SE Minnesota groundwater at higher risk
The dangers of nitrates from fertilizers leaching into groundwater was one of the topics of a workshop dealing with current issues facing feedlot operators in Blooming Prairie last week. The session was sponsored by the feedlot officers of Dodge, Freeborn, Goodhue, Mower, Rice and Steele counties and attended by several dozen area feedlot operators.
The Minnesota Department of Agriculture has recently approved a Nitrogen Fertilizer Management Plan which outlines how the department will address elevated levels of nitrates in groundwater as a result of the use of nitrogen fertilizer, said Dawn Bernau of the agriculture department. She said the department is now working on a proposed rule that will apply in areas of the state with vulnerable groundwater.
The vulnerability of groundwater to elevated nitrogen levels varies throughout the state but the aquifers in southeastern Minnesota are considered to be at a higher risk, she said. There is less risk of contamination in the south central region.
Nitrates can leach into the groundwater from a variety of sources. While nitrate occurs naturally, it can also come from man-made sources such as human waste, animal manure and commercial fertilizers.
Nitrate is one of the most common contaminates in Minnesota’s groundwater, she said. The vast majority of households in the state have access to safe drinking water, the MDA has determined, however in some areas private and public wells may have high nitrate levels.
At high levels nitrates can cause human health problems which are most severe for infants and pregnant women.
Nitrate levels vary greatly throughout Minnesota depending on the soil type and geology of the area. Southeastern Minnesota are vulnerable to nitrate because of shallow fractured bedrock while south center Minnesota has a higher vulnerability because of widespread sandy soil.
There are three major parts to the nitrogen fertilizer management plan, Bernau said.
The first, she said, is prevention because once a problem occurs it is much harder and more expensive to address. The department, she said, has developed best management practices (BMP) and will work with the agriculture community to explore the use of cover crops, forage crops and other land management alternative on sensitive areas.
The second step, she said, is monitoring and prioritizing the situation. The department plans on testing private drinking water wells on the township level to identify areas with nitrate concerns. Current plans, she said, are to test about 70,000 wells in 230 to 280 townships over the next six years. The agriculture department will also work with the Department of Health to identify municipal wells that might have high nitrate levels.
From there, she said, the department will move on to mitigation of any problems.
The proposed rule, Bernau said, will restrict the fall and winter application of nitrogen fertilizer in areas that are vulnerable to groundwater contamination. The restriction will vary depending on the region and soil type and will be based on best management practices established by the University of Minnesota.
As long as the farmer is using the best management practices, she said, no additional regulatory measures will be taken.
The rule making process, she said, will take two to three years so the potential rule will not go into effect until 2018.