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Drainage offers great benefits, raises some issues Tuesday, December 19, 2006
Agri News staff writer
BLOOMINGTON, Minn. -- Drainage has been a key to populating the upper Midwest, but it's also brought problems.
Gary Sands of the University of Minnesota's Bioproducts and Biosystems Engineering Department said drainage has raised several concerns, although it's also had benefits.
"We've lost wetlands on our landscape," Sands said, noting that drainage has contributed to the decrease in landscape diversity.
Sands spoke about drainage during a session titled "What's Going Down the Drain?" at the 70th annual meeting of the Minnesota Association of Soil and Water Conservation Districts.
Sands said field tiling has increased the loss of applied nitrogen on fields and added it to the water supply.
Nitrogen is soluble, so it runs off fields and into the water supply, eventually entering the Mississippi River and traveling to the Gulf of Mexico, Sands said. It's there that nitrogen causes a situation named the Gulf Hypoxia Zone, which suffers from a loss of oxygen because of the nitrogen entering the gulf.
Nitrogen goes to the floor of the gulf and causes living things dwelling on the gulf floor to die, Sands said.
"The effects go up and down the food chain," he said.
One of the solutions, Sands said, is to bring environmental goals into water management goals.
"When it's in the wrong place, it does more harm than good," Sands said of nitrogen.
An engineering approach to tiling is a drainage water management system, which retains water in times when chemicals have been applied and crops are in the ground, but releases water at other times or bioreactor drainage design.
Sands said the systems have structures to manipulate and control output levels from fields, allowing producers to keep water in the soil profile at particular times of year.
One challenge is that hilly land significantly increases the cost of the system, so land with no to 0.5 percent slope is ideal, Sands said. About 33 percent of the Minnesota River Basin has a slope of 0 to 2 percent, but the Red River Valley has potential.
Bioreactors have wood chips or other matter buried around the field's drainage and grabs the nitrogen out of the water before it leaves the field and enters the ditch, Sands said. Research shows the wood chips have a life span of about 15 years in the system.
"Some of our most productive soils are those drained artificially," he said. |
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