U of I Researchers cooperate with local farmers on new device to improve water quality

U of I Researchers cooperate with local farmers on new device to improve water quality

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You’ve probably heard of the phenomenon known as the “Dead Zone” that occurs each summer in the Gulf of Mexico. It forms when the concentration of dissolved oxygen in a defined area falls below the threshold that will support animal life. Highly mobile organisms, such as fish, can flee as it develops, but others, including mussels and crabs, die as it overtakes them.

In August, scientists with the group that has monitored the Dead Zone since 1985 found that this year it covered an area of almost 6,800 square miles. That’s just smaller than all of Lake Ontario, and about average for recent years.

The Dead Zone is caused by an explosive summertime growth and decay of algae, which is fueled by nutrients that enter the Gulf by way of the Mississippi River. Those nutrients, primarily nitrate and phosphorous, can be traced back to a number of sources, including urban runoff and treated wastewater. But agriculture in the Midwest is far and away the largest contributor of nitrate, and tile-drained agriculture of the sort that dominates east central Illinois leaks the largest amounts.

Over the past three years, a team of researchers from the U of I led by professor Mark David has been working with local farmers to address this problem, in cooperation with a number of other agencies, including American Farmland Trust, the Champaign County Soil and Water Conservation District and the USDA Natural Resources Conservation Service.

One part of their effort has been an experiment to test whether managing the flow of drainage water from fields can reduce nitrate loss. A modern tile drain is really just a buried plastic pipe with slits in it that speeds the movement of water from the soil into an adjacent waterway. Without such drainage, many fields in Illinois would remain too saturated to work in the spring and early summer. It’s generally not important to farming, however, that fields be drained year round.

The researchers have been testing a simple structure that allows a farmer to block the flow of water at the discharge end of the tile during the winter and early spring. They have found that the amount of water coming out of these tiles once they were opened was reduced by 50–75 percent, with a corresponding reduction in the amount of nitrate discharged.

What makes this method of reducing nitrate loss exciting is that the mechanism is simple and relatively cheap. It’s essentially a small, belowground reservoir with a frame where boards can be stacked to back up water to a specific level. It occupies only a very small space and doesn’t interfere with farming in any other way.

There are aspects of the system that bear further investigation—chief among them, the question of what happens to the water and nitrates that do not flow out through the tile. The researchers don’t yet know for sure whether that all just winds up in the waterway via some other route, but they’re conducting further tests to see. If this method of controlling nitrate loss proves to be as effective as it seems, it would add to a growing list of practices that have been shown to work under a variety of conditions.

What do farmers think about when deciding whether to adopt these practices? That’s another key question being investigated as part of the current project. Next week I’ll check in with U of I professor Courtney Flint to report on what she has found so far.