Irrigating Through Drainage Pipes Helps Farmers and the Environment

Pumping water back through the same buried pipes used to drain wet fields could increase crop yields significantly while cleaning groundwater and providing a wetland wildlife habitat. Results from three test sites show corn yields went up nine to 60 bushels an acre, and soybean yields went up six to 11 bushels an acre, on average. During the drier growing seasons, corn and soybean yields went up by 48 and 40 percent, respectively.

The test sites have been in operation for six to seven growing seasons in the northwest Ohio counties of Fulton, Defiance and Van Wert.

Agricultural Research Service (ARS) agricultural engineer Barry Allred, ARS soil scientist Norm Fausey and colleagues in Columbus, Ohio, developed the system in collaboration with Ohio State University and the Maumee Valley Resource Conservation and Development Area. Drainage water flows from farm fields through a wetland before being stored in a reservoir, to be used later for irrigation. Many farmers in the upper Midwest have soils so wet they must drain them. Drainage water can pollute surface and groundwaters.

Preliminary results show that water exiting the wetland had, on average, 75 percent less solids--organic matter and sediment, with pesticides possibly attached; 74 percent less nitrate from fertilizer and 63 percent less organic carbon. The wetland trapped the solids and organic carbon, and used the nitrogen to fertilize wetland plants.

Vegetation is thriving in the healthy wetland, providing cover for a variety of wildlife, with up to 19 species of dragonflies--indicators of good water quality--as well as waterfowl, including herons and mallards. Blanchard's cricket frogs thrive at the Defiance County site, although they're on the decline elsewhere in Ohio.

The reuse system keeps the water table constant during the growing season, giving crops all the water they need. The stable water table also limits nitrate-nitrogen from leaching below the reach of corn or soybean roots.

ARS is the U.S. Department of Agriculture's chief scientific research agency.