While researching for a presentation on Agronomy for Landowners in Bloomington this week, I was looking into the geology and soils of McLean County and came across an interesting fact. As a result of the Swamp Act of 1850 the state of Illinois gave almost 24,000 acres to McLean County. This is more than the whole area of a typical township. The young county eventually sold this land and the money was used to found Normal University which became Illinois State University. This reminded me of the stories about how challenging the early pioneers found the prairies of Illinois. It was a soggy dense turf that defied their early efforts to utilize. Then a few days later I had the opportunity to listen to Dr. Richard Cooke, Associate Professor in Agricultural Engineering at the University of Illinois, talk about his research on new soil drainage techniques and technologies.

Since the Drainage Districts were formed, the ditches dug and first clay tile lines installed were installed in the late 1800's there have not been a lot of changes. Some of the equipment has changed such as more horsepower, plastic tile and GPS location/leveling technologies but the basic system design has been pretty much the same.

In the last few years tile drainage has come under fire for contributing to water quality problems. The whole point of tile drainage is to get water off the field faster to allow for better cropping conditions. This rapid removal of water can sometimes carry away nutrients such as nitrogen and phosphorus. High nitrate levels in municipal reservoirs and the Hypoxia zone in the Gulf of Mexico have focused the attention of environmentalists on this issue.

Drainage researchers such as Dr Cooke have been looking at ways to decrease the level of nitrates flowing out of the tile lines. Water sampling of the outflow from tile lines showed that most of the nutrient loss through tile does not occur during the cropping season. One technique that has been successful is the use of control structures that basically make it possible to turn off the tile system for part of the year. The system is not just a valve that you turn on and off. The control structure is more like a manhole sunk down into the ground. In the bottom on one side is the tile flowing in, on the other side is a tile line leading to the outlet. Across the middle is a "dam" that will cause water on the inlet side to back up the water to the height of the dam. The "dam" is adjustable by removing panels that will lower the retention level. Shutting down the flow in the off season has shown significant reductions in nitrate loads.

Bio-reactors are another strategy that is being evaluated to improve water quality. Instead of the control box mentioned above the bioreactors act somewhat like filters that remove the nutrients as the water flows through. In the basic design somewhere near the tile outlet a trench is excavated and the tile line is interrupted. The trench is filled with wood chips that serve as a food and host site for fungi and bacteria that will remove nitrates from water flowing through the trench. The microorganisms need nitrogen from the nitrates to feed on the woodchips and will rapidly grab it from the passing water. The details and designs are a slightly more complicated but that is the basic idea.