A study by the Minnesota Pollution Control Agency concluded that farmland is the source for 70 percent of the damaging nitrates in state surface waters. The MPCA wants farmers to adjust the fertilizer they use to reduce those levels.
MPR reports that making those changes will help farmers save money as well as the planet.
Fertilizer runoff in Minnesota and other Midwest states is a major cause of the "dead zone", a biological void where the Mississippi River reaches the Gulf of Mexico. Nitrate promotes algae growth and algae depletes the oxygen marine life need as it decomposes. High levels also harm the food chain for fish in Minnesota waters.
Scientists at the University of Minnesota's Southern Research and Outreach Center in Waseca have calculated the smallest dose of fertilizer needed. The PCA report founds more efficient fertilizer management could reduce nitrate runoff into state streams by about 13 percent.
Some farmers are adjusting their methods, cutting costs by cutting the supplemental nitrogen they use. One farmer suggested that the economic advantage provides the most powerful motivation to change.