Agricultural residues may be the newest tool in protecting drainage water quality.
Bioreactors or biofilters, use organic materials such as wood chips or crop residues like straw or corn stover to provide an environment that supports the growth of microbes. Subsurface farm drainage water flows through these bioreactors. The microbes consume nitrates in the water, reducing them to nitrogen gas and denitrifying the water.
Bioreactors are becoming more common in agricultural drainage systems. Currently, the cost of bioreactors is driven by the cost of wood chips, which is the most common filter media. But a new AURI project will look at the effectiveness of agricultural residues compared to wood. The project, supported by the Minnesota Corn Growers, will test the effectiveness of bioreactors using agricultural residues. Research will be conducted at the USDA Agricultural Research Service lab in St. Paul.
Not only does the research offer potential for extended uses of agricultural products, it also addresses the water quality issue of nitrates coming from drained agricultural lands. Benefits of using agricultural residue-based materials in denitrifying bioreactors include additional uses for crop residues such as corn stover or wheat and barley straw, increased bioreactor efficiency which would improve drainage water quality, plus it potentially increases the number of acres that can be treated by a given reactor.
“It addresses several issues for producers who are using biofilters,” says Alan Doering, AURI scientist. “It allows them to utilize ag fibers that they are producing on their farm in bioreactors, increasing value of a coproduct they produce. Since the cost of the wood fibers is one of the largest expenses, using locally available media would help them avoid those costs.”
The estimated 15-month project will get underway this fall.