In order to improve soil fertility and achieve high crop yields, natural and artificial fertilizers containing plant nutrients–primarily nitrogen, phosphorus, and potassium–are applied to farm fields. Management of soil fertility is an ancient and desirable farming practice, but plant food doesn't all stay on the fields; it finds its way into lakes, streams, and aquifers. These chemicals can lead to ecological imbalances such as excessive algae growth and low oxygen levels, can kill aquatic life, and can make drinking water unsafe.
Phosphorus levels are too high in 433 Minnesota lakes and 48 river stretches, and nitrate levels often exceed safe levels in wells located below sandy or shallow soils above fractured bedrock. In some rivers and streams nitrate levels are high enough to harm fish.
The Minnesota Nutrient Reduction Strategy (NRS), administered by the Minnesota Pollution Control Agency (MPCA), seeks to reduce nutrient pollution in waters within Minnesota, Lake Winnipeg, the Gulf of Mexico, and Lake Superior. The latest NRS report, dated 2018, notes that Minnesota phosphorus concentrations are down, but nitrogen levels are up. A detailed plan for the first phase of the NRS is here.
MPCA also regulates concentrated animal feeding operations, aka feedlots. An environmental assessment and permit is required for a feedlot with 1,000 or more animals. You can read more about the agency’s proposed changes to feedlot permits here.
The public is invited to comment on current draft feedlot permits until September 3rd at this webpage.