Agri News, MN
11-21-06
Small box has big role to play in corn field
By Jean Caspers-Simmet
Agri News staff writer
DOUGHERTY, Iowa -- A small box protruding above the ground at the edge of
Ted Pitzenberger's corn field is one way the Dougherty farmer is cutting nitrates
going into Coldwater Creek.
Pitzenberger recently agreed to install an experimental biofilter on his farm. It
works like this: A water control structure diverts tile water from 50 acres of his
crop ground sending it through a 5-foot by 40-foot by 6-foot deep trench filled
with wood chips that filter nitrates out of the tile water. Once the water moves
through the wood chip-lined trench, it flows back into the tile line and outlets into
the creek.
"We're forcing a portion of the drain flow through the wood chips which are a
great carbon source," said Matt Helmers, Iowa State University ag engineer
and drainage specialist. "Research has shown nitrate concentration can be
reduced 50 to 70 percent."
To make sure the biofilter won't harm Pitzenberger's field drainage in the event of
a heavy rain, there's an overflow outlet tile.
Pitzenberger is secretary of the Coldwater/Palmer Watershed Council, which
formed last winter.
"Our survey of farmers in the watershed indicated only 5 percent were interested
in constructing wetlands to remove nitrates from tile water," said John Rodecap,
Iowa State University Extension watershed coordinator based in Fayette. "Ted
volunteered to put in a biofilter as an alternative."
The Coldwater/Palmer Watershed Council will work with Coe College and the
Cedar River Watershed Monitoring Coalition to analyze the water before, during
and after it leaves the biofilter. A study will determine how long the wood chips
remain effective, and Pitzenberger will measure yield.
"Hopefully, we'll gain information on how to reduce nitrates going into the creek,"
said Pitzenberger, who raises corn and soybeans and feeds hogs with his wife,
Judy, and their sons Phil and Ian. "Our goal is to cut nitrates in half."
The biofilter is on a buffer strip between Pitzenberger's corn field and the creek.
The wood chip trench was covered with geofabric and a foot of soil and will be
seeded down.
"Nobody will even know it's here," Pitzenberger said.
A second biofilter was installed on Kenneth Pint's farm west of Independence.
Pint is a member of the Lime Creek Watershed Council.