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Open tile intakes in Midwest farm fields, “is a practice that should be ended,” says Gary Feyereisen, a USDA drainage expert in Minnesota.
He notes that open tile intakes allow debris, sediment and pollutants, such as nitrogen and phosphorus, to enter surface waterways and block underground pipes.
Most farmers would love to get rid of open surface tile intakes, adds Gary Sands, University of Minnesota Extension ag engineer, “provided they can maintain adequate drainage flow. Alternatives to open inlets, such as inlet risers, rock inlets, or intensive tiling, are “a win-win” for both farmers and the environment.”
Alternatives to inlets
Gary Feyereisen, an agricultural engineer with the USDA-ARS, St. Paul, Minn., is evaluating the water quality effects of French drains in two quarter-section tiled fields in west-central Minnesota. The corn silage fields, which receive annual manure applications, had 48 open surface-tile inlets. All but two were replaced with birdseed sand French drains. “In the three years with the new intakes, average concentrations of sediment in the drainage water have gone down,” Freyereisen reports.
Another inlet alternative is intensive tiling of field potholes, says Gary Sands, University of Minnesota Extension agricultural engineer. Narrowly spaced tile pipes are installed in a shallow grid or coil in the middle of a wet spot. “In new tile systems, contractors have been putting a lot of these in.”
Sands says all these alternative inlets protect water quality better than open inlets, while still providing adequate drainage.
At the University of Illinois, graduate student Stephanie Herbstritt designs and tests filters that can be retrofitted to existing tile inlets or outlets. The goal is to keep out pollutants such as spilled anhydrous ammonia or phosphorus, without lowering drainage capacity.
“There is a need for these innovations,” she says. If regulations on drainage water quality tighten, as they are expected to do, “farmers will need economical solutions.”