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Tile drainage hydrology and phosphorus losses from agricultural runoff

Tile drainage is a key strategy that farmers in the Lake Champlain basin are using to adapt to climate change. But a general understanding of how tile alters field hydrology and transports phosphorus to surface waters is lacking. Joshua Faulkner, a research assistant professor at University of Vermont Extension, recently presented his research on how tile drainage affects field hydrology.

Faulkner highlighted the benefits to drainage for producers, particularly in the Champlain Valley area. But even given the benefits, he said, “There’s trouble in Paradise.” Phosphorus export from tiles has become a major concern in the area, said Faulkner. However, he said as research has deepened, there is some evidence of less surface erosion and reduced runoff.

“Tile drainage was really allowing farmers to adopt many of the best management practices that we’re promoting so fiercely… Things like no-till and cover cropping.”

In their research, Faulkner and team aimed to increase their understanding of the hydrologic flow paths within the soil related to the preferential flow, and now that may function in terms of moving legacy, or long-term, phosphorus that’s in soil, and examining drainage’s efficiency at reducing phosphorus losses.

The research found that phosphorus loads were within typical ranges reported elsewhere, but nitrogen losses were “concerning.” Discharge rates and flow rates were found to drive overall P losses.

“There’s plenty of P there, it’s just whether we’re going to have the flows to move it or not.”

For more on Faulkner’s research, click here.