January 26, 2014

Agricultural tile drains -- beneficial for crops or costly to environment?

If you walk along a stream in an agricultural area it is not unusual to encounter pipes discharging water directly into it.

These pipes are attached to drain systems that farmers use to lower the water table for their fields. The practice, termed tile draining, can dramatically improve crop yields on marginal fields, but its environmental impact is unclear.

Fields have been tiled for millennia. The Roman statesman Cato was the first to describe the practice around ancient Rome. He noted the use of brush, straw, poles, stones, boards and tile to improve drainage in fields. It was popularized in the United States in the mid-1800s by John Johnston, a Scottish immigrant who used tile drainage to improve the poor soils of his farm in upstate New York. Today perforated plastic piping has largely replaced actual ceramic tiles in fields.

Pipes are placed in trenches 2 to 4 feet below the surface. Groundwater flows through the pipes rather than the soil, because the pipes offer a pathway of least resistance. As a result, the groundwater table is lowered to the depth of the pipes thus ensuring that a crop’s roots won’t become water logged, and that fields drain earlier in the spring. The pipes are usually oriented to discharge into a nearby stream, though in some cases, the discharge may just be to an area lower in elevation.

Initially, research on tile drainage in the Champlain Basin focused on economic issues, but that has changed. At first, researchers sought means to improve the efficiency of tiling and maximize yields while minimizing the cost of installation. Tiling was seen as a way to increase the social and economic well-being of the region. Today, that has shifted and more researchers are exploring the effects of tiling on the ecosystem and nutrient loading to our waters.

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