"While further refinements in fertilizer rates and application timing can be expected to reduce nitrate loads by roughly 13 percent statewide, additional and more costly practices will also be needed to make further reductions and meet downstream needs," the study said. "Statewide reductions over 30 percent are not realistic with current practices."
The MPCA used monitoring results from more than 50,000 stream samples from across Minnesota. It found low nitrate levels in the north, higher in the southern part of the state, and high to very high in south-central Minnesota. The agency also worked with University of Minnesota researchers to examine the pathways by which nitrates get into surface waters.
To address the problem, Minnesota state agencies are working on a strategy for reducing the state's contribution to the "dead zone." Minnesota contributes the country's sixth-highest nitrate load to the gulf, the report said.
The U.S. Department of Agriculture earlier this month announced a voluntary pilot project for four small Minnesota watersheds that will offer farmers incentives to reduce water pollution from their operations in exchange for protection from tighter future regulations. Controlling water pollution from agriculture has been a political and technical challenge. Because agriculture is exempt from the federal Clean Water Act, officials have emphasized voluntary measures so far.
MPCA Nitrogen in Surface Waters report: http://www.pca.state.mn.us/6fwc9hw