailed explanation here from Purdue University and the drainage management team in the Midwest). In this system, a control structure is placed near the end of the tile line at the edge of the field. This structure allows for the water in the field to be backed up to different heights, so that less water flows out. usually the tile is backed up in the fall, and then opened several weeks before field work begins in the spring to allow the water to drain out. We need to know more about how well this system works, and what happens to the water and nitrate backed up into the field. This system allows normal farm practices to occur, and does not interfere at all with what is happening in the field. We still need additional cooperators with fields we can install monitoring equipment so we can see what is happening.
|This shows a field with the control structure, and then with
monitoring wells we will need to monitor what is happening.
Our other method is called a saturated lateral buffer. We will modify the end of a tile line with a tee and direct flow down and along the ditch through a new tile line about 1/4 mile long. The idea is that water will flow out of the lateral tile along the ditch and intro the stream, but as the water does this the nitrate will be removed.
|Here is the tee and the lateral intercepting the main tile line.|
|This is the way the saturated buffer would work.|
Last modified August 10, 2011