The Vermont Agency of Agriculture is set to consider new rules for how farms drain water off their fields using subsurface tile systems. Environmental groups are concerned that these systems could increase nutrient and sediment pollution in Lake Champlain. They say no new tile drainage should be installed until the rules are in place.
The state’s new Required Agricultural Practices regulating farms aren't in effect yet. Lake Champlain Committee staff scientist Mike Winslow says farmers are installing an increasing number of tile drainage systems, especially in Franklin County, and no permitting or mapping is required.
“We know that there’s a lot of phosphorus coming out of tile drains and that it’s in a form that’s really available to for algae growth,” Winslow said. “So we’re concerned about it as a source of pollution that is currently not regulated by the required agricultural practices.”
Winslow says there should be a moratorium on new tile drainage systems until more is known about potential nutrient loss.
But farmers say the tile drainage systems may actually help prevent runoff by keeping soil drier.
“When you get your next rainfall you have soil that’s ready to absorb that rain instead of the water running off into an open ditch,” said Paul Bourbeau, president of the Franklin County Farm Bureau. “For decades we were told the only way that phosphorus ended up in the lake was by soil runoff.”
Bourbeau says a moratorium on tile drainage would put Vermont farmers at a disadvantage.
While the systems are expensive to install, they can help increase crop yield and quality. And some research says they might reduce surface run off and soil erosion. Eric Young, research agronomist at the Miner Institute in Chazy, New York, says the systems help the soil hold on to phosphorus.
But he says under certain conditions tile drains can lose nutrients.
“When you get cracks in the clay soil you can have cracks that run all the way down to the tiles drains, and you can imagine if you were to apply fertilizer and manure under those conditions and then you get a big rainfall event, it doesn’t take a rocket scientist to understand that some of that stuff can get flushed down into the tile drain,” he said.
Young says more needs to be known about how phosphorus loss from tiled fields compares to fields that don’t use sub-surface drainage.
“Everyone wants to say tiles drains are bad or good type of thing for water quality but unfortunately it’s way too much of a simplification to say that because we’re finding that each field or set of fields in a particular location they act accordingly, their behavior depends on the landscape and the soil type and the slope as well as the management, how much manure it’s had over the years, how much it’s had in corn,” he said.
Young says the vast majority of phosphorus loss comes from soil erosion, not tile drains.
Later this month, the Agriculture Agency and the Agency of Natural Resources will submit an interim report on tile drainage to the legislature.