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"Plug" is the wrong word. Using drainage control boxes on level fields can reduce phosphorus losses by 30% or more, and retain moisture for summer.

February 19, 2015

2 Min Read

A year ago, American Agriculturist reported on research by Cornell University, the Miner Institute and Iowa State University on using drainage control boxes to slow subsurface field drainage. Why would you do that?

The quick answer is: Inline water control boxes can reduce phosphorus loading of draining water by 30% to 50%. Slowing field drainage gives the P more time to bind with soil.


Recent Ohio State University research confirmed the same effect on heavy lake bed soils. That's why farmers in the Western Lake Erie Watershed have installed 430 drainage control structures since 2008 through cost-share programs funded by Ohio and the Campbell Soup Company. Another 131 structures were scheduled for installation by this year.

According to research by Ohio State University and USDA's Agricultural Research Service, drainage control structures can reduce phosphorus losses through subsurface drainage systems by 30% to 40%.

The structures are buried along a drainage line upstream from a tile outlet, explains Ed Crawford, Western Lake Erie Basin Program coordinator. The structure has a track to hold boards to block water flow. Farmers can adjust that flow by adding or removing boards.

How they're used

Typically, farmers install boards to hold water within a foot or two of the surface over the winter after harvest, then remove boards to allow fields to dry in the spring. Of course, the system works best in fields with very little slope.

Won't that block drainage when needed? No, according to Crawford. Once the boards are removed, the system drains just as it would without the structures.

Some farmers use the control structures to hold up the water table across the field during dry periods – after planting. And using them along with cover cropping can reduce P and nitrogen losses even more.

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