Healthy Lawns and Healthy Lakes
Runoff containing the nutrient phosphorus from fertilizer use is a big contributor to algal blooms and the resulting oxygen depletion in many lakes, rivers and streams. As a result, some states and communities have passed restrictions on the use of phosphorus-containing fertilizers. Minnesota, for example, now restricts their use on turf (but not agricultural or general garden use), with exceptions for soils that are shown to be deficient with a soil test, for the first year turf is being established and certain golf course uses.
Recently, scientists at the University of Minnesota conducted research on the impact phosphorus fertilization of home lawns has on water quality and turf quality. They confirmed that applying phosphorus to turf when a soil test shows there is no deficiency has no benefit to an established lawn. They did determine that there is a benefit to applying a phosphorus-containing fertilizer according to State Extension Service recommendations the first year following seeding or sodding and that, as long as recommended amounts weren't exceeded, water quality wasn't affected. They also found that, even if soil deficiency warranted applying phosphorus, late fall applications were of no benefit and were much more likely to run off into waterways.
One important finding from this research published in the Journal of Environmental Quality in 2010 was that, even if no phosphorus fertilizer was applied, the amount of phosphorus in the runoff increased as the vigor and quality of the grass declined. So keeping your lawn dense and healthy with appropriate lawn care practices helps not only your yard, but the environment as well.