"A lot of people just want to blame fertilizer, but it's not that simple," David said. "It's fertilizer on intensive corn and soybean agricultural rotations in heavily tile-drained areas. There is also an additional source of nitrogen from sewage effluent from people, although that is a small contribution. It's all of these factors together."
David said that ripping out all of the drainage tiles is not a viable option. "Creating wetlands and reservoirs such as Lake Shelbyville can remove nitrate by holding the water back and letting natural processes remove it, but that's not a solution. It's expensive and we can't flood everyone's land to stop nitrate. That's not going to happen."
"The problem is correctable but will take a concerted effort to change the outcome, with some of the solutions expensive. Installing small wetlands or bioreactors at the end of tile lines that remove nitrates before they flow into the ditch do work, but would cost thousands of dollars per drain. Who's going to pay for that?" David said.
Cover crops can hold the nutrients so they are available in the spring, and are reasonably cheap, David said, but can increase the farmer's risk for the following crop. "So if a farmer plants a cover crop and his neighbor doesn't, he may be at a disadvantage."
David believes that the system can be improved by focusing conservation efforts on the areas of the country that are contributing the most nitrate loss and establish an incentive program for farmers to utilize one or more practices known to reduce nitrate losses from tile lines.
Encouraging farmers to apply the right amount of nitrogen in the spring rather than the fall (or to sidedress), establishing a more complex cropping system which incorporates cover crops or even biofuel crops
|Contact: Debra Levey Larson|
University of Illinois College of Agricultural, Consumer and Environmental Sciences