Excerpt taken from MDA Nitrogen Application Fact Sheet:
There are a number of reasons why the rule focuses on agricultural areas and not urban areas. First, only a small percentage of the nitrogen fertilizer sold in Minnesota is applied to lawns, golf courses and parks. The MDA estimates that 94 – 95% of the nitrogen sold is applied to agricultural crops. The rate of nitrogen application to lawns is only 25% of the rates normally used on corn and other high nitrogen using crops. Second, the fact that nitrate leaching from fertilizer applied to lawns can range from low to very low. Lawns are perennial and have a dense root structure, so nitrate leaching losses are very similar to agricultural perennial crops and native prairie. Third, most of the concerns related to lawns are related to phosphorus rather than nitrogen. Unneeded phosphorus inputs were drastically reduced (80 – 85%) when the MN Phosphorus Lawn Fertilizer Law was passed in 2005. As part of that law, it is illegal to apply any fertilizer on impervious surfaces. The Phosphorus Lawn Fertilizer Law greatly reduces the risk of nitrogen entering storm water and other surface water bodies.
For more information visit this site from the MDA.