Pollutants

Agricultural Runoff

Water flowing off cropland, feedlots, and pastures that carries fertilizer, manure, pesticides, and eroded soil into lakes and streams.

What It Means for Your Lake

Agricultural runoff is the dominant source of nutrient pollution to lakes in the agricultural regions of Minnesota and Wisconsin, responsible for the majority of phosphorus loading to impaired waters in the Minnesota River basin, central Wisconsin, and the southwestern prairie regions of both states. Cropland agriculture contributes nutrients through several pathways: surface runoff carries dissolved phosphorus from recently applied fertilizer and manure, along with particulate phosphorus bound to eroded soil particles; subsurface tile drainage delivers dissolved phosphorus and nitrate directly to ditches and streams; and wind erosion deposits nutrient-rich dust on downwind water bodies. Livestock operations add nutrients through manure application to fields, feedlot runoff, and pasture grazing along streams and shorelines. The scale of agricultural nutrient loading is immense, the Minnesota Pollution Control Agency estimates that agriculture contributes approximately 75% of the phosphorus entering the Minnesota River, which carries more sediment and nutrients than any other tributary of the Upper Mississippi. The impact on downstream lakes is profound: many lakes in agricultural watersheds are eutrophic or hypereutrophic with persistent algal blooms and impaired recreational use. Conservation practices that reduce agricultural runoff include cover crops (which protect soil from erosion during fall and spring), no-till or reduced tillage (which minimizes soil disturbance), buffer strips and filter strips along waterways, grassed waterways that channel and slow runoff, nutrient management planning (matching fertilizer application to crop needs based on soil testing), and wetland restoration (which captures and processes nutrient-laden runoff before it reaches lakes). Federal programs through the Natural Resources Conservation Service (NRCS) and state programs provide cost-share payments and technical assistance to farmers who implement these practices.

Frequently Asked Questions