A study on the effects of varying nitrogen levels on corn yields has been under way in the St. Peter, MN, watershed since 1997.

The St. Peter Wellhead Project was started because of concerns about nitrate levels in the city's water supply.

“The nitrate levels in two of our shallow wells are approaching the 10 ppm level,” says Pete Moulton, St. Peter's water and wastewater superintendent. “This is an early indicator that there is a surface influence in our agricultural area that we need to evaluate. Presently, we are blending water from these two shallow wells with water from deeper wells so that the nitrate level is at a safe consumption level.”

Replicated nitrogen rates ranging from 0 to 150 lbs/acre are applied at six farm sites in the watershed.

“Replicated studies help us look at the interaction between the rate of nitrogen applied and the resulting yield,” notes Maggie Jones, owner of Blue Earth Agronomics and senior consultant with the Center for Agricultural Partnerships.

Results from the project won't clean up the water in the two wells tomorrow, but will offer some statistical data on nitrogen use and corn production.

“The St. Peter Wellhead Project looks at the actual worth of nitrogen application,” says Moulton. “At what point do lower rates of nitrogen result in lower yields? Where does profitability fit into that picture? Can slightly lower yields result in similar or greater profits? Those are the questions farmers need answers to.”

The Minnesota Pollution Control Agency, University of Minnesota Extension Service, Blue Earth Agronomics and several other agencies and groups are involved in the project.