RURAL CLARKFIELD - Modern agriculture needs nitrate fertilizers, which create problems with nitrates running off fields into receiving streams. Doug Albin, director of the Minnesota Corn Research and Promotion Council, is running a long-term experiment on his farm near Clarkfield to reduce nitrate runoff and enhance the fertility of his land in the Conservations Reserve Program.
A year ago, Albin installed a wood chip biofilter and a saturation buffer between the edge of his field and the Yellow Medicine River. Last week, two scientists from the University of Minnesota Department of Soil, Water and Climate came down to spend six days running extensive tests on the biofilter system.
"I knew I wanted to drain this field, and I wanted to design a system that was as current and environmentally friendly as possible," Albin said.
Photo by Steve Browne
Clarkfield Doug Albin, director of the Minnesota Corn Research and Promotion Council, is working with Andry Ranaivoson, right, and Ed Dorsey from the University of Minnesota Department of Soil, Water and Climate to evaluate the effectiveness of the wood chip biofilter Albin installed on his farm near Clarkfield a year ago. The biofilter is designed to reduce the amount of nitrates from fertilizer in the runoff from the field.
The biofilter is a trench measuring 10-by-60 feet, lined and filled with a mixture of hardwood and softwood chips.
The tile lines of 25 acres drain into one end and flow through the chips, which facilitates the growth of bacteria that consume the nitrate in the runoff, converting it to atmospheric nitrogen.
The saturation buffer is simply a tile line from 12 acres of the field dead-ending in a strip of CRP land. It is thought the nitrated water runoff will soak into the soil replenishing the fertility.
"Last year, we had the biofilter and saturation buffer installed," said Andry Ranaivoson, research associate with the U of M. "Now we're running a week-long evaluation. At this point, we'll have to see if there's significant denitrification, but we'll definitely continue the experiment."
What Ranaivoson and instrument specialist Ed Dorsey are doing is pumping river water through the filter, now that the tiles are not running, and taking samples at the intake and outflow. The U of M is monitoring five biofilters across the state.
Results from other parts of the Midwest are promising, and there are biofilters in Iowa whose wood chips appear good as new after nine years, Ranaivoson said.
Albin and the team are working to find ways to make biofilters more efficient, find out the optimum size ratio of biofilter to acreage of field and whether they need to have water flowing through them when the tiles aren't running.
"This project is specifically to find out about mercury," Ranaivoson said, "because at some point the filed will dry out, the water in the biofilter will become stagnant and shift from denitrification to sulphate reduction. There's a possibility of mercury methylation, which is a dangerous situation."
The solar-powered monitoring station over the bioreactor records rainfall, temperature and flow through the system.
"This is a Conservation Innovation Grant," Albin said. "It helps me adjust what's happening down here."
The biofilter cost about $13,000 to build, of which $10,000 was covered by federal grant money channeled through the state clean water Legacy fund.
Albin conceived of the project and carried it out in cooperation with the state Department of Agriculture, the Minnesota Agriculture and Water Resource Center, the state Department of Natural Resources, the Yellow Medicine County Soil and Water Conservation District, the University of Minnesota and Clean Up the River Environment, which recently gave him the River Keeper Award.
"Between the biofilter and the saturation buffer, we're trying to find out which works best under certain conditions," Albin said. "The next question is what happens if we tie them together? The preliminary indications look promising, but I'd really like to see what five to 10 years will tell."