According to the researchers, the combination of expanded and patterned tile drainage, increased fertilizer use due to more corn production, and more frequent high-intensity precipitation events all contribute to greater losses of nutrients and therefore a large hypoxic zone. This occurs even though nutrient balances (inputs minus outputs) have generally improved across the upper Midwest.
The USDA Natural Resources Conservation Service (NRCS) promotes and provides technical information on a wide array of techniques that can be used to reduce nutrient losses, including fertilizer rate, timing and placement; cover crops; nitrification inhibiters; water table management; tile bioreactors; constructed wetlands; buffer strips; and conversion of row crops to CRP or perennial crops. David said that unfortunately, few of these methods are used on tile-drained fields because they impose substantial costs and/or risks on the producer without increasing crop production.
"For example, end-of-pipe practices such as tile bioreactors or constructed wetlands have substantial construction costs, require land to be taken out of production, and provide no production benefit to the producer," David said.
The researchers noted that important constraints are in the socioeconomic realm and relate to factors influencing adoption of farm conservation practices.
"Producers view themselves as stewards who care for the land, but they need to make a living from it," said rural sociologist Courtney Flint. "Not only can they not see the loss of nutrients, they are disconnected physically from the downstream effects.
Stewardship objectives may be strong, but they can be trumped
|Contact: Debra Levey Larson|
University of Illinois College of Agricultural, Consumer and Environmental Sciences